Droplet sensors for fuel systems

A droplet detection system includes a sensing channel, such as a microfluidic channel, configured to receive a flow of fluid that may contain one or more liquid droplets dispersed in the fluid. The cross-sectional area of the sensing channel maybe configured to allow droplets of a predetermined size to flow through the channel one at a time. A light source, a light aperture, and a light detector are positioned outside the sensing channel, which use light in a selected frequency band that has a substantially different absorbance for the liquid compared to the fluid. Liquid droplets may be detected and characterized using a signal from the light detector.

The present disclosure relates to droplet sensors. In particular, the present disclosure relates to droplet sensors configured to detect liquid droplets dispersed in a different fluid, such as water droplets dispersed in fuel.

The water in fuel may be problematic in fuel systems of internal combustion engines. Water in fuel may damage fuel injectors due to corrosion or vaporization during combustion. For example, damage to injectors may cause various problems in operation of the engine, such as failing to be able to comply with jurisdictional emission standards. Fuel injector damage may require repair or maintenance. Reduced operating time may be particularly costly for commercial or industrial vehicles.

Sensors, such as water-in-fuel (WIF) sensors, have been proposed to detect water in fuel. One type of sensor is a float system, which uses material with density between water and fuel. Another type of sensor is a conductivity sensor. Both of these types of sensors are subject to problems over time as dirt or debris collects on the surfaces. In particular, conductive WIF sensors may be susceptible to corrosion and electrochemical plating over time. In-line flow sensors on fuel systems have been proposed using light sources at near infrared wavelengths to detect water in fuel. Some systems are designed to have path lengths between the light source and detector on the order to centimeters to be suitable for detecting water. Such systems may be ineffective at distinguishing from dissolved water and water droplets, which may have different impacts on the injectors. Further, such system may provide inaccurate sizing information when multiple water droplets are present in the detector.

There is a need for improved sensors to mitigate fuel injector damage and to improve the performance of internal combustion engines over time.

SUMMARY

Various aspects of the present disclosure relate to droplet sensors configured to detect liquid in a different fluid using a sensing channel, such as detecting liquid droplets dispersed in a different fluid using a microfluidic channel. In some embodiments, the droplet detection sensors may be configured to detect water droplets dispersed in a hydrocarbon fluid, such as fuel, which may be described as a microfluidic water-in-fuel (WIF) sensor. Infrared light may be used by the droplet sensors to measure light absorbance through the microfluidic channel and determine whether or how much of a liquid droplet is present in the fluid. The droplet sensor may be configured to differentiate, or distinguish, between liquid droplets dispersed in fluid and dissolved liquid in fluid as the fluid flows through the microfluidic channel. Information from the sensor may be used to determine one or more of the concentration of liquid in the fluid, the liquid droplet size, or the liquid droplet rate of flow through the microfluidic channel. A water level may also be measured using the sensor.

In one aspect, the present disclosure relates to a system including a microfluidic channel configured to receive a flow of a first fluid and a second fluid dispersed in the first fluid. The second fluid has a different composition than the first fluid. The system also includes a light source configured to direct a light beam in a frequency band along a path through the microfluidic channel. The frequency band is selected to have a higher absorbance by the second fluid than by the first fluid. The system further includes an aperture element defining a light aperture positioned in the path of the light beam from the light source. The system further includes a light detector positioned to receive the light beam in a sensing area after passing through the microfluidic channel and the light aperture. The light detector is configured to provide a signal representing an amount of light in the frequency band that remains after passing through the microfluidic channel. The system further includes a controller operably coupled to the light detector and configured to determine whether the second fluid is in droplet form based on the signal.

In another aspect, the present disclosure relates to a system including a fuel and water separator having a housing defining a water collection volume. The water collection volume is fluidly connected to an engine fuel line and fluidly connected to a water drain outlet. The system also includes a light source configured to direct a light beam in a frequency band along a path through the water collection volume. The frequency band is selected to be absorbed by water. The system further includes a light detector positioned to receive the light beam in a sensing area after passing through at least part of the water collection volume. The light detector is configured to provide a signal representing an amount of light in the frequency band. The system further includes a controller operably coupled to the light detector and configured to determine whether water is detected based on the signal.

In yet another aspect, the present disclosure relates to a system including a microfluidic channel configured to receive a flow of hydrocarbon fluid. The microfluidic channel has a cross-sectional area sized to receive one water droplet at a time when a water droplet of a predetermined size is dispersed in the hydrocarbon fluid. The system also includes a light source positioned outside the microfluidic channel configured to generate light in a selected frequency band such that the water droplet has a higher absorbance than the hydrocarbon fluid in the selected frequency band. The system further includes a light detector sensitive to the selected frequency band positioned outside the microfluidic channel and configured to provide a signal representing an amount of light remaining after passing through the microfluidic channel. The system additionally includes a light aperture positioned between the light source and the light detector, wherein light from the light source passing through the light aperture forms a light beam defining a beam axis that extends through the light source, the microfluidic channel, and the light detector. The system still further includes a controller operably connected to the light detector and configured to detect one or more water droplets dispersed in the flow of hydrocarbon fluid based on the signal from the light detector representing the amount of light from the light source remaining after passing through the microfluidic channel and the light aperture.

In still another aspect, the present disclosure relates to a sensor including a microfluidic channel sized to receive a flow of fluid. The microfluidic channel has a cross-sectional area sized to receive one liquid droplet at a time when a liquid droplet of a predetermined size is dispersed in the fluid. The sensor also includes a light source positioned outside the microfluidic channel configured to generate light in a selected frequency band such that the droplets have a different absorbance than the different liquid in the selected frequency band. The sensor further includes a light detector sensitive to the selected frequency band positioned outside the microfluidic channel and configured to provide a signal representing an amount of light remaining after passing through the microfluidic channel. The sensor additionally includes a light aperture positioned between the light source and the light detector, wherein light from the light source passing through the light aperture forms a light beam defining a beam axis that extends through the light source, the microfluidic channel, and the light detector. A width of the light aperture and the light detector define a sensing area. The sensor still further includes a controller operably connected to the light detector and configured to determine a droplet rate through the sensing area of the microfluidic channel based on the signal from the light detector representing the amount of light from the light source remaining after passing through the microfluidic channel and the light aperture.

In a further aspect, the present disclosure relates to a water droplet sensor including a microfluidic channel defining a cross-sectional area less than 1 mm2. The sensor also includes a light source positioned outside the microfluidic channel configured to generate light in a near infrared frequency band. The sensor further includes a light detector sensitive to the selected frequency band positioned outside the microfluidic channel and configured to provide a signal representing an amount of light remaining after passing through the microfluidic channel. The sensor additionally includes a light aperture positioned between the light source and the light detector, wherein light from the light source passing through the light aperture forms a light beam defining a beam axis that extends through the light source, the microfluidic channel, and the light detector. The aperture has a width less than 1 mm. The sensor still further includes a controller operably connected to the light detector and configured to detect one or more water droplets dispersed in the flow of hydrocarbon fluid based on the signal from the light detector representing the amount of light from the light source remaining after passing through the microfluidic channel and the light aperture.

DETAILED DESCRIPTION

This disclosure relates to sensors configured to detect or characterize liquid droplets dispersed in a different fluid using one or more sensing channels, such as microfluidic channels. Although reference is made herein to water droplet sensors to protect engine fuel systems, such as water-in-fuel (WIF) sensors, the sensors and related techniques may be used to detect or characterize any liquid-in-fluid for which the absorbance of the liquid is different than the fluid, as well as various vehicular or non-vehicular applications. Non-limiting examples of other applications include detecting water-in-oil or detecting water in fuel tanks used for bulk fuel storage. A water level may also be measured using the sensor. Various other applications will become apparent to one skilled in the art having the benefit of this disclosure.

In applications related to engine fuel systems, different forms of water may have different effects on various components of the fuel system. For example, water that is not dissolved in the fuel, which may be described as free water, water droplets, or dispersed water, can cause damage to engine systems by causing rust, encouraging microbial growth, damaging fuel injectors, or causing poor ignition performance.

It may be beneficial to provide a sensor configured to precisely detect water droplets, or free water, instead of treating all forms of water equally. For example, the sensor may be substantially more sensitive to detecting water droplets, such as emulsified water in fuel, compared to dissolved water in fuel. It may be beneficial to provide sensors that may require less maintenance than existing sensors, such as float sensors or conductive WIF sensors. Further, it may be beneficial to provide a sensor that can be used to characterize the water droplets in the fuel.

The present disclosure provides droplet sensors that may be configured to use light, such as near infrared (NIR) wavelengths of light, to detect and size water droplets in a stream of hydrocarbon fluid, such as fuel or oil, using one or more microfluidic channels. The microfluidic channel may have a cross-sectional area that is a square, rectangle, circle, oval, half-circle, or any other suitable geometric shape. The microfluidic channel limits the path length of light across the channel that is used to detect water droplets in the fuel. Advantageously, the limited path length provided by the microfluidic channel may reduce the occurrence of some water droplets being hidden behind other water droplets in a sensing area of the droplet sensor, thereby facilitating a sensitivity for detecting water droplets higher than for detecting dissolved water, which may facilitate accurate and precise characterization of the droplets.

In some applications, the width or depth of the microfluidic channel may be sized comparably to water droplets of interest. For example, droplets in a range from 15 up to 300 micrometers in diameter may be detected and sized using a microfluidic channel having a width of 150 micrometers. In other words, a droplet diameter down to one-tenth the width or depth of the microfluidic channel may be detected and sized. Smaller droplets may be detected and sized using a smaller channel, such as a width of 100 micrometers, a more precise alignment, or a more sensitive electronic detector.

The absorbance of water to NIR light may be substantially different than the absorbance of fuel. For example, water may have an absorbance greater than 3, whereas hydrocarbon fluid, such as fuel, may have an absorbance of less than 0.5 for a 10-millimeter path length. In one or more embodiments, a sensor includes an NIR light source centered at approximately 1550 nanometers, a circular aperture aligned with the channel, and a light detector. In some embodiments, the sensor may contain no focusing optics, and many parts of the droplet sensors, such as the light source and light detector, do not need to physically contact the water or fuel to detect water droplets using light, which may facilitate the robust operation of the sensor electronic, for example, due to less risk for corrosion compared to a conductive WIF sensor. In some embodiments, only the microfluidic channel may contact the water or fuel. Further, the droplet sensor may be designed using low-power usage parts and without moving parts, which may facilitate fewer maintenance events and longer operational times.

As used herein, the term “light” refers to energy at one or more wavelengths in the electromagnetic spectrum. Non-limiting examples of “light” include solar energy, infrared (IR) light, visible light, or ultraviolet (UV) light. Infrared light may include wavelengths in a range from 0.75 micrometers up to 1000 micrometers.

As used herein, the term “near infrared” or “NIR” light includes wavelengths greater than or equal to 0.75 or 0.78 micrometers and less than or equal to 2.5 or 3 micrometers.

As used herein, the term “or” is generally employed in its inclusive sense, for example, to mean “and/or” unless the context clearly dictates otherwise. The term “and/or” means one or all the listed elements or a combination of at least two of the listed elements.

Reference will now be made to the drawings, which depict one or more aspects described in this disclosure. However, it will be understood that other aspects not depicted in the drawings fall within the scope of this disclosure. Like numbers used in the figures refer to like components, steps and the like. However, it will be understood that the use of a reference character to refer to an element in a given figure is not intended to limit the element in another figure labeled with the same reference character. In addition, the use of different reference characters to refer to elements in different figures is not intended to indicate that the differently referenced elements cannot be the same or similar.

FIG.1shows system100with droplet sensor102that is configured to detect liquid dispersed in a different fluid. In the illustrated embodiment, system100is an engine system including engine120, fuel system130, and computer122. Engine120may be an internal combustion engine. Droplet sensor102may be configured to detect water droplets in fluid. The fluid may be hydrocarbon fluid, such as a fuel or oil. In the illustrated embodiment, the fluid is fuel112. Non-limiting examples of fuel112include gasoline and diesel. Fuel112is stored and provided to engine120by fuel system130. System100may be used on a vehicle for on-road or off-road applications, such as trucking or mining. In such applications, computer122may be a vehicle computer, such as an engine control module (ECM) or other on-board computer.

As illustrated, fuel system130includes droplet sensor102, fuel tank108, fuel pump110, fuel line114, fuel filter116, and injection system118. Fuel tank108is in fluid communication with fuel pump110, fuel line114, and injection system118. Fuel112is stored in fuel tank108and pumped by fuel pump110when system100is in operation combusting fuel112in engine120. Fuel pump110is configured to provide a flow of fuel112, or fuel flow, to one or more fuel injectors of injection system118. Fuel line114is configured to deliver fluid to injection system118. Fuel112enters fuel line114at fuel pump110and exists fuel line114at injection system118. Injection system118may include a pressurized fuel rail and one or more fuel injectors. Injection system118is configured to provide a pressurized spray of fuel112into one or more combustion cylinders of engine120.

Fuel filter116is positioned, or disposed, along fuel line114. Fuel112may contain water. Fuel filter116is configured to remove water from fuel112. Fuel filter116may be a fuel-water separator (FWS), for example, as used in some on-vehicle diesel engine systems. Water in fuel112may cause damage to various components of system100. For example, water may cause damage to one or more injectors of injection system118. In particular, water droplets in fuel112may cause damage to one or more injectors of injection system118when vaporized in the combustion cylinder. Dissolved water in fuel112may not cause similar damage.

Droplet sensor102may be positioned, or disposed, along fuel line114to detect water in fuel112. Droplet sensor102may be configured to be more sensitive to detecting water droplets in fuel112than dissolved water in fuel112to provide reliable indication of potential damage to any injectors of injection system118.

Droplet sensor102includes one or more detection assemblies104. Each detection assembly104may be configured to receive a flow of fuel112for measuring water droplets. Fuel112from fuel line114may flow through each detection assembly104. Fuel112may be returned to fuel line114after measurement. Fuel112may enter each using the flow of fuel112through fuel line114provided by fuel pump110. In other words, fuel112may enter some or all detection assemblies104passively.

In some embodiments, droplet sensor102may include one or more separate pumps (not shown), different than fuel pump110, to actively provide a flow of fuel112from fuel line114to some or all detection assemblies104. The separate pumps, or sampling pumps, may be positioned downstream of any sensing channel or microfluidic channel so that the pump does not affect measurement of droplets. For example, a pump may have the effect of “chopping up” some water droplets.

As used herein, the term “downstream” refers to a direction along fuel line114toward fuel pump110. The term “upstream” refers to the opposite of downstream, or a direction along fuel line114toward injection system118.

In the illustrated embodiment, fuel pump110is positioned upstream of fuel filter116. In other embodiments (not shown), fuel filter116is positioned upstream of fuel pump110. In some embodiments (not shown), system100includes two or more fuel filters116. For example, one fuel filter116may be positioned upstream and one fuel filter116may be positioned downstream of fuel pump110. Each fuel filter116may be the same or different. In some embodiments, water may be removed from fuel at the upstream fuel filter116, the downstream fuel filter116, or both.

Each detection assembly104may include a microfluidic channel configured to receive a flow of fuel112from fuel line114. Each microfluidic channel may be positioned adjacent or proximate to a main flow of fuel112along fuel line114. In some embodiments, some or all microfluidic channels of detection assembly104are in parallel fluid communication with fuel line114. In some embodiments, some or all microfluidic channels of detection assembly104are disposed in the main flow of fuel line114, such that some of or all the main flow is directed through one or more microfluidic channels.

Depending on the application, droplet sensor102may be positioned at one or more locations along fuel line114, such as upstream, downstream, or at the location of fuel filter116. In some embodiments (not shown), droplet sensor102is located on a fuel return line (not shown) in fluid communication between injection system118and fuel tank108. In some embodiments (not shown), droplet sensor102may be built into, or integrated with, one or more injectors of injection system118. In other words, the droplet sensor102may be directly integrated into the fuel injector or the injection system118.

In one embodiment, droplet sensor102includes one detection assembly104. The one detection assembly104may be positioned downstream of fuel filter116. Alternatively, the one detection assembly104may be positioned at fuel filter116or upstream of fuel filter116. In some embodiments, droplet sensor102includes a combination of detection assemblies104positioned at one or more locations selected from upstream, downstream, or at the location of fuel filter116. One or more detection assemblies104may be positioned at the same location along fuel line114.

Positioning detection assembly104downstream of, or at, fuel filter116may be used to provide information used to determine the quality of water-fuel separation by fuel filter116, which may be used to indicate that fuel filter116is operating correctly or may need maintenance or replacement. Positioning detection assembly104upstream of, or at, fuel filter116may be used to provide information used to determine the quality of fuel112stored in fuel tank108or being provided along fuel line114, which may be used to indicate that fuel tank108is operating correctly or may need maintenance or replacement or that fuel112provided to fuel tank108.

As fuel112approaches injection system118, fuel112may reach a high temperature, for example, due to the proximity to injection system118or engine120. In some embodiments, detection assembly104may be positioned upstream from injection system118a sufficient distance to prevent the high temperature of some injection systems from substantially impacting the performance of certain droplet sensors102.

Droplet sensor102may include sensor controller106. Sensor controller106may be operably connected, or coupled, to one or more detection assemblies104. Each detection assembly104may make measurements and provide information characterizing water droplets detected in fuel112to sensor controller106. Information may be provided in the form of a signal, such as an electrical signal. Examples of electrical signals include a current signal, voltage signal, and power signal. Information from detection assemblies104may be used by sensor controller106to determine various characteristics corresponding to the water droplets in fuel112, such as droplet size, droplet rate, or the amount of water in fuel112(for example, a concentration).

Sensor controller106may be operably connected to computer122. Computer122may be used to control various aspects of fuel system130, such as flow rate of fuel112or injection timing for injection system118. Sensor controller106and computer122are part of a control system of system100and may be separate components. In some embodiments, the functionality of sensor controller106and computer122may be integrated into a single component, such as a single controller or computer.

Droplet sensor102may be configured to detect a predetermined size of liquid droplet, or droplet size. As used herein, “droplet size” may be described interchangeably using a volume or using a spherical diameter corresponding to the volume of a liquid droplet when shaped as a sphere. In other words, the volume of a liquid droplet of any shape may be described by a spherical diameter of the same droplet when re-shaped into a sphere. In this manner, droplet size may be described as a volume corresponding to a specified spherical diameter.

In some embodiments, droplet sensor102is configured to detect or characterize a droplet size greater than or equal to 5, 10, 15, 50, 100, 150, 250, 300, or 1000 micrometers. In some embodiments, droplet sensor102is configured to detect or characterize a droplet size less than or equal to 5000, 1000, 300, 250, 150, or 100 micrometers. In some embodiments, droplet sensor102is configured to detect or characterize a droplet size in a range from 5 up to 5000 micrometers. In one or more embodiments, droplet sensor102is configured to detect or characterize a droplet size in a range from 10 to 300 micrometers.

In fuel system applications, droplet sizes less than 10 micrometers may not be considered liquid droplets that negatively impact the operation of injection system118of system100. In particular, such water droplet sizes may be considered unstable below 10 micrometers and may not substantially contribute to damaging fuel injectors. Further, water in fuel that passes through typical fuel pumps110tend to form droplets of at least about 10 micrometers.

In general, one or more of the components, such as controllers, sensors, detectors, or computers, described herein may include a processor, such as a central processing unit (CPU), computer, logic array, or other device capable of directing data coming into or out of the sensor. The controller may include one or more computing devices having memory (which may include storage drives), processing, and communication hardware. The controller may include circuitry used to couple various components of the controller together or with other components operably coupled to the controller. The functions of the controller may be performed by hardware and/or as computer instructions on a non-transient computer readable storage medium.

The processor of the controller may include any one or more of a microprocessor, a microcontroller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), and/or equivalent discrete or integrated logic circuitry. In some examples, the processor may include multiple components, such as any combination of one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, and/or one or more FPGAs, as well as other discrete or integrated logic circuitry. The functions attributed to the controller or processor herein may be embodied as software, firmware, hardware, or any combination thereof. While described herein as a processor-based system, an alternative controller could utilize other components such as relays and timers to achieve the desired results, either alone or in combination with a microprocessor-based system.

In one or more embodiments, the exemplary systems, methods, and interfaces may be implemented using one or more computer programs using a computing apparatus, which may include one or more processors and/or memory. Program code and/or logic described herein may be applied to input data/information to perform functionality described herein and generate desired output data/information. The output data/information may be applied as an input to one or more other devices and/or methods as described herein or as would be applied in a known fashion. In view of the above, it will be readily apparent that the controller functionality as described herein may be implemented in any manner known to one skilled in the art.

FIG.2shows various components of droplet sensor102including detection assembly104and sensor controller106that may be used with system100ofFIG.1. In the illustrated embodiment, detection assembly104includes microfluidic channel200, light source202, light aperture204, and light detector206. Sensor controller106is operably connected to light detector206and may also be operably connected to light source202.

Microfluidic channel200is configured to receive a flow of fluid208. Microfluidic channel200may include an inlet to receive the flow of fluid208and an outlet to discharge the flow of fluid208. The droplet sensor102may be configured to detect and characterize liquid droplets210in the flow of fluid208may also flow through microfluidic channel200in a forward direction toward the outlet or even in reverse direction toward the inlet.

Liquid droplets210may be dispersed in fluid208in microfluidic channel200. For example, liquid droplets210may be suspended in fluid208in a separate phase. In other words, liquid droplets210are not dissolved in fluid208.

In general, microfluidic channel200is sized to receive one or more liquid droplets210at a time. In some embodiments, microfluidic channel200has a cross-sectional area sized to receive one liquid droplet210of a predetermined size at a time. In particular, the cross-sectional area of microfluidic channel200may be about the same size as a cross-sectional area of liquid droplet210, which may facilitate counting one liquid droplet210at a time to facilitate accurate counting and sizing of liquid droplet210.

The cross-sectional area may be defined orthogonal to the direction of the flow of fluid208. In other words, the cross-sectional area may be described as transverse to a longitudinal flow of fluid208. In some embodiments, microfluidic channel200has a cross-sectional area less than or equal to 1, 0.5, 0.2, 0.1, 0.05, 0.04, 0.03, or 0.02 mm2. In some embodiments, microfluidic channel200has a cross-sectional area greater than or equal to 0.01, 0.02, 0.03, 0.04, 0.05, 0.1, 0.2, or 0.5 mm2. For example, the cross-sectional area of a 150×150-micrometer microfluidic channel200would be 0.0225 mm2.

Cross-sectional area may be defined as a channel depth multiplied by a channel width. Both channel depth and channel width may be orthogonal to the direction of the flow of fluid208. In some embodiments, the channel depth is less than or equal to the channel width. Using a shallow channel depth may prevent liquid droplets210from stacking, or hiding behind one another, as the liquid droplets flow through microfluidic channel200.

In some embodiments, the channel width is less than or equal to 5000, 2000, 1000, 500, 300, 250, 200, 150, or 100 micrometers. In some embodiments, the channel width is greater than or equal to 50, 100, 150, 200, 250, 300, 500, 1000, or 2500 micrometers. In one or more embodiments, the channel width is 150 micrometers. In one or more embodiments, the channel width is 250 micrometers.

In some embodiments, the channel depth is less than or equal to 750, 500, 300, 250, 200, 150, 120, or 100 micrometers. In some embodiments, the channel depth is greater than or equal to 50, 100, 120, 150, 200, 250, 300, or 500 micrometers. In one or more embodiments, the channel depth is less than or equal to 150 micrometers. In one or more embodiments, the channel depth is less than or equal to 250 micrometers.

In the illustrated embodiment, light source202is positioned outside microfluidic channel200. Light aperture204is positioned between light source202and light detector206. In some embodiments, light aperture204is positioned before microfluidic channel200, for example, between light source202and microfluidic channel200. In some embodiments, light aperture204is positioned after microfluidic channel200, for example, between microfluidic channel200and light detector206.

Light source202is configured to direct light212through light aperture204to form light beam214. Light beam214is directed to pass through microfluidic channel200. Light beam214may be collimated or substantially collimated by light aperture204, at least for the path length of light beam214through microfluidic channel200. Light beam214may define a beam axis extending through the microfluidic channel200. The walls of microfluidic channel200may be formed of a light transparent material, at least to light212provided by light source202. The path of light beam214intersecting with microfluidic channel200defines sensing area216, which may also be described as a sensing volume, in which liquid droplets210may be detected. After light beam214passes through microfluidic channel200, light beam214is received by light detector206, which is positioned outside of microfluidic channel200in the illustrated embodiment. When liquid droplet210and fluid208are in sensing area216, light detector206may be used to determine an absorbance of light beam214by liquid droplet210and fluid208to detect, size, or otherwise characterize liquid droplet210.

As used herein, the term “path length” refers to the distance that light from light source202travels in fluid to be measured. In some embodiments, the path length may be equal to a width or depth of microfluidic channel200. The path length may be small to improve sensitivity to liquid droplets210. In some embodiments, the path length is less than or equal to 2000, 1000, 500, 300, 250, 200, 150, or 100 micrometers. In one or more embodiments, the path length is less than or equal to 1000 micrometers.

Light source202is configured to generate light in a selected frequency band such that liquid droplet210has a different absorbance than fluid208in the selected frequency band. In one or more embodiments, liquid droplet210has a higher absorbance than fluid208when the liquid is water and fluid208is a hydrocarbon fluid. In fuel system applications, for example, light source202may generate light212in at least the NIR frequency band. In some embodiments, NIR light212may include an emission peak in, or at least include frequencies in, a range from 1400 to 1600 nanometers. In particular, NIR light212may include an emission peak centered at or near 1550 nanometers. In some embodiments, NIR light212may include an emission peak in, or at least include frequencies in, a range from least 900 to 1100 nanometers. In particular, NIR light212may include an emission peak centered at or near 1000 nanometers.

Light source202may include any suitable type of light source capable of providing light212in a selected frequency band. In some embodiments, light source202is a light-emitting diode (LED). The LED light source202may be a low-power LED. In some embodiments, the LED light source emit omnidirectionally or in all directions from the light-emitting junction. In some embodiments, the LED light source emits primarily in one direction. In some embodiments, light source202may be paired with or include a fiber optic cable that directs light to microfluidic channel200. Light aperture204may be used to allow a narrow light beam214through microfluidic channel200, which may facilitate eliminating noise or false signals, for example, due to scattering and reflectance.

Light aperture204includes an opening in an aperture element218. As used herein, “aperture” refers to the opening, or void, within the aperture element. Light aperture204has a width that is sized relative to microfluidic channel200and light detector206to facilitate optimal sensitivity for detecting liquid droplets210in fluid208. In some embodiments, the width of light aperture204is the same or substantially the same as the channel width of microfluidic channel200.

Additionally, or alternatively, light aperture204may be sized relative to a predetermined droplet size of interest. For example, in some embodiments, the width of light aperture204may be designed to be less than or equal to 2, 3, 4, 5, 6, 7, 8, 9, or 10 times the droplet size of interest. In some embodiments, the width of light aperture204may be designed to be greater than or equal to 1, 2, 3, 4, 5, 6, 7, 8, or 9 times the droplet size of interest.

Light aperture204may have any suitable geometric shape. In some embodiments, light aperture204has a round or circular shape, such as a circle or oval. In some embodiments, light aperture204has a polygonal shape, such as a triangle, square, trapezoid, or rectangle. Light aperture204may have a length, which may extend along the same direction as the flow of fluid208. In one or more embodiments, the length of light aperture204may be the same or substantially the same as the width of light aperture204.

In some embodiments, light aperture204has a width less than or equal to 5000, 2000, 1000, 500, 300, 250, 200, 150, or 100 micrometers. In some embodiments, the width of light aperture204is greater than or equal to 50, 100, 150, 200, 250, 300, 500, 1000, or 2500 micrometers. In one or more embodiments, the width of light aperture204is 150 micrometers. In one or more embodiments, the width of light aperture204is 250 micrometers.

Light detector206may be any suitable type of photodetector sensitive to the selected frequency band, which may be an NIR frequency band. Light detector206is also configured to provide a signal representing an amount of light from light beam214remaining after passing through microfluidic channel200. In particular, light detector206may be configured to generate an electrical signal, such as a current, voltage, or power signal, in response to receiving light in the selected frequency band. Non-limiting examples of types of photodetectors include indium-gallium-arsenide (InGaAs) or germanium (Ge) photodiodes. For example, an InGaAs photodiode may be sensitive to light212in a frequency band from 1100 to 1700 nanometers. A Ge photodiode may have a peak sensitivity at 1550 nanometers.

Sensor controller106is configured to detect, size, or otherwise characterize one or more liquid droplets210dispersed in the flow of fluid208based on the signal from light detector206. In some embodiments, sensor controller106may be configured to detect one liquid droplet210at a time dispersed in the flow of fluid208, particularly liquid droplets210of a predetermined size. The signal may be used to determine an amount of liquid (e.g., water) per unit volume of fluid208(e.g., hydrocarbon fluid) excluding liquid dissolved in fluid208.

In some embodiments, sensor controller106is configured to determine a droplet rate through sensing area216. For example, a change in absorbance detected based on the signal from light detector206may indicate that liquid droplet210is entering or is leaving sensing area216. Alternatively, or additionally, sensor controller106may be configured to determine a droplet size. In some embodiments, sensor controller106may determine a droplet rate or a droplet size based on at least one of: a magnitude of a pulse contained within the signal, a width of a pulse contained within the signal, a first threshold signal level for detecting a minimum size droplet in the sensing area, a second threshold signal level for detecting a droplet that fills the sensing area, and a threshold signal level crossing rate, which are described herein in more detail with respect toFIGS.3-5. Sensor controller106may determine an amount of liquid210in droplet form per unit volume of fluid208, such as a droplet concentration, based on droplet rate, droplet size, or both. In some applications, such as non-engine applications, when a droplet rate is regular or substantially regular, the droplet rate may be used to estimate or determine a droplet size or concentration.

In fuel systems applications, sensor controller106may be configured to provide a maintenance signal in response to detecting water in fuel. For example, a maintenance signal may be provided under certain conditions, such as when detecting a droplet above a threshold size, detecting a number of droplets above a threshold size, detecting a threshold number of droplets, determining a threshold volume of water based on detected droplets, detecting a threshold rate (or frequency) of droplets, or detecting a threshold concentration of water in fuel. These conditions may also be used for other liquid droplets in fluid.

FIGS.3A-5Dshow various sizes of liquid droplets303,304,305that may be detected using a single microfluidic channel in detection assembly104ofFIG.2. In particular,FIGS.3A-Dare various illustrations showing when liquid droplet303with a large droplet size (e.g., a plug shape) greater than channel width310of microfluidic channel312flows through sensing area314.FIGS.4A-Dare various illustrations showing when liquid droplet304with a medium droplet size (e.g., a spherical shape) equal to channel width310flows through sensing area314.FIGS.5A-Dare various illustrations showing when liquid droplet305with a small droplet size (e.g., a small spherical shape) less than channel width310flows through sensing area314.

In the illustrated embodiments, channel depth316of the cross-sectional area318of microfluidic channel312is equal to channel width310. In other words, microfluidic channel312has a square shaped cross-sectional area318. Also, in the illustrated embodiments, sensing area314is in the shape of a cylinder, which may be provided by a light aperture in the shape of a circle. As described herein, various characteristics of liquid droplets303,304,305may be determined based on signals323,324,325detected, for example, in response to various liquid droplets303,304,305.

As used herein, a “plug shape” may be used to describe a liquid droplet that has been squeezed into a microfluidic channel and may have a shape similar to two spherical caps connected by a cylinder.

FIG.3Ashows a snapshot of large liquid droplet303flowing through microfluidic channel312when a center of liquid droplet303is aligned with a center of sensing area314of microfluidic channel312.FIG.3Bshows cross-sectional area318of microfluidic channel312at the center of sensing area314when liquid droplet303is positioned as shown inFIG.3A. As can be seen, when liquid droplet303is constrained in microfluidic channel312, width333of liquid droplet303is the same as channel width310and channel depth316. When liquid droplet303is not constrained by microfluidic channel312, liquid droplet303may have a spherical shape. For comparison,FIG.3Cshows a top-down view of liquid droplet303as visible in sensing area314, also, when liquid droplet303is positioned as shown inFIG.3A. As can be seen, liquid droplet303fills sensing area314as liquid droplet303flows through sensing area314.

FIG.3Dshows plot343of one example of a signal from light detector206(FIG.2). Plot343of signal323shows electrical voltage V versus time t. Signal323may be inversely related to absorbance of liquid in sensing area314. In other words, as light-absorbing liquid enters sensing area314, signal323may drop and, as light-absorbing liquid leaves sensing area314, signal323may rise. In other embodiments, signal323may be directly related (e.g., the opposite to inversely related) to absorbance of liquid in sensing area314, for example, depending on the particular type of light detector used.

Various thresholds may be used to characterize liquid droplet303. In the illustrated embodiment, before liquid droplet303enters sensing area314, signal323exceeds first threshold350. As light-absorbing liquid droplet303begins to fill sensing area314, signal323drops. After liquid droplet303completely fills sensing area314, signal323falls below second threshold352. As liquid droplet303begins to leave sensing area314, signal323rises and exceeds second threshold352. After liquid droplet303completely leaves sensing area314signal323may once again exceed first threshold350.

FIG.4Ashows a snapshot of medium liquid droplet304flowing through microfluidic channel312when a center of liquid droplet304is aligned with a center of sensing area314of microfluidic channel312.FIG.4Bshows cross-sectional area318of microfluidic channel312at the center of sensing area314when liquid droplet304is positioned as shown inFIG.4A. As can be seen, when liquid droplet304is in microfluidic channel312, width334of liquid droplet304is the same as channel width310and channel depth316. For comparison,FIG.4Cshows a top-down view of liquid droplet304as visible in sensing area314, also, when liquid droplet304is positioned as shown inFIG.4A. As can be seen, liquid droplet304fills sensing area314as liquid droplet304flows through sensing area314. In other words, both the large droplet size of liquid droplet303(FIG.3A) and the medium droplet size of liquid droplet304(FIG.4A) entirely fill sensing area314.

FIG.4Dshows plot344of signal324from light detector206(FIG.2). LikeFIG.3D, plot344of signal324shows electrical voltage V versus time t. The same thresholds350,352shown inFIG.3Dare shown here. In the illustrated embodiment, before liquid droplet304enters sensing area314, signal324exceeds first threshold350. As light-absorbing liquid droplet304begins to fill sensing area314, signal324drops. LikeFIG.3D, after liquid droplet304completely fills sensing area314, signal324falls below second threshold352. As liquid droplet304begins to leave sensing area314, signal324rises and exceeds second threshold352. After liquid droplet304completely leaves sensing area314signal324may once again exceed first threshold350. In contrast toFIG.3D, the duration between signal324falling below second threshold352and subsequently exceeding second threshold352is substantially lower. As can be seen inFIG.3D, the duration between crossings of second threshold352looks like a flat or substantially flat line, whereas signal324ofFIG.4Dlooks like a “V” or sharp valley. Further, the duration between signal324crossing first threshold350is shorter compared to signal323ofFIG.3D.

FIG.5Ashows a snapshot of small liquid droplet305flowing through microfluidic channel312when a center of liquid droplet305is aligned with a center of sensing area314of microfluidic channel312.FIG.5Bshows cross-sectional area318of microfluidic channel312at the center of sensing area314when liquid droplet305is positioned as shown inFIG.5A. As can be seen, when liquid droplet305is in microfluidic channel312, width335of liquid droplet305is less than channel width310and channel depth316. For comparison,FIG.5Cshows a top-down view of liquid droplet305as visible in sensing area314, also, when liquid droplet305is positioned as shown inFIG.5A. As can be seen, liquid droplet305does not fill sensing area314as liquid droplet305flows through sensing area314in contrast to the large droplet size of liquid droplet303(FIG.3A) and the medium droplet size of liquid droplet304(FIG.4A).

FIG.5Dshows plot345of signal325from light detector206(FIG.2). LikeFIGS.3D and4D, plot345of signal325shows electrical voltage V versus time t. The same thresholds350,352shown inFIGS.3D and4Dare shown here. In the illustrated embodiment, before liquid droplet305enters sensing area314, signal325exceeds first threshold350. As light-absorbing liquid droplet305begins to fill sensing area314, signal325drops. In contrast toFIGS.3D and4D, after liquid droplet305completely enters sensing area314, signal325does not fall below second threshold352. As liquid droplet305begins to leave sensing area314, signal325rises. After liquid droplet305completely leaves sensing area314signal325may once again exceed first threshold350. In contrast toFIGS.3D and4D, signal325does not cross second threshold352. Further, the duration between signal325crossing first threshold350is shorter compared to signal323ofFIG.3Dand signal324ofFIG.4D. Signal325looks like a flat or substantially flat line when below first threshold350, similar toFIG.3Dbut unlikeFIG.4D. The flat line may be attributed to the length of liquid droplet305being shorter than the length of sensing area314such that the entire liquid droplet305is in sensing area314for a longer duration than as shown inFIG.4D.

With reference to the various patterns observed in signals323,324,325, various liquid droplets303,304,305may be identified and characterized. A droplet rate or droplet size may be determined based on a magnitude of a pulse contained within the signal from light detector206(FIG.2). As used herein, the term “pulse” refers to a time when the signal falls below first threshold350. A greater magnitude drop of the pulse may indicate a larger droplet size or slower droplet rate. Further, qualitatively, if the signal crosses first threshold350twice but does not cross second threshold352in between, then the droplet size may be determined as less than channel width310. Vice versa, if the signal crosses second threshold352in between first threshold350crossings, then the droplet size may be qualitatively determined as at least the size of channel width310.

In some embodiments, a droplet size may be determined based on the magnitude of the pulse contained within the signal when the signal level does not cross the second threshold. When the signal does not cross the second threshold, the droplet size may be determined to be less than channel width310. In such cases, the droplet size may be determined based on the magnitude drop of the signal during the pulse. In general, the larger the magnitude drop, the larger the droplet size.

Additionally, or alternatively, a droplet rate or droplet size may be determined based on a width of a pulse contained within the signal from light detector206. A greater width of the pulse, between first threshold350crossings, between second threshold352crossings, or both, may indicate a larger droplet size or slower droplet rate.

In some embodiments, a droplet size may be determined based on the width of the pulse contained within the signal when the signal level crosses the second threshold. When the signal crosses the second threshold, the droplet size may be determined to be at least the size of channel width310. in such cases, the droplet size may be determined based on the time between crossings of the signal with one or both thresholds350,352, which may be used to indicate the width of the pulse. In general, the larger the width, the larger the droplet size.

First and second thresholds350,352may be empirically determined and stored by sensor controller106(FIG.2) for a particular application. A first threshold350may be set to detect a minimum size liquid droplet in sensing area314. In general, the lower first threshold350is set, the larger the minimum size of liquid droplet detection. A second threshold352may be set to detect a liquid droplet that fills sensing area314, such as liquid droplet303(FIG.3A) or liquid droplet304(FIG.4A), which may have a droplet size greater than or equal to channel width310. A droplet rate or droplet size may be determined based on whether the signal crosses first threshold, second threshold, or both.

A droplet rate or droplet size may be determined based on a threshold signal level crossing rate, or how quickly the signal crosses first threshold350, second threshold352, or both. For example, the crossing of the signal from above to below first threshold350or second threshold352may be measured, or vice versa. In some embodiments, the crossing of the signal across one threshold350,352may be used. For example, if the signal falls below first threshold350, the next time the signal falls below first threshold350, the signal must have risen above first threshold350. Therefore, a droplet rate may be determined using only one type of threshold crossing.

In some embodiments of the present disclosure, more than one microfluidic channel may be used in a droplet sensor. For example, at least another microfluidic channel may be included in each detection assembly. The sensor controller operably connected to light detector206(FIG.2) may be further configured to detect one or more liquid droplets dispersed in a flow of fluid through another microfluidic channel based on the signal from the light detector. The sensor controller may be configured to distinguish between liquid droplets flowing through each of the microfluidic channels.

FIGS.6and7show additional embodiments of detection assemblies450,452, which may be used with system100ofFIG.1. In the illustrated embodiments, each detection assembly450,452includes a plurality of microfluidic channels400. Each microfluidic channel400may share one inlet420and may share one outlet422. The fluid connections between microfluidic channels400, inlet420, and outlet422are shown schematically with dashed lines. In some embodiments (not shown), microfluidic channels400may be in fluid communication with different inlets420and may be in fluid communication with different outlets422. Inlet420and outlet422may be in fluid communication with a main fluid flow, for example, in fuel line114of system100. As illustrated, microfluidic channels400are in parallel fluid communication with fuel line114. Each detection assembly450,452includes light detector404and an opposing light source (not shown). Microfluidic channels400may share one light detector404and one light source.

Each microfluidic channel400may have the same or different cross-sectional area. In some embodiments, the cross-sectional areas of each microfluidic channel400may be differently sized to detect different droplet sizes. Using a plurality of microfluidic channels400may be used in various applications to allow more fluid to be sampled at the same pressure drop compared to using a single microfluidic channel, allow a higher flowrate of fluid through the detection assembly, or lower the pressure drop for the same amount of fluid sampled. For example, using a plurality of microfluidic channels400may be used in-line with a main flow of fluid through fuel line114.

Detection assembly450may include a plurality of light apertures402. Each light aperture402corresponds to one microfluidic channel400. Light apertures402may be used to define multiple light beams, which in turn define one sensing area per microfluidic channel400. As liquid droplets flow through each microfluidic channel400, light detector404will detect different levels of absorption corresponding to liquid droplets flowing through microfluidic channels400. Light apertures402may have the same or different widths, which may facilitate sensitivity to the different droplet sizes. Each light aperture402may have any suitable shape, such as a circular shape.

Detection assembly452may include a single light aperture412. Single light aperture412corresponds to the plurality of microfluidic channels400. In other words, the plurality of microfluidic channels400share one light aperture412. Light aperture412may have any suitable shape, such as a rectangular shape. In some embodiments (not shown), light aperture412may have different widths along each microfluidic channel400.

In some embodiments (not shown), more than one light detector404may be used. For example, each microfluidic channel400may have a corresponding light detector. Each light detector may be operably connected to the same or a different sensor controller.

FIG.8shows a layout of sensor controller106that may be used with droplet sensor102(FIGS.1and2). As illustrated, sensor controller106includes input interface500and output interface502. Sensor controller106may be operably connected to light detector206or optional flow sensor550using input interface500. Sensor controller106may be operably connected to computer122or light source202using output interface502. Each interface500,502may be operably connected to processor504, memory506, or both. Processor504may be operably coupled to memory506to store and retrieve information or data, such as signal510, threshold512, droplet rate520, droplet size522, or droplet amount524.

In the illustrated embodiment, processor504may be configured to receive signal510from light detector206using input interface500. One or more thresholds512may be determined by processor504based on signal510or retrieved from memory506. Various modules of processor504may be executed based on signal510and threshold512. For example, signal510and threshold512may be compared using comparator514executed on processor504. Based on the comparison, processor504may determine whether a liquid droplet has been detected using droplet detector516. Further, various characteristics of the liquid droplet may be determined using droplet characterizer518. Non-limiting examples of droplet characteristics that may be determined include droplet rate520, droplet size522, and droplet amount524. In some embodiments, processor504may determine to provide a maintenance signal526to output interface502.

A flow rate of fluid from flow sensor550may be used to determine some characteristics. In some embodiments, the flow meter or flow sensor550may be positioned in, upstream of, or downstream of the sensing channel or microfluidic channel. In general flow sensor550is positioned and configured to determine a flow rate of fluid through the microfluidic channel, which may also be described as a sensing channel.

FIG.9shows a flowchart describing method600that may be used with droplet sensor102ofFIG.2or sensor controller106ofFIG.8. Method600may include monitoring a signal602. If the monitored signal falls below a first threshold604, method600may continue and determine that a liquid droplet has been detected606. Otherwise, the signal may continue to be monitored602.

After a droplet has been detected606, if the signal exceeds the first threshold608, for example, without falling below the second threshold, method600may continue and determine a droplet size or rate610. For example, the droplet size may be determined to be less than a channel width of a microfluidic channel. As another example, a droplet rate may be determined based only on crosses of the first threshold. After the droplet size or rate is determined, the signal may continue to be monitored for another droplet602. If the signal has not yet exceeded the first threshold608, method600may continue and determine whether the signal has fallen below a second threshold612.

If the signal falls below the second threshold612, for example, before exceeding the first threshold, method600may determine droplet size or rate based on a pulse width614. As described herein above, a signal below the second threshold may indicate that the droplet size is greater than or equal to the channel width of the microfluidic channel, and the pulse width may indicate the droplet size or rate. After determining droplet size or rate614, the signal may continue to be monitored for another droplet602.

Otherwise, if the signal does not fall below the second threshold612, for example, before exceeding the first threshold, method600may determine droplet size based on a pulse magnitude616. As described herein above, a signal above the second threshold may indicate that the droplet size is less than the channel width of the microfluidic channel, and the pulse magnitude may indicate the droplet size. After determining droplet size616, the signal may continue to be monitored for another droplet602.

The droplet sensor may be integrated with a main flow line in any suitable manner. Controlling piping dimensions (e.g., length or hydraulic diameter) and observing the impact of minor pressure head losses (e.g., expansions or contractions in hydraulic diameter) may allow pressure losses in the overall system to be controlled. In some cases, the droplet sensor may be integrated in a manner to reduce overall pressure or energy loss, for example, facilitating a shorter microfluidic channel length.

The microfluidic sensor may be in parallel fluid communication with a main flow branch. In some embodiments, the microfluidic channel may be configured to accept a bypass flow from the main flow. In some embodiments, the microfluidic channel may be at least partially disposed within the main flow.

FIG.10shows one example of a droplet sensor that may be used with system100. Droplet sensor700includes microfluidic channel702positioned to receive a bypass flow from main flow channel704. One or both of main flow channel704or microfluidic channel702may include a bend to separate the bypass flow from the main flow.

In the illustrated embodiment, microfluidic channel702forms a straight path with main flow inlet706and main flow outlet708of main flow channel704. The straight geometry may prevent water drops or bubbles from being caught in microfluidic channel702. The main flow follows a different path along main flow branch710. As illustrated, main flow branch710is shown as a simple loop, but any suitable shape may be used to balance pressure and flow through the microchannel.

In some embodiments, microfluidic channel702may include a converging-diverging nozzle or converging-diverging nozzle design. The nozzle may improve pressure recovery, or otherwise control pressure losses, for example, by reducing the length of microfluidic channel702. In the illustrated embodiment, the nozzle may be defined by inlet portion712, sensing portion714(which may also be described as a throat of the nozzle), and outlet portion716. In other embodiments, sensing portion714may be incorporated into the inlet portion712or the outlet portion716.

In the illustrated embodiment, inlet portion712and outlet portion716each have widths that are variable, or that change, along their length. Length of microfluidic channel702is defined along an axis that extends along the direction of flow through microfluidic channel702. Width of microfluidic channel702is generally orthogonal to length. Sensing portion714may have a width that does not change along its length, for example, when sensing portion714is not incorporated into inlet portion712or outlet portion716.

Inlet portion712may taper in the direction of fluid flow, or flow direction, through microfluidic channel702. The taper may be linear or non-linear (e.g., curved). Inlet portion712may define a contraction angle, which is a measurement that may represent the angle of a linear taper or may represent an average measurement representative of multiple measurements of angles in a non-linear taper. An angle may be measured from any suitable axis, such as an axis aligned to the direction of bypass fluid flow through microfluidic channel702. Inlet portion712may be described as a contracting inlet portion.

Outlet portion716may flare in the direction of fluid flow, or flow direction, through microfluidic channel702. The flare may be linear or non-linear (e.g., curved). Outlet portion716may define an expansion angle, which may be calculated in a similar manner to the contraction angle. An angle may be measured from any suitable axis, such as an axis aligned to the direction of bypass fluid flow. Outlet portion716may be described as an expanding outlet portion.

Inlet portion712and outlet portion716may also be described using a contraction ratio and an expansion ratio. As used herein, “contraction ratio” refers to the ratio of the cross-sectional area at the nozzle inlet (widest cross-sectional area of inlet portion712or at the widest opening of the inlet portion) and the throat (the smallest cross-sectional area, such as in the sensing portion714). The “expansion ratio” refers to the ratio of the cross-sectional area at the nozzle outlet (widest cross-sectional area of outlet portion716or at the widest opening of the outlet portion). For example, a channel cross-sectional area that goes 300 micrometers down to 100 micrometers and back to 300 micrometers would have a contraction ratio of 3 and an expansion ratio of 3.

The lengths and corresponding angles of inlet portion712and outlet portion716may be the same or different. In some embodiments, the length of contracting inlet portion712is shorter than the length of the expanding outlet portion716, or vice versa. In some embodiments, the contraction angle of inlet portion712may be greater than the expansion angle of outlet portion716. In some embodiments, the expansion and contraction ratios may be the same or different. For example, the expansion ratio and the contraction ratio may be the same even though the corresponding lengths and angles are the different.

In the illustrated embodiment, main flow720, or main fluid flow, enters from the left side of the illustration into microfluidic channel702from main flow inlet706. The main flow720splits between main flow branch710and microfluidic channel702. The bypass flow enters microfluidic channel702at inlet portion712and increases in fluid velocity, while flow rate remains the same, as the cross-section decreases in inlet portion712causing the static pressure head to decrease. After the bypass flow passes from inlet portion712and sensing portion714and enters outlet portion716, the reverse occurs and the fluid velocity decreases, while flow rate remains the same, causing the static head pressure to increase. In other words, the fluid velocity may decrease, and the static head pressure may increase, after a minimum diameter of microfluidic channel702is encountered by the bypass flow. The bypass flow may then rejoin in the main flow after passing through outlet portion716.

By controlling the contraction and expansion rates, the amount of pressure recovery may be controlled, for example, by minimizing flow separation within the system. In properly engineered devices, minimizing flow separation may lead to sustainably less pressure drop at a given channel length compared to a constant cross-sectional area channel length. The converging-diverging nozzle design of microfluidic channel702may be used to control the pressure drop through droplet sensor700. A lower pressure drop may lead to additional flow through droplet sensor700.

System100may include a flow restrictor to facilitate fluid flow through droplet sensor700. In the illustrated embodiment, flow restrictor722may be positioned along the main flow channel704, for example, in main flow branch710. Flow restrictor722may facilitate driving more flow through microfluidic channel702compared to a system without flow restrictor722. In some cases, without flow restrictor722, less than or equal to 0.0001% of the main flow may enter microfluidic channel702, for example, when a width or diameter of microfluidic channel702is 150 micrometers and a width or diameter of main flow channel704is 12 millimeters. In general, the relative width of microfluidic channel702is much smaller compared to main flow channel704than illustrated (e.g., at least one order of magnitude). In some embodiments, at least 0.1, 0.5, 1, 1.5, 2, 2.5, 5, or even 10% of the main flow may enter microfluidic channel702, for example, when the converging-diverging nozzle or flow restrictor722is included.

Optical components may be used to increase the signal-to-noise ratio of droplet sensor700, for example, by increasing the intensity of light from light source730directed at light detector732. In one or more embodiments, droplet sensor704may include one or more optical components, such as focusing optics or a lens734. One or more lenses734may be positioned generally between light source730and light detector732. As illustrated one lens734is positioned between light source730and microfluidic channel702, and another lens734is positioned between microfluidic channel702and light detector732.

The microfluidic channel may be at least partially or fully submerged in the main flow of the fuel line. In some embodiments, an inlet of the microfluidic channel is positioned in the main flow or main flow channel.FIGS.11-13show various examples of positioning an inlet of the microfluidic channel to sample the main flow from the main flow channel. Main flow720through main flow channel704may be sampled by the droplet sensor from near the wall of main flow channel704(e.g., near the wall of the pipe) or from inside main flow channel704(e.g., inside the pipe). If main flow720is sampled from the middle of main flow channel704, the main flow720may be sampled from a straight section of pipe or from a bend in the pipe. Inlet portion712of microfluidic channel702may include opening752positioned to capture a representative fluid sample for the droplet sensor, a sample in which the water drops are concentrated, or a sample in which water drops are diluted. In general, the center of main flow channel704may provide a representative fluid sample of main flow720.

The opening752may have the same cross-sectional dimensions as microfluidic channel702or may be larger or smaller. Larger sensor inlet dimensions may be advantageous due to a lower pressure drop.

FIG.11shows droplet sensor750, which includes opening752at a distal end of inlet portion712extending from a side of main flow channel704toward a center of main flow channel704to position opening752near the center of main flow channel704. In the illustrated embodiment, main flow channel704extends linearly, or straight, and microfluidic channel702extends linearly, or straight, orthogonal to the direction of main flow720.

Main flow channel704may extend linearly or non-linearly. In some embodiments, one or more droplet sensor embodiments may also be used with a main flow channel having a bend or other non-linear geometry.FIG.12shows droplet sensor760, which includes opening752at a distal end of inlet portion712extending from bend754in main flow channel704to a center of main flow channel704to position opening752near the center of main flow channel704. In the illustrated embodiment, main flow channel704is non-linear. Microfluidic channel702enters into main flow channel704at bend754.

Inlet portion712of microfluidic channel702may be straight or include a taper (or converging nozzle).FIG.13shows droplet sensor770, which includes opening752at a distal end of inlet portion712extending from bend754to a center of main flow channel704to position opening752near the center of main flow channel704. Inlet portion712is at least partially tapered and opening752is larger compared to droplet sensor760(FIG.12). In the illustrated embodiment, main flow channel704extends linearly, or straight, and microfluidic channel702extends linearly, or straight, along the direction of main flow720.

The microfluidic channel may be entirely submerged in the main flow channel. In particular, the inlet and the outlet of the microfluidic channel may be positioned in the main flow of the main flow channel. In some embodiments, the droplet sensor may be in an annular flow configuration, in which the microfluidic sensor channel is contained within the main flow channel. The microfluidic channel may be located at the center of the main flow channel or away from the center.

The microfluidic sensor channel may be oriented in any suitable manner within the main flow channel. In some embodiments, the microfluidic sensor channel may run parallel to the direction of fluid flow or at an angle. The light source and detector may be submersed in the main flow channel, encapsulated and submersed, or coupled to the microfluidic channel with fiber optics, light guides, waveguides, or the like. The microfluidic channel may have a constant cross-sectional dimension (e.g., width) or may vary along its length. Varying the microfluidic sensor channel dimensions may be advantageous by lowering pressure drop or increasing sampling volume.

FIGS.14A-Band15A-B show various examples of microfluidic channels submerged in a main flow channel, which may facilitate having fewer bends in the path of fluid flow.FIGS.14A-Bshow one example of a droplet sensor with the light source and light detector submerged in a main flow channel. Droplet sensor800includes light source802, light detector804, and microfluidic channel806. In particular, inlet807(e.g., opening or inlet portion) and outlet809(e.g., opening or outlet portion) of microfluidic channel806are submerged in main flow channel810. Microfluidic channel806may be described as being surrounded by a wall, or interior surface, of main flow channel810.

To hold a substrate forming microfluidic channel806in the main flow, one or more supports812, or support structures, may be coupled to main flow channel810. In the illustrated embodiment, one support812is coupled between light source802and a wall of main flow channel810. Another support812is coupled between light detector804and a wall of main flow channel810and may be on the opposite side of main flow channel810or microfluidic channel806than the other support. The substrate forming microfluidic channel806may be coupled to light source802or a first support812and may be coupled to light detector804or a second support812to be held, for example, near a center of the main flow. Supports812may be made of any suitable material to mechanically couple different components of the droplet sensor800.

Microfluidic channel806may be formed from a substrate or defined between two or more optical components, for example, instead of being formed only from a substrate. In some embodiments, microfluidic channel806may be defined between two or more optical components, such as a light source, light detector, light aperture, light channel, lens, and separate microfluidic channel substrate. In some embodiments, microfluidic channel806may be formed of a glass tube as the substrate.

One example of a light channel is a fiber optic channel, or a channel formed by fiber optics. Use of fiber optics may allow certain optical components of the droplet sensor to be positioned outside of the main flow channel.FIGS.15A-Bshow one example of a droplet sensor with fiber optics at least partially submerged in a main flow channel that form a microfluidic channel. Droplet sensor820includes light source802, light detector804, and fiber optics814. In the illustrated embodiment, light source802and light detector804are positioned outside of main flow channel810and optically coupled to the interior of main flow channel810through fiber optics814. The microfluidic channel826may be defined in length and width by end portions of optical fibers of fiber optics814, for example, instead of a separate microfluidic channel substrate.

Various combinations of optical components may also be used to form the microfluidic channel. In some embodiments, a light source and a fiber optic channel may be used to define the microfluidic channel. In other embodiments, a light detector and a fiber optic channel may be used to define the microfluidic channel. In still further embodiments, the light source and light detector may be contained within main flow channel and define the microfluidic channel.

Optical components forming the microfluidic channel may be described as forming a virtual microfluidic channel between the two components. That is, the path length between the two components creates the microfluidic channel. The light detector or light source may be coupled to, or positioned relative to, a light aperture to define the virtual microfluidic channel.

In general, one or both of the light source and detector may be outside the main flow channel, where fiber optics, light guides, waveguides, or the like may be used to bring the light into or out of the main flow channel to or from the virtual microfluidic channel. Utilizing the virtual microfluidic channel may reduce pressure drop relative to using a separate substrate only to form the microfluidic channel.

Sensors similar to the droplet sensors described herein may also be used to detect water without a microfluidic channel. In some embodiments, such a sensor may be used to detect when a water volume or water level (e.g., based on height) has reached a certain threshold or used to monitor water level continuously. In some trucking applications, for example, understanding water height may help a truck operator understand when to drain water from the fuel system because a certain water volume has been collected. Existing water sensors in trucking applications utilize a mechanical float, which may be prone to fouling, or a resistive or conductive probe, which may also be prone to fouling through electroplating or deposits.

FIGS.16-18show various embodiments of sensors, such as water level sensors, used without a microfluidic channel in a fuel water separator or fuel filter, such as fuel filter116(FIG.1). When water is removed from a fuel system using a filter, the water may be collected in the bottom of a housing842of fuel water separator840in a water collection volume844, or bowl, after fuel is filtered. The water collection volume844may be fluidly connected to an engine fuel line (e.g., main flow channel) fluidly connected to filter element846and water drain outlet848to selectively drain water when water has reached threshold water level850. In general, the water collection volume844may be upstream of filter element846or downstream of filter element846.

Sensor852may be positioned at a height of water collection volume844corresponding to detect water reaching threshold water level850. Sensor852may include light source856, which may be a near-infrared light source. Sensor852may also include light detector858, which may be a photodetector. Light source856and light detector858may be positioned to define threshold water level850in the water collection volume844. The distance or space between lights source856and light detector858may define path length854.

A controller (which may be similar to controller106ofFIG.8) may be operably coupled to light detector858and optionally light source856. The controller may be configured to determine that water in water collection volume844has reached threshold water level850in response to the signal from light detector858. In general, when water is present between light source856and light detector858along path length854, in response, the controller may determine that the water volume has reached threshold water level850.

Various configurations of sensor852may be used to measure the water level.FIG.16shows sensor852having light source856and light detector858positioned outside of water collection volume844and housing842. In other embodiments, one or both of light source856and light detector858may be positioned inside water collection volume844or housing842and may be submersible in water.

FIG.17shows another example of a sensor configuration. Sensor860is similar to sensor852and further includes optical components862, or fiber optics. Optical components862may be used to couple light from light source856or light detector858into or out of water collection volume844. In the illustrated embodiment, light source856is positioned outside water collection volume844and is optically coupled to optical component862to direct a light beam into water collection volume844and toward light detector858. Light detector858is positioned inside water collection volume844to receive the light beam and is optically coupled to another optical component862to direct the light beam outside of water collection volume844. Path length854may be defined between optical component862coupled to light source856and light detector858.

FIG.18shows yet another example of a sensor configuration. Sensor870is similar to sensor860and is oriented to measure a water level by defining path length854in a direction to measure rising water levels (e.g., vertically). In particular, light source856and light detector858are positioned to measure a water level in water collection volume844and the controller (which may be similar to controller106ofFIG.8) is configured to determine the water level in response to the signal. As the water level rises along path length854, the absorptivity detected by light detector858will increase, and the controller may determine the water level, for example, in proportion to the increase in absorptivity. In the illustrated embodiment, light source856and light detector858are positioned inside water collection volume844and housing842. In other embodiments, light source856and light detector858may be positioned outside water collection volume844or housing842.

In general, a near-infrared light source and detector may be placed outside the water collection bowl. If the near-infrared light source and detector are outside the water collection volume, they may be coupled with fiber optics, wave guides, light guides (or similar) to bring the incoming light into the bowl, and to collect the transmitted light and bring it back out of the bowl. In some embodiments, one of the light source and detector may be in the water collection volume, while the other component may be outside the water collection bowl connected by a fiber optic, wave guide, or light guide. In other embodiments, both the light source and detector may be in the water collection volume.

The path length of the light may consist of a portion of the water collection volume width or height or may include the entire water collection bowl width or height. If the path length of light is the entire water collection volume width or height, the housing of the fuel water separator may be made from a material transparent to near-infrared light (e.g., glass) such that the light source and detector are outside the housing. If the sensor is oriented with the water collection bowl width, the sensor can act as a trigger once the water has reached the height of the sensor. If the sensor is oriented with the water collection bowl height (or at an oblique angle), the sensor can act as a continuous water level sensor as a decrease in transmitted light may indicate an increase in water height.

FIG.19shows one example of a fuel water separator including a filter head. In the illustrated embodiment, various positions for a sensor or droplet sensor884are shown within fuel water separator880. In some embodiments, one or more droplet sensors884may be positioned in filter head882. Filter head882may include an inlet and an outlet in fluid communication with a main flow channel and the filter element. Droplet sensor884may be positioned to sample along inlet890, along outlet892, between inlet and outlet, or even along or within filter element846.

In general, a microfluidic water sensor, or droplet sensor, may be integrated directly into the filter head. The sensor could be placed in the inlet or outlet of the filter head. The sensor could be a bypass to the filter connecting the inlet and outlet directly. The sensor may be incorporated directly into a replaceable filter element.

While the present disclosure is not so limited, an appreciation of various aspects of the disclosure will be gained through a discussion of the specific examples and illustrative embodiments provided below. Various modifications of the examples and illustrative embodiments, as well as additional embodiments of the disclosure, will become apparent herein.

Examples

In Example 1, detection assembly900was provided as shown inFIG.20. Detection assembly900included a near-infrared light-emitting diode (LED)902, which was centered at 1550 nm (available from Thorlabs, Newton, N.J.). LED902was driven by commercially-available 5V power source904connected using a Universal Seral Bus (USB) port. LED902was connected in series with a commercially available 51Ω resistor903. Light from LED902was not focused by an optics. LED902was brought into close proximity to microfluidic device906, made of poly(dimethylsiloxane) (PDMS) (available under trade name DOW CORNING SYLGARD 184) and glass, which defined a microfluidic channel. Microfluidic device906included a T-Junction droplet generator that fed water drops into the microchannel of microfluidic device906. The microchannel, or microfluidic channel, had a width of 150 micrometers and a depth of 140 micrometers. The channel was aligned with 150 μm-pinhole light aperture908(available from Thorlabs). Light from LED902was directed through the light aperture908and the microfluidic channel of microfluidic device906to be detected by a PDA30B germanium (Ge) transimpedance amplified light detector910(available from Thorlabs, Newton, N.J.). The output signal was transferred via a 50Ω BNC cable to a TDS 2014C oscilloscope (available from Tektronix, Beaverton, Oreg.).

A flow of fuel at 25 microliters per minute and a flow of water at 2 microliters per minute were provided to detection assembly900using syringe pumps (available from Harvard Apparatus, Holliston, Mass.), which resulted in the formation of water droplets. As determined from signal analysis, the water droplets had a diameter of 117 micrometers at a droplet rate of 40 droplets per second. Measurements were taken using the TDS 2014C oscilloscope set at a probe attenuation of 10×.FIG.21shows plot920of voltage (V) versus time (s) of signal922from the TDS 2014C oscilloscope. Each dip in signal922corresponded to a droplet moving through a sensing area defined by detection assembly900.

In Example 2, a detection assembly was fed with drops smaller than the dimensions of the microchannel of a microfluidic device to test whether the detector response would correspond, or correlate, to droplet diameter. The detection assembly was the same as detection assembly900, except that the microfluidic device used a flow focusing droplet generator was used instead of a T-Junction droplet generator was used to feed the microchannel and the oscilloscope was set at a 1× attenuation. From signal analysis, droplet frequency and size were determined. As illustrated inFIG.22, plot940shows the output voltage drop of the detector in millivolts (mV) for various droplet sizes (μm or micrometers). As can be seen, the greater voltage drops correspond to greater droplet diameters when the droplet is smaller than the width of the microchannel.

Illustrative Embodiments

In embodiment A1, a system comprises a microfluidic channel configured to receive a flow of a first fluid and a second fluid dispersed in the first fluid. The second fluid has a different composition than the first fluid. The system also comprises a light source configured to direct a light beam in a frequency band along a path through the microfluidic channel. The frequency band is selected to have a higher absorbance by the second fluid than by the first fluid. The system further comprises an aperture element defining a light aperture positioned in the path of the light beam from the light source. The system further comprises a light detector positioned to receive the light beam in a sensing area after passing through the microfluidic channel and the light aperture. The light detector is configured to provide a signal representing an amount of light in the frequency band that remains after passing through the microfluidic channel. The system further comprises a controller operably coupled to the light detector and configured to determine whether the second fluid is in droplet form based on the signal.

In embodiment A2, a system comprises the system according to any A embodiment, wherein the controller is further configured to determine an amount of second liquid in droplet form per unit volume of first fluid based on the signal. The amount optionally excludes second fluid dissolved in first fluid.

In embodiment A3, a system comprises the system according to any A embodiment, further comprising a controller operably connected to the light detector and configured to detect a droplet rate or a droplet size of one or more droplets of the second fluid dispersed in the flow of the first fluid based on the signal.

In embodiment A4, a system comprises the system according to embodiment A3, wherein the controller is further configured to determine the droplet rate or the droplet size based on at least one of: a magnitude of a pulse contained within the signal, a width of a pulse contained within the signal, a first threshold signal level for detecting a minimum size droplet in the sensing area, a second threshold signal level for detecting a droplet that fills the sensing area, and a threshold signal level crossing rate.

In embodiment A5, a system comprises the system according to embodiment A4, wherein the controller is further configured to determine at least one of: an amount of second liquid in droplet form per unit volume of first fluid based on the droplet rate and droplet size; the droplet size based on the magnitude of a pulse contained within the signal in response to the signal not crossing the second threshold signal level; the droplet size based on the width of a pulse contained within the signal in response to the signal crossing the second threshold signal level; and the droplet size based on the droplet rate.

In embodiment A6, a system comprises the system according to any A embodiment, wherein the microfluidic channel is at least one of: in parallel fluid communication with a main flow of a fuel line; at least partially submerged in the main flow of the fuel line, wherein an inlet of the microfluidic channel is positioned in the main flow of the fuel line or the inlet and an outlet of the microfluidic channel is positioned in the main flow of the fuel line; and defined between two or more optical components selected from: the light source, the light detector, the light aperture, a light channel, a lens, and a separate microfluidic channel substrate.

In embodiment A7, a system comprises the system according to any A embodiment, wherein the microfluidic channel comprises a converging-diverging nozzle.

In embodiment A8, a system comprises the system according to embodiment 7, wherein: the converging-diverging nozzle of the microfluidic channel comprises a contracting inlet portion and an expanding outlet portion along a flow direction; and optionally wherein a length of the contracting inlet portion is shorter than a length of the expanding outlet portion.

In embodiment A9, a system comprises the system according to any A embodiment, wherein the controller is further configured to detect a droplet of the second liquid of a predetermined size having an equivalent volume to a droplet of the second liquid having a spherical diameter in a range from 10 up to 1000 micrometers.

In embodiment A10, a system comprises the system according to any A embodiment, wherein the first fluid comprises a hydrocarbon fluid and the second fluid comprises water.

In embodiment A11, a system comprises the system according to any A embodiment, further comprising at least one of: a fuel line configured to deliver fuel a fuel injector; a fuel filter configured to filter water from gasoline or diesel fuel positioned along the fuel line; and a fuel pump in fluid communication with the fuel line, wherein the fuel pump is configured to provide fuel flow to the fuel injector along the fuel line.

In embodiment A12, a system comprises the system according to any A embodiment, further comprising another microfluidic channel positioned between the light source and the light detector.

In embodiment A13, a system comprises the system according to any A embodiment, wherein the microfluidic channel defines a cross-sectional area less than 1 mm2and the light aperture has a width less than 1 mm to define the sensing area.

In embodiment A14, a system comprises a fuel and water separator comprising a housing defining a water collection volume. The water collection volume is fluidly connected to an engine fuel line and fluidly connected to a water drain outlet. The system also comprises a light source configured to direct a light beam in a frequency band along a path through the water collection volume. The frequency band is selected to be absorbed by water. The system further comprises a light detector positioned to receive the light beam in a sensing area after passing through at least part of the water collection volume. The light detector is configured to provide a signal representing an amount of light in the frequency band. The system further comprises a controller operably coupled to the light detector and configured to determine whether water is detected based on the signal.

In embodiment A15, a system comprises the system according to embodiment A14, wherein: the light source and light detector are positioned to define a threshold water level in the water collection volume and the controller is configured to determine that water in the water collection volume has reached the threshold water level in response to the signal; or the light source and the light detector are positioned to measure a water level in the water collection volume and the controller is configured to determine the water level in response to the signal.

In embodiment B1, a system comprises a microfluidic channel configured to receive a flow of hydrocarbon fluid. The microfluidic channel has a cross-sectional area sized to receive one water droplet at a time when a water droplet of a predetermined size is dispersed in the hydrocarbon fluid. The system also comprises a light source positioned outside the microfluidic channel configured to generate light in a selected frequency band such that the water droplet has a higher absorbance than the hydrocarbon fluid in the selected frequency band. The system further comprises a light detector sensitive to the selected frequency band positioned outside the microfluidic channel and configured to provide a signal representing an amount of light remaining after passing through the microfluidic channel. The system further comprises a light aperture positioned between the light source and the light detector. Light from the light source passing through the light aperture forms a light beam defining a beam axis that extends through the light source, the microfluidic channel, and the light detector. The system further comprises a controller operably connected to the light detector and configured to detect one or more water droplets dispersed in the flow of hydrocarbon fluid based on the signal from the light detector representing the amount of light from the light source remaining after passing through the microfluidic channel and the light aperture.

In embodiment B2, a system comprises the system according to any B embodiment, wherein the controller is configured to determine an amount of water per unit volume excluding dissolved water based on the signal from the light detector.

In embodiment B3, a system comprises the system according to any B embodiment, wherein the controller is configured to detect the water droplet of the predetermined size having a volume corresponding to a spherical diameter in a range from 10 up to 1000 micrometers based on the signal from the light detector.

In embodiment B4, a system comprises the system according to any B embodiment, wherein the controller is configured to provide a maintenance signal in response to detecting water in hydrocarbon fluid based on the signal from the light detector.

In embodiment B5, a system comprises the system according to any B embodiment, further comprising a fuel line configured to deliver fuel as the hydrocarbon fluid to a fuel injector, wherein the microfluidic channel is in parallel fluid communication with the fuel line.

In embodiment B6, a system comprises the system according to embodiment B5, further comprising a fuel filter configured to filter water from gasoline or diesel fuel positioned along the fuel line.

In embodiment B7, a system comprises the system according to embodiment B6, further comprising a fuel pump in fluid communication with the fuel line, wherein the fuel pump is configured to provide fuel flow to the fuel injector along the fuel line.

In embodiment B8, a system comprises the system according to any B embodiment, further comprising another microfluidic channel positioned between the light source and the light detector. The controller is further configured to detect one or more water droplets dispersed in a flow of hydrocarbon fluid through the another microfluidic channel based on the signal from the light detector.

In embodiment C1, a sensor comprises a microfluidic channel sized to receive a flow of fluid. The microfluidic channel has a cross-sectional area sized to receive one liquid droplet at a time when a liquid droplet of a different liquid of a predetermined size is dispersed in the fluid. The sensor also comprises a light source positioned outside the microfluidic channel configured to generate light in a selected frequency band such that the droplets have a different absorbance than the different liquid in the selected frequency band. The sensor further comprises a light detector sensitive to the selected frequency band positioned outside the microfluidic channel and configured to provide a signal representing an amount of light remaining after passing through the microfluidic channel. The sensor further comprises a light aperture positioned between the light source and the light detector. Light from the light source passing through the light aperture forms a light beam defining a beam axis that extends through the light source, the microfluidic channel, and the light detector. A width of the light aperture and the light detector define a sensing area. The sensor further comprises a controller operably connected to the light detector and configured to determine a droplet rate through the sensing area of the microfluidic channel based on the signal from the light detector representing the amount of light from the light source remaining after passing through the microfluidic channel and the light aperture.

In embodiment C2, a sensor comprises the sensor according to any C embodiment, wherein the controller is configured to determine the droplet rate or a droplet size based on at least one of: a magnitude of a pulse contained within the signal, a width of a pulse contained within the signal, a first threshold signal level for detecting a minimum size droplet in the sensing area, a second threshold signal level for detecting a droplet that fills the sensing area, and a threshold signal level crossing rate.

In embodiment C3, a sensor comprises the sensor according to any C embodiment, wherein the controller is configured to determine an amount of droplet liquid per unit volume based on the droplet rate and droplet size.

In embodiment C4, a sensor comprises the sensor according to any C embodiment, wherein the controller is configured to determine the droplet size based on the magnitude of a pulse contained within the signal when the signal level does not cross the second threshold signal level.

In embodiment C5, a sensor comprises the sensor according to any C embodiment, wherein the controller is configured to determine the droplet size based on the width of a pulse contained within the signal when the signal level crosses the second threshold signal level.

In embodiment C6, a sensor comprises the sensor according to any C embodiment, wherein the controller is configured to determine a droplet size based on the droplet rate.

In embodiment D1, a water droplet sensor comprises a microfluidic channel defining a cross-sectional area less than 1 mm2, a light source positioned outside the microfluidic channel configured to generate light in a near infrared frequency band, a light detector sensitive to the frequency band positioned outside the microfluidic channel and configured to provide a signal representing an amount of light remaining after passing through the microfluidic channel, and a light aperture positioned between the light source and the light detector. Light from the light source passing through the light aperture forms a light beam defining a beam axis that extends through the light source, the microfluidic channel, and the light detector. The aperture has a width less than 1 mm. The sensor also comprises a controller operably connected to the light detector and configured to detect one or more water droplets dispersed in a flow of hydrocarbon fluid based on the signal from the light detector representing the amount of light from the light source remaining after passing through the microfluidic channel and the light aperture.

In embodiment D2, a sensor comprises the sensor according to any D embodiment, wherein the light source is configured to generate light centered in the range from 1400 to 1600 nanometers.

In embodiment D3, a sensor comprises the sensor according to any D embodiment, wherein a path length of the light beam from the light aperture to the light detector is less than or equal to 1000 micrometers.

In embodiment D4, a sensor comprises the sensor according to any D embodiment, wherein at least one of a channel width of the microfluidic channel and the width of the aperture is less than or equal to 500 micrometers.

In embodiment D5, a sensor comprises the sensor according to any D embodiment, wherein a channel depth of the microfluidic channel is less than or equal to a channel width of the microfluidic channel.

In embodiment D6, a sensor comprises the sensor according to any D embodiment, wherein the width of the aperture is less than or equal to a channel width of the microfluidic channel.

Thus, various embodiments of the DROPLET SENSORS FOR FUEL SYSTEMS are disclosed. Although reference is made herein to the accompanying set of drawings that form part of this disclosure, one of at least ordinary skill in the art will appreciate that various adaptations and modifications of the embodiments described herein are within, or do not depart from, the scope of this disclosure. For example, aspects of the embodiments described herein may be combined in a variety of ways with each other. Therefore, it is to be understood that, within the scope of the appended claims, the claimed invention may be practiced other than as explicitly described herein.

All references and publications cited herein are expressly incorporated herein by reference in their entirety into this disclosure, except to the extent they may directly contradict this disclosure.

Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties used in the specification and claims may be understood as being modified either by the term “exactly” or “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein or, for example, within typical ranges of experimental error.

The recitation of numerical ranges by endpoints includes all numbers subsumed within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and any range within that range. Herein, the terms “up to” or “less than or equal to” a number (e.g., up to 50) includes the number (e.g., 50), and the term “no less than” a number (e.g., no less than 5) includes the number (e.g., 5).

The terms “coupled” or “connected” refer to elements being attached to each other either directly (in direct contact with each other) or indirectly (having one or more elements between and attaching the two elements). Either term may be modified by “operatively” and “operably,” which may be used interchangeably, to describe that the coupling or connection is configured to allow the components to interact to carry out at least some functionality (for example, sensor controller may be operatively connected to vehicle computer to send and receive data).

Terms related to orientation, such as “top,” “bottom,” “upstream,” and “downstream,” are used to describe relative positions of components and are not meant to limit the orientation of the embodiments contemplated.

The phrases “at least one of,” “comprises at least one of,” and “one or more of” followed by a list refers to any one of the items in the list and any combination of two or more items in the list.