Integrated fuel composition and pressure sensor

Methods and systems are provided for an integrated fuel composition-pressure sensor. In one example, the integrated sensor may include a set of cylindrical capacitors and a set of plate capacitors with a common capacitor element shared between the sets. A composition of fuel may be determined from the set of cylindrical capacitors and a pressure of fuel may be determined from the set of plate capacitors.

FIELD

The present description relates generally to an electronic device for determining a fuel composition and a fuel pressure in a fuel line.

Flexible fuel vehicles (FFVs) are an alternative to conventional gasoline-driven vehicles and include an internal combustion engine to combust mixtures of gasoline and a secondary fuel, such as methanol, ethanol, propanol, or other alcohols and octane improvers. Fuel blends incorporating ethanol are particularly popular due to a derivation of ethanol from biomass, with various feedstocks available from agriculture. A flexible fuel engine may be adapted to burn fuel mixtures of 0-100% ethanol, thereby reducing gasoline consumption and emission of undesirable byproducts of gasoline combustion.

In order to adjust engine operations to accommodate changes in fuel composition, a powertrain control module (PCM) may undergo a learning process. The PCM's ability to effectively diagnose changes in fueling conditions may be dependent on reception of accurate signals to provide parameters as a basis for calculations. For example, to determine suitable air-fuel ratios at combustion chambers of the engine, the PCM may utilize an estimate or measurement of the fuel composition (e.g., percentage of ethanol) and a fuel pressure to determine an amount of fuel to be injected.

The PCM may obtain such information from sensors configured to measure pressure and fuel composition. In one approach described by Tuckey et al. in U.S. Pat. No. 5,044,344, a fuel delivery system of an engine includes a fuel delivery module configured with a sensor that is responsive to fuel alcohol concentration. The fuel delivery module also includes a pressure sensor coupled to the fuel delivery line to measure a fuel delivery pressure. Signals from the pressure sensor and alcohol concentration sensor are sent to an amplifier that communicates with a fuel pump that drives fuel flow to the engine.

However, the inventors herein have recognized potential issues with such systems. As one example, the use of separate sensors to measure the pressure and composition of fuel combusted in the engine adds complexity, costs, weight, and packaging space of the fuel system. In addition, the sensors disclosed in U.S. Pat. No. 5,044,344 are positioned in the fuel tank and may not account for pressure losses in the fuel line with distance from the fuel tank. As fuel flows through the fuel line before reaching the combustion chambers, a final delivery pressure may differ significantly from pressures measured at the tank and lead to poor combustion efficiency.

In one example, the issues described above may be addressed by an integrated fuel composition and pressure sensor, comprising a set of cylindrical capacitors concentrically arranged and spaced apart from one another, where the set of cylindrical capacitors are adapted to receive a flow of fluid axially through each capacitor of the set of cylindrical capacitors, and a set of plate capacitors spaced apart from one another, where a common capacitor element is shared between the set of cylindrical capacitors and set of plate capacitors. In this way, fuel pressure and fuel composition of fuel may be measured by a single sensor that may be positioned proximal to combustion chambers of the engine.

As one example, the electronic device includes a first set of ceramic plates for determining the fuel pressure and a second set of concentric cylindrical ceramic plates for determining fuel composition of fuel. A shell of an outer cylindrical plate of the second set of ceramic plates may be shared between the two sets of ceramic plates and used in both measurements. A capacitance may be calculated between each of the first and second sets of plates based on a voltage potential. A permittivity of the fuel flowing through the electronic device may be determined by the second set of cylindrical ceramic plates and used to calculate a percentage of ethanol in the fuel. The permittivity may also be used to calculate a capacitance of the first set of ceramic plates which, along with an adjustment to account for a change in fluid pressure due to flow through the electronic device, may determine the fuel pressure.

DETAILED DESCRIPTION

The following description relates to a device for measuring both fuel composition and fuel pressure of a fuel combusted in an engine. The device may be included in an engine system of a vehicle and in particular, positioned in a fuel line between a fuel tank and cylinders of an engine. An example of a vehicle including such an engine system is given inFIG. 1and an example of an engine system configured with the device is shown inFIG. 2. The device may be an integrated sensor for measuring both a pressure and composition of fuel combusted at the engine. The integrated sensor may include sensing elements including integrated capacitance plates and concentrically arranged capacitance cylinders, as illustrated in a side cut-away view of the integrated composition-pressure sensor inFIG. 3. Cross-sections of the integrated composition-pressure sensor, providing a view perpendicular to the view ofFIG. 3are shown inFIGS. 4 and 5, illustrating variations in a geometry of a second cylinder of the integrated composition-pressure sensor.FIG. 6is an example of a method for operating the integrated composition-pressure sensor to obtain a composition of a fuel blend flowing from the fuel tank to the engine. Variables that may be used to calculate the fuel composition and fuel pressure as described in the method ofFIG. 6are represented in schematic diagrams of cylindrical capacitors used to determine the fuel composition and capacitor plates used in combination with the cylindrical capacitors to determine the fuel pressure inFIGS. 7, 8, and 10. A schematic diagram depicted inFIG. 9illustrates a transmission of electronic signals from the integrated composition-pressure sensor to an engine controller where the determined fuel composition and fuel pressure may be used to adjust engine operations such as spark, fuel injection, and crankshaft timing.

Turning now to the figures,FIG. 1illustrates an example vehicle propulsion system100. Vehicle propulsion system100includes a fuel burning engine110and a motor120. As a non-limiting example, engine110comprises an internal combustion engine and motor120comprises an electric motor. Motor120may be configured to utilize or consume a different energy source than engine110. For example, engine110may consume a liquid fuel (e.g. gasoline, ethanol, or a gasoline-ethanol blend) to produce an engine output while motor120may consume electrical energy to produce a motor output. As such, a vehicle with propulsion system100may be referred to as a hybrid electric vehicle (HEV) and a vehicle that combusts fuel mixtures may be referred to as a flexible fuel vehicle (FFV).

Vehicle propulsion system100may utilize a variety of different operational modes depending on operating conditions encountered by the vehicle propulsion system. Some of these modes may enable engine110to be maintained in an off state (e.g., set to a deactivated state) where combustion of fuel at the engine is discontinued. For example, under select operating conditions, motor120may propel the vehicle via drive wheel130as indicated by arrow122while engine110is deactivated.

During other operating conditions, engine110may be set to a deactivated state (as described above) while motor120may be operated to charge energy storage device150. For example, motor120may receive wheel torque from drive wheel130as indicated by arrow122where the motor may convert the kinetic energy of the vehicle to electrical energy for storage at energy storage device150as indicated by arrow124. This operation may be referred to as regenerative braking of the vehicle. Thus, motor120can provide a generator function in some embodiments. However, in other embodiments, generator160may instead receive wheel torque from drive wheel130, where the generator may convert the kinetic energy of the vehicle to electrical energy for storage at energy storage device150as indicated by arrow162.

During still other operating conditions, engine110may be operated by combusting fuel received from fuel system140as indicated by arrow142. For example, engine110may be operated to propel the vehicle via drive wheel130as indicated by arrow112while motor120is deactivated. During other operating conditions, both engine110and motor120may each be operated to propel the vehicle via drive wheel130as indicated by arrows112and122, respectively. A configuration where both the engine and the motor may selectively propel the vehicle may be referred to as a parallel type vehicle propulsion system. Note that in some embodiments, motor120may propel the vehicle via a first set of drive wheels and engine110may propel the vehicle via a second set of drive wheels.

In other embodiments, vehicle propulsion system100may be configured as a series type vehicle propulsion system, whereby the engine does not directly propel the drive wheels. Rather, engine110may be operated to power motor120, which may in turn propel the vehicle via drive wheel130as indicated by arrow122. For example, during select operating conditions, engine110may drive generator160, which may in turn supply electrical energy to one or more of motor120as indicated by arrow114or energy storage device150as indicated by arrow162. As another example, engine110may be operated to drive motor120which may in turn provide a generator function to convert the engine output to electrical energy, where the electrical energy may be stored at energy storage device150for later use by the motor. The vehicle propulsion system may also be configured to transition between two or more of the operating modes described above depending on operating conditions.

Fuel system140may include one or more fuel storage tanks144for storing fuel on-board the vehicle. For example, fuel tank144may store one or more liquid fuels, including but not limited to: gasoline, diesel, and alcohol fuels. In some examples, the fuel may be stored on-board the vehicle as a blend of two or more different fuels. For example, fuel tank144may be configured to store a blend of gasoline and ethanol (e.g. E10, E85, etc.) or a blend of gasoline and methanol (e.g. M10, M85, etc.), whereby these fuels or fuel blends may be delivered to engine110as indicated by arrow142. Still other suitable fuels or fuel blends may be supplied to engine110, where they may be combusted at the engine to produce an engine output. The engine output may be utilized to propel the vehicle as indicated by arrow112or to recharge energy storage device150via motor120or generator160.

In some embodiments, energy storage device150may be configured to store electrical energy that may be supplied to other electrical loads residing on-board the vehicle (other than the motor), including cabin heating and air conditioning, engine starting, headlights, cabin audio and video systems, etc. As a non-limiting example, energy storage device150may include one or more batteries and/or capacitors.

Control system190may communicate with one or more of engine110, motor120, fuel system140, energy storage device150, and generator160. Control system190may receive sensory feedback information from one or more of engine110, motor120, fuel system140, energy storage device150, and generator160. Further, control system190may send control signals to one or more of engine110, motor120, fuel system140, energy storage device150, and generator160responsive to this sensory feedback. Control system190may receive an indication of an operator requested output of the vehicle propulsion system from a vehicle operator102. For example, control system190may receive sensory feedback from pedal position sensor194which communicates with pedal192. Pedal192may refer schematically to a brake pedal and/or an accelerator pedal.

In other embodiments, electrical transmission cable182may be omitted, where electrical energy may be received wirelessly at energy storage device150from power source180. For example, energy storage device150may receive electrical energy from power source180via one or more of electromagnetic induction, radio waves, and electromagnetic resonance. As such, it should be appreciated that any suitable approach may be used for recharging energy storage device150from a power source that does not comprise part of the vehicle. In this way, motor120may propel the vehicle by utilizing an energy source other than the fuel utilized by engine110. Fuel system140may periodically receive fuel from a fuel source residing external to the vehicle. As a non-limiting example, vehicle propulsion system100may be refueled by receiving fuel via a fuel dispensing device170as indicated by arrow172. In some embodiments, fuel tank144may be configured to store the fuel received from fuel dispensing device170until it is supplied to engine110for combustion. In some embodiments, control system190may receive an indication of the level of fuel stored at fuel tank144via a fuel level sensor. The level of fuel stored at fuel tank144(e.g. as identified by the fuel level sensor) may be communicated to the vehicle operator, for example, via a fuel gauge or indication lamp indicated at196. Furthermore, the fuel system140may include one or more sensors for detecting a fuel composition when more than one fuel type is used for combustion, as well as for measuring a fuel pressure.

FIG. 2shows a schematic depiction of a vehicle system200. The vehicle system200includes an engine system208coupled to an emissions control system251and a fuel system218. Emission control system251includes a fuel vapor container or canister222which may be used to capture and store fuel vapors. In some examples, vehicle system200may be a flexible fuel vehicle system (FFV) and/or a hybrid electric vehicle system.

The engine system208may include an engine210having a plurality of cylinders230. The engine210includes an engine intake223and an engine exhaust225. The engine intake223includes a throttle262fluidly coupled to an engine intake manifold244via an intake passage242. The engine exhaust225includes an exhaust manifold248leading to an exhaust passage235that routes exhaust gas to the atmosphere. The engine exhaust225may include one or more emission control devices270, which may be mounted in a close-coupled position in the exhaust. One or more emission control devices may include a three-way catalyst, lean NOx trap, diesel or gasoline particulate filter, oxidation catalyst, etc. In some examples, the exhaust manifold248may be configured with exhaust gas recirculation, coupling the exhaust manifold to the intake passage242upstream of the engine intake223to mix burnt gas with intake air prior to re-combustion (not shown inFIG. 2). It will be appreciated that other components may be included in the engine such as a variety of valves and sensors.

Fuel system218may include a fuel tank220coupled to a fuel pump system221. The fuel pump system221may include one or more pumps for pressurizing fuel delivered to the injectors of engine210, such as the example injector266shown. While only a single injector266is shown, additional injectors are provided for each cylinder. It will be appreciated that fuel system218may be a return-less fuel system, a return fuel system, or various other types of fuel system. Fuel tank220may hold a plurality of fuel blends, including fuel with a range of alcohol concentrations, such as various gasoline-ethanol blends, including E10, E85, gasoline, etc., and combinations thereof.

For example, fuel tank220is shown inFIG. 2with a first inner compartment224and a second inner compartment226. A first type of fuel, such as gasoline, may be stored in the first inner compartment224, and a second type of fuel, such as ethanol, may be stored in the second inner compartment226. Fuel level sensors234located in the first inner compartment224and the second inner compartment226of fuel tank220may provide an indication of the fuel levels (“Fuel Level Input”) to controller212. As depicted, fuel level sensors234may comprise a float connected to a variable resistor. Alternatively, other types of fuel level sensors may be used. Valves238and239may control flow of fuel from the first and second inner compartments224,226, into a mixing compartment240, where the two fuel types may be mixed in a desired ratio before being pumped through into a fuel line236by the fuel pump221.

Fuel line236couples the fuel tank220to the engine210. Efficient combustion and peak torque derived from combustion may depend on engine operations such as spark timing, fuel injection timing, intake and exhaust valve timing, shifting at the transmission, etc. Adjustment of the engine operations to provide a desirable engine performance may be conducted according to a measured fuel composition and fuel pressure. The fuel composition and fuel pressure may be determined by an integrated sensor202, arranged inline in the fuel line236and positioned closer to the engine210than the fuel tank220. The integrated sensor202may be a single device configured to measure both a pressure and composition of the fuel in the fuel line236. The measurements may be obtained by electrical outputs of shared elements of the integrated sensor202to determine individual values of pressure and composition. In this way, fuel flowing through fuel line236may flow directly through (e.g., through a center or central portion of) the integrated sensor202. The integrated sensor202may output signals (e.g., two signals from two different electrodes, as explained further below) to the controller212which may then be used by the controller212to determine (e.g., calculate) a percentage of ethanol in the fuel, for example, and a pressure of the fuel in the fuel line236between the integrated sensor202and the engine210. Components and operation of the integrated sensor202are elaborated below in descriptions ofFIGS. 3-8.

Vapors generated in fuel system218may be routed to an evaporative emissions control system251which includes a fuel vapor canister222via vapor recovery line231, before being purged to the engine intake223. Vapor recovery line231may be coupled to fuel tank220via one or more conduits and may include one or more valves for isolating the fuel tank during certain conditions. For example, vapor recovery line231may be coupled to fuel tank220via one or more or a combination of conduits271,273, and275.

Further, in some examples, one or more fuel tank vent valves are in conduits271,273, or275. Among other functions, fuel tank vent valves may allow a fuel vapor canister of the emissions control system to be maintained at a low pressure or vacuum without increasing the fuel evaporation rate from the tank (which would otherwise occur if the fuel tank pressure were lowered). For example, conduit271may include a grade vent valve (GVV)287, conduit273may include a fill limit venting valve (FLVV)285, and conduit275may include a grade vent valve (GVV)283. Further, in some examples, recovery line231may be coupled to a fuel filler system219. In some examples, fuel filler system may include a fuel cap205for sealing off the fuel filler system from the atmosphere. Refueling system219is coupled to fuel tank220via a fuel filler pipe or neck211.

Further, refueling system219may include refueling lock245. In some embodiments, refueling lock245may be a fuel cap locking mechanism. The fuel cap locking mechanism may be configured to automatically lock the fuel cap in a closed position so that the fuel cap cannot be opened. For example, the fuel cap205may remain locked via refueling lock245while pressure or vacuum in the fuel tank is greater than a threshold. In response to a refuel request, e.g., a vehicle operator initiated request, the fuel tank may be depressurized and the fuel cap unlocked after the pressure or vacuum in the fuel tank falls below a threshold. The fuel cap locking mechanism may alternatively be a latch or clutch, which, when engaged, prevents the removal of the fuel cap. The latch or clutch may be electrically locked, for example, by a solenoid, or may be mechanically locked, for example, by a pressure diaphragm.

In some embodiments, refueling lock245may be a filler pipe valve located at a mouth of fuel filler pipe211. In such embodiments, refueling lock245may not prevent the removal of fuel cap205. Rather, refueling lock245may prevent the insertion of a refueling pump into fuel filler pipe211. The filler pipe valve may be electrically locked, for example by a solenoid, or mechanically locked, for example by a pressure diaphragm. In other embodiments, refueling lock may be a refueling door lock or locked using an electrical mechanism.

Emissions control system251may include one or more emissions control devices, such as one or more fuel vapor canisters222filled with an appropriate adsorbent, the canisters are configured to temporarily trap fuel vapors (including vaporized hydrocarbons) during fuel tank refilling operations and “running loss” (that is, fuel vaporized during vehicle operation). In one example, the adsorbent used is activated charcoal. Emissions control system251may further include a canister ventilation path or vent line227which may route gases out of the canister222to the atmosphere when storing, or trapping, fuel vapors from fuel system218.

Canister222may include a buffer222a(or buffer region), each of the canister and the buffer comprising the adsorbent. As shown, the volume of buffer222amay be smaller than (e.g., a fraction of) the volume of canister222. The adsorbent in the buffer222amay be same as, or different from, the adsorbent in the canister (e.g., both may include charcoal). Buffer222amay be positioned within canister222such that during canister loading, fuel tank vapors are first adsorbed within the buffer, and then when the buffer is saturated, further fuel tank vapors are adsorbed in the canister. In comparison, during canister purging, fuel vapors are first desorbed from the canister (e.g., to a threshold amount) before being desorbed from the buffer. In other words, loading and unloading of the buffer is not linear with the loading and unloading of the canister. As such, the effect of the canister buffer is to dampen any fuel vapor spikes flowing from the fuel tank to the canister, thereby reducing the possibility of any fuel vapor spikes going to the engine. One or more temperature sensors232may be coupled to and/or within canister222. As fuel vapor is adsorbed by the adsorbent in the canister, heat is generated (heat of adsorption). Likewise, as fuel vapor is desorbed by the adsorbent in the canister, heat is consumed. In this way, the adsorption and desorption of fuel vapor by the canister may be monitored and estimated based on temperature changes within the canister.

Vent line227may also allow fresh air to be drawn into canister222when purging stored fuel vapors from fuel system218to engine intake223via purge line228and purge valve261. For example, purge valve261may be normally closed but may be opened during certain conditions so that vacuum from engine intake manifold244is provided to the fuel vapor canister for purging. In some examples, vent line227may include an air filter259disposed therein upstream of a canister222.

In some examples, the flow of air and vapors between canister222and the atmosphere may be regulated by a canister vent valve coupled within vent line227. When included, the canister vent valve may be a normally open valve, so that fuel tank isolation valve252(FTIV) may control venting of fuel tank220with the atmosphere. FTIV252may be positioned between the fuel tank and the fuel vapor canister within conduit278. FTIV252may be a normally closed valve, that when opened, allows for the venting of fuel vapors from fuel tank220to canister222. Fuel vapors may then be vented to atmosphere, or purged to engine intake system223via canister purge valve261.

Fuel system218may be operated by controller212in a plurality of modes by selective adjustment of the various valves and solenoids. For example, the fuel system may be operated in a fuel vapor storage mode (e g., during a fuel tank refueling operation and with the engine not running), wherein the controller212may open isolation valve252while closing canister purge valve (CPV)261to direct refueling vapors into canister222while preventing fuel vapors from being directed into the intake manifold.

As another example, the fuel system may be operated in a refueling mode (e.g., when fuel tank refueling is requested by a vehicle operator), wherein the controller212may open isolation valve252, while maintaining canister purge valve261closed, to depressurize the fuel tank before allowing enabling fuel to be added therein. As such, isolation valve252may be kept open during the refueling operation to allow refueling vapors to be stored in the canister. After refueling is completed, the isolation valve may be closed.

As yet another example, the fuel system may be operated in a canister purging mode (e.g., after an emission control device light-off temperature has been attained and with the engine running), wherein the controller212may open canister purge valve261while closing isolation valve252. Herein, the vacuum generated by the intake manifold of the operating engine may be used to draw fresh air through vent27and through fuel vapor canister22to purge the stored fuel vapors into intake manifold44. In this mode, the purged fuel vapors from the canister are combusted in the engine. The purging may be continued until the stored fuel vapor amount in the canister is below a threshold.

Controller212may comprise a portion of a control system214. Control system214is shown receiving information from a plurality of sensors216(various examples of which are described herein) and sending control signals to a plurality of actuators281(various examples of which are described herein). As one example, sensors216may include exhaust gas sensor237located upstream of the emission control device, temperature sensor233, fuel tank pressure sensor (FTPT)291, canister temperature sensor243, and integrated sensor202. Other sensors such as pressure, temperature, air/fuel ratio, and composition sensors may be coupled to various locations in the vehicle system200. As another example, the actuators may include fuel injector266, throttle262, fuel tank isolation valve253, pump292, and refueling lock245. The control system214may include a controller212. The controller may receive input data from the various sensors, process the input data, and trigger the actuators in response to the processed input data based on instructions or code programmed therein (e.g., programmed and stored on a memory of the controller) corresponding to one or more routines. An example control routine for determining the fuel composition and fuel pressure from integrated sensor202is described herein with regard toFIG. 6.

As described above, engine performance may be increased by adjusting engine operations in response to a determined composition and pressure of a fuel blend in a FFV. The fuel composition and fuel pressure may be estimated based on outputs (e.g., measurement signals) from an integrated sensor, such as the integrated sensor202ofFIG. 2. For example, the integrated sensor202may relay signals indicating capacitances generated by components of the sensor which are due to changing ethanol percentage and/or pressure of the fuel flowing through the integrated sensor. The capacitance is a ratio of a change in electric charge in a system to a corresponding change in an electric potential of the system and may be a function of a geometry of the integrated sensor and permittivity of the fuel flowing through the integrated sensor.

A cut-away side view300of the integrated sensor202is shown inFIG. 3. A set of reference axes301are provided, indicating a y-axis, x-axis, and z-axis. The integrated sensor202has a first section302that is arranged inline with the fuel line236so that fuel flowing through the fuel line also flows through the first section302of the integrated sensor202. At least a portion of the first section302is arranged entirely within an interior of a flow passage303of the sensor202. The first section302may have a central axis304that is also a central axis304of the fuel line236and includes a set of cylindrical capacitors comprising at least two concentrically arranged cylinders. The cylinders may be formed from ceramic or from other conductive materials. As shown inFIG. 3, the first section302includes a first cylinder308, shown as two planar plates in the cut-away side view300, that is aligned so that an inner passage310of the first cylinder308is centered along the central axis304and a central axis of the first cylinder308is coaxial with the central axis304. The first cylinder308may be surrounded by a second, larger (e.g., larger diameter) cylinder312, also shown as two planar plates in the cut-away side view300. Each of the first cylinder308(which may be referred to as an inner cylinder) and the second cylinder312(which may be referred to as an outer cylinder, where inner/outer are relative to the central axis304) are annular and have an inner diameter and outer diameter, which a thickness of each cylinder defined between respective inner and outer diameters. For example, the second cylinder312may have an outer diameter that is substantially equal to an outer diameter of the fuel line236and the flow passage303of the integrated sensor202, and an inner diameter that is substantially equal to an inner diameter of the fuel line236and the flow passage303. In other examples, however, the outer diameter and inner diameter of the second cylinder312may differ from the outer diameter and inner diameter of the fuel line236.

The first cylinder308may be enclosed by and spaced away from the second cylinder312so that an outer surface of the first cylinder308does not contact an inner surface of the second cylinder312. A position of the first cylinder308, centered within the second cylinder312, may be anchored by a rigid stem314, formed from a non-conductive material, connecting the first cylinder308to the second cylinder312. An outer flow passage316is formed between the outer surface of the first cylinder308and the inner surface of the second cylinder312. Fuel flowing through the fuel line236along a direction indicated by arrow318, which is parallel with the central axis304, may flow continuously through the inner passage310of the first cylinder308, as well as through the outer passage316. The fuel contacts both the inner and outer surfaces of the first cylinder308and the inner surface of the second cylinder312.

The second cylinder312may comprise a first shell320and a second shell322. In one example, the first shell320and the second shell322may be coupled together to form a continuous cylindrical surface (forming a complete cylinder), as shown in a first cross-section400of the integrated sensor202inFIG. 4. The first cross-section400is taken along A-A′ inFIG. 3. In other words, each the first shell320and the second shell322may form half of the second cylinder312. The edges408of the first shell320and the edges410of the second shell322may be connected by sections of a material of the fuel line236. In other examples, however, each of the first shell320and the second shell322may be less than half of the second cylinder312, the remainder of the cylinder formed by panels of a material forming the flow passage303. As an example, as shown in a second cross-section500of the integrated sensor202inFIG. 5, the first shell320and the second shell322may each comprise a quarter of the annular cross-section of the second cylinder312. The second cross-section500is also taken along A-A′ inFIG. 3. The first shell320and the second shell322may be connected by panels502, also formed from the material of the flow passage303. While the first shell320and second shell322are shown inFIGS. 3-5to be of similar dimensions, other examples of the integrated sensor202may include the second cylinder312with the first shell320smaller (e.g., narrow, thinner, and/or shorter) than the second shell322, or the first shell320larger (e.g., wider, thicker, and/or longer) than the second shell322.

The first shell320may be configured to bend or deflect when experiencing an outward (e.g., away from the central axis304) force from a pressure of the fuel flowing through the outer passage316. A curvature of the first shell320may increase slightly due to the pressure in an outwards direction, as indicated by arrows402shown inFIGS. 4 and 5. As the first shell320may be formed from ceramic and may be brittle and resistant to bending, the increase in curvature of the first shell may be relatively small. Alternatively, the first shell320may be adapted to shift radially outward in response to increased pressure in the outer passage316without varying the curvature while remaining connected, such as to the panels502inFIG. 5. The second shell322may respond similarly to changes in pressure of fuel flowing through the second cylinder312or may be configured to maintain a position of the second shell322regardless of pressure.

Returning toFIG. 3, the integrated sensor300may have a second section326, in addition to the first section302, that protrudes outwards, away from the central axis304, and is mostly positioned external to, e.g., outside of, the flow passage303and also outside of the flow path of the fuel line236. The second section326may comprise a parallel set of capacitance plates with first shell320of the second cylinder312forming one plate of the set of parallel capacitance plates and an external plate328, e.g., external to a path of fuel flow, forming a second plate of the set of parallel capacitance plates. The external plate328may also be formed from ceramic or some other type of conductive material. The external plate328may be positioned above the first shell320of the second cylinder312, with respect to the y-axis, and spaced away from the first shell320by a distance that may vary as the first shell320bends in response to an increase in pressure from fuel flowing through the cylindrical capacitance plates. Said another way, the external plate328is positioned outside of the first shell320, with respect to central axis304and an outer (e.g., external) wall of flow passage303. The external plate328may be configured to be static and, unlike the first shell320, does not bend in response to a change in the pressure of the fuel.

The external plate328may be configured to be a same length as the first shell320of the second cylinder312, as shown inFIG. 3, the length defined along the z-axis. In alternate embodiments, the length of the first shell320and external plate328may be different. In one example, the external plate328may be planar, as shown inFIG. 4and may have a width, defined along the x-axis, that is wider or narrower (as shown inFIG. 4) than an outer diameter404of the second cylinder312. In another example, as shown inFIG. 5, the external plate328may be curved, with a curvature matching the base, unbent curvature of the first shell320of the second cylinder312. The curved external plate328may also have a width that is narrower or wider than the outer diameter404of the second cylinder312. In addition, a thickness of the external plate328, defined along the y-axis, may be equal to, thinner, or thicker than the thickness of the first shell320of the second cylinder312.

The second section326of the integrated sensor202may also include an electronic device330, as shown inFIG. 3, to transmit electronic signals from the integrated sensor202to an engine control system, such as the controller212of engine control system214ofFIG. 2. The electronic device330may be formed from a conductive material, such as a metal or a composite, and comprise a first electrode332and a second electrode334, both the first and second electrodes332,334arranged perpendicular to the central axis304. The first electrode332and the second electrode334may be linked by a crossbar336that maintains positions of the first electrode332and the second electrode334. The crossbar336may be coaxial with the central axis304and spaced away from and above the external plate328.

The first electrode332of the electronic device330may extend down from a height above the external plate332, through the external plate328and through the first shell320of the second cylinder312to contact the outer surface of the first cylinder308. The external plate328and the first shell320may be adapted with apertures to accommodate insertion of the first electrode332. The portion of the first electrode332between the inner surface of the second cylinder312and the outer surface of the first cylinder308may be immersed in fuel. The first electrode332may alternatively extend along a side edge of the external plate328, e.g., side edge406shown inFIGS. 4-5, and along a side edge504shown inFIG. 5of the first shell320of the second cylinder312if the external plate328and the first shell320have widths that allow an adjacent positioning of the first electrode332while remaining aligned, along the y-axis, with the first cylinder308.

The second electrode334may be aligned parallel to and spaced away from the first electrode332by a distance less than a width (defined along the z-axis) of the crossbar336. The second electrode334may extend down from a height equal to a height of the first electrode332above the external plate332, either penetrating through the thickness of the external plate328or along the side edge406of the external plate328. Unlike the first electrode332, the second electrode may contact an outer surface of the first shell320of the second cylinder312but not extend through the first shell320and not contact the first cylinder308. The first and second electrodes332,334thereby transmit electronic signals from different sets of capacitance plates, the first electrode332relaying an electronic signal generated from a capacitance difference between the two cylinders of the set of cylindrical capacitors (e.g., first cylinder308and second cylinder312) and the second electrode334relaying an electronic signal generated from a capacitance difference between the two plates of the set of plate capacitors (e.g., external plate328and first shell320). In this way, the sensor202may output two electronic signals, with the first shell320of the second cylinder312being used by the sensor to produce each of the two electronic signals.

The integrated sensor202may be enclosed within an outer housing, as shown inFIG. 2to provide a barrier between the second section326of the integrated sensor202and other objects, such as other engine components. The aperture in the first shell320of the second cylinder312or one of the panels502(as shown inFIG. 5), through which the first electrode332may be inserted may be sealed so that fuel from the outer passage316of the integrated sensor202may not flow through the aperture into the encased second section326of the integrated sensor202.

In this way, an integrated sensor may be used to determine a fuel composition (e.g., percentage of ethanol in a gasoline/ethanol blend) and a fuel pressure of fuel flowing in a fuel line upstream of engine cylinders of an engine. The integrated sensor, comprising a set of cylindrical capacitors and a set of plate capacitors that share an element (e.g., the first shell320of the second cylinder312ofFIGS. 3-5), may be connected to an electrical storage device, such as energy storage device150ofFIG. 1. A potential may be applied to each of the set of cylindrical capacitors and the set of plate capacitors. A potential difference between a first cylinder and a second cylinder, the second cylinder surrounding the first cylinder and spaced away by a distance, may be measured and used to calculate a capacitance of the set of cylindrical capacitors. The capacitance may deviate by an amount, based on the potential difference, from a predetermined capacitance of the set of cylindrical capacitors. The capacitance change of the set of cylindrical capacitors may be converted into an electrical signal, such as a voltage, and sent to an engine controller by the electronic device where a permittivity of the fuel may be determined from the electrical signal and compared to permittivities of gasoline and ethanol. For example, a relative permittivity of gasoline may be 2 and a relative permittivity of ethanol may be 24.3. The calculated permittivity of the fuel may be a value between 2 and 24.3 and a percentage of ethanol in the mixture of gasoline and ethanol may be calculated based on the calculated permittivity value relative to the permittivities of gasoline and ethanol.

The fuel pressure may be determined from the set of plate capacitors. The set of plate capacitors may be spaced apart by a known distance when fuel is stationary or at a low flow rate through the set of cylindrical capacitors. However, when fuel flow increases through the set of cylindrical capacitors, a pressure from the fuel may exert an outwards, e.g., away from a central axis of the cylinders, force on the outermost cylinder of the set of cylindrical capacitors. The outermost cylinder may be adapted to bend outwards in response to the fuel pressure, decreasing the distance between the set of plate capacitors. The change in distance results in a change in capacitance of the set of plate capacitors. A calculation of the change in capacitance of the set of capacitance plates may include a potential difference between the plates as well as the permittivity of the fuel determined from the set of capacitance cylinders. The change in capacitance may be converted to a voltage that is conveyed to the controller. At the controller, a pressure of the fuel in the fuel line within the integrated sensor between an inner cylinder, e.g., the first cylinder308ofFIGS. 3-5, and a first shell of the outer cylinder, e.g., the first shell320of the second cylinder312ofFIGS. 3-5, may be determined to correspond to the change in capacitance.

The fuel pressure within the integrated sensor, e.g., P1inFIG. 3, may differ from a fuel pressure downstream of the integrated sensor, e.g., P2ofFIG. 2, between the integrated sensor and the engine, due to the presence of the inner cylinder within the fuel flow path. The interaction of the fuel with the inner cylinder may generate friction, increasing fuel pressure within the integrated sensor compared to the fuel pressure downstream of the integrated sensor. The downstream fuel pressure (upstream of the engine) may be estimated based on a calculated effect on the fuel pressure arising from friction between the fuel and the inner cylinder, providing a pressure of the fuel when the fuel reaches the engine. Fuel pressure and fuel composition of fuel injected into cylinders of the engine are thus measured by a single device (e.g., single electronic sensor) that is arranged proximal to the engine, thereby accounting for changes in fuel pressure along the fuel line. Calculations used to determine the fuel composition and fuel pressure will be elaborated further below in an example of a routine shown inFIG. 6.

An example of a routine600for determining a fuel composition and a fuel pressure of fuel from an integrated sensor arranged in a fuel line, between a fuel tank and an engine of a vehicle and proximal to the engine, is provided inFIG. 6. The integrated sensor may include a set of cylindrical capacitors and a set of plate capacitors with a common capacitor element shared between the two sets. An energy storage device may be coupled to the integrated sensor, supplying a voltage to the capacitors of the integrated sensor. The integrated sensor may also comprise an electronic device, such as the electronic device330ofFIG. 3, to relay signals from the integrated sensor to a controller, such as controller212ofFIG. 2. Instructions for carrying out method600and the rest of the methods included herein may be executed by the controller based on instructions stored on a memory of the controller and in conjunction with signals received from sensors of the engine system, such as the sensors described above with reference toFIG. 2. The controller may employ engine actuators of the engine system to adjust engine operation, according to the methods described below.

At602, the method includes flowing fuel from the fuel tank to the engine through the fuel line. The fuel may be gasoline, ethanol, or a blend of gasoline and ethanol. Flowing the fuel may include actuating a fuel pump, such as fuel pump221ofFIG. 2, to pump fuel out of the fuel tank towards the engine. As the integrated sensor is placed inline in the fuel line, the fuel also flows through the integrated sensor. A voltage may be applied to the integrated sensor at602by the energy storage device. The controller may command a connection of a circuit to provide a preset voltage to the integrated sensor from which baseline capacitances of the capacitors of the integrated sensor may be obtained based on stationary gasoline or ethanol in the integrated sensor as a dielectric material. A powertrain control module (PCM) may be a component of the controller, computing fuel injection timing based on signals received by the controller.

The fuel composition of the fuel flowing through the fuel line is determined at604.

Determining the fuel composition may comprise flowing fuel through the set of cylindrical capacitors at606. The set of cylindrical capacitors includes a first, smaller diameter cylinder aligned so that fuel flows along a length of the first cylinder through an inner passage and an outer passage of the first cylinder. The first cylinder is positioned inside a second cylinder of the set of cylindrical capacitors, as shown by the first cylinder308and second cylinder312shown inFIGS. 3-5 and 7, and centered within the second cylinder, arranged parallel with the first cylinder. A length of the first cylinder may be less than or equal to a length of the second cylinder. The outer passage of the first cylinder may also be an inner passage of the second cylinder. The second cylinder may be formed from a first shell and a second shell, the first shell arranged above the second shell. The first and second shell may be coupled directly to one another or coupled by panels, such as the panels502ofFIG. 5, arranged between the first and second shells. In this way, fuel may flow through an interior passage formed by an interior of the first cylinder and an outer passage formed between an outer wall of the first cylinder and an inner wall of the second cylinder (e.g., the outer passage formed in the space that separates the first and second cylinder).

An electronic signal indicating a change in capacitance may be generated by the electronic device when a composition of the fuel changes, e.g., the ethanol percentage decreases or increases. The electronic device may include a first electrode coupled to the set of cylindrical capacitors that relays a capacitance from the set of cylindrical capacitors to a signal conditioner at608. At610, the signal conditioner may convert the signal to a format readable by the controller, such as a voltage. Conditioning of the signal may be illustrated in a schematic diagram900inFIG. 9. The electronic device of the integrated sensor202may send a signal902via a first path904to a signal conditioner906. In one example, the signal may be analog and the signal conditioner906may be an amplifier that converts the analog signal to a digital signal908. The signal908may be sent to the controller212.

At612, the method includes calculating a permittivity of the fuel. Geometrical parameters of the integrated sensor such as, the radii of the first and second cylinders (e.g., r1and r2inFIG. 7), an area of a cross section of the set of cylindrical capacitors, volumes of the first and second cylinders, a distance between an inner surface of the second cylinder and outer surface of the first cylinder, and the lengths of the first and second cylinders, may be stored in a memory of the controller and used in the determination of the permittivity. As an example, a schematic diagram700of the integrated sensor202is shown inFIG. 7, depicting a cross-section of the first section of the integrated sensor202, taken from a plane perpendicular to the central axis of the first and second cylinders308,312on the left and a cross-section of the first and second cylinders308,312taken along the central axis is shown on the right. An electric field may be generated between the first cylinder308and the second cylinder312, as indicated by arrows702. From Gauss's Law, a Gaussian surface may be included to describe the electric potential difference using a difference between r1and r2, a stored electric charge q, and a length L of the first and second cylinders308,312, according to,

Δ⁢⁢V=qϵ⁢⁢2⁢π⁢⁢L⁢ln⁡(r2r1)(1)
where ϵ is a fuel permittivity of the fuel flowing through the integrated sensor.

A capacitance of the first section302of the integrated sensor202may be measured by the integrated sensor and related to the electric potential difference using the following relationship,

C=qΔ⁢⁢V(2)
The electronic device may be configured to measure capacitance and equations (1) and (2) may be combined to determined equation (3), as described below. The measured capacitance may be converted to a voltage output by the signal conditioner and sent to the controller. In one example, the voltage may correspond to the permittivity of the fuel. At the controller, the permittivity may be determined at612according to,

ϵ=C⁢⁢ln⁡(r2r1)2⁢π⁢⁢L(3)
Based on value of a relative permittivity of gasoline of ϵ≈2 and a relative permittivity of gasoline of ϵ≈24.3 stored in the controller's memory, the percentage of ethanol in the fuel blend flowing through the integrated sensor may be inferred at614of the method.

Inferring the percentage of ethanol in the fuel blend may include referring to a look-up table describing a relationship of the fuel permittivity to percentage of ethanol. For example, the controller may compare the calculated permittivity as an input to a list of ethanol/gasoline ratios resulting in specific permittivities. A corresponding ethanol percentage may be output based on the permittivity to estimate the fuel composition.

At618, the method includes determining a fuel pressure of the fuel line between the integrated sensor and the engine via the second section (e.g., the second section326of the integrated sensor202ofFIGS. 3-5, 8) of the integrated sensor comprising the set of plate capacitors. A first plate of the set of plate capacitors may be a first shell of the outer cylinder of the set of cylindrical capacitors and a second plate may be an external plate, with reference to the first shell320, the second cylinder312, and the external plate328ofFIGS. 3-5, and 8. The external plate may be curved to match a curvature of the first shell of the second cylinder or be planar. The external plate may be spaced away from the first shell of the second cylinder by a distance d, as shown inFIG. 8, and the distance when fuel flow through the integrated sensor is low or stationary may be stored in a memory of the controller as a base distance, as well as a capacitance of the second section of the integrated sensor calculated based on the distance.

When fuel flow is slow or stationary, the first shell of the second cylinder may be at the base distance where the first shell is not displaced relative to when fuel pressure rises. The base distance may correspond to a base pressure in the integrated sensor that is also stored in the controller's memory. The increase in fuel pressure may exert an outwards force on the first shell so that the first shell bends slightly outwards or is shifted slight outwards relative to a circumference of the second cylinder. The displacement of the first shell may change the distance between the external plate and the first shell of the second cylinder, thereby varying a potential difference and the capacitance of the set of plate capacitors. The capacitance of the set of plate capacitors may also depend on the fuel permittivity calculated based on the capacitance change at the set of cylindrical capacitors.

The electronic device of the integrated sensor may have a second electrode that is coupled to the set of plate capacitors. At620, the method includes measuring the capacitance (e.g., capacitance difference) between the set of plate capacitors. In this way, the second electrode may measure the change in capacitance across the set of plate capacitors, which occurs due to a change in pressure of fuel flowing through the sensor. The potential difference across the set of plate capacitors of the integrated sensor may be estimated based on Gauss's law and a Gaussian surface. The calculation is illustrated in a schematic diagram800, depicting the external plate328arranged above the first shell320and spaced away by a distance d. A magnetic field flow is formed between the external plate328and the first shell320, as indicated by arrows802. The potential difference, ΔV, may be determined according to,

Δ⁢⁢V=qϵ⁢⁢A⁢d(4)
where A is an area of the external plate328or the first shell320of the second cylinder. The measured capacitance may be related to the permittivity and distance between the plates by the following relationship,

C=ϵ⁢⁢Ad(5)
where the permittivity, ϵ, may be the fuel permittivity determined at612. The measured capacitance of the set of plate capacitors may be relayed to a signal conditions at622of the method.

The signal relaying a change in capacitance of the set of plate capacitors may be sent to the signal conditioner to convert the signal to a format readable by the controller. The electronic device of the integrated sensor may relay the capacitance as an electronic signal912along a second path910, shown in the schematic diagram900ofFIG. 9, to a signal conditioner912, similar to the signal conditioner906in the first path904. The signal conditioner914may also be an amplifier, converting an analog signal from the second section of the integrated composition-pressure sensor202to a digital output916of the method, resulting in a conversion of the capacitance signal to a voltage output that is sent to the controller at624.

A change in capacitance, relayed as a voltage, relative to the baseline capacity when fuel is at low flow or stationary within the integrated sensor may be proportional to a change in pressure. The controller may refer to a lookup table stored in the memory controller using the received voltage as an input and a corresponding pressure as an output. The fuel pressure in a flow passage of the integrated sensor is thereby determined at626.

The pressure value may represent a fuel pressure P1in the integrated sensor, as shown inFIG. 3. However, the positioning of the first cylinder within the path of fuel flow may affect the fuel pressure in the integrated sensor so that the pressure in the integrated sensor is higher than the fuel pressure in the fuel line between the integrated sensor and the engine. Thus, at628of the method, the fuel pressure downstream of the integrated sensor may be calculated based on an estimated ring duct friction and volume fuel flow speed of the first cylinder that may be obtained by a fuel delivery module. For example, the downstream pressure, P2, as shown inFIG. 3, may be determined according to,

P2=P1+[0.3164⁢(ReDh)-0.25]⁢ρ⁢⁢LV22⁢Dh(6)
where Re is Reynolds number, ρ is a density of the fuel, V is the flow speed of the fuel. The hydraulic diameter, Dh, in equation 6 may be calculated from inner and outer diameters of the first cylinder308and the second cylinder312, as shown in a schematic diagram1000ofFIG. 10depicting the first section302of the integrated sensor, based on,

At630, the method includes adjusting engine operating parameters, such as spark timing, fuel injection timing, valve timing, and/or exhaust gas recirculation, according to the detected changes in fuel composition and fuel pressure from the integrated sensor. For example, the controller may use the calculated pressure P2to infer a rail pressure and a fuel flow rate through fuel injectors of the engine, providing the PCM with information to adjust fuel injection accordingly. If fuel pressure is detected to increase, the duration of an injector pulse may be decreased to accommodate the higher flow rate through the fuel injectors. Conversely, a decrease in fuel pressure may result in a longer injector pulse.

In other examples, if the ethanol percentage increases, a spark timing may be advanced due to a higher activation energy of ethanol compared to gasoline and thus a longer ignition period for ethanol. An increase in ethanol content may also reduce a formation of gasoline combustion byproducts such as particulate matter and nitrous oxides and as a result, more gas may be recirculated to the engine intake instead of passing through an after treatment device such as the emission control device270ofFIG. 2. As another example, opening and closing of intake and exhaust valves at engine cylinders may be timed according to changes in fuel composition to accommodate different periods of time for ignition of the fuel.

In this way, a single integrated sensor, may be used to determine both a fuel composition and a fuel pressure of fuel. The integrated sensor may comprise a set of concentric cylindrical capacitors arranged inline with a fuel line and a set of plate capacitors positioned external to a path of fuel flow, with a common capacitor element shared between the two sets. The capacitance of the set of cylindrical capacitors may be used to estimate a permittivity of the fuel flow from which a percentage of ethanol in the fuel may be calculated. As fuel flows through the set of cylindrical capacitors, pressure from the fuel may displace a shell of an outer cylinder of the set of cylindrical capacitors that is also a plate of the set of plate capacitors. The displacement of the shell of the cylindrical capacitor results in a change in capacitance of the set of capacitor plates which may be translated to a fuel pressure in the integrated sensor. A pressure downstream of the integrated sensor may be calculated based on the fuel pressure in the integrated sensor corrected for an estimated amount of ring duct friction generated by fuel flow through the set of cylindrical capacitors. Thus, the fuel composition and fuel pressure may be determined directly from the integrated sensor and changes to fuel composition and/or pressure may be anticipated before combustion events with the altered composition and/or pressure occur. The integrated sensor may operate independently of other sensing devices and reduce response times to changes in fuel composition and/or fuel pressure, thereby increasing engine performance and decreasing a likelihood of events leading to engine degradation, such as engine knock. Furthermore, by incorporating dual sensing capabilities into one device instead of two, costs and weight of the engine system may be reduced.

The technical effect of configuring a fuel line with an integrated sensor including a set of cylindrical capacitors concentrically arranged and spaced apart from one another, where the set of cylindrical capacitors are adapted to receive a flow of fluid axially through each capacitor of the set of cylindrical capacitors and a set of plate capacitors spaced apart from one another, where a common capacitor element is shared between the set of cylindrical capacitors and set of plate capacitors, is that a number of measuring components (e.g., sensors) is reduced, thereby decreasing engine costs and reducing engine control complexity.

As one embodiment, an integrated fuel composition and pressure sensor includes a set of cylindrical capacitors concentrically arranged and spaced apart from one another, where the set of cylindrical capacitors are adapted to receive a flow of fluid axially through each capacitor of the set of cylindrical capacitors and a set of plate capacitors spaced apart from one another, where a common capacitor element is shared between the set of cylindrical capacitors and set of plate capacitors. In a first example of the sensor, the set of cylindrical capacitors includes an inner cylinder and an outer cylinder, the outer cylinder surrounding the inner cylinder, and wherein the common capacitor element is a portion of the outer cylinder. A second example of the sensor optionally includes the first example, and further includes wherein the set of plate capacitors includes a first plate and a second plate spaced apart from one another, where the first plate is the portion of the outer cylinder and the second plate is positioned outside of the first plate relative to a central axis of the inner cylinder. A third example of the sensor optionally includes one or more of the first and second examples, and further includes, wherein the first plate is adapted to bend and the second plate is static. A fourth example of the sensor optionally includes one or more of the first through third examples, and further includes, wherein a first electrode of an electronic device of the sensor is coupled to the set of cylindrical capacitors and a second electrode of the electronic device is coupled to the set of plate capacitors. A fifth example of the sensor optionally includes one or more of the first through fourth examples, and further includes, wherein the first electrode is adapted to measure of first change in capacitance between the set of cylindrical capacitors that is indicative of a change in fuel composition of fuel flowing through the sensor. A sixth example of the sensor optionally includes one or more of the first through fifth examples, and further includes, wherein the second electrode is adapted to output a second change in capacitance between the set of plate capacitors that is indicative of a change in pressure of fuel flowing through the sensor. A seventh example of the sensor optionally includes one or more of the first through sixth examples, and further includes, wherein the second plate of the set of plate capacitors is arranged parallel to the first plate and parallel to the set of cylindrical capacitors.

As another embodiment, a method includes flowing a fuel through a fuel line and through a sensor arranged in the fuel line, estimating a fuel composition of the fuel from a first signal generated from a change in capacitance between a set of cylindrical capacitors of the sensor which are arranged concentrically with one another and positioned in a flow path of the fuel, and estimating a pressure of the fuel from a second signal generated from a change in capacitance between a set of plate capacitors of the sensor and based on the first signal. In a first example of the method, estimating the fuel composition includes, via a controller adapted to receive the first signal and the second signal from the sensor, calculating a permittivity of the fuel based on the first signal and further comprising, estimating a percentage of ethanol in the fuel from the calculated permittivity. A second example of the method optionally includes the first example, and further includes estimating the pressure of the fuel includes, via the controller, calculating the pressure of fuel based on the second signal and the calculated permittivity, where the change in capacitance between the set of plate capacitors is generated due to a change in distance between plates of the set of plate capacitors. A third example of the method optionally includes one or more of the first and second examples, and further includes, correcting the estimated pressure for an effect of ring duct friction based on a fuel speed and length of the set of the cylindrical capacitors and a density of the fuel to determine a pressure of the fuel in the fuel line, downstream of the sensor and upstream of an engine. A fourth example of the method optionally includes one or more of the first through third examples, and further includes, wherein the set of cylindrical capacitors and the set of plate capacitors share a common element, where the common element is a portion of an outer cylinder that surrounds an inner cylinder of the set of cylindrical capacitors. A fifth example of the method optionally includes one or more of the first through fourth examples, and further includes, wherein flowing fuel through the sensor includes flowing fuel through an interior of the inner cylinder and through a space that separates the inner cylinder and the outer cylinder.

As another embodiment, a fuel system includes a fuel line coupling a fuel tank to an engine, and an integrated sensing device arranged in the fuel line, in line with a path of fuel flow through the fuel line, the device including, a set of cylindrical capacitors formed by concentrically arranged, inner and outer cylindrical capacitors, and a set of plate capacitors formed by a portion of the outer cylindrical capacitor and a static plate arranged outside of the path of fuel flow. In a first example of the fuel system, the inner cylindrical capacitor is arranged entirely within the path of fuel flow. A second example of the fuel system optionally includes the first example, and further includes, wherein, when fuel flows through the fuel line and through the integrated sensing device, fuel flows through an inner passage of the inner cylindrical capacitor formed from an interior of the inner cylindrical capacitor and through an outer passage formed between an outer surface of the inner cylindrical capacitor and an inner surface of the outer cylindrical capacitor. A third example of the fuel system optionally includes one or more of the first and second examples, and further includes, wherein the outer cylindrical capacitor has a first shell and a second shell, each of the first shell and second shell forming a portion of a circumference of the outer cylindrical capacitor. A fourth example of the fuel system optionally includes one or more of the first through third examples, and further includes, wherein the first shell is adapted to outwardly displace, in a direction away from a central axis of the outer cylindrical capacitor, when fuel pressure inside the outer cylindrical capacitor increases. A fifth example of the fuel system optionally includes one or more of the first through fourth examples, and further includes, wherein the first shell of the outer cylindrical capacitor is the portion of the outer cylindrical capacitor that forms a movable plate of the set of plate capacitors and wherein the outward displacement of the first shell changes a distance between the set of plate capacitors.

In another representation, a method includes upon flowing fuel through a device via a fuel line, applying a voltage to the device and determining a composition and pressure of the fuel based on signals relayed by the device. In a first example of the method, flowing fuel through the device includes flowing fuel through inner passages of a set of concentric cylindrical capacitors. A second example of the method optionally includes the first method, and further includes wherein a potential difference is generated between the set of concentric cylindrical capacitors. A third example of the method optionally includes one or more of the first and second examples, and further includes, wherein a capacitance of the set of the concentric cylindrical capacitors is calculated based on the potential difference. A fourth example of the method optionally includes one or more of the first through third examples, and further includes, wherein a permittivity of the fuel flowing through the device and fuel line is determined based on the capacitance of the set of concentric cylindrical capacitors, a length of the set of concentric cylindrical capacitors, and radii of each cylinder of the set of concentric cylindrical capacitors. A fifth example of the method optionally includes one or more of the first through fourth examples, and further includes, wherein the permittivity of the fuel is converted to a fuel composition by a signal converter and relayed to an engine controller. A sixth example of the method optionally includes one or more of the first through fifth examples, and further includes, wherein flowing fuel through the device exerts an outward force on a first shell of an outer cylinder of the set of concentric cylindrical capacitors that is also a first plate of a set of capacitance plates of the device and an external plate is a second plate of the set of capacitance plates. A seventh example of the method optionally includes one or more of the first through sixth examples, and further includes, wherein the outward force on the first plate changes a distance between the first plate and the second plate and also changes a capacitance of the set of capacitance plates. An eighth example of the method optionally includes one or more of the first through seventh examples, and further includes, wherein a capacitance of the set of capacitance plates is calculated based on the distance between the first plate and the second plate, a fuel permittivity determined from the set of concentric cylindrical capacitors, and a surface area of the second plate. A ninth example of the method optionally includes one or more of the first through eighth examples, and further includes, wherein the capacitance of the set of capacitance plates is converted to a fuel pressure by a signal converter and relayed to an engine controller. A tenth example of the method optionally includes one or more of the first through ninth examples, and further includes, wherein the fuel pressure is adjusted to reflect a fuel pressure downstream of the device by calculating an effect of ring duct friction.