Patent Description:
Aircraft engines may be provided with various flowmeters to measure the flow rate of the various fluids used in the engine. Various types of flowmeters exist, such as flowmeters based on hydrodynamic methods, flowmeters with continuously moving bodies, and flowmeters based on various physical phenomena. However, flowmeters based on certain physical phenomena may be limited to measuring the flow rate of liquids.

Using alternative fuels such as hydrogen in gas turbine engines can pose certain design/engineering challenges, which are not encountered when jet fuels are used. For example, certain alternative fuels, such as hydrogen, can be gaseous at atmospheric conditions and thus may need to be stored and/or conveyed in gaseous form. As such, any on-board flowmeters for measuring the mass flow of the aircraft's fuel must be capable of measuring the flow rate of gaseous fluids. As such, improvements are desired.

<CIT> discloses a prior art fluidic detection system for the magnetic-electrical measurement of a fluid sample, wherein the system comprises at least one sample module, one magnetic field sensor, and one magnet, which are spaced apart from one another. The sample module has at least one channel which is designed for transporting a fluid sample along a flow direction. The magnet generates a magnetic field in a measurement and excitation region of the channel. The detection region of the magnetic field sensor corresponds to the measurement and excitation region of the channel. When transporting the fluid sample in the measurement and excitation region of the channel, the magnetic field is modified by the fluid sample to be examined, wherein the magnetic field sensor detects the modified magnetic field.

According to a first aspect of the present invention, there is provided a flowmeter for gaseous fluid as set forth in claim <NUM>.

In an embodiment according to any of the previous embodiments, the flowmeter further comprises an ionizer for ionizing the gaseous fluid to produce the ionized flow.

In an embodiment according to any of the previous embodiments, the ionizer is configured for stripping away electrons from gas molecules in the gaseous fluid and the ionized flow is positively charged.

In an embodiment according to any of the previous embodiments, the ionizer is configured for adding electrons to gas molecules in the gaseous fluid and the ionized flow is negatively charged.

In an embodiment according to any of the previous embodiments, the electromagnetic sensor comprises any one of a Hall effect sensor, an anisotropic magneto-resistive sensor, a giant magnetoresistance sensor, and a transformer.

In an embodiment according to any of the previous embodiments, the flowmeter further comprises a flow divider upstream from the conduit for separating the gaseous fluid into a first stream and a second stream, wherein the first stream flows through the conduit and the second stream flows externally to the conduit, and a flow combiner downstream from the conduit for recombining the first stream and the second stream together.

In an embodiment according to any of the previous embodiments, the flowmeter further comprises a flow modulator upstream from the electromagnetic sensor to pulse the gaseous fluid and produce an alternating current in the conduit.

In an embodiment according to any of the previous embodiments, the flowmeter further comprises a measuring circuit coupled to the electromagnetic sensor for receipt of the signal generated by the electromagnetic sensor and conversion of the signal to a mass flow of the gaseous fluid.

According to a further aspect of the present invention, there is provided a method for measuring mass flow of a gaseous fluid as set forth in claim <NUM>.

In an embodiment according to any of the previous embodiments, the method further comprises ionizing the gaseous fluid to produce the ionized flow.

In an embodiment according to any of the previous embodiments, the method further comprises separating the gaseous fluid into a first stream and a second stream, wherein the first stream flows through the conduit and the second stream flows externally to the conduit, and recombining the first stream and the second stream together after the measuring of the magnetic field.

In an embodiment according to any of the previous embodiments, the method further comprises pulsing the gaseous fluid to produce an alternating current in the conduit.

Features of the systems, devices and methods described herein may be used in various combinations, in accordance with the embodiments described herein.

The present disclosure is directed to measuring the mass flow of gaseous fluids, for example as used in a hydrogen fuel cell. The properties of gaseous fluids differ from the properties of liquids. For example, gaseous fluids are compressible whereas liquids are not. The compressibility of gaseous fluids makes it difficult to measure its mass flow using traditional flowmeters suitable for liquids. Therefore, there are described herein methods, systems and devices for measuring gaseous fluids.

In some embodiments, the gaseous fluid is gaseous fuel used by an engine. As used herein, "gaseous fuel" refers to fuels that exist in the gaseous state at room temperature. Examples of gaseous fuels are hydrogen gas, natural gas, butane and propane. <FIG> illustrates an example engine <NUM> of a type provided for use in subsonic flight, generally comprising in serial flow communication a fan <NUM> through which ambient air is propelled, a compressor section <NUM> for pressurizing the air, a combustor <NUM> in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and a turbine section <NUM> for extracting energy from the combustion gases. A longitudinal main engine axis <NUM> extends through the center of the engine <NUM>. Although a turbofan engine <NUM> is shown in <FIG> for exemplary purposes, it is to be understood that the engine <NUM> as described herein may alternately be another type of gas turbine engine, including for example turboshafts, turboprops, and turbojets, or another type of combustion engine, such as a Wankel engine or a reciprocating engine. As such, the expression "combustor" should be understood to include any chamber within an engine in which combustion can occur. In some embodiments, the engine <NUM> forms part of an aircraft. In some embodiments, the engine <NUM> forms part of a vehicle for land or marine applications. In some embodiments, the engine <NUM> is used in an industrial setting, for example for power generation or as an auxiliary power unit.

Engine <NUM> may be powered in part or entirely by gaseous fuel. Engine <NUM> may also be a hybrid or bi-fuel propulsion system, in which two different fuel types (e.g. an alternative fuel such as hydrogen, as well as a traditional jet fuel) may be used.

Control of the operation of the engine <NUM> can be effected by one or more control systems, for example a controller <NUM>, which is communicatively coupled to the engine <NUM>. The operation of the engine <NUM> can be controlled by way of one or more actuators, mechanical linkages, hydraulic systems, and the like. The controller <NUM> can be coupled to the actuators, mechanical linkages, hydraulic systems, and the like, in any suitable fashion for effecting control of the engine <NUM>. The controller <NUM> can modulate the position and orientation of variable geometry mechanisms within the engine <NUM>, the bleed level of the engine <NUM>, and fuel flow, based on predetermined schedules or algorithms. Note that the controller <NUM> can be implemented as part of a full-authority digital engine controls (FADEC) or other similar device, including electronic engine control (EEC), engine control unit (ECU), electronic propeller control, propeller control unit, and the like.

Referring to <FIG>, there is shown an example of a flowmeter <NUM> for measuring the mass flow rate of a gaseous fluid. The flowmeter <NUM> measures gas flow in a manner similar to the external measurement of electric current, where charged particles (i.e. electrons) move in a fixed space and result in a magnetic field surrounding a conductor. This principle is reproduced in gas particles by the flowmeter <NUM>, whereby a charged gas flows through a non-electrically conductive conduit <NUM> and an electromagnetic sensor <NUM> measures a resulting magnetic field. In some embodiments, and as shown in <FIG>, flowmeter <NUM> is configured for measuring the flow rate of gaseous fuel used in engine <NUM>. In cases where flowmeter <NUM> measures the mass flow rate of the engine's fuel, the flowmeter <NUM> may be positioned upstream of combustor <NUM>. Alternatively, the flowmeter <NUM> may be positioned elsewhere in the engine <NUM>.

Ionized gas flowing through the conduit <NUM> made of non-electrically conductive material generates a magnetic field about the conduit <NUM>. The non-electrically conductive material may be, for example, an insulative material or a non-insulative material that is non-electrically conductive such as a semi-conductor material. In some embodiments, the gaseous fluid is provided to a gas ionizer <NUM> from a gas source <NUM>. In some embodiments, the gas source <NUM> may be the engine's primary fuel tank. In other embodiments, the gas source <NUM> may be another source for the gas whose flow is to be measured. In use, gas particles from the gas source <NUM> are sent to the gas ionizer <NUM> to impart a positive or negative charge to the gas, producing a charged gas (i.e. a plasma). If the gaseous fluid is already ionized, the gas ionizer <NUM> may be omitted. The positively or negatively charged gas is then directed through the conduit <NUM>, where the electromagnetic sensor <NUM> is arranged to measure the magnetic field generated about the conduit by the passage of the ionized flow and to generate a signal, such as voltage or current, proportional to the magnetic field. The generated signal may then be used to determine the mass flow of the gas via a measuring circuit <NUM>. In some cases, the measuring circuit <NUM> may be omitted, whereby the output of the flow meter is the signal generated by the electromagnetic sensor <NUM>. The charged gas is sent to a de-ionizer <NUM> for neutralization after the magnetic field has been measured.

Various types of gas ionizers <NUM> may be contemplated to ionize the gas molecules, utilizing methods such as electric discharge, laser ionization, or the application of very high electric or magnetic fields. In some embodiments, electrons may be stripped away from the gas molecules, resulting in positively charged ions. In other embodiments, electrons may be added to the gas molecules, resulting in positively charged ions. In either case, energy must be provided to either add or remove one or more electron from each gas particle, resulting in electrically charged gas particles, also referred to as gas ions or plasma. Power is supplied to the gas ionizer <NUM> in order to ionize the gas particle, for instance from a battery or other power source within engine <NUM>. The power source may be dedicated to the flowmeter <NUM> or shared, for example a battery from a hybrid engine. The quantity of power required may depend on factors such as the type and quantity of gas being ionized.

Various types of electromagnetic sensors <NUM> may be contemplated. For instance, the electromagnetic sensor <NUM> may be a Hall effect sensor, an anisotropic magneto-resistive (AMR) sensor, a giant magnetoresistance (GMR) sensor, or a transformer. In embodiments where the electromagnetic sensor <NUM> is suitable for measuring an alternating current (AC), such as a transformer, the flowmeter <NUM> may further include a flow modulator <NUM> upstream from the electromagnetic sensor <NUM> to pulse the gaseous fluid and produce the alternating current in the conduit <NUM>. Other devices capable of measuring the magnitude of the magnetic field generated by the flow of ions through the conduit <NUM> and, in response, produce a proportional signal may be contemplated as well. To prevent the ions from prematurely recombining with electrons in the conduit <NUM> before a proper reading is taken, the conduit <NUM> is made of a non-electrically conductive material.

The gas de-ionizer <NUM>, also referred to as a gas neutralizer, is operable to de-ionizer or neutralize the ionized gas after it has passed through the conduit <NUM> and the generated magnetic field is measured. Various means for neutralizing the gas, i.e. adding electrons to the positively charged plasma or removing electrons from the negatively charged plasma, may be contemplated.

The measurement circuit <NUM> is coupled to the electromagnetic sensor for receipt of the voltage generated by electromagnetic sensor <NUM> and conversion of this voltage to a mass flow of the ionized gaseous fluid flowing through the conduit <NUM>. In some cases, the mass flow rate of the gas is directly proportional to the outputted signal from the electromagnetic sensor <NUM>, which itself is proportional to the magnitude of the magnetic field generated by the flow of ions through the conduit <NUM>. In other cases, various scale factors or ratios may be used to calculate the mass flow of the gas from the outputted signal. In some embodiments, the signal is converted to mass flow using: <MAT>.

Where Y is the mass flow, X is the measured parameter (in millivolts, volts, amps, milliamps, etc), M is a scale factor and B is an offset. Any electronic component suitable for converting a measured signal to mass flow may be used, such as but not limited to a microcontroller, a field programmable gate array (FPGA), a complex programmable logic device (CPLD), and a field programmable analog array (FPAA). In some embodiments, the measuring circuit <NUM> is integrated into the engine controller <NUM>. In some embodiments, the engine controller <NUM> may be configured to control the flow of the gaseous fuel based on the mass flow as measured by the flowmeter <NUM>.

Referring to <FIG>, in an exemplary embodiment, gaseous hydrogen molecules <NUM> are directed through conduit <NUM> of flowmeter <NUM>. Each hydrogen molecule <NUM>, commonly referred to as H<NUM>, emanating from the gas source <NUM> includes two positively charged protons <NUM> and two negatively charged electrons <NUM>. For illustrative purposes, the size of each hydrogen molecule <NUM> relative to the conduit <NUM> is highly exaggerated. As the hydrogen molecules <NUM> flow through the conduit <NUM>, power is supplied to the gas ionizer <NUM> and an electron <NUM> is stripped or removed from each hydrogen molecule <NUM>, resulting in a plurality of positively charged hydrogen ions <NUM>, also referred to as dihydrogen cations or hydrogen molecular ions (H<NUM>+). Each hydrogen ion <NUM> includes two protons <NUM> and a single electron <NUM>, resulting in an overall positive charge. The flow of hydrogen ions <NUM> through the conduit <NUM> creates a magnetic field <NUM> in the area around the conduit <NUM>, which can be detected and measured by the electromagnetic sensor <NUM> (illustratively a Hall effect sensor).

Each molecule requires a certain amount of energy (i.e. ionization energy) to add or remove an electron from it. For example, the measured ionization energy of H<NUM> is <NUM> kJ/mol. As such, the gas ionizer <NUM> must be set to a high enough level to saturate (i.e. add or strip electron(s) from each molecule) at the highest possible flow rate of the gas through conduit <NUM> to ensure that all of the gas molecules have been ionized. This will ensure the accuracy of the flowmeter <NUM>, as unionized gas molecules will not generate a magnetic field <NUM> and thus not be accounted for by the electromagnetic sensor <NUM>. As such, the power level applied to the gas ionizer <NUM> may be adjusted, for instance, based on the type of fluid and the expected flow rate.

In some embodiments, and as shown in <FIG>, the flowmeter <NUM> may be operable to measure a diverted portion of the gas by separating the gas flow into a main gas path <NUM> and a secondary gas path <NUM>. For instance, if a substantial amount of power is needed to ionize an entire flow of gas in order to measure its mass flow via flowmeter <NUM>, a portion of the gas glow may be separated and recombined for the purpose of flow measurement. A calculated ratio between the diverted gas flow and the undiverted gas flow may be used to estimate the mass flow of the entire gas flow.

As shown in <FIG>, a flow divider <NUM> may split the gas into two streams: a first stream towards the flowmeter <NUM> via the secondary gas path <NUM> and a second stream continuing through the main gas path <NUM>. The quantity of gas diverted through the secondary gas path <NUM> relative to the quantity of gas remaining in the main gas path <NUM> is used to estimate the mass flow of the entire gas flow. For instance, the flow divider <NUM> may include a pair of orifices, a first orifice with a larger surface area diverting gas towards the main gas path <NUM> and a second orifice with a smaller surface area diverting gas towards the flowmeter <NUM> via the secondary gas path <NUM>. Thus, a ratio may be determined via the relative areas of the orifices. Similarly, if the orifices are circular, a ratio may be determined based on their relative diameters. The mass flow determined via the measuring circuit <NUM> may take into account the ratio of gas in the main gas path <NUM> vs gas in the secondary gas path <NUM> to calculate the mass flow of the entire flow of gas. Once the ionized gas flow is measured and optionally neutralized via gas de-ionizer <NUM>, it may be re-combined with the flow of the main gas path <NUM> via flow combiner <NUM>.

Referring to <FIG>, there is shown an exemplary method <NUM> for measuring mass flow of a gaseous fluid. Such method <NUM> may be performed to measure mass flow of gaseous fuel, such as for an engine, or to measure mass flow of any other gaseous fluid.

At step <NUM>, the gaseous fluid is ionized to produce an ionized flow. In some embodiments, the gaseous fluid may be gaseous hydrogen (H<NUM>) acting as a fuel source for engine <NUM>, and the gaseous fluid may be ionized by gas ionizer <NUM>. Ionizing the gaseous fluid may be performed by adding or removing electrons to obtain a charged or ionized flow of gaseous fluid. If the flow is already ionized, step <NUM> may be omitted.

At step <NUM>, the ionized flow of gaseous fluid is received in a non-electrically conductive conduit <NUM>. Any non-electrically conductive material may be used for the conduit <NUM>, such as fiberglass, rubber, plastics, and the like. It will be understood that the gaseous fluid may be ionized prior to receipt inside the conduit, concurrently with receipt into the conduit, or after receipt into the conduit. As such, the order of steps <NUM> and <NUM> is interchangeable. In some embodiments, only a portion of the conduit <NUM> is made of non-electrically conductive material and receipt therein comprises receipt in the portion of the conduit made of non-electrically conductive material.

At step <NUM>, a magnetic field <NUM> generated about the non-electrically conductive conduit <NUM> by the ionized flow is measured by the electromagnetic sensor <NUM>, which may be for instance, one or more of a Hall effect sensor, an anisotropic magneto-resistive (AMR) sensor, a giant magnetoresistance (GMR) sensor, a transformer, induction coils, a magnetoimpedance (MI) sensor, a fluxgate sensor, an optical magnet sensor, an atomic magnetometer, and a superconducting quantum interference device (SQUID). Any sensor capable of detecting changes and disturbances in a magnetic field like flux, strength and direction may be used. In some embodiments, a combination of sensors of same or different types are used. A signal, such as voltage or current, proportional to the magnetic field is then generated by the electromagnetic sensor <NUM>.

At step <NUM>, the signal generated by the electromagnetic sensor <NUM> proportional to the magnetic field is converted to the mass flow of the gaseous fluid by the measuring circuit <NUM>. In some embodiments, the measuring circuit <NUM> forms part of the engine controller <NUM>. In some embodiments, the measuring circuit is external to the engine controller <NUM> and communicatively coupled thereto.

At step <NUM>, the ionized flow is neutralized by gas de-ionizer <NUM>, by either adding or removing electron(s) to the charged gas.

In some embodiments, the method <NUM> further includes separating the gaseous fluid into a first stream and a second stream. The first stream flows through the conduit <NUM> to have its mass flow measured by flowmeter <NUM>, and the second stream flows externally to the conduit <NUM>. The first stream and the second stream are then recombined after the first stream's mass flow is measured. The ratio of flow in the first stream and the second stream is used to determine the mass flow of the overall flow of gaseous fluid.

It can be appreciated from the foregoing that in at least some embodiments the flowmeter <NUM> is operable to measure the flow rate of a gaseous fluid without the use of dynamic components that are susceptible to the harsh realities that aerospace engines are subjected to, such as vibrations and severe thermal variations. In addition, in at least some embodiments, the flowmeter <NUM> described herein does not require any components positioned in the flow of the gaseous fluid itself which may impact the momentum of the flow and delay the response times. For example, the ionizer <NUM>, de-ionizer <NUM>, and electromagnetic sensor <NUM> may all be provided externally to the conduit <NUM>.

In some embodiments, the measuring circuit <NUM> is implemented in a computing device <NUM>, an example of which is illustrated in <FIG>. For simplicity only one computing device <NUM> is shown but the measuring circuit <NUM> may include more computing devices <NUM> operable to exchange data. The computing devices <NUM> may be the same or different types of devices. The controller <NUM> may be implemented with one or more computing devices <NUM>.

The processing unit <NUM> may comprise any suitable devices configured to convert a given parameter such as voltage or current into mass flow.

The memory <NUM> may include a suitable combination of any type of computer memory that is located either internally or externally to the device, for example random-access memory (RAM), read-only memory (ROM), compact disc read-only memory (CDROM), electro-optical memory, magnetooptical memory, erasable programmable read-only memory (EPROM), and electrically-erasable programmable read-only memory (EEPROM), Ferroelectric RAM (FRAM) or the like.

Computer-executable instructions <NUM> may be in many forms, including program modules, executed by one or more computers or other devices.

Claim 1:
A flowmeter (<NUM>) for gaseous fluid comprising :
a conduit (<NUM>) composed of non-electrically conductive material for passage of an ionized flow of the gaseous fluid therethrough;
an electromagnetic sensor (<NUM>) arranged to measure a magnetic field generated about the conduit (<NUM>) by the passage of the ionized flow and generate a signal proportional to the magnetic field; and characterized by
a de-ionizer (<NUM>) for neutralizing the ionized flow downstream from the electromagnetic sensor (<NUM>).