Dual pump/dual bypass fuel pumping system

An example dual pump/dual bypass fuel pumping assembly may include a dual bypass valve including a first inlet port, a second inlet port, and a movable spool arranged to modulate fuel flow from the first inlet port to a first bypass port and a first discharge port and arranged to modulate fuel flow from the second inlet port to a second bypass port and a second discharge port based on a position of the movable spool; a first pump arranged to supply fuel to the first inlet port; a second pump arranged to supply fuel to the second inlet port; a supply header arranged to supply fuel to the first pump and the second pump; a bypass header fluidicly coupled to the first bypass port, the second bypass port, and the supply header; and/or a discharge header fluidicly coupled to the first discharge port and the second discharge port.

BACKGROUND

The subject matter disclosed herein relates generally to fuel systems for internal combustion engines, and, more specifically, to fuel pumping systems for gas turbine engines, such as aircraft engines.

Fuel pumping systems on gas turbine engines may utilize a single positive displacement pump operating in conjunction with a bypassing control in which excess fuel flow is recirculated to the pump inlet. Under some conditions (e.g., cruise), the amount of fuel being pumped may far exceed the amount of fuel required, and a majority of the pumped flow may be recirculated.

The problem: Continual pumping to required pressure followed by recirculation of flow to the pump inlet at low pressure may result in excess fuel pumping horsepower consumption and may reduce efficiency in terms of engine specific fuel consumption (SFC) and heat imparted to the fuel system.

BRIEF DESCRIPTION OF THE INVENTION

At least one solution for the above-mentioned problem(s) is provided by the present disclosure to include example embodiments, provided for illustrative teaching and not meant to be limiting.

An example dual pump/dual bypass fuel pumping assembly according to at least some aspects of the present disclosure may include a dual bypass valve including a first inlet port selectively connectable to a first bypass port and a first discharge port, a second inlet port selectively connectable to a second bypass port and a second discharge port, and a movable spool arranged to modulate fuel flow from the first inlet port to the first bypass port and the first discharge port and arranged to modulate fuel flow from the second inlet port to the second bypass port and the second discharge port based at least in part on a position of the movable spool; a first pump arranged to supply fuel to the first inlet port; a second pump arranged to supply fuel to the second inlet port; a supply header arranged to supply fuel to the first pump and the second pump; a bypass header fluidically coupled to the first bypass port, the second bypass port, and the supply header; and a discharge header fluidically coupled to the first discharge port and the second discharge port. In a first position, the movable spool may modulate fuel flow from the first inlet port between the first discharge port and the first bypass port and may direct substantially all fuel flow from the second inlet port to the second bypass port. In a second position, the movable spool may direct substantially all fuel flow from the first inlet port to the first discharge port and may modulate fuel flow from the second inlet port between the second discharge port and the second bypass port.

An example fuel supply system according to at least some aspects of the present disclosure may include a dual pump/dual bypass fuel pumping assembly including a dual bypass valve including a first inlet port selectively connectable to a first bypass port and a first discharge port, a second inlet port selectively connectable to a second bypass port and a second discharge port, and a movable spool arranged to modulate fuel flow from the first inlet port to the first bypass port and the first discharge port and arranged to modulate fuel flow from the second inlet port to the second bypass port and the second discharge port based at least in part on a position of the movable spool, a first positive displacement pump arranged to supply fuel to the first inlet port, a second positive displacement pump arranged to supply fuel to the second inlet port, a supply header arranged to supply fuel to the first pump and the second pump, a bypass header fluidically coupled to the first bypass port, the second bypass port, and the supply header, a discharge header fluidically coupled to the first discharge port and the second discharge port; and a control valve assembly fluidically coupled to the dual bypass valve to modulate fuel pressure in the discharge header, the control valve assembly including an electrohydraulic servo valve operatively coupled to an electronic engine controller, and a servo valve operatively coupled to direct pressurized fuel to both ends of the moveable spool of the dual bypass valve to position the movable spool as directed by the electronic engine controller, the servo valve being operatively coupled to be actuated by pressurized fuel received from the electrohydraulic servo valve.

An example fuel supply system according to at least some aspects of the present disclosure may include a dual pump/dual bypass fuel pumping assembly including a dual bypass valve including a first inlet port selectively connectable to a first bypass port and a first discharge port, a second inlet port selectively connectable to a second bypass port and a second discharge port, and a movable spool arranged to modulate fuel flow from the first inlet port to the first bypass port and the first discharge port and arranged to modulate fuel flow from the second inlet port to the second bypass port and the second discharge port based at least in part on a position of the spool, a first positive displacement pump arranged to supply fuel to the first inlet port, a second positive displacement pump arranged to supply fuel to the second inlet port, a supply header arranged to supply fuel to the first pump and the second pump, a bypass header fluidically coupled to the first bypass port, the second bypass port, and the supply header, a discharge header fluidically coupled to the first discharge port and the second discharge port; and/or a control valve assembly fluidically coupled to the dual bypass valve. The control valve assembly may include a metering valve operatively disposed in the discharge header, the metering valve modulating fuel flow through the discharge header, an electrohydraulic servo valve operatively coupled to position the metering valve as directed by an electronic engine controller, and/or a spool valve operatively coupled to the metering valve and the dual bypass valve to direct pressurized fuel to both ends of the moveable spool of the dual bypass valve to position the movable spool to maintain a desired pressure differential across the metering valve.

DETAILED DESCRIPTION

The present disclosure includes, inter alia, fuel systems for internal combustion engines, and more specifically fuel pumping systems for gas turbine engines, such as aircraft engines. Generally, some example embodiments according to at least some aspects of the present disclosure may be configured to limit the amount of fuel pumped to metering system required pressure at some or all operating conditions.

The present disclosure contemplates that some aircraft engine fuel systems utilize bypassing controls operating with a positive displacement pump sized for maximum flow demand, which may result in excess flow, wasted horsepower, and/or excessive heat generation at cruise conditions (e.g., 10-15% of maximum power).

As described in detail below, some example embodiments according to at least some aspects of the present disclosure may include a fuel system utilizing two (or more) fuel pumps operating in conjunction with a bypass valve assembly (e.g., a dual bypass valve assembly). Some example dual pump/dual bypass configurations may allow a fuel system to operate at reduced drive horsepower at some operating conditions, which may contribute to improved engine efficiency (e.g., specific fuel consumption for aircraft engines) and/or reduced heat addition to the fuel due to pumping and recirculation. In some example embodiments, reduced heat addition to the fuel may allow reduced operating temperatures for systems and components cooled by the fuel, such as lubricating oil.

Some example embodiments according to at least some aspects of the present disclosure may include a first pump and a second pump. For example, the first pump may include a relatively smaller, positive displacement fuel pump (e.g., relatively lower pumping capacity) and/or the second pump may include a relatively larger, positive displacement fuel pump (e.g., relatively higher pumping capacity). The first pump may be sized to supply the required fuel flow for a particular operating condition. The second pump, which may supplement the fuel flow from the first pump, may be sized such that the combined flow from both the first pump and the second pump provides the maximum expected demand flow. The fuel flow from the pumps may be delivered to a servo actuated dual bypassing valve assembly, which may be arranged to bypass fuel flow in excess of engine need back to the inlet of the pumps.

In some example embodiments according to at least some aspects of the present disclosure, at cruise conditions, the first pump may supply substantially all of the fuel consumed by the engine, while the second pump may be in substantially full bypass. When in full bypass, the second pump may produce a very minimal fuel pressure rise and/or may consume very minimal horsepower. During high engine fuel flow demand (e.g., takeoff), the second pump may augment fuel flow from the first pump such that the combined flow from both pumps satisfies the required system pressure and flow.

FIG. 1is a schematic view of an example dual pump/dual bypass fuel pumping assembly100including a movable spool110in an intermediate flow position, according to at least some aspects of the present disclosure.FIG. 2is a schematic view of example dual pump/dual bypass fuel pumping assembly100including movable spool110in a high flowhigh flow position, according to at least some aspects of the present disclosure.FIG. 3is a schematic view of example dual pump/dual bypass fuel pumping assembly100including movable spool110in a low flow position, according to at least some aspects of the present disclosure.

Some example dual pump/dual bypass fuel pumping assemblies100may include a dual bypass valve108. An example dual bypass valve108may include a first inlet port112, which may be selectively connectable to a first bypass port116and/or a first discharge port122. Dual bypass valve108may include a second inlet port114, which may be selectively connectable to a second bypass port118and/or a second discharge port124. Dual bypass valve108may include a movable spool110arranged to modulate fuel flow from first inlet port112to first bypass port116and/or first discharge port122and/or arranged to modulate fuel flow from second inlet port114to second bypass port118and/or second discharge port124, based at least in part on a position of the movable spool110.

Some example dual pump/dual bypass fuel pumping assemblies100may include a first pump102arranged to supply fuel to first inlet port112and/or a second pump104arranged to supply fuel to second inlet port114. In some example embodiments, first pump102and/or second pump104may comprise a positive displacement pump, such as a gear pump, a vane pump, or a gerotor (“generated rotor”) pump.

Some example dual pump/dual bypass fuel pumping assemblies100may include a supply header106arranged to supply fuel to first pump102and/or second pump104. Some example dual pump/dual bypass fuel pumping assemblies100may include a bypass header120fluidically coupled to first bypass port116, second bypass port118, and/or supply header106. Some example dual pump/dual bypass fuel pumping assemblies100may include a discharge header126fluidically coupled to first discharge port122and/or second discharge port124.

Some example dual pump/dual bypass fuel pumping assemblies100may include a check valve128operatively disposed in discharge header126, such as fluidically between first discharge port122and second discharge port124. Check valve128may be arranged to substantially prevent flow from first discharge port122to second discharge port124and/or to allow flow from second discharge port124through discharge header126.

In some example embodiments according to at least some aspects of the present disclosure, the position of movable spool110within dual bypass valve108may determine the amount and/or pressure of fuel directed through discharge header126(which may be consumed by an associated internal combustion engine) and/or the amount and/or pressure of fuel directed to bypass header120(which may be recirculated through first pump102and/or second pump104). For example, with movable spool110in the position illustrated inFIG. 3(e.g., “first” or “low flow” position), movable spool110may direct at least a portion of the fuel flow from first inlet port112to first bypass port116and/or substantially all fuel flow from second inlet port114to second bypass port118. In the low flow position, movable spool110may direct at least some of the fuel flow from first inlet port112to first discharge port122. In other words, movable spool110may modulate fuel flow from first inlet port112between first discharge port122and first bypass port116and may direct substantially all fuel flow from second inlet port114to second bypass port118.

With movable spool110in the position illustrated inFIG. 2(e.g., “second” or “high flow” position), movable spool110may direct substantially all fuel flow from first inlet port112to first discharge port122and/or substantially all fuel flow from second inlet port114to second discharge port124. More specifically, in the second position, movable spool110may direct substantially all fuel flow from first inlet port112to first discharge port122and may modulate fuel flow from second inlet port114between second discharge port124and second bypass port118.

With movable spool110in an intermediate flow position as illustrated inFIG. 1, movable spool110may direct substantially all of the fuel flow from first inlet port112to first discharge port122, at least some fuel flow from second inlet port114to second discharge port124, and/or at least some fuel flow from second inlet port114to second bypass port118.

Some example dual pump/dual bypass fuel pumping assemblies100may include a first control line130operatively coupled to convey pressurized fuel from a control valve assembly (e.g., control valve assembly300ofFIG. 4and/or control valve assembly400ofFIG. 5) to dual bypass valve108to move movable spool110towards the high flow position. Some example dual pump/dual bypass fuel pumping assemblies100may include a second control line132operatively coupled to convey pressurized fuel from a control valve assembly to dual bypass valve108to move movable spool110towards the low flow position. More specifically, the control valve assembly may be configured to raise the pressure delivered to dual bypass valve108via one of first control line130and second control line132while reducing the pressure in the other of first control line130and second control line132. For example, to move movable spool110towards the high flow position, the control valve assembly may raise the pressure in first control line130while lowering the pressure in second control line132. Similarly, to move movable spool110towards the low flow position, the control valve assembly may raise the pressure in second control line132while lowering the pressure in first control line130.

FIG. 4is a schematic view of an example fuel supply system200, according to at least some aspects of the present disclosure. Fuel supply system may include a dual pump/dual bypass fuel pumping assembly100and/or a control valve assembly300, which may be fluidically coupled to dual bypass valve108to modulate fuel pressure in discharge header126. Generally, the example embodiment illustrated inFIG. 4may be particularly advantageous in fuel systems requiring maintenance of adequate pressure for proper operation of downstream multiple metering paths.

Some example control valve assemblies300may include an electrohydraulic servo valve (EHSV)302operatively coupled to an electronic engine controller304(e.g., a full authority digital engine controller (“FADEC”)) and/or a servo valve operatively coupled to direct pressurized fuel to the dual bypass valve via first control line130and second control line132to position the movable spool of the dual bypass valve as directed by the electronic engine controller. Servo valve306may be operatively coupled to be actuated by pressurized fuel received from the electrohydraulic servo valve.

Some example control valve assemblies300may include a pressure transducer308operatively coupled to discharge header126and arranged to provide an electrical signal to electronic engine controller304corresponding to fuel pressure in discharge header126.

An example fuel supply system200may operate as follows. Fuel (e.g., from aircraft tanks) may be supplied to a boost pump310, which may raise the pressure at boost pump discharge (Pb) to a level suitable for charging first pump102and/or second pump104. The electronic engine controller304may schedule the fuel pressure (Ps) to be supplied to the fuel metering unit (FMU) based at least in part upon sensed engine parameters (e.g., compressor discharge pressure). Pressure transducer308may inform the electronic engine controller304of the current, actual Ps pressure in order to close the pressure setting loop. In some example embodiments, Ps may be scheduled such that Ps is generally minimized (accounting for accuracy and safety considerations) at some operating conditions, which may result in reduced power consumption by first pump102and/or second pump104.

Electronic engine controller304in conjunction with EHSV302may set pressure Px. For example, electronic engine controller304may send an electrical command to EHSV302, which may set Px using input pressures Ps and Pb. Variation of Px by EHSV302may cause a variation in the compression of a spring312, thereby changing the force applied to the right end of servo valve306. Since the spring force may be balanced by the force created by Ps acting in the left end of servo valve306, Ps may be directly related to Px. Generally, controlling Ps at or near the lowest value required for any operating condition may result in reduced pump drive horsepower with attendant improvement in overall engine efficiency.

Servo valve306is supplied with Ps and Pb, which may be directed to dual bypass valve108via first control line130and/or second control line132. A difference between actual Ps and desired Ps may result in movement in servo valve306, which may result in a corresponding change in Py (supplied to dual bypass valve108via first control line130) and Pz (supplied to dual bypass valve108via second control line132). Unbalanced pressures Py and Pz may cause movable spool110to move within dual bypass valve108, thereby varying fuel flow to discharge header126and fuel flow recirculated via bypass header120. The variation of fuel flow to discharge header126may adjust the actual Ps to the scheduled Ps.

While the above describes the basic electronic control loop, it will be understood that a substantial change in flow delivered by the FMU to the engine may result in a corresponding change in Ps, which may cause a response of the system to restore Ps control. Such an arrangement may provide improved response over an alternative system relying solely on a basic electronic pressure control loop.

FIG. 5is a schematic view of an example fuel supply system250including an alternative control valve assembly400, according to at least some aspects of the present disclosure. Control valve assembly400may include a metering valve402operatively disposed in the discharge header126. Metering valve402may be configured to modulate fuel flow through discharge header126. An EHSV404may be operatively coupled to metering valve402to position metering valve402as directed by electronic engine controller304. Electronic engine controller304may receive an electrical signal corresponding to the position of metering valve402from a linear variable differential transformer (LVDT)406, which may be operatively coupled to metering valve402. Generally, electronic engine controller304may specify the desired position of metering valve402based upon fuel demand.

Some example control valve assemblies400may include a spool valve408operatively coupled to metering valve402and/or dual bypass valve108. Spool valve408may be configured to direct pressurized fuel to first control line130and/or second control line132of dual bypass valve108to position movable spool110of dual bypass valve108to maintain a desired pressure differential across metering valve402by changing flow into discharge header126. Spool valve408may be actuated using fuel pressure upstream and downstream of metering valve402along with filtered high pressure fuel (Psf) and/or fuel at boost pump pressure (Pb). Generally, spool valve408may be configured to maintain a substantially constant differential pressure across metering valve402, regardless of fuel flow therethrough.

Some example control valve assemblies400may include a pressurizing valve410downstream of metering valve402. Pressurizing valve410may be configured to provide a predetermined downstream reference pressure to metering valve402.

Various example embodiments according to at least some aspects of the present disclosure may be generally applicable to any gas turbine engine and may be particularly advantageous to commercial engines, where reducing fuel burn at cruise may have substantial benefits. Superior thermal management (e.g., less fuel heating due to pumping and recirculation) may offer particular advantages where components are cooled using fuel (e.g., military and commercial engines). Embodiments providing compatibility with a throttling control may allow independent control of multiple flow paths to the combustor. Some embodiments may provide substantially infinite variability in scheduling via software (e.g., in electronic engine controller304).

Generally, regulating fuel pressure according to engine need may limit wasted pump drive horsepower. Use of the bypassing capability may enable the pumping system to be used in conjunction with a throttling-type FMU, which may be more adaptable to the needs of combustion systems requiring multiple independently variable flow paths as compared to a bypassing control operating with a single positive displacement pump.