Patent Application
20140083395
The present disclosure is directed to fuel systems, and more particularly directed to providing compressed gas for fuel delivery systems that use multiple fluids to deliver fuel to an engine.
Many types of devices have been developed over the years for the purpose of converting liquids into aerosols or fine particles readily converted into a gas-phase. Many such devices have been developed, for example, to prepare fuel for use in internal combustion engines. To optimize fuel oxidation within an engine's combustion chamber, the fuel must be vaporized, homogenized with oxidizer (e.g. air), and in a chemically-stoichiometric gas-phase mixture. Ideal fuel atomization and vaporization enables more complete combustion and consequent lower engine out pollution. In the case of underwater or high altitude engine operation, the oxidant may more effectively be of another fluid (gas or liquid). In special service applications, the oxidant is selected based upon its efficacy for combustion irrespective of costs. Another factor of oxidant selection is mass per oxidizing unit (e.g., hydrogen peroxide etc.).
More specifically, relative to internal combustion engines, stoichiometricity is a condition where the amount of oxidant required to completely burn a given amount of fuel is supplied in a homogeneous mixture resulting in optimally correct combustion with no residues remaining from incomplete or inefficient oxidation. Ideally, the fuel should be completely vaporized, intermixed with air, and homogenized prior to ignition for proper oxidation. Non-vaporized fuel droplets do not ignite or combust completely in conventional internal and external combustion engines, which degrades fuel efficiency and increases engine out pollution.
Attempts to reduce or control emission byproducts by adjusting temperature and pressure typically affects the NOx byproduct. To meet emission standards, these residues must be dealt with, typically requiring after treatment in a catalytic converter or a scrubber. Such treatment of these residues results in additional fuel costs to operate the catalytic converter or scrubber and may require additional component costs as well as packaging and mass implications. Accordingly, any reduction in engine out residuals resulting from incomplete combustion would be economically and environmentally beneficial.
Aside from the problems discussed above, a fuel that is not completely vaporized in a chemically stoichiometric air/fuel mixture causes the combustion engine to perform at less than peak efficiency. A smaller portion of the fuel's chemical energy is converted to mechanical energy when fuel is not completely combusted. Fuel energy is wasted and unnecessary pollution is created. Thus, by further breaking down and more completely vaporizing the fuel-air mixture, better fuel efficiency may be available.
Many attempts have been made to alleviate the above-described problems with respect to fuel vaporization and incomplete fuel combustion. In automobile engines, for example, inlet port or direct fuel injection have almost universally replaced carburetion for fuel delivery. Fuel injectors spray fuel directly into the inlet port or cylinder of the engine and are controlled electronically. Injectors facilitate more precise metering and control of the amount of fuel delivered to each cylinder independently relative to carburetion. This reduces or eliminates charge transport time facilitating optimal transient operation. Nevertheless, the fuel droplet size of a fuel injector spray is not optimal and there is little time for the fuel to mix with air prior to ignition.
Some types of fuel delivery systems require a source of compressed air to properly delivery fuel to the cylinder for combustion. The compressed air is typically provided by the engine, a compressor component operated by the engine, or electrically off-board of the engine. Challenges exist related in providing a source of compressed air for the fuel delivery system when starting the engine before the compressor is operating.
The principles described herein may address some of the above-described deficiencies and others. One aspect provides an air charging system that includes a valve providing access to an engine cylinder, an accumulator coupled in flow communication with the valve, and a controller operable to open and close the valve until a threshold pressure condition is reached in the accumulator.
The valve may include a poppet valve. The poppet valve may be biased into a closed position. The controller may open the valve during a compression cycle during the engine start cycle. The controller may operate to control flow of compressed air stored in the accumulator to a fuel delivery system. The accumulator may include a storage tank. The accumulator may hold a volume of compressed air sufficient for at least one engine firing sequence. The valve may include a poppet valve opening in the cylinder that is arranged outward opening. The charging system may include a solenoid configured to move the valve between opened and closed positions.
Another aspect of the present disclosure relates to a method of scavenging compressed air from an engine cylinder. The method includes providing a valve and an accumulator, wherein the valve provides access to the engine cylinder and the accumulator is coupled in flow communication with the valve. The method also includes opening the valve during an engine compression stroke, collecting compressed air from the cylinder into the accumulator while the valve is opened, and storing the compressed air in the accumulator for use in a fuel delivery system.
The method may also include closing the valve upon reaching a predetermined pressure condition in the accumulator. The method may include closing the valve upon completion of the engine compression stroke. The valve may include a valve opening directly into the cylinder, a valve seat positioned within the cylinder, and a poppet valve movable into and out of sealing contact with the valve seat. The method may include biasing the valve into a closed position.
Another method in accordance with the present disclosure relates to a method of starting an engine. The method includes providing an air charging system and a fuel delivery system, wherein the air charging system includes a valve configured to access a power cylinder of the engine, and an accumulator connected in flow communication with the valve and the fuel delivery system. The method includes opening the valve during a compression cycle of the engine, collecting compressed air from the cylinder into the accumulator, delivering the compressed air from the accumulator to the fuel delivery system, and delivering fuel from the fuel delivery system to the cylinder to start the engine.
The method may include closing the valve after completing the compression cycle of the engine. The method may include closing the valve after a predetermined pressure condition is reached in the accumulator. The method may include delivering the compressed air to the fuel delivery system only after a predetermined pressure condition is reached in the accumulator. The method may include shutting off the compressed air from the accumulator to the fuel delivery system after the engine is started. The method may further include using multiple compression cycles of the engine to reach the predetermined pressure condition in the accumulator. The method may also include providing a solenoid to operate the valve between opened and closed positions based on a compression cycle of the cylinder and a pressure condition in the accumulator.
The accompanying drawings illustrate certain embodiments discussed below and are a part of the specification.
Throughout the drawings, identical reference characters and descriptions indicate similar, but not necessarily identical elements.
Illustrative embodiments and aspects are described below. It will, of course, be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.
The present disclosure is directed to fuel preparation systems and methods, and related systems and methods for creating charged air that is used for the fuel preparation system. One type of fuel preparation system has a dual fluids input, wherein one of the fluids is gas (e.g., air) and the other fluid is a liquid (e.g., liquid fuel such as gasoline). A supply of the gas is needed to commence operation of the fuel preparation system in order to deliver a prepared fuel charge to the engine for starting the engine. Once the engine is running, a mechanically or electrically driven compressor may assume the task of providing a source of the compressed gas to the fuel preparation system. The supply of compressed gas prior to starting the engine may be provided using, for example, a charge accumulator tank, a converter, a reformer, or other charge supply device.
An example air charging system in accordance with the present disclosure collects compressed air from a cylinder of the engine during a compression stroke of an initial engine rotation while the engine is cranking for startup. The compressed air is stored in an accumulator to provide sufficient air volume for operating the fuel preparation system to start the engine. At least one compression cycle may be required to sufficiently charge the air charging system to provide adequate air volume for starting the engine. Air pressure within the accumulator may be monitored during engine start cranking to determine when the firing sequence may commence (e.g., delivery of fuel from a fuel preparation system). Once the engine begins firing, an engine driven or off-engine compressor may assume responsibility for providing compressed air to the fuel preparation system. In one example, a variable displacement compressor may be applied at transient engine demand volumes—thus reducing parasitic losses at lower volumes.
The example air charging systems disclosed herein may operate to scavenge gases (e.g., air) from a power cylinder of an engine during engine start cranking. The scavenged compressed air may be used with a fuel preparation system such as a dual fluid injection system to start the engine. An example dual fluid injection system and related methods is disclosed in U.S. Patent Publication No. 2011/0284652, which is incorporated herein in its entirety by this reference.
An example air charging system in accordance with the present disclosure includes a charge valve assembly, an accumulator, a control valve and a controller (e.g., an engine control unit (ECU)). The charge valve assembly may include a valve member (e.g., a poppet valve) that provides access into a power cylinder combustion chamber of the engine. Compressed air is extracted from the engine power cylinder through the charge valve assembly during a compression cycle of the engine. The compressed air is stored in the accumulator. The charge valve assembly operates between open and closed positions to collect the compressed air from the engine power cylinder (typically during the compression stroke). Air may be collected from the power cylinder compression stroke in multiple cycles until a threshold pressure is reached in the accumulator. The controller then initiates an engine starting sequence in which compressed air from the accumulator is delivered to an air metering device that supplies compressed air to a fuel delivery device, which delivers fuel to the engine. Once the engine is started, the control valve switches from the accumulator to a compressor that operates under power of the engine, either mechanically or electrically, for supply of compressed air to the air metering device.
Referring now to
The controller 22 may control operation of a plurality of features of air charging system 10. For example, controller 22 may receive sensor signals from engine 28 related to a position of the piston in engine cylinder 30 to help determine when the charge valve assembly 12 should be operated between opened and closed positions. Sensor signals from the air system (e.g., from sensor 329 on the air supply rail, manifold or other portion of the system as shown in
Referring to
The charge valve assembly 12 shown in
As noted above, a sensor may be used to determine a position of the piston operating in engine cylinder 30. The controller 22 operates the charge valve assembly 12 between closed and opened positions based on a position of the piston operating within engine cylinder 30 (e.g., a crank position). A plurality of sensors may be used, wherein one sensor indicates a crank position while another sensor determines which cycle the cylinder is in. Typically, the charge valve assembly 12 is operated into an open position during a compression stroke and is closed during the remaining crank positions. The charge valve assembly 12 may be opened and closed several times (e.g., an opening cycle) in order to obtain the amount of compressed air in accumulator 14 needed to operate the fuel delivery device 26.
The accumulator 14 may have any desired shape, size, and volume. The accumulator 14 may be a separately formed structure that is mounted outside of engine 28. In an alternative configuration, the accumulator 14 is integrated into the engine 28, such as being formed (e.g., cast) into a portion of the engine block or head.
The control valve 16 may be, for example and without limitation, a three-way valve or a shuttle valve. A control valve 16 operates between a first position in which gases flow from the charge valve assembly 12 to accumulator 14, and a second position in which the flow path from the charge valve assembly 12 to the accumulator 14 is closed and a separate flow path between the compressor 18 and the accumulator 14 is opened. The control valve 16 may be operated between the first and second positions based on, for example, a pressure condition sensed within accumulator 14, an operating state of compressor 18, and an operating condition of engine 28.
The compressor 18 may be a mechanically driven or electric compressor. A mechanically driven compressor 18 is typically operable after the engine 28 has started and is powered by engine 28. An electric compressor may operate using power generated by engine 28 or may draw power from a different power source such as batteries that are independent of engine operation. Using a mechanically driven compressor 18 may provide a low cost, low weight, simple option for providing the minimum requirements for compressed air for the fuel delivery device 26.
The one-way valve 20 is positioned in the flow line between the charge valve assembly 12 and the accumulator 14 or control valve 16. The one-way valve 20 helps prevent backflow of compressed air collected from the charge valve assembly 12.
The controller 22 may be part of an engine control unit (ECU). The controller 22 may receive inputs from a variety of sensors of the air exchange system 10 and engine 28, and receive feedback concerning operation of various components of the air charging system 10, fuel delivery device 26 and engine 28. At a minimum, the controller 22 typically controls operation of the charge valve assembly 12 between opened and closed positions, controls operation of the control valve 16 between first and second positions, and controls delivery of compressed air stored in accumulator 14 or delivered from compressor 18 to the air metering device 24. The controller 22 may provide other operations and related methods for the air charging system 10.
The air metering device 24 may regulate the flow rate and pressure condition of compressed air stored in the accumulator 14 that is delivered to the fuel delivery device 26. In one example, the air metering device 24 provides a flow of air at a pressure of about 4 Bar/58 psi to about 6 Bar/87 psi and at a flow rate of about 2.2 kg/hr to about 22 kg/hr.
In the arrangement shown in
Referring now to
As noted above,
The accumulator 314 is positioned in the line between control valve 316 and the first and second fuel delivery devices 326A, 326B. The first and second charge valve assemblies 312A, 312B are connected in flow communication with the control valve 316.
Referring to
Further steps of the method 400 may include operating the control valve after the engine starts to receive compressed air from a compressor (e.g., a mechanical or electric compressor), which is operated using power from the engine. The compressed air provided by the compressor may be used to operate the fuel delivery device to continue operation of the engine.
The air charging systems disclosed herein may be used as back-up systems for the compressor after the engine has started. For example, the compressor may malfunction during operation of the engine. The controller of the air charging system may identify that the compressor has malfunctioned (e.g., senses a drop in pressure supplied to the fuel delivery device via the air metering device), and switch the control valve 16 to receive compressed air from the charge valve assembly for ongoing operation of the engine.
In one example, the accumulator 14 may be charged with an amount of compressed gas that exceeds the amount (e.g., pressure level) needed for operating the fuel delivery device 26. The additional gases collected in the accumulator 14 may be used to operate the engine for a temporary period of time after the engine starts and before the compressor 18 is fully operational and generating sufficient compressed air to operate the fuel delivery device 26. The threshold pressure condition set for the accumulator 14 before initiating the start cycle for engine 28 may be above the minimum amount of air pressure needed to start the engine and/or initially operate the fuel delivery device.
Referring now to
The method 500 may also include switching between the accumulator as a source of compressed air and a compressor such as a mechanical compressor that is powered by the engine after the engine is started. Alternatively, the accumulator is used to collect compressed air from either the engine cylinder or the compressor depending on an operated position of the control valve. The accumulator may act as a buffer as the amount of compressed air provided from either the engine cylinder or the compressor fluctuates prior to and after the engine starts.
The in-cylinder charge valve(s) and accumulator(s) may be used during braking to provide “regenerative braking” power by storing air compressed by the engine. The pressure buildup during compression into the accumulator provides engine braking, thus more efficient braking of the vehicle. The stored gas (e.g., air) is then routed to a pneumatic motor or other air operated driveline component to provide vehicle launch or torque assist during higher torque demand modes thus reducing fuel consumption.
Another example method in accordance with the present disclosure relates to retrofitting an engine with the air charging system. The method may include forming (e.g., drilling) a valve opening and valve seat in the housing in which the engine cylinder is formed. The valve member is mounted to the engine and operable in the valve opening to control flow of gases from the engine cylinder 30 to the accumulator 14. The accumulator 14 is coupled in flow communication with the air metering device 24 and the air metering device 24 is coupled in flow communication with the fuel delivery device 26. The compressor 18 may also be coupled in flow communication with the air metering device 24. A control valve may be positioned in the flow line between the charge valve and the accumulator, or between the accumulator and the air metering device as described above with reference to
One advantage associated with using the air charging systems disclosed herein is facilitating engine starting using the engine as an air pump during engine cranking, thereby eliminating the need for a separately powered air source during start up of the engine.
Another potential advantage is mitigating the risks associated with attempting to store compressed air for use by a fuel delivery device during start up of an engine. Dissipation of stored air may result from permeability of the storage device or leaks in the system that may occur when the engine is not running. Dissipation of the stored air charge would other inhibit operation of a dual fluids fuel delivery device. The air charging systems disclosed herein may avoid reliance upon stored compressed air by collecting a volume of compressed air while cranking the engine during or just before starting.
Another potential advantage relates to eliminating the need for an electrical pump to charge the accumulator or otherwise supply compressed air to the fuel delivery device prior to starting the engine. Avoiding the use of an electric pump may conserve battery capacity that may otherwise be needed for operation of the engine and other components such as components of a vehicle that carries the engine.
A further potential advantage may relate to implementation of a mechanical, engine driven compressor pump to provide a source of compressed air after the engine is started. The use of a mechanical compressor pump may be advantageous where there is limited electrical load available.
A still further potential advantage relates to the added functionality provided by the air charging system with relatively little or no increased reciprocating mass, parasitic load or inertia.
A dual fluids system may be ideal for employing a variety of oxidants and mixtures tailored to a specific mission.
The preceding description has been presented only to illustrate and describe certain aspects, embodiments, and examples of the principles claimed below. It is not intended to be exhaustive or to limit the described principles to any precise form disclosed. Many modifications and variations are possible in light of the above disclosure. Such modifications are contemplated by the inventor and within the scope of the claims. The scope of the principles described is defined by the following claims.
