CA2849623C

CA2849623C - Fuel system for an internal combustion engine

Info

Publication number: CA2849623C
Application number: CA2849623A
Authority: CA
Inventors: Nikolas Goodfellow
Original assignee: Westport Power Inc
Current assignee: Westport Fuel Systems Canada Inc
Priority date: 2014-04-17
Filing date: 2014-04-17
Publication date: 2015-04-07
Anticipated expiration: 2034-04-17
Also published as: WO2015157858A1; CA2849623A1

Abstract

Some engines employ a fuel for purposes other than for combusting in motoring. These engines take longer to start and have reduced efficiency in certain operating modes. An improved fuel system for an internal combustion engine comprises a fuel supply in fluid communication with and supplying a fuel for motoring the internal combustion engine. A fuel employer is in fluid communication with the fuel supply and employs the fuel for purposes other than as a source of energy for combusting in the internal combustion engine. There is a valve for selectively enabling fluid communication between the fuel supply and the fuel employer. The valve is closed to disable the fuel employer when not needed to reduce the demand on the fuel supply.

Description

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FUEL SYSTEM FOR AN INTERNAL COMBUSTION ENGINE
Field of the Invention [0001] The present application relates to a fuel system for an internal combustion engine, and more particularly a fuel system for reducing start time.
Background of the Invention

[0002] Some engines employ fuel for additional purposes, and not only as a source of energy that is consumed by combustion for motoring. For example, engines that employ concentric needle-type fuel injectors, such as disclosed in U.S. Patent No.
6,336,598, issued January 8, 2002 and which is co-owned by the Applicant, inject a pilot fuel and a main fuel separately and independently through the fuel injectors. An additional purpose of the pilot fuel is for use as a hydraulic fluid within the fuel injector for actuating a pilot injection valve or a main injection valve by controlling pilot fuel pressure in an actuator control chamber in response to a pilot fuel injection command or a main fuel injection command respectively. The pilot fuel also acts a liquid seal within the injector preventing the main fuel, which is typically a gaseous fuel such as natural gas, from leaking out of the injector. The pressure differential between the pilot fuel and main fuel is maintained within a predetermined range for proper functioning of the liquid seal. The pilot fuel, which is typically diesel, can also be employed as a reference fuel for regulating the pressure of the main fuel. The Applicant's U.S. Patent No. 6,298,833, issued October 9, 2001, describes a fluid seal apparatus and method for dynamically controlling sealing fluid pressure, and which uses pilot fuel in a pilot fuel rail to regulate the pressure of the main fuel to within the predetermined range. The pressure difference between the pilot fuel and the main fuel is known as the system bias pressure.

[0003] In other applications, the pilot fuel can be employed as a hydraulic fluid for actuating a main fuel pumping apparatus, such as disclosed in Canadian Patent No.

2,758,246, issued February 12, 2013 and which is co-owned by the Applicant.
After pilot fuel is pressurized to injection pressure by a pilot fuel pump, such as a common rail pump, a portion of the pilot fuel flow is employed to hydraulically actuate the main fuel pumping apparatus. By employing the pilot fuel as a hydraulic fluid a separate hydraulic system is not required thereby eliminating the need for a hydraulic reservoir and a hydraulic pump, along with other components normally found in hydraulic systems.
100041 The start times for internal combustion engines employing the techniques described above have increased compared to previous internal combustion engines.
Efficiency has also decreased due to increased fuel flow demand at times when it is not needed. The state of the art is lacking in techniques for reducing start times and improving efficiency for internal combustion engines that employ a fuel for purposes other than as a source of energy for combustion.
Summary of the Invention [0005] An improved fuel system for an internal combustion engine comprises a fuel supply in fluid communication with and supplying a fuel for motoring the internal combustion engine. A fuel employer is in fluid communication with the fuel supply and employs the fuel for purposes other than as a source of energy for combusting in the internal combustion engine. There is a valve for selectively enabling fluid communication between the fuel supply and the fuel employer. The valve is closed to disable the fuel employer when not needed to reduce the demand on the fuel supply. In a preferred embodiment the fuel is a liquid fuel such as Diesel. The fuel employer can be a fuel consumer that consumes an average flow of fuel.
[0006] The valve can be one of a solenoid valve, an injection-type valve and a variable flow rate valve. However other types of valve that can close fluid communication between the fuel supply and the fuel employer can also be used.
For example, the valve can be a mechanically actuated valve comprising a first check valve that selectively allows fluid communication from the fuel supply to the fuel employer.
The first check valve is actuatable to an open position when a pressure upstream from the first check valve is at least a third predetermined value, and actuatable to a closed position when a pressure upstream from the first check valve reduces from the third predetermined value to a fourth predetermined value. The mechanically actuated valve can further comprise a second check valve that selectively allows fluid communication from the fuel employer to the fuel supply. The second check valve is actuatable to an open position when a pressure differential across the valve is at least a fifth predetermined value.
[0007] In a preferred embodiment, there is a controller operatively connected with the valve and programmed to selectively enable fluid communication through the valve. The controller can be programmed to close the valve when the internal combustion engine is starting to reduce the demand on the fuel supply, allowing the fuel pressure to increase more rapidly thereby reducing start time.
[0008] In another preferred embodiment, the fuel supply is a first fuel supply, and the fuel is a first fuel, and the fuel employer is a first fuel employer. The fuel system further comprises a second fuel supply supplying a second fuel, wherein the second fuel is selectively combusted in the internal combustion engine. The first fuel can be a liquid fuel and the second fuel can be a gaseous fuel. The first fuel employer can be a pumping apparatus in fluid communication with the second fuel supply for pressurizing the second fuel. Alternatively, or additionally, the first fuel employer can be a second fuel pressure regulating apparatus in fluid communication with the second fuel supply that employs the first fuel to regulate the pressure of the second fuel. The fuel system can comprise a second valve for selectively enabling fluid communication between the second fuel supply and the second fuel pressure regulating apparatus. A controller operatively connected with the second valve can be programmed to selectively open the second valve when the second fuel is required downstream, for example for combusting in the engine.

- 4 -[0009] An improved method for reducing demand on a fuel supply supplying a fuel to an engine for combusting and to a fuel employer for purposes other than for combusting in the engine, the method comprises closing fluid communication between the fuel supply and the fuel employer when not needed. For example, the fluid communication can be closed when the engine is starting, reducing demand on the fuel supply and thereby allowing the fuel to increase in pressure more rapidly, which reduces start time on the engine. In a preferred embodiment, the method comprises pressurizing the fuel to an injection pressure; injecting the fuel into a combustion chamber where it is combusted;
and opening fluid communication between the fuel supply and the fuel employer such that the fuel pressure does not drop below the injection pressure.
[0010] In another preferred embodiment, the fuel supply is a first fuel supply, and the fuel is a first fuel, and the fuel employer is a first fuel employer, and further comprising a second fuel supply supplying a second fuel to the engine for combusting. The method further comprises closing fluid communication between the second fuel supply and the engine when the engine is starting.
Brief Description of the Drawings 100111 FIG. 1 is schematic view of a fuel system for an internal combustion engine according to a first embodiment.
[0012] FIG. 2 is a flow chart of a method for starting the internal combustion engine of FIG. 1.
[0013] FIG. 3 is a plot view of a first fuel pressure for the internal combustion engine of FIG. 1 showing a first trace when the internal combustion engine is not employing the method of FIG. 2 and a second trace when the internal combustion engine is employing the method of FIG. 2.

-5-[0014] FIG. 4 is a plot view of engine speed for the internal combustion engine of FIG. 1 showing a first trace when the internal combustion engine is not employing the method of FIG. 2 and a second trace when the internal combustion engine is employing the method of FIG. 2.
[0015] FIG. 5 is a schematic view of a fuel system for an internal combustion engine according to a second embodiment.
[0016] FIG. 6 is a schematic view of a fuel system for an internal combustion engine according to a third embodiment.
[0017] FIG. 7 is a schematic view of a fuel system for an internal combustion engine according to a fourth embodiment.
Detailed Description of Preferred Embodiment(s) [0018] Referring to FIG. 1, fuel system 10 supplies fuel to engine 20.
First fuel supply 30 supplies a first fuel to engine 20 along conduit 40. Engine 20 consumes the first fuel in one or more combustion chambers (not shown). First fuel supply 30 is also in fluid communication with valve 50 by way of conduit 40 and conduit 60. Valve selectively enables fluid communication of the first fuel over conduit 70 to first fuel employer 80, which employs the first fuel for reasons other than supplying a source of energy for motoring engine 20. First fuel employer 80 is in fluid communication with second fuel supply 90 that supplies a second fuel, and the first fuel employer uses the first fuel to supply the second fuel to engine 20 at injection pressure within a predetermined range of tolerance. First fuel employer 80 can be a pressure regulating apparatus that regulates the pressure of the second fuel based on the pressure of the first fuel, for example such as a dome loaded regulator. Alternatively, first fuel employer 80 can be a pressure regulating apparatus that employs the first fuel as a hydraulic fluid to actuate a pump or compressor to pressurize the second fuel. In other embodiments, first fuel . ,

-6-employer 80 can be any component or apparatus that employs the first fuel for reasons other than as a source of energy for motoring engine 20. When first fuel employer 80 requires a flow of the first fuel to perform its function than first fuel employer 80 is also referred to as a first fuel consumer.
100191 Controller 100 monitors and manages the operation of fuel system 10 and engine 20. Various sensors and actuators (not shown) throughout system 10 and engine send respective engine operating data to controller 100, and this transfer of engine operating data is represented collectively by communication line 110, which is illustrated showing hi-directional communication lines since controller 100 can send commands for example to drivers and actuators, and to some sensors, and also receives information from 15 the sensors. In the figures, dotted lines represent electrical communication lines, and the arrows at the ends of these communication lines represent that information, such as status information and commands, can be transmitted in the direction of these arrows.

Controller 100 is operatively connected with valve 50 to selectively enable the flow of the first fuel between first fuel supply 30 and first fuel employer 80. In a preferred 20 embodiment valve 50 is a variable flow rate valve that can allow a variable flow rate of the first fuel as will be described in more detail below. As an example only, valve 50 can be a solenoid type valve, an injector type valve, an electromechanical type valve and a servo-assisted type valve. Controller 100 can also be operatively connected with first fuel supply 30 and second fuel supply 90 as required to command components therein for supplying the first fuel and the second fuel respectively. As would be understood by those familiar with the technology, controller 100 can also be operatively connected with engine 20. Controller 100 can comprise both hardware and software components.
The hardware components can comprise digital and/or analog electronic components.
In the embodiments herein controller 100 comprises a processor and memories, including one or more permanent memories, such as FLASH, EEPROM and a hard disk, and a temporary memory, such as SRAM and DRAM, for storing and executing a program.
In another preferred embodiment electronic controller 100 is an engine control unit (ECU)

-7-for engine 20. As used herein, controller 100 is also referred to as 'the controller'. As used herein, the terms algorithm and step refer to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. In preferred embodiments the algorithms and steps herein are part of controller 130.
[00201 When engine 20 starts the first fuel must be pressurized to injection pressure before one or more injectors (not shown) can inject the fuel into the one or more combustion chambers of the engine. In a preferred embodiment the first fuel is a pilot fuel, such as diesel, and the second fuel is a main fuel, such as natural gas, and engine 20 can start with only the first fuel or can start with both the first fuel and the second fuel, in either case the first fuel must be pressurized to injection pressure before the engine can start. First fuel supply 30 pressurizes the first fuel, for example using a common rail pump that pressurizes diesel fuel. The rate of pressure increase of the first fuel downstream from first fuel supply 30 is related to the total volume downstream of the first fuel supply into which the first fuel is being supplied. The greater the downstream volume the slower the rise in the pressure of the first fuel. When the downstream volume is reduced the amount of time it takes to pressurize the first fuel to a first predetermined pressure decreases, thereby decreasing the start time of engine 20. An advantage of the disclosed apparatus is that the first fuel can then be pressurized in a reduced amount of time when valve 50 is closed such that the downstream volume is reduced. When valve 50 is closed first fuel supply 30 does not need to supply the first fuel to conduit 70 and first fuel employer 80. First fuel employer 80 typically requires at least a minimum quantity of the first fuel to operate or a minimum continuous flow rate of the first fuel. In a preferred embodiment, engine 20 starts with only the first fuel according to the algorithm of FIG.2 that will now be described.

-8-[0021] With reference to FIG. 2, a method of starting engine 20 is now discussed. In step 200 a start command is received by controller 100, such as a key ignition signal or the like, after which the controller commands first fuel supply 30 to pressurize the first fuel in step 210. In a preferred embodiment valve 50 is a normally open valve such that controller 100 commands the valve to close (also done in step 210) such that the downstream volume is reduced. Valve 50 can also be a normally closed valve. It is expected throughout the operation of engine 20 that valve 50 will be open more than it is closed, and depending upon the type of valve it may be more energy efficient to employ a normally open valve that must be closed at start-up. Controller 100 monitors the pressure of the first fuel in conduit 40 in step 220 and when the pressure rises above a first predetermined value the controller commands the one or more fuel injectors in step 230 to inject the first fuel into the one or more combustion chambers respectively where it is ignited and combusted, thereby starting engine 20. After engine 20 starts, which can be determined by monitoring engine speed, controller 100 commands valve 50 to open in step 240 in a manner where the first fuel remains at a pressure in conduit 40 that allows the first fuel to be injected into the one or more combustion chambers. When valve 50 is the type that allows a variable flow rate by adjusting a flow area, then controller 100 can command the valve to gradually increase the flow area until the pressure in conduit 40 is equal to the pressure in conduit 70. When valve 50 is the type that allows for a variable flow rate (for example an injector type valve), then controller 100 can command the valve to gradually increase the flow rate until the pressure in conduit 40 is equal to the pressure in conduit 70. Typically, when engine 20 starts the ability of first fuel supply 30 to supply the first fuel improves. For example, when first fuel supply comprises a fuel pump driven directly by engine 20, the flow capacity of the fuel pump increases as the engine speed of the engine increases. During cranking the engine speed is low and the ability of first fuel supply 30 to supply the first fuel is reduced compared to when engine 20 is running.
Depending upon the demand for the first fuel by first fuel employer 80, it is possible that valve 50 can be the open or closed type that can simply be made open after engine 20 starts.

-9-[0022] Valve 50 can also be closed when first fuel employer 80 is not needed.
For example, there can be engine modes other than start-up where engine 20 fuels exclusively with the first fuel. In these modes controller 100 command valve 50 to close reduce fuel demand on first fuel supply 30. In a preferred embodiment, when the first fuel is Diesel and the second fuel is natural gas, one such mode is referred to as Run On Diesel (ROD).
In this mode engine 20 is fuelled exclusively with Diesel and second fuel supply 90 is commanded to shut-off the supply of natural gas. First fuel employer 80 is a pressure regulating apparatus that regulates natural gas pressure downstream of the first fuel employer based on Diesel pressure in conduit 40. It is advantageous to close valve 50 to reduce and preferably eliminate any Diesel leakage in the pressure regulating apparatus in the ROD mode.
[0023] Referring now to FIGS. 3 and 4, test data illustrates the reduction in start time by employing the technique herein. Trace 300 in FIG. 3 illustrates the first fuel pressure with valve 50 open as engine 20 is started, and trace 310 illustrates the first fuel pressure when engine 20 starts using the method of FIG. 2 with valve 50 closed.
Similarly, trace 320 in FIG. 4 illustrates the engine speed with valve 50 open, and trace 330 illustrates the engine speed with valve 50 closed. When a starter motor for engine 20 begins to crank the engine at start-up, the first fuel pressure gradually begins to rise.
During this initial phase the engine speed is low due to the limited capacity of the start motor to crank the engine. Although different criteria can be used to determine when engine 20 starts, as used herein engine 20 starts when the first fuel is injected into and combusted in the combustion chambers of the engine. At this point in start-up the engine speed increases rapidly since it is no longer solely relying on the crank motor and engine 20 begins to run due to combustion of the first fuel. In FIGS. 3 and 4, engine 20 starts at time tsc with valve 50 closed, and at time tso with valve 50 open. The pressure of the first fuel increases to the first predetermined value (Puic) at time tsc (approximately 0.6 seconds) in trace 310 when valve 50 is closed, and when the valve is open the pressure of the first fuel reaches a suitable injection pressure at time to (approximately 5.6 seconds) in trace . ,

- 10 -300. In this particular test, pressure PTH0 is greater than pressure Puic to ensure the first fuel pressure in conduit 40 does not drop below injection pressure as a result of fuelling demand of first fuel employer 80. As a more direct comparison, when engine 20 starts with valve 50 open the first fuel pressure takes approximately 4.8 seconds to reach the first predetermined value Pnic in trace 300, compared to 0.6 seconds in trace 310. The engine speeds in FIG. 4 can be seen to track the respective fuel pressures in FIG. 3.
[0024] With reference to FIG. 5, there is shown fuel system 12 according to a second embodiment that is similar to the first embodiment and where like parts in this embodiment and all other embodiments have like reference numerals and may not be described in detail if at all. Second valve 55 selectively enables the fluid communication of the second fuel between second fuel supply 90 and first fuel employer 80.
Second valve 55 operates as a second fuel shut-off valve such that the pressure of the second fuel in an accumulator not shown separately but included as part of second fuel supply 90 can be maintained above a second predetermined value when engine 20 shuts down.
[0025] Referring now to FIG. 6, there is shown fuel system 13 according to a third embodiment. Valve 51 comprises a mechanical arrangement of components to selectively enable fluid communication of the first fuel between conduit 60 and conduit 70 and first fuel employer 80, and vice versa. Check valve 51 allows fluid communication between conduit 60 and conduit 70 when the first fuel pressure in conduit 60 reaches a third predetermined value, until this condition is met the check valve is closed.
For example, when engine 20 begins the start-up sequence, check valve 51 is closed until the first fuel pressure increases to the third predetermined value, which happens after engine 20 has started. Once check valve 51 is opened it remains open until the first fuel pressure in conduit 60 drops below a fourth predetermined value, and in this manner check valve 51 can be said to have hysteresis. When engine 20 is shutdown, the first fuel pressure in conduit 70 can be reduced when check valve 53 opens. The first fuel in conduit 40 and conduit 60 drains to a return line (not shown) after engine 20 shuts down, allowing the

-11-first fuel pressure in these conduits to reduce. Once the first fuel pressure in conduit 60 drops below the first fuel pressure in conduit 70 by a fifth predetermined value, the differential pressure, check valve 53 opens allowing the flow of the first fuel from conduit 70 to conduit 60.
[0026] Referring now to FIG. 7, there is shown fuel system 14 according to a fourth embodiment. Fuel system 14 is a mono-fuel system that employs a fuel from fuel supply 31 for combusting in combustion chambers of engine 20 and for other purposes with fuel employer 81. In a preferred embodiment the fuel is a liquid fuel, such as Diesel. Fuel employer 81 can use the fuel as a hydraulic fluid for any application requiring a hydraulic system, such as a pump drive, an air compressor, and other auxiliary systems.
When starting engine 20 and when the function of fuel employer 81 is not required valve 50 can be closed to reduce demand on fuel supply 31.
[0027] While particular elements, embodiments and applications of the present invention have been shown and described, it will be understood, that the invention is not limited thereto since modifications can be made by those skilled in the art without departing from the scope of the present disclosure, particularly in light of the foregoing teachings.

Claims

What is claimed is:

1. A fuel system for an internal combustion engine comprising:
a fuel supply in fluid communication with and supplying a fuel for motoring the internal combustion engine;
a fuel employer in fluid communication with the fuel supply and employing the fuel for purposes other than as a source of energy for combusting in the internal combustion engine; and a valve for selectively enabling fluid communication between the fuel supply and the fuel employer;
wherein the valve is closed to disable the fuel employer when not needed to reduce the demand on the fuel supply.

2. The fuel system of claim 1, wherein the fuel is a liquid fuel.

3. The fuel system of claim 1, wherein the valve is one of a solenoid valve, an injection-type valve and a variable flow rate valve.

4. The fuel system of claim 1, wherein the fuel employer is a fuel consumer that demands a flow of the fuel.

5. The fuel system of claim 1, further comprising a controller operatively connected with the valve and programmed to selectively enable fluid communication through the valve.

6. The fuel system of claim 5, wherein the controller is programmed to close the valve when the internal combustion engine is starting.

7. The fuel system of claim 1, wherein the valve comprises a first check valve that selectively allows fluid communication from the fuel supply to the fuel employer, the first check valve is actuatable to an open position when a pressure upstream from the first check valve is at least a third predetermined value, and actuatable to a closed position when a pressure upstream from the first check valve reduces from the third predetermined value to a fourth predetermined value.

8. The fuel system of claim 7, wherein the valve further comprises a second check valve that selectively allows fluid communication from the fuel employer to the fuel supply, the second check valve is actuatable to an open position when a pressure differential across the valve is at least a fifth predetermined value.

9. The fuel system of claim 1, wherein the fuel supply is a first fuel supply, and the fuel is a first fuel, and the fuel employer is a first fuel employer, further comprising a second fuel supply supplying a second fuel, wherein the second fuel is selectively combusted in the internal combustion engine.

10. The fuel system of claim 9, wherein the first fuel is a liquid fuel and the second fuel is a gaseous fuel.

11. The fuel system of claim 9, wherein the first fuel employer is a pumping apparatus in fluid communication with the second fuel supply for pressurizing the second fuel.

12. The fuel system of claim 9, wherein the first fuel employer is a second fuel pressure regulating apparatus in fluid communication with the second fuel supply that employs the first fuel to regulate the pressure of the second fuel.

13. The fuel system of claim 12, further comprising a second valve for selectively enabling fluid communication between the second fuel supply and the second fuel pressure regulating apparatus.

14. The fuel system of claim 13, further comprising a controller operatively connected with the second valve and programmed to selectively open the second valve.

15. A method for reducing demand on a fuel supply supplying a fuel to an engine for combusting and to a fuel employer for purposes other than for combusting in the engine, the method comprising closing fluid communication between the fuel supply and the fuel employer when not needed.

16. The method of claim 15, wherein the fluid communication is closed when the engine is starting.

17. The method of claim 16, further comprising:
pressurizing the fuel to an injection pressure;
injecting the fuel into a combustion chamber where it is combusted; and opening fluid communication between the fuel supply and the fuel employer such that the fuel pressure does not drop below the injection pressure.

18. The method of claim 15, wherein the fuel is a liquid fuel.

19. The method of claim 15, where the fuel supply is a first fuel supply, and the fuel is a first fuel, and the fuel employer is a first fuel employer, further comprising a second fuel fuel supply supplying a second fuel to the engine for combusting, the method further comprising closing fluid communication between the second fuel supply and the engine when the engine is starting.

20. The method of claim 19, wherein the first fuel is a liquid fuel and the second fuel is a gaseous fuel.