WO2009062228A1

WO2009062228A1 - Fuel delivery apparatus and method

Info

Publication number: WO2009062228A1
Application number: PCT/AU2008/001621
Authority: WO
Inventors: Francisco Antonio D'amico; Justin Barry Rasmussen; Raymond Leslie Watt; Robert Michael Remedi
Original assignee: D-Gas Pty Ltd
Priority date: 2007-11-13
Filing date: 2008-10-31
Publication date: 2009-05-22

Abstract

An apparatus is described for delivering a secondary fuel to a diesel engine (30), the diesel engine having a turbocharger (33) for delivering compressed air at boost pressure to an engine intake manifold (28). The apparatus delivers the secondary fuel to the engine intake downstream of the turbocharger. The apparatus includes a fuel line extending from a reservoir (10) for the secondary fuel to the engine intake manifold, a first valve (20,120) in said fuel line; and a biasing means (38) arranged to urge said first valve to an open configuration. The apparatus controls the flow rate of the secondary fuel dependent on the boost pressure.

Description

Fuel delivery apparatus and method

Field of the Invention

This invention relates to an apparatus and method for delivering secondary fuel to an engine, and in particular to a turbo-diesel engine.

Background of the Invention

Diesel engines have been used with a dual fuel system that uses diesel as a primary fuel together with a secondary fuel such as propane.

US Patent 6,422,015 discloses a propane injection system for a turbo- diesel engine in which a regulator valve responsive to boost pressure allows the continuous injection of propane into an engine air-inlet hose upstream of the turbocharger compressor. In the event of sparking within the compressor, the propane-rich atmosphere can lead to an explosion.

Summary of the Invention

It is an object of the present invention to substantially overcome or at least ameliorate one or more disadvantages of existing arrangements.

According to a first aspect of the invention there is provided an apparatus for delivering a secondary fuel to a diesel engine, the diesel engine having a turbocharger for delivering compressed air at boost pressure to an engine intake manifold, wherein the apparatus delivers the secondary fuel to the engine downstream of the turbocharger.

The apparatus may comprise a fuel line extending from a reservoir for the secondary fuel to the engine intake manifold;

a first valve in said fuel line; and

a biasing means arranged to urge said first valve to an open configuration, wherein in use said biasing means opposes a back pressure exerted through said fuel line from the engine intake manifold. The apparatus may comprise at least one control valve in said fuel line operable to vary a flow rate of the secondary fuel; and

control means that manipulates said control valve dependent on the boost pressure.

The apparatus may manipulate said control valve dependent on the boost pressure and a measured speed of the diesel engine.

According to another aspect of the invention there is provided a diesel engine comprising a fuel delivery apparatus for delivering a secondary fuel downstream of a turbocharger.

According to a further aspect of the invention there is provided a method of delivering a secondary fuel to a diesel engine, the diesel engine having a turbocharger for delivering compressed air at boost pressure to an engine intake manifold, wherein the method comprises:

injecting the secondary fuel into the engine intake manifold downstream of the turbocharger; and

varying a flow rate of the secondary fuel dependent on the boost pressure.

According to a further aspect of the invention there is provided an apparatus for delivering a secondary fuel to a diesel engine, the diesel engine including a turbocharger for delivering compressed air at boost pressure to an engine intake manifold, the apparatus comprising:

a regulator having an inlet communicating with a reservoir of secondary fuel and an outlet communicating with said engine intake manifold downstream of the turbocharger, the regulator adapted to control the supply of secondary fuel in a fuel line from the reservoir to the engine intake manifold, said regulator including a regulator valve for varying the flow rate of the secondary fuel continuously in response to variations in the boost pressure, and an adjustable biasing means arranged to increase the responsiveness of the regulator valve when opening in response to an increase in boost pressure via a boost pressure line.

Brief description of the drawings

Embodiments of the invention are described herein with reference to the drawings, in which:

Figure 1 shows a first embodiment of a fuel delivery apparatus for supplying a secondary fuel to a turbo diesel engine;

Figure 2 shows a partly schematic cross-sectional view of a regulator forming part of the apparatus of Figure 1 ;

Figure 3 shows a second embodiment of a fuel delivery apparatus having an electronic control unit;

Figure 4 shows a cross-sectional view of a regulator used in the apparatus of Figure 3;

Figure 5 shows an example of a look-up table for use by the electronic control unit of Figure 3; and

Figure 6 is a schematic block diagram illustrating the use of the look-up table by the electronic control unit.

Detailed description

Referring first to Figure 1 , a liquid fuel, for example liquid propane, is stored under pressure in an LPG tank or cylinder 10 and is delivered to an engine intake downstream of a turbocharger 33 by a fuel delivery apparatus 1.

The liquid propane is delivered via an outlet from the fuel tank or cylinder 10 through a first conduit 12 which forms part of a fuel inlet line. A heat exchanger 14 surrounds the first conduit 12, and converts the liquid propane into a gas at a temperature of approximately 4O⁰C. The fuel flows via a first lock-off valve 16 into a control module 18 via a second conduit 21 forming part of the fuel inlet line. The control module 18 comprises a regulator 20 (see Figure 2) and a delivery valve 22. The fuel passes through the regulator 20 into a third conduit 24 to the delivery valve 22. The fuel then passes through a fourth conduit 26 and is injected into an intake manifold 28 of a diesel engine 30 via a pair of variable size injectors 32, one of which is schematically illustrated in Figure 1. Both the third and fourth conduits 24, 26 also form part of the fuel inlet line. The size of the injectors 32 may be varied depending on the engine requirements, thereby allowing the engine to be infinitely tuneable.

Compressed air generated by a compressor of a turbocharger 33 flows into the inlet manifold of the engine 30 from an intercooler 31 which receives heated compressed air from the turbocharger 33. The fuel delivery apparatus of Figure 1 thus injects the secondary fuel downstream of the turbocharger 33.

Referring now to Figure 2, the regulator 20 has an inlet 34 that receives fuel via the second conduit 21 and an outlet 36 that feeds the secondary fuel to the third conduit 24. A compression spring 38 acts against a diaphragm 40 forming part of a diaphragm valve. A pre-set force is applied to the spring 38 via adjusting means such as an adjusting screw 39. The amount of pre-set force to be applied to the spring 38 depends on the amount of force required to keep the valve head 42 open during normal operation. In operation, the preset force allows the fuel to be continuously delivered to the engine 30 against back pressure exerted from the inlet manifold via the third and fourth conduits 24, 26. The spring 38 is a biasing means that may increase the responsiveness of the diaphragm to an increase in boost pressure via the boost pressure line, thereby avoiding a delay in opening whilst the boost pressure is building up against the diaphragm 40. This is typically between 3 and 15psi.

The force exerted by the spring may be variable. There are several ways in which this may be achieved. For example, the adjusting screw may be accessible so that the spring may be manually adjusted. Alternatively, the tension of the spring 38 may be determined by control means 190 (see Figure 4) such as a stepper motor and/or a worm drive. The control means 190 may be activated by a control signal. In one arrangement the control signal 169 may be provided from an electronic control unit 160, as shown in Figure 4. Alternatively, there may be a wireless communication enabling the control means 190 to be adjusted. For example, the regulator may include a radio- frequency link or a SIM card permitting remote communication. The spring 38 may be set when the fuel delivery apparatus 1 is being installed in the vehicle, but may also be adjusted during operation, for example by sending a control signal to cause the control means 190 to adjust the spring tension.

The valve head 42 is carried on and is directly responsive to movement of the diaphragm 40 and is movable along the axis of the spring 38 within the fuel outlet 36 from a "closed" position where the valve head 42 rests on a valve seat 44, to an "open" position, where fuel is able to flow from the inlet 34 to the outlet 36.

An inlet 46 to a control air line 48 is positioned above the diaphragm 40 in the valve chamber 41. The control air line 48 connects the regulator 20 to a pressure outlet 50 downstream of the turbocharger 33 and upstream of the intercooler 31 via an in-line boost pressure switch 52. In other arrangements the pressure outlet 50 may be positioned downstream of the intercooler 31. The boost pressure switch 52 stops the flow of fuel by sending a signal to the delivery valve 22 when the boost pressure drops below a pre-set manifold pressure, which is typically in the range of 1 to 6psi. In operation, boost air pressure from the intake manifold 28 is applied via the control air line 48 to the diaphragm 40 so that the fuel flow rate through the regulator 20 is varied continuously substantially in proportion to changes in the boost pressure.

In operation, the ignition 56 is switched on, and the dashboard mounted on/off gas switch 58 is then turned on. The heat exchanger 14 may be heated with engine coolant. When the heat exchanger reaches a pre-set temperature , typically between 30⁰C and 40°C after the engine has been turned on and has run for a period of time, the temperature switch 60, or alternatively the timer relay 61 delivers a signal to the boost pressure switch 52, via an LPG safety cut-out switch 62, which is activated by an alternator exciter wire that gives 12v or in some cases 24v when the vehicle is running. The lock-off valve 16 is powered up once the safety cut-out switch 62 has been activated. When the boost pressure in the manifold 28 reaches a pre-set pressure, typically in the range of 1 to 6psi, the boost pressure switch 52 sends a signal to the delivery valve 22 causing it to open. Thus, the delivery valve 22 will be opened when both the pre-set temperature and pre-set boost pressure have been reached. When the lock-off valve 16 and delivery valve 22 are open, fuel flows through the control module 18 and into the engine 30 via the injectors 32. As the boost pressure increases, pressure is transferred from the pressure outlet 50 to the regulator 20 via the control air line 48 to proportionally open the valve 42 in the manner described previously. When the boost pressure drops below the pre-set boost pressure, the boost pressure switch 52 is deactivated and the delivery valve 22 is closed and fuel ceases to flow to the engine 30. Provided the ignition 56 and the on/off switch 58 remain activated, the boost pressure switch 52 is directly responsive to an increase in boost pressure as the vehicle accelerates. When the ignition 56 and on/off switch 58 are switched off, the system automatically shuts down.

The on/off switch 58 allows the system to be turned on or off while the engine is running. If the system is turned on while the engine is running, power will not be instantly switched to the lock-off valve 16 and delivery valve 22. Rather, the same sequence as for a cold start is initiated. Fuel ceases to flow if the engine stops running, as both the lock-off and delivery valves are connected to the ignition.

Second embodiment

Figures 3 and 4 show a fuel delivery system 100 for injecting secondary fuel into an engine downstream of a turbocharger 33. In this arrangement the flow of the secondary fuel is controlled by a variable solenoid valve 130. The valve 130 may be manipulated dependent on the pressure in the manifold 28. The operation of the valve may also depend on the engine's revolutions per minute (RPM). As in the arrangement of Figure 1 , the liquid secondary fuel is fed to a first conduit 12 from a storage tank. Heat exchanger 14 acts to convert the fuel to a gas. The temperature of the heat exchanger may be monitored by a thermostat 106. A first lock-off valve 16 is operable to close off the first conduit 12 or else permit the fuel to flow through to a second conduit 21 , which leads to a regulator 120. As described below with reference to Figure 4, the regulator 120 has a biasing means that acts to keep the valve 42, 44 open, even in the presence of back pressure, for instance deriving from the pressure within the inlet manifold.

From the regulator, a third conduit 24 communicates with the solenoid valve 130 that may be manipulated to control the flow of secondary fuel through the third conduit 24. In one arrangement the valve 130 is a pulsed solenoid valve that is driven by a square wave signal 166 in which the width of the pulses is modulated. The duty cycle of the signal 166 determines the proportion of time during which the valve is open, and hence varies the flow of fuel. It will be understood that other types of controllable valve may also be used.

A gas reservoir 140 may be provided at the output of the valve 130, integrating the gas flow to give a smoothed flow rate into a fourth conduit 126. The fourth conduit 126 is the last link of a fuel inlet line that leads to the injectors or nozzles 32, which inject the secondary fuel into the manifold 28 downstream of the turbocharger 33.

Pressure sensor 150 measures the pressure in the manifold 28. The sensor 150 is located at the pressure outlet 50, which is downstream of the turbocharger 33. The sensor 150 generates a voltage signal 164, for example in the range 0 to 5 V, that is indicative of the pressure at the pressure outlet 50. The voltage signal 164 is provided to an electronic control unit (ECU) 160 that controls the provision of secondary fuel.

The ECU 160 generates a voltage signal 166 that specifies a desired duty cycle for the solenoid valve 130. The ECU 160 may also receive a voltage signal 162 from a tachometer that measures the engine's revolutions per minute (RPM). As described below, the duty cycle of valve 130 may be varied as a function of both engine speed and manifold pressure.

The ECU 160 also receives an input signal 108 from the thermostat 106 that measures the temperature of the heat exchanger 14. In one arrangement the ECU 160 is activated if the thermostat 106 reaches a specified temperature, for example 4O⁰C. If the temperature has reached the setpoint (indicated by signal 108) and the manifold pressure has reached a minimum threshold (indicated by signal 164), then the ECU 160 sends a signal 168 to cause the lock-off valve 16 to open. The ECU 160 also acts to manipulate the solenoid valve 130 as a function of the manifold pressure and/or the measured RPM.

The ECU may be a dedicated circuit used to control the secondary fuel injection system. The ECU may, for example, be an integrated circuit including a microcontroller or microprocessor. The ECU 160 may also be implemented using analogue electronic components. Alternatively, the functions of the ECU 160 may be programmed into an on-board computer system for the vehicle containing the diesel engine 30.

The system of Figure 3 also includes a fuel level sensor 110.

Figure 4 shows a cross-section of the regulator 120, which includes a valve head 42 that cooperates with valve seat 44. Fuel enters through inlet 34 and exits through outlet 36 if the valve is open. Diaphragm 40 is movable to adjust the position of the valve head 42. Compression spring 38 provides a biasing means that acts on the diaphragm 40, urging the valve head 42 into an open position. The spring 38 thus counteracts back pressure at the outlet 36 which would otherwise act to close the valve. The force of the spring 38 may be pre-set, for example by adjusting screw 39, and may be varied to meet different engine requirements. Biasing the regulator assists in enabling the injection of secondary fuel downstream of the turbocharger 33. As described above with reference to Figure 2, the force provided by the biasing means may be adjustable. For example, a control means 190 such as a stepper motor may determine the setting of the spring 38 and the stepper motor may be controlled by a control signal 169 from the ECU 160.

In the arrangement shown in Figure 4, the manifold pressure is not fed back to the valve chamber 41 as is the case in regulator 20 seen in Figure 2.

However, alternative implementations of the fuel delivery system 100 may use regulator 20, ie both the regulator and the valve 130 may be adjusted dependent on the manifold pressure.

There are various ways in which the ECU 160 can generate the control signal 166 for valve 130. For example, a proportional or proportional-integral controller may operate on the pressure measurement 164 and/or the RPM signal 162 to generate signal 166. This is illustrated schematically in Figure 6, which shows two inputs 162, 164 into the ECU 160 and an output 166 sent to the valve 130.

One method that may be used with the functional arrangement of

Figure 6 uses a look-up table to find a suitable value for the control signal 166. An example of the look-up table 200 is shown in Figure 5. The table 200 is a two-dimensional array in which one axis 204 represents engine RPM and the other axis 202 represents manifold pressure. Given an input pressure and RPM value, the ECU 160 reads the value for signal 166 at the intersection of the appropriate row and column of table 200. For example, for an RPM value of 1500 and a pressure of 50%, the table 200 specifies a value of 6. The ECU 160 outputs the value to set the duty cycle of the solenoid valve 130.

The table 200 specifies a relative weighting of the two input values. For example, if the manifold pressure increases from 60% to 80% but the RPM measurement falls from 2000 to 500, then the duty cycle of the valve is reduced from 8 to 5. The drop in engine speed may indicate that the driver is decelerating. It will be appreciated that the table 200 is one example of an algorithm for controlling the valve 130. Different tables may be used, for example for engines of different capacity, and other control methods may also be used.

The described system advantageously enables the secondary fuel to be delivered downstream of the turbocharger. Consequently, the secondary fuel may be delivered to the engine without filling the turbocharger, associated piping and, in most cases, the intercooler, with a potentially explosive mixture of fuel vapour and air.

Where in the foregoing description reference has been made to integers having known equivalents, then those equivalents are hereby incorporated herein as if individually set forth.

It will be appreciated that the apparatus and method relates to the delivery of secondary fuel and is not limited to the delivery of LPG/LNG/CNG or Hydrogen to diesel engines. The illustrated embodiments use a heat exchanger 14 to convert a liquid fuel to a gaseous form. In other arrangements the fuel delivery systems 1 and 100 may be used without a heat exchanger to deliver liquid fuel. In some arrangements the fuel may be injected into the intake upstream of the manifold and downstream of the turbocharger.

The fuel delivery system 100 may be used for naturally-aspirated engines where a secondary fuel is delivered between an air-box and the engine manifold. In the case of naturally-aspirated engines the ECU 160 may control the flow rate of secondary fuel as a function of the engine speed (indicated by signal 162).

Those skilled in the relevant arts will appreciate that modifications and additions to the embodiments of the present invention may be made without departing from the scope of the present invention.

It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.

Claims

Claims:

1. An apparatus for delivering a secondary fuel to a diesel engine, the diesel engine having a turbocharger for delivering compressed air at boost pressure to an engine intake manifold, wherein the apparatus delivers the secondary fuel to the engine downstream of the turbocharger.

2. An apparatus according to claim 1 , wherein the apparatus comprises:

a fuel line extending from a reservoir for the secondary fuel to the engine intake manifold;

a first valve in said fuel line; and

a biasing means arranged to urge said first valve to an open configuration, wherein in use said biasing means opposes a back pressure exerted through said fuel line from the engine intake manifold.

3. An apparatus according to claim 1 or 2 comprising:

at least one control valve in said fuel line operable to vary a flow rate of the secondary fuel; and

4. An apparatus according to claim 3 wherein the first valve is the control valve and wherein said control means comprises a boost-pressure line providing fluid communication between the engine intake manifold and a valve chamber of said first valve such that the first valve is adjusted in the fuel line dependent on variations in a pressure within the valve chamber.

5. An apparatus according to claim 4 wherein said biasing means is arranged to supplement the pressure in the valve chamber to which the first valve is responsive.

6. An apparatus according to claim 3 wherein said control means manipulates said control valve dependent on the boost pressure and a measured speed of the diesel engine.

7. An apparatus according to claim 6 wherein said control means comprises a look-up table that defines a control value for said control valve.

8. An apparatus according to claim 7 wherein the control value specifies a duty cycle of a pulse-width modulated signal that said control unit communicates to said control valve.

9. An apparatus according to any one claims 2 to 8 further comprising:

at least one lock-off valve in said fuel line, the apparatus arranged to close said lock-off valve if the boost pressure is less than a low threshold.

10. An apparatus according to any one of claims 2 to 9 further comprising:

a heat exchanger that in use heats at least a portion of said fuel line to convert the secondary fuel from a liquid state to a gaseous state.

11. An apparatus according to claim 10 when dependent on claim 9, wherein the apparatus is arranged to close said lock-off valve if a measured temperature of said heat exchanger is less than a specified temperature threshold.

12. An apparatus according to claim 3 comprising a gas reservoir in the fuel line between said control valve and the engine intake manifold, wherein in use the gas reservoir smooths an output flow from said control valve.

13. An apparatus according to claim 2 wherein said biasing means comprises an adjustable compression spring.

14. An apparatus according to claim 2 comprising adjustment means to adjust a force exerted by said biasing means.

15. An apparatus according to claim 14 wherein said adjustment means comprises at least one of a stepper motor and a worm drive.

16. An apparatus according to claim 14 or 15 comprising a wireless communication means operable to receive a signal to activate said adjustment means.

17. An apparatus for delivering a secondary fuel to a diesel engine, the diesel engine including a turbocharger for delivering compressed air at boost pressure to an engine intake manifold, the apparatus comprising:

18. A diesel engine having a turbocharger for delivering compressed air at boost pressure to an engine intake manifold of the engine, and comprising the apparatus of any one of claims 1 to 17.

19. A method of delivering a secondary fuel to a diesel engine, the diesel engine having a turbocharger for delivering compressed air at boost pressure to an engine intake manifold, wherein the method comprises:

varying a flow rate of the secondary fuel dependent on the boost pressure.

20. A method according to claim 19 further comprising:

varying the flow rate of the secondary fuel dependent on a measured rotational speed of the diesel engine.

21. A method according to claim 20 wherein varying the flow rate comprises:

measuring the rotational speed of the diesel engine;

measuring the boost pressure;

consulting a two-dimensional look-up table to obtain a control value dependent on the measured speed and pressure; and

manipulating a control valve dependent on the control value, the control valve located in a fuel line extending from a reservoir for the secondary fuel to the engine intake manifold.

22. A method according to claim 19 wherein the secondary fuel flows through a first valve located in a fuel line extending from a reservoir for the secondary fuel to the engine intake manifold and the method comprises:

providing a biasing means to urge the first valve to an open configuration, wherein in use the biasing means opposes a back pressure exerted through the fuel line from the engine intake manifold.