Method for controlling fuel pressure for a LPG engine

Patent metadata

Field	Value
Publication number	US-9702307-B2
Application number	US-201314019445-A
Country	US
Kind code	B2
Filing date	Sep 5, 2013
Priority date	Sep 5, 2013
Publication date	Jul 11, 2017
Grant date	Jul 11, 2017

Abstract

Methods and systems are provided for adjusting a phase of gaseous fuel delivered to fuel injectors of a fuel delivery system. In one example, a method may include adjusting a fuel pressure in a fuel delivery system to deliver fuel in each of a liquid and a gaseous phase during different engine operating conditions. The fuel pressure may be based on a temperature, composition, and desired phase of the fuel.

First claim

The invention claimed is:

1. A method for controlling an engine, comprising:
adjusting a fuel pressure of fuel in a fuel delivery system downstream of a fuel pump by adjusting a fuel pump output pressure to change a phase of the fuel downstream of the fuel pump, and selectively delivering the fuel which has been changed in phase downstream of the fuel pump to fuel injectors in each of a liquid phase and a gaseous phase during different engine operating conditions, the fuel pressure adjusted based on a temperature of the fuel and a desired phase of the fuel,
wherein adjusting the fuel pressure includes adjusting operation of the fuel pump in the fuel delivery system to deliver fuel to the fuel injectors at the fuel pressure by adjusting the pump output pressure via a pressure control valve, and
wherein the fuel is liquefied petroleum gas (LPG) and the LPG is stored in a single fuel tank in the liquid phase, the method further comprising, responsive to transitioning the fuel between phases, adjusting a fuel injection pulse width for a period to account for the fuel being a mixture of gaseous and liquid phases.

2. The method of claim 1 , wherein adjusting the fuel pressure includes increasing the fuel pressure above a threshold pressure to transition from delivering the fuel to the fuel injectors in the gaseous phase to delivering the fuel to the fuel injectors in the liquid phase.

3. The method of claim 2 , wherein adjusting the fuel pressure includes decreasing the fuel pressure below the threshold pressure to transition from delivering the fuel to the fuel injectors in the liquid phase to the gaseous phase, the threshold pressure based on the fuel pressure for the temperature of the fuel at which the fuel transitions between the liquid phase and the gaseous phase and a composition of the fuel.

4. The method of claim 1 , wherein the fuel pressure is further based on temperature and pressure of an engine cylinder, the temperature and pressure of the engine cylinder being one of a measured temperature and pressure or an estimated temperature and pressure based on charge air temperature, air charge and cylinder volume derived from crankshaft position, and piston position relative to the crankshaft position.

5. The method of claim 1 , further comprising adjusting the fuel pressure to deliver fuel to the fuel injectors in the liquid phase in response to a charge air temperature determined to be above a threshold temperature.

6. The method of claim 1 , further comprising adjusting the fuel pressure to deliver fuel to the fuel injectors in the gaseous phase in response to one or more of an engine temperature determined to be below a threshold temperature, an engine speed determined to be below a threshold speed, or an engine load determined to be below a threshold load.

7. The method of claim 1 , further comprising adjusting an amount of fuel injected into an engine cylinder based on the fuel pressure and whether the fuel is injected in the gaseous phase or the liquid phase.

8. The method of claim 1 , wherein the fuel injection pulse width is larger for fuel that is in the gaseous phase than for fuel that is in the liquid phase.

9. An engine control method, comprising:
during a first condition, adjusting a fuel pump output pressure to increase fuel pressure downstream of a fuel pump to change a phase of fuel downstream of the fuel pump from a second phase to a first phase and deliver fuel to a fuel injector in the first phase;
during a second condition, adjusting the fuel pump output pressure to decrease fuel pressure downstream of the fuel pump to change the phase of fuel downstream of the fuel pump from the first phase to the second phase and deliver the fuel to the fuel injector in the second phase, the second phase different from the first phase; and
adjust a fuel injection pulse width during each transition from the first phase to the second phase, and the second phase to the first phase, while fuel injected is a mixture of the phases.

10. The method of claim 9 , wherein the first phase is a gaseous phase and the second phase is a liquid phase, and wherein adjusting the fuel pump output pressure includes adjusting a pressure valve coupled to the pump.

11. The method of claim 10 , wherein the first condition includes one or more of a cold start condition, conditions requiring increased mixing in a combustion chamber, or conditions requiring complete combustion.

12. The method of claim 10 , wherein the second condition includes one or more of conditions requiring increased charge air cooling or conditions with an increased likelihood of engine knock.

13. The method of claim 10 , further comprising transitioning from the first phase to the second phase by adjusting the fuel pump to increase a fuel delivery pressure, the transitioning from the first phase to the second phase responsive to a charge air temperature greater than a threshold temperature, the threshold temperature based on a temperature increasing likelihood for engine knock.

14. The method of claim 10 , further comprising transitioning from the second phase to the first phase by adjusting the fuel pump to decrease a fuel delivery pressure, the transitioning from the second phase to the first phase responsive to one or more of a cold start condition, an engine speed, or a decreased engine load.

15. The method of claim 9 , wherein adjusting the fuel pump to deliver fuel in the first phase includes adjusting the fuel pump to deliver fuel at a first fuel delivery pressure, the first fuel delivery pressure based on the first phase and a temperature of the fuel and further comprising adjusting the first fuel delivery pressure based on cylinder temperature and pressure.

16. The method of claim 9 , wherein adjusting the fuel pump to deliver fuel in the second phase includes adjusting the fuel pump to deliver fuel at a second fuel delivery pressure, the second fuel delivery pressure based on the second phase and a temperature of the fuel and further comprising adjusting the second fuel delivery pressure based on cylinder temperature and pressure.

17. The method of claim 9 , wherein the fuel is stored in a fuel tank that is a single fuel tank for a fuel system, wherein the fuel tank contains liquefied petroleum gas (LPG), and wherein the fuel injector is one or more of a direct fuel injector or a port fuel injector.

18. A system for an engine, comprising:
an engine cylinder;
a first fuel injector coupled directly to the engine cylinder for injecting fuel into the engine cylinder;
a fuel delivery system coupled to the engine cylinder via the first fuel injector, the fuel delivery system including a single fuel tank and a fuel pump configured to adjust a fuel delivery pressure; and
a controller with computer readable instructions for adjusting the fuel pump to deliver fuel in a first phase at a first fuel delivery pressure during a first set of engine operating conditions and adjusting the fuel pump to deliver fuel in a second phase at a second fuel delivery pressure during a different, second set of engine operating conditions, the first fuel delivery pressure and the second fuel delivery pressure based on a temperature of the fuel and respective phase of the fuel, and for adjusting a fuel injection pulse width during each transition from the first phase to the second phase, and the second phase to the first phase, the fuel injected being a mixture of the phases during transitions.

19. The system of claim 18 , further comprising a second fuel injector coupled to a port of the engine cylinder for i

Assignees

• Ford Global Tech Llc

Inventors

• Glugla Chris Paul
• Surnilla Gopichandra
• Curtis Eric Warren
• Hedges John
• Dearth Mark Allen

Classifications

• F02D2200/0606

  Fuel temperature · CPC title

• F02D2200/0602

  Fuel pressure · CPC title

• F02D41/3845

  by controlling the flow into the common rail, e.g. the amount of fuel pumped · CPC title

• F02D41/0027

  the fuel being gaseous (non-electrical control F02D19/02) · CPC title

• F02D41/0025 Primary

  Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures · CPC title