Techniques for mitigating low-speed pre-ignition conditions in an engine and a fuel delivery system using the same

Patent metadata

Field	Value
Publication number	US-9797334-B2
Application number	US-201615006489-A
Country	US
Kind code	B2
Filing date	Jan 26, 2016
Priority date	Jan 26, 2016
Publication date	Oct 24, 2017
Grant date	Oct 24, 2017

Abstract

Aspects and embodiments disclosed herein indicate a correlation exists between a specific gravity of combustible fuel and the occurrence of low-speed pre-ignition (LSPI) within engines. Thus techniques are disclosed herein for online measurement of the specific gravity of fuel within an engine, and allow for preventative measures to be executed to minimize or otherwise mitigate the incidence of LSPI when the calculated specific gravity of the fuel exceeds a predefined threshold. In an embodiment, the preventative measures may include, for example, altering or otherwise adjusting an engine map such that an injection timing scheme injects less poor-quality fuel into engine cylinders, thus advantageously preventing the engine from operating at full-power when conditions for LSPI are present.

First claim

What is claimed is:

1. A method for determining conditions giving rise to low-speed pre-ignition events in an engine, the method comprising:
receiving, by a controller, a first and second fuel pressure measurement, the first and second fuel pressure measurement corresponding to a high pressure region and a low pressure region, respectively;
determining, by the controller, a pressure differential based on the difference between the second fuel pressure measurement and the first fuel pressure measurement;
calculating, by the controller, a specific gravity value based in part on the determined pressure differential; and
detecting, by the controller, a condition giving rise to low-speed pre-ignition events in response to the calculated specific gravity value exceeding a predefined threshold.

2. The method of claim 1 , wherein the high pressure region and the low pressure region are within a fuel return line, and wherein a first end of the fuel return line is fluidly coupled to an outlet of a fuel rail, and wherein a second end of the fuel return line is fluidly coupled to a solenoid control valve, and wherein the method further comprises:
actuating the solenoid control valve to pass fuel through an orifice for measurement purposes.

3. The method of claim 2 , wherein actuating the solenoid control valve is in response to the controller receiving a measurement interrupt signal.

4. The method of claim 3 , wherein the measurement interrupt signal is generated based on detecting de-acceleration of the engine.

5. The method of claim 2 , wherein the specific gravity for the fuel is calculated based at least in part on the following equation:

1
p

=

(

Q

CA
2

)

2

2
⁢

(

P
1

-

P
2

)

wherein (Q) is volumetric flowrate at any cross-section (m 3 /s) of the fuel return line, (C) is a orifice flow coefficient of the orifice, (A 2 ) is a cross-sectional area of a hole of the orifice, (P 1 ) is the first fuel pressure measurement, (P 2 ) is the second fuel pressure measurement, and

(

1
p

)

is the specific gravity of the fuel.

6. The method of claim 1 , the method further comprising:
de-rating the engine in response to the calculated specific gravity value exceeding a predefined threshold, wherein de-rating the engine includes adjusting an engine map, and wherein the adjusted engine map causes a fuel injection scheme implemented by the engine to inject relatively less fuel into cylinders at least during engine speeds under 3000 rotations per minute than when using an unmodified engine map.

7. A direct injection system comprising:
a fuel pump fluidly coupled to a fuel supply;
a fuel return line;
a fuel rail having an inlet fluidly coupled to the fuel pump and an outlet fluidly coupled to the fuel return line, the fuel rail being configured to provide a first portion of fuel to a plurality of fuel injectors, and provide a second portion of fuel to the fuel return line;
an orifice disposed within the fuel return line and configured to pass fuel and introduce a measurable pressure difference such that a first pressure is provided before fuel passes through the orifice and a second pressure is provided downstream of the orifice;
a first pressure sensor configured to measure the first pressure;
a second pressure sensor configured to measure the second pressure;
circuitry electrically coupled to the first and second pressure sensors and configured to:
determine a pressure differential based on a difference between the second measured pressure and the first measured pressure;
calculate a specific gravity value for the second portion of fuel based in part on the determined pressure differential; and
detecting a condition giving rise to low-speed pre-ignition events in response to the specific gravity value exceeding a predefined threshold.

8. The direct injection system of claim 7 , wherein the circuitry is further configured to de-rate an engine in response to detecting the condition giving rise to low-speed preignition events.

9. The direct injection system of claim 7 , wherein the predefined threshold equals about 0.76.

10. The direct injection system of claim 8 , wherein the circuitry de-rates an engine at least in part by causing an engine map to be adjusted, wherein the adjusted engine map causes a fuel injection scheme implemented by an engine control unit to inject relatively less fuel into cylinders at least during engine speeds under 3000 rotations per minute than when using an unmodified engine map.

11. The direct injection system of claim 7 , further comprising a solenoid control valve disposed along the fuel return line prior to the orifice and configured to inhibit flow of fuel when de-actuated and allow flow of fuel when actuated, and wherein the circuitry is further configured to:
actuate, in response to receiving a measurement interrupt signal, the solenoid control valve by providing an electrical signal to the solenoid control valve.

12. The direct injection system of claim 11 , wherein the measurement interrupt signal is generated as a result of an engine control unit detecting engine de-acceleration.

13. The direct injection system of claim 7 , wherein the fuel return line is fluidly coupled to the fuel supply such that fuel passing through the orifice is returned to the fuel supply.

14. The direct injection system of claim 7 , wherein the first pressure sensor is a fuel rail pressure sensor fixedly attached to the fuel rail.

15. The direct injection system of claim 7 , wherein the specific gravity for the fuel is calculated based at least in part on the following equation:

1
p

=

(

Q

CA
2

)

2

2
⁢

(

P
1

-

P
2

)

Assignees

• Southwest Res Inst

Inventors

• Anderson Garrett L
• Briggs Jr Thomas E

Classifications

• F02D2041/389

  for injecting directly into the cylinder · CPC title

• F02M55/025

  Common rails · CPC title

• F02D41/3863 Primary

  by controlling the flow out of the common rail, e.g. using pressure relief valves · CPC title

• F02D41/26

  using computer, e.g. microprocessor · CPC title

• F02D41/045

  Detection of accelerating or decelerating state (detection thereof in general G01P) · CPC title