Methods for determining fuel bulk modulus in a high-pressure pump

Patent metadata

Field	Value
Publication number	US-9243598-B2
Application number	US-201414189946-A
Country	US
Kind code	B2
Filing date	Feb 25, 2014
Priority date	Feb 25, 2014
Publication date	Jan 26, 2016
Grant date	Jan 26, 2016

Abstract

Methods are provided for finding the bulk modulus of a fuel used in the direct injection system of an internal combustion engine. A method is needed to continuously monitor and reliably calculate the fuel's bulk modulus during engine operation on-board the vehicle, where the fuel's bulk modulus may be used to infer the ratio of fuels in a fuel mixture or determine the density of supercritical propane when propane is used as the injected fuel. To find the fuel's bulk modulus on-board a vehicle, methods are proposed that involve monitoring and recording fuel rail pressures, high pressure pump duty cycles, and fractional liquid volume pumped values in order to find zero flow relationships.

First claim

The invention claimed is:

1. A method, comprising:
adjusting duty cycle of a high pressure pump to measure a bulk modulus of a fuel based on a zero flow function for the high pressure pump, the fuel being pumped through the high pressure pump and the zero flow function based on a change in pump duty cycle relative to a resulting change in fuel rail pressure.

2. The method of claim 1 , wherein determining the zero flow function for the high pressure fuel pump includes:
while not direct injecting fuel into an engine and while the engine is in a stabilized idling condition, commanding a first pump duty cycle;
waiting until fuel rail pressure reaches a steady-state value and then determining a first fuel rail pressure;
then commanding a second, higher pump duty cycle and determining a second fuel rail pressure; and
continue increasing pump duty cycle incrementally and determining fuel rail pressure until an upper duty cycle threshold is reached.

3. The method of claim 1 , wherein determining the zero flow function for the high pressure fuel pump includes:
while direct injecting fuel into an engine to maintain a positive fuel flow rate, commanding a multitude of pump duty cycles corresponding to a multitude of fuel rail pressures and determining a responsive fractional volume of liquid fuel pumped, thereby forming a dataset, wherein the dataset comprises a multitude of operating points, each operating point consisting of a duty cycle, fuel rail pressure, and fractional volume pumped; and
determining a multitude of horizontal-axis intercepts that correspond to zero flow rate data based on a known line slope.

4. The method of claim 3 , wherein the known line slope is a slope of the dataset, wherein a vertical axis is fractional liquid fuel volume pumped and a horizontal axis is pump duty cycle.

5. The method of claim 1 , wherein high pressure pump duty cycle is a measure of a closing time of a solenoid activated check valve that controls an amount of fuel pumped into the fuel rail by the high pressure pump.

6. The method of claim 5 , wherein any reduced current of the solenoid activated check valve is disabled.

7. The method of claim 1 , wherein the high pressure fuel pump ingests liquid fuel with no fuel vapor.

8. The method of claim 1 , wherein the fuel is a mixture of ethanol and gasoline, a mixture of propane and gasoline, or liquid propane.

9. An engine system, comprising:
an engine;
a direct fuel injector configured to direct inject fuel into the engine;
a fuel rail fluidly coupled to the direct fuel injector;
a high pressure fuel pump fluidly coupled to the fuel rail;
a controller with computer readable instructions stored in non-transitory memory for:
adjusting duty cycle of a high pressure pump to measure a bulk modulus of a fuel based on a zero flow function for the high pressure pump, the fuel being pumped through the high pressure pump and the zero flow function based on a change in pump duty cycle relative to a resulting change in fuel rail pressure.

10. The engine system of claim 9 , wherein determining the zero flow function for the high pressure fuel pump includes:
while not direct injecting fuel into an engine and while the engine is in a stabilized idling condition, commanding a first pump duty cycle;
waiting until fuel rail pressure reaches a steady-state value and then determining a first fuel rail pressure;
then commanding a second, higher pump duty cycle and determining a second fuel rail pressure; and
continue increasing pump duty cycle incrementally and determining fuel rail pressure until an upper duty cycle threshold is reached.

11. The engine system of claim 9 , wherein determining the zero flow function for the high pressure fuel pump includes:
while direct injecting fuel into an engine to maintain a positive fuel flow rate, commanding a multitude of pump duty cycles corresponding to a multitude of fuel rail pressures and determining a responsive fractional volume of liquid fuel pumped, thereby forming a dataset, wherein the dataset comprises a multitude of operating points, each operating point consisting of a duty cycle, fuel rail pressure, and fractional volume pumped; and
determining a multitude of horizontal-axis intercepts that correspond to zero flow rate data based on a known line slope.

12. The engine system of claim 11 , wherein the known line slope is a slope of the dataset, wherein a vertical axis is fractional liquid fuel volume pumped and a horizontal axis is pump duty cycle.

13. The engine system of claim 9 , wherein high pressure pump duty cycle is a measure of a closing time of a solenoid activated check valve that controls an amount of fuel pumped into the fuel rail by the high pressure pump.

14. The engine system of claim 13 , wherein any reduced current of the solenoid activated check valve is disabled.

15. The engine system of claim 9 , wherein the high pressure fuel pump ingests liquid fuel with no fuel vapor.

16. The engine system of claim 9 , wherein the fuel is a mixture of ethanol and gasoline, a mixture of propane and gasoline, or liquid propane.

17. A method, comprising:
while not direct injecting fuel into an engine via a high pressure pump and while the engine is in a stabilized idling condition, determining a relationship between high pressure pump duty cycle and fuel rail pressure; and
finding a slope from the relationship to determine a bulk modulus of a fuel.

18. The engine method of claim 17 , wherein determining the relationship includes:
incrementally increasing pump duty cycle and waiting for a period of time before measuring a responsive fuel rail pressure for each pump duty cycle; and
continue incrementally increasing pump duty cycle until an upper threshold duty cycle is reached.

19. An engine method, comprising:
while direct injecting fuel into an engine to maintain a positive fuel flow rate, determining a relationship between high pressure pump duty cycle and fuel rail pressure; and
finding a slope from the relationship to determine a bulk modulus of a fuel.

20. The engine method of claim 19 , wherein determining the relationship further comprises:
selecting a multitude of operating points, each operating point including a pump duty cycle and a fuel rail pressure that correspond to a fractional fuel volume pumped;
regressing each operating point to find a multitude of intersections with a horizontal axis; and
plotting the intersections on a graph.

21. The engine method of claim 20 , wherein regressing each operating point involves finding a slope of a line based on pump duty cycle and fractional fuel volume pumped.

Assignees

• Ford Global Tech Llc

Inventors

• Pursifull Ross Dykstra
• Surnilla Gopichandra
• Zhang Hao
• Meinhart Mark
• Basmaji Joseph F

Classifications

• F02M65/002 Primary

  Measuring fuel delivery of multi-cylinder injection pumps · CPC title

• F02D2200/0612

  determined by estimation · 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

• F02D2200/0602

  Fuel pressure · CPC title

• F02D41/0027

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