Method and system for determining knock control fluid composition

Patent metadata

Field	Value
Publication number	US-10316798-B2
Application number	US-201514918475-A
Country	US
Kind code	B2
Filing date	Oct 20, 2015
Priority date	Oct 20, 2015
Publication date	Jun 11, 2019
Grant date	Jun 11, 2019

Abstract

Methods and systems are provided for accurately determining the composition of a knock control fluid using sensors already present in the engine system. An intake or an exhaust oxygen sensor is used to estimate the water and the alcohol content of a knock control fluid that is direct injected into an engine cylinder responsive to an indication of abnormal combustion. A change in the pumping current of the oxygen sensor due to the water content of the knock control fluid is distinguished from a change in the pumping current of the oxygen sensor due to the alcohol content of the knock control fluid.

First claim

The invention claimed is:

1. An engine method, comprising:
injecting an amount of a water-alcohol blend;
applying a reference voltage to an intake oxygen sensor;
monitoring a change in pumping current of the sensor;
learning a first portion of the change in pumping current due to a water content of the blend; and
learning a second portion of the change in pumping current due to an alcohol content of the blend.

2. The method of claim 1 , further comprising learning a composition of the blend based on the learned first portion and second portion, and further based on the injection amount.

3. The method of claim 2 , further comprising adjusting an engine operating parameter based on the learned composition, the engine operating parameter including one or more of a fuel octane estimate and a fuel injection amount.

4. The method of claim 1 , wherein the blend includes no gasoline and wherein the alcohol content includes one or more of ethanol and methanol.

5. The method of claim 1 , wherein the applying includes applying a first lower voltage that does not dissociate water molecules.

6. The method of claim 1 , wherein learning the first portion includes determining a first value of a methanol-to-water concentration in the blend.

7. The method of claim 6 , wherein learning the second portion includes:
determining a second value of the methanol-to-water concentration in the blend that is learned based on the monitored change in pumping current and further based on the amount of water-alcohol blend injected, the second value reflecting a base concentration of oxygen in the ambient air; and
comparing the first value to the second value.

8. The method of claim 1 , wherein the method is performed responsive to selected conditions being identified, the selected conditions include following refilling of the water-alcohol blend in a reservoir.

9. The method of claim 1 , wherein the water-alcohol blend includes one of wiper fluid and engine coolant.

10. An engine system, comprising:
an engine including an intake manifold;
a first injector for injecting fuel into an engine cylinder;
a second injector for injecting a knock control fluid into the intake manifold, downstream of an intake throttle;
an EGR system including a passage for recirculating exhaust residuals from downstream of a turbine to upstream of a compressor via an EGR valve;
an oxygen sensor coupled to the intake manifold, downstream of the intake throttle and downstream of the EGR valve; and
a controller with computer readable instructions stored on non-transitory memory for:
injecting an amount of the knock control fluid into the cylinder;
applying a lower reference voltage to the oxygen sensor;
measuring a change in pumping current of the oxygen sensor; and
estimating a composition of the knock control fluid based on the injection amount and the measured change in pumping current.

11. The system of claim 10 , wherein the knock control fluid includes water and alcohol and no fuel, and wherein the controller estimates the composition by calculating a first portion of the change in pumping current due to a water content of the knock control fluid and calculating a second portion of the change in pumping current due to an alcohol content of the knock control fluid.

12. The system of claim 10 , wherein the controller includes further instructions for:
updating a fuel octane estimate based on the estimated composition of the knock control fluid.

13. The system of claim 12 , wherein the controller includes further instructions for:
adjusting each of a spark timing and a borderline spark value applied responsive to knock based on the updated fuel octane estimate, the adjusting including retarding spark timing from a base spark timing, and advancing borderline spark towards MBT as the fuel octane estimate increases.

Assignees

• Ford Global Tech Llc

Inventors

• Hakeem Mohannad
• Surnilla Gopichandra

Classifications

• F02D19/12 Primary

  peculiar to engines working with non-fuel substances or with anti-knock agents, e.g. with anti-knock fuel · CPC title

• F02D19/0634

  Determining a density, viscosity, composition or concentration (F02D19/087 takes precedence) · CPC title

• F02D19/084

  Blends of gasoline and alcohols, e.g. E85 · CPC title

• F02D19/0649

  Liquid fuels having different boiling temperatures, volatilities, densities, viscosities, cetane or octane numbers · CPC title

• F02M25/0227 Primary

  Control aspects; Arrangement of sensors; Diagnostics; Actuators · CPC title