Method for measuring recirculated exhaust gas flow in a compression-ignition engine

• US 6,588,210 B2
• Filed: 12/06/2001
• Issued: 07/08/2003
• Est. Priority Date: 03/31/2000
• Status: Expired due to Term

• Current Assignee: Detroit Diesel Corporation (Daimler Truck Holding AG)
• Original Assignee: Detroit Diesel Corporation (Daimler Truck Holding AG)
• Inventors: Kreso, Admir M.
• Primary Examiner(s): NGUYEN, HOANG M
• Application Number:
  US10/010,089
• Publication Number:
  US 20020059797A1
• Time in Patent Office: 579 Days
• Field of Search: 606/00, 606/01, 606/02, 606/03, 606/051, 606/052
• US Class Current: 60/602
• CPC Class Codes: F02B 37/24 by using pumps or turbines with adjustable guide vanes
• CPC Class Codes: F02D 2041/0067 Determining the EGR temperature
• CPC Class Codes: F02D 2200/0406 Intake manifold pressure
• CPC Class Codes: F02D 2200/0414 Air temperature
• CPC Class Codes: F02D 41/0072 Estimating, calculating or determining the EGR rate, amount or flow sensors in EGR systems F02M26/45
• CPC Class Codes: G01F 1/36 the pressure or differential pressure being created by the use of flow constriction
• CPC Class Codes: G01F 1/42 Orifices or nozzles
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A system and method for measuring the flow rate of recirculated exhaust gas in a compression ignition engine including a plurality of engine sensors having outputs indicative of current engine conditions and a turbocharger. The system includes an exhaust gas recirculation (EGR) valve mounted in the exhaust pipe upstream of the turbocharger for diverting a selectable portion of the exhaust gas for recirculation and combination with the charge air, one or more sensors for sensing current conditions of the recirculated exhaust gas, including temperature and pressure, one or more sensors for sensing current conditions of the intake air, and control logic for determining the flow rate of the recirculated exhaust gas as a function of the sensed conditions. In one embodiment, the system includes an obstruction in the flow path of the recirculated exhaust gas and a differential pressure sensor for determining the pressure differential between a point upstream of the obstruction and a point downstream of the obstruction and control logic for determining the flow rate of the recirculated exhaust gas as a function of the current intake manifold pressure, the recirculated exhaust gas temperature, and the differential pressure drop across the obstruction.

Claims

1. A method for measuring the mass flow rate of recirculated exhaust gas in a vehicle having a compression-ignition engine, a plurality of engine sensors having outputs indicative of current engine conditions including an intake manifold pressure sensor, and a variable geometry turbocharger in which geometry is varied by a controllable actuator, the method comprising:

sensing intake manifold pressure;

controllably diverting a selected portion of exhaust gas for mixture with intake air;

sensing temperature in a flow of the recirculated exhaust gas;

obstructing the flow of the recirculated exhaust gas;

sensing pressure of the recirculated exhaust gas downstream of the obstruction;

sensing pressure of the recirculated exhaust gas upstream of the obstruction; and

determining flow rate of the recirculated exhaust gas as a function of the intake manifold pressure, recirculated exhaust gas temperature, and differential pressure drop across the obstruction.

2. The method of claim 1 wherein the exhaust gas is recirculated through a pipe, and wherein the flow of the recirculated exhaust gas is obstructed by providing a thin plate obstructor mounted in the pipe in the path of the recirculated exhaust gas defining an orifice having a diameter of between about 40% and about 80% of the diameter of the recirculated exhaust gas pipe.

3. The method of claim 2 further including providing a sharp edge on the edge of the plate which defines the orifice.

4. The method of claim 3 further including bevelling the edge of the obstructor defining the orifice on the downstream side of the orifice at an angle of between about 30°

and about 60°

from horizontal.

5. The method of claim 4 including bevelling the edge of the obstructor defining the orifice on the downstream side of the orifice at an angle of about 45°

.

6. The method of claim 2 wherein the flow of the recirculated exhaust gas is obstructed by providing a thin plate obstructor mounted in the pipe in the path of the recirculated exhaust gas defining an orifice having a diameter of about 60% of the diameter of the recirculated exhaust gas pipe.

7. The method of claim 1 wherein the flow rate of the recirculated exhaust gas is determined by

determining the differential pressure drop across the obstruction according to the following relationship:

8. A method for measuring flow ratio of recirculated exhaust gas to charge air in a vehicle having a compression-ignition engine, a plurality of engine sensors having outputs indicative of current engine conditions, and a variable geometry turbocharger in which geometry is varied by a controllable actuator, the method comprising:

diverting a selected portion of exhaust gas for mixture with intake air;

sensing the temperature of the recirculated exhaust gas;

sensing the temperature of the charge air;

sensing the temperature of the mixture of charged air and recirculated exhaust gas; and

determining the flow ratio of the recirculated exhaust gas as a function of the temperature of the charge air, the temperature of the recirculated exhaust gas, and the temperature of the mixture of charge air and recirculated exhaust gas.

9. The method for claim 8 wherein determining the flow ratio of the recirculated exhaust gas is based upon the relationship:

$\begin{array}{cc}\mathrm{EGR}<br><br>\text{\hspace{1em}<br><br>}<br><br>\%=\frac{{\stackrel{.}{m}}_{\mathrm{egr}}}{{\stackrel{.}{m}}_{\mathrm{air}}}-\frac{T_{\mathrm{mixture}}-T_{\mathrm{air}}}{T_{\mathrm{egr}}-T_{\mathrm{mixture}}}.& \left(6\right)\end{array}$

10. An information recording medium for use in a control module that controls a compression-ignition engine including a plurality of engine sensors having outputs indicative of current engine conditions, an intake manifold pressure sensor, and a variable geometry turbocharger in which geometry is varied by a controllable actuator, the information recording medium recording a computer program that is readable and executable by the control module, the computer program comprising:

sensing the intake manifold pressure;

controllably diverting a selected portion of the exhaust gas from the engine exhaust line for mixture with intake air;

sensing the temperature in the flow path of the recirculated exhaust gas;

sensing the pressure of the recirculated exhaust gas downstream of an obstruction in the flow of the recirculated exhaust gas;

sensing the pressure of the recirculated exhaust gas upstream of the obstruction; and

determining flow rate of the recirculated exhaust gas as a function of the current intake manifold pressure, recirculated exhaust gas temperature, and differential pressure drop across the obstruction.

11. The information recording medium of claim 10 wherein the computer program further comprises determining the flow rate of the recirculated exhaust gas by

determining the differential pressure drop across the obstruction according to the following relationship:

12. An information recording medium for use in a control module that controls a compression-ignition engine including a plurality of engine sensors having outputs indicative of current engine conditions, an intake manifold pressure sensor, and a variable geometry turbocharger in which geometry is varied by a controllable actuator, the information recording medium recording a computer program that is readable and executable by the control module, the computer program comprising:

controllably diverting a selected portion of the exhaust gas for mixture with intake air;

sensing the temperature of the recirculated exhaust gas;

sensing the temperature of the charge air;

sensing the temperature of the mixture of charged air and recirculated exhaust gas; and

determining the flow ratio of the recirculated exhaust gas as a function of the temperature of the charge air, the temperature of the recirculated exhaust gas, and the temperature of the mixture of charge air and recirculated exhaust gas.

13. The information recording medium of claim 12 wherein the computer program further comprises determining the flow ratio of the recirculated exhaust gas based upon the relationship:

$\begin{array}{cc}\mathrm{EGR}<br><br>\text{\hspace{1em}<br><br>}<br><br>\%=\frac{{\stackrel{.}{m}}_{\mathrm{egr}}}{{\stackrel{.}{m}}_{\mathrm{air}}}-\frac{T_{\mathrm{mixture}}-T_{\mathrm{air}}}{T_{\mathrm{egr}}-T_{\mathrm{mixture}}}& \left(6\right)\end{array}$