Dynamic modeling of an internal combustion engine operating with multiple combustion modes

• US 7,987,078 B2
• Filed: 08/10/2007
• Issued: 07/26/2011
• Est. Priority Date: 08/10/2006
• Status: Active Grant

• Current Assignee: Southwest Research Institute
• Original Assignee: Southwest Research Institute
• Inventors: Wang, Junmin
• Primary Examiner(s): Rodriguez; Paul L
• Assistant Examiner(s): PIERRE LOUIS, ANDRE
• Application Number:
  US11/837,036
• Publication Number:
  US 20080040085A1
• Time in Patent Office: 1,446 Days
• Field of Search: 703/7, 703/8
• US Class Current: 703/7
• CPC Class Codes: F02B 29/0406 Layout of the intake air cooling or coolant circuit
• CPC Class Codes: F02D 2041/007 by estimation
• CPC Class Codes: F02D 2041/1433 using a model or simulation of the system
• CPC Class Codes: F02D 2200/0402 the parameter being determined by using a model of the engine intake or its components
• CPC Class Codes: F02D 23/02 the engines being of fuel-injection type
• CPC Class Codes: F02D 41/0007 for control of turbo-charged or super-charged engines control of the pumps per se F02B37/12
• 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: F02D 41/3035 a mode being the premixed charge compression-ignition mode
• CPC Class Codes: F02M 26/05 High pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust system upstream of the turbine and reintroduced into the intake system downstream of the compressor
• CPC Class Codes: F02M 26/25 with coolers having bypasses
• CPC Class Codes: F02M 26/47 the characteristics being temperatures, pressures or flow rates
• CPC Class Codes: G06F 2119/08 Thermal analysis or thermal optimisation
• CPC Class Codes: G06F 30/15 Vehicle, aircraft or watercraft design
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A method of modeling a diesel engine that is capable of multiple combustion modes and equipped with a turbocharger and EGR loop. The model comprises a set of equations, each equation representing one of the following as a time derivative: pressure at the intake manifold, pressure between the turbine and an intake manifold throttle, pressure at the exhaust manifold, the compressor power, and the fresh air fraction (the ratio of fresh air to EGR). The model is used to determine what engine conditions (such as throttle positions and turbocharger output) will result in desired pressures and fresh air fraction.

Claims

1. A method of modeling a diesel engine operable for multiple combustion modes, the engine having an EGR (exhaust gas recirculation) throttle, HP (high pressure) throttle, and a turbocharger with a compressor and turbine, comprising:

expressing the following engine condition values each as one of the following five state equations;

a pressure at the intake manifold of the engine;

pressure between the compressor and the HP throttle;

pressure at the exhaust manifold of the engine;

power produced by the compressor; and

a fresh air fraction at the intake manifold;

wherein the pressure at the intake manifold is calculated from the ideal gas law and from flow rates through the HP throttle, the EGR throttle, and the compressor;

wherein the fresh air fraction at the intake manifold is calculated from the ideal gas law, from an air amount between the compressor and the HP throttle, and from an air amount in the exhaust manifold and wherein a plurality of actuators are used to control the fresh air fraction and pressure for a given combustion mode wherein a control unit controls in-cylinder conditions, including determining when to switch combustion modes and conditions to achieve optimal mode transitions;

wherein the five state equations provide an engine model, which can be solved to provide the engine condition values;

storing the state equations in a computer readable medium;

substituting input values into the state equations; and

wherein the input values include at least flow rates through the EGR throttle, HP throttle, and compressor turbine.

2. The method of claim 1, further comprising testing the input values on the diesel engine.

3. The method of claim 1, wherein the five state equations are in terms of time derivatives of the engine conditions.

4. The method of claim 1, wherein a state equation representing pressure between the compressor and HP throttle is derived from expressions representing conservation of mass between the compressor and the HP throttle.

5. The method of claim 1, wherein a state equation representing pressure at the exhaust manifold is derived from expressions representing conservation of mass at the exhaust manifold.

6. The method of claim 1, wherein a state equation representing compressor power is derived from expressions representing thermodynamics of the flow through the compressor.

7. The method of claim 1, wherein the compressor power is expressed as a time derivative based on simplification of the dynamics of the turbocharger as a first order system with a time constant.

8. The method of claim 1, wherein a state equation representing the fresh air fraction is a time derivative based on the fresh air fraction at the exhaust manifold and the flow rates through the HP throttle and the EGR throttle.