Internal Combustion Engine Air-Fuel Ratio Estimation via Cylinder Pressure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for estimating the air-fuel ratio in internal combustion engines are inadequate in accurately reflecting the specific-heat ratio and temperature properties of the air-fuel mixture, leading to inefficiencies in fuel injection control and potential engine performance issues.
Innovation Solution
An internal combustion engine control apparatus that includes a cylinder pressure sensor, operational status detection unit, reference crank angle setting unit, reference cylinder pressure calculation unit, air-fuel ratio estimation unit, and control unit, which calculates the air-fuel ratio based on the pressure difference between actual and reference cylinder pressures, reflecting the specific-heat ratio's temperature properties and ensuring accurate estimation and control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional specific-heat ratio estimation methods are used, then calculation simplicity is maintained, but measurement precision and reliability of air-fuel ratio estimation deteriorate due to inadequate reflection of temperature properties
Solution Approach 1:
The system pre-calculates and stores reference cylinder pressures corresponding to various specific-heat ratios and operating conditions in a lookup table. During operation, the controller simply retrieves the appropriate reference pressure based on detected operating parameters, avoiding complex real-time calculations while maintaining high estimation accuracy through the pre-computed temperature property relationships
Solution Approach 2:
The specific-heat ratio serves as an intermediary parameter that connects cylinder pressure measurements to air-fuel ratio estimation. By introducing this intermediate physical property that directly reflects temperature characteristics of the air-fuel mixture, the system achieves more accurate air-fuel ratio estimation without requiring direct temperature measurement, thus maintaining system simplicity while improving precision
2Productivity
If conventional air-fuel ratio estimation methods are used, then system simplicity is maintained, but fuel injection control accuracy deteriorates leading to engine performance issues
Solution Approach 1:
The system implements a feedback control mechanism where the estimated air-fuel ratio (derived from specific-heat ratio and pressure difference) continuously informs fuel injection adjustments. The controller compares the estimated air-fuel ratio against target values and modifies fuel injection quantities accordingly, creating a closed-loop system that optimizes fuel efficiency while maintaining accurate control
Solution Approach 2:
The system dynamically adjusts fuel injection parameters based on detected operating conditions (engine speed, load, temperature) and the calculated specific-heat ratio. By changing fuel injection quantity and timing parameters in response to real-time specific-heat ratio measurements, the system optimizes combustion efficiency and reduces energy loss while maintaining precise air-fuel control
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables precise estimation and control of the air-fuel ratio, improving fuel injection accuracy and engine performance by reflecting the specific-heat ratio's temperature properties, thus maintaining high accuracy and avoiding inefficiencies.
Implementation Method 1
a cylinder pressure sensor that detects a pressure in the cylinder as a cylinder pressure
Implementation Method 2
the fact that a change in the status of an air-fuel mixture in the compression stroke in an internal combustion engine is a polytropic change and the fact that a specific-heat ratio of an air-fuel mixture varies with an air-fuel ratio
Implementation Method 3
a specific-heat ratio κ of an air-fuel mixture is calculated from respective cylinder pressures P1 and P2 detected at two predetermined crank angles θ1 and θ2 by a cylinder pressure sensor during the combustion stroke and cylinder volumes V1 and V2 corresponding to the crank angles θ1 and θ2 by the following expression: κ=log(P1/P2)/log(V2/V1)
Implementation Method 4
combustion of the air-fuel mixture is started in accordance with the detected operational status of the internal combustion engine
Data Source
AI summary
An internal combustion engine control apparatus includes a cylinder pressure sensor, a driving condition detector, a reference crank angle setter, a reference cylinder pressure calculator, an air-fuel ratio estimator, and a controller. The cylinder pressure sensor detects a cylinder pressure. The driving condition detector detects a driving condition in an engine. The reference crank angle setter calculates a reference crank angle immediately before which an air-fuel mixture starts combusting in accordance with the driving condition. The reference cylinder pressure calculator calculates a reference cylinder pressure in the cylinder at the reference crank angle based on temperature characteristics of a specific-heat ratio of the air-fuel mixture under a condition. The air-fuel ratio estimator calculates an air-fuel ratio based on a pressure difference between the reference cylinder pressure and the cylinder pressure at the reference crank angle. The controller controls the engine in accordance with the air-fuel ratio.