Predicting Engine Knock via Polytropic Compression Analysis
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Solution Overview
Problem
Current engine management systems rely on knock sensors that detect vibrations after engine knock occurs, leading to incomplete suppression of engine block noise and damage, and rapid changes in operating parameters that impair fuel efficiency and quietness.
Innovation Solution
A method predicting engine knock by calculating initial cylinder pressure using operating parameters and manifold pressure, interpreting the compression process as a polytropic process, calculating heat release rates, and determining ignition delay to assess unburned gas temperature and mass fraction, allowing for proactive control of engine parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a knock sensor is used to detect engine knock, then knock detection capability is improved, but the detection occurs too late to prevent knock and causes rapid parameter changes that worsen fuel efficiency and quietness
Solution Approach 1:
The patent calculates predicted in-cylinder pressure and unburned gas temperature before knock occurs, enabling advance detection of knock-prone conditions. By computing ignition delay and unburned gas mass fraction at end of ignition delay, the system identifies potential knock events before they happen, allowing preventive action rather than reactive response, thus avoiding the fuel efficiency penalty of rapid parameter changes
2Reliability
If operating parameters are rapidly changed to avoid knock, then knock prevention is improved, but vehicle quietness and fuel efficiency deteriorate
Solution Approach 1:
By calculating predicted in-cylinder pressure, unburned gas temperature, and ignition delay characteristics in advance, the system identifies knock-prone conditions before knock occurs. This allows gradual or preventive adjustment of operating parameters rather than rapid changes, maintaining vehicle quietness while preventing knock
Solution Approach 2:
The patent establishes a feedback mechanism where predicted in-cylinder pressure and unburned gas temperature are continuously calculated based on actual operating conditions. The engine management system uses this feedback to adjust operating parameters proactively, maintaining knock prevention while avoiding unnecessary rapid changes that would affect quietness and fuel efficiency
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
Enables early prediction and prevention of engine knock, reducing noise, engine damage, and improving fuel efficiency by allowing robust control of engine operating conditions before knock occurrence.
Implementation Method 1
calculating in-cylinder pressure at spark timing by interpreting compression process as polytropic process based on the initial pressure calculation
Implementation Method 2
calculating unburned gas temperature using adiabatic compression process using the calculated change in in-cylinder pressure
Data Source
AI summary
Disclosed herein is a method of predicting engine knocking, which includes calculating initial pressure in cylinder based on operating data and pressure in intake manifold measured using manifold absolute pressure sensor, calculating pressure at spark timing in the cylinder by interpreting compression process as polytropic process based on the calculated initial pressure in the cylinder, calculating heat release rate for individual operating conditions based on the calculated pressure in the cylinder at spark timing, calculating pressure change in the cylinder based on the calculated heat release rate, calculating unburned gas temperature in adiabatic compression process based on the calculated pressure change in the cylinder, and determining whether knock occurs by calculating ignition delay based on the calculated unburned gas temperature and calculating unburned gas mass fraction at crank angle at the end of the ignition delay.