Heat Generation Rate Waveform Calculation Using First-Half Combustion Period
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Solution Overview
Problem
Conventional methods for calculating the heat generation rate waveform in internal combustion engines require extensive man-hours and resources, as they need to consider various operation conditions to determine the Wiebe function parameters, and they cannot estimate the first-half combustion period independently without expressing the entire waveform.
Innovation Solution
The first-half combustion period, from ignition to the maximum heat generation rate, is identified as a characteristic value not affected by engine load, EGR rate, air-fuel ratio, or oil-water temperature, allowing its estimation based on physical quantities at the maximum heat generation rate time, using the in-cylinder volume and engine rotation speed to calculate the waveform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the entire heat generation rate waveform is expressed using the Wiebe function with multiple parameters, then accurate evaluation of the combustion state is achieved, but it is not possible to estimate and evaluate only the first-half combustion period independently
Solution Approach 1:
The patent segments the combustion process into two distinct periods: the first-half combustion period (from ignition to maximum heat generation rate) and the second-half combustion period. By applying different functional forms to each segment - using a simplified linear relationship for the first-half period and the Wiebe function for the second-half period - the patent enables independent estimation and evaluation of the first-half combustion period while maintaining accurate representation of the overall combustion state.
2Measurement precision
If Wiebe function parameters are identified under various operation conditions, then accurate heat generation rate waveform is obtained, but extensive man-hours and costs are required
Solution Approach 1:
The patent changes the parameter representation for the first-half combustion period from complex Wiebe function parameters to simple physical quantities (in-cylinder volume and engine rotation speed) that can be directly measured or calculated. This parameter transformation eliminates the need for extensive parameter identification experiments under various operation conditions, reducing man-hours and costs while maintaining waveform accuracy through the established linear relationship between the first-half combustion period and these physical quantities.
Data Source
AI summary
A first-half combustion period, for example, is estimated/evaluated, with a required accuracy, more simply than the conventional art, while reducing man-hours to produce a heat generation rate waveform of an internal combustion engine. Within a combustion period of an air-fuel mixture, a period from an ignition time FA to a heat generation rate maximum time dQpeakA where the heat generation rate is maximum is defined as the first-half combustion period a that is one of characteristic values of the heat generation rate waveform. The first-half combustion period a is estimated based on an in-cylinder volume at the heat generation rate maximum time, and furthermore by being corrected using an exponential function of the engine rotation speed with a value depending on a tumble ratio as exponent. Thus, the heat generation rate waveform is produced using the estimated first-half combustion period a.