Estimating Ignition Delay Period Using In-Cylinder Fuel Density
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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 are costly, as they involve determining multiple parameters under various operation conditions, and cannot estimate the ignition delay period independently without expressing the entire heat generation rate waveform.
Innovation Solution
The ignition delay period, a characteristic value of the heat generation rate waveform, is estimated using fuel density, allowing for reduced man-hours and accurate estimation of the ignition delay period, with influences from engine load rate and spark time collectively expressed by fuel density, and correction based on engine rotation speed for higher accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple parameters (m, k, a/θp^m+1, θb) are identified under various operation conditions to determine the Wiebe function, then the heat generation rate waveform can be expressed with high accuracy, but the man-hours and costs to produce the waveform increase significantly
Solution Approach 1:
The invention extracts and focuses specifically on the ignition delay period (θb parameter) as a separate characteristic value that can be estimated independently from the entire heat generation rate waveform. By taking out this specific parameter of interest, the invention enables accurate estimation of the ignition delay period without requiring identification of all Wiebe function parameters under various operation conditions, thus significantly reducing the time and resources needed while maintaining the required accuracy for evaluating ignition characteristics
Solution Approach 2:
The invention segments the heat generation rate waveform analysis into separate characteristic values, specifically isolating the ignition delay period (θb) from the overall combustion process parameters. This segmentation allows the ignition delay period to be estimated using a dedicated correlation with fuel density at spark time, independent from the other parameters (m, k, a/θp^m+1), thereby reducing the complexity and time required for comprehensive waveform production
2Adaptability or versatility
If the entire heat generation rate waveform is expressed by identifying all Wiebe function parameters, then the combustion state can be evaluated comprehensively, but the ignition delay period cannot be estimated independently
Solution Approach 1:
The invention extracts the ignition delay period as a separable characteristic value that can be estimated independently using fuel density at spark time. This extraction allows the ignition delay period to be evaluated without requiring comprehensive identification of all Wiebe function parameters, thereby reducing the complexity of the system while still enabling comprehensive combustion state evaluation through the use of multiple independent characteristic values
3Productivity
If fuel density at spark time is used to estimate ignition delay period, then the estimation process is simplified and man-hours are reduced, but the influence of engine load rate and spark time must be collectively expressed by fuel density
Solution Approach 1:
The invention applies universality by using fuel density at spark time as a multi-functional parameter that collectively expresses the influences of engine load rate, spark time, and other operation conditions on the ignition delay period. This single parameter serves multiple purposes: it captures the effect of varying load rates, accounts for different spark timing positions, and maintains accuracy across various operating conditions, thereby simplifying the estimation process while maintaining comprehensive coverage of operational variations
Data Source
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AI summary
An ignition delay period, for example, is estimated or 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. A period from spark generated by an ignition plug to ignition of an air-fuel mixture is defined as an ignition delay period τ that is one of characteristic values of the heat generation rate waveform. When the ignition time FA of the air-fuel mixture is on the advance side of a compression top dead center of a piston (BTDC), the ignition delay period τ is estimated based on an in-cylinder fuel density ρfuel@SA at the spark time SA, and when the ignition time FA of the air-fuel mixture is on the delay side of the compression top dead center of the piston (ATDC), the ignition delay period τ is estimated based on an in-cylinder fuel density ρfuel@FA at the ignition time FA. Thus, the heat generation rate waveform is produced using the estimated ignition delay period τ.