Autoignition Detection via Pressure Gradient Comparison
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Solution Overview
Problem
Internal combustion engines face challenges in detecting autoignitions, which can lead to thermal overloading and damage due to existing methods' inefficiencies in distinguishing between autoignitions and other combustion faults, and current solutions do not effectively prevent autoignitions from escalating.
Innovation Solution
A method and device for detecting autoignitions in spark-ignited internal combustion engines using a combustion chamber pressure sensor, crankshaft angle sensor, and control device, which calculates theoretical pressure values and compares gradients to detect autoignitions, initiating countermeasures such as adjusting the air/fuel mixture and throttling to reduce combustion chamber temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If knocking sensors are used to detect combustion faults, then knocking combustion can be detected, but autoignitions cannot be reliably distinguished from other combustion faults
Solution Approach 1:
The patent introduces a model-based intermediary (theoretical pressure curve calculated from engine operating parameters) that mediates between the raw pressure sensor signal and the autoignition detection. By comparing the measured pressure gradient against the model-predicted gradient, the system can reliably distinguish autoignitions from other combustion faults, resolving the contradiction between detection accuracy and reliability.
2Reliability
If existing detection methods are used, then some combustion faults can be detected, but the escalation of autoignitions cannot be prevented
Solution Approach 1:
The patent implements preliminary action by detecting autoignitions at their early stage, before they can escalate into severe thermal overloading. The method compares pressure gradients during the compression stroke to identify incipient autoignitions and triggers countermeasures (such as enriching the air-fuel mixture or retarding ignition timing) before the autoignition can cause significant damage to engine components.
3Device complexity
If pressure sensor values are used directly without theoretical comparison, then simple detection can be achieved, but reliable autoignition detection is not possible
Solution Approach 1:
The patent applies parameter changes by transforming the raw pressure signal into a pressure gradient parameter (dp/dα) and comparing it against a theoretically calculated gradient based on engine operating parameters (temperature, pressure, volume, compression ratio). This parameter transformation enables precise autoignition detection while keeping the overall system relatively simple, as it uses existing sensors and standard thermodynamic models.
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 reliable and cost-effective detection of autoignitions, effectively protecting engine components from thermal overloading by quickly identifying and mitigating early autoignition events, thereby preventing damage.
Implementation Method 1
a combustion chamber pressure sensor for measuring the pressure in the combustion chamber
Implementation Method 2
a crankshaft angle sensor which supplies a signal which represents the crankshaft angle
Implementation Method 3
theoretical pressure values in the combustion chamber which would occur if no combustion were to take place in the combustion chamber are determined
Data Source
AI summary
A method is provided for detecting autoignition in a spark-ignited internal combustion engine, wherein values for the combustion chamber pressure are measured during a compression stroke of the internal combustion engine at defined crankshaft angles within an evaluation window, a filtered pressure value is determined from the measured values for the combustion chamber pressure, and theoretical pressure values in the combustion chamber that would arise if no combustion took place in the combustion chamber are determined for the defined crankshaft angles. The value of the slope between two defined crankshaft angles for filtered pressure values is determined, the value of the slope between two defined crankshaft angles for theoretical pressure values is determined, and a difference of the slope values is calculated therefrom. This difference is compared with a specified threshold value, and, if the threshold value is exceeded, an autoignition in the combustion chamber is inferred.