In-Cylinder Pressure Signal Processing Applied to the Diagnosis of Combustion in Low Displacement Diesel Engine

摘要

The analysis of the pressure signal in the combustion chamber provides information that is used for combustion diagnostics and advanced technologies for engine control. Due to noise conditions, cycle variations, and offset issues, proper signal processing is necessary in order to ensure proper accuracy. In this study, pressure signal processing is analyzed, based on the average of consecutive cycles and signal filtering. The experimental development is carried out on a low-capacity diesel engine. The tests have been conducted under different conditions of engine speed and torque. The effect of noise and the variations of each cycle on the pressure signal have been investigated. By using a statistical methodology based on standard deviation, it has been verified that a number of 40 cycles averaged out allows for a considerable reduction in the pressure signal disturbance for the different engine operating modes. The use of the low-pass filter has made it possible to eliminate high-frequency noise, which could not be eliminated by averaging the signal. Calculations of the standard deviation of heat release rates have been kept below 0.6 J/deg. By comparing the results of the signal with and without filtering, it has been verified that an adequate quality of the pressure signal for further analysis of the combustion process is obtained.