Detection Of Knocking Combustion In Diesel Engines By Inverse Filtering Of Structural Vibration Signals

Detection of Knocking Combustion in Diesel Engines by Inverse Filtering of Structural Vibration Signals

Vibration-based Condition Monitoring

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An Application to Detect Knock and Combustion Severity of Diesel Engine Working with Biodiesel (COME)-Additive Blends Using Cylinder Vibration Signature

Knock is an undesirable combustion mode occurring in diesel engines due to longer delay period that decreases the engine performance and life. In diesel engine, knock is mainly due to the improper fuel burning or missing caused by the injection system problems. Engine miss causes rapid combustion with very high pressures generating a rumble or dull clattering sound with violent vibration called “knocking or detonation”. The method introduced in the present study using alternate fuel (biodiesel-triacetin additive) in the engine suggests a newly developed approach towards analyzing the cylinder vibration of diesel engine. This method is based on fundamental relationship between the engine vibrations pattern and relative characteristics of the combustion process in the cylinder. Vibrations generated by the engine during knock are measured by using DC-11 Fast Fourier Transform (FFT) analyzer with accelerometer. The FFT output at each load of the cylinder excitation frequencies is obtained and compared with the frequencies of diesel fuel as base line. Time waveforms on the cylinder head and derived heat release rate curves are used to analyze the modus operandi of how combustion generates the vibrations and finally to detect the engine knock.