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Combustion Analysis and Knock Detection in Single Cylinder DI-Diesel Engine Using Vibration Signature Analysis

Author(s): Y.V.V.SatyanarayanaMurthy

Journal: International Journal of Engineering Science and Technology
ISSN 0975-5462

Volume: 3;
Issue: 1;
Start page: 10;
Date: 2011;
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Keywords: Knock | Vibration | combustion | Fast Fourier Transformation (FFT).

The purpose of this paper is to detect the “knock” in Diesel engines which deteriorate the engine performance adversely. The methodology introduced in the present work suggests a newly developed approach towards analyzing the vibration analysis of diesel engines. The method is based on fundamental relationship between the engine vibration pattern and the relative characteristics of the combustion process in each or different cylinders. Knock in diesel engine is detected by measuring the vibration generated by the engine using The DC-11 FFT analyzer with accelerometer. Knock in diesel engine is mainly due to the engine miss .A diesel engine miss results from one or more cylinders when the fuel is not burning properly. Improper fuel burning is caused by Injection system problems which include, Faulty injectors, clogged fuel filters, incorrect Injection timing, Low engine compression, injection system leaks, Air leaks, faulty injection pump etc. Engine miss causes rapid combustion with very high pressures generating a rumble or dull clattering sound. Abnormally loud sound with violent vibration is called “knocking or detonation”. Engine cylinder vibration in FFT form is monitored at each load the cylinder excitation frequencies are compared with the base line frequencies using diesel oil. Time wave forms on the cylinder head are also recorded to analyze the combustion. Since the very combustion in the cylinder is the basic exciter, the vibration study of the engine cylinder through the measured FFT and time waveforms are the representatives of combustion propensity. Vibration accelerometer is mounted on the cylinder head, preferably on the bolt connecting the head and the cylinder to record the engine vibrations using DC-11 data logger which directly gives the spectral data in the form of FFT, the overall vibration levels. This FFT data recorded is collected by On-Time window based software designed by e-predict Inc., Argentina. The Time waveforms are obtained on the cylinder head by DC-11 in the OFF-ROUT mode and are presented in graphic form by Vast DOS- based software, designed by VAST, Inc., Russia.
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