On board recognition of different fuels feeding SI engines with the use of dimensional and nondimensional vibration signal parameters-part 1

The availability of gaseous fuels such as natural gas and propane butane mixtures has led to worldwide popularity of internal combustion engines running dual fuel or alternatively gas powered. These gaseous fuels are known as fuels more resistant to knocking than conventional liquid fuels and as less ones pollutant. Their better mixing with air is also well recognized. There are some works published on the use of gaseous fuels, but the problem of the combustion noise, as a very important source of information regarding the combusted fuel, is not receiving much attention. Combustion noise occurs in two forms, direct and indirect. It is transmitted throughout the engine block as a vibration at a different spectrum of frequencies. In this study an attempt is made to relate the combustion noise to the operating parameters for LPG, CNG and Hydrogen enriched CNG powered engine as compared to petrol fueled engine. Combustion pressure and vibration of cylinder block data are measured and presented in case of engine running on gaseous fuels and compared to the results obtained for engine fed by petrol. The ability to recognize the fuel type feeding the multi-fuel engine would certainly make it possible to automatically adjust both fuel and ignition system setup, allowing the optimal fuel energy utilization. The first part of the methodology based on selected vibration signal parameters for the purposes of fuel type recognition, has been presented in the paper. The following parameters have been mentioned: scalogram and wavelet coefficient increase. Signals of multiple resonances in combustion chamber and corresponding vibration signals of cylinder block of engine were examined for one combustion cycle. Tests were completed on a four cylinder, 1.6L spark-ignition engine converted to run on gaseous fuels in this project. The engine test stand was fully computerized and the cylinder pressure data, acceleration of vibration of engine block, crank angle data were stored on a PC. The influence of engine speed, load on combustion and engine block vibration were examined for all fuels. A few of well known diagnostic parameters were used for comparison of engine noise operated on petrol and gaseous fuels.