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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.

The availability of gaseous fuels like natural gas and propane butane mixtures has lead 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 ones less pollutant, their better mixing with air is also well recognized. There have been many published works on the use of gaseous fuels but actually the problem of the combustion noise, as a very important source of acoustic discomfort is not receiving 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 powered engine as compared to petrol fueled engine.

Paper presents the general assumptions for an gaseous fuels injector rail diagnosis and calibration with the application vibroacoustic methods, considerably different from used today methodology which typically base on measurements of mechanical dislocation of piston/nozzle, and injector flow rates has been described in the paper. Flow rates, as well as injector actuator stroke measurements are time-consuming and require the use of complex systems. This is what generally disables the methods currently in use from their integration in the continuous control system, especially into OBD. Methodology presented in the paper, based on simultaneous measurements of injector opening time and its vibration, allows an enhanced accuracy of the calibration and diagnosis process. It also shortens the time of calibration since it does not require invasion into mechanical system of injector rail and allows a quick and efficient assessment of its proper operation.

A study on the overall performance of an engine powered with hydrogen-enriched NG at stoichiometric condition, for different hydrogen shares have been described in this paper. The research has been carried on a General Motors Company X16SZR 4-cylinder, 4-stroke 1600 cm3 engine. Engine dynamometer tests were complemented with mathematical model calculations. Tested engine has been equipped with an aftermarket CNG feeding system where fuel is being injected into intake manifold simultaneously under low overpressure. Research program provided analysis for fuel blends with variable methane/hydrogen volume proportion (%): 100/0, 95/5, 90/10, 85/15, 80/20, 70/30, 60/40 and 50/50. Ignition timing and all other strategies, excluding EGR, remained unvaried. Testing procedure provided three different steady-state engine operation points for each of 8 different fuels: idle, high speed without load and full power at speeds in range of 1500-3500 rpm.

Influence of piston skirt clearance on engine noise has been presented in this paper. Traces of forces producing engine block vibrations, i.e. gas force, and piston slap force were estimated and verified with real sampled data. An engine block vibration signal decomposition was also carried on, what enabled the identification of the influence of piston clearance on wavelet factor values C(a,b). It has been proved that increasing piston skirt clearance, delays the response of engine body on piston slap.