Automotive Science and Engineering

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To improve the engine performance and reduce emissions, factors such as changing ignition and injection timing along with converting of port injection system to direct injection in SI(spark-ignited) engines and hydrogen enrichment to CNG fuel at WOT conditions have a great importance. In this work, which was investigated experimentally (for CNG engine) and theoretically (for combustion Eddy Break-Up model and turbulence model is used) in a single- cylinder four-stroke SI engine at various engine speeds (2000-6000 rpm in 1000 rpm intervals), injection timing (130-210 crank angle(CA) in 50 CA intervals), ignition timing (19-28 CA in 2 degree intervals), 20 bar injection pressure and five hydrogen volume fraction 0% to 50% in the blend of HCNG. The results showed that fuel conversion efficiency, torque and power output were increased, while duration of heat release rate was shortened and found to be advanced. NOx emission was increased with the increase of hydrogen addition in the blend and the lowest NOx was obtained at the lowest speed and retarded ignition timing, hence 19° before top dead center. 

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In internal combustion engines, the turbocharger and alternative fuels are two important factors affecting engine performance and exhaust emission. In this investigation, a one-dimensional computational fluid dynamics with GT-Power software was used to simulate a six-cylinder turbocharged diesel engine and the naturally aspirated diesel engine to study the performance and exhaust emissions with alternative fuels. The base fuel (diesel), methanol, ethanol, the blend of diesel and ethanol, biodiesel and decane was used. The results showed that decane fuel in the turbocharged engine has more brake power and torque (about 3.86%) compared to the base fuel. Also, the results showed that the turbocharger reduces carbon monoxide and hydrocarbon emissions, and biodiesel fuel has the least amount of carbon monoxide and hydrocarbon among other fuels. At the same time, the lowest NO_X emission was obtained by decane fuel. As a final result can be demonstrated that the decane fuel in the turbocharged engine and the biodiesel fuel in the naturally aspirated engine could be a good alternative ratio to diesel fuel in diesel engines.