ABSTARCTThe paper presents the numerical analysis of the drag force generated on the body of a sports car, based on the CFD method in the Ansys Fluent program. The three-dimensional model of the vehicle was taken from an open CAD database. Based on this, a computational grid was developed, boundary conditions and a turbulence model were defined. As a result of the calculations, the pressure distribution on the individual body parts and the velocity distribution in selected cross sections were obtained. In the next part of the research, the simulation results are used to optimize the shape of the bodywork of different passenger vehicles in order to reduce the generated drag force.
Homogeneous charge compression ignition concepts despite high efficiency and ultra-low nitrous oxides emissions, suffer from week controllability and load range limited by excessive pressure rise rates. In the present work, controlled auto-ignition is achieved via direct injection of gasoline into the exhaust gasses recompressed during negative valve overlap phase. Single cylinder engine experiments are designed to explore the potential of additional late post injection strategies for pressure rise rate and peak pressure suppressing. For two mixture strengths, fuel distribution is varied between 3 gasoline injection events. In-depth combustion analysis is supported by emission measurement results. Increasing the amount of gasoline, post-injected during the main compression event, was proven to be an effective measure for reducing pressure rise rates, with over 50% reduction potential. The regulation capability however, is limited by typical tread-offs between stratified and homogenous fuelling concepts. Using post injection strategy results in decreased hydrocarbon emissions, but causes rapid increase in carbon monoxide and particulate matter emissions. Nitrous oxide increase rate is dependent on mixture strength with significantly higher sensitivities during lean operation.
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