Thermodynamic analysis of indexes of operation of the engine with direct fuel injection for idle speed and acceleration

Abstract

Contemporary requirements for combustion engines are aimed mainly at obtaining significant parameter values of their operation at simultaneously low fuel consumption and reduced exhaust emission. Despite the fact that combustion engines utilize diverse load conditions, the idle speed share in the whole range of their operation is significant. The percentage of combustion engines with spark-ignition direct injection (SI DI) in the total number of spark-ignition engines is increasing. It means that the method of the mixture preparation is an important factor in SI DI engine, also for idle speed. In the tests was analysed the SI engine preparing the mixture with a dose of injected fuel (air-guided type) in conditions of the idle speed. Idle speed control is a critical issue in engine control fields. Essentially, it is a highly nonlinear and time-varying problem. Its performance has a significant impact on fuel economy and emission levels. The engine operation indexes were determined, and with the use of coefficient of variation, the variation of the cycle was estimated. Article contains the three-stage division, taking into account the variable measuring modes where was analysed the work condition during the idling, free acceleration of combustion engine and car acceleration. From numerous operational indexes of the engine operation were selected those, which in the best way characterize engine operation for idle speed.