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This paper is about computer modelling of a four-stroke spark-ignition engine with a dual-injector system. Using a KIVA-3V program for Linux, computer simulations were performed for one of the cylinders fuelled by multipoint injection and by the dual-injector system, i. e. with direct injection into the cylinders on top of MPI. The modelling was done for a combustion engine Toyota 2SZ-FE with a dual-injector system. Both simulations were done for the same parameters of engine's work, i.e. at the same RPM of 2000 and the intake pipe pressure of 0.079 MPa. KIVA-3V program models the processes taking place in an internat combustion engine while taking into account physical and chemical phenomena occurring during the formation of a charge and during its combustion. Using a stochastic model of injection the program takes into account the movement of droplets and their dispersion. The results of the simulation show that the dual-injector system has an improved volumetric coefficient, i.e. improved engine performance. An increase in the engine's indicated pressure was also observed; this increases the engine's total efficiency. The intensification of the charge's angular momentum in a cylinder with a dual-injector system can explain the improvements in the course of combustion process. Because the air-fuel mixture was already partially formed in the engine there was a small increase in the unburned hydrocarbons in the cylinder. However, a marked drop in the carbon monoxide and nitric oxide were observed for the dual-injector system. Analyzing the overall results of the simulations one can ascertain a positive impact of using a dual-injector system on the working parameters of a spark-ignition engine.
This paper analyzes aprocess of combustion in a spark-ignition engine. The aim of the analysis was to determine the differences in the combustion process between the engine with a classic multipoint injection system and a system which injects fuel directly to the cylinders as well. To aid in the analysis the measurements of the high variable pressure in the engine's cylinder against the crankshaft angle were taken. This allowed us to obtain indicated diagrams for both types of engines. To eliminate distortions, both functions were approximated using combined functions. The other basic parameters were also measured: torque, RPM and instantaneous fuel consumption. The analysis of the indicated diagrams yielded an indicated mean pressure and thermal efficiency for both fuel systems. Then, a comprehensive analysis ofpressures in cylinders was performed in order to determine the way the flame spreads in the cylinder for the two types of engines. The results obtained from this analysis show that the speed of combustion is greater for the charge formed by the dual-injector fuel system. The increased speed of the combustion, especially when it reaches a 50% fraction of the exhaust gas in the cylinder, is what accounts for the increase in the indicated mean pressure and the increase in the thermal efficiency of the engine with a dual-injector fuel system. The time of the spreading of the flame, as well as the fast burn period were reduced. The increased efficiency of the combustion process in the cylinder me ans that the heat losses through the cylinder sleeve are greatly reduced. The results of the research in this paper confirm the purposefulness of using a dual-injector fuel system in a spark-ignition engine.
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