EFFECTS OF USING A DUAL-INJECTOR FUEL SYSTEM ON A PROCESS OF COMBUSTION IN A SPARK-IGNITION ENGINE

This paper analyzes a process 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 wh ich injects fuel directly to the cylinders as well. To aid in the analysis the measuremen ts of the high variable pressure in th e engine's cylinder against the crankshaft angle were taken. This allowed us to obtain indicated diagrams for both types o f engines. To eliminate distortions, both functions were approximated using combined functions. Th e other basic parameters were also measu red: torque, RPM and insta ntaneous fuel consumption. The analysis of the indicated diagrams yielded an indicated mean pressure and thermal e fficiency for both fuel systems. Then, a comprehensive analysis of pressures in cylin ders 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 grea ter for the charge formed by the dual-injector fuel system. The increased spee d 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 eff iciency of the combustion process in the cylinder means tha t the heat losses through the cylinder sleeve are greatly red uced. The results of the research in th is paper confirm the purposefulness of using a dual-injector fuel system in a spark-ignition engine.