Transient processes of piston engines with various forms of external speed characteristic

Abstract

Power and dynamic indicators remain the main indicators of piston engines. At the same time, the dynamic qualities of the car are largely determined by the shape of the external speed characteristics of the engine. The possibilities of changing the shape of the external speed characteristics of the engine by adjusting the fuel supply in these modes are considered. A method is described for improving power and dynamic performance by converting a four-stroke engine to work on a two-stroke cycle in modes with low rotational speeds. The analysis of the results of computational studies of transient processes of engines with different forms of external speed characteristics is carried out. Using the mathematical model developed by the authors, a simulation of the transient acceleration process of a KamAZ-740 engine in the engine speed range from 800 to 2200 min-1 (an increase in the speed mode by 2.75 times) was carried out when adjusting the fuel supply. It is shown that an increase in the fuel supply of a KamAZ-740 engine in the maximum torque mode by about 1.5 times (an increase in the torque adaptability coefficient from 1.05 to 1.50) reduces the engine acceleration time from 8.2 to 5.4 seconds (by 34%). The simulation of acceleration of a car with a 2/4 Sight engine carried out by Ricardo (with its transfer to a two-stroke cycle at speed modes lower than the maximum torque speed mode) showed that when the vehicle was accelerated from 80 to 120 km/h (an increase in the speed of the car by 1.5 times), the time of such acceleration was reduced from 8.1 to 6.7 seconds (by 17%) compared to a car with a standard configuration.