Tkachenko O. Improvement of energy efficiency of passenger cars by rational choice of parameters of motor-transmission system

Dissertation for obtaining the scientific degree of Doctor of Philosophy in specialty 274 "Automotive transport". – Kharkiv National Automobile and Highway University, Kharkiv, 2024. Improving the energy efficiency of cars is an important scientific, practical and technical task. The current global environment requires many governments to take measures to reduce fuel consumption in road transport. One of these measures is to reduce the maximum speed of vehicles on main roads, not to improve traffic safety, but to reduce fuel consumption. Refinement of the method for calculating the aerodynamic drag of a car, taking into account the dependence of the coefficient of frontal aerodynamic drag on speed, allows to reduce the required engine power while ensuring the required indicators of the dynamism of cars. Improving the methodology of traction calculation of a car requires a revision of the choice of gear ratios of the main gear and gearbox. The dissertation was carried out within the framework of the individual work plan of the graduate student, the work was carried out: - In accordance with the Resolution of the National Council on the Safety of Human Life №. 3 of December 25, 1997 “On the compliance of labor protection requirements for machines, vehicles, equipment manufactured in Ukraine”; - The Transport Strategy of Ukraine for the period up to 2020, approved by the Cabinet of Ministers of Ukraine on October 20, 2010, №. 2174-p; - According to the plan of implementation of research work under the state order №. D3/101-2022 dated October 25, 2022. “Development of a prototype of an energy-efficient wheeled small-sized dual-use vehicle” №.01224200935. Purpose and objectives of the study. The aim of the study is to improve the operational properties of passenger cars by increasing their energy efficiency through the rational choice of parameters of the engine-transmission system. To achieve this goal, the following tasks are necessary: - To conduct a theoretical study of the possibility of reducing engine power while maintaining the level of dynamic properties of the car; - To conduct a theoretical study of improving the energy efficiency of cars with a rational reduction in engine power; - To conduct experimental studies of the dynamic properties of a passenger car. The scientific novelty of the results obtained is the development of known methods for selecting the parameters of motor-transmission systems, taking into account the dependence on the speed of the frontal coefficient of aerodynamic resistance. At the same time, for the first time: - The gear ratio of the gearbox in the lower gear is determined, which, provided that the maximum initial acceleration is realized when the car is touched from a standstill, should be in the range of 4.183 - 5.074. - Determination of the power reserve on the driving wheels, which is formed as a result of using an increased constant value of the aerodynamic frontal coefficient (independent of speed) in the calculations; - For the first time, a method for rationally reducing the maximum effective engine power by reducing the power reserve while maintaining the required indicators of the vehicle's dynamic properties. The method of selecting rational gear ratios of the main gear and gearbox was improved in the direction of taking into account the change in the speed of the frontal coefficient of aerodynamic drag. The laws of controlling the effective torque and effective engine power were further developed in the direction of ensuring passenger comfort and cargo safety when accelerating the car. The practical significance of the obtained results is to develop a methodology for rationally reducing the maximum effective engine power and selecting gear ratios of the main gear and gearbox of the car, which is used in the laboratory of high-speed cars of KhNAНU in the development of advanced cars. Personal contribution of the applicant. The scientific results of the research submitted for defense were obtained by the author independently. In joint works with other authors, the dissertator used the following: in [1], a method for rationally reducing the maximum effective engine power is proposed; in [2, 3], a method for selecting the parameters of the motor-transmission system with a rational reduction in the maximum effective engine power is proposed; in [4, 5], rational laws for controlling effective torque and engine power are determined, provided that comfort is ensured; in [6-13], directions for improving energy efficiency are proposed by