Numerical Simulation And Experimental Research On The Working Process Of Hybrid Compressed-Air And Fuel Engine

Due to the increasing shortage of oil resources and increasingly serious environmental pollution problems caused by the internal combustion engine vehicles, automobile manufacturers and related research institutions not only strive to improve the performance of internal combustion engine to meet the increasingly stringent environmental protection standards, but also pay more attention to research and development of the new generation of alternative-fuel, ultra-low emission, fuel-saving automotive engines.In this paper, a new hybrid compressed-air and fuel engine concept is proposed, which can work by compressed-air powered engine mode and internal-combustion engine mode. The compressed-air powered engine mode is to change the pressure of compressed air into mechanical energy, and there are no pollutant emissions. The operating principle of internal-combustion engine mode is similar to the four-stroke internal combustion engine, so it will inevitably produce harmful emissions. Although the hybrid engine is not zero pollution emissions, fuel consumption and harmful emissions greatly reduce, belongs to low-emission and fuel-saving engine.The main research content of this paper is as follows:Chapterâ… : After the introduction of the research situation and existing problems of the compressed air powered engine, a new hybrid compressed-air and fuel engine concept is put forward. Then give an overview of the domestic and foreign research situation and existing problems of hybrid compressed-air and fuel engine. Finally, the main research objects of this dissertation are proposed.Chapterâ…¡: The series structure and the parallel structure of hybrid compressed-air and fuel engine are designed, and their operating principles and characteristic are respectively elaborated. According to the ideal thermodynamic cycle, the feasibilities of the series and parallel structure of hybrid four-stroke compressed-air and fuel engine are analyzed. The feasibility analysis shows that the performance indicators of the two working modes of hybrid four-stroke compressed-air and fuel engine are similar to those of non-supercharged four-stroke internal combustion engine, and can meet the small automobile engine's needs. Chapterâ…¢: By the first law of thermodynamics and the second law of thermodynamics, the working process mathematical model and the exergy analysis mathematical model of the two working modes of hybrid four-stroke compressed-air and fuel engine are respectively established. According to the established mathematical model, simulation and calculation method is designed and the fourth-order Runge-Kutta method is selected to solve the mathematical models.Chapterâ…£: The working characteristics and the exergy distribution of four-stroke compressed-air powered engine mode are researched using simulation computational method. Mainly study the speed characteristic and the influence of several key parameters such as valve timing, inlet air pressure of compressed air, cylinder volume, and stroke-bore ratio on the working characteristics. The influence of several key parameters such as pneumatic- source pressure, inlet-air pressure of compressed-air, and inlet-air temperature of compressed-air on the energy efficiency of the system is also analyzed.Chapterâ…¤: The working characteristics and the exergy distribution of internal-combustion engine mode are researched using simulation computational method, and the speed scope to switch the two operating mode of the hybrid four-stroke compressed-air and fuel engine is also analyzed. Research of the working characteristics mainly includes the speed characteristics and load characteristics. Research of the exergy distribution mainly involves influence of speed and load on the energy efficiency of the system.Chapterâ…¥: Two kinds of parallel hybrid compressed-air and fuel prototype engine are designed, and the test bench is also set up. According to the test results of two-stroke compressed-air powered engine and four-stroke internal-combustion engine, the simulation results of the two working mode of four-stroke hybrid compressed-air and fuel prototype engine are assessed. The bench test of parallel two-stroke hybrid compressed-air and fuel prototype engine is finished, and the switching rotation speed of the two working mode is analyzed.Chapterâ…¦: The research work is summarized and perspectives on the future are presented.