Optimization And Matching Research On 4108 LPG Engine

With the global energy and environmental problems increasingly serious, the research of clean substitute fuel automobile has currently become an important direction of developing automobile industry. The liquefied petroleum gas (LPG) with high calorific value, low cost, high anti-explosion performance, abundant resources and so on become the first choice of clean burning car alternative fuel. In an increasingly stringent fuel economy and emission regulations, the development of LPG car at home and abroad is rapid. At present, most people focus on the research of LPG engine combustion mechanism, structure and working process optimization and emission control technology. Based on computer simulation analysis and experimental research, the 4108 LPG engine with its structure parameters optimization analysis, control system selection, subsystem parts matching selection and the calibration method of the machine performance are studied, which aims at improving engine power, economy and emission performance.To analyze the engine working process for the purpose, based on gas dynamics, thermodynamics and basic principle of engine, according to law of conservation, using the modern computer technology and numerical method, this paper has studied the engine performance by simulation analysis. Through the use of advanced engine performance simulation software BOOST, this paper established the simulation model of turbocharged and lean burning 4108LPG engine, and then simulated the working process of the engine. By optimizing the compression ratio (from 7 to 10), power and economy properties have been improved obviously. Power increased from 73 kW to 106.5 kW, fuel consumption ratio decreased by 12.9% and exhaust temperature dropped 55℃。Under the most optimal compression ratio, this paper used the successive optimization method to optimize engine distribution phase. That is optimizing valve overlap angle first and then optimizing the exhaust valve open Angle. The results show that:the optimized engine both can satisfy the vehicle power, economy etc various performance indicators. The above research provides a good theoretical guidance for the next experiment. To develop the better performance of LPG engine, this paper designed and builded the engine test bench. According to the developing goal, this thesis chose ECI company's lean burning heavy-duty gas engine control systems, formulate the technology solutions, such as lean burning turbocharged, electric pressure regulator fuel control, oxygen sensor closed-loop control, high energy ignition of single cylinder independent, and high response performance of intensification pressure control. Through the analysis of relation curves between the thermal efficiency, platoon temperature, the combustion instability and single fuel gas engine emission and excess air coefficient, and determine the realize engine power, economy and emission target technical route. According to the above implementation scheme and technical route, this paper made engine test, the results shown that the bench test could ensure operation stablely, and electrical control system can accurately control gas fuel, make each cylinder fuel distribution uniformity. Hence, engine's power, economy and emission performance have improved.In order to validate the simulated results,4108 LPG engine's structure parameters and its subsystems components were researched. According to the simulation results, under the different compression ratios (8 to 10), the engine performances are contrasted. And the experiment result shows that when the compression ratio is 9, the engine shows better power, economy and emission performance and low exhaust temperature. Under the most optimal compression ratio, by using successive optimization method, the distribution phase of camshaft with different overlap Angle (35°and 25°) and exhaust early open Angle (75°and 65°) is contrasted. The experiment results show that when overlap Angle is 35°and EVO is 75°, the ergine has high power and low gas consumption and exhaust temperature. In order to increase engine power and economy, the 4108LPG engine of the two different turbochargers (GT25A and GT25B) are studied. The experiment results show that: GT25B supercharger low-speed characteristics is poorer, cause engine torque is insufficient, but GT25A supercharger low-speed performance is better, the overall performance can satisfy the engine development requirements, especially in low speed conditions engine shows good performance and fuel economy, accords with the actual working needs, so be sure to choose. For improving the emission performance of the 4108LPG Engine effectively, oxidized catalysts is used in the exhausts processing, and reducing the emissions of carbon monoxide and hydrocarbon compounds greatly. Meanwhile, using Econtrols calibration software to conduct calibration experiment of the whole engine performance to get the optimal Parameter Map, and then, conducting static circulation experiment on the calibrated engine. The result indicates:the fuel economy and power of the 4108LPG Engine can meet development requirements, the vehicle emission is low and can achieve the countries III Emission Standard.