| Due to the advantages of economy, good durability and low CO2emission, in21st century the diesel engine will continue to be the main power for transportation. But the emission regulations become increasingly strict, the high NOx and PM emission issues are getting more and more challenging, which need further improvement of combustion process for diesel engine. At present, the ideal fuel injection system is pressure-time electrical high pressure common rail fuel injection system, which has high injection pressure and can be adjusted according to demand. It could control the injection timing and quantity accurately and flexibly, and make the ideal injection rate curve fulfill the required conditions, thus it become the study focus of diesel engine technology and is wildly applied.This paper focuses on the study of high pressure common rail system (HPCRS), introduces the development and present status of HPCRS and analyses the mechanism to improve emission for HPCRS, also in this paper the author completes the selection and design of componentsand parts of HPCRS for a certain engine, and introduces design process of the whole HPCRS.In the design process, the type of common rail system for new developed engine is first determined by calculation and analysis. Single cylinder calculation method is established, the correctness of the calculation method is verified through test values from the test bed, and the specification of injector nozzle is determined by use of the single cylinder calculation method. Then based on the single cylinder method, the whole HPCRS model is established, and simulated calculation is carried out for the whole HPCRS under typical operating conditions of the diesel engine,the rationality of the system is estimated through the deviation of injection quantity in each cylinder. By adjusting the system structure, parameter, the deviation of injection quantity in each cylinder is controlled within a reasonable range, then according to the calculation results design the common rail system. Under typical working conditions, the pressures in injection orifice, injection nozzle and injector accumulator are calculated for the final scheme. Finally through the test and verification for the correctness, good effect is obtained for matching the engine, and the economic performance as well as the emission performance can fulfill the expected targets. In the test, by adjusting thefuel supply advance angle and the rail pressureunder each working conditions, the MAP figure has been found out for the best economy and emission. |
