【作者】

Alkan Göcmen

【摘要】

该论文已在赫尔辛基举行的第28届CIMAC大会上发表，论文的版权归CIMAC所有。The proper layout of the accumulator function in a common rail system (CRS) is crucial for the competitiveness of the CRS in terms of costs and benefit. The accumulator function can be realized in various ways. It can be built up by a modular system that allows using the same accumulators and connecting parts in engines with different numbers of cylinders or by the integration of a manifold (common rail) that feeds several injectors. Accumulators can be integrated into the injectors. The accumulator function can alternatively be integrated into the fuel pipe line system between the high pressure pump and the injectors. A systematic approach is presented for the identification of an optimal layout of the accumulator function in diesel engines with a power output in the range between 1 and 5MW by taking into consideration of the engine layout conditions, hydraulic and lifetime requirements, manufacturability and manufacturing economies as well as assembly and maintenance requirements. The effects of various design layouts of the accumulator on the hydraulic performance and fatigue life has been studied by means of hydraulic simulations and fatigue calculations using an inline six cylinder model engine with 1750kW power output and a nominal operation pressure of 2000bars. Two fundamentally different approaches for the accumulator function have been studied in detail. In one approach the system is built-up in a modular way, whereas an accumulator of 500 or of 80cm3 volume content is integrated into the injectors. In a second approach the CRS was built-up using a one piece accumulator (rail) with 500cm3 volume content. In both approaches the damping effect of orifices on pressure fluctuations was studied. For the rail variant the damping effect of additional, small sized 40cm3 single accumulators, which can be integrated into the injector or in front of the injector, was additionally studied. Hydraulic performance is discussed in terms of the pressure drop within the injector, injected discharge rate development over one cycle, amount of injected fuel per cycle as well as their reproducibility from one cylinder to the other. It was shown that the best combination with respect to a minimum drop of the injection discharge rate and to a reproducible injection discharge rate function can be achieved with two fundamentally different approaches: (1) by a modular system with 500cm3 accumulator integrated injectors in which pressure pulsations within the jumper lines are dampened by orifices and (2) by a non-modular common rail system with a 500cm3 one piece accumulator, which is stabilized against pressure pulsations within the injector by means of additional 40cm3 single accumulators that are placed in front of the injector or integrated into the injectors. Under given design boundary conditions a slight but visible advantage of variant (1) over variant (2) in terms of the reproducibility of the injection discharge rate function from one cylinder to the other is found. Damping of pressure pulsations is found to be crucial for the high pressure capability (fatigue life) under nominal operation conditions at the working pressure of 2000bar. The relevance of the hydraulic characteristics diminishes when fatigue lifetime is governed by a high number of start-up/shut-down cycles. As long as advanced requirements in regard to hydraulic performance and fatigue life can be realized with a modular set-up with large accumulator integrated injectors as well as with an optimized CRS based on an external accumulator system, the decision for either of these approaches must be made dependent upon given engine layout conditions, cost targets, manufacturing opportunities and preferences with respect to assembly and maintenance works. The relative strengths and weaknesses of studied variants are briefly discussed in relation to the above mentioned decision criteria.

【会议名称】

第28届CIMAC会议

【会议地点】

芬兰 赫尔辛基

【下载次数】

2

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