In recent years, diesel engine is developing rapidly in the direction of high power and super long stroke, which requires higher strength of its key moving parts. Connecting rod is one of the key moving parts of diesel engine which is subjected to complex alternating load during the working process. This loading condition has a great influence on its structural strength and reliability. In the proposed study, the strength and fatigue of a low-speed diesel engine con-rod made of 42CrMoA are analyzed. The 3-D model of the con-rod assembly built in the proposed study. The stress distribution and deformation of the con-rod assembly under the maximum explosive pressure are presented and studied. In the present paper, fatigue safety factor of all parts of con-rod assembly under the maximum explosive pressure condition is checked. According to the results carried out from the proposed work, the corresponding alternating stress is 340MPa, while the fatigue limit of 42CrMo material is above 430-540MPa, which means that the con-rod parts work under the alternating stress far below the fatigue limit. The kirasushvili method is adopted in the present paper as the standard of safety factor evaluation of con-rod. According to the allowable safety factor table of kirasushvili method, the minimum safety factor of the big and small ends of the con-rod and rod body can meet the requirements without fatigue damage.
The structure and properties of diesel fuel injection system directly influence the performance of diesel, and calculation and analysis are important methods to improve engine performance. So, by analyzing the structure, math models and working process theory of the electronic control PPVI fuel injection system, this paper founds initial and improved simulation models of the diesel electronic control PPVI fuel injection system, completes simulation and analysis. The simulation results show that the improved model has better cushion effect than the initial model by adding a constant pressure delivery valve between the nozzle and electromagnetic valve, what is more, the improved model can avoid the instability of the work state, such as second injection, cavitation and anomaly injection, etc., therefore, the diesel forms perfect unloading characteristic, and its performance has also been improved.
Adopting a three-dimensional contact finite element method, with complex connecting rod group assembled body model of computation, the fatigue strength of the connecting rod of a certain type of diesel engine was verified. A transient stress analysis was conducted on the connecting rod. Compared with the connecting rod static stretching and compression test, the three-dimensional contact finite element method, which was used to analyze the strength of the connecting rod subassembly, was feasible. Based on the three-dimensional contact finite element method, the connecting rod transient stress analysis results showed that the maximum stress of the connecting rod did not occur under the highest pressure of the cylinder, and the dynamic stress value was less than the static stress value.
Adopting the contact finite element method, with complex connecting rod group assembled body model of computation, the fatigue strength of the connecting rod of a certain type of diesel engine was verified. A transient stress analysis was conducted on the connecting rod. Compared with the connecting rod static stretching and compression test, the contact finite element method, which was used to analyze the strength of the connecting rod subassembly, was feasible. Based on the contact finite element method, the connecting rod transient stress analysis results showed that the maximum stress of the connecting rod did not occur under the highest pressure of the cylinder, and the dynamic stress value was greater than the static stress value.
In order to solve cylinder outbreak problem of high pressure, the blowoff system has been added at transformation process from conventional turbo diesel engine to sequential turbocharing diesel engine. Set up air bleeder valve model of diesel engine sequential turbocharing high condition based on SIMULINK software platform and the air bleeder valve regulated by fuzzy PI control strategies, when the stable operation and in low load conditions of diesel engine, analyses the burst control effect as increase the amount of fuel delivery at different situation. The simulation results show that the model has fast response, high control accuracy and good control effect of high burst pressure, achieve control of diesel engine performance, fuel economy and reliability.
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