Abstract
Supercharging is the main method to improve the output power of marine diesel engines. Nowadays, most marine diesel engines use turbocharging technology, which increases the air pressure and density into the cylinder and the amount of fuel injected correspondingly so as to achieve the purpose of improving the power. In a marine diesel engine, the turbocharger has become an indispensable part. The performance of turbochargers in a harsh working environment of high temperature and high pressure for a long time will directly affect the performance of diesel engine. Based on the market feedback data from manufacturers, the failure modes of compressor impeller, turbine blade, and turbine disk of marine diesel turbocharger are analyzed, and the statistical model of random factors is established. Using DOE design, the structural strength simulation data of 46 compressors and 62 turbines are obtained, and the response surface model is constructed. On this basis, Monte Carlo sampling is carried out to analyze the reliability of the compressor and turbine. The reliability of the compressor is good, while that of the turbine disk is 0.943 and that of the turbine blade is 0.96, which still has the potential of reliability optimization space. Therefore, a multiobjective optimization method based on the NSGA-II genetic algorithm is proposed to obtain the multiobjective optimization scheme data with the reliability and processing cost of turbine disk and blade as the objective function. After optimization, the reliability of turbine disk and blade is 1, the stress value of turbine blade is optimized by 4.7941%, the stress value of turbine disk is optimized by 3.0136%, the machining cost of the turbine blade is reduced by 15.5087%, and the machining cost of turbine disk is reduced by 3.9907%. At the same time, it is verified by simulation, the data based on NSGA-II multiobjective genetic algorithm are more accurate and have practical engineering reference value. The optimized data based on NSGA-II multiobjective genetic algorithm are used to manufacture new turbine samples, and the accelerated test of simulation samples is carried out. The cycle life of the optimized turbine can reach 101,697 cycles and 118,687 cycles, which is 51.75% and 77.11% longer than that of the unoptimized turbine. It can be seen that the optimized turbine can meet the requirements of the reliability index while reducing the manufacturing cost.
Highlights
With the continuous consumption of fossil energy, energy and environmental problems are becoming increasingly serious
E stress cloud diagram of the turbine disc can be obtained through structural strength analysis, as shown in Figure 24(a). e maximum stress of the turbine disc is 967.25 MPa. e simulation value is 2.6735% different from the optimized value in Table 13. e stress cloud diagram of the turbine blade is shown in Figure 24(b). e maximum stress of the turbine blade is 755.88 MPa, and the simulation value is 4.3178%, different from the optimized value in Table 13. e difference between the two values is less than 5%. erefore, the data obtained by using the NSGA-II algorithm for 6Sigma reliability optimization are considered to have high engineering reference value
Results show that the maximum structural strength of the compressor is 373.73 MPa, which is less than the yield strength of 600 MPa when the TC4 material is at 400°C and above, and the structural strength meets the requirement for materials
Summary
With the continuous consumption of fossil energy, energy and environmental problems are becoming increasingly serious. Erefore, it is necessary to study the structural reliability of marine low-speed diesel engine turbochargers under high temperature and high-pressure conditions. Is article analyzes the structural strength of the key parts of the turbochargers of marine low-speed diesel engine designed and produced by a company under the severe complex load. Based on the response surface method and Monte Carlo sampling method, the reliability analysis of the turbocharger compressor and turbine of the marine lowspeed diesel engine is carried out. Is article will provide a theoretical reference for the structural design and improvement optimization of marine low-speed diesel engine turbochargers and has direct practical application value According to the optimization results, the accelerated test of the simulation sample is carried out. e results show that based on the multiobjective optimization algorithm, the turbine can meet the requirements of the reliability index while reducing the processing cost. is article will provide a theoretical reference for the structural design and improvement optimization of marine low-speed diesel engine turbochargers and has direct practical application value
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