Design And Optimization Of Impeller For Ship's Marine Exhaust Turbocharger

In the 21 st century,the energy problem and environment problem is becoming more and more attention.Pressurization technology can effectively improve the fuel economy of the internal combustion engine and reduce the concentration of harmful substances.Therefore it is widely applied in automobile,shipbuilding,aerospace and so on.Centrifugal compressor is the core of the turbocharger components,its design quality directly determines the performance of the compressor,thereby affecting the effects of pressurization.Therefore,to improve the efficiency,increase the compression ratio and broaden the scope of work has always been the hot spot of the researchers.At present,to use rotating mechanical design software for the structure design of the impeller and fluid analysis software for numerical simulation of internal flow of centrifugal compressor is to ensure the compressor the effective means of highly efficiency and safety work.Firstly,The paper established one dimension formula of aerodynamic optimization design on the basis of the theory of the centrifugal impeller.The import optimization design was to minimize relative Mach number of the shroud.And close to the real situation of impeller loss model was established.On the premise of guarantee level stage pressure ratio unchanged,to use loss model check export design and optimization for export.Then it can calculate diffuser structure and performance,according to the geometry of impeller outlet and pneumatic parameter.Blade geometry molding method are introduced at the same time,this paper adopted the Bladegen module to complete the blade shape of centrifugal impeller.Secondly,on the basis of the above theory,using the Matlab language compiled the centrifugal impeller optimization design calculation procedures and variable condition prediction procedures.Take Krain centrifugal impeller,for example.Comparing with this program calculation results with the experimental results,the results showed that under the design conditions,the calculative geometric parameters of this paper was roughly identical to geometric parameters of the literature,and impeller efficiency was accordance with the experiment.But the stage isentropic efficiency was a bit low,within the allowable range of error.And comparing under different working conditions of the machine performance,stage pressure ratio calculation resulted coincide well with the experimental results,proved the validity and reliability of the design method and program in this paper.In order to better fit the engineering practice in Chongqing Jiang Zeng machinery co.,Ltd,an exhaust gas turbocharger centrifugal impeller design requirements and performance index for the task,the calculative geometric parameters of this paper were compared with actual centrifugal impeller parameters,the parameters of the two slightly different.But the level of efficiency was lower than experiment,as with Krain centrifugal impeller.Using CFD for numerical simulation of the centrifugal impeller at the same time,the simulation curve coincided well with the experimental results,verifies the feasibility and the accuracy of the numerical simulation method in this paper.Finally,the optimal design of the impeller blade was carried out.This paper proposes a method by stage pressure ratio and isentropic efficiency such as quantitative approach,then the multi-objective optimization would be converted into single objective optimization,avoided to each objective function to make trade-off optimization.The Bezier curve control points was used for parameterized blade.The uniform design was to determine the test sample database,the performance of the sample data is obtained by CFD analysis corresponding response value.The quality of approximation model which was built by the traditional response surface method,the random improved response surface method and regular improved response surface method were compared.By eliminating redundant items,the approximate model precision established by response surface method was increased by about 1.5%.Then iterative optimization using GA determined the optimized impeller.Results showed that the regular improved response surface method,no matter from the approximate model fitting precision,the iterative optimization effect and calculation efficiency,were superior to the traditional response surface method.At the same time,it was verified that the selection of no error center in the improved response surface method has a significant effect on the quality of the approximate model,and the effect of the regular improved response method was optimal by using the method of this paper.The stage pressure ratio of optimized impeller for the final increased by 3.76%,the efficiency increased about 3.3 percentage points.Contrast analysis of the optimized impeller with original impeller Mach number distribution,static pressure distribution and velocity distribution in the meridional plane,the results proved that the optimized impeller at static pressure of export was improved,the hub separation loss reduced significantly,and the distribution of static pressure and Mach number were more uniform and smooth.It indicated that optimized impeller improved mechanical impeller internal flows.