Design And Optimization Of Pneumatic Attachments For A Heavy Truck With Flat Head

With the continuous development of domestic highways,the driving speed of heavy trucks is also increasing.With the rising of oil price and the aggravation of environmental pollution,it is urgent to improve the fuel economy of the heavy trucks.Energy saving and emission reduction has become the current research upsurge.Heavy truck with flat head plays an important role in heavy truck,so it is of great significance to improve fuel economy of heavy truck with flat head.In the above-mentioned domestic environment,this paper relies on the Sino-US Clean Energy Joint Research Center(CERC)project(the Sino-US joint research on key technologies for improving the energy efficiency of mid-load and heavy-duty trucks,project number: 2017YFE0102800)to research.A domestic flat head heavy truck is taken as the research object to optimize the aerodynamic drag reduction of the flat head heavy truck.The main process includes: basic numerical simulation calculation of the flat-head heavy truck;design and calculation of pneumatic attachments;EGO global optimization;wind tunnel test.In the meantime,the author is been invoved in this project.First of all,the design and analysis of the pneumatic package are carried out.In this paper,the 1:1 model of a flat head heavy truck is numerically simulated and calculated,and the flow characteristics of the basic model are deeply studied.Three vehicle aerodynamic sensitive areas are determined,i.e.tractor area,tractor and trailer spacing area.Ten independent pneumatic devices have been designed in the aerodynamic sensitive area.One of the marine animal bionic drag reduction accessories has obvious drag reduction effect,and the drag reduction rate is 15.0%.Through the combination of pneumatic accessories,the combination of pneumatic components is obtained,and the drag reduction rate is 27.4%.Secondly,the global optimization of the combination package is carried out.Four kinds of additional devices are selected as the optimization object,and the aerodynamic drag coefficient is taken as the objective function.In order to obtain more accurate optimization results,this paper uses the optimal Latin hypercube to extract the initial samples,obtains the initial sample model through the parametric modeling method,and carries on the numerical simulation calculation to the initial sample model,uses the initial training samples to establish the initial Kriging agent model.The de differential evolution algorithm is used to iteratively optimize the response surface of the agent model,and the maximum point of EI iterative function is output.If the requirements(maxei < 0.1%)are met,the iterative optimization is stopped and the corresponding optimization results are output.Otherwise,the set of design variables corresponding to maxei will be added to the last sample point set.95 sample points are used in the whole optimization process.The results show that the drag reduction of the optimal combined aerodynamic accessory is 3.7% compared with the combined aerodynamic accessory and 30.1% compared with the basic model.In this paper,by introducing the global optimization algorithm of ego(efficient global optimization),not only the calculation cost is saved,the optimization efficiency is improved,but also the optimization results are accurately output.The global optimization algorithm of ego is based on EI iterative optimization function and Kriging agent model,in which Kriging agent model instead of numerical simulation can save calculation time and cost,EI function is the final stop iteration criterion to accurately search for the global optimal solution.At last,the 1 / 20 and 1 / 8 scale reduction experiments were carried out in the laboratory of low turbulence wind tunnel of Northeastern University of Japan and arc scale reduction wind tunnel of the United States respectively.In the 1 / 20 scale wind tunnel experiment,the aerodynamic parameters of the basic model and the optimal combination model are measured,and the flow state of the top and side of the container is measured by the oil flow method.In the 1 / 8 scale experiment,the aerodynamic drag coefficients of each independent aerodynamic package,basic model,combined model and optimal combined model are obtained.The results of two experiments show that the drag reduction effect of the optimal combination model is equivalent to that of the simulation calculation,which proves the accuracy of the optimization algorithm and the simulation calculation.In this paper,the aerodynamic drag reduction of a heavy truck with flat head is studied by combining numerical simulation,global optimization algorithm of ego and wind tunnel experiment,which provides a reference for the design of the heavy truck with flat head in the future.