Research On Powertrain Trade-off Of The Heavy Duty Truck

With the rapid development of transportation, the Vehicle freight is takingmore proportion and has being become the fundamental mode which plays animportant role in the economy growth of China. With the increas of the vehiclepopulation and the extensive use of the heavy duty truck, more and more fuel isconsumed. Statistics indicates that automobile fuel consumption occupies thegasoline and the diesel output 87% and 21% respectively in China. So it proves thatthe automobile is the main consumer of the petroleum. About 100 million tons ofpetroleum was imported in 2004 and it is estimated that in 2010, when the numberof the vehicle will reach 60 million, the capacity of input oil in China will reach1,800 million tons. The demand of energy aggravates the shaortage intensely,therefore the automobile performance required is much higher than before,especially for the considering of the economy. How to reduce the consumption ofthe fuel under the condition of guaranteeing automobile dynamics always is a focusof automobile profession researching on.The optimizing of powertrain trade-off is an effective measure to solve theproblem of fuel-consumption and dynamic property by automotive design, which isa focal question in the field of automobile. The unceasing progress of the computertechnology and the unceasing improvement of the mathematical arithmetic take aneffective method for powertrain matching of the heavy duty truck.Overseas study on model formulation and the software development work ofautomobile dynamic property and the fuel economy began from the 1960s. InChina, the study on the aspect is later than the other countries and began from thelate 1980s.However, early research is not adopt to the rapid development ofautomotive technology, thus further research on this aspect is necessary. Thefollowing aspects will be studied.Referring to the research all over the world, the paper establishes theevaluating index of dynamic property and fuel economy , as well as entireautomobile integrative evaluating index, which includ loss ratio of driving power,constant speed fuel consumption of 100km, the fuel consumption of circulation testand energy utilization ratio. Evaluating index of dynamic property and integrativeevaluating index of the entire vehicle are non-dimensional figures, valuing between0 and 1, which is convenient to pick out the better, comparing with the traditionalevaluating index. It can also reflect the matching degree of automobile powertrain,the exertion degree of the engine power and the difference between the engineoperating condition corresponding to the automobile actual operating condition andthe perfect operating condition, as well as the potential and the possible ofapproach of powertrain.Mathematics model of engine-torque characteristic and engine mappingcharacteristics is established. It proves that the mathematics model can meet therequirement of simulation on the dynamic property and fuel economy of the heavyduty truck in some precision by comparing with experimental value and calculatedvalue. Correct establishment of mathematical model is the foundation for othercalculation and analysis about dynamic property and fuel economy.Transmission efficency model of transmission and driving axle and shiftingmode of the dynamic property and fuel economy are established, which make theresults of simulation much more veracious.According to the theory of vehicle and the test requirement of NationalStandard on fuel economy and dynamic property, the simulation method ofdynamic property and the fuel economy of the heavy duty truck is established. Theprogram calculating the evaluating index of dynamic property and fuel economy isdesigned by Matlab. It is verified that the program is reasonable, correct andapplicable through comparing with experimental results and simulation results,which is the foundation for the next calculation and analyses.Based on the manufacture mode of the heavy-duty truck, the paper putsforward to a sort of methods solving how to choose the powertrain for betterautomobile characteristics, including how to choose engine type, maximum enginepower, engine peak speed, maximum engine torque, transmission ratio and drivingaxle ratio, and to make certain the parameter of engine and transmission system. Inorder to ensure the dynamic property and fuel economy of the heavy duty truck,according to actual demand, this paper chooses the felicitous driving axle ratio onthe graph about loss ratio of driving power and the fuel consumption of circulationtest.Besides the powertrain, there are lots of factors that affect the dynamicproperty and fuel economy of the heavy duty truck, such as gross weight, rollingresistance coefficient, drag factor, windward area, drive-train efficiency, and so on.The degree of influence on the dynamic property and fuel economy of the heavyduty truck from is successively drive-train efficiency, gross weight, rollingresistance coefficient, drag factor and windward area. This paper points out thedirection what and how to do when the heavy duty trucks are designed again.