Study On The Hybridization Rate Of Parallel Hybrid Electric Bus

Hybrids are certainly an attractive technological option, since their improvedfuel efficiency can potentially provide solutions for three of the main problemsraised by transport: increasing demand for fossil fuels, greenhouse gas emissionsand pollution. Laboratory measurements, real life demonstrations and an increasingnumber of commercially available vehicles all suggest that hybrids can have acomparable performance to that of conventional vehicles while consuming up to30% less fuel and being environmentally friendly.However, as the precondition of the whole vehicle design, the way to selectthe hybridization rate of the power system of Hybrid Electric Vehicle(HEV) is notbeen sought in a certain theory yet, and the variation range of hybridization rate israther wide in the HEV of today's market. The thesis, supported by the Researchand Development of the Jiefang Hybrid Electric Bus(HEB) which is a sub-projectof the 863 Program of China, based on the software ADVISOR, systematicallystudies the selection of the hybridization rate of HEB's power system.Firstly, the thesis introduces the type selection results and work characters ofthe main hybrid components of HEB, such as internal combustion engine, ACelectric motor and NiMH batteries;because the study on hybridization rate , with acertain control strategy, adopts combination method of theoretical research andanalog simulation, the thesis introduces the HEB's parallel electric assistant controlstrategy and software ADVISOR, and analyses the modeling achievement of themain hybrid power components in ADVISOR.Secondly, based on the driving energy demand, the thesis analyses the drivingpower demand of the HEB, and chooses the total power 160KW, which is almostsame to the maximum engine of traditional bus, and is convenient to compare HEBwith a traditional bus. Then, by employing different hybridization rate , studies thepower and fuel economy performance, including engine driving alone, motorstarting the vehicle and engine, engine and motor in united driving mode, and, withdifferent hybridization rate, effect on vehicle fuel economy of HEB in Beijing,Shanghai, Changchun driving cycle.Thirdly, the number of the batteries could be designed according to that powerdemand of batteries should satisfy the power demand of motor in the whole driving,based on which, the thesis studies the relationship between the mass difference ofhybridizing the power system and the selection of hybridization rate, the effect onvehicle performance caused by mass difference;the thesis also analyses the cost ofthe main components in HEB(especially NiMH battery), interprets the relationshipbetween the increase cost of HEB with economies of scale and the differenthybridization rate, especially studies the effect on the ultimate estimate economicreturns, the return term of increase cost of HEB with the different hybridizationrate, the outlook for the future is more positive.Finally, based on the former simulation results, using the curve fitting of dates,combining the lowest technology targets of the vehicle design and other controlobjectives, including the best fuel economy objective, the maximum estimateeconomic returns objective, the minimum return term of increase cost objective, thethesis makes hybridization rate an optimal selection;the thesis also uses the theoryof orthogonal optimal design, selects target and factors of orthogonal experiment ofHEB, constraint conditions and appropriate orthogonal experiment table,establishes orthogonal experiment schemes, then, the thesis carries out the designof orthogonal simulation experiment of HEB, analyses the effect level of economyperformance of HEB with different hybridization rate, and ultimately finds out anoptimal experiment scheme and hybridization rate.The thesis is about the fundamental research contents of Jiefang HEB design,and not only makes some guide meaning for theoretical design and development ofHEB, but has some practical meaning for final market target of HEB.