查看更多>>摘要：An experiment was conducted to analyse the local heat transfer and flow characteristics in the viscous coupling unit (VCU) of a crossover utility vehicle (CUV). Heat is transferred by free convection and forced convection, and affected by the lubrication effect of the smooth wall and the embedded circumferential ribs, at various rotational speeds. In the simulation of the practical operational range of VCU of CUV under experimental conditions, both rotational speed and geometric parameters must correspond closely to the real situation. In addition, the test section is designed such that the cooling characteristics of the power transmission system of the CUV of actual size could be investigated. The overall temperature distribution is measured and the local heat transfer coefficient is analysed. The impact of the centrifugal force upon the Taylor vortex is clarified with reference to the flow-field distribution. Finally, some empirical formulae by CUV designers are obtained from the experimental results.
查看更多>>摘要：A methodology for the accurate description of three dimensional track geometries is proposed. Cubic, Akima and shape preserving splines are proposed for track parameterisation. The track description uses Frenet frames that provide the track referential at every point. During dynamic analysis a pre-calculated database is linearly interpolated to form the kinematic constraints that enforce the wheelsets of the vehicle to move along the track with a prescribed angular orientation. This approach allows calculating the reaction forces that develop between the vehicle and the track. The formulation is discussed emphasizing the influence of the parameterisation methods to construct the track geometry.
查看更多>>摘要：The mathematical modelling of a suspension unit is considered. The unit comprises a hydraulic cylinder connecting the vehicle body to the unsprung mass, two nitrogen-filled accumulator springs and two damper ports. The model takes the deflection rate as input and iteratively employs simple fluid dynamics theory to calculate the flow-rates from each accumulator to the cylinder. It calculates the pressure in the accumulators by time-integrating the flow rates to determine the gas volumes and then invoking ideal gas theory. This renders the dynamic force of the unit as output. Model predictions are compared with measurements.
查看更多>>摘要：This paper presents the modelling technique and dynamic simulation results of fuel cell and engine Hybrid Electric Scooters (HES) using the bond graph approach. The first example is on a fuel cell-battery hybrid scooter, in which the zero pollution fuel cell is the major powerplant, also acts as the battery charger. The second case study is on a typical engine-motor-regenerator-battery HES. It mainly consists of a brush-less direct current motor/regenerator and a 4-stroke direct injection spark ignition engine. They are interconnected in parallel by a continuously variable transmission. Detailed differential equation sets as well as simulation results are presented. A fuzzy auto-pilot control rule was employed to simulate the vehicle performance under typical driving pattern conditions.
查看更多>>摘要：The properties and calculation methods of axial vibration of high-speed automotive engine crankshafts are studied in this paper. First, the two main excitations that induce axial vibrations are analysed. Then a simplified model and the calculation method and analytical procedures are deduced by the application to the crankshaft of an online six-cylinder diesel engine. At last the axial vibration is measured at the front end of the crankshaft using a newly designed torsional/axial/bending 3-D vibration-testing device to verify the modelling and the results of the theoretical calculations. It was observed that the analytical results were very close to the actual measurements.
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