| Because the thermal efficiency of vehicle internal combustion engine is difficult to improve, waste heat recovery of vehicle internal combustion engine which is based on Organic Rankine Cycle is an effective way to improve the combustion efficiency of internal combustion engine. This thesis is targeted towards Organic Rankine Cycle on vehicle and mainly studies the following aspects.Firstly, the relationship between temperature, flux of exhaust-gas and speed, torque of diesel engine is analyzed by using exhaust-gas’ s parameters of a 4-cylinder diesel engine. A steady-state model of Organic Rankine cycle is built by Matlab and the outlet temperature, output work and exhaust exergy of Organic Rankine Cycle under different working conditions is analyzed. The result shows that fluctuation of heat source parameters is remarkable under different working conditions which causes performance of Organic Rankine cycle system to be unstable and steady-state model is insufficient to support effective analysis on Organic Rankine cycle. The result shows that when the rotate speed is in the range of 1200~2200RPM and the torque is in the range of 200~1300Nm, the range of exhaust gas temperature can keep 473~858K, the rate range of flux is 0.12~0.469kg/s. The range of the evaporator outlet temperature is 154~543℃. The range of net work cycle is 2.7~21.2kW, the range of exhaust exergy is 10.8~95.6kWSecondly, a dynamic model of vehicle’s organic Rankine cycle is built, and divided fluctuation of heat source into 6 models which were simulated respectively. The relationship between temperature, step time of flux, variable quantity of step time, initial value of step time and stable time of system is analyzed. It proposes that thermal storage can weaken fluctuation of heat source which affect on system performance. System setting time is related with temperature and flux step time linearly. There is a quadratic function between System setting time and initial step time and change of step timeThirdly, a flooded evaporator as a regenerative system is proposed, a dynamic model of heat release and heat storage are built, the effect on working substance in the procedure of heat release caused by setting back-pressure of evaporator, initial gas liquid ratio, and radius exit is analyzed and design parameter of this evaporator is optimized.Finally, the flooded evaporator is integrated into the Organic Rankine Cycle on vehicle, the effect of regenerative system on vehicle Organic Rankine Cycle in different cases, such as parking, decelerating and accelerating of different timings is analyzed.In conclusion, the regenerative system can weaken the effect of exhaust gas temperature and heat source fluctuation on expander’s inlet temperature, improving the output total work of Organic Rankine Cycle system effectively, which need switch regenerative operational mode to regenerative normal mode rapidly, maintaining the vapor quality in expander inlet at 1, protecting expander from wetness destroy. The change of expander inlet temperature were below 51℃ which is 162℃ less than without the regenerative system. |
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