| With the rapid development of automobile industry, people increasingly depend on oil fuel. Recent vehicles mostly use common fuel internal combustion engine, even the higher thermal efficiency of internal combustion engine, primary energy converted into mechanical power efficiency is low, the exhaust carrying heat accounts for about 40% of the total fuel consumption. If we recover the automobile exhaust energy, we can improve the power and thermal efficiency of internal combustion engine, reduce the emissions. Therefore, exhaust waste heat recycle has become a hot spot in the field of energy saving. Organic Rankine’s circulation waste heat recovery technology has great application prospect with high energy utilization, becoming the main way of vehicle internal combustion engine waste heat recovery.Based on the mainstream technology of organic Rankine’s circulation waste heat recovery system, regarding to variability of the exhaust waste heat, instantaneous degeneration characteristic and recovery of waste heat from internal combustion engine exhaust gas energy by way of diversity, this paper puts forward the introduction of heat storage single shaft power(supercritical heat and latent heat storage using regenerative type space, variable expansion ratio) of organic Rankine cycle vehicle composite system for internal combustion engine waste heat utilization. This paper first introduces supercritical thermal storage temperature control module of after processing system and variable expansion ratio of single shaft power recovery system. Based on heat storage uniaxial work organic Rankine’s cycle simulation model, this paper explores energy recovery of waste heat from internal combustion engine in the steady-state condition, the effect of the variable expansion ratio under different thermodynamic state on recovery efficiency and transient operating conditions of supercritical thermal storage stability potential of exhaust gas temperature; According to the simulation model to build laboratory prototype system test and study the key links.(1)Theory combined with the simulation to study core parts structure parameters(expansion ratio)、control parameter of the system(working substance、the thermal physical parameters of each link)on the key of thermal process and the influence rule of system efficiency(thermal-machinery)at the steady state under the all working state of exhaust gas residual heat:a)Under the steady state condition,the expander efficiency will increase step by step with the increase of working substance evaporation pressure; under the evaporation pressure-C25 、 1.1MPa, the expander efficiency is the highest, the result is 84.44 percent.Equivalent recovery efficiency will increase slightly with the increase of the organic working substance evaporation pressure,equivalent recovery efficiency will decrease step by step with the increase of the load,under the small load,equivalent recovery efficiency is higher. Under the evaporation pressure-C25、1.1MPa,equivalent recovery efficiency is the highest.b)Total power and the equivalent recovery efficiency of expander will firstly increase and then they will decrease with the increased of expansion ratio,when the expansion ratio is 6,total power output and the equivalent recovery efficiency achieve the optimal level,19.894 k W and 31.221 percent respectively.(2)Study and evaluate single shaft work organic Rankine’s circulatory system, the space back to thermal characteristics is introduced into single shaft work of waste heat recovery system, explores variable expansion at different thermodynamic state influence on heat recovery efficiency single shaft work space of the organic Rankine’s circulatory system.a)The optimization of working substance evaporation pressure and temperature can make the expansion machine at the best power output level, in a certain temperature, thermal efficiency gradually increased with the increase of pressure; Under the same pressure, as the heat substance temperature rise gradually, the thermal efficiency reduce, heat substance temperature at 200℃, pressure at 34 bar,thermal efficiency is best. Exergy efficiency rise with the increase of the pressure under a specific temperature. When the pressure is constant efficiency decreases with increasing temperature.b) By changing the hot working substance injection time, realize variable expansion ratio.Unit mass torque, thermal efficiency, exergy efficiency and back thermal efficiency increased linearly as expansion ratio increase, the isentropic efficiency decrease slightly.(3) Supercritical heat storage device reveals the potential and heat utilization(post-processing inlet temperature control) satisfaction,at the transient condition,waste heat recovery is converted into mechanical energy(expander output power), clear about the thermodynamic energy grade ascending roots: in the region of high performance,quality of the working fluid of is the most sensitive factors of thermal storage;in the region of the middle and low performance with the increase of working fluid quality, the sensitivity of the mass flow rate increases. High-performance area average temperature(320℃), availability(about 96%), satisfaction(about 79%) and comprehensive index(0.7) has a relatively high level and low standard deviation(about 58-68), high performance area(2-6 kg) is the optimal area, to provide 4 kg with 1.0 kg/s mass flow rate working fluid quality strategy is the optimal scheme.(4) The laboratory prototype system was built on the simulation platform, and conduct research and evaluation on the key link: the pneumatic motor performance test results show that the pneumatic motor output power increase with the increase of rotational speed firstly and then reduce; pneumatic motor conversion efficiency decrease with the rotating speed booting; under specific speed, the optimal expansion ratio of maximum efficiency exists, based on the experimental model expansion ratio of 1.09 performance is better. ORC of pneumatic motor test results show that the burner can realize simulation of a heavy vehicle exhaust within the 1160 s. heat exchanger in the 405 s can make the working substance evaporation temperature and pressure were 127.25℃ and 2.03 bar of overheating; With evaporation pressure gradually increasing, the torque and power output of pneumatic motor increase when the temperature is the same. And the maximum power point gradually goes backwards.Under the condition of evaporation pressure 2.2bar and large expansion ratio(2D), torque and power output of the motor is larger, and maximum power is 22.3% higher than 1D.On the level of application, pneumatic motor-ORC provides technical guidance for waste energy recovering industrialization application based on ORC. |
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