| With the update of energy consumption mode, the dependence and consumptiondemand on the energy increase day by day in nowadays society. As an important supportingpart to the development of industry, the automobile industry relies more serious on the fossiland oil resources. China owns larger auto production and consumption power, the carconsumption for oil energy would become the important factors which restrict thedevelopment of country economy and auto industry. Therefore, improving the overallperformance of engines by recovering the waste heat form the exhaust gas has become oneimportant technical means.Based on the above condition, we analysed the mainstream technologies about recoveringheat from exhaust gas in the world, and proposed a variable expansion ratio waste heatrecovery system coupling ORC in this paper. The technical route of whole paper is thattaking variable expansion ratio as the core and aiming at taking full use of the latent heat ofworking fluid. And we definite the technical structure of waste heat recovery which dependson the free piston expander (FPE) and variable expansion ratio pneumatic motor expander(VEPME). First, thermodynamic process and the key sensitive factors of ORC were analysed,and then the operating principle of two expanders which owned the function of variableexpansion ratio were introduced respectively. At last, we built up simulation models andexperiment beds of two expanders coupling ORC to evaluate and analyse the performancesof two combination structures.Research and evaluation of ORC-FPE, studying performances and recovery efficiency ofORC-FPE through the combining mean of simulation and test bed: (1) Experiment evaluation of the ORC-FPE similar system: according to the simulationresults, we select related components to build up the actual similar system. Changing thepressure of working fluid which flow into the evaporator by the pump, the work convertingefficiency, heat-exchange efficiency of evaporator and total efficiency of system underdifferent pressure were studied. Results show that the best performance of system (of whichthe work converting efficiency is12%, heat-exchange efficiency of evaporator is62%, andtotal efficiency of system is6.5%) is get when the pressure of working fluid is0.6MPa.(2) Simulation research and evaluation of ORC-FPE which assists compressing gas:ORC-FPC model that assist compressing gas was built up with GT-suite software and theparameters of the key parts were selected based on the analytical data. Results indicated thatthe feasibility of the system could be validated based on the present model. First, influencesof ratio of the power piston area to the compression piston area () and different outputpressures of gas on the system were studied through GT-suite simulations. Results showedthat when varies from2.5to5.0, the effective efficiency of FPC (,) in five cyclesdecreased gradually, while the indicated efficiency of FPC (,) in five cycles firstlydecreased and then increased. When was2.5, the model achieved the bestperformance, of50.7%and, of23.7%). Within the range of the target CNG’soutput pressure (11-14bar),, and, decreased with the increase of the outlet pressure,and the best performance of the system was obtained at11bar (, of53.2%and, of26.5%).And then, influences of thermodynamic state of working fluid and input power werestudied. Results show that when the heated working fluid is at11.5bar and383K, the systemachieves better performances than other thermodynamic states, of which is601.1mg/KJand is44.3%. Based on the optimum thermodynamic state and the principle of obtain themaximum, the specific input power determined by (332g/cycle) and (1.2s/cycle) can make the system achieve a better performances, of which is648.9mg/KJ and is42.8%.(3) Simulation research and evaluation of ORC-FPE which assists outputting work: Themodel of ORC-FPE which assists outputting work is built up in the GT-suite to studyinfluence on this system under different clearance. The feasibility of the model is verifiedfrom the system operating condition. Meanwhile, the percent of damping loss can nearlyrepresent the percent of friction loss in the total because that there is no availableparameter to set for simulating the friction condition in the GT software. Results show thatndecrease about9.5%at0.3mm-clearance comparing with the initial condition withoutclearance. Nevertheless, friction loss (about20%of) will vanish based on theoreticalanalysis and can make up the loss ofn, as a result,nof ORC-FPE can increaseabout10%at0.3mm-clearance.With the improvement of the processing technology, theincreasing proportion ofncan be improved to a higher level.Research and evaluation of ORC-VEPME, studying function of variable expansion ratioand performances of ORC-FPE through the combining mean of simulation and test bed:(1) Simulation research and evaluation of ORC-VEPME: the simulation model basedon the GT-suite software, which could realize the function of variable expansion ratio andsubstitute the ORC-VEPME, is built up to study the influence of different factors on thesystem. The feasibility of the system can be validated from the operating curve of motor andPID control plots. First, influences of thermodynamic states on the system were studiedthrough GT-suite simulations. Results show that higher temperature and pressure of workingfluid benefits performances of system. And then, influences of injection angle of workingfluid and clearance volume on the system were studied through GT-suite simulations. Resultsshow that the best performances of the system can be obtained when the injection angle is30ATDC and clearance volume is0.03L. (2) Performance research of the VEPME: we designed the actual motor according to thepatent which has received the national invention patent license. Then, the test bed of VEPMEis built up to explore its function of variable expansion ratio. Taking the compressing air asthe working fluid, the performances of VEPME under different expansion ratio and workingpressure are studied, and results show this motor can realize its designed function andbenefits the later research.(3) Experiment evaluation of the ORC-FPE similar system: according to the simulationdata, the key conpoments of ORC were selected to build up the intergral ORC-VEPMEsystem test bed, which could provide foundation for later experiment. |
PDF Full Text Request