| As the shortage of energy supply and the deterioration of environment, the energysaving and environmental protection work is in desperate need. The utilization of theindustrial waste heat is an important step to the energy saving and environmentalprotection work, especially for the waste heat with temperature below250℃. As oneeffective way of the waste heat recovery for power generation, the Organic RankineCycle (ORC) system gradually shows a remarkable economy benefits, but is seldomapplied due to the immaturity of the domestic ORC expander technology. Given thesignificance of the ORC system and its turbine technology to the waste heat recovery,this dissertation does the research and design of the low-temperature ORC system andits turbine. Then the500kW class ORC testing system and its radial turbine are studiedand designed according to a certain enterprise’s demand of validating and popularizingthe ORC technology.This dissertation establishes the design and analysis system of the ORC system, forstudying the influence of the cycle parameters on the ORC thermal performance. Thisdissertation also studies the selecting of the suitable organic working fluids for thelow-temperature waste heat with different temperatures, and the influences of theworking fluids’ thermal properties on the ORC thermal efficiency and system economy,the organics’ environmental impact and the turbine design. According the demand ofrecovering the five waste heat sources with their temperatures ranging from98℃to215℃from a1.2million ton/a reforming and extraction unit, the waste heat recoverysystem using ORC is studied with the principle of the energy gradient utilization and thecomprehensive distribution of the heat sources. The ORC system using single workingfluid but with two evaporation section was proposed to make the system simple andcompact as well as reduce the cost, while ensuring the system output power. In theproposed ORC system for the reforming and extraction unit, R141b is used and30.3%of the mass flow rate is evaporated at the high temperature and60.9%is evaporated atthe low temperature.According to the characteristics of the organic turbine: high expansion ratio andlow enthalpy drop, and the characteristics of the organic working fluid: small molecular weight and low speed of sound, the aerodynamic design and performance predictionmethod of the radial turbine in the ORC system are studied, and an one-dimensionaldesign system and a three-dimensional (3D) numerical analysis system for the turbineperformance are established. The500kW-class model turbine for the ORC test rig withR123as working fluid is designed, combining the analysis of the predicted turbineperformance. The radial turbine’s aerodynamic design and performance are validatedand analyzed by the3D numerical simulations. The numerical simulation results agreewell with the one-dimensional design. For the appearance of the strong shock wave andlocal separations, this dissertation uses NURBS curve technology to control the profileshape, uses3D numerical simulation to analyze the aerodynamic performance, andutilizes the combination of genetic algorithm and sequential quadratic programming tooptimize the turbine nozzle and impeller. Results show the increase of the turbineefficiency, and the inhibition of the separation zone on the impeller suction side. Theturbine efficiency after the optimization increases by about1.05percent. The backwardimpeller further improves the flow field.With the performance map of the radial turbine, the design and off-designthermodynamic performance of the500kW-class ORC test rig is studied, for thepurpose of providing reference data to the test rig running and controlling. The turbinehas been manufactured, and its vibration test using the steam is20μm. This test rig isunder construction, and experiments are expected to start in the early2014. The testresults are of crucial use for the industrial application of the ORC system and its turbinetechnology. |
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