Performance Study Of Steam-liquid Two Phase Power Generation System Using Screw Expander With Medium-low Temperature Heat Source

China is the world's second largest economy.However,energy consumption per unit of industrial production is 2.2 times higher than the that of the world average,which makes improving energy efficiency and developing renewable clean energy the main direction of energy structure adjustment.Therefore our country's industrial waste heat and renewable energy such as solar energy and geothermal energy are expecting bright prospects for development.Screw expander for medium and low temperature heat source in gas-liquid two phase power generation technology has profound significance on energy saving and emission reduction,because it can not only recycle the industry waste heat,but also can be used in geothermal power generation.Apart from serving as a theoretical guidance for engineering practice,this paper through establishing three models including organic fluid two-phase power generation,total flow power generation and two-stage system power generation,with the help of theory analysis is to study its performance under the condition of middle and low temperature heat source.At first,organic fluid steam-liquid two phase power generation model was established with the heat source being exhaust gas from gas turbine power plant.Factors,such as evaporating temperature,working medium dryness at exit of evaporator and the ambient temperature are studied,because of their influence on power generation performance.Besides,the reasons of different performance under varying cycle parameters are analyzed by first and second law of thermodynamics.Results show that when the evaporating temperature rises,the system has a higher power potential.With regard to a given evaporating temperature,when the dryness at the evaporator exit increases,the system has a descending power potential.Furthermore,the ambient temperature affects the performance of system as well,for when the former moves up,the latter will go down.Apart from that,for geothermal heat source,the total flow power generation system was set up.Based on the relationship between screw expander efficiency and expansion ratio,the relation between the power machine inlet dryness and the system net power was studied.Then,total flow power generation System performance was analyzed and compared with ORC when the heat resource temperature ranged from 90 to 150?.And results show that at power machine inlet an optimal dryness do exist,which can maximize the system net output power.When the heat source temperature is between 90 to 130?,total flow power generation system shows a better performance.However,if the heat source temperature moves above 130?,the ORC system works better.Therefore,total flow power generation system is more suitable for heat source with certain degree of dryness,because it can reduce the energy loss of throttling.At last,total flow power generation system was connected with ORC power generation system to form a double-stage system,whose performance was analyzed under the heat source temperature from 130 to 150? by comparing how the super heater and internal heat exchanger work in the double-stage system.Furthermore,a model of energy loss is established to analyze the reasons of these systems with different performance.Results show that the double stage system with super heater and internal heat exchanger works very well,for considering the net power,thermal efficiency or energy efficiency,it all has a superior advantage.Super heater and internal heat exchanger have huge influence on the system.When the double-stage system has only a superheater,its performance tends to be weakening.Therefore,only with both super heater and internal heat exchanger,the system will function improvingly.