Expansion Characteristics Of Middle-temperature Geothermal Power Generation Based On The Single Screw Expander

Single screw expander as a new type of expander has good stability. At present,the research of single screw expander technology is still in the stage of development.In this paper, experimental research and analysis of single screw expander dynamiccharacteristics has been studied, with single screw expander used in mediumtemperature geothermal power generation system as the background.In this paper, the corresponding theoretical research has been done based on thesingle screw expander for medium temperature geothermal power. The test system ofsingle screw expander has been designed and constructed. Experimental research,with compressed air and steam as working fluid respectively, has been studied.The main research contents are as follows:Firstly, single cycle and double cycle simulation systems of low temperaturegeothermal power based on the latest10kW single screw expander have beendesigned. The work characteristics of the different steam states under the rated flow ofexpander have been analyzed, and in the same heat absorption conditions, Single andbinary cycle have been compared. The results showed that, the work characteristics ofsaturated state and two-phase state were better, while superheated state was nocontribution to net power. In the same heat absorption, binary cycle system was betterthan the single cycle on thermal efficiency and power, but the difference was reducingwith the parameter of steam increasing.Secondly, the test system of single screw expander, with compressed air andsteam as working fluid respectively, had been designed and constructed. Someequipment had also been designed and manufactured. The problems of construction ofthe testing platform had been solved, and test equipment had been calibrated.Thirdly, with compressed air as working fluid, the power, efficiency, gasconsumption rate and temperature difference of single screw expander with rotationalspeed variation had been studied in an established experimental apparatus of singlescrew expander. The results showed that, the maximum speed of expander reached3393r/min, the maximum moment of torque reached22N·m, the maximum power ofexpander was up to4.4kW, and the maximum inlet flow rate was32.9m3/h. Themaximum temperature difference between import and export of expander reached45℃. The lowest gas consumption rate was up to55.2kg/kW·h, and the maximumtotal efficiency of expander reached58.8%.Fourthly, for the simulation of expansion characteristics of single screw expanderon medium temperature geothermal power, with steam as working medium, the power,efficiency and gas consumption rate of single screw expander with rotational speed variation had been studied in an established experimental apparatus of single screwexpander. Experimental study showed that, the maximum power of expander was upto3.9kW, the lowest steam consumption rate amounted to22.5kg/kW·h. Themaximum total efficiency of expander reached66%.Finally, the single screw expander has good expansion properties, and theapplication of that in geothermal field has a very good development potential andprospects. In this paper, the influence of the lubricating oil on the single screwexpander and the experimental research of the single screw expander in two-phasestate had not been studied. The mechanical seal of the single screw expander cannotmeet the high pressure and vacuum under the conditions of the experimentrequirements, and need to be further improved. The unfinished work above should beperfected in the further.