Developement and Demonstration on Single Screw Expander in Organic Rankine Cycle

orc2019 Tracking Number 49

Single screw expander is a machine which can realize volume change by means of a screw and two gaterotors. Single screw expander was recognized as the best volumetric expanders for the advantages of ideal force balance, low leakage, low noise, low vibration, long life , low maintenance cost , hige pressure ratio, etc. Based on the gear theory and spatial relationship between single screw rotor and gate rotor, mathematical models on the profile of CP-type, PP-type, CC-type and PC-type structure are established. The groove volume of the four types of structure are derived. And the unwrapped helix of single screw rotor deciding the suction size and discharge position are obtained. Moreover, the changing rules of groove volume and volume ratio are quantitatively analyzed.Developed a generating processing technology and 2 sets of special machine tools to massive manufacture screw rotors from Φ20 to Φ450mm at high precision and low cost. The cutting tool and moulds for machining the gate rotor have been successfully designed and machined. Thermo- fluid dynamic models and performance testing system of single screw expander were established. Influences of clearance height, lubrication oil. rotating speed, pressure and temperature on single screw expander were investigation by experiments and numerical simulations. Compound slide valve adjusting capacity and internal volume ratio regulation simultaneously were proposed to improve the single screw expander performance under different operating conditions. Developed six module single screw expander prototypes in wide power range from 5kW to 172 kW. A double-stage single screw expander by utilizing the discharge velocity of screw grooves was developed. Experimental result indicates that the developed single screw expander performed well under different expansion ratio conditions. The coefficient of discharge velocity utilization achieved 0.42. An optimized single screw expander ORC system working with R123 was developed, the maximum efficiency achieved 9.3%. Four demonstration projects were established respectively with solar and internal combustion engine waste heat.