Research On Thermodynamic Performance Of Twin Screw Expander Based On Rotor Profile Analysis

Expander is one of the core components of organic Rankine cycle.Its thermal performance directly affects the thermal efficiency of the system cycle.In previous studies,the calculation of the thermal performance of the twin-screw expander was mostly obtained through the isentropic enthalpy difference method,and there were few studies based on the geometric characteristics,resulting in the lack of universal conclusions on the relationship between the structural parameters and the thermal performance.Therefore,from the perspective of mathematical analysis,this paper proposes a model of the geometric characteristics of twin-screw expander based on rotor profile analysis.Through the analysis of the influencing factors of thermal performance related parameters,the overall operation of the device in the system is improved.The purpose of efficiency.In this paper,starting from the analysis of the rotor profile of different twinscrew expanders,the unilateral asymmetrical-toothed-arc rotor profile is considered as the research object;the mathematical model of the rotor profile is established according to the meshing principle,and the key geometry for the calculation of thermal performance is established.The variation of the area of the feature parameters and the volume of the primitives was studied.Both of them were calculated by the proposed meshing sequence method.Based on the obtained area of the base element and the volume of the base element,the thermal performance of the twin-screw expander is calculated,and the parameters including the diameter of the rotor,the lead,the twist angle of the male rotor,and the internal expansion angle are obtained.Influencing law: The theoretical volume flow and isentropic athermal power have a positive correlation with the diameter and lead of the rotor;the theoretical volume flow increases with the increase of the male rotor torsion angle,and the isentropic power is monotonous with the male rotor's torsion angle and internal expansion angle.Decrease relationship;thermal performance is used as an objective function according to the influence laws,and the nonlinear programming method is used to optimize the structural parameters of the twin-screw expander.Again,based on the open system energy equation and the mass conservation equation,combined with the optimized volume change of the working chamber,a mathematical model for the actual working process of the twin-screw expander in the presence of a leak is established;the determination of the use of Runge-Kutta The method calculates the microscopic characteristics of the working process model.Finally,according to the consistency between the results of the mathematical model of the twin-screw expander and the ideal process,the correctness of the differential equations describing the working process of the expander is verified.The analysis shows that the leakage leads to the power of the expander shaft.The reason for the decrease is mainly caused by the pressure difference between adjacent working chambers;by changing the operating parameters such as rotation speed,suction pressure,suction temperature,etc.,on the actual operation status of the twin-screw expander,the variation rule of the operating characteristics of the expander is obtained: Increased suction pressure makes the expander shaft power and adiabatic efficiency continuously improve;the speed increases by 3000 rad/min,the adiabatic efficiency increases by 5.12%;the suction pressure increases by 300 k Pa,the adiabatic efficiency increases by 10.1%;and the suction temperature affects the expander.The effect of thermal performance is less.In this paper,based on the mathematical model of the rotor profile,through the analysis and study of the influencing factors of thermal performance,the structural parameter optimization method and operational performance improvement recommendations are proposed to achieve the safe and efficient operation of the twinscrew expander and improve the organic Rankine cycle.Low-temperature waste heat recovery has important practical significance.