Single Screw Expander Research Articles

Influence of intake pressure on the performance of single screw expander working with compressed air

In order to meet the demand of small expander in the field of waste heat recovery, distributed renewable energy, gas liquefaction and compressed air vehicles, a single screw expander with 175 mm diameter rotor is developed in our lab. An experimental system using compressed air has been built to test the performance of single screw expanders. The experiments were conducted for different intake pressure, and important parameters were measured, such as flow rate, intake and exhaust temperature, output power and rotating speed. The influence of intake pressure on the performance was obtained. Results indicate that satisfactory power output and economic performance can be obtained at high intake pressure and high rotational speed, meanwhile a good working efficiency is maintained. The speed of 2800 rpm is considered as the best working speed, and fitting formulae are given for dynamic performances versus intake pressures. The highest overall efficiency that can be reached is 55% and the maximum output reached is 22 kW. The preliminary experimental study indicates a very good working performance for the first generation of self-developed single screw expanders.

Study and Selection of Working Fluids for Organic Rankine Cycle (ORC) Using Engine Waste Heat Energy

In this paper, a basic ORC system is proposed to recover the exhaust gas energy of vehicle engines, and the mathematical model of the ORC system is built. Thirteen working fluids are analyzed. The main criterion for selecting working fluids is the mass flow rate and the heat absorption rate under the same power output of single-screw expander. Then, the paper presents an analysis of the irreversibility rate and thermal efficiency of the ORC system using 4 different organic working fluids.

Pure Working Fluid Selection for the Organic Rankine Cycle in Waste Heat Recovery of Diesel Engine

According to the analysis of heat balance, about 1/3 of the fuel combustion heat is taken away into the ambience by exhaust gas of diesel engine. Depending on the characteristics of the diesel, this paper uses a special system to recover this waste heat, in which the organic Rankine cycle is combined with a single screw expander. The economy should be improved by using this system in the diesel. The model of this system is designed in Matlab combined with REFPROP. Using this way, the thermodynamic parameters should be calculated and the thermodynamic properties of this system with different working fluids should be analyzed. At last, R245fa, R245ca, R123 and R141b are selected as the alternative refrigerants used in this system.

Efficiency Analysis on Low Temperature Energy Conversion System Based on Organic Rankine Cycle

The amount of low temperature heat resources is very huge, efficient utilization that energy is very important issue for improving energy efficiency, saving energy and protecting environment. Due to the small available energy of low temperature heat source, how to improve thermodynamic efficiency is the key problem. In this paper, the thermodynamic model of low temperature thermal power conversion system based on organic Rankine cycle was described firstly. Turbine, single screw and piston expanders were briefly described. R123, R245fa and R134a were chose as working fluid because of quite different critical temperature. Based on this model, the influence of thermodynamic property of organic working fluid on the efficiency of low temperature thermal power conversion system was discussed. The calculating result showed that R123 is the best choice if no considering the impact of expander types and that R245fa is the best choice if considering the impact of expander. This conclusion indicated that it is very important to investigate the match relationship between working fluid and expander. Moreover, single screw expander was proved to be more suitable than turbine and piston expanders for low temperature heat power conversion system.

Comparative Analysis of Electric Power and Steam Loss Rate between Single Flash and Binary Geothermal Power System with Single Screw Expander

In this paper, cycle efficiency, net electric power and steam lose rate are calculated between the single flash and binary geothermal power system. The prime mover is 10kW single screw expander. These parameters of the single flash system are calculated by rated inlet volume flow rate of the single screw expander. The heat absorption capacity of both systems is determined to be equivalent. The working fluids of binary system are R134a, R245fa, and R600a. Those parameters of binary system are calculated with the condition that the saturated temperature of the working fluid before pump is 22°C. Engineering Equation Solver (EES) software is used for analysis. The results show that electric power of the single flash system is on the rise and steam loss rate of the single flash system is on the decrease with an increase of the inlet temperature between 100°C and 155°C. From the same heat absorption capacity, the binary system has apparent improvement in electric power and efficiency. The efficiency of binary system can increase by 2.1% compared with single flash system.

Research of Two Stage Single Screw Expander Organic Rankine Cycle System Scheme Based on the Waste Heat Recovery of Diesel Engine’s Exhaust Gas

According to the analysis of heat balance, about 1/3 of the fuel combustion heat is taken away into the ambience by exhaust gas of diesel engine. In this article, to improve the using level of the fuel’s combustion heat, a two stage single screw expander organic Rankine cycle (ORC) system has been used to recover the waste heat from exhaust gas of a certain turbine diesel engine. In this article, physical model of the recovery system was built at first, then the T-S curve was drawn, at last, REFPROP was used to calculate thermodynamics parameter in different state point of this system, and analyze the whole system’s thermodynamics character. By analyzing, the evaporation temperature of this system should be optimized to get the relatively evaporation press; by calculating, it could be seen that the middle heater in this system should be taken away to improve the economy of this scheme. This scheme should supply a direction for the exhaust heat recovery of diesel engine.

Preliminary experimental study of single screw expander prototype

Abstract Efficient heat conversion of low temperature heat source is a key problem for energy saving, especially in the fields of waste heat recovery and renewable energy utilization. At present, technical bottleneck for low temperature thermal power is lack of suitable prime mover. As the core component of general machinery, single screw has many good features, including balanced loading of the main screw, low leakage, low noise, low vibration and long working life, etc. If single screw technology is applied to the field of expander, more efficient prime mover would be possibly obtained, compared with pistol expander, scroll expander and twin screw expander, and so on. In order to verify the performance of the prototype, the function experiment was made. In this paper, compressed air was used as working fluid and performance test for the prototype was finished at conditions including different intake flow, different humidity, constant torque, and constant rotational speed. From the experimental data, it is shown that the power output is 5 kW, exhaust temperature is −45 °C, difference between the import and export is about 62 °C, in the conditions of inlet pressure at 0.6 MPa and rotational speed 2850 rpm. The test results also show that the single screw expander has good part load characteristics. From the analysis of experimental data, we found that adiabatic efficiency of the prototype is not so high probably because of poor lubrication. The lubrication problem will be considered in the next work.

Performance study on three-stage power system of compressed air vehicle based on single-screw expander

A new compressed-air engine system based on three-stage single screw expander was proposed to improve the performance of power system. Three different structure styles were presented, and the studies on the power performance and the distribution of expansion ratios between stages were carried out by programming and mathematical modeling of each style. Research results indicated that the best matches of expansion ratios with equal heat temperature for the air tank of pressure 30 MPa were seven- five-three for “first-stage heating” style, eight-five-three for “two-stage heating” style and five-five-four for “three-stage heating” style, respectively. Results also showed that heating up inlet air or increasing the expander efficiency might improve the power performance. The output power of the “two-stage heating” style is far higher than that of “first-stage heating” style and is a little lower than that of “three-stage heating” style. The new system showed good structure and power performances.

Research of Air Powered Engine System Using Two-stage Single Screw Expander

A new compressed air engine system based on two-stage single screw expander is proposed to increase the energy utilization rate of compressed air.The distribution of expansion ratios between stages is optimized by building mathematical optimal arithmetic model with variable metric method and is checked by programming calculation.The influence of total efficiency and heating temperature on the power performance parameters including total output work and air consumption rate is analyzed.Research results indicate the best match of expansion ratio is ten to seven(nine to seven and nine to eight are also good) for the same inlet temperature system with air tank of 30 MPa pressure and 300 L volume.Results also show that heating up inlet air or increasing the system efficiency can improve the total output work and reduce the air consumption rate.It is concluded that the compressed air engine system combined two-stage single screw expander with heating is better than single-stage system.

00/01172 World energy prospects to 2020

Increasing energy-demand and environmental concerns are leading to a growing interest in alternative and sustainable energy solutions. Low-grade waste heat recovery through ORC systems is considered to be one of the most feasible eco-friendly energy conversion technologies.In this paper, a comprehensive model of an organic Rankine cycle (ORC) system for micro-CHP applications is presented in order to compare the behavior under part-load conditions of two types of positive displacement expanders, a single-screw expander and a scroll expander. The ORC model is implemented in the AMESim® environment, which allows system modeling both for steady-state and transient analysis. Typical residential electrical and heating loads are considered to study the performances of a suitable small-scale system.By means of a detailed quasi-1D model for a single-screw expander and a Reverse Engineering (RE)-Computational Fluid Dynamics (CFD) approach for a scroll expander, the performance characteristic maps of both expansion machines, in terms of isentropic efficiency as function of expansion ratio and rotational speed, have been determined and implemented in the AMESim® model.A comparison between the selected expanders is presented to address the influence of different positive displacement-type expanders on the overall ORC performances at off-design conditions. The capability of the system to meet the requested loads is also discussed.