Slide Valves for Single-Screw Expanders Working Under Varied Operating Conditions

Yuting Wu,Jingfu Wang,Wei Wang,Huan Wang,Chongfang Ma,Guoqiang Li,Ruiping Zhi,Biao Lei

doi:10.3390/en9070478

Abstract

This paper fully describes the working principle of slide valves in single-screw expanders (SSEs). A geometric analysis of suction and volume ratio slide valves is presented to determine the relations between volume ratio, suction closure volume, discharge opening volume and slide valves displacement. An organic Rankine cycle (ORC) thermodynamic model with SSE integrated with slide valves is developed to analyze the power output of SSE and the net power output of ORC system and variation law of slide valves displacement. Analysis of a typical ORC system under changing operating conditions shows that the power output of the expander and the net output power of the ORC system with slide valves are much better than those without slide valves. When the condensing temperature is 40 °C and the waste availability is 80 kW, the increase in output power and net output power are approximately 3.4 kW and 5 kW, respectively. The presented geometric analysis of slide valves and the thermodynamic model integrated with slide valves can be used to provide a theoretical and technical basis for designing the slide valves of SSEs and the control strategies of slide valves under varied operating conditions.

Highlights

With increasing concerns about energy shortages and environmental pollution, low-grade waste heat recovery technology for power generation has received much attention in the past decades.Various low-grade heat recovery technologies have been developed and are currently employed in diverse applications such as solar thermal power [1], geothermal energy [2,3], biomass energy [4,5], and engine exhaust gases [6]
The results showed that the maximum organic Rankine cycle (ORC) efficiency was 6.48% when the output power of diesel engine was 250 kW and the single-screw expanders (SSEs) torque was 64.43 Nm
The rotary speed of the adjusted by slide valves maintained at 3000 rpm and the optimum shaft efficiency is thought as 60%

Summary

Introduction

With increasing concerns about energy shortages and environmental pollution, low-grade waste heat recovery technology for power generation has received much attention in the past decades.Various low-grade heat recovery technologies have been developed and are currently employed in diverse applications such as solar thermal power [1], geothermal energy [2,3], biomass energy [4,5], and engine exhaust gases [6]. With increasing concerns about energy shortages and environmental pollution, low-grade waste heat recovery technology for power generation has received much attention in the past decades. Expanders come in two types: dynamic (turbine) [8,9] and positive displacement (volumetric) [10]. Such as rotary vane [11,12,13,14], scroll [15,16,17,18,19], twin screw [20], single-screw [21,22,23,24,25,26,27] and reciprocating expanders [28]. In the development of expander technologies for small-scale ORC units, the single-screw expander (SSE) has gained popularity because of its superior characteristics of balanced loads, small

Objectives

Results

Conclusion