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

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.

A Review of Recent Research and Application Progress in Screw Machines

“…Liu et al [48] and Wang et al [103] proposed semi-empirical models for optimizing the built-in volume ratio of TSCs with slide valves for refrigeration applications and heat pump applications, respectively. Wu et al [104] further analyzed the relations between volume ratio, suction closure volume, discharge opening volume, and the displacement of the suction and volume ratio slide valves for a SSE used in an ORC system.…”

“…Wu et al [150] concluded that the optimal built-in volume ratio was not the bigger the better when SSE worked at high pressure ratio condition, because suction pressure loss also increased with the increase of built-in volume ratio. The [104] further presented that adopting slide valves can effectively improve the power output of the SSE and the net power output of the ORC system. Bianchi et al [149].…”