Stepless Capacity Control for Reciprocating Compressors
In recent years, there has been increased interest in stepless, also called infinite-step, capacity control systems for reciprocating compressors. This paper will describe the different methods used to provide stepless control in sufficient detail to allow a user to evaluate them. Each system has different attributes and each will have its area of application. A discussion of the benefits and limitations of each type will allow a user to determine the most suitable method for each application. If the compression ratio is low and the mount of turn down required is high, a system that delays suction valve closing will be required. In other cases, a stepless system based on a variable clearance pocket may give a more simple, lower maintenance solution.