A Novel Screw Compressor with a Shunt Enhanced Decompression and Pulsation Trap (SEDAPT)

Abstract

When operating at pressures outside of their design point of a screw compressor, under- or over-compression would occur due to the deviation of the compressor cavity pressure from outlet pressure, and compressor efficiency suffers and pulsation and noise worsen. To solve the discharge pressure mismatch issue, some sort of control system is necessary, such as a variable volume ratio (commonly referred to as variable Vi) slide valve design. These systems, however, frequently have complex structural design, high price, large size, and significant dependability issues. Additionally, they are ineffective for commonly used dry screw applications in which oil is not allowed to lubricate the moving slide-valve parts. It has been widely known that a bicycle tire pump or rotary piston or scroll compressor equipped with an automatic discharge valve (one way valve), such as a reed valve, can operate over a wide range of pressures without suffering either an under-compression or an over-compression. The underlining principle of the bicycle pump has thus far NOT been fully explored for controlling the over compression or under compression problems of a screw compressor in general. This paper introduces a self-sensing and self-correcting screw compression process that can be derived or deduced from the Perfect Gas Law by optimizing for multiple design criteria such as best compression efficiency, pulsation/noise abatement, and cost and footprint reduction when operating over a wide range of pressures. The resulting schemes, called SEDAPT (Shunt Enhanced Decompression And Pulsation Trap), in contrast to an alternative scheme called SECAPT (Shunt Enhanced Compression And Pulsation Trap) (Huang et al. in A novel screw compressor with a shunt enhanced compression and pulsation trap (SECAPT), 2022), is then investigated and further honed numerically by a proprietary COMPUTATIONAL MODEL code for a dry screw case: a bulk truck loading application where compressor pressure varies from no pressure rise to maximum load. The numerical simulations illustrate that SEDAPT is tentatively capable of achieving multiple targets as theorized from the Gas Laws.