Development and Experimental Study of the First Stage in a Two-Stage Water-Flooded Single-Screw Compressor Unit for Polyethylene Terephthalate Bottle Blowing System

Abstract

The oil-free compressor is a key component in fabricating polyethylene terephthalate (PET) bottles for beverages and water. At present, the main compressor type used for blowing PET bottles is the reciprocating compressor. However, compared to screw compressors, reciprocating compressors have shortcomings of high energy consumption and too many consumable parts. Many manufacturers of PET bottles in Asia are seeking to replace reciprocating compressors with screw compressors, as we know. Screw compressors can be classified as single-screw compressors (SSC) and twin-screw compressors. Since the load in a twin-screw compressor is far larger than that in an SSC, SSCs are more suitable for being developed for high-pressure applications such as PET bottle blowing. This paper presents a performance study on an oil-free single-screw compressor as the first stage of the PET compressor unit. A 5.4 m3·min−1 prototype and its test rig were developed. The thermophysical process of the moist air is theoretically analyzed. The pressure loss on the flow path and the influence of the important parameters are experimentally investigated. It is found that water vapor cannot be separated during the adiabatic compression process. The results also show that the pressure loss from the discharging duct to the check valve accounts for the largest percentage of the total pressure loss. The experimental results further show that the discharge capacity and shaft power increase almost linearly with the motor speed. The efficiency declines with increasing injected water temperature. The discharge capacity and shaft power all increase with the injected water flowrate, and an optimum flowrate is found to ensure a highest isentropic efficiency. With the increase in discharge pressure, the discharge capacity decreases, and the shaft power increases. The isentropic efficiency is found to have its maximum value at a certain discharge pressure.

Influence of water injection parameters on the performance of a water-lubricated single-screw air compressor

“…Studies on WLSSAC performance remain limited. Li et al examined the impacts of different meshing pair lines on a single-screw compressor's hydrodynamic lubrication parameters using both theoretical and experimental approaches and determined that an optimal impact of water lubrication can be obtained using the multiple cylindrical meshing pair [12][13][14][15]. Yet, there has to date been no study on the impact of water injected parameters on compressor performance.…”

A Review of Recent Research and Application Progress in Screw Machines

“…As for single-screw machines, the two-stage water-injected SSC unit gains popular application for polyethylene terephthalate bottle blowing system, but the stability of SSC is hard to be guaranteed in practice [6,126]. Furthermore, the scholars at Beijing University of Technology [40,60,[127][128][129][130][131][132] carried out lots of experimental studies on self-developed SSEs using compered air as the working fluid.…”