A New Design of the Tooth Profile for Single Screw Compressors
The wear of star wheel teeth is an importance issue in the single screw compressor. In order to enhance the wearresistance of star wheel teeth, some new profiles of the meshing pair were proposed to replace the currently used straight line envelope profile, such as single column envelope, multi-straight line (or multi-column) envelope. In this paper, a curved surface of the tooth flank is suggested. The groove flank is the envelope surface corresponding to the curved surface of the tooth flank. Section profile of the new tooth flank is a curved line, which could be elliptical, hyperbolic or involute. During the tooth meshing with the groove, the contact line between the tooth flank and the groove flank could move back and forth in the whole area of the tooth flank. This design is expected to improve the lubricating between the tooth flank and the groove flank, and to prolong the service life of the single screw compressor. Geometric and kinematic investigation of the star wheel and the screw rotor is established. And a new designed tooth flank of the meshing pair is introduced in this paper. Numerical control high-velocity cutting technology is suggested to fabricate the new star-wheel and the screw rotor.
Development of single screw compressor technologies and their tendency
Single screw compressor (SSC), a strong competitor of the twin screw compressor, is regarded as an excellent gas compressor because of symmetrical structure and balanced gas forces on the screw rotor. However, the market for the SSC is tiny compared with that for the twin screw compressor because of the serious abrasion of star-wheel teeth. In recent years, this problem has been solved due to the development of the new profiles of meshing pairs, and the SSC has attracted more attention due to its high application potential for low-temperature heat pump, mechanical vapor recompression, and two-phase expansion. Nevertheless, there are still many technical problems remained to be solved for applying SSC to these fields urgently. In this paper, a comprehensive review on the progress and development of SSC technologies is presented. The review first combs the current situation of SSC products. Besides, the design and processing of meshing pairs are clarified and analyzed. Moreover, the working process of SSC and its performance in new applications are discussed in detail. Finally, the further research direction of the SSC is also discussed, which will be beneficial for designing high-efficiency SSC.
Development of polyamide curable modified epoxy novolac resins with improved adhesion and chemical resistance
Purpose – To prepare modified epoxy resins from resorcinol, cresol and phenol for improved adhesion and chemical resistance. To evaluate the properties of such modified epoxy resins.Design/methodology/approach – Epoxy novolac resins (ENRs) were synthesised by condensing epichlorohydrin with novolacs based on different types of substituted phenols for improving adhesion and chemical resistance. Various compositions were made by incorporating different proportions of polyamide resin. The chemical and adhesive strengths of the conventional epoxy and the modified epoxy resins were characterised.Findings – The modified ENR using substituted phenols showed significant enhancement of chemical and adhesive strengths over the conventional DGEBA resin. The modified ENR had an increased number of glycidyl groups (thus increased functionality) of resin, which was responsible for improved chemical and adhesive strengths over the conventional DGEBA resin.Research limitations/implications – The EPN resins used in the pr...