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.
A Design Method of Engaging Couple Profile of Single Screw Compressors Enveloped by Multi Straight Lines
AbstrcatThis paper introduced a new design method of rotor teeth profile and star-wheel teeth profile enveloped with multi straight lines in a single screw compressor.A teeth grove surface of a single-screw is repeatedly machined by a specially designed lathe with straight-lined cut feeding in different directions and positions,and these directions and positions of cut feeding are reasonably determined,so that,different regions of a generator on a teeth surface can be machined by different cut feedings.Recording to all those straight lines in different directions and positions,we can construct an ideal star-wheel teeth profile with these lines.The screw rotors and star wheel teeth profile machined in this way will provide excellent engagement in the compressor operation.It is predicted that this engaged couple will have less wear,better sealing in operation and have more easily manufacturing property and lower cost.
Evaluation of buckling load and dynamic performance of steel shear wall retrofitted with strips made of shape memory alloy
One of the most imperfections of the steel shear wall is out of plane displacements that cause severe damage in both structural and non-structural elements. In this paper, the effects of shape-memory alloys on steel shear walls are investigated. First, a numerical analysis using the finite element method in ABAQUS software has been carried out according to an experimental test. The results of the numerical analysis have been verified with experimental results. Next, shape-memory alloy fibers have been added vertically and horizontally to various parts of the steel shear wall. The results show that retrofitting with the shape-memory alloy reduces the out-of-plane displacement of the steel shear wall under both cyclic and seismic loadings. Besides, the buckling load in the steel shear wall increases when it is retrofitted with the shape-memory alloy. Also, the total out-of-plane movement (accumulated absolute displacements) of the steel shear wall and non-structural damage are controlled by the characteristic of a shape-memory alloy material called “super-elastic”.