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As a new type of fluid machinery, the disc-seal single screw pump (DSSP) is vital for energy conversion in oil sludge energy recovery systems and natural gas liquefaction system due to the advantages of wide flow range, strong self-absorption and well adaptability to organic solid impurities. However, no research work has focused on the working mechanism and performance of this pump at present, which makes its application limited. In view of this, the in-depth theoretical study on the meshing characteristics and operating performance of the DSSP must be carried out. In this paper, the profile equations of the meshing pair and the working process mathematical model were established for the first time based on three-dimensional space meshing theory, coordinate transformation principle. By using this model, the working performance of this pump was investigated, and the influence mechanism of the profile parameters on the theoretic volume was analyzed. The results of the analysis show that DSSP has the best leakage characteristics when the seal disc rotation center fell on the screw rotor touchline. All these analyses can provide the theory basis for improving the performance of the pump and optimized design of the meshing pair.

The disc-seal single screw pump (DSSP) is the key devices for liquid refrigerant conveying. However, there is little research on the suction capacity of this pump at present, which makes its application limited. In view of this, a mathematical model of the suction volume was established firstly based on the three-dimensional meshing theory. By using this model, the suction capacity calculation model was put forward, and the suction capacity and the impact mechanism of working parameters on it were investigated. The theoretical calculation results are in good agreement with the actual engineering data with the deviation not more than 6.5%. The results obtained by this validated model show that DSSP has abundant suction capacity with a suction capacity far more than 1 and the suction capacity varies in inverse proportion to density and rotation speed. All of these studies can provide theoretical basis for improving the performance of the DSSP.

In single screw compressor (SSC), the inner surface of the working chamber has always been a key issue that affects oil application and heat transfer. However, the geometric characteristics for the inner surface of the working chamber in SSC with Multicolumn Envelope Meshing Pair (MEMP) have not been carried out yet. Therefore, in this paper, a geometric model of working chamber inner surface for the SSC with MEMP is established to predict the geometric characteristics of the working process. The presented model is verified as a powerful tool for geometric characteristics analysis by the simulation results. With the validated model, the geometric characteristics of the working process and the effect of MEMP structural parameters on the geometric characteristics and the working performance for the SSC with MEMP have been analyzed. Through the comparison of the inner surface area with different structural parameters, optimization analysis of the structural parameters can be obtained. All of this work can provide the basis for the later heat transfer analysis and optimization structural design of the SSC.

In single screw refrigeration compressor (SSRC), the wear of meshing pair has always been a key issue that restricts its development. In order to solve this problem, a Multicolumn Envelope Meshing Pair (MEMP) was proposed. However, the theoretical research on wear resistance of MEMP has not been carried out yet. Therefore, in this paper, a theoretical calculation model describing the influence of the MEMP profile parameters on wear characteristics of the SSRC with MEMP is established to predict the wear resistance. The presented model is verified as a powerful tool for wear characteristics analysis by the experimental results. With the validated model, the effect of MEMP profile parameters on the wear characteristics of SSRC has been analyzed. Optimization analysis shows that in the design stage more envelope columns with a larger center distance and larger envelope column diameter should be chosen for the MEMP to get a better wear resistance.

A geometric model of a 1-pair of circular arcs modified wrap (1-CMW), the existing circular arc modified wrap (CMW), was developed. In order to improve the performance and overcome its shortcoming of the CMW, a novel n-pair of circular arcs modified wrap (n-CMW) for scroll compressors was proposed based on the midline design method. A 2-CMW was analyzed, and then a general geometric model of n-CMW with arbitrary pair number n was established. In addition, the generation procedure, general mutual dependence of geometric parameters as well as equations of wrap profiles were obtained, and the influence of geometric parameters on shapes of the n-CMW was analyzed. Flow simulations of the 1-CMW, 2-CMW, 3-CMW and 4-CMW during the working process with the same conditions were conducted. Study results indicate that the proposed n-CMW increases the built-in volume ratio and design flexibility, and is superior to the existing CMW.

The Multicolumn Envelope Meshing Pair (MEMP) is a significant influence factor of single screw compressor (SSC) performance. It is necessary to carry out an optimization study on MEMP to improve the SSC performance. In this paper, a theoretical calculation model containing three leakage influencing factors is presented to research the influence of the MEMP profile parameters on the leakage characteristics of the SSC. Experiment investigations on the performance of a SSC with MEMP are carried out to verify the theoretical calculation model. With the validated model, the effect of MEMP profile parameters on the leakage characteristics of SSC has been analyzed. Optimization analysis shows that in the design stage more envelope columns with smaller center distance and larger radius should be chosen for the front side of the MEMP, but less envelope columns with smaller center distance and smaller radius should be chosen for the back side of the MEMP.

A novel design methodology has been proposed based on the equidistant curve approach for constructing the complete meshing profiles (CMPs) of scroll compressors. The CMPs, including the peripheral profiles and central profiles for both the orbiting and fixed scrolls, can be generated simultaneously by offsetting the midline in the convex and concave direction. Three examples of the CMPs, named the circular arc modified wrap, circular arc add line modified wrap and asymmetric circular arc modified wrap, have been designed and illustrated by using the proposed design method. Geometric models of these three CMPs are established. Effects of geometric parameters of the modified wrap on performance of the scroll compressor are analyzed. The discharge pressure under the same suction volume of the scroll compressors with these three modified wraps are compared using numerical simulation. Results show that the discharge pressure of the circular arc modified wrap is bigger than that of the circular arc add line modified wrap with the same conditions, and the symmetric wrap is better than the asymmetric wrap in terms of the compression efficiency. The proposed design method is convenient to design new types of the advanced CMPs with better thermal and mechanical properties for scroll compressors.

In single screw refrigeration compressor (SSRC), the liquid refrigerant injected into the working chamber is used to reduce the exhaust gas temperature and improve the compressor performance. In this paper, a new calculation model of the injection process considering internal compression, leakage and heat transfer is presented based on the meshing principle of the meshing pair and the working mechanism of the SSRC with injection. By this model, the actual capacity and injection quality can be obtained using the calculated effective injection area. The influence of the structural parameters such as the initial position and the injection-hole diameter to the characteristics of the injection process and the thermodynamic properties of the SSRC are analyzed. Through the comparison of the injection process with different structural parameters, optimization analysis of the structural parameters can be obtained. All of this work can provide the basis for the later optimization design of the injection process.

The Multicolumn Envelope Meshing Pair (MEMP) was proposed and has been applied for the single screw refrigeration compressor (SSRC) to reduce the wear of the meshing pair. However, the geometric model shows its changed shape of the leakage paths compared with the existing straight line envelope meshing pair (LEMP). It is necessary to research the leakage characteristics of the SSRC with MEMP and LEMP, to evaluate the value of the proposed MEMP. In this paper, the geometric model of the leakage paths between star-wheel and screw rotor is established. A two-phase leakage mathematical model for gas-oil flow is presented to predict the gas leakage rate of the SSRC with MEMP. The experiments of the performance of a SSRC with MEMP were conducted to verify the leakage mathematical model. Obtained results show the leakage of the SSRC with MEMP is a little bit smaller than that of the SSRC with LEMP.

In the rotary compressor, the rolling piston and the contacted rotor-journal bearing system are main moving components. They suffer very large periodically varying loads introduced by the inertia force, the contact force and the gas force. These loads change rapidly with speed variation of the compressor. They always lead to serious vibration of the system, and then result in abrasion and performance reduction. In this paper, the dynamic behavior of the rotor-journal bearing system were calculated by solving three-dimensional numerical model using finite element method, and the vibration characteristics of the system were investigated according to the calculation results. The natural frequencies and vibration modes were obtained. The stress, displacement and axis orbit of the rotor center were calculated considering the speed variation of the motor. Via the established numerical model, vibration characteristics of a newly designed compressor can be predicted, and optimization can be done to reduce the vibration.