Development of a rotary pump using the rotational clap mechanism

Abstract

To avoid problems of the slider-crank mechanism, many attempts have been made to develop rotary-type machines. Nevertheless, none of them were practically successful except the Wankel engine, mainly due to poor sealing and manufacturing techniques. Furthermore, their theoretical analyses have not been advanced, and it still remains as just an idea or kinematic analysis stage. As technology has recently enough to solve the problems associated with the rotary-type machines, they have attracted attentions again. In this study, the rotational clap mechanism that was first presented by Kim was improved, detailed mechanisms to realize the mechanism was developed, and the characteristics analysis and performance prediction of the rotational clap pump were conducted based on a proto-type pump and its verification test. A working principle of the mechanism and its design parameters were introduced with kinematic analysis of the pins and rotors. The vector equations developed in the analysis can be used to easily depict the motion characteristics of the mechanism for different design parameters. The inter-relationships between the design parameters were also examined to determine the proper crank radius and pin distance within the allowable number of gear teeth and rotor size. The thickness angle of the jaw and inner radius of the rotor were found to be most significant constraints that affect the crank radius and pin distance of the mechanism. The pressure, driving torque, and efficiency characteristics of the pump were evaluated to analyze the fundamental performance of the pump. The design constraints of the fixed internal gear and gear of shaft link using involute curves were examined, and the strength of the main components was designed. The involute-type internal gear has design limits caused by three kinds of interferences. The kinematic constraints can aggravate this limits. As a result, designing a pump for high-pressure and low flow rate conditions with an involute-type internal gear can be difficult. To verify the fundamental performances of this pump, a proto-type pump was manufactured, and pump test equipment was installed. The simulated data of the flow rate, differential pressure, driving torque, and efficiencies were verified by comparison with experimental data. The main parameters that affected the pump performance were the clearance between the rotor jaws and chambers, the number of jaws, the jaw width, and the jaw height. Therefore, the parameter studies that affect the pump performance were conducted, and the performance was then predicted under these conditions. In these analysis results, the rotational clap mechanism can be realized as a pumping device on equal performance with conventional rotary pumps. In addition, It can have compact size, be good in a state of high viscosity and shear sensitive fluid, high flow rate, and works well with less vibration and power loss.