Papers by Author: Jun Zhao

Abstract: The flow in centrifugal fan and 90° bend pipe was simulated numerically by the RNG k-turbulent model in software Fluent, and obtained the distribution diagram of the pressure and velocity. From the distribution diagram of the pressure and velocity, for measurement, three measurement points must be chosen, and two of them should be closed to the wall of pipe. However, in order to insure the measure accuracy, five or six measure points should be chosen. In addition, the velocity distribution of pipe bending reaches well-distibuted at the 1000 mm away from pipe exports. That is fluid flowing after through the flow field of bending section tends to uniform soon, so for the greater curvature bend pipe, measurement is more convenient.

Abstract: With the development of the city sewage treatment, the request of the specific speed of axial flow pump has been higher and higher. At present China is lack of the system theory and method to design axial flow pump above 1400 specific speed. Selection methods of design parameters depend on experience. This paper used the improved lifting method to design axial flow pump. Optimize design of axial flow pump from cascade solidity, blade number, ratio hub and the airfoil of impeller. The feasibility of such optimize methods had been validated from theoretical analysis. Put forward new selection methods of design parameters. Design an impeller model. The rated condition of flow rate is 3000 m³/h and the rated condition of lift is 1 m. A useful reference of axial flow pump design, improvement and optimization was obtained.

Abstract: Air drilling technology has been widely used in the oil and gas exploration, coal, geothermal, geological exploration, nuclear industry and other fields due to its high drilling rate and low cost. However, the design of the pneumatic conveying system for the mineral detritus is still largely based on empiricism. The paper was set in the background of gas drilling, mainly studied the gas-solids two-phase flow characteristics in 90 degree bent annular pipe and backward-facing step of an annular pipe, which are very important parts of air drilling. They refer to the bent part and backward-facing step of an annular channel formed by the drill pipe and the borehole wall. A detailed numerical simulation and experimental studies were carried out for the flow structure and pressure losses of gas-solid two-phase in the annular pipe of gas drilling. Since a unified theory has not been developed for the two-phase flow in annular pipe, a lot of experimental work should be conducted. In the experimental research, the paper independently designed and built an annular pipe pneumatic conveying system with 90 degree bend and backward-facing step, including designing material screw feeder, material receiving hopper, pipeline, control system, data acquisition system, and etc. As known, many parameters, such as gas velocity, diameter and density of the particle, and solids loading ratio, can influence the conveying process. How these primordial influence factors act on the pressure losses of two-phase flow in annular pipe was analyzed in this paper. In the numerical simulation research, turbulent two-phase flow calculations were performed with a commercial CFD computer code referred to as FLUENT to study the gas-solid two phase flow in the sections of backward-facing step and 90 degree bent pipe respectively by using Euler-Lagrange method. The RNG κ-ε model and stochastic tracking were involved in the calculation of turbulence dispersion of two phases. The discrete phase model was performed for the solid phase. In the end, the numerical study 3-D results were translated to 1-D results using the standard averaging transformation to compare with experimental results. Predicted results obtained for pressure drop and velocity variations in full developed flows in the cases examined are in good qualitative agreement and are not in quantitative agreement with experimental data. The deviations between the simulations and experimental data lie in the range of 20%-30%. These results suggest commercial CFD codes such as FLUENT can be used productively for investigations into gas-solid two-phase flow phenomena and as an aid in pneumatic conveying design. The studies of the two-phase flow characteristics in the paper will contribute to reliable determination of the optimal condition of pneumatic conveying in gas drilling.