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Yang X.L.,Key Laboratory of Hubei Province for Water Jet Theory and New Technology | Long X.P.,Wuhan University
IOP Conference Series: Earth and Environmental Science | Year: 2012

This paper aims to figure out the influence of turbulence model and wall boundary condition on the simulation of performance and flow field of jet pumps. And then try to find out one combination of turbulence model and wall treatment method that gives out more accurate performance prediction and reasonable internal flow details. Six turbulence models, (namely the three k-epsilon, the standard and SST k-omega, and Reynolds stress models) and two wall treatment methods (standard wall functions and enhanced wall treatment) were involved. A jet pump model used in an experiment was chosen as the simulation prototype. The static pressure distribution along the wall and the performance data from the experiment were used as the reference data for validating with those from the simulation results. It is found that all the ten combinations agree well with the experiment data when the volumetric flow ratio is low, however, none of them could give a performance prediction with errors less than 10% under the lager flow ratio work conditions. The errors between predicted results by several combinations and the experiment data were lowered to be less than 5% under all the working conditions by adjusting the model constants. © Published under licence by IOP Publishing Ltd.

Long X.P.,Wuhan University | Long X.P.,Key Laboratory of Hubei Province for Water Jet Theory and New Technology | Yang X.L.,Wuhan University | Yang X.L.,Key Laboratory of Hubei Province for Water Jet Theory and New Technology
IOP Conference Series: Earth and Environmental Science | Year: 2012

This paper adopts a new method named the constant rate of pressure change (CRPC) to improve the jet pump performance. The main contribution of this method is that the diffuser generates uniform pressure gradient. The performance of the jet pump with new diffusers designed by the CRPC method, obtained by CFD methods, was compared with that of the jet pump with traditional conical diffusers. It is found that the CRPC diffuser produces a linear pressure increase indeed. The higher friction loss and the separation decrease the CRPC diffuser efficiency and then lower the pump efficiency. The pump with shorter throats has higher efficiency at small flow ratio while its efficiency is lower than the original pump at lager flow ratio and the peak efficiency of the pumps with the throat length of 5-6 Dt is higher than that of the pumps with other throat length. When the throat length is less than 4 Dt, the CRPC diffuser efficiency is higher than the conical diffuser. The CRPC method could also be used to design the nozzle and other situations needing the pressure change gradually. © 2013 Published under licence by IOP Publishing Ltd.

Long X.,Hubei Engineering University | Long X.,Key Laboratory of Hubei Province for Water Jet Theory and New Technology | Cheng H.,Beijing Institute of Technology | Yang X.,Hubei Engineering University | And 3 more authors.
Paiguan Jixie Gongcheng Xuebao/Journal of Drainage and Irrigation Machinery Engineering | Year: 2012

Two jet pumps with super-large area-ratios (57.4 and 60.05), respectively, were designed according to the conventional theory and the engineering requirements. Based on the finite volume method, the Realizable k-ε turbulence model with the standard wall function was adopted in the three dimensional flow simulations and structure optimization of the pumps. The simulation results indicated that the best efficiency point moves to a higher flow ratio and the optimum throat length increases with area ratio. Six jet pumps were manufactured according to the optimized parameters; subsequently their performance was tested under different driving pressures. There were six area ratios through the combinations of two size nozzles and three throat diameters. The experimental data show that the fluid flow inside those pumps has self-similarity like a conventional jet pump. The existing theory for predicting cavitation flow ratio overestimates the cavitation performance of those pumps, and it needs to be updated. The experimental data agreed well with the simulation results, confirming the reliability of numerical simulation and the feasibility of structure optimization. The investigation into the pumps with super area ratios has extended the application range of jet pumps.

Lyu Q.,Wuhan University | Lyu Q.,Key Laboratory of Hubei Province for Water Jet Theory and New Technology | Ranjith P.G.,Monash University | Long X.,Wuhan University | And 5 more authors.
Arabian Journal of Geosciences | Year: 2015

This paper presents an experimental study of the effects of bedding planes on the mechanical properties of shale samples. Two specimens, sourced from Sichuan Basin in China, cored perpendicular and parallel to the beddings were tested using a uniaxial compressive strength (UCS) machine, and the corresponding crack propagation patterns were analysed using acoustic emission (AE) data. In addition, a digital camera system called ARAMIS was used to acquire the lateral and axial strains during the loading. It was observed that there was significant influence on the peak strength of shale when tested for various bedding planes. As expected, the sample with perpendicular load had nearly twice as high maximum axial strength than the sample with parallel load, and the peak cumulative energy release of the parallel load on the specimen was 1.5 times higher than that of the perpendicular load. The axial strain was higher than the lateral strain in perpendicular load, while under parallel load, the lateral strain was higher than the axial strain. When the axial stress was small, for the shale sample with perpendicular load, the axial strain increased gradually with the increase of stress. In contrast, the lateral strain remained near to zero during the loading period for the sample with parallel load, and both the axial strain and lateral strain were not affected by the increasing load and remained zero. The volumetric strain of the two samples indicated that shale with a perpendicular load shows a compaction behaviour, while parallel load leads to a dilatancy characteristic. The AE data showed that the compression period consists of three stages on both of the two tests and energy release occurs mainly in the third stage. From the ARAMIS results, no perpendicular cracking was observed in the normal stress test, while under parallel loading, the cracks were mostly parallel to the load direction. © Saudi Society for Geosciences 2015.

Lyu Q.,Wuhan University | Lyu Q.,Key Laboratory of Hubei Province for Water Jet Theory and New Technology | Ranjith P.G.,Monash University | Long X.,Wuhan University | And 5 more authors.
Journal of Natural Gas Science and Engineering | Year: 2015

Due to the improvement of drilling and recovery techniques, shale gas exploration has developed rapidly over the past ten years, and problems that have arisen have attracted increasing attention. Swelling of shale with the adsorption of water is one of the leading problems for shale gas exploration, as it causes wellbore instability and shale formation collapse. The main objective of this study is to investigate the relationship of factors that influence shale swelling. On the basis of previous studies, three factors - initial water content, clay fraction and confined pressure - were selected for analysis. In order to further understand the speed of shale swelling, investigations of specimens with different initial water/moisture contents swelling in water/humid conditions are summarized. The results show that water adsorption creates higher swelling volume than moisture adsorption and the maximum swelling speed occurs at an initial water content of about 14%. To measure swelling potential, a multiple linear regression model is developed to obtain an equation to predict shale's swelling potential. According to the regression results, shale swelling is negatively linearly related to initial water content and logarithmic confined pressure, and is correlated linearly with clay fraction. © 2015 Elsevier B.V.

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