Time filter

Source Type

Lyu Q.,Wuhan University | Lyu Q.,Key Laboratory of Hubei Province for Water Jet Theory and New Technology | Lyu Q.,Monash University | Long X.,Wuhan University | And 4 more authors.
Energies | Year: 2016

An experimental study was performed to investigate the effect of subcritical carbon dioxide (CO2) adsorption on mechanical properties of shales with different coring directions. Uniaxial compressive strength (UCS) tests were conducted on shale samples with different CO2 adsorption time at a pressure of 7 MPa and a temperature of 40 °C. The crack propagation and the failure mechanism of shale samples were recorded by using acoustic emission (AE) sensors together with ARAMIS technology. According to the results, samples with parallel and normal bedding angles present reductions of 26.7% and 3.0% in UCS, 30.7% and 36.7% in Young's modulus after 10 days' adsorption of CO2, and 30.3% and 18.4% in UCS, 13.8% and 22.6% in Young's modulus after 20 days' adsorption of CO2. Samples with a normal bedding angle presented higher brittleness index than that with a parallel bedding angle. The strain distributions show that longer CO2 adsorption will cause higher axial strains and lateral strains. The AE results show that samples with a parallel angle have higher AE energy release than the samples with a normal angle. Finally, samples with longer CO2 adsorption times present higher cumulative AE energy release. © 2016 by the authors.


Yang X.,Wuhan University | Yang X.,Key Laboratory of Hubei Province for Water Jet Theory and New Technology | Long X.,Wuhan University | Long X.,Key Laboratory of Hubei Province for Water Jet Theory and New Technology | And 4 more authors.
Harbin Gongye Daxue Xuebao/Journal of Harbin Institute of Technology | Year: 2014

New diffuser profiles designed by constant rate of velocity or pressure change method (CRVC/CRPC) were adopted to improve the jet pump performance. The orthogonal design was used to arrange the structure combinations of jet pump. The throat length, diffuser angle and profile were chosen and each factor had three levels. Considering the interactions between factors, 27 combinations were obtained and simulated to gain their performance. The effect of structure parameters on the flow details was studied. The results from the variance analysis show that all the factors and interactions have great influence on the pump performance. The interactions among the geometric parameters should be considered during jet pump optimization. The CRVC or CRPC diffuser produces a smoother and more uniform velocity and pressure gradient along the axis than the conical diffuser. Combining with appropriate throat length, the CRVC or CRPC diffuser could improve the pump performance and shorten the total pump length considerably. The most desirable combination consists of a throat with its length 6 times of its diameter and a conical diffuser with angle of 8°.


Zeng Q.,Hubei Engineering University | Zeng Q.,Key Laboratory of Hubei Province for Water Jet Theory and New Technology | Long X.,Hubei Engineering University | Long X.,Key Laboratory of Hubei Province for Water Jet Theory and New Technology | And 4 more authors.
Paiguan Jixie Gongcheng Xuebao/Journal of Drainage and Irrigation Machinery Engineering | Year: 2014

With the method of DOE (the design of experiment method) and CFD, the optimum structure parameters combination of an annular jet pump (AJP) was mainly investigated for the maximum efficiency. The AJP model designed by previous researchers, with the area ratio 1.75, was adopted as the simulation prototype. The experimental data of the performance were used to validate the simulation results. Based on DOE, four main factors, namely the flow ratio q, the relative throat length lt, the included angles of the suction chamber α and the diffusion angle in diffuser β, were selected for the optimization of the efficiency, and series of experiments were carried out to study the inner flow of pump with different structure parameters combination. Then, the significance of structural parameters to the AJP performance was ascertained and the optimum structure parameters combination was obtained by means of statistic software package. The results confirmed the availability and effectiveness of the method that the maximum efficiency 36.3% from DOE is nearly the same with the corresponding results 35.8% from CFD. Moreover, among all the main structural parameters impacting on AJP performance, the influence of the relative throat length is considerably greater than that of the included angle of the suction chamber and the diffusion angle in diffuser. It can be concluded that the effects of two-factor interactions are more significant than that of one factor acting alone. The basis for the further optimization and determination of reasonable working range of AJP is provided.


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.


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.


Lyu Q.,Wuhan University | Lyu Q.,Key Laboratory of Hubei Province for Water Jet Theory and New Technology | Lyu Q.,Monash University | Ranjith P.G.,Monash University | And 4 more authors.
Materials | Year: 2016

The effects of CO2-water-rock interactions on the mechanical properties of shale are essential for estimating the possibility of sequestrating CO2 in shale reservoirs. In this study, uniaxial compressive strength (UCS) tests together with an acoustic emission (AE) system and SEM and EDS analysis were performed to investigate the mechanical properties and microstructural changes of black shales with different saturation times (10 days, 20 days and 30 days) in water dissoluted with gaseous/super-critical CO2. According to the experimental results, the values of UCS, Young's modulus and brittleness index decrease gradually with increasing saturation time in water with gaseous/super-critical CO2. Compared to samples without saturation, 30-day saturation causes reductions of 56.43% in UCS and 54.21% in Young's modulus for gaseous saturated samples, and 66.05% in UCS and 56.32% in Young's modulus for super-critical saturated samples, respectively. The brittleness index also decreases drastically from 84.3% for samples without saturation to 50.9% for samples saturated in water with gaseous CO2, to 47.9% for samples saturated in water with super-critical carbon dioxide (SC-CO2). SC-CO2 causes a greater reduction of shale's mechanical properties. The crack propagation results obtained from the AE system show that longer saturation time produces higher peak cumulative AE energy. SEM images show that many pores occur when shale samples are saturated in water with gaseous/super-critical CO2. The EDS results show that CO2-water-rock interactions increase the percentages of C and Fe and decrease the percentages of Al and K on the surface of saturated samples when compared to samples without saturation. © 2016 by the authors.


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.


Xiao L.Z.,Hubei Engineering University | Xiao L.Z.,Key Laboratory of Hubei Province for Water Jet Theory and New Technology | Long X.P.,Hubei Engineering University | Long X.P.,Key Laboratory of Hubei Province for Water Jet Theory and New Technology | And 6 more authors.
IOP Conference Series: Earth and Environmental Science | Year: 2014

The nozzle of annular jet pump (AJP) is annular and the secondary flow is encircled by the primary flow which is of great differences with that of central jet pump (CJP). Since the high velocity working flow soaring out the annular nozzle adheres to the inner wall, the cavitation is considerably easy to be induced at the intersection of the suction chamber and the throat. This paper mainly investigated the inception and development of the cavitation in an AJP under different flow rate ratio q by numerical methods and the results was validated by the experimentation. The turbulent model is set as Realizable k-ε model, which combined with the mixture multiphase model and the Schnerr-Sauer cavitation model. The SIMPLEC algorithm is applied to solve the coupling of pressure and velocity. The simulated results confirms well with experimental data. As the working condition varies, specifically when the pressure of the outlet decreases to a certain value, the intersection of the suction chamber and the throat sees the inception and development of the cavitation and the bubble generates there adheres to the inner wall. With the decreasing outlet pressure, the cavitation region expands to the diffuser along the inner wall, and also to the axis. When the cavitation region develops to the axis and the pressure there reaches to the critical cavitation pressure (generally vapor pressure), the pump turns into the operation limits and the efficiency drops abruptly. Furthermore, when the flow rate ratio q is considerably low (generally <0.2), the shearing layer and the center of the recirculation also experience the cavitation inception. It is for this reason that the relationship between the critical cavitation number σc and the cavitation flow rate ratio qc can be divided into two parts. When σc<0.31, it varies little with the increasing qc, while it increases linearly with the increasing qc when ranging from 0.31 to 1.58. © Published under licence by IOP Publishing Ltd.

Loading Key Laboratory of Hubei Province for Water Jet Theory and New Technology collaborators
Loading Key Laboratory of Hubei Province for Water Jet Theory and New Technology collaborators