入流速度对车用催化转换器流动特性的影响

用CFD软件FLUENT对三种不同入流速度下的催化转换器的速度场、压力场进行了三维稳态流动数值模拟,模拟结果显示:对于同一催化转换器,入口流速越大,催化转换器气流分布越不均匀,其压力损失越大。

水平井射孔参数分段组合优化模型

沿水平井筒从趾端至跟端存在压力降,且水平井射孔完井沿整个水平井筒射孔参数一般相同,导致水平井跟端过早见水,因此研究水平井射孔参数分段组合优化控制沿水平井筒入流速度剖面对水平井稳油控水尤为重要。基于水平井筒入流速度剖面控制原理,综合考虑水平井筒管流、井壁入流、地层渗流等因素的相互影响,建立了水平井射孔参数分段组合优化模型。对比分析不同射孔参数组合条件下分段优化调控入流剖面的效果,结果表明,射孔密度是调控水平井入流速度剖面最重要的参数,射孔枪弹类型、射孔相位角、射孔方位角是调控水平井入流速度剖面的次要参数,且优化参数越多,水平井入流速度剖面优化效果越好。

铝合金半固态触变充型过程的计算机模拟

分析半固态Ａ１Ｓｉ７Ｍｇ合金触变充型过程中各个阶段浆料的压力和速度变化特征，建 立耦合半固态表观粘度的三维流场数学模型，在考虑半同态边界条件和气体阻力方程基础之 上，采用ＳＯＬＡ－ＶＯＦ法对铝合金件的触变充型过程进行模拟计算．结果表明，入流速度大小 对半固态浆料充填流态有显著影响．小的入流速度浆料充填流态倾向于采用平稳充型，同时气 孔等缺陷产生倾向也小．与刹车泵体轴向注入工艺相比，在一定入流速度下，采用径向注人工 艺成形阻力较小，充型中不会出现充不满的铸造缺陷．上述模拟结果与实际相吻合．

考虑絮凝作用的辐流式二次沉淀池的三维数值模拟

为研究絮凝作用在幅流式二次沉淀池中的变化规律,本次研究采用Ghadiri模型模拟絮团的破碎机理,通过UDF自定义聚集核心相关函数,运用RNG k-ε紊流模型、Mixture混合模型以及考虑速度差、布朗运动和紊动强度的聚合模型,对考虑絮凝作用的辐流式二次沉淀池,在不同的入流速度和入流温度的工况下进行了三维数值模拟。结果表明:絮凝作用对辐流式二次沉淀池的沉淀效率影响显著,高温入流更有利于污泥絮团的生长,入流速度选取在0.02~0.05 m/s之间时更利于提高沉淀池的利用效率。

In situ experimental study on TBM excavation with high-pressure water-jet-assisted rock breaking

China’s first high-pressure hydraulically coupled rock-breaking tunnel boring machine(TBM) was designed to overcome the rock breaking problems of TBM in super-hard rock geology, where high-pressure water jet system is configured, including high-flow pump sets, high-pressure rotary joint and high-pressure water jet injection device. In order to investigate the rock breaking performance of high-pressure water-jet-assisted TBM, in situ excavation tests were carried out at the Wan’anxi Water Diversion Project in Longyan, Fujian Province, China, under different water jet pressure and rotational speed. The rock-breaking performance of TBM was analyzed including penetration, cutterhead load, advance rate and field penetration index. The test results show that the adoption of high-pressure water-jet-assisted rock breaking technology can improve the boreability of rock mass, where the TBM penetration increases by 64% under the water jet pressure of 270 MPa. In addition, with the increase of the water jet pressure, the TBM penetration increases and the field penetration index decreases. The auxiliary rock-breaking effect of high-pressure water jet decreases with the increase of cutterhead rotational speed. In the case of the in situ tunneling test parameters of this study, the advance rate is the maximum when the pressure of the high-pressure water jet is 270 MPa and the cutterhead rotational speed is 6 r/min. The technical superiority of high-pressure water-jet-assisted rock breaking technology is highlighted and it provides guidance for the excavation parameter selection of high-pressure hydraulically coupled rock-breaking TBM.

Numerical simulation investigation on pressure loss of diffusion tank of axial main fan

Based on the engineering application, the angle range of rectifying airflow unit attaching diffusion tank is from 2.5° to 7.5°. In the range of average inlet velocity of 25.0 m/s to 55.0 m/s of diffusion tank, numerical simulations of diffusion tank were done. The results of numerical simulations of diffusion tank are shown as follows： ③ In cases of the inlet velocity range from 25.0 m/s to 55.0 m/s, and the angle range of rectifying airflow unit from 2.5° to 7.5°, the average value of pressure losses decreases to the minimum when the angle is 4.5°.② In cases of the inlet velocity of 35.0 m/s, the pressure loss of diffusion tank decreases to the minimum when the angle of rectifying airflow unit is 5.5°. ③ As far as there are different angles of rectifying airflow unit, pressure loss increases gradually along with the addition of inlet velocity.

CFD simulation of an industrial hydrocyclone with Eulerian-Eulerian approach: A case study

In the present study, a three-dimensional computational fluid dynamics simulation together with experimental field measurements was applied to optimize the performance of an industrial hydrocyclone at Sarcheshmeh copper complex. In the simulation, the Eulerian–Eulerian approach was used for solid and liquid phases, the latter being water. In this approach, nine continuous phases were considered for the solid particles with different sizes and one continuous phase for water. The continuity and momentum equations with inclusion of buoyancy and drag forces were solved by the finite volume method. The k–e RNG turbulence model was used for modeling of turbulency. There was a good agreement between the simulation results and the experimental data. After validation of the model accuracy, the effect of inlet solid percentage, pulp inlet velocity, rod inserting in the middle of the hydrocyclone and apex diameter on hydrocyclone performance was investigated. The results showed that by decreasing the inlet solid percentage and increasing the pulp inlet velocity, the efficiency of hydrocyclone increased. Decreasing the apex diameter caused an increase in the hydrocyclone efficiency.

The western South China Sea currents from measurements by Argo profiling floats during October to December 2007

The three dimensional structure of the western boundary current east of the Vietnam coast was determined from measurements by Argo profiling floats which deployed near the east of the Vietnam Coast in October 2007. The trajectories of the Argo floats provided robust evidence that there does exist southward flowing current along the Vietnam coast. The southward current begins at about 15°N, 111°E, flowing along the 1 000 m isobath and extending to 5°N south. The estimated surface and parking depth velocities obtained from the floats suggest that this southward current can extend to 1 000 m depth. The mean surface velocity of the western boundary current is about 49 cm/s, with the maximum speed exceeding 100 cm/s occurring at 11.6°N, 109.5°E in the direction of 245°. The mean parking depth （1 000 m） velocity is 12-16 cm/s with the maximum speed of 36 cm/s occurring at 12.1°N, 109.7°E in the direction of 239°. The water mass analysis suggests that the Kuroshio surface water and NPIW are not apparent in the western boundary current although this time was the favored season for the Kuroshio intrusion into Luzon Strait. The mean geostrophic currents suggest that the Kuroshio intrusion into Luzon Strait during October to December 2007 is very weak, as most of the intruding water was carried eastward at 14°N near the western boundary and little flowed southward along the western boundary, providing an explanation for the absence of Kuroshio surface water and NPIW in the water mass analysis. There is a strong cyclonic circulation in the SSCS during this time, which induces a strong mixing in the western boundary companied by a homogeneous salinity layer between 300 600 m in the salinity vertical distribution. No reversal undercurrent occurred at the intermediate depth along the western boundary east of the Vietnam coast during October to December 200%

高黏石油管道球阀内油水环状流数值模拟

在油水环状流管道运输过程中,球阀启闭时流道截面变化会对油水环状流稳定性产生较大影响。利用VOF(Volume of Fluid)模型与CSF(Continuum Surface Force)模型追踪油水界面,采用标准的k-ε湍流模型,建立数值模拟控制方程,分析球阀在不同开度及不同入流速度下油水环状流的流动状态,并建立油水环状流试验平台进行验证。结果表明:数值模拟结果与试验结果一致,数值模拟能够很好地分析环状流在球阀内的流动;阀门开度对流型、油相体积分数、阀两端压力差、油相粘壁距离均产生影响,开度较小时,阀内与阀后出口管道的油水环状流遭到破坏,油相体积分数较小,阀两端压力差较大,油相容易粘附管壁;入流速度也对上述参数产生影响,较高的入流速度能够改善油水环状流的稳定性。

Aerodynamic Characteristic Research on Final Stage Stator of a Highly Loaded Fan

Due to corner separation and other complex three-dimensional flows existing in the highly loaded stator, which influences the fan performance significantly, highly loaded stator blades of a transonic fan with a maximum camber angle of 57° were studied in this paper and sector cascade experiment was adopted. In order to get the stator aerodynamic parameters as realistic as possible and conduct the experiment without the existence of rotor, an adjustable guide vane was designed to simulate the velocity magnitude and direction of the stator inlet flow. Results show that the adjustable guide vane can simulate the rotor outlet velocity direction and magnitude in most span range. The deviation angle is positive and the maximum value is nearly 21° because the severe separation is at 27% span. Corner separation exists on both pressure side and suction side and the location of separation initiation is determined. Finally, the stator blades were redesigned with some suction slots on the suction side. Experiment results show that the suction slots change the flow field structure, increase the capability of flow turning, and decrease the flow loss.

Numerical Study on the Influence Mechanism of Inlet Distortion on the Stall Margin in a Transonic Axial Rotor

A numerical study is conducted to investigate the influence of inlet flow condition on tip leakage flow (TLF) and stall margin in a transonic axial rotor.A commercial software package FLUENT,is used in the simulation.The rotor investigated in this paper is ND_TAC rotor,which is the rotor of one-stage transonic compressor in the University of Notre Dame.Three varied inlet flow conditions are simulated.The inlet boundary condition with hub distortion provides higher axial velocity for the incoming flow near tip region than that for the clean inflow,while the incoming main flow possesses lower axial velocity near the tip region at tip distortion inlet boundary condition.Among the total pressure ratio curves for the three inlet flow conditions,it is found that the hub dis-torted inlet boundary condition improves the stall margin,while the tip distorted inlet boundary condition dete-riorates compressor stability.The axial location of interface between tip leakage flow (TLF) and incoming main flow (MF) in the tip gap and the axial momentum ratio of TLF to MF are further examined.It is demonstrated that the axial momentum balance is the mechanism for interface movement.The hub distorted inflow could de-crease the axial momentum ratio,suppress the movement of the interface between TLF and MF towards blade leading edge plane and thus enhance compressor stability.

LBE simulation of impinging stream inside a T-junction mixer

Lattice Boltzmann Equation(LBE) method is utilized to simulate impinging stream(IS) in a T-junction mixer using a TD2G9 model. It aims to investigate the influence of Reynolds number(Re), aspect ratio of outlet diameter to inlet diameter, ratio of opposite inlet velocities, and the thermal boundary conditions on flow, mixing and heat transfer characteristics. In particular, the vortex evolution, velocity distribution, mixing index and Nusselt number(Nu) distribution in the T-junction mixer are explored in details. Four types of vortices and flow regimes are observed. The instantaneous and time-averaged flow and thermal fields,including vortex structure, transition of flow regimes, streamline and the Nusselt number distribution are discussed. Distinct quantitative transitions, even for dramatic change, are observed near the critical Re. At a low or moderate aspect ratio, the symmetric coherent structure is observed in an unstable flow regime. At a larger aspect ratio, the flow in the T-mixer becomes turbulent and asymmetric. The unequal injections velocities of the nozzles impose significant influence on the flow structure,mixing and heat transfer in vertical tube. Using larger difference between the two inlet velocities can result in more obvious change in flow characteristics. Moreover, mixing index is found to be valid in evaluating the mixing degree under a sinusoidal inlet velocity.