共查询到20条相似文献,搜索用时 15 毫秒
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José González Jesús Manuel Fernández Oro Katia M. Argüelles‐Díaz Carlos Santolaria 《国际流体数值方法杂志》2009,61(2):220-236
A double suction centrifugal machine has been studied, both experimentally and numerically, operating as a pump and as a turbine. Experimentally, the static performance of the machine working as a pump was obtained. These measurements were compared with equivalent numerical results from a URANS calculation. As a second step, the numerical results have been exploited to get detailed information about the flow in both operating modes (pump and turbine). The main goals of the study are, first, the validation of the numerical procedure proposed and second, the possible turbine operation of the impeller, which could point out a wider working range for the machine. The first aspect is handled by detailed analysis in the pump mode, according to previous experience of the research group. The second objective is obtained by using the numerical model to explore the flow fields obtained, when working in an inverse mode. Therefore, the presented results join the use of a numerical methodology and the turbine mode of operation for a centrifugal impeller, providing insight into the flow characteristics. When working as a pump, the flow at the suction side is characterized by the existence of an inlet tongue, which tends to enforce a uniform flow for the nominal conditions. For the turbine mode, flow patterns in the impeller, volute and suction regions are carefully investigated. The influence of the specific geometrical arrangement is also considered for this operation mode. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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Unsteady three-dimensional (3D) computational fluid dynamics (CFD) simulations are conducted with the open-source software OpenFOAM to assess the scale-adaptive k-ω-SST-SAS turbulence model (SAS) on a radial, volute-type centrifugal pump at part load operation which is characterized by high unsteadiness and flow separation. SAS results are compared to spatially high resolved and ensemble-averaged flow measurement data in terms of flow angle and turbulence intensity (TI) in the rotor–stator interaction region. Differences to simulation results obtained with the statistical state-of-the-art k-ω-SST turbulence model (SST) are highlighted. The flow angle is predicted with a reasonable agreement to measurement data by both, SST and SAS models. In the highly transient flow of strong rotor–stator interaction near the volute tongue, SST results show a significant overprediction of measured TI while the SAS model yields a considerably better agreement to measurement data even with a typical URANS grid resolution. A grid refinement does not further improve the agreement to measurement data. An in-depth analysis of the SAS model on separated flow, i.e., periodic hill test case, together with a large eddy simulation (LES) reference solution is performed and reveals that with successive grid refinement, in contrast to LES, the SAS model in its present form of Egorov and Menter (2008) does not resolve a successively larger portion of the turbulence spectrum, and the modeled part is not successively reduced. For that purpose, a re-calibration or even a re-formulation of the scale-adaption source term in the transport equation of the turbulent dissipation rate may be indispensable, which will be the subject of future studies. 相似文献
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Sai Shrinivas Sreedharan Danesh K. Tafti 《International Journal of Heat and Fluid Flow》2011,32(1):201-211
An improved physical model to predict flyash deposition is developed and discussed in this paper. This model differs from its predecessor (
[Rozati et al., in press] and [Sreedharan and Tafti, 2009] by accounting for deposition of syngas ash particles below the ash softening temperature. The modified deposition model is based on the critical viscosity approach. To test this model, deposition of ash particles impacted on a flat, 45° wedge shape geometry is computed and the results obtained from the numerical model are compared to Crosby et al. (2007). Large Eddy Simulation (LES) is used to model the flow field and flyash particles are modeled using a discrete Lagrangian framework. Results quantify deposition for 4 μm particles of various ash composition samples. Most of the deposition occurs at the stagnation region of the target plate. At 1456 K, out of all the ash samples considered in this study, WY and ND ash sample show the highest capture efficiency (15%) and KL1 ash sample exhibits the lowest capture efficiency (0.02%). In general, capture efficiencies for all ash samples followed an exponential trend with temperature. Additionally, this model is also compared to results obtained from the flat plate deposition experiments conducted here at Virginia Tech using PVC particles (Wood et al., 2010). In the case of PVC particles, the sticking probability in the deposition model assumed an exponential increase in deposition rate with temperature and was calibrated with one experimental data point. The results obtained from this model for PVC particles showed excellent agreement with the experimental measurements over a range of temperatures. 相似文献
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Maximizing efficiency is the main goal in centrifugal compressor design. Thus a computer code has been developed to optimize geometric and fluid dynamic variables with respect to several design constraints. Computations are performed with an adiabatic one-dimensional approach using state-of-the-art loss and slip correlations. The optimization takes into account mechanical stress limits. Results with different loss and slip correlations are compared with the available experimental data. Changes in optimum efficiency and specific speed due to variations of mass flow rate and pressure ratio are also presented and discussed together with the trends of the optimum geometric features. 相似文献
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Xu Liping 《Acta Mechanica Sinica》1991,7(1):39-45
An inviscid base pressure model for transonic turbine blade has been presented. It has been shown that for a given back pressure
the base pressure at the trailing edge, and the profile loss of a turbine blade are fixed according to the model and the base
pressure can be calculated with the help of an inviscid numerical scheme. A parameteric study on the model shows that a blade
profile with positive curvature downstream of the throat is advantageous for generating less loss, whilst the worst situation
is when the exit flow reaches the sonic condition. 相似文献
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基于Kriging模型的汽轮机基础动力优化设计 总被引:3,自引:0,他引:3
随着汽轮机容量的增加和核电站的迅速发展,汽轮机基础动力优化设计已经成为世界前沿的研究课题.本文提出一种基于Kriging模型的有效优化方法,用以求解上述动力优化设计问题.该问题的优化模型是在汽轮机基础框架重量约束条件下,优化汽轮机基础中柱的位置和粱、柱的截面面积,使基础振动的最大幅值最小化.Kriging模型用于建立基础振动的最大动位移幅值与设计变量间的近似函数关系,从而避免了优化迭代中灵敏度分析.开发了动力分析程序,作为黑箱用于动力响应分析.算例结果表明,本文方法在效率和稳定性上优于序列线性规划方法. 相似文献
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Two-equation turbulence models for prediction of heat transfer on a transonic turbine blade 总被引:4,自引:0,他引:4
Two versions of the two-equation k–ω model and a shear stress transport (SST) model are used in a three-dimensional, multi-block, Navier–Stokes code to compare the detailed heat transfer measurements on a transonic turbine blade. It is found that the SST model resolves the passage vortex better on the suction side of the blade, thus yielding a better comparison with the experimental data than either of the k–ω models. However, the comparison is still deficient on the suction side of the blade. Use of the SST model does require the computation of distance from a wall, which for a multi-block grid, such as in the present case, can be complicated. However, a relatively easy fix for this problem was devised. Also addressed are issues such as (1) computation of the production term in the turbulence equations for aerodynamic applications, and (2) the relation between the computational and experimental values for the turbulence length scale, and its influence on the passage vortex on the suction side of the turbine blade. 相似文献
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S. S. Katsnelson G. A. Pozdnyakov 《Journal of Applied Mechanics and Technical Physics》2013,54(5):756-761
A mathematical model of a centrifugal conductive magnetohydrodynamic (MHD) pump that calculates the distributions of velocity, current density, and pressure along the channel is developed. The viscous forces in the original system of MHD equations are taken into account on the basis of the known square law of the drag for a turbulent flow in a pipe, generalized for the case of plane flows in a channel. Dependences of the drag coefficient on the main governing parameters (metal flow rate, current intensity, and intensity of magnetic induction), which provide the agreement of the calculated and experimental data on the pressure at the pump outlet for different operation modes, are obtained. It is shown that these dependences have a universal character and the proposed model can be used to design pumps of this type and to manage their operation in production industry. 相似文献
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基于变螺旋角蜗壳型线设计方法,通过大涡模拟(LES)计算风机内部的非定常流场,利用二次回归正交试验设计法,对某离心风机的蜗壳型线进行数值优化以降低风机的A声级。优化时以蜗壳型线起始和终了位置的螺旋角为设计变量,以非定常流场计算得出的时均效率和A声级为目标函数,通过优化得到使风机气动噪声最低的最佳螺旋角分布,进而得到最佳蜗壳型线。利用数值模拟对优化结果进行了验证,验证结果表明:优化之后,时均效率降低了0.07%,A声级降低了4.04dB,时均效率和A声级相对于原风机分别降低了0.09%和4.51%;本次二次回归正交试验优化具有较高的预测精度,与CFD数值验证得出的时均效率和A声级的相对误差分别为0.01%和0.53%。 相似文献
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为预测煤尘爆炸能量,基于量纲分析理论建立煤尘爆炸能量预测模型。选取爆炸能量E、空气密度ρ和大气压强p的量纲为导出量纲。根据量纲分析Π定理得出含有待定参数λ的具有普适性的能量预测模型。通过小型煤尘爆炸性实验设计,测定10次爆炸最长火焰长度平均值l0、10次最长火焰长度出现时间平均值t0与该小型煤尘爆炸中释放能量E0,确定模型中参数λ为0.467。对模型变量t、E、l的函数关系进行合理性检验。通过实测的15组不同时刻的火焰长度进行模型变量t、l幂指关系检验。检验结果表明:量纲选取完备,预测模型科学合理。 相似文献
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Carlos Santolaria Morros Jesús Manuel Fernández Oro Katia María Argüelles Díaz 《国际流体数值方法杂志》2011,65(5):542-562
The purpose of this paper is to investigate the flow patterns in a centrifugal pump when it works as a centripetal turbine, with special interest in the unsteady behavior in order to explain the shape of the performance curves. Also, we focus on the determination of the radial thrust and other mechanical loads over a pump‐designed machine. The pump studied is commercial, with single axial suction and a vaneless spiral volute casing. A numerical study has been carried out in order to obtain more information about the flow into the volute and the impeller. A numerical three‐dimensional unsteady simulation has been developed using a commercial code that solves the URANS set of equations with a standard k–ε turbulence model. The results show the non‐axisymmetric flow developed in the volute, responsible for a significant radial thrust; the interaction between the tongue and the impeller, generating force fluctuations; the velocity and pressure distributions inside the impeller; and the exit flow, characterized with post‐rotation and low‐pressure. These flow results allow us to understand the behavior of the machine by comparing it with the pump mode. Complementarily, an experimental study was conducted to validate the numerical model and characterize the pump‐turbine performance curves at constant head. Fast‐response pressure taps and a three‐hole pneumatic pressure probe were employed to obtain a complete data set of non‐stationary and stationary measurements throughout the centrifugal machine. As a result, loss of efficiency or susceptibility to cavitation, detected numerically, was confirmed experimentally. The study demonstrates that the numerical methodology presented here has shown its reliability and possibilities to predict the unsteady flow and time‐mean characteristics of centrifugal pumps working as turbines. In particular, it is shown that the commercial design of the pump allows a reasonable use of the impeller as a turbine runner, due to the suitable adaptation of the inflow distributions to the volute casing. Moreover, the efficiency for the inverse mode is shown to be as high as achieved for the pumping operational mode. In addition, it is concluded that both axial and radial thrusts are controlled, though important unsteady fluctuations—up to 25%—clocked with the blade passing frequency appear beyond the nominal conditions. In that case, a moderate use of the pump as a turbine is recommended in order to minimize risks of fatigue failure of the bearings. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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A new transition prediction model is introduced,which couples the intermittency effect into the turbulence transport equations and takes the characteristics of fluid transition into consideration to mimic the exact process of transition.Test cases include a two-dimensional incompressible plate and a two-dimensional NACA0012 airfoil.Performance of this transition model for incompressible flows is studied,with numerical results consistent to experimental data.The requirement of grid resolution for this transition model is also studied. 相似文献
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An experimental investigation is performed to assess the characteristics of the fluid–structure interactions and microburst-induced wind loads acting on a wind turbine model sited in microburst-liked winds. The experiment study was conducted with a scaled wind turbine model placed in microburst-like winds generated by using an impinging-jet-typed microburst simulator. In addition to quantifying complex flow features of microburst-like winds, the resultant wind loads acting on the turbine model were measured by using a high-sensitive force–moment sensor as the turbine model was mounted at different radial locations and with different orientation angles with respect to the oncoming microburst-like winds. The measurement results reveal clearly that, the microburst-induced wind loads acting on the turbine model were distinctly different from those in a conventional atmospheric boundary layer (ABL) wind. With the scales of the wind turbine model and the microburst-like wind used in the present study, the dynamic wind loadings acting on the turbine model were found to be significantly higher (i.e., up to 4 times higher for the mean loads, and up to 10 times higher for the fluctuation amplitudes) than those with the same turbine model sited in ABL winds. Both the mean values and fluctuation amplitudes of the microburst-induced wind loads were found to vary significantly with the changes of the mounted site of the turbine model, the operating status (i.e., with the turbine blades stationary or freely rotating), and the orientation angle of the turbine model with respect to the oncoming microburst-like wind. The dynamic wind load measurements were correlated to the flow characteristics of the microburst-like winds to elucidate underlying physics. The findings of the present study are helpful to gain further insight into the potential damage caused by the violent microbursts to wind turbines to ensure safer and more efficient operation of the wind turbines in thunderstorm-prone areas. 相似文献