• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Design and development of guide vane cascade for a low speed number Francis turbine*

    2016-10-18 01:45:37BirajSinghTHAPAChiragTRIVEDIOleGunnarDAHLHAUG

    Biraj Singh THAPA, Chirag TRIVEDI, Ole Gunnar DAHLHAUG

    Department of Energy and Process Engineering, Norwegian University of Science and Technology, Trondheim,Norway, E-mail: biraj.s.thapa@ntnu.no

    ?

    Design and development of guide vane cascade for a low speed number Francis turbine*

    Biraj Singh THAPA, Chirag TRIVEDI, Ole Gunnar DAHLHAUG

    Department of Energy and Process Engineering, Norwegian University of Science and Technology, Trondheim,Norway, E-mail: biraj.s.thapa@ntnu.no

    Guide vane cascade of a low speed number Francis turbine is developed for the experimental investigations. The test setup is able to produce similar velocity distributions at the runner inlet as that of a reference prototype turbine. Standard analytical methods are used to design the reference turbine. Periodic walls of flow channel between guide vanes are identified as the starting profile for the boundary of the cascade. Two alternative designs with three guide vanes and two guide vanes, without runner, are studied. A new approach, for the hydraulic design and optimization of the cascade test setup layout, is proposed and investigated in details. CFD based optimization methods are used to define the final layout of the test setup. The optimum design is developed as a test setup and experimental validation is done with PIV methods. The optimized design of cascade with one guide vane between two flow channels is found to produce similar flow conditions to that in the runner inlet of a low speed number Francis turbine.

    guide vanes, Francis turbine, cascade, optimization, CFD, PIV

    Introduction

    Increase in demand of clean energy is promoting further explorations of renewable energy sources. Hydropower is one of the oldest and most reliable sources of clean energy to meet electricity demand. It contributes more than 20% of the global electricity generation. However, more than 80% of feasible hydropower resources are still untapped[1]. In recent years large scale of new hydropower plants are under construction, particularly in Asia and South America. Thus, hydropower sector will receive more attention and investments in future. It also demands research and development activities to address several technical and operational challenges brought by environmental issues and market prices[2].

    Hydraulic turbine is an important component of a hydropower plant. The turbine converts available hydraulic energy into mechanical energy, which is then converted to electrical energy by the generators. Francis type of hydraulic turbines are widely used for this energy conversion, as it can meet the real time demand with its ability to maintain high efficiency even under fluctuating load. Single unit of these turbines are capable of generating power up to 1 000 MW[3]. During the operation of Francis turbines, the guide vanes control the discharge to the runner according to power requirement. Water usually accelerates when it passes through the guide vanes and is directed to the runner at an appropriate inlet angle. In a conventional Francis turbine, about 50% of pressure head is converted to velocity head as the flow accelerates through the guide vanes[4]. For the high head Francis turbines, this accelerated flow causes unstable flow conditions contributing to vortex shedding, high amplitude pressure pulsation, flow separation and sometimes cavitation[5]. Non-uniform pressure and velocity distribution significantly affects the turbine operation and induce dynamic load on runner affecting the operating life of the turbine[6]. Operating conditions with sediment laden flows add additional challenges and escalates the problems with the eroded surfaces due to material removal[7].

    Minimizing the rotor stator interaction and achieving uniform velocity distribution at the runner inlet is one of the challenging tasks for a turbine designer. Toaddress this issue, some of the researchers have attempted to investigate and improve the flow conditions in the flow passages of the guide vanes and runner blades. Ruchonnet[8]has developed a mathematical model and studied the rotor stator interaction in a Francis pump turbine. He has studied the role of Eigen frequencies on hydraulic systems experiencing high amplitude pressure fluctuations. Larsson[9]has conducted experimental and theoretical analysis of inlet flow of a Francis turbine runner. He has used LDA methods to measure the characteristics of velocity distribution in vane less space and found that the velocity fluctuations in a guide vane passage can be up to 15% of theoretical value due to the rotor stator interaction. Qian[10]has used PIV methods to measure the pressure and velocity distribution around the pressure side and suction side of the two neighboring guide vanes in a model Francis turbine. It was found that both radial and tangential components of velocity between the guide vanes fluctuate significantly. Kobro[11]has measured the effects of such velocity fluctuations on the dynamic load in runner blades in a model Francis turbines. He found that fluctuations of stresses inside the runner blades were highest for 50-70% of nominal discharge. Xiao[12]has conducted CFD predictions of pressure pulsations in a Francis pump turbine with misaligned guide vanes. It was found that the misaligned guide vanes significantly reduce the pulse amplitudes in the stationary parts of the turbine but increases the pulse amplitudes within the rotating runner blade passages. These works show that the unsteady flow is inherent from the guide vanes and cause to several undesirable effects on turbine parts. Comprehensive study of unsteady flow around the guide vanes of Francis turbines to identify its correlation with secondary flow fields and with the design of guide vane profile would contribute to further research in this field of study.

    For a more detailed and specific investigation of flow field inside a turbine, a stationary cascade system can also produce reliable results. Cascade setup considers only a section of turbine and hence reduces flow requirements inside the test rig. Furthermore, the components in the cascade can be designed to have a better excess to measuring instruments and physical observations. Such method however, does not include the effects of runner in the flow field, and also assumes the periodic symmetry in flow over the cascade boundary. Despite of these limitations, researchers have obtained reliable and useful results using the cascade setup. Bario[13]has used a single guide vane cascade to measure the boundary layer on the pressure and suction sides of a turbine inlet guide vane. Schabowski[14]has developed a test set up with cascaded vanes to test alternative geometries to reduce tip losses in unshrouded axial gas turbines. He also used the results to verify CFD codes for such cases of flow. Zobeiri[15]has also used single guide vane cascade setup to investigate the effects of hydrofoil trailing edge shape on the wake dynamics and flow induced vibration. He identified the vortex redistribution phenomenon as the cause of vibration reduction in oblique shaped trailing edge. Finstad[16]has further investigated this vortex redistributing phenomenon behind the trailing edge of airfoils for reducing rotor stator interaction in hydraulic machineries. He has also used single guide vane cascade setup for the measurements and has tested effects of different shapes of vortex generators mounted on the rear section of suction side of guide vanes. Most of these measurements have been supported by CFD analysis for predicting the flow behavior under applicable boundary conditions. However, none of these measurements were conducted with the same magnitude of velocity and pressure as that is observed in a prototype turbine. It is challenging to develop laboratory setup which can reproduce similar pressure and velocity distribution as that observed in prototypes.

    Table 1 Reference turbine analytical design values

    Fig.1 Dimensions of prototype turbine[18]

    Fig.2 Velocities in prototype turbine[18]

    Main objective of the presented work is to develop a cascade of guide vane passages, which will be able to produce steady state flow conditions from the stay vane outlet to the runner inlet of a low speed number Francis turbine. The design goal is to acquire quite similar flow conditions as that observed in a prototype turbine. The purpose of this setup is to examine the effects of leakage flow around guide vanes on the velocity and pressure distribution at the runner inlet. The setup isolates the effects of runner on the flow field and hence allows precise study of effects of leakage flow. The paper discusses the analytical and numerical techniques applied to develop the guide vane cascade starting from the preliminary design to the final optimization and its experimental validation.

    1. Analytical design and optimization

    1.1 Reference turbine

    Jhimruk Hydroelectric Center (JHC) in Nepal is considered as the reference case for this study. The power plant has three units of Francis turbine and each produces 4.2 MW at the best efficiency point (BEP). These are low speed number splitter bladed Francis turbines defined by Eq.(1)[17].

    The power plant represents a typical case of projects operating under large sediment load in Himalayan basin[18]. Several academic studies[19-21]have been conducted to improve hydraulic design of this turbine to handle large sediment load. Design and drawings of the installed prototype are not available therefore an in-house tool named as “Khoj”, was developed to design a reference turbine with the aim to replace the existing one[20]. Extensive investigations were carried out on this reference turbine for optimizing hydraulic design to minimize sediment erosion without compromise in efficiency[22-26]. Understanding the consequences of erosion on guide vanes and investigating its effects on velocity distribution at runner inlet was identified as the further works.

    The “Khoj” has been updated to estimate velocity component at different sections of the reference turbine. These sections include center of spiral casing, inlet and outlet of stay vanes, inlet and outlet guide vanes and inlet of runner. Separate codes are developed to compute the free vortex flow lines at the required sections of flow passages, starting from the center of spiral casing to the middle of runner blade. Table 1 presents the relevant analytical values for the reference turbine at BEP. With head exceeding 200 m and speed number 0.32 these turbine can be considered as a case of high head Francis units. Figure 1 shows the major dimensions of the actual turbine. It can be observed that the main dimensions from the analytical design are similar to that of actual turbine. Figure 2 shows the flow velocities at different sections of the actual turbine. It can be observed that the highest velocity inside the turbines is at the outlet of guide vanes, which exceeds 40 m/s at part load conditions. Relative velocity at the runner outlet also reaches close to 40 m/s at the full load condition. Such high velocities causes flow instability and also severe erosion of respective components under high sediment load.

    1.2 Design of flow cascade

    A symmetric section of reference turbine forms the flow cascade. Some of the researchers have considered a straight channel with guide vane, while others have considered a section of prototype or model turbine to investigate the passage flow conditions. Choiceof channel profile depends upon objectives and requirements of the measurements. For the present study,five guide vanes (GV) with four flow passages out of 24 passages of the GV is considered as a reference case. Two outer GV form as walls of cascade and three inner GV guide flow in the channel as in the case of prototype turbine. Similar design of test setup has also been developed by the past researchers to investigate the unsteady flow in the stator part of Francis turbine[9,27]. It is expected that such configuration with multiple GV would avoid the effects of walls on the flow field around the central GV. In the present study an alternative design of test setup with a single guide vane is also done, and its performance is compared with that of the case of three GV cascade.

    Fig.3 Analytical design and section for cascade

    Fig.4 Wall profile for cascade flow

    Figure 3 shows the layout of reference turbine and the section considered for the reference (3 GV)cascade. Five GV located at the end section of spiral casing (SC) are considered for this design. The choice of GV at the end section of SC will minimize the overall size of test setup. Figure 4 shows the profile of walls within the cascade with the selected five GV. For the reference case, walls defined by the profile of free vortex flow is considered from the center of spiral casing to the inlet of guide vane, from the outlet of guide vane to the inlet of runner and from the inlet of runner to the middle of runner blade. Profile of wall upstream of center of spiral casing up to the inlet ofcascade is designed to give same distribution of tangential and radial component of velocity at the center of spiral casing from the completely axial flow at the inlet of cascade (Fig.6). Stay vanes are not included as the part of cascade, as they are mainly for strengthening spiral casing and do not play significant role for hydraulic design[28]. Circular portion of spiral casing is replaced with flat plates with the same height as that of the span of guide vane. Thus, section from inlet to outlet of cascade is embedded between twoflat plates. This makes the design relatively simple and easy for manufacturing. However, such simplification would affect the flow conditions and hence the optimization of walls' profile is necessary. Optimization techniques are applied to redesign the profile from the inlet of cascade to the center of spiral casing,and from the inlet of runner to the outlet of cascade until the satisfactory flow conditions are obtained.

    Table 2 Control parameters for design optimization

    Fig.5 Velocity components in turbine

    Fig.6 Reference design and sections for optimization

    Fig.7 Design optimization flow chart

    Table 2 lists the parameters and the target velocity, which are used to govern the optimization process. Tangential and radial components of velocity obtained from the analytical design of reference turbine are used as the control parameters. The difference in tangential component of velocity at the inlet and outlet of runner is proportionate to the hydraulic efficiency of the runner (Eq.(2)). Hence, this velocity component is identified as the most important parameter to govern the optimization process. Figure 5 shows the respective velocity components inside the turbine for the parameters listed in Table 2. Details of design techniques and calculation methods adopted for the analytical design of the complete turbine and estimation of the respective velocity components has been presented in Refs.[22,28].

    Subscript 1 and 2 represents the parameters at the inlet and the outlet of runner respectively.

    CFD analysis is conducted to validate the respective control parameters for the optimized designs. Equally spaced control points along the circumferential direction along the outlet of stay vane and along the inlet of runner are used for plotting the velocity profiles (Fig.4 and Fig.19). 3 GV cascade has 50 control points within its 60oof angular position between the flow channel walls as shown in Fig.4. Similarly, 1 GV cascade has 22 control points within its 30oof angular positions between the flow channel walls. Figure 6 shows the reference layout of 3 GV cascade and different sections identified for the design optimization process. The geometries of sections upstream of center of spiral casing (1, 2) and downstream of runner inlet (3-5), as shown in Fig.6, are optimized to get the optimum velocity distributions along the control points. Geometry of sections defined by free vortex flow (6-8)is not changed throughout the optimization process.

    The overall optimization process is summarized with the flow chart in Fig.7. Same procedure is applied for the optimization of both 3 GV and 1 GV cascade. Different cases of optimized design of cascade are developed and CFD studies of each alternative design are conducted to evaluate the properties of the control parameters along the control points. The sections upstream of center of the spiral casing (1, 2)are adjusted to control velocity components at the outlet of stay vanes. The sections downstream of the runner inlet (3-5) are adjusted to control velocity components at the inlet of runner. Particularly it is observed that among others, Section 1 and Section 3(Fig.6) are very sensitive to velocity distribution at the outlet of stay vanes and at the inlet of runner respectively. Both of these sections being a longer curvature impart higher angular momentum to flow. This would lead to change in distribution of total velocity into its components as the flow progresses inside the channel.

    Comparison of tangential velocity, obtained from the analytical design of turbine with that for alternative design of cascades, is the basis to accept or reject the alternative designs. Results of each successive optimization process are used to form hypothesis to develop the next optimized design. The final optimum design of the cascade test setup is identifed as the one,which yeilded the minimum differnece in tangential velocity component at the runner inlet position.

    Fig.8 Flow domain for 3 GV cascade

    Fig.9 Flow domain for 1 GV cascade

    2. Numerical model

    Academic version of Ansys 15.0 is used for the numerical modelling, meshing, and simulation. Primary objective of the numerical study is to evaluate the flow field inside the guide vane cascade. For the mesh validation, velocity profiles at the stay vane outlet and runner inlet sections are compared with the velocity profiles available by analytical solution. Geometry and shape of the test section are optimized with coarse mesh (nodes<3× 106). Then, more detailed validation of the optimum design of cascade is conducted with fine mesh(nodes>10× 106), and with different turbulence models. The geometry of cascade is prepared in Creo Parametric, refined with Ansys CAD model and then exported to meshing module. Figure 8 and Fig.9 and show the CAD model of the guide vane cascade created for 3 GV and 1 GV case respectively. Around the guide vanes, geometrical shape is similar to the existing turbine. To obtain uniform flow distribution, inlet section is extended by 5 times of inlet pipe diameter. Similarly, to avoid the influence of downstream boundary condition, outlet section is also extended by 5 times of outlet pipe diameter.

    Table 3 Mesh statistics for coarse mesh study

    Fig.10 Coarse mesh for 3 GV cascade

    Fig.11 Coarse mesh for 1 GV cascade

    The coarse mesh is generated with Ansys Meshing module. Created mesh density, quality, and selected flow physics, are shown in Table 3. Total 2.34×106and 1.38×106nodes are created in the computational domain of 3 GV and 1 GV, respectively. The computational domains include both hexahedral and quad elements. This combination allowed one to create relatively fine mesh around the guide vanes,where the expected flow velocity is high and boundary layer is thin. Smooth transition of 5 layers of inflation with growth rate of 1.2 is prescribed for capturing the effects of walls on the boundary layer flow. Features as “proximity and curvature”, “patch conformal”and “topology checking” are also applied. Patch conformal hybrid mesh with high grid density in the region of control points is obtained for the coarse mesh CFD studies. Quality of mesh obtained thus satisfies the necessities of the numerical simulation in Ansys CFX[29]. Mass flow inlet and pressure outlet boundary conditions are prescribed during the simulations. Total 11 simulations are performed for 3 GV cascade and 5 simulations are performed for 1 GV cascade. Figure 10 and Fig.11 show the parts of coarse mesh around the control points for 1 GV and 3 GV cascade respectively. In both cases high density mesh is generated around the guide vanes. It can also be observed that the transition of hexahedral mesh between different densities is patch conformed by creating prism and pyramids mesh elements.

    Fig.12 Fine mesh for 1 GV cascade

    Fine mesh in 1 GV cascade is created after the optimization of the cascade using coarse mesh. The cascade of fine mesh includes complete hexahedral mesh of 10×106nodes. Figure 12 shows the part of mesh generated for this study. The mesh quality is better than the quality obtained with coarse mesh. Dimensionless node position (y+)from the boundaries is varying from less than one to 300. The node position is adjusted according to the Reynolds number in the corresponding subdomains of the cascade. Since the flow is accelerating around the guide vanes, the maximum fine mesh is required around the guide vane. Similar methods of mesh generation is discussed in detailed in previous works by the authors[30].

    To investigate the flow field in detail, six turbulence models and two discretization schemes are tested. Geometry of optimized design of 1 GV cascade is used for this study and also for the grid independency tests. The turbulence models namely, RNG k-ε,standardk-ε,k-ω, SST k-ω, eddy viscosity transport, and Reynolds stress model are used. High resolution and second order advection schemes are used for the discretization. Mathematical expressions of the turbulence models and discretization schemes are extensively discussed in the literatures[31], therefore it is not discussed in this paper. Figure 13 shows tangential component of velocity at the control points of runner inlet (C u1)and stay vane outlet (CuSVo)respectively for different cases of turbulence mode. The numerical values of tangential velocity(C u), at the stay vane outlet and runner inlet sections are compared with the ideal analytical values. Ideal velocity profile assumes tangential velocity of 14 m/s and 40.8 m/s at the stay vane outlet and the runner inlet,respectively. Trend of the numerical velocity distribution is found to be similar for all turbulence models. Velocity profile at the runner inlet shows sudden drop of velocity at the guide vane trailing edge from the maximum velocity of 43 m/s. This could be attributed to the wake flow leaving the guide vane. The standard k-εmodel showed velocity drop of 3 m/s whereas the Reynolds stress model showed drop less than 1 m/s. By comparing the results of high resolution and second order discretization schemes, both schemes showed almost similar variation across the width of the cascade. Velocity distribution at the stay vane outlet is almost the same for all selected turbulence models. No major difference among the turbulence models is observed except velocity profiles near the boundary (wall). RNGk-εmodel showed lower velocity than the SST andk-ωmodels.

    Fig.13 Turbulence model tests at runner inlet

    After comparing the different turbulence models,it is found that the simulation conducted with eddy viscosity transport equation and high resolution adve-ction scheme showed quite better results, for this flow conditions. The basis of comparison is the flow field along the position of stay vanes outlet and along the position of runner inlet. Velocity profile along the runner inlet with the wake from trailing edge of the guide vane is found to be the most sensitive case to compare between different turbulence models. Some of the models have over predicted the trailing edge wake and some of them under predicted the wake effect. Eddy viscosity model showed better resolution of the flow field and wake, therefore this turbulence model is considered for further validation of the numerical model.

    Fig.14 Mesh density test at runner inlet

    To perform mesh independency tests, a hexahedral mesh with five densities is created starting from 106to 10×106nodes. Quality of the mesh is maintained uniform for all densities as stated in Table 3. Initially mesh is created with one million nodes, then 2×106by increasing the scale factor of 2 and so on for successive mesh densities. Figure 14 shows the velocity profiles at the runner inlet position for different cased of mesh densities. All the gird density, except for the case of 106nodes, predicts the similar velocity profile. It is evident that 106node density is not sufficient enough to capture the wake phenomenon. Velocity profile at the stay vane outlet is almost same for all densities of the mesh indicating that there is minimum effect of spatial discretization on the upstream flow field. It is concluded that mesh with 2×106node is found suitable for this study.

    3. Results and discussions

    Result of numerical simulations of the flow inside the alternative designs of cascade at the control points defined in Fig.4, is compared with that of the analytical values. For cross verification of final design, the numerical results from current study are compared with that from other experimental and CFD studies of similar nature. Results from the experimental study of the flow inside the optimum design of cascade is also presented as the validation of this study.

    Fig.15 Runner inlet velocities for 3 GV reference design

    Fig.16 Stay vane outlet velocities for 3 GV reference design

    3.1 Optimization for 3 GV cascade

    The numerical study of the alternative designs of 3 GV cascade is done with the coarse mesh as discussed in Section 2. Only the results for the reference and the final optimized designs are discussed in this paper. Most of the results for intermediate designs fall in-between that of reference and optimized design. Figure 15 shows the velocity distributions along the inlet of runner for reference design of 3GV cascade. It can be observed that total velocity(C1)is lower than the analytical value towards the inner wall from the mid span of flow channel and higher than the analytical value towards outer wall from the mid span of flow. It can also be noticed that tangential component of velocity (C u1)is major contributor to this skewed velocity distribution. Figure 16 shows the velocity distributions along the outlet of stay vane. Similar pattern of skewed velocity distribution along the inlet of runner can also be observed at the outlet of stay vanes. Simplification in design of spiral casing and the channel downstream of runner inlet are the probable causes for this deviation. It is hypothesized that increasing the curvature of inner walls and reducing the same for outer walls can counter effect this skewed velocity distribution. Different curvatures for the walls and their combinations are introduced for changing the geometry of the inner and outer walls to come up with the final optimized design.

    Fig.17 Runner inlet velocities for 3 GV optimized design

    Fig.18 Stay vane outlet velocities for 3 GV optimized design

    Figure 17 and Fig.18 show the velocity distributions along the inlet of runner and along the outlet of stay vanes respectively for the optimized design. It can be observed that skewed velocity distribution for both runner inlet and stay vane outlet position is normalized. The velocity components for the runner inlet position are lower than the analytical values and that are higher than the analytical values for stay vane outlet position. It is likely that viscous effects and frictional losses in the walls might have caused lower velocities at runner inlet compared to that of analytical values, which is for the ideal flow conditions. Alteration of geometries at the inlet section of cascade for desired velocity profile at the position of runner inlet,have effected flow area and hence the velocities at the stay vane outlet. Variation in the velocity at the control points 16, 28, and 41 correspond to the effect of guide vanes' leading and trailing edge. Velocity and pressure contours have shown large pressure gradient on the leading and trailing edge.

    Figure 19 shows the contours for the velocity distribution along the section of reference design of 3 GV cascade. Regions of velocity higher than 45 m/s covers area downstream of runner inlet and the velocity upstream of stay vane outlet is below 20 m/s. Such velocity distribution requires high accelerated flow and hence demands the consecutive pressure distribution as shown in Fig.20. It is observed that pressure in the region upstream of stay vane is greater than 10 Pa, which is the limiting capacity of the laboratory. The pressure in the region downstream of runner inlet is lower than the atmospheric pressure,which induces the chances of cavitation in the region where the measurements are to be taken. These results further justify the need of design optimization of the cascade.

    Fig.19 Velocity profile for reference 3 GV design

    Fig.20 Pressure profile for reference 3 GV design

    Fig.21 Velocity profile for optimized 3 GV design

    Figure 21 and Fig.22 show the contours for the velocity distribution and the contours of pressure distribution along the section of optimized design of 3 GV cascade respectively. It can be observed that both velocity and pressure distributions have improved significantly. It satisfies the laboratory constraints while avoiding the cavitation in the regions wheremeasurements have to be conducted. Flow field around the middle guide vane may be considered as actual flow field in the turbine because flow around this guide vane is not largely affected by the boundaries.

    Fig.22 Pressure profile for optimized 3 GV design

    Fig.23 Velocity profile for optimum design of 1 GV cascade

    Fig.24 Pressure profile for optimum design of 1 GV cascade

    3.2 Optimum design of 1 GV cascade

    Similar design methods as for 3 GV cascade are used to develop the reference design of 1 GV cascade. Similar methods as for 3 GV are also used to optimize its geometry for desired velocity distributions along the control points. Coarse mesh is used to analyze alternative design options. The final optimized design is analyzed by fine mesh for cross verifications of the results. Only the results of final (optimum) design for 1 GV cascade is discussed in this paper. Figure 23 and Fig.24 show the velocity and pressure fields of the final design of 1 GV cascade. It can be seen that both velocity and pressure distribution has the matching pro-file with the theoretical distributions. Figure 25 compares tangential velocity(C u)distribution for the optimum design of 1 GV cascade obtained by both coarse and fine mesh with that of analytical values. It can be observed that both coarse mesh and fine mesh study show that velocity distribution along the control points are close to that of analytical values. As expected, fine mesh study predicts boundary wall effects and wake flow more precisely than that of coarse mesh. Accuracy in such effects as wakes and boundary layer flow etc. may not be necessary for the study of the effects of change in cascade geometry on the velocity distribution. This study shows that the results from coarse mesh study can be accepted for the analysis of design optimization of test setup as intended for this study.

    Fig.25 Velocity components for 1 GV optimum design from different methods

    Difference between the original design of cascade(3 GV setup) without any optimization, and the optimum design of cascade (1 GV setup) can be made by comparing Fig.15 and Fig.25. It can be observed in Fig.15 that the original 3 GV design has higher difference in tangential component of velocity between the adjacent guide vanes at runner inlet. However, optimum 1 GV design (Fig.25) gives the almost constant tangential component of velocity at runner inlet from the adjacent guide vanes.

    This analysis supports the argument that 1 GV cascade is able to produce the velocity profile at the position of inlet of runner comparable to that of an actual Francis turbine, excluding the rotor-stator interaction. However, with 1 GV cascade the correct flow conditions can be achieved only for a single operating point. Thus, all the measurements have to be done only at one operating point. For this study, best efficiency point (BEP) is considered for the design of cascade and for the consequent measurements.

    3.3 Experimental validation

    Development of the experimental test setup isbased on the layout of optimum design of 1 GV cascade. The main aim of the test setup is to measure the change in velocity and pressure distribution at the inlet of runner due to increasing leakage flow around guide vane. PIV methods is applied for capturing velocity field, from the position of stay vane outlet to the position of runner inlet. For the convenience of manufacturing, assembly and testing, the setup is divided into several parts as shown in Fig.26. The test section contains the test guide vane inside a plexiglass flow channel. The cover plates of test section have openings for excess to the laser sheet and camera exposure for PIV images as shown in Fig.27.

    Fig.26 Cross section view of 1 GV test setup

    Fig.27 Exploded view of the test section

    Fig.28 Test section and measurement points for PIV

    Fig.29 Comparison between PIV and CFD results

    Experimental validation of the test setup is conducted at the facilities of the Waterpower laboratory in NTNU. The test setup is mounted in a closed loop system consisting of pump, flow meter, and a pressure tank. The reference test condition for this measurement is the total velocity(C)at the runner inlet being 12.45 m/s. Flow rate of 58.2 liter per second is necessary to build this velocity. Results from the PIV measurement of velocity distribution at position of outlet of guide vanes and at the inlet of runner is compared to that from the fine mesh CFD results for the same operating conditions. The PIV measurements is performed with a Dantec system. The pulsed light sheet with a thickness of 0.002 m, is generated by two double-cavity Nd-YAG lasers providing 120 mJ by pulse. The lighted field is visualized by a HiSense 2M CCD PIV cameras, with a series of paired images acquired at 150 μs and 4 Hz. Alignment of laser and camera with respect to the measurement plane is achieved with separate laser pointers. Fluorescent seeding particles, with a density of 1.016 kg/m3, refractive index of 1.52 and mean diameter of 55 μm are used during the measurements. The camera resolution is 1 280×1 024 pixels for a 0.35 m×0.40 m spatial domain. The camera exposition and its synchronization with laser and the image processing is done with a Dantec DynamicStudio 3.40 PIV specific processor. The image processing is carried out with 32-pixel resolution cross-correlation technique with 50% overlap. Figure 28 shows the field of view of the test section and circular position of turbine components. Velocity vectors are obtained along the mid span of the test setup from the PIV measurements, with the time-averaged value for 100 image pairs. Figure 29 shows the comparison between results from PIV measurements with that of CFD simulations for similar flow conditions. Tangential velocity distribution along the circular section of guide vane outlet and runner inlet, as shown in Fig.28, is used as basis for this comparison. It can be observed that CFD results at GV outlet position is very close to that of PIV results. However, as expected, CFD over predicts the wake with respect to PIV measurements. At the runner inletposition as well, CFD results is close to that of PIV measurements. Effects of wall due to 1 GV cascade,and also measurements being conducted at lower velocities, could be the reasons for the velocity form PIV measurements, at the runner inlet, being less uniform with respect to the analytical velocity profile as shown in Fig.29. With these PIV results, it can be inferred that 1 GV test setup can produce the velocity conditions comparable with the prototype turbine.

    3.4 Comparison with similar studies

    There are some past studies for the flow analysis with the use of cascade guide vane setup. Comparison with the methods adopted for the design of such setup could not be done as the available literatures does not discuss the design methods in detail. Most of studies are focused on the measurements of wake behind the guide vane and on the prediction of rotor-stator interaction. Antonsen[32]has conducted measurements of wake flow in a 5 GV cascade setup for a high head Francis turbine. He has also compared the results with the CFD study. Figure 30 shows comparison of LDA measurements and CFD studies of wake behind the guide vane of a Francis turbine from his study. The measurements were done along the direction normal to the wake and not along the runner inlet as for this study. The profile of wake from his study can be compared with that estimated by CFD simulations for optimized design of 1 GV cascade. The constant velocity contours in zoomed section (Fig.23) show the formation and dissipation of wake behind the guide vanes that also matches to the results from Antonsen(Fig.30).

    Fig.30 LDV and CFD study of wake behind guide vane[32]

    Larsson[9]has conducted the measurement of velocity components along the circular section in the vane less gap between the outlet of guide vanes and the inlet of runner. He has also compared the experimental results with different numerical simulations. Figure 31 shows the distribution of tangential velocity along the vane less gap for one guide vane pitch in circumferential direction. He has verified this result with the actual measurements of velocity in vane less space in a model turbine. His CFD simulations, both with coarse mesh and fine mesh, were not able to predict the wake flow accurately. It can be observed that the profile of tangential velocity at GV outlet measured by Larsson is similar to that predicted for 1 GV cascade with the PIV measurements and CFD study shown in Fig.29. Simulations with the coarse mesh for pressure distribution in the vane less space done by Larsson is presented in Fig.32. Profile of pressure distribution obtained from his result is comparable with that for the optimum design of 1 GV cascade for this study, as presented in Fig.24. Due to difference in pressure along the pressure side and suction side of GV, runner experiences marginal increase in pressure as it passes from suction side of one GV to the point of wake interactions, and again experiences marginal reduction in pressure as it reaches to the suction side of adjacent GV. This pressure fluctuation also has its effects on velocity profile along the inlet of runner from the suction side of one GV to another. Hence,runner passes through the contours of different velocity magnitudes as it crosses one GV to another. This phenomenon can be observed in Fig.23, Fig.13 and Fig.14. Thus it can be accepted that the velocity profiles created by 1 GV cascade at the runner inlet is much closer to the prototype Francis turbine operating at BEP.

    Fig.31 LDA and CFD measurements of velocity component behind GV[9]

    Fig.32 CFD study of pressure distribution behind GV[9]

    4. Conclusions

    This paper suggests an approach to design a cascade setup for investigating the flow in stator part of low speed number Francis turbines. Several researchers have conducted theoretical, numerical and experimental studies to investigate flow phenomenon inside Francis turbine with different objectives. Stationary cascade with single or multiple guide vanes is often used to study flow in the stator part of Francis turbine. Details of design methods adopted for development of such test setups are not found to be published in available literatures. It is also perceived that none of the measurements in laboratory setup has been done for the prototype operating conditions.

    This paper discussed the details of the methods used to design and optimize a cascade test setup for studying the effects of leakage flow between guide vanes and its walls in a low specific speed Francis turbine. Analytical methods are used to design a complete reference turbine. Flow cascade with three guide vanes and one guide vane at the end section of spiral casing are selected as alternative design options. Computed velocity profiles through analytical method are compared with the CFD results to identify the best design option. The design optimization is carried out using coarse mesh and total 11 and 5 simulations are conducted for 3 GV and 1 GV cascade respectively. Furthermore, to investigate effects of spatial discretization and turbulence models, detailed mesh independency study are also conducted. It is found that the mesh with 2×106nodes and eddy viscosity transport equation and high resolution discretization scheme provide good results. Final simulation of the optimum design of test setup is conducted using the verified numerical model. The optimum design is fabricated and experimental validation of flow conditions with respect to CFD and analytical calculations are made.

    With this study it is concluded that optimized design of both 3 GV and 1 GV cascade can create the similar flow conditions at the position of inlet of runner as that in the case of actual turbine. Due to manufacturing and testing easiness, 1 GV cascade is selected for the development of test setup. Results of measurements from this setup can be compared directly to the case of prototype turbine at BEP conditions. It is also concluded that, for flow analysis and design optimization of problems, CFD studies with relatively coarse mesh can give reliable results.

    Acknowledgments

    Authors would like to thank Mr. Frode Kj?snes for his supports in CFD study with fine mesh, and Ms. Linda Haugvaldstad for her support in stress analysis in the test section of the setup.

    References

    [1] DARMAWI, SIPAHUTAR R. and BERNAS S. M. et al. Renewable energy and hydropower utilization tendency worldwide[J]. Renewable and Sustainable Energy Reviews, 2013, 17: 213-215.

    [2] STERNBERG R. Hydropower's future, the environment,and global electricity systems[J]. Renewable and Sustainable Energy Reviews, 2010, 14(2): 713-723.

    [3] FLORES E., BORNARD L. and TOMAS L. et al. Design of large Francis turbine using optimal methods[J]. IOP Conference Series: Earth and Environmental Science,2012, 15(2): 022023.

    [4] BREKKE H. Hydraulic design strategy for Francis turbines[J]. International Journal on Hydropower and Dams,1996, 3(3): 38-42.

    [5] XIAO Y., WANG Z. and YAN Z. et al. Experimental and numerical analysis of pressure pulses characteristics in a Francis turbine with partial load[J]. IOP Conference Series: Earth and Environmental Science, 2010, 12(1): 012023.

    [6] MAGNOLI M. V., SCHILLING R. Numerical simulation of pressure pulsationsin Francis turbines(GOURBESVILLE P., CUNGE J. and CAIGNAERT G. Advances in hydroihformations)[M]. Singapore: Springer, 2014, 389-403.

    [7] THAPA B. S., DAHLHAUG O. G. and THAPA B. Sediment erosion in hydro turbines and its effect on the flow around guide vanes of Francis turbine[J]. Renewable and Sustainable Energy Reviews, 2015, 49: 1100-1113,

    [8] RUCHONNET N., NICOLET C. and AVELLAN F. Onedimensional modeling of rotor stator interaction in Francis pump-turbine[C]. Proceedings of the 23rd IAHR Symposium on Hydraulic Machinery and Systems. Yokohama, Japan, 2006.

    [9] LARSSON C. Experimental and theoretical analysis of inlet flow of a Francis turbine runner[D]. Doctoral Thesis, Trondheim, Norway: Norwegian University of Science and Technology, 2003.

    [10] QIAN R. Flow field measurements in a stator of a hydraulic turbine[D]. Doctoral Thesis, Quebec, Canada: Laval University, 2008.

    [11] KOBRO E. GAMBOA A. and BLOCH R. et al. Onboard pressure measurement in high head Francis prototype runners[C]. 3rd IAHR International Meeting of the Work Group on Cavitation and Dynamic Problems in Hydraulic Machinery and Systems. Brno, Czech Republic, 2009, 14-16.

    [12] XIAO Ye-xiang, WANG Zhong-wei and ZHANG Jin et al. Numerical predictions of pressure pulses in a Francis pump turbine with misaligned guide vanes[J]. Journal of Hydrodynamics, 2014, 26(2): 250-256.

    [13] BARIO F., BERAL C. Boundary layer measurements on the pressure and suction sides of a turbine inlet guide vane[J]. Experimental Thermal and Fluid Science, 1998,17(1-2): 1-9.

    [14] SCHABOWSKI Z., HODSON H. The Reduction of over tip leakage loss in unshrouded axial turbines using winglets and squealers[J]. Journal of Turbomachinery, 2007,136(4): 663-675.

    [15] ZOBEIRI A., AUSONI P. and AVELLAN F. et al. How oblique trailing edge of a hydrofoil reduces the vortexinduced vibration[J]. Journal of Fluids and Structures,2012, 32(3): 78-89.

    [16] FINSTAD P. H. E., KJELDSEN M. and ARNDT R. E. Characterizing Rotor-Stator interaction-RSI in hydrofoil wake using CFD and experimentally obtained wake flow fields[C]. 14th International Symposium on Transport Phenomena and Dynamics of Rotating. Trondheim,Norway, 2012.

    [17] BREKKE H. Hydraulic turbines: Design, erection and operation[M]. Trondheim, Norway: Norwegian University of Science and Technology (NTNU) publications,2001.

    [18] PRADHAN P. M. S., DAHLHAUG O. G. and JOSHI P. N. et al. Sediment and efficiency measurements at Jhimruk Hydropower Plant-Monsoon 2003[R]. Report from Hydro Lab, Nepal, 2004.

    [19] GJOSATER K. Hydraulic design of Francis turbine exposed to sediment erosion[D]. Master Thesis,Trondheim, Norway: Norwegian University of Science and Technology, 2011.

    [20] THAPA B. S. Hydraulic design of Francis turbine to minimize sediment erosion[D]. Master Thesis, Dhulikhel,Nepal: Kathmandu University, 2012.

    [21] ELTVIK M. Sediment erosion in Francis turbines[D]. Doctoral Thesis, Trondheim, Norway: Norwegian University of Science and Technology, 2013.

    [22] THAPA B. S., ELTVIK M. and GJ?S?TER K. et al. Design optimization of Francis runners for sediment handling[C]. Fourth International Conference on Water Resources and Renewable Energy Development in Asia. Chiang Mai, Thailand, 2012.

    [23] THAPA B. S., GJOSATER K. and ELTVIK M. et al. Effects of turbine design parameters on sediment erosion of Francis runner[C]. 2nd International Conference on Developments in Renewable Energy Technology. Dhaka,Bangladesh, 2012, 167-171.

    [24] THAPA B. S., THAPA B. and ELTVIK M. et al. Optimizing runner blade profile of Francis turbine to minimize sediment erosion[J]. IOP Conference Series: Earth and Environmental Science, 2012, 15(3): 032052.

    [25] CHITRAKAR S., CERVANTES M. and THAPA B. S. Fully coupled FSI analysis of Francis turbines exposed to sediment erosion[J]. International Journal of Fluid Machinery and Systems, 2014, 7(3): 101-109.

    [26] RAJKARNIKAR B., NEOPANE H. P. and THAPA B. S. Development of rotating disc apparatus for test of sediment-induced erosion in francis runner blades[J]. Wear,2013, 306(1-2): 119-125.

    [27] CHEN X. Theoretical and experimental study of flow through the double cascade of a Francis turbine[D]. Doctoral Thesis, Trondheim, Norway: Norwegian University of Science and Technology, 1992.

    [28] WEI Z., FINSTAD P. H. and OLIMSTAD G. E. et al. High pressure hydraulic machinery[R]. Trondheim,Norway: Norwegian Institute of Science and Technology,2009.

    [29] ANSYS, Ansys 16.0 release documentation. Theory and modelling guide[M]. Canonsburg, PA, USA: ANSYS Inc.,Southpointe, 2600 ANSYS Drive, 2015.

    [30] TRIVEDI C., CERVANTES M. J. and DAHLHAUG O. G. et al. Experimental investigation of a high head Francis turbine during spin-no-load operation[J]. Journal of Fluids Engineering, 2015, 137(6): 061106.

    [31] FERZIGER J. H., PERI? M. Computational methods for fluid dynamics[M]. Berlin, Germany: Springer, 2002.

    [32] ANTONSEN ?. Unsteady flow in wicket gate and runner with focus on static and dynamic load on runner[D]. Doctoral Thesis, Trondheim, Norway: Norwegian University of Science and Technology, 2007.

    10.1016/S1001-6058(16)60648-0

    June 22, 2015, Revised November 27, 2015)

    * Biography: Biraj Singh THAPA (1979-), Male,Ph. D. Candidate

    2016,28(4):676-689

    婷婷丁香在线五月| 久久午夜亚洲精品久久| 日本 av在线| 久久青草综合色| 中文字幕人妻丝袜一区二区| 在线观看免费视频日本深夜| 一级片'在线观看视频| 精品福利永久在线观看| 黄色女人牲交| 老汉色∧v一级毛片| 看黄色毛片网站| 别揉我奶头~嗯~啊~动态视频| 99精国产麻豆久久婷婷| 日韩三级视频一区二区三区| 91字幕亚洲| 亚洲精品国产一区二区精华液| 男女下面插进去视频免费观看| 男女做爰动态图高潮gif福利片 | 亚洲av第一区精品v没综合| 99热只有精品国产| 亚洲三区欧美一区| 中文字幕高清在线视频| 国产日韩一区二区三区精品不卡| √禁漫天堂资源中文www| 亚洲精华国产精华精| 国产精品久久久人人做人人爽| 一区二区三区激情视频| 国产伦人伦偷精品视频| 欧美亚洲日本最大视频资源| 日日夜夜操网爽| 夜夜夜夜夜久久久久| 色精品久久人妻99蜜桃| 女性生殖器流出的白浆| 99久久久亚洲精品蜜臀av| 97人妻天天添夜夜摸| 桃红色精品国产亚洲av| 在线免费观看的www视频| 精品电影一区二区在线| 性少妇av在线| 69av精品久久久久久| 80岁老熟妇乱子伦牲交| 一级a爱片免费观看的视频| 欧美日韩瑟瑟在线播放| 久久伊人香网站| 在线观看免费午夜福利视频| 久久中文字幕人妻熟女| 国产欧美日韩一区二区三| 国产欧美日韩一区二区三区在线| 99国产精品一区二区三区| 国产aⅴ精品一区二区三区波| 在线观看日韩欧美| 国产精品久久久久久人妻精品电影| 美女高潮喷水抽搐中文字幕| 亚洲伊人色综图| 国产亚洲av高清不卡| 麻豆一二三区av精品| 久久久久精品国产欧美久久久| 99riav亚洲国产免费| 亚洲国产精品一区二区三区在线| 美女高潮到喷水免费观看| 免费少妇av软件| 在线观看www视频免费| 国产乱人伦免费视频| 午夜久久久在线观看| a级毛片在线看网站| www.999成人在线观看| 丁香欧美五月| 久久婷婷成人综合色麻豆| 咕卡用的链子| 搡老乐熟女国产| 十分钟在线观看高清视频www| 久久九九热精品免费| 久久精品成人免费网站| 欧美日韩乱码在线| 国内毛片毛片毛片毛片毛片| 在线观看一区二区三区| 黑人巨大精品欧美一区二区蜜桃| 757午夜福利合集在线观看| 丁香六月欧美| 91老司机精品| 女人精品久久久久毛片| 在线观看午夜福利视频| 日韩视频一区二区在线观看| 亚洲久久久国产精品| 欧美激情 高清一区二区三区| 午夜影院日韩av| av天堂在线播放| 波多野结衣高清无吗| 老熟妇仑乱视频hdxx| 欧美不卡视频在线免费观看 | 性少妇av在线| 一级,二级,三级黄色视频| 欧美激情 高清一区二区三区| 在线观看一区二区三区| 久久久久亚洲av毛片大全| 不卡一级毛片| 免费在线观看影片大全网站| 亚洲五月色婷婷综合| xxxhd国产人妻xxx| 欧美另类亚洲清纯唯美| 一进一出抽搐动态| av超薄肉色丝袜交足视频| 亚洲九九香蕉| 国产黄a三级三级三级人| 日韩精品青青久久久久久| 精品福利观看| 岛国在线观看网站| 亚洲va日本ⅴa欧美va伊人久久| 香蕉久久夜色| 操美女的视频在线观看| 制服诱惑二区| 久9热在线精品视频| 国产有黄有色有爽视频| 欧美激情极品国产一区二区三区| 99在线视频只有这里精品首页| av网站免费在线观看视频| 中文字幕另类日韩欧美亚洲嫩草| 欧美日韩中文字幕国产精品一区二区三区 | 精品一区二区三区视频在线观看免费 | 黄色丝袜av网址大全| 欧美乱妇无乱码| 69av精品久久久久久| 久久中文字幕人妻熟女| 久久久久久大精品| 亚洲熟妇熟女久久| 激情视频va一区二区三区| 啦啦啦 在线观看视频| 亚洲第一av免费看| 午夜免费成人在线视频| 黄色成人免费大全| 成年版毛片免费区| 久久精品亚洲精品国产色婷小说| 伦理电影免费视频| 日本 av在线| 国产亚洲欧美在线一区二区| 国产精品香港三级国产av潘金莲| 亚洲专区中文字幕在线| 国产真人三级小视频在线观看| 国产精品久久久av美女十八| 在线观看免费视频网站a站| 国产精品久久久人人做人人爽| 一级,二级,三级黄色视频| 久久精品国产亚洲av香蕉五月| 热re99久久精品国产66热6| 午夜两性在线视频| 日本黄色视频三级网站网址| 久久久久久免费高清国产稀缺| 三上悠亚av全集在线观看| 日韩中文字幕欧美一区二区| 欧美不卡视频在线免费观看 | 亚洲一区高清亚洲精品| 亚洲一卡2卡3卡4卡5卡精品中文| 男人操女人黄网站| x7x7x7水蜜桃| 国产区一区二久久| 老司机午夜福利在线观看视频| 成熟少妇高潮喷水视频| 亚洲一码二码三码区别大吗| 嫩草影视91久久| 亚洲美女黄片视频| 精品一品国产午夜福利视频| 久久天躁狠狠躁夜夜2o2o| 中文字幕另类日韩欧美亚洲嫩草| 电影成人av| 男人操女人黄网站| 精品午夜福利视频在线观看一区| 99在线视频只有这里精品首页| 久久精品亚洲av国产电影网| 日韩高清综合在线| 一边摸一边抽搐一进一小说| 亚洲人成77777在线视频| 国产在线观看jvid| 久久人人精品亚洲av| 午夜激情av网站| 一级毛片高清免费大全| 99久久国产精品久久久| 欧美人与性动交α欧美精品济南到| 男人的好看免费观看在线视频 | 欧美日韩亚洲综合一区二区三区_| 色在线成人网| 啦啦啦免费观看视频1| 久久精品国产清高在天天线| 黄色女人牲交| 男女做爰动态图高潮gif福利片 | 免费一级毛片在线播放高清视频 | 黑人猛操日本美女一级片| 熟女少妇亚洲综合色aaa.| 婷婷丁香在线五月| 黑人猛操日本美女一级片| 国产成人欧美在线观看| 天堂影院成人在线观看| 中文字幕高清在线视频| 亚洲人成网站在线播放欧美日韩| 亚洲 欧美 日韩 在线 免费| 亚洲伊人色综图| 少妇被粗大的猛进出69影院| 国产精品九九99| 88av欧美| 人人妻人人爽人人添夜夜欢视频| 男女床上黄色一级片免费看| 国产成年人精品一区二区 | 精品欧美一区二区三区在线| www.熟女人妻精品国产| 欧美最黄视频在线播放免费 | 亚洲七黄色美女视频| 99国产综合亚洲精品| 亚洲欧美一区二区三区黑人| 久久久国产成人免费| 欧洲精品卡2卡3卡4卡5卡区| 午夜日韩欧美国产| 国产乱人伦免费视频| 又黄又粗又硬又大视频| 亚洲国产精品合色在线| 热re99久久精品国产66热6| 国产精品一区二区精品视频观看| 身体一侧抽搐| 欧美黑人精品巨大| 午夜福利一区二区在线看| 老汉色av国产亚洲站长工具| 久久久久久久午夜电影 | 欧美中文综合在线视频| 丁香六月欧美| 国产亚洲精品综合一区在线观看 | 级片在线观看| av国产精品久久久久影院| 中文字幕精品免费在线观看视频| av国产精品久久久久影院| 高清欧美精品videossex| 精品一区二区三区视频在线观看免费 | 欧美最黄视频在线播放免费 | 水蜜桃什么品种好| 动漫黄色视频在线观看| 欧美日韩亚洲高清精品| 神马国产精品三级电影在线观看 | 麻豆久久精品国产亚洲av | 香蕉国产在线看| 国产欧美日韩综合在线一区二区| 夜夜夜夜夜久久久久| 国产精品久久电影中文字幕| 亚洲在线自拍视频| 成人精品一区二区免费| 中文字幕精品免费在线观看视频| 欧美日韩精品网址| 动漫黄色视频在线观看| 久久伊人香网站| 欧美中文日本在线观看视频| 在线播放国产精品三级| 国产成人av教育| 一级作爱视频免费观看| videosex国产| 人成视频在线观看免费观看| 久久性视频一级片| 人妻久久中文字幕网| 亚洲午夜理论影院| 亚洲精品av麻豆狂野| 在线国产一区二区在线| 久热爱精品视频在线9| 女人被躁到高潮嗷嗷叫费观| 天天躁狠狠躁夜夜躁狠狠躁| 国产精品二区激情视频| 精品国产乱码久久久久久男人| 国产成人影院久久av| 亚洲人成伊人成综合网2020| 久久人人爽av亚洲精品天堂| 亚洲午夜理论影院| 日本黄色视频三级网站网址| 男人舔女人下体高潮全视频| 国产精品爽爽va在线观看网站 | 人成视频在线观看免费观看| 高清毛片免费观看视频网站 | 日本vs欧美在线观看视频| av片东京热男人的天堂| 桃色一区二区三区在线观看| 久久人妻av系列| 亚洲 欧美一区二区三区| 精品福利观看| 91成人精品电影| 欧美在线黄色| av有码第一页| 久久性视频一级片| 国产成人欧美在线观看| 久久久久久久久免费视频了| 久久精品亚洲熟妇少妇任你| 自线自在国产av| 亚洲成av片中文字幕在线观看| cao死你这个sao货| 亚洲精华国产精华精| 久久久国产成人免费| 制服人妻中文乱码| 免费在线观看视频国产中文字幕亚洲| 久久国产精品影院| 亚洲成人免费av在线播放| 琪琪午夜伦伦电影理论片6080| 69av精品久久久久久| e午夜精品久久久久久久| 高潮久久久久久久久久久不卡| 欧美日韩av久久| 成人三级黄色视频| 香蕉丝袜av| 午夜免费激情av| 桃色一区二区三区在线观看| 国产精品一区二区免费欧美| 国产伦一二天堂av在线观看| 亚洲中文字幕日韩| 国产xxxxx性猛交| 久久香蕉国产精品| 中国美女看黄片| 黄色片一级片一级黄色片| 国内久久婷婷六月综合欲色啪| 91精品国产国语对白视频| 一级黄色大片毛片| 在线视频色国产色| 国产精品二区激情视频| 交换朋友夫妻互换小说| 欧美日韩福利视频一区二区| 国内久久婷婷六月综合欲色啪| 好看av亚洲va欧美ⅴa在| 欧美亚洲日本最大视频资源| av欧美777| 亚洲狠狠婷婷综合久久图片| 欧美乱妇无乱码| 亚洲欧美精品综合久久99| 亚洲av成人一区二区三| 亚洲色图av天堂| 乱人伦中国视频| 国产精品日韩av在线免费观看 | 女性生殖器流出的白浆| 欧美日韩福利视频一区二区| 精品久久久久久电影网| 亚洲男人的天堂狠狠| 韩国av一区二区三区四区| 午夜免费成人在线视频| 搡老岳熟女国产| 99精品欧美一区二区三区四区| 亚洲欧美一区二区三区黑人| 久9热在线精品视频| 级片在线观看| 757午夜福利合集在线观看| 婷婷精品国产亚洲av在线| 男女床上黄色一级片免费看| 69av精品久久久久久| 精品久久久久久电影网| 夫妻午夜视频| 女性被躁到高潮视频| 久久欧美精品欧美久久欧美| 国产成年人精品一区二区 | 国产1区2区3区精品| 亚洲精品国产区一区二| 国产91精品成人一区二区三区| 免费人成视频x8x8入口观看| 操美女的视频在线观看| 看片在线看免费视频| 色哟哟哟哟哟哟| 免费在线观看完整版高清| 久久精品91无色码中文字幕| 国产高清视频在线播放一区| 国产蜜桃级精品一区二区三区| а√天堂www在线а√下载| 桃色一区二区三区在线观看| 男男h啪啪无遮挡| 国产精品综合久久久久久久免费 | 亚洲中文日韩欧美视频| 亚洲精品国产区一区二| www.999成人在线观看| 久久久国产成人免费| 午夜日韩欧美国产| 日韩成人在线观看一区二区三区| 久久人妻福利社区极品人妻图片| 操出白浆在线播放| 精品国产乱子伦一区二区三区| 日本黄色视频三级网站网址| 日韩欧美一区二区三区在线观看| 亚洲国产欧美一区二区综合| 多毛熟女@视频| 国产精品一区二区精品视频观看| 精品一品国产午夜福利视频| 久久亚洲真实| 国产成人啪精品午夜网站| 黄色成人免费大全| 男女下面进入的视频免费午夜 | 一进一出抽搐动态| 久久精品亚洲精品国产色婷小说| 亚洲精品一区av在线观看| 久久久精品欧美日韩精品| 人人妻人人澡人人看| 黑人操中国人逼视频| 最好的美女福利视频网| 亚洲av电影在线进入| 日韩一卡2卡3卡4卡2021年| 丝袜美足系列| 亚洲 国产 在线| 精品久久久久久久毛片微露脸| 日韩一卡2卡3卡4卡2021年| 在线十欧美十亚洲十日本专区| 亚洲国产毛片av蜜桃av| 国产亚洲精品久久久久5区| 国产亚洲欧美精品永久| 国产精品乱码一区二三区的特点 | 亚洲欧美激情在线| 国产精品九九99| 亚洲成a人片在线一区二区| 757午夜福利合集在线观看| 岛国视频午夜一区免费看| 日本vs欧美在线观看视频| 欧美乱码精品一区二区三区| 日本欧美视频一区| 这个男人来自地球电影免费观看| 窝窝影院91人妻| 一进一出抽搐gif免费好疼 | 国产单亲对白刺激| 国产精品99久久99久久久不卡| 国产精品免费一区二区三区在线| 香蕉国产在线看| 亚洲av片天天在线观看| 欧美日本亚洲视频在线播放| 99精国产麻豆久久婷婷| 亚洲一区高清亚洲精品| 欧美性长视频在线观看| 亚洲片人在线观看| a在线观看视频网站| 怎么达到女性高潮| 自线自在国产av| 最近最新中文字幕大全免费视频| 久久久久久大精品| 国产色视频综合| 亚洲精品av麻豆狂野| 免费看a级黄色片| 母亲3免费完整高清在线观看| 久久国产精品人妻蜜桃| 亚洲成人久久性| 黄色视频,在线免费观看| 高清av免费在线| 999精品在线视频| 亚洲人成77777在线视频| 精品日产1卡2卡| 身体一侧抽搐| 日韩欧美免费精品| 久久影院123| av天堂在线播放| 视频在线观看一区二区三区| xxx96com| 人人妻,人人澡人人爽秒播| 老鸭窝网址在线观看| 国产激情欧美一区二区| 自线自在国产av| 国产伦人伦偷精品视频| av网站在线播放免费| 色哟哟哟哟哟哟| 99在线人妻在线中文字幕| 日韩有码中文字幕| 热re99久久国产66热| 精品一品国产午夜福利视频| 波多野结衣一区麻豆| 久久青草综合色| 日韩精品青青久久久久久| 69av精品久久久久久| 91精品国产国语对白视频| 亚洲精品一区av在线观看| 色精品久久人妻99蜜桃| 久久国产亚洲av麻豆专区| 国产真人三级小视频在线观看| 国产成人影院久久av| 法律面前人人平等表现在哪些方面| 精品一区二区三区视频在线观看免费 | 欧美成人午夜精品| 久久香蕉国产精品| 欧美一级毛片孕妇| 国产欧美日韩一区二区三区在线| 精品免费久久久久久久清纯| 精品午夜福利视频在线观看一区| 国产亚洲精品久久久久久毛片| 黑丝袜美女国产一区| 精品久久久久久成人av| 欧美日韩黄片免| 天天添夜夜摸| 久久人妻av系列| 欧美av亚洲av综合av国产av| 桃红色精品国产亚洲av| 黑人操中国人逼视频| 国产91精品成人一区二区三区| 免费女性裸体啪啪无遮挡网站| 国产成人欧美在线观看| 日韩中文字幕欧美一区二区| 嫩草影院精品99| 正在播放国产对白刺激| 黑人巨大精品欧美一区二区蜜桃| 欧美在线一区亚洲| 丁香六月欧美| 日韩欧美一区二区三区在线观看| 国产国语露脸激情在线看| 又黄又爽又免费观看的视频| 欧美老熟妇乱子伦牲交| 三级毛片av免费| 国产乱人伦免费视频| 成人亚洲精品一区在线观看| 国产激情久久老熟女| 国产男靠女视频免费网站| 99riav亚洲国产免费| 男男h啪啪无遮挡| 99re在线观看精品视频| 欧美人与性动交α欧美精品济南到| 又黄又爽又免费观看的视频| 久久香蕉国产精品| 99久久综合精品五月天人人| 亚洲国产欧美日韩在线播放| 国产有黄有色有爽视频| 久久热在线av| 亚洲成人精品中文字幕电影 | 久久精品国产亚洲av高清一级| 国产成人欧美在线观看| 国产亚洲精品一区二区www| 99久久人妻综合| videosex国产| 人人妻人人澡人人看| 久久国产亚洲av麻豆专区| 亚洲成人久久性| 久久久水蜜桃国产精品网| 后天国语完整版免费观看| av天堂久久9| 妹子高潮喷水视频| 老汉色av国产亚洲站长工具| 桃红色精品国产亚洲av| 精品第一国产精品| 丰满饥渴人妻一区二区三| 岛国视频午夜一区免费看| 久久性视频一级片| 看免费av毛片| 12—13女人毛片做爰片一| 男女之事视频高清在线观看| 亚洲在线自拍视频| 欧美黑人精品巨大| 亚洲免费av在线视频| 色哟哟哟哟哟哟| 老鸭窝网址在线观看| 亚洲一区二区三区不卡视频| 啦啦啦 在线观看视频| av天堂久久9| 午夜a级毛片| 国产成人啪精品午夜网站| 丁香欧美五月| 色婷婷久久久亚洲欧美| 国产免费现黄频在线看| 天堂影院成人在线观看| 天天躁狠狠躁夜夜躁狠狠躁| 操出白浆在线播放| 麻豆久久精品国产亚洲av | 精品国内亚洲2022精品成人| 亚洲第一青青草原| √禁漫天堂资源中文www| 啦啦啦免费观看视频1| e午夜精品久久久久久久| 纯流量卡能插随身wifi吗| 国产黄色免费在线视频| 亚洲一区中文字幕在线| 99精国产麻豆久久婷婷| 日日摸夜夜添夜夜添小说| 欧美黄色片欧美黄色片| 久久久久精品国产欧美久久久| 免费看a级黄色片| 欧美日韩福利视频一区二区| 午夜两性在线视频| 亚洲国产欧美一区二区综合| 亚洲国产精品合色在线| 日韩视频一区二区在线观看| 一级毛片女人18水好多| 亚洲激情在线av| 熟女少妇亚洲综合色aaa.| 日韩成人在线观看一区二区三区| 女警被强在线播放| 亚洲三区欧美一区| av超薄肉色丝袜交足视频| 欧美人与性动交α欧美软件| 久久久水蜜桃国产精品网| 成人18禁高潮啪啪吃奶动态图| 国产不卡一卡二| 国产区一区二久久| 亚洲伊人色综图| 国产精品秋霞免费鲁丝片| 黄网站色视频无遮挡免费观看| cao死你这个sao货| 免费在线观看视频国产中文字幕亚洲| 俄罗斯特黄特色一大片| 99久久99久久久精品蜜桃| 黄色视频不卡| 国产成人av激情在线播放| 欧美黄色片欧美黄色片| 国产人伦9x9x在线观看| 国产精品久久久人人做人人爽| 在线播放国产精品三级| 丰满的人妻完整版| 伦理电影免费视频| 久久精品国产清高在天天线| 国产aⅴ精品一区二区三区波| 婷婷六月久久综合丁香| 精品日产1卡2卡| 啦啦啦免费观看视频1| 狂野欧美激情性xxxx| 亚洲自拍偷在线| 欧美黄色淫秽网站| 91成人精品电影| 国产区一区二久久| 国产亚洲精品第一综合不卡| 成人黄色视频免费在线看| 亚洲精品国产区一区二| 两性夫妻黄色片| 国产无遮挡羞羞视频在线观看| 超色免费av| 热re99久久精品国产66热6| 亚洲五月婷婷丁香| 亚洲熟女毛片儿| 国产精品成人在线| 999久久久精品免费观看国产| a在线观看视频网站| 亚洲精品在线美女| 麻豆国产av国片精品|