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Abstract
The external performance of designed axial-flow pump was tested with and without guide vane. Using the five-hole probe to measure the flow field at the inlet and outlet of guide vane through the measuring holes, the velocity components curves were given. The experimental results show that the power curves of pump with guide vane and without guide vane are the same. The guide vane has no influence on the performance of the impeller. At the efficiency point, the circular velocity at the outlet of guide vane is small and the recovering rotating kinetic energy of the guide vane is about 15.7% of total energy. The operating point of pump without guide vane will move to the lower flow, so the design of axial-flow pump without guide vane needs parameter compensation. Using the five-hole probe to measure the three-dimensional velocity distribution of flow field has the merits of simple operation and well applicability. The experimental data reveals the guide vane influence on performance of axial-flow pump and provides reference for the further study of flow field in axial-flow pump.
... There is no guide vane upstream and downstream of the impeller, as reduces both the pump weight and dimensions. Certainly, the contribution of the guide vane to energy transformation cannot be neglected [8]. In addition, the match between the impeller and the guide vane is another issue that influences pump performance [9,10]. ...
... Therefore, the vapor source term & S v is given by (8) The number of bubbles per unit volume of the mixture, N, is given by: ...
A reversible axial-flow pump equipped with S-shaped blades is investigated. Numerical simulation is employed as the major instrument to virtually visualize complex turbulent flows in the pump at direct and reverse operation modes. Cavitation is taken into account as well. Pressure fluctuations near the inlet and outlet of the impeller are obtained with unsteady simulation. At nominal flow rate, a relative difference of pump head of 15% is manifested between direct and reverse operation modes. At direct mode merely, cavitation zones are aggregated near the leading edge of the blade and assume a small volume fraction. The contribution of pump shaft is remarkable in terms of affecting pressure fluctuation characteristics upstream of the impeller. Characteristic frequencies immediately downstream of the impeller are analogous for the two operation modes and pressure fluctuation magnitudes are large relative to their counterparts upstream of the impeller.
... Numerous extant studies revealed that the IGV installation, which changes the absolute flow angle, influences the incidence angle 15,16 . Consequently, IGV was identified as a determining factor of pump performance; it is inferred that the installation of a variable-geometry IGV can influence the performance characteristics of a pump 17,18 . Qian et al. 19 experimentally analyzed the impact of angle variations in a variable-geometry IGV on the performance characteristics of an axial-flow pump under off-design conditions, confirming that the optimization of the angle adjustment resulted in a maximum improvement of the pump efficiency (by 2.16%) and an expanded stable operating range. ...
In this study, numerical simulation was employed to predict the performance and internal flow characteristics of the inlet of an axial-flow pump by assigning an absolute flow angle to the inlet guide vane (IGV) trailing-edge flow. Further, the finite volume method based on the three-dimensional Reynolds-averaged Navier–Stokes equations was employed to discretize the governing equations. The shear stress transport model was used as the turbulence model, and an appropriate number of nodes were selected for the hexahedral grid system through a grid-dependency test. The performance curve and changes in the internal flow field were investigated based on the variation in the flow angle at the inlet of the axial-flow pump. These results can be used to establish an efficient operational plan by adjusting the IGV angle of IGV when installing a variable IGV for an axial-flow pump.
... It is comprised of an inlet conduit, pump impeller, a guide vane, and an outlet conduit. The guide vane is used to recover the kinetic energy of the water flow in the pump impeller [5][6][7]. If the guide vane is installed in the pump, the pump efficiency will be improved [8], and the high-efficiency area position of the pump is also affected by the guide vane design [9]. ...
In order to improve the pump device efficiency of the frequent operating condition of the extra-low head pumping station, the energy performance of the front-positioned shaft tubular pump device at two guide vane inlet angles has been researched. Based on the function of the guide vane in the pump device, the guide vane blades are divided into three parts: the inlet section, the middle section, and the outlet section. Combining numerical simulation and model tests, the energy performance of the pump device with the inlet section angle adjusted to 0° and −12° were studied and compared, respectively. The research results indicate that the inlet section angle of the guide vane has a significant effect on the energy performance of the pump device. When the guide vane inlet section is adjusted clockwise, the pump device efficiency of the optimal operating point—while the efficiency of the pump device at a low head and large discharge that deviate from the optimal operating point—will be improved. The farther the working condition deviates from the optimal operating point, the greater the influence. Within the scope of the working conditions studied in this paper, the pump device efficiency of the optimal operating point is reduced by about 2%, and the pump device efficiency in the low head and high flow conditions is increased by 5% at the maximum. Adjusting the inlet section angle of the guide vane, the flow pattern in the guide vane will be improved, and the hydraulic loss of the guide vane will be decreased, thus the pump device efficiency is increased. The numerical calculation results of the energy performance agree with the model test results; the maximum error of the pump device efficiency is less than 7%. Adjusting the angle of the inlet section of the guide vane has great significance to the hydraulic design and engineering application of the extra-low head pump device.
... For example, the guide vane is used to recycle the kinetic energy of the water flow, its hydraulic design impacting the hydraulic performance of the pump and pump device. With a guide vane installed in the pump, water flow from the impeller outlet with tangential velocity is partly eliminated, and the water flow energy is converted into pressure energy, the recyclable rotation kinetic energy of the flow using the guide vane accounting for 10-15.7% of the total energy of the impeller outlet (Tang and Wang, 2006;Li et al., 2009). Compared to an axial flow pump with no guide vane, the efficiency can be improved by 5% when a guide vane is installed in the pump (Hu et al., 2008). ...
To improve the efficiency of low-head pump device in the large-discharge and low-head domain, the hydraulic characteristics of vertical axial flow pump devices with different guide vane inlet angles were studied using computational fluid dynamics (CFD) and model test methods. The Q ∼ H zz and Q ∼ η zz curves of the pump device were obtained for different impeller blade angles when the inlet angle adjustments of the guide vane were 0° and −12°. The resulting hydraulic performance was compared and analyzed. The results showed that the pump device efficiency under low-head and large-discharge conditions was improved when the guide vane inlet angle was rotated in the clockwise direction. The reason for the increased pump device efficiency was analyzed using CFD. When the guide vane inlet angle adjustments were 0° and −12° under low-head working conditions, the vortex in the guide vane was eliminated, the hydraulic loss of the guide vane decreased, and the energy performance of the pump improved. When the operational conditions of the pump device deviate from its high-efficiency zone due to limitations in the pump model or the motor itself, the application of these results could improve its hydraulic performance, which is of great significance to the design and application of low-head pump devices.
... At present, studies on the effect of the guide vane on the hydraulic performance of an axial flow pump can be summarized as follows. Li et al. [11] studied the ability of the guide vane to recover rotational kinetic energy, and Hu et al. [12] and Durmus Kaya [13] studied the influence of the guide vane on the pump efficiency for cases with and without a guide vane. Zhou et al. [14] studied the pump efficiency for different guide vanes, and Shi et al. [15] studied the hydraulic characteristics of axial flow pumps with different guide vane sweep angles. ...
Axial flow pump has been widely used in hydraulic engineering, agriculture engineering, water supply and sewerage works, and shipbuilding industry. In order to improve the hydraulic performance of pump under off-design working conditions, the influence of the inlet segment axial chord and inlet angle adjustment of the guide vane on the pump segment efficiency and flow filed was simulated by using the renormalization group (RNG) k − ε turbulent model based on the Reynolds-averaged Navier–Stokes equations. The results indicate that the inlet segment axial chord and inlet angle adjustment of guide vane have a strong influence on the pump segment efficiency. Considering the support function and hydraulic loss of the guide vane, the inlet segment axial chord is set to 0.25 times the axial chord of guide vane. On the basis of the inlet angle of the guide vane under design conditions, when the inlet segment angle is turned counterclockwise, the pump segment efficiency is improved in the lower flow rate region; moreover, the pump segment efficiency is improved in the larger flow rate region when the inlet segment angle is turned clockwise. As the conditions deviate from the design working conditions, the influence of the guide vane inlet angle on the pump segment efficiency increases. If the inlet segment angle is properly adjusted under off-design working conditions, the flow pattern in the guide vane is improved and the hydraulic loss is decreased, because the inlet segment angle matches with the flow direction of impeller outlet; consequently, the pump segment efficiency is increased.
... The research showed that the performance curve moves to the small flow area when the offset is positive; when the offset is negative, the performance curve moves to the large flow area and the optimal efficiency point drops rapidly. Zhou Rui [11] analyzed the influence of the front guide vane on the performance of the axial flow pump. The results showed that the external characteristic curve of the axial flow pump could be effectively changed after changing the placement angle of the front guide vane. ...
In order to make the centrifugal pump run efficiently and stably under various working conditions, the influences of the incoming vortex flow in the inlet pipe on the main flow in the impeller is studied numerically, based on the k - ω SST turbulence model. Some guide vanes with different offset angle were added to change the statistical characteristic of the internal flow in the inlet pipe of the centrifugal pump. Both contour distributions of internal flow and statistical results of external performance are obtained and analyzed. The results show that the existence of vanes can divide the large vortex because of the reversed flow from the rotating impeller at low flow rate conditions into small vortices, which are easier to dissipate, make the velocity and pressure distribution more uniform, improve the stability of the flow in the impeller, reduce the hydraulic loss, and improve the hydraulic performance of the pump. The pump with vanes of offset angle 25° has a small pressure pulsation amplitude at each monitoring point. Comparing with the performance of the original pump, the head increased by around 2% and efficiency increased by around 2.5% of the pump with vanes of offset angle 25°.
... The visualization of the internal flow field of the axial flow pump thus has more important significance besides the experimental investigation of its external characteristics [10,11] . Currently, the testing approaches for the internal flow field of the axial flow pump mainly include the probe measurement [12,13] , the laser Doppler measurement [14] , the high-speed photography [15,16] and the PIV measurement [17][18][19] . Among them, the PIV measuring technique serves as a kind of non-contact metrology methods with a high precision and a good instantaneous capture ability. ...
Axial flow pump is a kind of typical pumps with rotor-stator interaction, thus the measurement of the flow field between impeller and guide vane would facilitate the study of the internal rotor-stator interaction mechanism. Through a structural modification of a traditional axial flow pump, the requirements of particle image velocimetry (PIV) measurement are met. Under the condition of 0.8Qopt, the axial vortex is identified between impeller hub and guide vane hub, which is developed into the main flow and to affect the movement when the relative positions of impeller and guide vane at different flow rates are the same. Besides, the development and the dissipation of the tip leakage and the passage vortex in impeller passages are mainly responsible for the difference of the flow field close to the outer rim. As the flow rate decreases, the distribution of the meridional velocities at the impeller outlet becomes more non-uniform and the radial velocity component keeps increasing. The PIV measurement results under the condition of 1.0Qopt indicate that the flow separation and the trailing vortex at the trailing edge of a blade are likely to result in a velocity sudden change in this area, which would dramatically destroy the continuity of the flow field. Moreover, the radial direction of the flow between impeller and guide vane on the measurement plane does not always point from hub to rim. For a certain position, the direction is just from rim to hub, as is affected by the location of the intersection line of the shooting section and the impeller blade on the impeller as well as the angle between the intersection line and the rotating shaft.
... In the flow components which affect the hydraulic performance of tubular pump, the guide vane is particularly prominent, how to optimize the guide vane, choose a reasonable guide vane angle and the number of guide vane blades, and other issues remains to be elucidated. So far, most researches on the guide vane were calculating the hydraulic loss through the external characteristics test, or measuring the internal flow field by flow measurement technology [9], but due to the complex structure of guide vane, it is difficult to get a comprehensive test data. ...
The blade number of pump guide vane is an important factor that affects hydraulic characteristics of the pumping system, since the diffusion angle after the impeller is larger than as usual. It is necessary to pay more attention for its calculation and analysis. By CFD method the numeric simulation was conducted to a bulb tubular pump with different guide vane blades and the three dimensional flow fields within whole passage of pumping system was obtained. There are five different number of guide vane blades (4 blades, 5 blades, 7 blades, 8 blades and improved 5 blades) selected for the simulation and performance prediction. The influences of the guide vanes numbers on the system performance are analyzed. The hydraulic losses increases with the increase of the number of guide vane blades while the efficiency of pumping system is not fully comply with this relationship. The system efficiency for which 5 guide vanes were adopted is higher than others with different number of guide vane blades; also the velocity and the pressure distribution of flow fields are more uniform. The system efficiency for which 5 improved guide vanes is the highest with lowest hydraulic losses. The recommended alternative of guide vane is presented for the pump impeller.
... Huang Huanming etc. [4] conducted numerical simulation for axial impeller flow field on the commercial software CFX platform, and compared relative speed and streamline distribution of the 90% impeller outlet height and root position with PIV measurement results obtained relative speed and streamline the n and are compared, and verified the validity of the numerical simulation. Li Zhong, etc. [5] measured the outlet flow field of three conditions of a axial flow pump by using a spherical five-hole probe and obtained the distribution of circumferential, radial velocity component of impeller outlet absolute velocity and velocity circulation. Currently, the study on the gap between impeller outlet and guide vanes of axial flow pump is not enough, the velocity field, pressure field are not been studied well, especially movement coupling between the impeller and guide vane. ...
In order to study the influence on gap changing of the static and dynamic components in axial flow pump, the axial flow pump model (TJ04-ZL-06) that used in the eastern of south-to-north water diversion project was selected. Steady turbulence field with different gaps was simulated by standard κ-ε turbulence model and double-time stepping methods. Information on the pressure distribution and velocity distribution of impeller surfaces were obtained. Then, calculated results were compared with the test results and analyzed. The results show that the performance of pump is not sensitive with the axial gap width under design conditions and the large flow rate condition. With increasing gap width, it will be improved in low flow rate condition. The attack angle of impeller inlet in small flow rate condition become small and the flow separation phenomenon can be observed in this condition. The axial velocity distribution of impeller outlet is nonlinear and to increase the axial gap is to improve the flow pattern near the hub effectively. The trend of calculating results is identical with test. It will play a guiding role to the axial pump operation and design in south-to-north water diversion project.
The pre-swirl inflow generated by guide vanes could improve the hydrodynamic performances of centrifugal pumps as long as the inflow matches the patterns of internal flow of the impeller. In this work, we present a numerical investigation on the internal flow in a centrifugal impeller subjected to inflow artificially constructed with simple pre-swirling; unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations are performed at the designed flow rate with five values of rotating velocity of the inflow, i.e., Urot/Uref = −0.5, −0.3, 0.0, 0.3 and 0.5, where Urot and Uref denote the rotating and normal velocity component at the entrance of the inflow tube, respectively. The primary objective of this work is to reveal the three-dimensional characteristics of internal flow of the impeller as influenced by the superimposed pre-swirl inflow, and to identify the propagation of inflow within the impeller. The numerical data are presented and analyzed in terms of the streamline fields, the distributions of various velocity components along the circumferential and axial directions, the pressure distribution and limiting streamlines on the surfaces of a blade. Numerical results reveal that separation occurs around the leading edge of the blades and occasionally at the trailing edge, and the internal flow is more uniform in the central region of the channels. A noticeable fluctuation of both radial and circumferential velocities is observed at the outlet of the impeller as it is subjected to counter-rotating inflow, and the greatest fluctuation is close to the hub instead of the middle channel and shroud as for the co-rotating inflow. The boundary layer flow of suction surface is more sensitive to the inflow; occasional small-scale separation bubble occurs on the suction surface around the leading edge for some blades, and reattachment of separated flow is reduced for the counter-rotating inflow.
In axial flow pump systems, not only are the flow rates typically large but the water leaving the guide vanes almost invariably possesses a residual rotation. Since such pumps often generate only low heads, the energy content of this residual rotation often has a notable influence on the hydraulic and economic performance of the outlet conduit. The hydraulic losses and flow fields associated with a specific siphon outlet conduit under different rotational speeds are herein studied both experimentally and using a 3D turbulent flow numerical simulation. In order to experimentally verify the simulation results, the hydraulic losses are measured and flow patterns are observed for a siphon outlet conduit with a series of different guide vanes. It is observed that as the rotational speed increases the hydraulic loss within this outlet conduit increases gradually until the rotation speed reaches 300 r min−1; as the rotational speed surpasses this value, the hydraulic losses increase sharply. Yet surprisingly, residual swirl can have benefits, with the general trend being that larger rotational speeds are associated with a smaller vortex zones and a better flow field in the outlet conduit, an observation confirmed both numerically and experimentally. This research has considerable significance, both theoretically and practically, for the design of outlet conduits and guide vanes in axial flow pump system.
Diffusion guide vane number is a factor affecting on the hydraulic performance of tubular pump system. CFD method was used to simulate the three-dimensional flow of a bulb tubular pump system with different diffusion guide vanes. Five adopting schemes were the tubular pump system with 4 guide vanes 5 guide vanes 7 guide vanes 8 guide vanes and improved 5 guide vanes. The hydraulic performance of pump system and the hydraulic loss of guide vane unit were obtained and the effect of different vane number and vane shape on the external characteristics of tubular pump system were analyzed. The results showed that the hydraulic loss of guide vane was increased with the vane number but the efficiency of pump system did not fully comply with this law. The highest pump efficiency was of the case with 5 vanes. The distributions of pressure and velocity were more uniform and the minimum hydraulic loss and the highest efficiency were in scheme with the improved 5 vanes． The best guide vane number matching the impeller was proposed.
In order to study the influence of clocking effect on the centrifugal pump, the CFD method was applied to simulate the inner flow in the centrifugal pump at its design flow rate under different guide vane clocking positions. The centrifugal pump mainly consisted of volute, guide vane and impeller. The physical model was made of transparent organic glass. The clocking positions were changed by changing the circumferential connection between guide vane and volute. First, we defined the position at which the angle between guide vane blade trailing edge and volute tongue was 0° as Clocking0, and the clocking position number increases by 1 every increase of 10° clockwise. The calculation result at Clocking1 position was compared with its experimental value. The experiment was conducted in a closed test platform. The pump head and efficiency error between experimental and calculated results were less than 3%, which indicated the CFD calculation method predicted the performance of centrifugal pump relatively well such that it can be used for predicting the characteristics of other clocking positions. The external characteristics and internal flow features variations of the pump versus clocking positions were obtained. The pressure fluctuation at the tongue region and the radial hydraulic force on the impeller at different clocking positions were analyzed as well. The results indicated that with the increase of clocking position, the pump head and efficiency increased and then decreased, reaching the maximum value near Clocking2. The minimum value of pump head and efficiency was at Clocking0. The pump head at Clocking2 was 0.6m greater than that of Clocking0, and the efficiency was about 5% greater. The average relative pressure differences on each cross section of pump volute were analyzed, which indicated that the pressure variations were within 20% with the increase of clocking positions. The analysis on frequency fluctuations and frequency spectra of pressure fluctuations at locations around tongue for different clocking positions revealed that clocking effect mainly affected one and two times the blade passing frequency at the tongue region. When the clocking position number increased, both the dominant frequency and the amplitude of the pressure fluctuation increased and then decreased. The minimum value of the pressure fluctuation amplitude was at Clocking1, the maximum value of pressure fluctuation amplitude was at Clocking4, and the minimum value was 70% of the maximum. In addition, the structures of pressure fluctuation translate periodically with the sequence of clocking positions. The analysis of unsteady radial hydraulic force on the impeller showed that with increasing clocking position, the value of radial hydraulic force first decreased and then increased, the maximum value was at Clocking4, and the minimum was at Clocking1. The study demonstrates that the guide vane clocking position has the very important impact on centrifugal pump and it provides a reference for the guide vane design in centrifugal pumps.
In order to study influence of the velocity circulation at the guide vane outlet on the hydraulic performance of outlet conduit for a large pump system quantitatively, the methods to calculate velocity circulation and to measure the average angular velocity for the flow at the guide vane outlet of the pump system were put forward, the influence of circulation on the hydraulic losses of both siphon and straight outlet conduit were studied numerically and experimentally. The results indicated that the hydraulic loss of the outlet conduit was obviously influenced by the circulation at the guide vane outlet. There was an optimum circulation for the hydraulic loss of the outlet conduit to be minimized, the optimum circulation for siphon and straight outlet conduit was 0.972 and 1.308 m 2/s respectively. The hydraulic losses calculated of the siphon and straight conduit under the condition of the optimal circulation were respectively lower 0.126 and 0.180 m than those under the condition of zero circulation. This study above could be helpful to optimal hydraulic design both for outlet conduit and guide vane of an axial-flow pump.
The guide vanes were designed by using the axial flow pumps isolated blade design method based on Gottingen airfoil blade. The experimental studies on the basic rule and the regulatory mechanisms of prewhirl regulation for the centrifugal pump were made. Comparison experiment tests showed that the inlet guide vane installed with long-string side close to the center axis on the improvement of the external characteristics of centrifugal pump was better than the other. Also the inlet guide vane installed with long-string side close to the center axis has enlarged the high efficiency scope and improved the hydraulic performance of the centrifugal pump. When compared with the performance of the centrifugal pump without inlet guide vane, the peak value of efficiency was enhanced by 2.3% after the guide vane was installed. This method improved efficiency and saved energy for the centrifugal pump.
A series of vaned-diffusers, which are with various vane inlet angles, vane angle distributions along streamline, leading and trailing edge positions, were designed for a mixed-flow pump impeller by using the point-by-point integration method that was applied to generate the three-dimensional camber of vane on the streamlines determined by employing an iterative calculation between two kinds of relative stream surfaces. The vane thickening and leading and trailing edges smoothing were conducted on a plane of conformal mapping. 3D turbulent flow fields inside the mixed-flow pump with the same impeller but different diffusers were simulated by solving the Reynolds time-averaged N-S equations and the standard k-ε turbulence equations based on SIMPLE algorithm, and the pump hydraulic efficiencies were predicted, consequently, the correlations of both the vane wrap angle and hydraulic efficiency to different design parameters were obtained. In addition, effects of various design parameters on the mixed-flow pump performance were analyzed by means of relative velocity, static pressure and total pressure distributions in the inlet and outlet to the diffusers. The results showed that the diffuser vane inlet angle has the strongest influence on the performance and a reasonably selected inlet angle can reduce the shock loss. The vane angle distributions along streamlines should be selected by considering the control of wrap angle to reduce the hydraulic friction loss in diffuser. The leading edge and trailing edge positions should be selected with the consideration of static pressure recovery ability and hydraulic friction loss across diffuser.
In order to analyze the effects of adjustable guide vane (AGV) on axial pumps working in saddle zone, in the hope of optimizing adjusting laws, performance test of a new axial-flow pump with AGV was carried out on the pump test bed. Q-H, Q-η and Q-P curves at different guide vane angles were obtained. The effects of AGV on hydraulic performance of the model pump in saddle zone were analyzed. The results show that, at the same flow rate, head and efficiency of axial flow pump increase as guide vane angle is adjusted from 0° to -5°. With AGV, the separation vortex in the flow channel is suppressed effectively; flow regime at pump outlet is optimized obviously; kinetic energy recovery rate is improved. Head and efficiency of the pump are improved by 0.15 m (0.0469Hd) and 1.93% respectively. The critical flow discharge is decreased by 0.00494 m3/s and the range of saddle-shaped zone is narrowed by 6.64%, broadening the range of stable working zone. At guide vane angle of -5°-0°, the shaft power changes little. In this experiment, the best values of hydraulic performance obtained are at -5° guide vane angle, but they can be further improved.
With the aim to explore the influence of inlet guide vane on the cavitation performance of centrifugal pump, the cavitation experiment on IS 150-125-250 centrifugal pumps with original design inlet guide vane has been conducted. Using the Zwart-Gerber-Belamri cavitation model, the 3D unsteady cavitation flow in centrifugal pump flow channels has been simulated. The result shows that the negative pre-whirl by guide vane regulation could improve the cavitation performance of centrifugal pump in a certain angle range, and the cavitation performance was deteriorated when the angle exceeds the certain value. The positive pre-whirl regulation deteriorated the cavitation performance of centrifugal pump, and it become even more serious with the increasing positive pre-whirl angle. The analysis of the vapor volume fraction distribution in impeller channels indicates that the negative pre-whirl angle reduced the cavitation zones in impeller, and the positive pre-whirl angle expanded the cavitation zones in impeller channels.
3D numerical simulation was carried out to a two-stage variable vane axial flow fan using Fluent software, so as to study the effects of the first-stage guide vane structure on aerodynamic performance of the fan, such as long-short composite guide vane or single long guide vane, etc., and to compare the fan performance when the short vane is placed at different axial and circumferential positions and has different lengths. Results show that both the single-stage diffusion performance and the overall aerodynamic performance of the long-short composite guide vane are superior to those of the single long guide vane. When the short vane is located at inlet of the first-stage guide vane in the intermediate pitch between two adjacent long vanes, both the full pressure and efficiency of fan shall reach the optimum, especially the efficiency will be significantly higher than at other places. In addition, the length of short guide vane also has significant effects on the fan performance. Increasing or decreasing the length of short guide vane will cause deterioration of the fan performance and result in notable irreversible loss, when the length of the short guide vane is 320 mm.
To design compact multistage centrifugal pumps, a circumferential crankle guide vane was proposed to match their compact structure. The basic design principle originated from the twisted centrifugal impeller design method and the design method of this guide vane was investigated systematically. By fixing the top curve of the guide vane and extending the bottom curve forward along a circumferential direction, a crankle surface is shaped. This design method has two merits. Firstly, the bottom curve of the first guide vane is extended circumferentially forward to guarantee a large throat flow area. And secondly, a diffuser-like passage is naturally formed by the extended surface and the cylindrical surface of the next blade, which enhances its pressure recovery ability. In addition, the blade surface is divided into two segmented parts, that is, a full twisted surface and a cylindrical surface, thus the casting and molding of the guide vane is more convenient. To reduce the design cycle of the guide vane, a hydraulic design system of the circumferential crankle guide vane was developed using the secondary development technique. Based on this system, different configurations of guide vane were developed. Through evaluation of the different configurations of guide vane, an optimal configuration was obtained by means of CFD analysis. To validate the CFD results, a prototype multistage pump was developed and manufactured. The prototype pump testing showed that the stage head was 9 m, and its efficiency was 57.8%, which could meet the design requirement. To conclude, the guide vane design method is beneficial for energy-saving in multistage centrifugal pumps, and this method could provide useful guidance for the development of compact multistage centrifugal pumps.
Based on the computational fluid dynamics (CFD) software, this paper studied the influence of the post guide vane under different sweep angles on the hydraulic performance of the axial flow pump device. The purpose was that through changing the angle of blade forward and back sweeping, the post guide vane could as much as possibly recover the velocity circulation of the impeller outlet, at the same time, the hydraulic loss of the guide vane could be not too large, so as to improve the hydraulic characteristics of the axial flow pump device. This paper used the Turbo-Grid software to build the model and carry out the mesh division of the post guide vane and the impeller, used the Pro/E software to build the models of the inlet straight pipe with water-guiding cone and the standard 60° outlet pipe, and then used the ICEM to carry out the structured-grid division. Then, the hydraulic property of the axial flow pump device was analyzed through the CFX software. There were 6 different post guide vane sweeping schemes, which were forward sweep 24°, forward sweep 16°, forward sweep 8°, 0°, back sweep 8°and back sweep 16°. Numerical simulation of the axial flow pump device adopted the standard k-ε model, and each sweeping scheme of post guide vane had 8 flow points including 280, 300, 320, 340, 360, 380, 400 and 420 L/s. The influence of different post guide vane sweeping angles on the energy characteristics of the axial flow pump was analyzed under the design condition and the non-design condition. Then the hydraulic loss of the post guide vane and the outlet pipe was calculated and analyzed. Finally, the experimental study of the energy performance of the axial flow pump device was carried out. The results showed that, the test performance curve trend was consistent with the numerical simulation; the flow-head curve showed a little deviation under small flow, other parts fitted well, and the flow-efficiency curve did not fit so well, but the error between the test data and the numerical data was within 3% that was very small. The results from numerical simulation and experimental study had been mutually authenticated. The results of the study showed that: under small flow condition and near design condition, the energy performances of axial flow pump device of different sweep angles had comparatively large difference, on the other hand, the energy performances were almost the same under large flow condition; under the design condition, the flow separation of the airfoil tail of back sweep guide vane was very serious, and hydraulic loss of the guide vane was very large; the guide vane of forward sweep 16° could as much as possibly recover velocity circulation of the impeller outlet, also its hydraulic loss was the smallest. Therefore, the guide vane of forward sweep 16° has a good effect to improve the energy performance of the axial flow pump device. ©, 2015, Chinese Society of Agricultural Engineering. All right reserved.
Axial-flow pumps are widely used in many fields where low pumping head and large flow rate are required such as irrigation and drainage, flood control, bio-environmental protection and inter-basin water diversion. Conventional axial-flow pump diffuser is designed with post fixed guide vanes to eliminate circulation, diffuse water and decrease flow velocity while converting dynamic energy to pressure energy. Under designed flow rate the inlet setting angle of the fixed guide vanes is designed to be equal to the outlet flow angle of the impeller blades which is regarded to be the best operating condition. Under off-design conditions the outlet flow angle of the impeller blades does not match the inlet setting angle of guide vanes any more. As a result hydraulic losses are increased, flow separation appeared and vortex generated inside the diffuser, the operation conditions of pump is deteriorated, bringing in bad cavitation characteristics, more energy consumption and lower pumping efficiency. The proposal of Axial-flow pumps with adjustable guide vanes are put forward in this paper, in which the inlet setting angle of guide vanes can be adjusted to coordinate with the change of flow rate and impeller blade setting angle and guarantee the outlet flow angle of impeller blades matching the inlet setting angle of guide vanes. The three-dimensional time-averaged N-S equations, closed by the standard κ–ε turbulence model, are adopted to simulate the internal flow fields of axial-flow pumps with fixed and adjustable guide vanes, and their performances are predicted. The internal flow mechanism of an axial-flow pump with adjustable guide vanes is investigated, and computational fluid dynamics is adopted to simulate and analyze the internal flow fields. Computation results indicate that the value of the highest pumping efficiency is slight changed while the vane setting angle is adjusted when the inlet setting angles of blades are fixed and the setting angles of guide vanes are regulated. Under off-design conditions the flow conditions inside the diffuser of axial-flow pump with adjustable guide vanes can be improved, the hydraulic loss reduced and the pumping efficiency can be raised effectively.
According to the basic theory of turbomachinery design and inlet guide
vanes prewhirl regulation, two different airfoils inlet guide vanes of
prewhirl regulation device were designed, the influence of the positive
prewhirl to the performance of centrifugal pump were studied based on
different airfoils. The results show that, for a single-suction
centrifugal pump: Gottingen bowed blade-type inlet guide vane adjustment
effect is better than straight blade-type inlet guide; appropriate
design of positive prewhirl can elevate the efficiency of centrifugal
pumps. Compared with no vane conditions, the efficiency of centrifugal
pump with prewhirl vanes has been greatly improved and the power
consumption has been reduced significantly, while has little influence
on the head.
Based on the Navier-Stokes equation set and the standard k-ε turbulence model, the numerical simulation of the flow field in axial flow pump was conducted on the platform of commercial software CFX by using SIMPLEC method. The pump performance curves resulted from numerical simulation was verified with the experimental results; and then, the computational distribution of relative velocity and streamline in 90% blade span and the discharge region was compared with the results measured by PIV in the same positions, and they were in a good agreement, which indicated the validity and correctness of the numerical simulation. Furthermore, the flow features and the reasons caused efficiency fall of axial flow pump under different flow rates were analyzed, and the results provided some references to the internal flow analysis and the performance improvement of axial flow pump.
The purpose of the present study is to investigate the performance and three-dimensional flow fields in a water-jet pump. TASCflow is employed to simulate the rotator–stator coupling flow field. A standard k–ε turbulence model combined with standard wall functions is used. In order to investigate the effect of a rear stator on flow fields, the flows in two water-jet pumps with and without a rear stator are studied. Computational fluid dynamics (CFD)-predicted overall performances are in good agreement with the experimental results. Then the flow fields, such as the pressure distribution on the blade surfaces, and the axial and tangential velocity distribution, especially the radial loading distribution, are investigated at different flow rates. In addition, the effects of a rear stator and different spacings between the rotor and the stator on the overall performance and the flow fields of the water-jet pump are also investigated.
Cavitation flows induced around an axial-flow pump blade and inside a high pressure cage-type valve are simulated by a two-dimensional
unsteady Navier-Stokes analysis with the simplest treatment of bubble dynamics. The fluid is assumed as a continuum of homogeneous
dispersed mixture of water and vapor nuclei. The analysis is aimed to capture transient stages with high amplitude pressure
change during the birth and collapse of the bubble especially at the stage of cavitation inception. By the pump blade analysis,
in which the field pressure is moderate, cavitation number of the inception and locations of developed cavitation are found
to agree with experimental results in a wide flow range between high incidence and negative incidence. In the valve flow analysis,
in which the water pressure of 5MPa is reduced to 2MPa, pressure change responding to the bubble collapse between the vapor
pressure lower than 1 KPa and the extreme pressure of higher than 104 KPa is captured through a stable computation. Location of the inception bubble and pressure force to the valve plug is found
agree well with the respective experimental features.