Dissertations / Theses on the topic 'Axial flow impeller blades'

Stratification of water in large reservoirs occurs in summer, or at anytime in hot climates where the water surface is exposed long-term to sunlight and the water surface is heated. Natural mixing will not occur due to the cooler and denser water always staying at the lower levels. Therefore, mechanical circulators are designed to prevent water quality problems related to stratification and depletion of dissolved oxygen. Impellers that produce the flow in mechanical circulators are available in different sizes and these impellers are designed to produce different flow rates. Due to hydraulic loadings, impellers have to be strong and durable. Loadings on impellers depend on their geometries and therefore, a durable impeller is a good combination of the use of correct materials and good geometry. Long and slender impellers are prone to failure when subjected to high hydrodynamic loadings. Nowadays, designers have very limited information on predicting the stresses on impellers and the deflection patterns of impellers because there are no design rules in designing these impeller blades and there is no such thing as "best geometry". A good impeller blade design is by guesswork and experience. In order to design the geometry that suits this application, trial-and-error finite element analyses have been conducted in this project to minimize stress levels on the blades. This research involves the use of finite element analysis (FEA) to predict stress and deflection of impeller blades used on large (5m diameter) ducted axial flow impellers as the first step in the design process. Then, based on the results, improvements have been done to the models until the final design was made. As far as the author has been able to determine, this has not been researched before. Finite Element Analysis has been used on wind turbine blades, rudders and hulls of boats but not on axial flow impeller blades of the type used in this project. For the purpose of this project, commercial finite element computer program packages STRAND6 and STRAND7 were used as the main analysis tools. A static line load increasing linearly with radius along the blade has been used to simulate the assumed hydrodynamic loading, and applied to all FEA blade models. The analysis results proved the stresses on blades are largely dependant on the blade geometry. From the analysis results, the author modified the stacking arrangement of the FEA elements in order to minimize both the tensile stresses and the displacements of the blades at the tip. Parametric studies have been done in order to obtain the best FEA impeller blade model.

Stratification of water in large reservoirs occurs in summer, or at anytime in hot climates where the water surface is exposed long-term to sunlight and the water surface is heated. Natural mixing will not occur due to the cooler and denser water always staying at the lower levels. Therefore, mechanical circulators are designed to prevent water quality problems related to stratification and depletion of dissolved oxygen. Impellers that produce the flow in mechanical circulators are available in different sizes and these impellers are designed to produce different flow rates. Due to hydraulic loadings, impellers have to be strong and durable. Loadings on impellers depend on their geometries and therefore, a durable impeller is a good combination of the use of correct materials and good geometry. Long and slender impellers are prone to failure when subjected to high hydrodynamic loadings. Nowadays, designers have very limited information on predicting the stresses on impellers and the deflection patterns of impellers because there are no design rules in designing these impeller blades and there is no such thing as "best geometry". A good impeller blade design is by guesswork and experience. In order to design the geometry that suits this application, trial-and-error finite element analyses have been conducted in this project to minimize stress levels on the blades. This research involves the use of finite element analysis (FEA) to predict stress and deflection of impeller blades used on large (5m diameter) ducted axial flow impellers as the first step in the design process. Then, based on the results, improvements have been done to the models until the final design was made. As far as the author has been able to determine, this has not been researched before. Finite Element Analysis has been used on wind turbine blades, rudders and hulls of boats but not on axial flow impeller blades of the type used in this project. For the purpose of this project, commercial finite element computer program packages STRAND6 and STRAND7 were used as the main analysis tools. A static line load increasing linearly with radius along the blade has been used to simulate the assumed hydrodynamic loading, and applied to all FEA blade models. The analysis results proved the stresses on blades are largely dependant on the blade geometry. From the analysis results, the author modified the stacking arrangement of the FEA elements in order to minimize both the tensile stresses and the displacements of the blades at the tip. Parametric studies have been done in order to obtain the best FEA impeller blade model.
Thesis (Masters)
Master of Philosophy (MPhil)
School of Engineering
Full Text

\Yith the current develop111ent in computer technology and Computational Fluid D)"n<'tlllics techniques, t.he si11utlation within axial flow compressors becomes 1110re and 1110re pract.ical and beneficial to the compressor designs. Due to the insufficient capabilit)" of today's COll1put.ers for three-dimensional unsteady flow 1110delling of 111Ult i~Llg(' axial flow compressors, sophisticated models of steady state flow and perfor111ance 1110delling of the C0111prcssors deserve to be thoroughly investigated. In l1utltistage C0111pressor sinlulations with steady state methods, frame of reference is fixed on blades and the c0111putational domains for rotors and stators haye relati\"e rotation. One of the difficulties in such simulations is how to pass information across the interfaces between blade rows without losing continuity. Two 111ajor stead)" state modelling approaches, a mixing plane approach based on Denton's circu111ferentially non-uniform mixing plane model and a deterministic stress approach based on Adamczyk's average passage model, are investigated and compared with each other through the flow predictions of the third stage of Cranfield Low Speed Research Compressor at peak efficiency operating condition. In the deterministic stress approach, overlapped solution domains are introduced to calculate deterministic stresses in order to "close" the time-averaged governing equation system and the influence of the downstream blade row of the blade row under investigation has to be imposed through the simulation of bodyforce and blade blockage effect of the downstream blade row. An effective method of simulating bodyforce and blade blockage effect has been developed and proven to be simple in programming. ConYentionally, boundary conditions are specified in CFD calculations based on experimental data or other empirical calculations. By taking advantage of the special flow features in rear stages of multistage axial flow compressors where each rear stage behaves like a repeating stage of its neighbouring stages in terms of flow pattern at the inlet and the exit of these stages, a repeating stage model has been developed aiming at significantly simplifying the boundary conditions when simulating rear stages of a multistage axial flow compressor with only mass flow rate and stage exit average static pressure required as global input. A computer simulation system 1'/ STurbo3D has been developed to investigate a11d assess different steady state simulation models within multistage compressor environment. It has been proven that with the mixing plane model M STurbo3D is able to predict flows in multistage low speed axial flow compressors with acceptable accuracy. Application of the repeating stage model to the third stage of LS RC shows that the prediction with this model has equivalent accuracy to the prediction with the conventional boundary setting, and proves that the repeating stage model is an effective alternative to the expensive complete compressor simulation. The deterministic stress model provides more information of rotor-stator interaction and slightly better performance prediction than the mixing plane model, but the benefits of the model is not significant when applied to low speed axial flow compressors.

Axial-flow pumps or propeller pumps allow fluid to enter the impeller axially. The impeller can be driven directly by a sealed motor in the pipe or mounted to the pipe from the outside, or by a right angle drive shaft that pierces the pipe. These pumps discharge fluid nearly axially, pumping the liquid in a direction that is parallel to the pump shaft. Axial-flow pumps are typically used in high-flow rate, low-head applications. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34873

Two main sources of high losses in small axial turbines are the tip leakage loss and the Reynolds number related loss. The extents of these losses are directly related to blade geometry. Due to limitation in manufacturing capabilities and the prohibitive cost of precision engineering often the manufactured blade is very different from the design or the ideal blade shape and as a result the component efficiency degrades. Reynolds number effect plays a very important role in the low efficiency of small axial turbines. The effect of low Reynolds number is essentially separation of the flow resulting in high losses. Unlike in large turbines, where the Reynolds number is above 10e5, depending on size the Reynolds number over which a small turbine operates can be as low as 10e4. At this range the flow is laminar over a large extent of the blade and is very susceptible to laminar separation resulting in high losses. Since due to the aerodynamics this is inevitable, the only resort for an engineer is to design a blade that will delay separation to a point which will either result in turbulent separation or a transitional-laminar separation resulting in a smaller separation bubble. The design of such blades requires in depth knowledge on the field of flow transitional methods. An existing flow transition model has been implemented with simple modifications for separated flow in an in-house CFD code. Once validated against available experimental data, a parametric study has been conducted, where the effects of Reynolds number, velocity ratio, the turbulence levels and the location of maximum loading has been tested on a simulated turbine flow. Two different velocity distributions were tested. The combined results provided an understanding of the aerodynamic behaviour of small low Reynolds number axial turbine blades and provided a basis of better blade design.

Thesis (PhD (Mechanical and Mechatronic Engineering)--University of Stellenbosch, 1990.
260 leaves printed single pages, preliminary pages i-xxi and numbered pages Chapter 1/1.1-1.3, Chapter 2/2.1-2.17, Chapter 3/3.1.1-3.10, Chapter 4/4.1-4.18, Chapter 5/5.1-5.3, References pages R.1-R.7, Appendix A pages A.1-A.34, Appendix B pages B.1-B.34, Appendix C pages C.1-C.26, Appendix D pages D.1-D.16, Appendix E pages E.1-E.30, Appendix F pages F.1-F.39. Includes bibliography, list of tables, figures and symbols.
Digitized at 600 dpi grayscale to pdf format (OCR), using a Bizhub 250 Konica Minolta Scanner.
ENGLISH ABSTRACT: The ultimate goal of this project is to ensure a better understanding of the governing mechanisms present when flow distorting components are installed in close proximity of an axial flow fan. The effect of different parameters on the operation of axial flow fans is investigated. These parameters are divided into flow enhancing and flow reduction effects. The performance of an axial flow fan can be enhanced by changing the tip clearance, by adding a solid disc to the hub of the fan or by varying the number of fan blades. Flow reductions are caused by components such as inlet grids, walkways and their supporting structures, heat exchangers and windwalls. The effects of flow enhancing components are measured and compared to the results of other authors. The sensitivity of these effects to parameters such as the type of fan rotor and the specific system in which the rotor is installed is highlighted. The system effect (the interaction between the fan rotor and flow resistances in close proximity of each other) of individual components, as well as the combination of different components, is predicted both theoretically and experimentally. These predictions are compared to measured data relevant to the components in an installation where the system effects are present. The results are correlated to the kinetic energy flux coefficient of the flow at different locations within the installation. Experimental data obtained from a full scale unit (inlet shroud diameter of 9,216 m) are used to compare to scaled data from the model (inlet shroud diameter of 1,542 m). The hub to tip ratio of the axial flow fans investigated is 0,15. The most important conclusions are that the performance of the type of axial flow fan under investigation can be improved by reducing its tip clearance and by installing a solid disc to the downstream side of the rotor. An increase in the number of blades of the fan leads to only marginal improvements in the fan performance. The overall performance of the system can also be improved by removing some of the flow resisting components, or by changing their relative positions. All these conclusions are based on the assumption that the power input to the fan rotor remains constant.
AFRIKAANSE OPSOMMING: Die uiteindelike doel van hierdie projek is om te verseker dat die beherende meganismes wat teenwoordig is wanneer vloeiversteurende komponente in die nabyheid van 'n aksiaalwaaier geinstalleer word, beter verstaan word. Die effek van verskillende parameters op die werkverrigting van aksiaalwaaiers word ondersoek. Hierdie parameters word verdeel in vloeiverbeterings- en vloeiverminderingseffekte. Die werkverrigting van 'n aksiaalwaaier kan verbeter word deur die lempuntspeling te verstel, deur 'n soliede skyf aan die naaf van die waaierrotor te installeer, of deur die aantal lemme te verander. Die vloeiverminderings word veroorsaak deur inlaatsiwwe, loopvlakke en hul ondersteuningsstrukture, warmteruilers en windwande. Die effekte van vloeiverbeteringskomponente word gemeet en vergelyk met die resultate van ander outeurs. Die sensitiwiteit van hierdie effekte op parameters soos die tipe rotor en die spesifieke stelsel waarin die rotor geinstalleer is, word uitgelig. Die stelseleffek (die interaksie tussen die rotor van die waaier en vloei weerstande wat naby mekaar geinstalleer is) van individuele, sowel as 'n kombinasie van verskillende komponente, word teoreties en eksperimenteel voorspel. Hierdie voorspellings word dan vergelyk met eksperimentele data wat van toepassing is op die komponente in 'n installasie waar stelseleffekte voorkom. Die resultate word gekoppel aan die kinetiese energievloedkoeffisient van die vloei by verskillende posisies binne die installasie. Eksperimentele data, verkry vanaf 'n volskaaleenheid (inlaatmondstukdiameter van 9,216 m), word met die geskaleerde data van die model (inlaatmondstukdiameter van 1,542 m) vcrgelyk. Die naaf- tot hulsverhouding van die aksiaalwaaiers wat ondersoek word is 0,15. Die belangrikste gevolgtrekkings is dat die werkverrigting van die tipe aksiaalwaaier wat ondersoek word verbeter kan word deur die lempuntspeling te verminder en deur 'n soliede skyf te installeer by die stroomaf kant van die rotor. 'n Toename in die aantal lemme van die waaier lei slegs tot marginale verbeterings in die werkverrigting van die waaier. Die totale werkverrigting van die stesel kan ook verbeter word deur sommige vloeiweerstandskomponente te verwyder, of deur hulle relatiewe posisies te verander. Al hierdie gevolgtrekkings is gebasseer op die aanname dat die drywingsinset na die waaierrotor konstant bly.

An accurate knowledge of turbine blade surface temperature is desired in order to obtain maximum performance from turbine engines. A limited spectrum radiation pyrometer can be used for blade temperature measurement. A model is presented which predicts the output signal from the detector unit of a pyrometer in a turbine engine application. Six inputs are required for the model. The inputs are the turbine blade geometry, location of the pyrometer with respect to the blades being viewed, focusing parameters of the pyrometer, type of detector, transmission curve of the optical system, and an estimate of the blade surface temperature. The model uses Fortran 77 and IBM CADAM to create a three dimensional representation of the pyrometer path across the blades along with the intercepted target spots. Once the target spot areas are determined, the photocurrent output signal of the detector is predicted as a function of percent blade chord and time. Results are shown for different detectors and temperature distributions. Experimental data is also included, and a comparison is made between the data and the model. Any of the model input parameters can be varied so that different pyrometer schemes can be evaluated at either the initial design phase or after installation.
Master of Science

The thesis deals with the construction design of reversible swirl turbine used in a tidal range power plant for bidirectional operation. The theoretical part provides an overview of state-of-the-art technologies in the usage of tidal energy, mostly by means of tidal range and stream tidal power plants. It also analyses respective designs of tidal turbines and their advantages and disadvantages. The practical part of the thesis demonstrates individual steps applied when examining loading forces and also shows the design method and strength inspection procedure of the turbine and its parts, especially of the impeller, gears, shafts and bearings. Lastly, the paper outlines the selection approach of the most appropriate water plant generator.

碩士
華梵大學
機電工程學系博碩專班
96
In this study, flow fields of axial flow pumps with different numbers of rotating blade and different numbers of stator vane are analyzed. A commercial finite volume code, STAR-CD, is utilized to simulate the flow fields under the impeller rotating speed of 7000 rpm. The governing equations for the flow fields are conservation of mass and momentum equations. For the turbulence calculations, a high Reynolds number k-ε turbulence model is used. Multiple rotating frames and steady interaction technique have been used to simulate the flow fields. A total of four different pump designs are investigated in this study. The models’ variations include two different numbers of rotating impeller blade and two different numbers of stator guide vane. Model 1 has a cone shape hub and has 4 rotating blades with 6 stator vanes. Model 2 uses the same hub and rotating blades as model 1 but possesses 12 stator vanes. Model 3 and model 4 have a cone shape hub and 3 rotating blades. Model 3 has 6 stator vanes while model 4 has 12 stator vanes. The results show that model 2 possesses the best efficiency and model 1 is the 2nd and model 4 is 3rd while model 3 is the last . In terms of thrust force, model 2 has the highest value and model 1 is the 2nd and model 4 is 3rd while model 3 is the last . Regarding the effects of the number of stator vane, models with 6 stator vanes have higher flow rates but smaller torque and thrust force than those models with 12 stator vanes. Hence, efficiency is not directed related with flow rate. In addition, models with 12 stator vanes have higher torque and thrust force. Both three and four rotation blade impellers will produce cavitation. Cavitation phenomenon only occurs in rotating blade region but not in the guide vane region.

碩士
華梵大學
機電工程研究所
93
In this study, flow analyses of axial flow pumps with different rotating impeller hub and blade designs and different number stator vanes are performed. A finite volume based code, STAR – CD, is utilized to simulate the flow fields under the impeller rotating speed of 8000 rpm. The governing equations for the flow fields are conservation of mass and momentum equations. For the turbulence calculations, a high Reynold number k-ε turbulence model is used. Multiple rotating frames and steady interaction technique have been used to simulate the flow fields. Five pump designs are investigated in this study. Model 1 to model 4 are different in hub shape, while model 4 and model 5 are different in stator’s guide vane number. Among them, the radius of hub of model 1 is unanimous in size, and the shape is like a cylinder. The model 2 has a smaller size of the hub with the shape of a cup. Model 3 has a even smaller sizer and has the shape of the funne1. Model 4’s hub has a similar funnel shape with model 3 but has different number of stator vane. Model 5 has the same hubs as model 4. Models 1,2,3,5 has a stator with 6 vanes. However, Model 4 has a stator with 12 guide vanes. The results show that model 1 possesses the best efficiency without considering cavitation. However, due to the fact the cavitation region of model 1 is significant, it is not a good choice. Model 3’s efficient is not as good as that of model 2. Although model 2 has a very good efficiency, however, its cavitation zone is bigger than that of models 4 and 5. In addition, model 4’s mechanical efficiency is better than model 2’s efficiency. It is found that model 4 with a stator of 12 guide vanes is superior to model 5 with a stator of 6 guide vanes in terms of overall efficiency. It is concluded that model 4 is the best choice because of its high efficiency and small region of cavitation.

碩士
華梵大學
機電工程研究所
95
In this study, flow fields of axial flow pumps with different rotating impeller hub designs and different number stator vanes are analyzed. A commercial finite volume code, STAR-CD, is utilized to simulate the flow fields under the impeller rotating speed of 7000 rpm. The governing equations for the flow fields are conservation of mass and momentum equations. For the turbulence calculations, a high Reynolds number k-ε turbulence model is used. Multiple rotating frames and steady interaction technique have been used to simulate the flow fields. A total of four different pump designs are investigated in this study. The models’ variations include two different hub designs and two different numbers of stator guide vane. Model 1 has a cylindrical hub with 6 stator vanes. Model 2 uses the same hub as model 1 but possesses 12 stator vanes. Model 3 and model 4 have a cone shape hub. Model 3 has 6 stator vanes while model 4 has 12 stator vanes. The results show that model 1 possesses the best efficiency and model 2 is the 2nd and model 4 is 3rd while model 3 is last without considering cavitation. Due to the fact that cavitation region of model 1 is significant, it may not be the best choice. If we compare the torque and thrust force, model 4 obtains a higher torque and thrust force than model 1, although model 4’s efficiency is not as good as model 1. Moreover, if we compare the effects of the number of stator vanes, we can see that models with 6 stator vanes have higher flow rates but smaller torque and thrust force than those models with 12 stator vanes. Thus, efficiency is not directed related with flow rate. In addition, models with 12 stator vanes have higher torque and thrust force.

碩士
國立臺北科技大學
製造科技研究所
94
Five-axis numerically controlled machining has more recently been applied in national defence and motor vehicle industries to produce precisely complex surface parts, such as aerospace parts, impeller blades, dies and moulds. For promoting the application of five-axis machining technology, this research presents a milling process plan for machining the impeller blades was provided. The impeller of the axial-flow compressor contains a lot of thin blades on the hub of the impeller. In addition, the thin blades of the impeller possess overlapped surfaces and with large blade height/thickness ratio (about 20:1), so that the machining of the impeller is not easy. At the present time, the impeller machining usually adopts five-axis numerically controlled machines because of the tool motion has two additional degrees of freedom compared with traditional three-axis machining. In this paper, a new milling process method for thin blade with twisted ruled surfaces has presented. Our strategy is to change the tool orientation such that the overcut or undercut is minimized. Unigraphics CAD/CAM system, Procam system, and Vericut system were used to model the geometry of the impeller and to simulate and verify the cutting process in five-axis machine (X, Y, Z, A, and B axes). The validity and effectiveness of the blade milling process was demonstrated on Forestline five-axis machine with Num 1060M controller.

碩士
華梵大學
機電工程研究所
92
Axial flow pumps are widely used in a wide range of applications. The different designs of axial flow pump have different hydrodynamic efficiency and mechanical efficiency. In this study, we use a finite volume based code, STAR-CD, to simulate the flow fields in an axial flow pump under four different impeller rotating speeds, 5500 rpm, 6000 rpm, 6500 rpm, and 7000 rpm. The governing equations for the flow fields are conservation of mass and momentum equations. For the turbulence calculations, a high Reynold number k-ε turbulence model is used. Multiple rotating frames and steady interaction technique have been used to simulate the flow fields. Simulated results match the experimental observations of other investigators. The fluid flow in the axial flow pump rotates and accelerates by the impeller’s motion, while the stator van make it distribute smoothly and flow out from the nozzle. The flow fields are influenced by the boundary layer on impeller, stator vane and wall. Phenomena such as reversed flow, vortex are observed. When the fluid flows through the impeller, it will initiate reversed and separated flow because of the viscosity effects. The reversed and separated flow forms at the blade suction side and develops to the blade trail. It also interacts with the leakage flow and produces the leakage vortex. In the present study, we also conduct a analysis about hydrodynamic efficiency and mechanical efficiency of whole fluid field.

On unshrouded axial flow turbine rotors, the tip clearance, required for thermal expansion and manufacturing limitations, allows fluid to leak from the pressure side to the suction side of the blade. This flow across the blade tip causes a large proportion of the overall rotor loss. In this work, the flow was visualized, microscopic static pressures taken and flow field measurements were done in the blade tip region to investigate the complex nature of tip clearance flows. An annular turbine cascade with a rotating outer casing was used to simulate the relative motion at the tip of an axial rotor. It was found that relative motion did not have a significant effect on the basic structure of the micro-flow, even though it reduced the leakage mass flow rate which is important as far as mixing loss formation is concerned. The existence of a narrow, very low pressure depression, caused by the flow remaining attached around the sharp pressure corner edge, was confirmed. The width and pressure of the separation bubble were found to be strongly dependent on gap size but the relationship was not linear. The point at which the separation bubble reattaches was seen to coincide with a slight rise in static pressure. The separation bubble which caused the majority of the internal gap loss, and which was thought to contribute to the mixing loss, was shown to disappear when the pressure corner was given a radius of 2,5 gap widths.A linear cascade was used to evaluate the performance of two blade tip shapes that substantially reduced internal gap loss and to compare them to a standard sharp or flat tip blade. A method whereby linear cascade data was analyzed as if it were a rotor with work transfer, was used to evaluate the performance of the various blade tip geometries. It was found that both modified tips increased the mixing loss due to the extra leakage mass flow rate. The first tip with the radiused pressure corner was seen to have a lower efficiency than the flat tip blade. A second tip that was contoured to shed flow in a radial direction and thus decrease the leakage mass flow rate through the gap was seen to significantly increase the overall efficiency.
Thesis (M.Sc.)-University of Natal, Durban, 1989.

The on-line condition monitoring of turbomachinery blades is of utmost importance to ensure the long term health and availability of such machines and as such has been an area of study since the late 1960s. As a result a number of on-line blade vibration measurement techniques are available, each with its own associated advantages and shortcomings. In general, on-blade sensor measurement techniques suffer from sensor lifespan, whereas non-contact techniques usually have measurement bandwidth limitations. One non-contact measurement technique that yields improvements in the area of measurement bandwidth is laser Doppler vibrometry. This thesis presents results and findings from utilizing laser Doppler vibrometry in an Eulerian fashion (i.e. a fixed reference frame) to measure on-line blade vibrations in axial-flow turbomachinery. With this measurement approach, the laser beam is focussed at a fixed point in space and measurements are available for the periods during which each blade sweeps through the beam. The characteristics of the measurement technique are studied analytically with an Euler-Bernoulli cantilever beam and experimental verification is performed. An approach for the numerical simulation of the measurement technique is then presented. Associated with the presented measurement technique are the short periods during which each blade is exposed to the laser beam. This characteristic yields traditional frequency domain signal processing techniques unsuitable for providing useful blade health indicators. To obtain frequency domain information from such short signals, it is necessary to employ non-standard signal processing techniques such as non-harmonic Fourier analysis. Results from experimental testing on a single-blade test rotor at a single rotor speed are presented in the form of phase angle trends obtained with non-harmonic Fourier analysis. Considering the maximum of absolute unwrapped phase angle trends around various reference frequencies, good indicators of blade health deterioration were obtained. These indicators were verified numerically. To extend the application of this condition monitoring approach, measurements were repeated on a five-blade test rotor at four different rotor speeds. Various damage cases were considered as well as different ELDV measurement positions. Using statistical parameters of the abovementioned indicators as well as time domain parameters, it is shown that with this condition monitoring approach, blade damage can successfully be identified and quantified with the aid of artificial neural networks.
Thesis (PhD)--University of Pretoria, 2010.
Mechanical and Aeronautical Engineering
unrestricted

Conventionally the size of the back clearance played a great importance on reducing the axial clearance by utilizing the concept that the decreased axial clearance results in lower axial force acting on the impeller. However, from the previous works on the effect of the back clearance on the hydrodynamic forces upon the semi-open impeller showed the opposite trend: increasing the back clearance results in the reduced axial loading. In this work, the CFD simulation of an entire pump and detailed analysis on the back clearance flow are performed. By utilizing the commercially available software, meshing and CFD simulations are performed. LDA data, unsteady pressure data, and pressure distributions on the housing are used to validate the CFD model. The flow field prediction of the back clearance flow is then compared with other researcher’s works of the gap flow analysis between the rotating and stationary disks. The flow field inside the impeller passage, which is very sensitive to the back clearance size, is also studied. The empirical equation for the leakage loss through the balance holes is produced using the CFD predictions.