Test results from a rocket turbine test model, called the Oxidizer Technology Turbine Rig (OTTR), are discussed in this paper. The turbine was designed to support the development of advanced turbines for future liquid rocket engines. It is a highly loaded single stage liquid oxygen pump drive turbine which uses inlet and exit volutes to provide optimum performance in a compact configuration. The system design creates high pressure and temperature gradients as well as high Mach number flow. These factors make it especially difficult to accurately measure the flowfield. Test issues such as probe calibration; probe interference, rake blockage, and averaging techniques were discussed in a previous paper. Test results including inlet volute, exit volute (both circular and square), and diffuser static pressure distributions, stator airfoil static pressure distributions, total and static pressure drops through the system, and overall performance parameters at the turbine aerodynamic design point and off-design point are presented here. This thesis will mainly focus on the information of both aerodynamic design point and off-design point of inlet volute, exit volute and diffuser for both circular exit volute and square exit volute.

The prediction of shut-off head within a centrifugal pump or fan has historically relied on the use of a combination of empirical formulae, together with experience. This reliance has been forced on designers due to both a lack of information regarding the flow at shut-off and the available tools with which to gain more accurate insights. To improve understanding the following investigation examines the capability of the commercial CFD package, FLUENT, to model the flow in a centrifugal pump at shut-off conditions. The computational model was validated using experimental measurements from a purpose built two-dimensional centrifugal pump rig. The rig used air as the working fluid and was similar in design to that used by Miner. Measurements were made of both the fluctuating velocities, using LDA, and the fluctuating pressures, using microphones, within the volute of the pump. The CFD model uses a sliding mesh which enables the full time-dependent rotor/stator interaction of the pump to be modelled. The results show the volute flow contains two patterns, a recirculating eddy in the outlet duct and a volute flow circulating around the rotor. This volute flow separates partway around the volute, with re-attachment on the discharge side of the tongue. The major effect of the volute at shut-off is to act as a diffuser with a strong circumferential pressure gradient over approximately the first 1200 after the tongue. A comparison of the experimental and computational results showed that good qualitative agreement was obtained at most positions at shut-off and considerable insight was gained into the flow mechanisms. However, the results showed that the CFD model over predicted the measured shut-off head by 25%. This was attributed to an over prediction of the effective viscosity due to the use of the k-s turbulence model.

This report is the documentation of a master’s thesis which was conducted at Scania CV AB in Södertälje. In this study, the benefits, challenges and conditions of using parametric CAD-models for aiding CFD-simulations and performance-optimization in the product development within internal combustion engines have been assessed. The goal of the thesis included developing and proposing a methodology for design engineers at Scania which will aid them in creating parametric CAD-models which are robust, flexible, comprehensible and intelligent. The study also included assessing the benefits and pre-requisites of such methodology with both practical and theoretical approaches. The ultimate goal of this entire study was to create value for the organization by reducing lead-time in the design process while promoting the production of high quality products. A case-based approach was applied in the study in which modeling strategies resulting from practical investigations and analyzing existing methodologies were implemented on a CAD-model representing the gas-volume of a turbine volute. The chosen strategies were evaluated and subsequently documented as a part of the methodology or discarded depending on its support for the parameterization. The final methodology itself was evaluated based on the quality of the parameterized CAD-model, the time required to create the model and its compatibility to the present design process at Scania CV AB. Finally the methodology was discussed with respect to the different evaluations, and the defined research questions were discussed and answered. The results of the thesis revealed that if parametric CAD-models are made in a structured, standardized and conscious manner, they are able to be highly robust and flexible which gives the models the ability to assume a big set of different forms. The methodology is recommended to be tested in a pilot project and be implemented through internal courses at the company. It was concluded that a methodology which aids the design engineers in creating parametric CAD-models will be the key towards implementing parametric CAD-models in the company and also enabling the many benefits of parameterization, which includes reduced lead-time, enhanced component performance, increased knowledge about the component, and promotion of collaboration among engineers. It was also concluded that parametric models are best suited when the existing design freedom is big and when the time permits performance analyses via optimizations, while challenges include ensuring that the model is parameterized correctly with respect to the CFD-engineers’ wishes while taking into account the requirements from other disciplines. Therefore it is very important to establish a communication between the different engineers. Ultimately, when parametric models are established in the organization, they are recommended to be implemented eventually in both short-term and long-term projects within Scania for its beneficial properties.

The interior flowfield analysis of fan has been considered to be one of the most difficult problems in the past. With the advent of computational fluid dynamics (CFD) methods, many flow problems inside the fan can now be solved with a good degree of accuracy. ¡@ A numerical study of the influence of inlet cone and volute cutoff on a centrifugal fan performance is presented in this work. Using the flow-visualization simulating analysis of the flow-flied characteristic of air across the inner of centrifugal fan, the performance curve with different inlet cone shape, inlet clearance gap, cone position, extending angle and curvature radius of cutoff arc were obtained and explored. The Reynolds-Averaged Navier- Stokes equations with the Standard k-£` turbulence model is used to simulate the three-dimensional, steady, incompressible, turbulent flow field inside a double-suction backward-curved centrifugal fan and is solved by control volume method. The numerical model is validated by experimental data. The results showed that (i) the inlet cone can induce the air to enter into the impeller smoothly and uniformly, which reduces the flow-separation occurrence along the blade surface. However, the inlet cone with larger friction loss will also slightly lessen the fan performance; (ii) recirculation zones appear inside the volute channel due to the existence of inlet clearance gap between inlet cone and volute, which results in part of fluid leaving from the impeller outlet re-entering into the impeller inlet and reducing the fan performance. This recirculation leakage ratio of fluid through inlet clearance gap increases with increasing inlet clearance gap, which is also depends on the shape of inlet cone; (ii) the distance of inlet cone extending into the impeller will interfere the uniformity of inlet airflow distribution along each blade height. The longer the extending distance, the larger the vortex zone occupying the inter-blade space which makes less fan performance; (iv) it makes only little improvement in the fan performance to change the shape of volute cutoff. ¡@ It is found that (1) decreasing the inlet clearance from 11mm to 5mm, the outlet average total pressure increases about 3.26%; (2) increasing the distance of inlet cone extending into the impeller from 0mm from 20mm, the outlet average total pressure decreases about 6.32%; (3)changing the shape of inlet cone, the outlet average total pressure increases up to 5.4%, and (4) reducing the tongue radius of volute cutoff from 25mm to 15mm, the performance efficiency of fan promotes slightly about 1%.

One elementary part of a centrifugal compressor is the volute, which is located downstream the impeller. Its purpose is to collect the flow and increase the static pressure by converting kinetic energy into potential energy. Despite its significant effect onto the design point and operating range of the compressor, the number of publications regarding this component is quite small. Therefore, a numerical optimization of the volute housing is performed in order to identify important geometric parameters and find an optimal volute geometry. For this purpose, a new density-based CFD solver for all Mach numbers is developed as well as an automated geometry generation tool for the volute housing. The results show, that a volute with an inlet eccentricity of 0.9 and a slightly lower radial volute channel offers the best compressor efficiency. Moreover, the actual cross-sectional shape of the volute has only a minor influence onto the performance. As a result, the isentropic efficiency could be improved by up to 2 % compared to the reference compressor model, in particular at high off-design flow rates. These results are a novelty in the scientific community and help to design more efficient compressors. / Das Spiralgehäuse eines Radialverdichters wird im Gegensatz zum Laufrad kaum in wissenschaftlichen Arbeiten untersucht. Um wichtige Geometrieparameter und Einflussfaktoren dieses Bauteils zu identifizieren, wird daher eine Optimierung mittels genetischer Algorithmen durchgeführt. Dazu wird zunächst ein dichte-basierter CFD-Löser entwickelt und validiert, um die komplexe Strömung in einem Radialverdichter mit hoher Genauigkeit simulieren zu können. Darauf aufbauend wird das Spiralgehäuse parametrisiert und ein Programm entwickelt, welches die komplexe Geometrie automatisiert erstellt. Durch die neuartige Kombination von numerischer Optimierung, automatisierter Geometrieerstellung und CFD-Simulation des Spiralgehäuses können erstmals Aussagen zur optimalen Geometrie sowie über Verlusteffekte für eine Vielzahl an Geomtrievarianten getroffen werden. Mit Hilfe dieses Wissens können sparsamere und effizientere Radialkompressoren für viele Bereiche des Maschinenbaus entwickelt werden.

Čerpadla s nízkými specifickými otáčkami nacházejí uplatnění v široké škále aplikací, ale trpí nízkou účinností a rizikem nestability křivky dopravní výšky. Tato disertační práce pojednává o vylepšení hydraulických parametrů čerpadla se specifickými otáčkami ns = 32. Práce se zaměřuje na průtok v oběžném kole a ve spirále, které jsou řešeny pomocí CFD. Průzkum literatury ukázal, že přidání mezilopatek do průtokového kanálu je účinný způsob, jak zlepšit neuspokojivé proudění obecně přítomné v oběžných kolech s nízkými specifickými otáčkami. Byla zkoumána poloha mezilopatky v kanálu a vliv počtu přítomných mezilopatek. Část výsledků je ověřena experimentálně v laboratoři fakulty. Rovněž je zkoumán tvar spirály a pozornost je věnována numerickému řešení proudění u stěn a jeho vlivu na simulaci. Po numerických výpočtech na třech různých spirálách je navržen nový tvar, který zlepšuje vypočtové parametry čerpadla při nízkém i vysokém průtoku.

L'utilisation des pompes centrifuges à volute joue un rôle important dans divers secteurs de l'industrie en général. Parmi eux on peut mentionner l'automobile, la construction des installations navales, etc. Elles sont couramment employées par leurs prestations concernant leurs performances globales et leur comportement hydroacoustique. Il est bien connu que le comportement du fluide interne est caractérisé par des fortes interactions entre les parties mobiles et fixes qui sont à l'origine du bruit et des vibrations. Dans les cas des pompes centrifuges, le bruit se caractérise particulièrement à la fréquence aubage dû à l'interaction hydrodynamique entre la roue et le bec de volute. L'intensité de cette excitation, qui dépend de la géométrie et des conditions de fonctionnement, peut être nuisible dans certaines conditions et exigences. Les travaux de recherche effectués nous ont permis de contribuer à l'analyse et à la maîtrise des fluctuations de pression dans les pompes centrifuges grâce aux apports conjugués de simulations numériques et d'études expérimentales spécifiques. Une procédure numérique de prédiction du bruit tonal à la fréquence aubage est développée et validée par comparaison aux essais expérimentaux. En outre, l'amélioration des algorithmes numériques ainsi que le développement du matériel informatique ont permis l'émergence de codes de simulation d'écoulements plus avancés. Cependant, étant donné les exigences de précision pour prédire les fluctuations de pression et la difficulté des codes commerciaux d'atteindre des schémas d'ordre élevé nous mènent à développer notre propre code. Ce nouveau code (FV-MLS) plus précis, basé sur la méthode de volumes finis et les approximations de moindres carrés mobiles (Moving Least Squares - MLS), est couplé avec la technique de maillage glissant pour être appliqué dans une configuration 2D d'une pompe centrifuge.

For air cooling in aircrafts is used an air cycle machine. Recently, there is focusing on incresing efficiency of air cycle and due this are added another rotors. Design of machine with three rotors is performed in this thesis.

One elementary part of a centrifugal compressor is the volute, which is located downstream the impeller. Its purpose is to collect the flow and increase the static pressure by converting kinetic energy into potential energy. Despite its significant effect onto the design point and operating range of the compressor, the number of publications regarding this component is quite small. Therefore, a numerical optimization of the volute housing is performed in order to identify important geometric parameters and find an optimal volute geometry. For this purpose, a new density-based CFD solver for all Mach numbers is developed as well as an automated geometry generation tool for the volute housing. The results show, that a volute with an inlet eccentricity of 0.9 and a slightly lower radial volute channel offers the best compressor efficiency. Moreover, the actual cross-sectional shape of the volute has only a minor influence onto the performance. As a result, the isentropic efficiency could be improved by up to 2 % compared to the reference compressor model, in particular at high off-design flow rates. These results are a novelty in the scientific community and help to design more efficient compressors. / Das Spiralgehäuse eines Radialverdichters wird im Gegensatz zum Laufrad kaum in wissenschaftlichen Arbeiten untersucht. Um wichtige Geometrieparameter und Einflussfaktoren dieses Bauteils zu identifizieren, wird daher eine Optimierung mittels genetischer Algorithmen durchgeführt. Dazu wird zunächst ein dichte-basierter CFD-Löser entwickelt und validiert, um die komplexe Strömung in einem Radialverdichter mit hoher Genauigkeit simulieren zu können. Darauf aufbauend wird das Spiralgehäuse parametrisiert und ein Programm entwickelt, welches die komplexe Geometrie automatisiert erstellt. Durch die neuartige Kombination von numerischer Optimierung, automatisierter Geometrieerstellung und CFD-Simulation des Spiralgehäuses können erstmals Aussagen zur optimalen Geometrie sowie über Verlusteffekte für eine Vielzahl an Geomtrievarianten getroffen werden. Mit Hilfe dieses Wissens können sparsamere und effizientere Radialkompressoren für viele Bereiche des Maschinenbaus entwickelt werden.

This thesis is focused on design of the turbine housing CAD model applicable for mixed flow turbine. It also deals with strength analysis of designed turbine housing. The aim of the thesis is to create a three-dimensional turbine housing model accompanied by drawings.