Orientador: José Luiz Gasche / Banca: André Luiz Seixlack / Banca: Odenir de Almeida / Resumo: O presente trabalho refere-se à investigação experimental e numérica do escoamento em difusores radiais, que são usados como modelos de representação de sistemas de válvulas de compressores de refrigeração. Uma bancada experimental é projetada, construída e validada para medir a distribuição de pressão, sobre o disco frontal de um difusor radial de razão de diâmetro 3, para números de Reynolds de 1500 a 9000 e afastamento entre os discos frontal e anterior variando de 0,415mm a 0,705mm aproximadamente. Paralelamente, desenvolve-se um código computacional, baseado na metodologia de Volumes Finitos para malhas desencontradas, para simular o escoamento na geometria do difusor radial. O código computacional é primeiramente validado por meio dos resultados experimentais obtidos da bancada construída. Após sua validação, o código é usado para analisar o escoamento em um difusor de razão de diâmetro igual a 1,4, para números de Reynolds variando de 500 a 2500 e afastamento entre discos na fixa de 0,125 a 1,0mm. Os resultados numéricos mostram o surgimento de recirculação extendendo-se em toda região do difusor. Além disso, os resultados de perfil de pressão sobre o disco frontal fornecem forças e quedas totais de pressão no difusor que aumentam com o número de Reynolds e afastamento entre disco. Esse comportamento produz um ponto de mínima área efetiva de força localizado na faixa de , para números de Reynolds variando de 500 a 1500. Para número de Reynolds mais elevados, , a área efetiva de força sempre aumenta com o aumento do afastamento entre discos. A área efetiva de escoamento, outro parâmetro de interesse para a simulação do compressor, apresenta um crescimento linear com o afastamento entre discos, independentemente do número de Reynolds avaliado. / Abstract: In this work, an experimental and numerical investigation of the flow in radial diffusers representing the valve system of refrigeration compressor is accomplished. An experimental bench is designed, build, and validated allowing the measurement of the pressure distribution on the frontal disk surface of a radial diffuser with diameter ratio equal to 3, for Reynolds number varying from 1500 to 9000 and distances between disks in the ranges of 0.415 to 0.705mm. In addition, a computational code based on the Finite Volume Methodology for staggered mesh is developed in order to simulate the flow though the radial diffuser. The computational code is firstly validated by using the experimental data obtained from the experimental bench. After its validation, the code is used for analyzing the flow through a radial diffuser with diameter ratio equal to 1.4, for Reynolds numbers varying from 500 to 2500 and distance between disks in the range of 0.125 a 1.0 mm. The numerical results showed recirculation regions extending through the whole diffuser for the majority of the analyzed cases. The pressure profiles on the frontal disk surface produce forces and total pressure drops through the diffuser that increase with both Reynolds number and distance between disks. There is a minimum effective force area in the range of , for Reynolds numbers varying from 500 a 1500. For higher Reynolds numbers, , the effective force area always increases for increasing distance between disks. The effective flow area, another parameter used for simulating the compressor, increases linearly with the distance between disks, independently of the Reynolds number. / Mestre

This master thesis is focused on the issue of air distribution in residential buildings. The main part of thesis is devoted to experimental testing of diffusers by a smoke test. Achieved results are applied to design of air conditioning in passive house. Radiant heating and energy optimalization in PHPP are also proposed.

This diploma thesis is considering with computational modeling of flow field with separation. In the first part it contains theoretical bases of flow field computational modeling with RANS models equations and wall treatment modeling approaches included. There is also flow separation in asymmetric plane diffuser modeling described in the thesis where the most suitable turbulent model and the proper mesh parameters for the successful flow separation modeling should be chosen. Next the chosen turbulent model and parameters verification via flow separation modeling on the asymmetric 3D diffuser mesh. That analysis should ensure if the chosen turbulent model is applicable also for engineering problems. At the end of the thesis there is evaluation if the setup chosen in the thesis is suitable to apply in any practical aeroacoustics problem modeling.

The diploma thesis deals with the design of air-conditioning equipment in the building of a multifunctional hall in Brno and also includes an experimental analysis of air flow. It consists of 3 parts. In the first part a theory of air distribution is elaborated. The second part deals with the analysis of air flow for different types of air diffusers and for one diffuser further looks for a simplified model. The last part of this work is focused on the design of air conditioning equipment in the assigned building, the multifunctional sports hall.

My thesis is engaged in description of ineligibility original version of the elbow draft tube new constructed small hydro power plant Doudlevce. Other main purpose was construction of better hydraulic thus more efficient this draft tube. First chapter meets project small hydro power plant Doudlevce and it specifies this interesting contstruction of the power plant (for example position of the turbine in vacuum fontain) and many others information about it. Second chapter and its particular parts there deal with functions of this draft tube, for example out-flow of water from turbine and a principle of water-energy utilization placing behind turbine runner. There is also described energy profit and how to get it throught draft tube. There is an analysis of important quantities, which are used during the scoring of flow in the draft tube in third chapter. This part of my thesis is aimed to meeting their principles. There is one of the main purposes of this thesis, where is a description of ineligibility original version of the elbow draft tube in fourth chapter. It results sizable from Kaplan´s attemps and analysis of flowing based on computations in computer programme CFD Fluent. Fifth chapter is about general principles, which should be looked out during the construction of the draft tube. There is also project of new hydraulic better draft tube and its another parts. Last chapter compares original version with new better project based on computations in computer programme CFD Fluent. Comparison is made of specific criterion flowing of water, where are described quantites in third chapter, and efficiency of this draft tube.

This doctoral thesis studies the non-uniform blade cascade for centrifugal pumps. Influence of non-uniform blade cascade is investigated on the impeller and diffuser. A non-uniform blading impeller of pumps in this doctoral thesis was examined in terms of influence on efficiency characteristic. The idea of using non-uniform blading is to obtain a flat efficiency characteristic. Then the centrifugal pump could be used on larger scale of power with achieving a sufficiently high efficiency. The work is based on experimental measurements and numerical simulations of non-uniform hydraulic pump components. Non-uniform impeller and the diffuser were newly designed for this research. A new measuring track of small submersible pumps was needed to design and build for measurements. Different pump combinations with conventional hydraulics on one working point and hydraulics with non-uniform were measured. All measurements were evaluated and characteristics of efficiency, head and power were obtained for each measured combination. Some of pump combinations (which were measured in experiment) were numerically simulated by program Ansys Fluent. Data needed to evaluate the characteristic of efficiency and specific energy were collected from each numerical simulation. A theoretical consideration concerns the influence of non-uniform blade cascade applied on diffuser. The suggestion how to decrease hydraulic losses in canals was done. The theoretical consideration how to make a flat efficiency characteristic was made.

Many flow cases in fluid dynamics face undesirable flow separation due torising static pressure on wall boundaries. This occurs e.g. due to geometry as ina highly curved turbine inlet duct or e.g. on flow control surfaces such as wingtrailing edge flaps within a certain angle of attack range. Here, flow controldevices are often used in order to enhance the flow and delay or even totallyeliminate flow separation. Flow control can e.g. be achieved by using passiveor active vortex generators (VG) that enable momentum mixing in such flows.This thesis focusses on passive VGs, represented by VG vanes that are mountedupright on the surface in wall-bounded flows. They typically have an angle ofincidence to the mean flow and, by that, generate vortex structures that in turnallow for the desired momentum mixing in order to prevent flow separation.A statistical VG model approach, developed by KTH Stockholm and FOI,the Swedish Defence Research Agency, has been evaluated computationally.Such a statistical VG model approach removes the need to build fully resolvedthree-dimensional geometries of VGs in a computational fluid dynamics mesh.Usually, the generation of these fully resolved geometries is rather costly interms of preprocessing and computations. By applying this VG model, thecosts reduce to computations without VG effects included. Nevertheless, theVG model needs to be set up in order to define the modelled VG geometry inan easy and fast preprocessing step. The presented model has shown sensitivityfor parameter variations such as the modelled VG geometry and the VG modellocation in wall-bounded zero pressure gradient and adverse pressure gradientflows on a flat plate, in a diffuser, and on an airfoil with its high-lift systemextracted. It could be proven that the VG model qualitatively describes correcttrends and tendencies for these different applications.

No description available.

This study aimed to explore the integration of varying angles in small-scale measurements and assess the light transmission performance of uncoated curtains. A total of four curtains were evaluated: blackout curtain samples 1 and 2 had a weft satin structure, while daytime curtain samples 3 and 4 consisted of a twill structure. The primary challenge was the inadequacy of a standardized test method for measuring the blackout effect, which led to inefficiencies and resource consumption for Company X. To address this, the study emphasized the need to investigate and establish a reliable and efficient evaluation method for uncoated curtains. By developing a standardized test method, it is possible to reduce waste material, labor costs, and resource consumption, enabling companies to operate more efficiently, sustainably, and responsibly. In the pursuit of understanding the blackout effect and evaluating the structural parameters of uncoated curtains, this study explored various test methods and parameters. More specifically, parameters such as air permeability, porosity, and thickness together with microscopic evaluation, were investigated to shed light on their influence on light transmission. The voids in the fabric were found to be a significant factor, along with porosity and air permeability, which demonstrated a correlation with lower values for the blackout curtains. The construction of the test method in a small-scale required a controlled space in the form of a lightbox. Light proofing of the box was required and successfully achieved in Prototype 1 using plywood, sealing strips, and fixtures, resulting in a lower lux value compared with the previous internal method. Objective measurements using the Konica CL-500A lux meter provided a repeatable and reliable test method with a lower tolerance value of 0,05 lx. The developed test method, theoretical Prototype 2, incorporates different sun angles by adjusting the curtain’s position, in the angles of 0°, 15°, 30°, 45° and 60°, and the rotation of the sample within 0° to 360° in intervals of 45°. The important parameters of weft density and the subsequent increase in weight were key factors in the results of light transmission, air permeability, and porosity. Furthermore, properties of the uncoated curtains such of continuous filaments and darker color showed a higher blackout effect. After the identification of complications with the lamp used in the measurement, there has been a focus on discussing the significance of a light diffuser. Additionally, alternative approaches to measure light transmission have been presented, such as digital image analysis and air permeability.

<p dir="ltr">Increased scrutiny from customers and regulators to design aeroengines that are more efficient and environmentally friendly has pushed the need to investigate new engine architectures, manufacturing techniques, and computational fluid dynamic methods. This has led to the development of the CSTAR Gen. 2.5 centrifugal compressor, which uses an additively manufactured diffusion system and investigates the aerodynamic performance of an axi-centrifugal aeroengine. Additionally, an isolated unsteady diffuser computational model was previously developed that seeks to significantly reduce the computational cost of unsteady CFD in the diffuser.</p><p dir="ltr">The research presented in this paper is part of an ongoing attempt to utilize the capabilities of isolated unsteady diffuser modeling and rapid prototyping enabled through additive manufacturing in CSTAR Gen. 2.5 to develop a design framework that allows for quick computational and experimental analysis of diffusion systems in centrifugal compressors. Specifically, the scope of isolated unsteady diffuser modeling, which was previously only implemented in CSTAR Gen. 1 and at a single loading condition, is expanded by analyzing computational instabilities when applying the methodology to CSTAR Gen. 2.5 and analyzing results from four loading conditions (high loading, design point, low loading, and near choke) along a speedline.</p><p dir="ltr">Computational instabilities in the CSTAR Gen. 2.5 isolated diffuser models were determined to be caused by the decreased vaneless space compared to Gen. 1, which led to less “mixed” flow at the impeller outlet and a stronger diffuser potential field affecting the inlet profile. A boundary profile correction approach was developed which slightly increased very low total pressure near the diffuser shroud and negative radial velocity regions near the shroud and pitchwise locations of the diffuser vane leading edges while minimizing the overall affected area. The correction was successfully validated using 3D flow structure and minimum, average, and maximum total pressure, absolute velocity magnitude, and pressure comparisons at the diffuser inlet between an isolated and full-stage model.</p><p dir="ltr">Prediction capabilities of 3D flow structures and 1D performance parameters by isolated unsteady diffuser models were validated with results from full-stage unsteady models at each loading condition. The analysis indicated consistent performance by the isolated unsteady diffuser model at all loading conditions. An overall agreement in 3D flow structures was found, and trends in the full-stage unsteady models along the speedline were tracked well by the isolated unsteady model. At all loading conditions, there was a consistent over-representation of the separation region along the diffuser vane pressure side in the diffuser passage, overprediction of total pressure magnitude at the core of the flow at the diffuser outlet, and over- or underprediction of total pressure loss and static pressure recovery respectively. The similarity in the results between full-stage and isolated unsteady models, tracking of trends along the speedline, and consistent differences in 3D flow structure predictions and 1D performance parameters validates the isolated unsteady diffuser methodology for use at loading conditions from surge to choke.</p>