Browsing by Subject "Diffuser"
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Item Assessment of Flow Efficiency Through a Closed Circuit Wind Tunnel with Recommendations for Improvements(2013-12-02) Guthery, JohnWind tunnels are designed for a certain range of test velocities and model sizes. The Oran W. Nicks Low Speed Wind Tunnel (LSWT) at Texas A&M, was designed to reach 200 mph (M=0.26) with its original 1250 hp motor and 7 x 10 ft test section. In 2012 the motor and main bearing were replaced with a new 3000 hp motor. With the increased power and motor efficiencies, the tunnel could potentially reach M=0.42 flow. However, the current structure still limits the testing speed to M=0.26. This thesis outlines modifications that may allow the LSWT to reach M=0.5 for testing and potentially M=0.8 for an empty test section. The flow throughout the circuit and concomitant losses will be investigated. Methods for improving the efficiency will be presented, along with their estimated reduction in power loss. In order to reach this higher velocity, a 6 x 5 ft reduced test section with higher structural strength is required. This reduction in test section size requires subsequent diffuser and contraction alterations. The method for designing the diffuser will be presented, along with the design chosen. With these modifications to the tunnel, as well as using estimations of the motor efficiency, and results from measured and estimated losses in the circuit, the testing speed of M=0.5 in an empty test section could be reached with 1,200 to 1,800 hp supplied to the motor.Item Experimental investigation of the performance of a fully cooled gas turbine vane with and without mainstream flow and experimental analysis supporting the redesign of a wind tunnel test section(2013-12) Mosberg, Noah Avram; Bogard, David G.This study focused on experimentally determining the cooling performance of a fully cooled, scaled-up model of a C3X turbine vane. The primary objective was to determine the differences in overall effectiveness in the presence and absence of a hot mainstream flowing over the vane. Overall effectiveness was measured using a thermally scaled matched Biot number vane with an impingement plate providing the internal cooling. This is the first study focused on investigating the effect of removing the mainstream flow and comparing the contour and laterally-averaged effectiveness data in support of the development of an assembly line thermal testing method. It was found that the proposed method of factory floor testing of turbine component cooling performance did not provide comparable information to traditional overall effectiveness test methods. A second experiment was performed in which the effect of altering the angle of attack of a flow into a passive turbulence generator was investigated. Measurements in the approach flow were taken using a single wire hot-wire anemometer. This study was the first to investigate the effects such a setup would have on fluctuating flow quantitates such as turbulence intensity and integral length scale rather than simply the mean quantities. It was found that both the downstream turbulence intensity and the turbulence integral length scale increase monotonically with approach flow incidence angle at a specified distance downstream of the turbulence generator.Item Prediction of Room Air Diffusion for Reduced Diffuser Flow Rates(2011-02-22) Gangisetti, KavitaWith the ever-increasing availability of high performance computing facilities, numerical simulation through Computational Fluid Dynamics (CFD) is increasingly used to predict the room air distribution. CFD is becoming an important design and analytical tool for investigating ventilation inside the system and thus to increase thermal comfort and improve indoor air quality. The room air supply diffuser flow rates can be reduced for less loading with the help of a variable air volume unit. The reduction in supply flow rate reduces the energy consumption for the unoccupied and reduced load conditions. The present research is to study the comfort consequences for reduced diffuser flow rates and loading and to identify the hot and cold spots inside a room. A small office room with ceiling based room air distribution method is considered for CFD analysis. The CFD results are validated with experimental measured data for the designed diffuser flow rate. A parametric study on different turbulence models, namely, low Reynolds number modification of standard k-epsilon model, re-normalization group k-epsilon model, transition k-kl-w model and Reynolds stress model is carried out, and simulation results in terms of velocity and temperature profiles are compared against the measured data. Other important parameters such as diffuser jet inlet angle and radiation effect are also considered on the benchmark case to validate the results and to recommend the best fit parameters for room air simulations. Analysis has been carried out for a range of flow rates and heat loads. The jet momentum, draft and temperature distribution inside the room are studied for the impact of reduced flow rates and loading. The thermal comfort is quantified in terms of vertical temperature distribution and percentage dissatisfied index. From the research it is found that, for the studied room setup and air distribution method, the diffuser flow rate can be reduced up to 30 percent of the design flow rate, without experiencing a considerable effect on the room air temperature distribution. Also, based on thermal comfort and room air temperature distribution, several recommendations for occupant spacing in a room are suggested for reduced diffuser flow rates.