A series of experiments were carried out to measure the effects of convex surface curvature on film cooling. In the first series of experiments cooling holes were positioned along the vane such that their non-dimensional curvature parameter, 2r/d, was matched. Single row of holes with the same diameter were placed at high and moderate curvature position along a turbine vane resulting in 2r/d = 28 and 40, accordingly. A third row of holes was installed on the vane at the same location as the moderate curvature row with a larger hole diameter, resulting in 2r/d = 28, matching the high curvature row. Adiabatic temperature measurements were then carried out for blowing ratios of M = 0.30 to 1.60 tested at a density ratio of DR = 1.20. The results indicated that there was some scaling of performance present with matching 2r/d, but there was not an exact matching of performance. The second series of experiments focused on the effects of a changing surface curvature downstream of injection. Two row of holes were positioned along the vane surface such that the local radius of curvature and hole diameters were equivalent, with one row positioned upstream of the maximum curvature point and the other downstream of the maximum curvature point. Adiabatic temperature measurements were carried out for blowing ratios of M = 0.30 to 1.60 and tested at a density ratio of DR = 1.20. The results show that the change in curvature downstream plays a significant role in the performance of film cooling and that the local surface curvature is insufficient in capturing its effects. Additional experiments were carried out to measure the effects of the approaching boundary layer influence on film cooling as well as the effect of injection angle at a weakly convex surface. / text

This thesis presents the results of two 2-D computational studies of a circulation control Inlet Guide Vane (IGV) that takes advantage of the Coanda effect for flow vectoring. The IGV in this thesis is an uncambered airfoil that alters circulation around itself by means of a Coanda jet that exhausts along the IGV's trailing edge surface. The IGV is designed for an axial inlet flow at a Mach number of 0.54 and an exit flow angle of 11 degrees. These conditions were selected to match the operating conditions of the 90% span section of the IGV of the TESCOM compressor rig at the Compressor Aero Research Laboratory (CARL) located at Wright-Patterson AFB. Furthermore, using the nominal chord (length from leading edge of the IGV to the jet exit) for the length scale, the Reynolds number for the circulation control IGV in this region was 5e⁵. The first study was a code and turbulence model comparison, while the second study was an optimization study which determined optimal results for parameters that affected circulation around the IGV. Individual abstracts for the two studies are provided below. To determine the effect of different turbulence models on the prediction of turning angles from the circulation control IGV, the commercial code GASP was employed using three turbulence models. Furthermore, to show that the results from the optimization study were code independent a code comparison was completed between ADPAC and GASP using the Spalart-Allmaras turbulence model. Turbulence models employed by GASP included: two isotropic turbulence models, the one equation Spalart-Allmaras and the two-equation Wilcox 1998 k-ω. The isotropic models were then compared to the non-isotropic stress transport model Wilcox 1998 Stress-ω. The results show good comparison between turning angle trends and pressure loss trends for a range of blowing rates studied at a constant trailing edge radius size. When the three turbulence models are compared for a range of trailing edge radii, the models were in good agreement when the trailing edge is sufficiently large. However, at the smallest radius, isotropic models predict the greatest amount of circulation around the IGV that may be caused by the prediction of transonic flow above the Coanda surface. The optimization study employed the CFD code ADPAC in conjunction with the Spalart-Allmaras turbulence model to determine the optimal jet height, trailing edge radius, and supply pressure that would meet the design criteria of the TESCOM (TESt COMpressor) rig while minimizing the mass flow rate and pressure losses. The optimal geometry that was able to meet the design requirements had a jet height of h/C_n = 0.0057 and a trailing edge Radius R/C_n = 0.16. This geometry needed a jet to inflow total pressure ratio of 1.8 to meet the exit turning angle requirement. At this supply pressure ratio the mass flow rate required by the flow control system was 0.71 percent of the total mass flow rate through the engine. The optimal circulation control IGV had slightly lower pressure losses when compared to the cambered IGV in the TESCOM rig. / Master of Science

No description available.

This master thesis deals with design of compression part of Braysson engine which is instrumental to energy producing. The first part addresses generally the problem of Braysson cycle and briefly sums the knowledge about compressors. The next part focuses on the projection of design itself. It contains proposals of various possibilities of solutions, choice of optimal variants. Individual parts of the machine are described and design and control computations are provided. The final part contains evaluation.

Increasing the combustion temperatures in a gas turbine engine to achieve higher efficiency and power output also results in high heat loads to turbine components downstream of the combustor. The challenge of adequately cooling the nozzle guide vane directly downstream of the combustor is compounded by a complex vortical secondary flow at the junction of the endwall and the airfoil. This flow tends to increase local heat transfer rates and sweep coolant away from component surfaces, as well as decrease the turbine aerodynamic efficiency. Past research has shown that a large fillet at the endwall-airfoil junction can reduce or eliminate the secondary flow. Also, leakage flow from the interface gap between the combustor and the turbine can provide some cooling to the endwall. This study examines the individual and combined effects of a large fillet and realistic combustor-turbine interface gap leakage flow for a nozzle guide vane. The first study focuses on the effect of leakage flow from the interface gap on the endwall upstream of the vane. The second study addresses the influence of large fillets at the endwall-airfoil junction, with and without upstream leakage flow. Both studies were performed in a large low-speed wind tunnel with the same vane geometry. Endwall shear stress measurements were obtained for various endwall-airfoil junction geometries without upstream leakage flow. Endwall heat transfer and cooling effectiveness were measured for various leakage flow rates and leakage gap widths, with a variety of endwall-airfoil junction geometries. Results from these studies indicate that the secondary flow has a large influence on the coverage area of the leakage coolant. Increased leakage flow rates resulted in better cooling effectiveness and coverage, but also higher heat transfer rates. The two fillet geometries tested affected coolant coverage by displacing coolant around the base of the fillet, which could result in undesirably high gradients in endwall temperature. The addition of a large fillet to the endwall-airfoil junction, however, reduced heat transfer, even when upstream leakage flow was present. / Master of Science

This Masters Thesis describes the continuation of the Snow Probe development. The focus of this project was to establish the rotational shear vane as a useful tool in avalanche safety work as well as develop a robust method for measuring the applied torque. A new and novel way of measuring the torque on a rotational shear vane has been developed to illustrate its effectiveness. The new system measures the power supplied to a cordless drill to get an indication of the applied torque. This was done because it was found that the earlier method of using a strain gauge/cantilever system repeatedly failed to work, largely due to complexity. The snow probe in its present embodiment has been shown to provide a good clear indication of the snow profile under easily repeated circumstances. Shear strength results are at this stage not sufficiently for reliable quantitative results. However the probe in its present form is able to give pictorial impressions of the snow pack that compare well to current hand hardness profiles derived from snow pit methods. Even in its current form the snow probe is able to collect useful snow profile data in a matter of minutes, much quicker than conventional snow pit methods. A loose relationship was found to exist between the approach angle of a shear vane blade and the clarity of the snow profile. These relationships are relatively inaccurate at present due to lack of rotational velocity data and therefore pproach angle data. It is believed that the addition of a rotation counter would greatly increase the accuracy of the probe results and enable a shear strength profile to be quantified. Further developments and testing are underway with a view to forming a company around the snow probe.

This diploma thesis analyzes the effects of various parameters of vane profile and position of VNT mechanism on the size of aerodynamic force which acts on the vanes and on the position of neutral axis of the vane. A CDF simulation was created to do this analysis, and the results of the simulation were evaluated. Thesis also deals with turbochargers in general and with other methods of their regulation.

Instream structures are used to reinforce channel margins, redirect flows, and create habitat, but there is little consensus about their design or whether they function as intended. In this study, 536 instream structures in the state of Maryland were assessed to determine the effect of structure-, project-, and watershed-scale factors on performance. Structures were assessed using a 19 point scoring system based on structural stability, sediment transport, and overall function. Structure-scale variables related to the construction, geometry, and placement, and differed for six structure families: bank protection (BP), full and partial span vanes (FSV), constructed riffles (RF), regenerative stream conveyances, and step pools. Project- and watershed-scale variables related to flow, erosion resistance, and design approach. Relationships between structure scores and explanatory variables were evaluated using regression analysis. Structure performance was strongly influenced by the individual project, suggesting that design quality, construction, and maintenance are as important as specific design features. Structure durability decreased if there was additional urban development following construction. Results also indicated that restoration activities have a "protective effect" on nearby structures. For rock BP, imbricated rock walls performed better than stone toe, due to increased structure height and boulder size. Rock FSVs that were keyed into the bank at angles between 35° and 90° were more durable, while RFs performed best when constructed using downstream grade control and increased substrate depth. The results of this study provide insight into design and project features that contribute to structure success. / Master of Science / Stream restoration aims to rehabilitate streams that have been impacted by humans, and log or rock structures in the channel are utilized to protect the bed and banks, redirect water away from the banks, and create habitat for aquatic organisms. However, there are few design standards for these structures. In this study, 536 instream structures in the state of Maryland were assessed to determine the effect of design and site characteristics on performance. Structures were scored for performance based on structural stability, sedimentation, erosion, and function. Design characteristics related to structure construction and placement, while site conditions related to the project and watershed characteristics. Statistical analyses were used to determine the relationship between structure performance and design and site characteristics. Structure performance was strongly influenced by the restoration project, indicating that design quality, construction, and maintenance are as important as specific design features. Structure durability decreased if there was additional urban development in the watershed following construction. Results also indicated that when structures were used in series, there was a "protective effect" on other nearby structures. Rock walls performed better as height increased, while rock weirs that were constructed into the streambank between 35° and 90° were more durable. These results provide insight into design and project features that contribute to structure success.

Results from numerical simulation were performed to study flow and heat transfer in two types of rotating multi-pass cooling channels. Second moment closure model was used to solve flow in domain generated from Chimera method. The first type was a four-pass channel with two different inlet settings. The main flowing channel was rectangular channel (AR=2:1) with hydraulic diameter (Dh ) equals to 2/3 inch (16.9 mm). The first and fourth channel were set as different aspect ratio (AR=2:1; AR=1:1). Reynolds number (Re) used in this part was 10,000. The rotating angle was set as 90 degrees. The density ratio was set as 0.115. The rotation number varied from 0.0 to 0.22. It was showed that inlet effect only caused influence to flow and heat transfer in first two passages. The second type was a four-pass channel with/without addition of vane in smooth turn portion. The main flowing channel was rectangular channel (AR=2:1) with hydraulic diameter (Dh) equals to 2/3 inch. The first and fourth passages were set to be square duct (AR=1:1). The Reynolds number (Re) used in this part was 20,000. Three rotation numbers were set here (Ro=0.0; Ro=0.2; Ro=0.4). The density ratio and rotating angle varied from 0.12 to 0.32 and from 45 degrees to 90 degrees respectively. According to numerical results, it was revealed that the addition of vane in smooth turn portion did not cause influence to part before it. However, it caused significant influence to flow and heat transfer in smooth turn portion and part after it.

­^¤åºK­n In the wet wafer cleaning process, the wafer surfaces are washed with toxic solutions such as ammonia and sulfuric acid which was not to allow to enter the surroundings i.e. clean room. Therefore, common practice is to reduce the pressure differential between the wet bench and the surroundings to a very low pressure difference level while maintaining a high exhaust flow rate for toxic fumes. In such a case, the isolation of process area from the surrounding area may be compromised i.e. there is a danger that the surrounding air was suctioned to the process area. Conceptually, this dilemma can be solved by creating an air buffer between the wafer process area and the surrounding area. This study aims to determine/prove-in the optimal operational conditions and geometries of such design by both CFD analysis and experimental verification. This thesis includes three parts. First, the detailed experimental data to a bio-clean bench installed with the guide-vane design are conducted. The data are then used to verify the feasibility/accuracy of the CFD model. Second, the optimal operational conditions and geometries of a full-scale isothermal wet bench with the guide-vane design are determined by CFD simulation that takes most influential factors into account. These influential factors include exhaust pressures, length of the guide- vane, guide-vane angle and downward face velocity of the filter etc. The results show that the air curtain created by the guide-vane is able to isolate the process area from surrounding area, and vise-versa. Third, the thermal effect of ammonia solution on the distribution of ammonia vapor are examined. The shape of the thermal plume that encounters the downward air stream of the filter is discussed intensively. In general, this thesis provides significant information in improving the isolation effect of wet benches by the air-curtain design.