Browsing by Subject "inlet"
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Item Active flow control in an advanced serpentine jet engine inlet duct(2009-05-15) Kirk, Aaron MichaelAn experimental investigation was performed to understand the development and suppression of the secondary flow structures within a compact, serpentine jet engine inlet duct. By employing a variety of flow diagnostic techniques, the formation of a pair of counter-rotating vortices was revealed. A modular fluidic actuator system that would apply several different methods of flow control was then designed and manufactured to improve duct performance. At the two bends of the inlet, conformal flow control devices were installed to deliver varying degrees of boundary layer suction, suction and steady fluid injection, and suction and oscillatory injection. Testing showed that suction alone could delay flow separation and improve the pressure recovery of the duct by as much as 70%. However, this technique was not able to rid the duct completely of the nonuniformities that exist at the engine face plane. Suction with steady blowing, however, increased pressure recovery by 37% and reduced distortion by 41% at the engine face. Suction with pulsed injection had the least degree of success in suppressing the secondary flow structures, with improvements in pressure recovery of only 16.5% and a detrimental impact on distortion. The potential for gains in the aerodynamic efficiency of serpentine inlets by active flow control was demonstrated in this study.Item Degree of mixing downstream of rectangular bends and design of an inlet for ambient aerosol(Texas A&M University, 2006-04-12) Seo, YoungjinTests were conducted to characterize mixing in a square and a rectangular duct with respect to suitability for single point sampling of contaminants. Several configurations, such as a straight duct with unidirectional flow at the entrance section and straight ducts preceded by mixing elements (a 90?? mitred bend, double 90?? bends in S- and U-type configurations) were tested. For a straight duct of square cross section, the COV of tracer gas concentration at 19 duct diameters downstream of the gas release location is 143% (Center release). COVs of velocity and tracer gas concentration downstream of each mixing element in square duct setups were verified throughout this study. In the case of a rectangular duct with a 3:1 (width to height) aspect ratio, COVs of velocity and tracer gas concentration only downstream of a 90?? mitred bend were verified. Tests were conducted to develop improved inlets for a Battelle bioaerosol sampling system. New inlets have been developed called the All Weather Inlets (AWI), which are designed to prevent entry of precipitation while maintaining aerosol penetration. The AWI has two inlets - one that samples at a flow rate of 780 L/min and the other one that is operated at a flow rate of 90 L/min. The initial version of the AWI-780 L/min unit featured an internal cone, which was removed because the penetration of the AWI-780 without the bottom chamber was higher than that of the Battelle inlet ?? 81% with the cone while 86% without the cone for around 9.5 ??m AD at 2 km/h. The best bug-screen configuration was verified and a cutpoint management process was performed. The inlets were tested with different wind speeds from 2 to 24 km/h to verify the wind sensitivity of those inlets.Item Expanding the operational envelope of compact cylindrical cyclone gas/liquid separators using a variable inlet-slot configuration(Texas A&M University, 2006-04-12) Uvwo, IghofasanDespite the numerous advantages associated with using compact cylindrical cyclone gas/liquid separators, particularly for upstream production operations, the lack of a full understanding of the complex hydrodynamic process taking place in it and its ??unfamiliarity?? to oil field personnel has hindered its widespread use. The complexity associated with this technology is attributed to two limiting physical phenomena, liquid carry-over and gas carryunder. While a lot of work has been done to better understand and predict the liquid carry-over operational envelope, little or no information about methods capable of adequately predicting or characterizing the gas carry-under performance of such separators is available. Traditionally, to mitigate the gas carry-under phenomena, the use of complex control algorithms and systems has been employed. These systems make the technology expensive (as opposed to the potential cost reduction it promises) and impractical for realistic use in the oil field where reliability is of critical importance. A simpler solution, the use of changeable or adjustable inlet-slots that regulate the artificial gravity environment created in the separator, could significantly improve the gas carry-under performance of cylindrical cyclone separators. This research has focused primarily on the use of adjustable inlet-slots. Theoretical analysis and experimental data investigating the benefits of variable inlet geometry have been provided. This work lays the foundation or validation required to perform more tests on a field-scale version to verify the results presented here. A modular design of such a variable inlet-slot inletsection has the potential of simplifying the design and specifications of cylindrical cyclone gas/liquid separators. From the results of this investigation, it was found that the gas carry-under performance of a cylindrical cyclone gas/liquid separator could be improved considerably over a wider range of operating conditions by adjusting the size of the inlet-slots. This contradicts earlier reports of liquid carry-over improvement in separator performance. Also, for the first time, a simple method for theoretically analyzing the percent improvement in separator gas carry-under performance using the optimum g-force concept is presented. This method could be incorporated into design software for determining the slot-size configuration required for varying separator-operating conditions.Item Laboratory studies of eddy structures and exchange processes through tidal inlets(2009-06-02) Nicolau del Roure, FranciscoThe exchange flow through tidal inlets generates two-dimensional large coherent vortical structures (2DLCS), that are much broader than the water depth and exist because of the inherent instability of shallow shear flows. These vortical starting jets are critical to the mixing that occurs in the inlet area. Depending on the tidal period T, the width of the inlet W, and the maximum velocity in the inlet UMAX, the mixing will vary from poor exchange to efficient exchange. Here, we present laboratory and numerical experiments that study the formation of the 2DLCS at the mouth of the inlets. Experiments were conducted at large scale, in the shallow flat-bottomed water basin at the Institute of Hydromechanics of the University of Karlsruhe, Germany, which has the capability to generate a sinusoidal flow that simulates a series of tidal cycles. A set of idealized inlets were arranged in the tank, and by varying the tidal period and the maximum velocity, three different types of life-history were obtained (stationary dipole, dipole entrains, and dipole escapes). These types of life-history are defined by the mixing number depending if KW is equal, less or greater than a critical value. The experiments were visualized using color dye tracers. To quantify the shallow water velocity field, the Particle Image Velocimetry (PIV) technique was used. From the PIV data the vorticity field was obtained, and the regions where the vortex formed were identified. Then, a vortex time-evolution analysis was developed using iv physical parameters such as the position on the basin of the vortex, the equivalent diameter, and the maximum vorticity among others. The mixing number accurately predicts the behavior of the vortex for the first cycle on idealized inlets for the subsequent cycles; the structures behave differently than predicted by KW, because the blocking effect of the vortex /formed in the previous cycle. For characteristic times t* ? tUWless than about 2, the dipole is attached to the inlet and forms rapidly. For later times, the dipole advects downstream, and slowly dissipates. Numerical experiments are also presented. Comparing the numerical data with the laboratory data, good agreement is reached, but important limitations are identified for the grid resolution and domain size.Item Numerical Simulation of Flow and Heat Transfer in Internal Multi-Pass Cooling Channel within Gas Turbine Blade(2012-11-16) Chu, Hung-Chieh 1979-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.