The purpose of the current study is to increase the understanding of different steelmaking processes at the decarburization stages by use of mathematical modeling. More specifically, two De-Laval nozzles from a VOD (Vaccum Oxygen Decarburization) process, which is used for producing stainless steels with ultra-low carbon grades, was investigated for different vessel pressures. Moreover, the post combustion phenomena in a BOF or LD (Linz-Donawitz) process as well as an AOD (Argon Oxygen Decarburization) process were studied focusing on the decarburization stage. Two industrial VOD nozzles were numerically studied and compared at different temperatures and ambient pressures. Flow patterns of the oxygen jet under different ambient pressures were predicted and the flow information at different positions from the nozzle was analyzed. In addition, the effects of different ambient temperatures on the jet velocity and the dynamic pressure were compared. The predictions revealed that a little under-expansion is somewhat helpful to improve the dynamic pressure. The jet dynamic pressure and its width for the specific nozzle geometry were also studied. It was observed that a variation in the ambient pressure can influence the jet momentum and its width. In addition, a high ambient temperature was found to have a positive effect on the improvement of the jet dynamic pressure. Furthermore, it was found that a change in ambient pressure has a stronger effect on the jet force than a change in the ambient temperature. In addition, it was proved that the profiles of the dynamic pressure at a certain blowing distance fit well to Multi-Gaussian distribution. Post combustion in a BOF/LD and an AOD process during decarburization was also studied. Two mathematical models were created to show the post combustion phenomenon inside the converters, respectively. For the CFD modeling of the two processes, the realizable k-ɛ model, the species transport model and the discrete ordinate were adopted to calculate the turbulence, gas reaction and radiation present in the gas phase in the converter. For the BOF/LD modeling, a series of plant tests were conducted to collect data, which were used in the current model. These include the off-gas information, emissivity data, oxygen blowing parameters and the chemical composition of steel. After the simulation, the predicted flow pattern and detailed information of the gases taking part in the post combustion were compared to plant data. Specifically, the off-gas data from the plant was used for the model verification. The measured CO2 concentration was 15-20 wt% and the predicted value from the modeling was 16.7 wt%. For the AOD converter of interest in the current work, a fan is installed in the end of the AOD flue to help extract the off-gas from the converter. The influence of different fan gauge pressures as well as temperatures of the gas mixture, containing the generated CO and argon, on the post combustion in the whole AOD system was studied. It was indicated from the modeling results that the post combustion was only present in the flue for the present modeling conditions. Moreover, a critical fan gauge pressure (approx.. -550 Pa) was found which could yield a maximum post combustion in the flue gas. For both two models (BOF/LD and AOD), simulations indicated that a change of the converter temperature from 1500 to 1700 °C did not influence the post combustion reaction to a large degree. In addition, these two models can be regarded as the first step for a future more in-depth modeling work of the post combustion. / <p>QC 20130913</p>

By focusing on the cooling requirement of high power LED, the study aims to explore the spray cooling method and analyze its cooling performance. The ultrasonic micro-nozzle plate made of piezoelectric ceramic material was used in this experiment in order to establish a spray cooling system. The nozzle plate array (3 ¡Ñ 2) was used to carry out a cooling test for 24 LEDs with high power (6 ¡Ñ 4). Three different watts (1 W, 3 W, 5 W) of LED were tested, the total input power was 24W, 72W and 120 W, respectively, and the working medium was DI water. The goal is to understand the variance in performance caused by nozzle plates of different nozzle diameters (dj = 7, 35 £gm) in varied nozzle distances (z = 10, 20, 30, 40, 50 mm). The experiment used thermocouples to measure the slug temperature of LED. By applying thermal resistnace to the LED to calculate its chip temperature, and using micrometer resolution particle image velocimetry (£gPIV) to observe the spray flowfield inside the LED chamber, this study analyzes the influence of flowfield change on cooling performance.

This study aims to explore the use of an ultrasonic micro-nozzle plate, made of piezoelectric ceramic material, as a core material to establish a set of spray cooling system for high power LED. The system uses a single nozzle plate to implement a cooling test for 4 high power LEDs (2 ¡Ñ 2). The total input power was 4 W, 12 W and 20 W, and working medium was DI water. In order to understand the performance variance introduced by utilizing nozzle plates with differing nozzle diameters (dj = 7, 35 £gm) across various nozzle exit to test distance (z = 10, 20, 30, 40, 50 mm). By using micrometer resolution particle image velocimetry (£gPIV) to observe the spray flowfield inside the chamber, and using thermocouples to measure the temperature of LED slug and thermal resistance was used to calculate the LED junction temperature , Tj, for analyzing the influence of flowfield change spread in chamber on its cooling performance. The possibility of an LED spray cooling system is also explored.

This study presents a novel concept to integrated nebulizer nozzle plate for FD-ESI (Fused-droplet Electrospary Ionization Mass Spectrometry) using modified LIGA process. This fabrication technique can reduce the production cost of current nozzle plate. It comprises of multi-exposure and single develop (MESD) process, the extra-hard Ni-Co (Nickel-Cobalt) electroforming and thin-wall plastic microinjection molding. The template of nozzle plate is patterned using dry film and MESD process. Later, the template is transferred into metal Ni-Co mold by electroplating. In this study, the technique of extra-hard Ni-Co alloy electroplating process with Hardness of Vickers over (HV) 550 is developed. Then with the stiffness of Ni-Co mold, it can withstand high injection speed. Thin-wall microinjection molding process with short cycle time to fabricate nozzle plate can be finished. Liquid crystal polymer (LCP) is used for thin-wall microinjection molding process. In order to make efficiently atomization, we used ANSYS to optimize PZT actuator. Besides, the work of nebulizer with FD-ESI was demonstrated in this study. a novel design of nozzle plate.

No description available.

<p>A prerequisite for aeroelastic stability prediction inturbomachines is the understanding of the fluctuatingaerodynamic forces acting on the blades. Unsteady transonicflows are complex because of mutual interactions betweentravelling pressure waves, outlet disturbances, shock motion,and fluctuating turbulent boundary layers. Complex phenomenaappear in the shock/boundary layer region and produce phaselags and high time harmonics, which can give a significantcontribution to the overall unsteady lift and torque, andtherefore affect flutter boundaries, cause large localstresses, or even severely damage the turbomachine.</p><p>The present research work is concerned with theunderstanding of phenomena associated with travelling waves innon-uniform transonic flows and how they affect the unsteadypressure distribution on the surface as well as the far fieldradiated sound. In similitude with turbomachines potentialinteraction, the emphasis was put on the unsteady interactionof upstream propagating acoustic waves with an oscillatingshock in 2D and 3D nozzle flows. Both numerical andexperimental studies are carried out and compared with eachother.</p><p>Results shows that the unsteady pressure distribution, bothon the bump surface and within the channel, results from thesuperposition of upstream and downstream propagating waves. Itis believed that outlet pressure perturbations propagateupstream in the nozzle, interact in the high subsonic flowregion according to the acoustic blockage theory, and arepartly reflected or absorbed by the oscillating shock,depending on the frequency of the perturbations and theintensity of the SBLI. Furthermore the shock motion amplitudeis found to be related to the mean flow gradients and localwave length of the perturbations rather than to the shockboundary layer interaction. The phase angle between incomingpressure perturbations and the shock motion increases with theperturbation frequency but also depends on the intensity of theSBLI. Additionally the phase angle "shift" observed underneaththe shock location linearly increases with the perturbationfrequency and the shock strength. Such phase shift is criticalregarding aeroelastic stability and might have a significantimpact on the phase angle of the overall aerodynamic forceacting on the blade and shift the aerodynamic damping fromstable to exciting.</p><p><b>Keywords:</b>Shock Boundary Layer Interaction, ShockMotion, Unsteady Flows, Nozzle Flows, Potential Interaction,Back Pressure Perturbations.</p>

A novel method was developed to design and fabricate nozzles capable of producing low-divergence fluid jets. Nozzle apertures were elliptical, and jets exhibited elliptical cross-sections with divergence varying predictably between 0 and 13°. Nozzle aperture aspect ratios varied from 1.00 to 2.45, area was equivalent to that of a 6mm diameter circle. An elliptical jet was developed with 0.4° and 0.9° divergence in the major and minor axes, respectively. Performance of this elliptical nozzle was compared to that of a circular nozzle via profiled creep-feed grinding trials. Results indicate the circular nozzle performs similarly to the horizontal ellipse; the vertical ellipse frequently caused wheel breakdown. Optimized cutting parameters: wheel speed 23m/s, cut depth 1.78mm, feed rate 200mm/min, jet pressure 3.21MPa or greater. Experiments were performed on a Blohm Planomat 408 CNC grinding machine using CimTech 310 cutting fluid. Nozzle experiments used a Brix concentration of 6.1%, grinding experiments used 3.1%.

No description available.

An experimental apparatus was designed and built to study the thermal autoxidative carbon deposition, or coking, in the fuel injection nozzles of small gas turbine engines. The apparatus is a simplified representation of an aircraft fuel system, consisting of a preheating section and a test section, which is a passage that simulates the geometry, temperatures, pressures and flow rates seen by the fuel injection nozzles. Preliminary experiments were performed to verify the functionality of the apparatus. Pressure drop across the test section was measured throughout the experiments to monitor deposit buildup, and an effective reduction in test section diameter due to deposit blockage was calculated. The preliminary experiments showed that the pressure drop increased more significantly for higher test section temperatures, and that pressure drop measurement is an effective method of monitoring and quantifying deposit buildup.

An experimental apparatus was designed and built to study the thermal autoxidative carbon deposition, or coking, in the fuel injection nozzles of small gas turbine engines. The apparatus is a simplified representation of an aircraft fuel system, consisting of a preheating section and a test section, which is a passage that simulates the geometry, temperatures, pressures and flow rates seen by the fuel injection nozzles. Preliminary experiments were performed to verify the functionality of the apparatus. Pressure drop across the test section was measured throughout the experiments to monitor deposit buildup, and an effective reduction in test section diameter due to deposit blockage was calculated. The preliminary experiments showed that the pressure drop increased more significantly for higher test section temperatures, and that pressure drop measurement is an effective method of monitoring and quantifying deposit buildup.