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Flow separation is a common fluid dynamics phenomenon that occurs within supersonic nozzles while operating at off-design pressures. Typically, off-design pressures result in a shock formation that leads to a non-uniformity of the exiting flow and creates flow separation and flow recirculation. So far, no effective solution has been presented to eliminate flow separation and increase the total performance of the nozzle. The purpose of this work is to investigate whether a Gurney flap may beneficially affect the exiting flow pattern. For a better understanding of the Gurney flap effect, this investigation used a supersonic nozzle geometry based on a previous study by Lechevalier [33]. Results from the tested cases showed a poor effect of the flap at high free-stream Mach number and lower pressure ratio. Simulations of different flap heights along with different parameters showed a slight increase of thrust.

In this paper, an array of converging-diverging nozzles in parallel is designed to create a highly turbulent, sufficiently mixed flow for the study of turbulent-compressibility effects and assist in the ongoing work of oblique detonation wave (ODW) research. Several nozzle array candidates were designed with varying numbers of nozzles and nozzle sizes and evaluated using computational fluid dynamics to determine which candidate produced the most viable conditions for investigating turbulent compressibility effects. Conditions and design restrictions of the nozzle arrays were tailored to the conditions set in the Hypersonic Wind Tunnel, which is located at the Propulsion and Energy Research Lab at the University of Central Florida.

Condensing ejectors utilize the beneficial thermodynamics of condensation to produce an exiting static pressure that can be in excess of either entering static pressure. The phase change process is driven by both turbulent mixing and interphase heat transfer. Semi-empirical models can be used in conjunction with computational fluid dynamics (CFD) to gain some understanding of how condensing ejectors should be designed and operated. The current work describes the construction of a multidimensional simulation capability built around an Eulerian pseudo-fluid approach. The transport equations for mass and momentum treat the two phases as a continuous mixture. The fluid is treated as being in a non-thermodynamic equilibrium state, and a modified form of the homogenous relaxation model (HRM) is employed. This model was originally intended for representing flash-boiling, but with suitable modification, the same ideas could be used for condensing flow. The computational fluid dynamics code is constructed using the open-source OpenFOAM library. Fluid properties are evaluated using the REFPROP database from NIST, which includes many common fluids and refrigerants. The working fluids used are water and carbon dioxide. For ejector flow, simulations using carbon dioxide are more stable than with water. Using carbon dioxide as the working fluid, the results of the validation simulations show a pressure rise that is comparable to experimental data. It is also observed that the flow is near thermodynamic equilibrium in the diffuser for these cases, suggesting that turbulence effects present the greatest challenge in modeling these ejectors.

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Atomization can be achieved by discharging liquid at relative high velocities into a slow moving environment (hydraulic nozzles) or by discharging liquid at low velocities into a fast moving gas flow (air-blast nozzles). These two types of injector nozzles are featured in majority of the industry applications such as power generation, food or pharmaceutical powder formation, spray painting, petroleum refining, and thermal sprays. The most common atomizer used in combustion engines is the pressure-swirl nozzle (Simplex nozzle) to obtain a homogenous mixture at different equivalence ratios. The experimental studies performed with pressure-swirl nozzles have reported contradictory results over the last few years. Thus, the fundamentals of spray dynamics, such as spray formation, liquid breakup length, droplet breakup regimes, and coalescence still need to be understood for a pressure-swirl nozzle. An experimental study of the breakup characteristics of various liquids and fuels with different thermal physical properties emanating from hollow cone hydraulic injector nozzles induced by pressure-swirling was investigated. The experiments were conducted using two nozzles with different orifice diameters 0.3mm and 0.5mm and injection pressures (0.3-4MPa) which correspond to Rep = 7,000-31,000 depending on the liquids being tested. Three laserbased techniques, i.e., Shadowgraph, Particle Image Velocimetry (PIV) and Phase Doppler Particle Anemometry (PDPA) were utilized in this study. Although each technique had its limitation in different flow regimes, the results were cross-validated, and generally showed correct trends in axial and radial measurements of velocity and diameter for different nozzles, Weber and Reynolds numbers. iii The spatial variation of diameter and velocity arises principally due to primary breakup of liquid films and subsequent secondary breakup of large droplets due to aerodynamic shear. Downstream of the nozzle, coalescence of droplets due to collision is also found to be significant. Different types of liquid film break up was considered and found to match well with the theory. The spray is subdivided into three zones: near the nozzle, a zone consisting of film and ligament regime, where primary breakup and some secondary breakup take place; a second zone where the secondary breakup process continues, but weakens, and the centrifugal dispersion becomes dominant, and a third zone away from the spray where coalescence is dominant. Each regime has been analyzed in detail to understand the effect of surface tension and viscosity. Surface tension and viscosity were engineered to mimic fuels, which were then compared with real fuels such as Ethanol, Jet-A and Kerosene. Results show similarity in the diameter in the beginning stages of breakup but in the coalescence regime, the values deviate from each other, indicating that the vapor pressure also plays a major role in this regime.

Compound aerospike nozzles were designed and tested as part of an ongoing experimental study to determine the feasibility of thrust vectoring an aerospike nozzle with the addition of a secondary port. Earlier phases of the study have indicated that a compound aerospike nozzle could provide sufficient thrust vectoring. The addition of a hole-type secondary port was found to provide effective thrust vectoring. Experiments were carried out to determine the effects of secondary port size, secondary port inlet geometry and compound aerospike nozzle chamber pressure. Results show good predictability, axisymmetric flow, and emphasize the importance of a radius on secondary port inlet geometry.

Yes / The fluidized bed coating system is a conventional process of particles coating in various industries. In this work, an experimental investigation was conducted using Response Surface Methodology (RSM) to optimize the coating mass of particles in a top-spray fluidized bed coating. The design of experiments (DOEs) is a useful tool for controlling and optimization of products in industry. Thus, DOE was conducted using MINITAB software, version 16. This process used a sodium silicate solution for coating the sodium percarbonate particles. The effect of the fluidization air flow rate, atomization air flow rate and liquid flow rate on the coating mass in the top-spray fluidized bed coating was investigated. The experimental results indicated that the coating mass of particles is directly proportional to the liquid flow rate of the coating solution and inversely proportional to the air flow rate. It was demonstrated that the flow rate of the coating solution had the greatest influence on the coating efficiency. / Metallic Material Processing Research Group, ACECR, Branch of Tehran University, Tehran, Iran.

Two-dimensional supersonic flows out of rocket nozzles are one of three flow types: over-, perfectly-, or under-expanded. In under-expanded flows, an expansion fan is centered at the top and bottom tip of the rocket nozzle. When the waves from the expansion wave cross through the centerline and intersect the free boundary, the waves are reflected as compression waves. For higher exit-to-ambient pressure ratios, the compression waves coalesce and eventually form a barrel shock. The purpose of this study was to use the Method of Characteristics (MOC), a mathematical procedure for solving hyperbolic partial differential equations, to simulate the formation of the barrel shock. A MOC code was developed in the Python programming language to accomplish task. Results of the MOC code compared favorably with CFD results.

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