Computational Study on Aerodynamic and Thermal Characteristics of a Hot Jet in Parallel Flow

The study of the migration characteristics of turbulent jets has become relevant as they are used in a variety of engineering devices and are encountered in combustion, chemical processes, and processes involving cooling, mixing, and drying. In several applications, especially in the case of hot streaks in gas turbines, the knowledge of mixing phenomena becomes crucial from a design perspective. The purpose of this study is to look into the characteristics of a round hot jet in a parallel air flow. A jet of hot air injected through a nozzle into a flow of cold air has been considered. Numerical simulations were carried out with different hot jet temperatures and two different Reynold’s numbers, thus aiming at understanding the effect of initial conditions on the mixing of the jet. The temperature profiles were studied at different sections downstream of the nozzle. The results are presented in non-dimensional form.

Computational Study of Performance Characteristics for Truncated Conical Aerospike Nozzles

Aerospike nozzles are advanced rocket nozzles that can maintain its aerodynamic efficiency over a wide range of altitudes. It belongs to class of altitude compensating nozzles. A vehicle with an aerospike nozzle uses less fuel at low altitudes due to its altitude adaptability,where most missions have the greatest need for thrust. Aerospike nozzles are better suited to Single Stage to Orbit(SSTO) missions compared to conventional nozzles. In the current study, the flow through 20% and 40% aerospike nozzle is analyzed in detail using computational fluid dynamics technique. Steady state analysis with implicit formulation is carried out. Reynolds averaged Navier-Stokes equations are solved with the Spalart-Allmaras turbulence model. The results are compared with experimental results from previous work. The transition from open wake to closed wake happens in lower Nozzle Pressure Ratio for 20% as compared to 40% aerospike nozzle.

Numerical Simulation of Duct Flow with Fog Droplets

Evaporative cooling is a widely used air cooling technique. In this method, evaporation of a liquid in the surrounding air cools the air in contact with it. In the current investigation, numerical simulations are carried out to visualize the evaporation and dynamics of tiny water droplets of different diameters in a long air duct. The effect of initial droplet size on the temperature and relative humidity distribution of the air stream in the duct is investigated. Three different initial conditions of air are considered to verify the influence of ambient conditions. Droplet spray patterns are also analyzed to identify the suitable locations for the spray nozzles within the duct. The results obtained are displayed in a series of plots to provide a clear understanding of the evaporative cooling process as well as the droplet dynamics within the ducts.

Computational study on flow through truncated conical plug nozzle with base bleed

Conical plug nozzle and truncated conical plug nozzle are advanced rocket nozzles suitable for use as altitude compensating nozzles.In this study flow through the conical plug and truncated conical plug nozzles are numerically simulated to first validate with experimental data and then to compare the performance when a base bleed is introduced.The numerical analysis has considered two-dimensional axisymmetric models.Reynolds-averaged NavierStokes equations are solved with two equation shear stress transport k-ω turbulence model.For the validation of the plug nozzle,flow features and wall pressure along the length of the nozzle is taken for different nozzle pressure ratios.For the validation of truncated plug nozzle,flow features and base pressures at various nozzle pressure ratios are compared.The base bleed is taken as 2%of the inlet mass flow rate.The comparison of results shows that the introduction of base bleed helps to compensate for the loss of thrust due to conical plug nozzle truncation.

Experimental Study on the Inlet Fogging System Using Two-Fluid Nozzles

Large-capacity compressors in industrial plants and the compressors in gas turbine engines consume a considerable amount of power.The compression work is a strong function of the ambient air temperature.This increase in compression work presents a significant problem to utilities,generators and power producers when electric demands are high during the hot months.In many petrochemical process industries and gas turbine engines,the increase in compression work curtails plant output,demanding more electric power to drive the system.One way to counter this problem is to directly cool the inlet air.Inlet fogging is a popular means of cooling the inlet air to air compressors.In the present study,experiments have been performed to investigate the suitability of two-fluid nozzle for inlet fogging.Compressed air is used as the driving working gas for two-fluid nozzle and water at ambient conditions is dragged into the high-speed air jet,thus enabling the entrained water to be atomized in a very short distance from the exit of the two-fluid nozzle.The air supply pressure is varied between 2.0 and 5.0 bar and the water flow rate entrained is measured.The flow visualization and temperature and relative humidity measurements are carried out to specify the fogging characteristics of the two-fluid nozzle.

Computational Study on the Influence of Number of Threads on the Perfor-mance of Single Screw Pump at High Angular Velocities

Fluid flow in a screw pump which rotates at very high angular velocity is numerically analyzed. In the present study, fluid flow in screw pumps under high Reynolds number, of the order of 105, is considered. Screw pump has two major elements, a plain shroud which is a stationary element and a rotating hub with helical grooves contained within the shroud. In this paper, three variants of hubs with different number of thread starts numbering six, eight and twelve in combination with a plain shroud is studied. Each of the three possible combinations are analyzed on the basis of pressure rise developed, efficiency and shaft power. It was seen that pressure rise, efficiency and shaft power increases as the number of threads increases in the range of mass flow rates studied.