Man Sun Yu

Recovery Temperature Measurement of Underexpanded Sonic Jets Impinging on a Flat Plate

An experimental investigation has been carried out to examine heat-transfer characteristics of an axisymmetric, underexpanded, sonic jet impinging on a flat plate. The ratio of nozzle-exit pressure to the ambient pressure, that is, underexpansion ratio ranges from 1.5 to 3.5, and the distance from the nozzle exit to the plate is adjusted from 0.5 to 20.0 nozzle-exit diameters. Detailed measurements of the recovery factor and the surface pressure on the flat plate have been achieved

Distributions of Recovery Temperature on Flat Plate by Underexpanded Supersonic Impinging Jet

An experimental investigation has been conducted on the impingement of underexpanded, axisymmetric, and supersonic jets on a flat plate. The surface pressure and the adiabatic wall temperature distributions on the flat plate have been measured in detail at small nozzle-to-plate distances. The influences of the pressure ratio, the exit Mach number, the nozzle-to-plate distance, and the impinging angle have been considered. The surface pressure and the adiabatic wall temperature distributions on the flat plate for supersonic jet impingement are affected significantly by the nozzle-to-plate distance and the existence of a stagnation bubble in the central region

Heat transfer on flat surface impinged by an underexpanded sonic jet

Underexpanded impinging jets include complicated flow phenomena such as shock structure, sonic surface, and recirculation zone in a central impingement region, and the local heat transfer on an impinged surface has a different characteristic than a subsonic impinging jet. Studying this can be helpful in understanding the relation between supersonic flow characteristics and heat transfer on a surface. It can also provide a proper design factor for the impingement cooling technique by a high-speed jet. The convective heat transfer coefficients have been measured on a flat surface impinged by an underexpanded sonic jet. In addition, the visualization of shock structures and surface pressure measurements have been conducted to support the heat transfer measurement results. From the results, the distribution of the heat transfer coefficient on the central impingement region due to the interaction between the sonic surface and recirculation flow has been obtained

NUMERICAL STUDY ON A THERMAL RESPONSE OF THE JET VANE SYSTEM IN A ROCKET NOZZLE

The analysis of the heat transfer characteristics on the surface of jet vane needs to know ablation mechanism in a rocket engine. In this study, the distribution of heat transfer coefficient on the vane surface is calculated by means of the thermal boundary layer analysis for two dimension jet vane model. This method is only needed to get the free stream information around a vane and not required many fine meshes with large calculation time. User defined functions are inserted into a numerical code (FLUENT) for calculation of thermal boundary conditions. Some properties such as density, Mach number and heat transfer coefficient are plotted along the vane surface for different attack angles and several time steps. Also, the temperature contour inside vane is represented during the operation time. Finally, the heat transfer coefficient calculated by boundary layer integral method compares to that of using FLUENT solver itself.

A STUDY ON A SURFACE ABLATION OF THE JET VANE SYSTEM IN A ROCKET NOZZLE

During the rocket propulsion process, the jet vane which is installed in the rear side of rocket nozzle part is ablated chemically or mechanically due to the interaction of vane with a combusted gas. In this study, the simulation for the chemical ablation phenomenon of jet vane is tried out as a basic research on the jet vane performance test. Also, distributions of thermal boundary conditions such as heat transfer coefficient and recovery temperature are calculated and used as the input values for the acquisition of surface ablation rate. The thermal boundary layer integral method is applied to the calculation of these boundary conditions. User defined functions are inserted into a numerical code (FLUENT) for calculation of thermal boundary conditions and surface ablation rate. Leading edge on a jet vane is heated heavily compared with the side surfaces and therefore the ablation occurs primarily on that part. When the jet vane is rotated, the windward surface is heated and ablated more than the leeward surface. However, the ablation rate on a side surface is much lower than that on a leading edge of vane, so ablation of jet vane side surface can be ignored during the jet vane ablation simulation. In about 10 seconds of vane operation time, total ablation area is calculated not to be over 4% of the vane side surface area.

Heat Transfer near Sharp and Blunt Fins Protruded in a Supersonic Flow

Heat transfer characteristic near a sharp fin and blunt fin were studied in a supersonic flow. The unit Reynolds number was 5x10/m, respectively. Infra-red thermography was used to obtain the variation of surface heat transfer coefficient distribution. The oil and lampblack method was conducted to understand flow fields near a fin. Heat transfer increase in a flow separation region and peak heating appears at a flow reattachment region. As the wedge angle increases, effective area and peak value also increased.

Hybrid Thermal Analysis on Film Cooled Ramjet Combustor

Thermal analysis has been conducted numerically on a film cooled ramjet combustor with combining experimental data. The film cooling effectiveness and heat transfer coefficient on the exposed combustor wall were taken experimentally in a cold flow test to obtain the thermal boundary conditions. Distributions of temperature and thermal stresses on the combustor liner were calculated by using the boundary conditions from experimental data and a commercial code, ANSYS. The high thermal stress appears after the stabilizer wall. That is also the region attached by combustion flame. Thermal fracture will occur on the region of high thermal stress due to high temperature difference. The present results of temperature and stress distributions provide a guide line for thermal design in a film cooled ramjet combustor.

HEAT TRANSFER COEFFICIENTS ON A FLAT SURFACE IMPINGED BY THE UNDER-EXPANDED SONIC JET

An experimental investigation has been carried out to examine heat-transfer characteristics of an axisymmetric, under-expanded, sonic jet impinging on a flat plate and the local measurement of surface pressures and heat transfer coefficients on a plate have been achieved together with a visualization test of shock structure in a jet. Heat transfer coefficients on a plate have been found to be changed significantly depending on the under- expansion ratio as much as the nozzle-to-plate distance and these phenomena have been explained with other results and discussions by other

Impingement of Axisymmetric Under-Expanded Sonic Jets on a Flat Plate

An experimental investigation has been carried out to examine heat transfer characteristics of an axisymmetric, under-expanded, and sonic jet impinging on a flat plate. Distributions of recovery factor and the surface pressure on the flat plate have been obtained in detail. The ratio of nozzle exit pressure to the ambient pressure, i.e., under-expansion ratio ranges from 1.5 to 3.5 and the nozzle-to-plate distance is tested from 0.5 to 20.0 nozzle exit diameters. It has been found that the recovery factor varies from 0.35 up to over 1.25 depending on both parameters of interest within the present experimental range.Copyright