Sung Nam Lee

Effects of Nozzle Characteristics on the Rear Fuselage Temperature Distribution

In order to enhance the aircraft survivability, infrared signatures emitted by engine parts should be diminished. For its reduction it is necessary for the rear fuselage temperature to be decreased. In this study, numerical modeling of flow fields and heat transfer of nozzle is performed and its temperature distribution along each component wall is predicted. The effects of material characteristics and shape of nozzle wall and radiation shield on the heat transfer are also investigated. Through this numerical analysis, design parameters related to the susceptibility of aircraft are examined.

Numerical Analysis of Quasi-Steady-Combustion Characteristics in a Solid Rocket Motor

A numerical code that simulates combustion phenomena occurring in a solid rocket motor is developed in this study using a preconditioning algorithm. A quasi-steady-combustion process was analyzed for a composite material in a submerged nozzle. The governing equations were solved using a dual-time stepping method combined with a finite volume method. The mass flux and pressure in the cell face were evaluated using the advective upwind splitting method scheme. The turbulence model uses a two-equation model combined with a turbulence closure model. The geometric conservation law is used to simulate transient propellant surface regression. The numerical results for solid rocket combustion were compared with experimental results with a composite propellant. The calculated pressure variation in the combustion chamber is in good agreement with the measured results.

The Effects of Heat Shielding in Jet Engine Exhaust Systems on Aircraft Survivability

The infrared signatures from hot engine parts pose major threats to military aircraft survivability. Reducing the skin temperature at the rear of the fuselage is key to reducing susceptibility to heat-seeking armaments. A heat shield placed between the nozzle wall and the outer casing of the engine can decrease the skin temperature at the rear of the fuselage. Therefore, numerical modeling of the fluid flow fields coupled with the radiative and conductive processes within the heat shield, nozzle, and casing were performed to determine the temperature distribution at the rear of the fuselage. The effect of the material properties and the dimensions of the heat shield were studied in order to determine their effects on the susceptibility of an aircraft.

Analysis of Radiative Heat Flux for Nozzle Flow

— A finite volume method with non-gray gas model is applied to investigate radiative heat flux on the inside wall of nozzle. The radiative properties of non-gray gas are predicted by using weighted sum of gray gases model (WSGGM). Again, 4 gray gases and narrow band based WSGGM is used to predict total heat flux and spectral intensity on the nozzle wall. Finally, the hybrid use of 4 gray gases and narrow band based model is applied to reduce computational time preserving accuracy.

Investigation of the Radiative Heating from Aircraft Plume with Particles

The finite volume method for radiation is applied for the analysis of radiative base heating by SE and PE of the aircraft exhaust plume. The exhaust plume is considered as an absorbing, emitting, and scattering medium, while the base plane is assumed to be cold and black. The radiative properties of non-gray gases are obtained through the WSGGM, and the particle is modelled as spheres. The present method is validated by comparing the results with those of the backward Monte-Carlo method and then the radiative base heating characteristics are analyzed by changing such various parameters as particle concentration, temperature, and scattering phase function. The results show that the radiative heat flux coming into the base plane decreases with altitude and distance, but it increases as the particle temperature increases. The forward scattering of particles increases PE while it decreases SE.

Influence of thrust vectoring on radiative heat flux from plume flow

A finite volume method with nongray gases is applied to examine the radiative base heating due to plume which is changed by mechanical deflection. Numerical approaches are made to predict the effect of TVC. The radiative properties within plume flow are modeled with the weighted sum of 4 gray gases. The exhaust plume is considered as an absorbing and emitting medium with no scattering. Flow field is molded with using Preconditioned Navier-Stokes(N-S) algorithms with multiblock. The Geometric Conservation Law(GCL) is considered to compute the nozzle moving mechanism. The radiative base heating is changed by the nozzle deflection angle.

Numerical Study on the Unsteady Solid Rocket Propellant Combustion with Erosive Burning

A numerical modelling was performed to predict unsteady combustion processes for the AP/HTPB/Al propellant in a solid rocket motor. Its results were compared with the experimental data. Temporal pressure development was found to match quite well with measured data. A change in propellant surface was traced using the moving grid. The propellant thickness change was also observed to confirm the erosive burning effect.