Keiichi Okuyama

Prediction Accuracy of Thermal Response of Ablator Under Arcjet Flow Conditions

Cloth-layered carbon fiber reinforced plastic ablator with a specific gravity of about 1.5 is developed to examine the prediction accuracy of analysis methods associated with the thermal response of ablator. Heating tests are carried out in the arcjet wind tunnel to quantify the thermal performance of ablator so developed. In the tests, the surface temperatures and in-depth temperatures of ablative test pieces are measured during the testing. Thermal response models of ablator are also developed in this study. Thermal conductivity measurements are conducted by using the steady-state method. Thermal diffusivity values of ablator are measured by using the laser-flash method. Thermal gravimetric analysis is also made to model the pyrolysis phenomena of ablating test piece. The experimental results obtained in the heating tests are analyzed by the one-dimensional ablation code with the thermal response models developed in this study. By comparing the calculated results and experimental results, the prediction accuracy of thermal response models of ablator is discussed.

An Experimental Study on Thermal Response of Low Density Carbon-Phenolic Ablators

Coking phenomenon for low density carbon-phenolic ablative material exposed to aerodynamic heating is examined experimentally. The low density ablators with the nominal virgin density of 0.24g/cm3 are heated in arcjet wind tunnels with nitrogen and air as a test gas. The material in-depth density, in-depth and surface temperatures are measured. The density increase within the char layer is observed for the test specimens heated in the nitrogen arcjet freestream. In contrast, the coking behavior is not clearly seen for the case of air arcjet testing. The present study shows that the nature of the in-depth density distribution is very sensitive to the heating conditions.

Evaluation of Prediction Accuracy of Thermal Response of Ablator Under Arcjet Flow Condisions

Using a cloth-layered carbon fiber reinforced plastic ablator with a specific gravity of about 1.5, the thermal response model of ablator is studied experimentally and numerically. Heating tests are carried out in the arcjet wind tunnel to quantify the thermal performance of ablator. In the tests, the surface temperatures and in-depth temperatures of ablative test pieces are measured during the testing. The experimental results obtained in the heating tests are analyzed by using a two-dimensional analysis method developed earlier. In the method, the thermal response of ablator is calculated by loosely coupling the shock layer computational fluid dynamics code and the 2-D version of ablation code using an arcjet freestream condition. The arcjet freestream condition in the test section is evaluated by calculating the flows in the arcjet wind tunnel. The present analyses are made especially focusing on an anisotropic nature of thermal conduction of ablator. Thermal conduction inside the ablator is modeled in the present analysis method based on thermal conductivity values measured for different ply angles of carbon cloths of ablator. By comparing the calculated results with the arcjet data, the prediction accuracy of thermal response models of ablator is discussed.