InterPore2025

Development of a laser-heated facility to investigate coking in ablators

21 May 2025, 10:05

1h 30m

Poster Presentation (MS17) Complex fluid and Fluid-Solid-Thermal coupled process in porous media: Modeling and Experiment Poster

Speaker

Mr Junhao Zhang (New Mexico State University)

Description

When exposed to high temperatures, carbon/phenolic ablators undergo pyrolysis. In this process, the phenolic component of the ablator gets decomposed into a series of gaseous products. These products percolate through the hot fibrous charred material towards the surface, providing a blockage effect from the harsh external environment. While
the pyrolysis products percolate through the hot fibrous material, they may interact with it, creating Gas-Surface Interaction (GSI) processes which can lead to coking, also known as carbon deposition. The deposition process has two main effects: a change in properties of the material, such as the permeability, and the change in the composition
of the pyrolysis gas flux. Both these effects may have an important impact on the thermal protection system (TPS) performance. On the one hand, a significant decrease in permeability could lead to pressure buildup in the TPS which could result in fracture. On the other hand, a change in composition of the pyrolysis gas flux could affect
aerothermal calculations of the GSI at the surface of the ablator. Characterizing the deposition process is then crucial for the development of advanced TPS.
In this work, we propose the development of a new experimental facility to study this process. A high power laser (1.5 kW) will be used to heat up the surface of the sample material (e.g., FiberForm or charred material), generating an important temperature gradient within the sample. Simultaneously, a flow of gases will be supplied to the sample material from the opposite side to simulate the flow of pyrolysis products. The injected gases can be selected in such a way to simulate a pyrolysis gas mixture. We will start investigating methane since it is one of the most
produced products from the pyrolysis of phenolic resin and it is also easy to procure. We expect to evaluate different gaseous mixtures containing the main products such as toluene, water, methane, and benzene. The conditions will be monitored by a custom made LabView program to track pressure, surface temperature and laser power.
Preliminary simulations using the Porous material Analysis Toolbox based on OpenFOAM (PATO) showed that with our high laser power, we can achieve representative conditions in terms of temperatures. These simulations do
not consider any lateral heat loses and assume a 1D sample of TACOT database fictitius material.
Tested samples will be analyzed by means of Scanning Electron Microscopy (SEM) and by micro-compute tomography to determine the amounts and locations of deposition. This will help as develop and validate finite rate chemical models for the GSI of pyrolysis gases on carbonaceous porous materials