{"id":25,"date":"2023-01-22T15:29:37","date_gmt":"2023-01-22T14:29:37","guid":{"rendered":"http:\/\/jeanlachaud.com\/?page_id=25"},"modified":"2026-03-24T17:56:52","modified_gmt":"2026-03-24T16:56:52","slug":"accueil","status":"publish","type":"page","link":"https:\/\/jeanlachaud.com\/","title":{"rendered":""},"content":{"rendered":"\n
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Phenomenology of pyrolyzing materials : (a) burning match, (b) hypersonic vehicle heat shield, (c) common in-depth material physics [Lachaud 2026]<\/a>.<\/figcaption><\/figure>\n\n\n\n

Surprisingly, the heat shield of a hypersonic space vehicle entering a planetary atmosphere and a burning match undergo comparable internal physical phenomena. The ignition of a match is triggered by the combustion of its head. The heat generated by the sulfur head starts a self-sustained process, called pyrolysis. Pyrolysis comes from the ancient Greek “pyros” (fire) and “lysis” (separation). This substantive arose from early observations that in fires wood is separated into a solid dark part (char) and combustible gases. The exothermal combustion of the pyrolysis gas in air produces more heat than necessary to keep the pyrolysis process going. When a match is held horizontally, sufficient heat is transferred into the wooden stick to sustain the pyrolysis process and a pyrolysis front propagates along the stick. Technically, one could argue that a match does not burn but that it undergoes self-pyrolysis. The pyrolysis residue is a black stick of carbonized wood (char), a quasi-pure pseudo-graphitic carbon. It is interesting to observe that a match usually bends while burning, revealing internal mechanical strains generated by thermal dilatation and pyrolysis shrinkage. The char quickly cools down and its oxidation by air is very limited. A very similar pyrolysis process occurs in the thermal protection system (TPS) of very high-speed atmospheric entry capsules, with the difference that the surface temperature is chiefly imposed by a high enthalpy flow and that the surface temperature may reach 3000\u00b0C. The same process is used to produce biofuel by heating biomass up to 1000\u00b0C in the absence of oxygen. Combustion of the char occurs in fire and TPS applications. In the TPS community, the solid combustion process is called ablation, to capture the idea that matter is removed – such as charcoal progressively being consumed in a barbecue. Spallation (mechanical erosion), melting and sublimation (solid to gas transformation) may also contribute to ablation in TPS applications, depending on the type of material and entry conditions. Engineers have to design heat shields thick enough to anticipate these ablation processes. <\/p>\n\n\n\n

The articles that are available in this website bring some contributions to improve the understanding and the modeling of these phenomena. Theses contributions are continuously integrated in the Porous material Analysis Toolbox based on OpenFoam (PATO<\/a>) that is released Open Source. The simulation of the burning match is from this code. A couple of recent articles are derived works applied to the storage and recovery of thermal energy and fluids.<\/p>\n","protected":false},"excerpt":{"rendered":"

Surprisingly, the heat shield of a hypersonic space vehicle entering a planetary atmosphere and a burning match undergo comparable internal physical phenomena. The ignition of a match is triggered by the combustion of its head. The heat generated by the sulfur head starts a self-sustained process, called pyrolysis. Pyrolysis comes from the ancient Greek “pyros” … <\/p>\n

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