Experimental Study of Methane Heat Transfer Deterioration in a Subscale Combustion Chamber

Methane has many possible advantages as a fuel for reusable rocket engines and is therefore extensively discussed. However, the characteristics of methane as a coolant in a regenerative cooling system are widely unknown. Especially the heat transfer deterioration that occurs in the vicinity of the critical point is a major concern and a severe drawback. To investigate this phenomenon and to establish a broad data basis for the validation of numerical simulations, tests were performed with a subscale combustion chamber. The combustion chamber contains different cooling channel geometries (rectangular cooling channels with the aspect ratios [height-to-width ratio]: 1.7, 3.5, 9.2, and 30) and was cooled with cryogenic methane. Results close to the critical point show a distinct maximum in hot gas wall temperature, which is a clear evidence of heat transfer deterioration. The test results indicate a strong dependency on the occurrence of this effect toward cooling channels with a low aspect ratio.