Investigation on heat loss of microtube combustor

To understand heat loss characteristics of micro-combustor, combustion of CH₄/O₂ took place in a ceramic tube with inner diameter of 0.6mm, and temperature on the outer wall of the tube was measured. In the combustion tests, influence of total mass flow rate and mass ratio of O₂ and CH₄ on the heat loss of the tube wall was studied. The tests' results show that when mixture ratio is lower than the stoichiometric ratio, with the increase of ω(O₂)/ω(CH₄), combustion heat power increases. Therefore, wall temperature rises and heat loss power increases. The heat loss power occupies a very large proportion of the combustion power and the largest in the tests is 42%. However, in the wall heat loss, radiative heat loss accounts for a large part and the largest reaches 65% of the total heat loss. When the mass flow rate of O₂ and CH₄ is increased, combustion zone in the micro-tube is enlarged and temperature difference along the tube wall becomes smaller. Meanwhile, the combustion heat power and wall temperature variation rate increase.