Total temperature estimation of a hydrogen/air burned-gas torch igniter for a scramjet combustor

Abstract

Forced ignition is important for the scramjet engines in supersonic flights. When compared to other forced ignition devices, burned-gas torch igniters are considered suitable for scramjet combustors because it is easy to control the input energy of burned-gas torch igniters. In the conventional burned-gas injection methods, the injection gas total temperature is estimated by assuming a discharge coefficient in the range of 0.90-0.95. However, the assumption has not been validated and it may cause misestimations when analyzing combustion in scramjet engine in supersonic flight. Therefore, a validated temperature estimation method is needed. In this paper, a new total temperature estimation method was proposed and investigated experimentally and numerically. Additionally, a novel hydrogen/air burned-gas torch igniter, which can control the injection gas total temperature by controlling the overall equivalence ratio, was also developed. The experimental results showed that the newly-developed hydrogen/air burned-gas torch igniter can successfully control the injection gas total temperature by changing the overall equivalence ratio in the range of 1.0-10.0. Also, the chemical equilibrium assumption for estimating injection gas compositions was validated by O2 mole fraction measurement. The numerical results showed that the estimated discharge coefficient results in a maximum underestimation of 7.02% due to wall heat loss, which means that the maximum uncertainty of the estimated total temperature is 14.7%. This, in turn, indicates that the influence of wall heat loss on the discharge coefficient should be considered to estimate the injection gas total temperature more accurately.

Development and verification of a supersonic nozzle with a rectangular cross section at a Mach number of 2.8 for a scramjet model combustor

“…The distance between cavity leading wall and the center axis of the injection hole is 2.5 mm. The burned gas is supplied to the cavity flameholder by the hydrogen/air burned gas torch igniter developed by Yamaguchi et al (2018). This igniter can control the injection gas temperature by generating burned gas at equivalence Yamaguchi, Hizawa, Ichikawa, Kudo, Hayakawa and Kobayashi, Journal of Thermal Science and Technology, Vol.13, No.2 (2018) ratios ranging from 1.0 to 10.0.…”