David CERANTOLA, Daniel HANDFORD, Pradeep DASS
DOI Number: 10.82241/ceas-hisst-2024-252
Conference number: HiSST-2024-252
Leveraging computational fluid dynamics to design ramjet combustors requires a trade-off between solution fidelity and imposed assumptions. Many previous analyses decoupled the combustor from the adjacent components to increase confidence in the complex chemistry were at the expense of neither capturing flow distortion impact on thrust nor nozzle surface temperatures in excess of material limitations. Given the expectation that a lower fidelity approach can capture bulk flow trends from gaseous-hydrogen and air combustion, the 2D computational domain considered in this paper evaluated both the combustor and converging-diverging nozzle sections with the realizable k-ε turbulence model, two-step reaction mechanism, and turbulence chemistry interactions equated using the eddy dissipation concept.
A baseline study that varied flight Mach number (M0) between 3 and 5 and dynamic pressure between 21 kPa and 76 kPa (3–11 psi) showed that specific impulse (Isp) varied between 2400 s and 3600 s as a function of M0 with maximum wall and liner temperatures staying below suggested limits 1300 K and 1770 K respectively. A geometric study that varied injector, flameholder, and liner parameters at M0 = 3 or 5 and 5 psi operating conditions found that performance was most strongly influenced by equivalence ratio φ and liner length L26 where maximizing L26 was beneficial for thrust but L26 < 1 m was required to respect the temperature limits. Setting φ = 0.7 resulted in maximum Isp > 3800 s whereas thrust was maximum when φ = 1.1. The best configuration had no appreciable change in Isp but increased thrust by 41% and 7% at the M0 =3 and 5 conditions respectively relative to the baseline results. Conclusions identify how the geometric parameters response variability can be leveraged to improve design.