Secondary Combustion of Micron-Sized Magnesium Powder to Enhanced Kerosene-Fueled Scramjet Thrust

Abstract

In the pursuit of enhancing the thrust performance of scramjet engines under extreme conditions, a novel approach known as powder-enhanced scramjet (PES) was designed, incorporating secondary combustion between magnesium powder and combustion products of kerosene fuel. In this study, simulated air enters the combustor at Mach 2.0 and a total temperature of 1600 K, with an RP-3 equivalence ratio of 1.0. Magnesium powder was injected into the combustion products of kerosene for secondary combustion in the midsection of a direct-connected scramjet. Thrust performance is evaluated by measuring inner wall pressure along the flow. This study explores the impact of various structural configurations and powder–gas ratios on PES thrust performance. Results affirm the feasibility of the PES concept, revealing a specific thrust gain of up to 28.8% with the addition of 7.5% magnesium powder. Magnesium powder primarily reacts with carbon dioxide and water vapor in combustion products, as confirmed through product analysis. Among the tested structural configurations, the approach employing a central strut for magnesium powder injection and mixing promotion exhibits comprehensive performance, considering basic specific thrust, specific thrust gain, and condensed-phase product deposition. Within a 10% powder–gas ratio, increasing the proportion of injected powder significantly improves engine thrust performance. However, beyond 9%, the rate of specific thrust gain increase begins to decelerate, suggesting an optimal range for powder injection.