Bridging the Supersonic-to-Hypersonic Gap, Scientists Reveal Scramjet Igniter That Maintains Combustion Below Mach 5

Nagoya University scientists have developed an RD torch that enables sustained combustion in a scramjet engine below Mach 5, a critical step in bridging the supersonic-to-hypersonic gap. The RD torch, a rotating detonation combustor, was tested in a scramjet model combustor and a vacuum chamber, achieving continuous injection of burned gas into the cavity, with combustion nearly complete even during main hydrogen combustion. The study claims that under simulated flight Mach 3–4 conditions, the RD torch successfully ignited and sustained combustion, operating in detonation mode. The team reports that the mainstream flow in the scramjet model remained supersonic, demonstrating robust torch operation.

The RD torch was designed to address the challenge of maintaining ignition below Mach 5 in scramjet engines, where the total temperature of the airflow decreases, making autoignition less likely. Previous attempts to improve scramjet ignition had focused on higher Mach numbers, leaving the performance at sub-Mach 5 conditions unclear. The RD torch, compared to conventional deflagration torches, uses a rotating detonation wave to burn fuel and oxidizer, continuously discharging combustion gases into the cavity. The team claims that the RD torch is a promising candidate for scramjet ignition, as it can achieve ignition and flameholding under low-Mach conditions.

The study, published in the Journal of Propulsion and Power, highlights the RD torch's potential for practical use in future scramjet-powered airbreathing hypersonic engines. The results confirm successful supersonic combustion and demonstrate the RD torch's ability to reliably ignite and sustain main hydrogen combustion under low-Mach scramjet conditions. The team's findings suggest that the RD torch can bridge the gap between supersonic and hypersonic propulsion, offering a viable solution for aircraft propulsion systems.

AI-generated summary of the original article — see the source for the full story.