Chinese researchers claim to have successfully tested a hypersonic detonation engine that can push aircraft up to Mach 9, a blistering nine times the speed of sound. What’s more, the engine uses aviation kerosene as fuel, which carries neither the cost nor risk of explosion that hydrogen solutions do.
Published in a peer-reviewed paper, the research states this is the first time a kerosene-based detonation engine has been publicly tested.
A detonation engine uses a chain of shockwaves to propel the aircraft forward by injecting fuel into a ring-shaped channel, before igniting it to form a controlled explosion. The shockwave then ignites the next round of fuel injected into the channel, creating a cascade of detonations that self-sustain themselves while the combustion products are ejected out of the rear.
These engines release more energy than hypersonic alternatives, namely the scramjet that the US are investing in, and are markedly more efficient at high speeds. For carrying cargo or significant journeys, this could mean astonishing cost savings.
The tests used the JF-12 hypersonic shock tunnel, the largest shock tunnel in the world, that replicates hypersonic flight conditions. With a diameter of up to 3.5 meters (11.4 feet), the tunnel can simulate conditions from Mach 5-9, allowing the testing of hypersonic aircraft profiles and engines.
Detonation engines are not a new concept, but the dream of using aviation kerosene has posed challenges for scientists, as it burns more slowly than hydrogen. Using kerosene would require a huge chamber that is ten times longer than current hydrogen engines, and you can’t simply make things bigger when it will be travelling at close to Mach 9.
To get around this, Liu Yunfeng and colleagues from the Institute of Mechanics, Chinese Academy of Sciences, came up with an ingenious but simple solution – a tiny bump (which they call a “bulge”) in the air inlet allows kerosene to detonate more readily. As air spins round the chamber at huge speeds, it collides with the bump to create a small shockwave that helps ignite the fuel.
They tested their creation using RP-3 fuel and it was successful in creating powerful and sustained thrust.
Hypersonic flight is rapidly becoming a smaller form of the space race, with nations around the world searching for hypersonic technologies that can power missiles, passenger planes, and more. Aircraft travelling at that speed are almost unstoppable with current technology, so the appeal to create viable engines is rapidly coming to the forefront of research and development.