European supersonic engine researchers completed a Mach 2 scramjet study last month and concluded that combustion in a super-fast airstream is similar to that in spark ignition engines and that computational models must change.

The similarity with spark ignition lies in the fact that supersonic combustion operates on the principle of constant volume, not constant pressure.

The discovery means a new physical model must be used in computational fluid-dynamics (CFD) analyses to better reproduce the mixing and combustion process in a scramjet.

Although aerodynamics and aerostructures have been the focus of CFD for many years, combustion has been a much more complex and difficult computational task and much more research is needed.

“As air within the combustor flows at over Mach 1, mixing and combustion are critical issues,” says Antonella Ingenito of the University of Rome’s department of mechanics and aeronautics. Because combustion lasts a millisecond, hydrogen is the best fuel because its kinetic properties mean it can combust quickly enough, she says.

Source: Flight International