GUY NORRIS / LOS ANGELES
Powerplant is potentially ideal for missile and unmanned combat air vehicle applications
Pratt & Whitney has submitted proposals to the US Navy for a further round of pulse detonation engine (PDE) tests, including development of a hybrid turbine/PDE engine configuration to power a next-generation supersonic anti-ship and ground attack missile family.
The proposals come on the heels of a successful second round of tests of a five-tube conceptual PDE at the US Naval Air Weapons Center's T-Range test site in China Lake, California. Data from the tests, which were completed on 19 December, is still being assessed, but the company says "everything we tested ended up being close to predictions".
The latest test phase included evaluation of a compound nozzle that combines the exhaust flow from all five PDE tubes and is more representative of a production concept. PDE technology, however, is "still immature", says P&W, which describes it as being at a technology readiness level (TRL) of 3 to 4, rather than the TRL 6 or prototype stage needed for flight tests. This is emphasised by the pre-ignition issues experienced with the compound nozzle during the latest tests, adds the company, which is seeking a new round of funding from the Office of Naval Research (ONR) to continue its PDE development work.
The PDE is conceptually simple and has the potential to operate from zero airspeed to Mach 4, making it potentially ideal for missile and unmanned combat air vehicle applications. Combustion takes place in an open-ended tube in which fuel is mixed with air and detonated. As the detonation wave travels down the tube at supersonic speed, a refraction wave propagates into the combustor and exhaust products leave the chamber. Pressure in the chamber drops, drawing in fresh fuel and air, and the cycle is repeated. Each pulse lasts only milliseconds.
If ONR funding is approved, P&W plans to run tests on a full series of subsystems as well as possibly continue running the five-tube trials. It will also include configuration development of the hybrid engine, which replaces the gas generator section of a turbojet with the PDE. P&W is already involved in early work in hybrids through NASA's RASER programme while the US Air Force is considering the technology as part of its Versatile Affordable Advanced Technology Engine effort.
The hybrid is expected to have a 10%-plus fuel consumption advantage over conventional turbojets, and could provide payload and range advantages - particularly in a missile application.
Source: Flight International
