US company to demonstrate high-pressure turbine that can cope with high temperatures

Pratt & Whitney is to develop a ceramic high-pressure turbine under a US Army programme to demonstrate technology for an unmanned air vehicle (UAV) engine. The army's Aviation Applied Technology Directorate plans to demonstrate the 370kW (500shp) heavy-fuel engine by 2007, aimed initially at the A160 Hummingbird rotary-wing long-endurance UAV, but with growth to power the planned Unmanned Combat Armed Rotorcraft (UCAR).

Under a 39-month, $2 million cost-sharing contract, P&W and the United Technologies Research Center (UTRC) intend to demonstrate a ceramic turbine that can operate at high rotor-inlet temperatures without cooling. The team plans to employ ceramic technology used in automotive superchargers to produce a durable integrally bladed rotor.

The targets of a 20% reduction in specific fuel consumption and a 50% improvement in power-to-weight ratio for the engine require higher temperatures that cannot be reached with metallic technology, says ceramic turbine programme manager Aavo Anto, because the blades are too small to be cooled. The turbine is 180-200mm (7-8in) in diameter, with blades less than 15mm long.

The programme will use a silicon nitride material developed for the automotive industry to produce the monolithic ceramic turbine. P&W and UTRC will also demonstrate barrier coatings to protect the turbine from moisture and erosion as well as a proprietary way to attach the ceramic rotor to a metallic shaft, says Kevin Farrell, general manager small military engine programmes. Rig tests are planned for 2005.

The technology could also be applied to gas turbines in the 225-595kW range used as vehicle engines or ground power units, says Farrell. Programme goals include a 35% reduction in production and operating and support costs relative to comparable engines available today.

Source: Flight International