Guy Norris/LOS ANGELES
AlliedSignal could launch the full scale development of its new centreline turbofan by mid-1998 if negotiations with unidentified regional and business aircraft manufacturers succeed.
The engine, if launched, will be based on a technology validation test (TVT) core now running at AlliedSignal's site in Phoenix, Arizona.
"A lot depends on the market" says T K Kallenbach, director of new engines at AlliedSignal. "The technology demonstrator is designed to provide a launch pad for a new centreline engine, and to provide validation for new technology that could be used on our existing TFE731 and LF507 engines."
The TVT forms the basis for a new engine family, believed to be called the AS900 series. The 36kN (8,000lb) thrust AS908 version is probably a leading candidate for initial launch this year, although AlliedSignal declines to comment on this.
Chief contenders for the engine are thought to include a new mid-size business jet which Bombardier plans to launch by the end of 1998, and possibly a revamped Avro RJ85/100 regional jet family.
The core has now completed initial full power tests. The configuration is "not based on any existing core and is aimed at optimal performance at low cost," says Kallenbach. It comprises three axial compressor stages and a single centrifugal compressor stage with a single high pressure (HP) turbine stage. The compressor is made up of integrally bladed rotors.
After 6h of core tests, Kallenbach says: "We're pleasantly surprised at how well it is running. It has very good starting characteristics and is a robust design. We've had surge free operation and a temperature margin of 150íF [83íC] in the core."
AlliedSignal say tests show a TVT derived engine is on target to meet ownership goals 10-20% lower than current engines.
A fan rig test will be run by the end of June, while work on the core and three other component rigs is set to continue throughout the rest of the year. In additional tests due to begin soon, ram air will be injected into the inlet to simulate a full engine with a low pressure section.
True tests of a complete engine, with a fan and low pressure turbine, will take place with full scale development tests.
Initial rig tests will focus on a 760mm-diameter wide chord, an integrally bladed set of fan rotor blades and a composite full-span stator. Other fans designed for the family range up to a diameter of 915mm, producing bypass ratios from 4.0 to 5.5 and thrust levels from almost 18kN to 40kN.
Despite the potential of the new engine, AlliedSignal says it is continuing development of current powerplants. "We're clearly going to support and invest in the 731/507, and some of the technology for that is being checked out on the TVT," says Kallenbach.
An effusion-cooled combustor is one new technology which could find its way into the -731 family. Like other elements of the TVT, the combustor design aims at reducing operating costs and increasing robustness. The effusion cooled flow-through design has fewer nozzles than a conventional staged combustor, and is expected to show significant improvements in emissions and maintenance costs.
Source: Flight International
