Pratt and Whitney says the new development bi-metallic 18-blade fan for the PW1524G geared turbofan engine for the Bombardier CSeries is demonstrating "double-digit" performance level margins in initial engine-level testing underway at the company's West Palm Beach, Florida test facilities.

The results are part of a comprehensive battery of tests on the first of eight production configuration 24,000lb-thrust (107kN) turbofan engines to be used for internal evaluations and an 18-month certification program slated to be complete in 2012. Bombardier plans to certify the first CSeries variant, the 110-125 seat CS100, in 2012 with deliveries following in 2013.

Engine one's primary purpose is to investigate low spool (fan, low pressure compressor and low pressure turbine) performance, a task that requires the measurement of nearly 3,000 parameters during approximately 100h of testing.

As of 29 November, engine S/N001 had accumulated 80h of the "first order performance" runs and tests were expected to be completed by mid-December. Bob Saia, P&W vice-president next-generation product family, says the tests are typically run every other day.

PW1524G web 
 ©Pratt & Whitney

Though overall engine performance measurements are not possible due to the presence of the test equipment, including a fan nozzle with flapper valves and internal thermocouples and stress gauges, Saia says performance at the module level is representative. The flapper valve arrangement allows engineers to simulate various pressure conditions on the fan, including normal operations at altitude or the backpressure brought on by a surge.

The low pressure spool represents a large amount of new technology for P&W, starting with the fan. Whereas the geared turbofan demonstrator engine trials from 2008 used a titanium fan, the company moved to a lighter weight bi-metallic with a titanium-sheathed leading edge rather than a composite blade for the production geared turbofan engines. "We found it had the same weight as composite but has the significant benefit of making the blade thinner," Saia says. "It has better [aerodynamics] and still meets bird ingestion requirements."

While P&W had earlier measured fan aerodynamics on the titanium demonstrator engine and performed bird ingestion and blade out tests on the fan by itself running at red-line speed in a test rig, the ongoing S/N001 tests are the first performance testing of the new fan in the "engine environment," says Saia. "Performance looks very good" and matches that of the demonstration engine, he adds.

"We've done flutter and operability testing at elevated pressure at a given airflow," Saia says. "We're seeing double digit margins, which is above the design requirement."

The company on 29 November was preparing to begin distorted inlet testing, where the air inlet orientations are modified to simulate and angle of attack in the airflow to analyze fan performance.

P&W has also completed "a full survey" of the oil lubrication system and fuel management system on S/N001 including the fan gear drive system, which spins the fan at approximately one-third the speed of the low pressure turbine.

"We have not uncovered anything that tells us we need a major design or architecture change," says Saia.

Meanwhile test engine S/N002, which will be instrumented for high spool date (high pressure compressor and high pressure turbine), and S/N003, which will fly on the company's Boeing 747 testbed, are being assembled and will go into test "early" next year, says Saia. Assembly of S/N004, which will be used for endurance testing, starts in early 2011.

Source: Air Transport Intelligence news