GUY NORRIS / LOS ANGELES
Six-cylinder version of general aviation propulsion diesel engine could follow four-cylinder version for NASA
Teledyne is evaluating development of a six-cylinder version of the general aviation propulsion (GAP) advanced technology diesel engine, built in a four-cylinder configuration for the NASA-led programme.
The horizontally opposed, direct-drive engine would be turbocharged and fuelled by Jet A. "The power-to-weight ratio for a six-cylinder version is more attractive than a two-stroke," says chief technology officer John Barton, and would be rated at 220kW-245kW (295-440hp).
A key element of the study is an expansion of the complex machining technology that enabled the GAP engine to be made from a monoblock combining the crankcase, cylinder barrels and cylinder heads into a single aluminium element. Two monoblocks would be bolted together along the crankshaft centreline to form the engine, which will have 60% of the parts count of its conventional equivalent. The bigger version would not be configured with individual cylinder heads, and the pistons would run in cast-iron cylinder liners pressed into the aluminium casing.
Teledyne's target for the powerplant is an installed weight within 5% of a conventional piston engine. Barton adds that the engine is aimed "mainly at US airframers looking to partner a project for use overseas. Domestically, the use of this engine is not yet as compelling as for the overseas market."
No specific timescale has been decided, and an outline schedule could be agreed by the first quarter of next year. Teledyne believes the enhanced 3,000h time-between-overhaul durability of the diesel engine, which operates at a lower temperature than a normal piston engine, together with 25% lower fuel consumption, add up to around a 50% lower life-cycle cost.
Although NASA funding for the programme ceased last year, Teledyne is still testing the GAP engine, and is evaluating cold-starting and alternative fuels. "We're looking at the possibilities of mis-fuelling so we know what will happen in the real world with rough-and-ready handling," says Barton.
Source: Flight International
