Canada’s National Research Council (Hall 4 Stand C18B) has been flight-testing its Dassault Falcon 20 fueled by biofuel while sampling the exhaust using a probe fitted to a Lockheed T-33 chase plane. The NRC believes the exercise to be a world first.
The flights took place in May and June this year and pushed the mix 10 percent beyond the certified 50/50 blend of fossil fuel and the biofuel, which is produced from a new, domestically grown feedstock crop derived from Brassica carinata. Agrisoma Biosciences optimized and grew the oilseed for aviation use, and Honeywell UOP made the fuel from the oilseed. Flights at an even split and at a ratio of 60-percent bio and 40-percent fossil were made under various conditions.
The T-33 pilots took up formation on the Falcon to position the old trainer’s wing-mounted sensor pods in the slipstream of the Falcon. “The T-33 flies about 1,000 to 2,000 feet in trail and measures the whole wake of the Falcon,” Stewart Baillie, director of the flight research lab at the NRC Institute for Aerospace Research, Ottawa, told AIN. “The Falcon is not that heavy, and the T-33 is a robust old airplane, so we can get pretty close too–about a wingspan separation.”
Preliminary results of the sampling indicate that “particulate emissions, includingaerosols of black carbon, sulphates and by-products of the combustion of aromatic compounds,are significantly lower from biofuels than from jet-A1.”Analysis continues. What’s more, said Baillie, the performance of the Falcon 20 operating on biofuels was essentially the same as operations under jet-A1 on the ground, in cruise and during in-flight engine restarts. “The use of the biofuels did not demand any change to our ground handling, fueling or fuel system or engine maintenance practices.”
The feedstock crop used for the biojet fuel was grown in the summer of last year by Agrisoma Biosciences with the support on the NRC’s plant biotechnology expertise. This crop has all the features necessary to make it a sustainable energy feedstock crop, according to the NRC. “It is a nonfood, industrial oilseed, uniquely suited for production in semi-arid areas unsuitable for food oilseed production, with excellent agronomic characteristics,” the council said.
Brassica carinata is a “hardy plant, a type of mustard, almost like a weed in that it grows where other crops could not grow, and it’s got some interesting characteristics right at the molecular level that allow it be a particularly effective fuel feedstock,” noted Baillie.
NRC is also supporting work on icing research, among other things. A Montreal-based company called Newmerical Technologies International has taken out a license to use the NRC’s patented system for predicting the shape and structure of ice accretions that can affect flight safety. Baillie said, “This ‘morphogenetic’ modeling technology can simulate the formation of rough and discontinuous ice structures and predict ice accretion density and ice surface roughness. It is the only numerical algorithm that inherently covers the prediction of all types of ice formation under changing atmospheric conditions. The technology can predict realistic-looking, three-dimensional icing structures called ‘lobster tails’ that form on swept wings, and it can emulate the formation of runback ice accretions and rivulet structures that might occur on wings downstream from an anti-icing system. The technology has potential applications for a wide variety of aircraft, including airliners, business jets and general aviation.”
As part of a joint research project with collaborators NASA, the U.S. Federal Aviation Administration and Transport Canada, NRC researchers are also continuing to work at advancing the fundamental understanding of ice crystal accretion in the engine core, this time in relation to humidity. As part of the same research, the NRC also confirmed the importance of ice crystal size to the process of ice crystal accretion in the engine core.
“Many jet engine power-loss events have been observed since 1990 at altitudes above 23,000 feet/7,000 meters, usually considered to be the upper limit for the altitude at which water droplets can exist in liquid form,” according to the NRC. “These events, which have typically occurred in the anvil region of deep convective systems at tropical latitudes, have included engine rollback, flameout and stall, as well as damage to the low-pressure compressor from shed ice.”
A comprehensive review of 46 power-loss incidents since 1990 has built a general belief that such events result from atmospheric ice crystals entering the engine core, partially melting and then refreezing on internal components. This project, conducted in collaboration with Boeing, to prove that ice crystals could form in an aircraft engine at temperatures above the melting point of ice “represented a significant step forward in the understanding of how ice builds in aircraft engines under ice crystal conditions,” said Baillie. Certification standards in North America and Europe will start to evaluate the ability of commercial jet engines to eliminate or withstand this type of ice build-up beginning this year, and current research data from the NRC and its collaborators will inform these regulatory bodies.
The NRC has recently improved its 22.5-inch, altitude-icing wind tunnel, used for developmental and certification work with small models, wing sections and so on, to make it more responsive to client needs. The addition of a second vacuum pump to the tunnel allows researchers to simulate flight at altitudes as high as 25,000 feet, a significant improvement over the tunnel’s previous ability to simulate flight at 5,000 feet under normal icing conditions.
This article was amended at 4 p.m. on July 11, 2012, to include the involvement of Honeywell UOP in the production of the jet fuel used in the NRC's inflight emissions tests.