As every pilot and mechanic knows, high temperatures are the bane of any engine. But as engineers strive to design smaller, more powerful turbine engines by adding compressor stages, the compression ratio goes up and so does the temperature of the ram air. At a compression ratio of about 20 to 25, ram-air cooling becomes inefficient. The solution, researchers believe, lies with cooling the air before it goes into the combustor.
Jet fuel derived from coal successfully powered a Rolls-Royce T63 turboshaft engine recently at Pennsylvania State University. According to a Penn State scientist, tests have shown that the fuel mix can go to at least 75 percent coal and the end product meets or exceeds all specifications for JP8 and jet-A and has a higher flash point.