TCM Reveals SFC of 0.36 Jet-A-Burning piston

Teledyne Continental Motors (TCM) has unveiled a two-engine project that will bring jet fuel to the light-aircraft industry. The first, a 230-hp four-cylinder engine is expected to be certified next year. A follow-on six-cylinder, 350-hp version could follow as soon as two years later. TCM said the engine program stems from acquired technology — but would not identify which European company the already certified engine technology came from. 
Under the license agreement with the original maker, TCM now has free rein to further develop the existing engine as it sees fit. The company has said it expects the new engines to cost not much more than their gasoline-burning counterparts in the same power range. TCM’s version is currently undergoing tests on a static test stand and in flight on a Cessna 182 Skylane. Specific fuel consumption (sfc) of the new engines is said to be in the .36 range.Specific fuel consumption, often shortened to SFC, is an engineering term that is used to describe the fuel efficiency of an engine design. It measures the amount of fuel needed to provide a given power for a given period.
SFC is dependent on the engine design, with differences in the SFC between different engines tending to be quite small. For instance, typical gasoline engines will have a SFC of about 0.5 lb/hp.h (0.3 kg/kWh), regardless of the design of a particular engine. One exception to the rule is that the SFC within a particular class of engine will vary based on the compression ratio, an engine with a higher compression ratio will deliver a better SFC because it extracts more power from the fuel. Diesel engines have better SFCs than gasoline largely because they have much higher compression ratios, the way they burn their fuel is actually less efficient.
Engine type SFC
Ramjet 1.0 lb/hp.h (0.61 kg/kWh)
Turbo-prop 0.8 lb/hp.h (0.49 kg/kWh)
Otto cycle 0.5 lb/hp.h (0.3 kg/kWh)
Diesel cycle 0.4 lb/hp.h (0.24 kg/kWh)
Otto-Compound engine 0.38 lb/hp.h (0.23 kg/kWh)
Turbocharged Diesel 0.38 lb/hp.h (0.23 kg/kWh)
Turbocharged & Intercooled Diesel 0.36 lb/hp.h (0.22 kg/kWh)
Diesel-Compound engine 0.34 lb/hp.h (0.21 kg/kWh)

Modern jet engines actually have much higher compression ratios than piston engines, which was not always the case. Whereas a good Diesel might have a compression ratio of 22:1, Rolls-Royce RB-211 developed for the L-1011 in the 1960s runs at 29:1, and the latest R-R Trent runs at 41:1. Nevertheless jets deliver considerably worse SFC, which is due to their compressors being much less efficient than a piston for most pressure ranges.

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One comment

  1. Superb site yours faithfully Elfrieda Haslinger

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