Eurocopter is here exhibiting its “Bluecopter” diesel engine concept on the static display. The so-called “high-compression engine” is supposed to bring greener performance to light helicopters currently powered by a single turboshaft. Targeted are a 40-percent cut in CO2 emissions and a 53-percent reduction in NOx emissions.
The main challenge, however, is weight. A 30-percent reduction in specific fuel consumption translates into a 40-percent cut in carbon monoxide emissions (measured against distance), according to Eurocopter calculations.
Pollutant emission reduction apparently requires a significant volume of ducts.
Exhaust gases go through an oxidizing catalytic converter, targeting carbon monoxide and unburned hydrocarbons, and through a filter that retains particulates.
Finally, they pass through a selective catalytic converter that eliminates most remaining nitrous oxides, reducing them into nitrogen and water. Car maker Mercedes participated in building the engine on exhibit. According to Eurocopter, this technology can be applied to unmanned vehicles and auxiliary power units.

An expert at a turboshaft manufacturer previously told AIN that weight is the main challenge to using a diesel engine because they are four times heavier than a turbine engine for a given power. However, unlike a turbine engine, a diesel engine’s power is almost unaffected by outside air temperature, so there is no need to oversize it. Moreover, recent technology improvements are yielding better power-to-weight ratios.

Finally, a key issue is torque oscillation. The main gearbox of a helicopter does not cope very well with such oscillations because a turboshaft has a much more constant torque than a diesel engine.