Compact and Efficient Drive Unit Offers Very High Power Density

Six months after unveiling the new 3W-180SRE hybrid Wankel engine at Xponential 2017, 3w-International’s CEO Karsten Schudt points to the flexibility, efficiency and wide potential applications for the unique drive unit, opening the door to new target groups in both the military and civil domains.

The engine, which has a short-engine mass of 6.8kg and features rated power of 28hp at 6,000rpm, is available in a high-power version (38.5hp at 7,500rpm) and can provide users with a 5.66hp/kg power to mass ratio with consumption of 340g/kW as a result. Add to this the ability to feed 15kW independently of the storage system capacity for periods of 30-60s and the result is a uniquely flexible and adaptable system that offers valuable optional power during a rotary wing startup, for example, or in the acceleration curve of a fixed-wing airframe.

“This hybrid system, as well as the very good power-to-mass ratio, opens up entirely new possibilities for us,” observes Schudt. Since the engine is marketed only as a complete drive unit, a number of projects are approaching completion at year’s end. “The engine must be adapted exactly to the UAS in order to optimally extract the former’s power. This time we’re working closely with our customers,” Schudt adds.

The Wankel engine provides a variety of benefits to operators. Its compact construction features moving parts and its mechanical effectiveness is thus achieved with relatively few friction losses. Compared with other internal combustion engines, displacement is small and the engine provides greater power density with both light weight and low physical volume. Consuming less fuel at high rotational speeds than Otto engines, the Wankel solution offers high power and torque with very low vibration and can operate on both gasoline and heavy fuels.

“It’s precisely the high power with low mass and consumption that render the engine especially interesting for helicopter applications,” Schudt points out. Helicopters in particular need high rotational speeds for climb and hover manouevring. “Specific requests are on the table and we assume that we’ll implement a few of them in 2018,” he confirms.

The engine is in demand both in military and civilian application areas, for example, for hovercraft applications and as a power generator for applications in the construction industry. Noise emission has repeatedly been an aspect, especially in military applications, with noise reduction for Wankel engines often being perceived as too involved, 3W-International has developed bespoke silencers in which the trap of mufflers diminishing engine power has been avoided. “This is one reason why we work closely together with our customers during the engine’s initial integration. Our customers very much appreciate the fact that they thus profit from our experience and in part realize more rapid project implementation,” Schudt concludes.

Tim Mahon