The German engine manufacturer 3W-International is expanding its range of drive products for UAVs by a further engine sector. Just as the two-stroke engines already in use in the marketplace, the new 3W-180 SRE Hybrid Wankel engine can be fuelled by petrol or kerosene, too.
“In the past, many interested parties at trade fairs and congresses have asked us about Wankel engines,” Karsten Schudt, Managing Partner of 3W-International, recalled. For this reason, Schudt and his development team decided to expand the product segment with Wankel engine technology. In doing so, it was clear right from the start that the new engines had to fit in with the philosophy of 3W-International.
“We wanted a high-quality, fuel consumption-optimised engine which would demonstrate an outstanding power-to-weight ratio,” Schudt continued.
The 3W-180 SRE Hybrid has 180 ccm and as a short engine weighs 6.8 kilogrammes. In the high power version, at 7500 rpm it delivers 38.5HP (nominal power 28HP at 6,000rpm). From this there results a power-to-weight ratio of 5.66HP/kg, with a fuel consumption of 340g/KW at full load.
The weight rises to 9.5kg when the engine is fitted with an electric motor (starter generator). The generator also charges the super capacitors which turn the Wankel engine into a hybrid drive. Super capacitors are well-suited to hybrid applications in aviation due to their weight and fast charging and discharging behaviour.
“We are very proud that we are able to offer our customers an additional service with this modern and sustainable technology which is available at short notice,” Schudt was pleased to say.
The hybrid Wankel engine can feed 15KW, depending on the capacity of the storage system, into the system for a time (for example, 30-60 seconds). This additional power can be used when starting a helicopter or for the acceleration of a fixed wing aircraft. “Thus our customers always have a power reserve on call,” Schudt confirmed.
The 3W-180 SRE Hybrid is equipped with two independent cooling systems. A water cooling circuit undertakes the cooling of the engine housing, a second, oil cooling circuit, undertakes the internal cooling of the piston. This is a fundamental prerequisite for a drive system in aviation applications for which continuous power is also a fundamental prerequisite. Here the thermal stability, which gives added value to the 3W-180 SRE Hybrid, is of crucial importance.
In a further expansion stage, the Wankel engine can also be equipped with two drive pulleys. Through the doubling of the swept volume, the power of the naturally aspirated engine is doubled to 76HP in the high performance variant with a short weight of 10.5 kilogrammes. This engine variant is also intended as a hybrid version. In the future, a variant with a turbocharger which is primarily intended for height compensation will also be offered. “We can also supply the Wankel engine as a complete drive unit similar to our two-stroke engines. This means that the customer receives the engine equipped with all additional systems completely in accordance with his individual requirements,” the industry executive explained.
In accordance with the engine philosophy of 3W-International, the 3W-180 SRE Hybrid can be used as a petrol or as a Heavy Fuel (HF) engine. As an HF engine, the fuels JET A-I, JP-5 or JP-8 can be used. "For the HF versions we provide high performance fuel injection which leads to a further reduction in fuel consumption," explained Schudt. For petrol operation, intake manifold injection is provided for the fuel injection.
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