A diesel-electric hybrid helicopter using Ecomotors OPOC engines is a concept project grouped under the name of eCO2avia by EADS Innovation Works. Highly efficient electrical motors driving the rotors, combined with OPOC (Opposed Piston, Opposed Cylinder) diesel engines, reduce fuel consumption and emissions by up to 50% relative to a conventional twin-turbine powered helicopter.
The main components of this hybrid system are multiple diesel-electric motor-generator units, a pair of high-performance batteries and a power electronics unit controlling the energy flows for best efficiency. The OPOC diesel engines, designed and built by EcoMotors International in the US, offer a fuel economy improvement of up to 30% compared to today’s helicopter turbine engines.
The pistons are connected to a short crankshaft, located between the two opposed cylinders. The volume formed between the two opposed pistons is the combustion chamber. These design features are the key to an OPOC engine’s power-to-weight ratio being as high as 2 kW/kg.
From Greencarcongress – The Ecomotors opoc engine operates on the 2-cycle principle, generating one power stroke per crank revolution per cylinder. Each module consists of two opposing cylinders per module, with a crankshaft between them; each cylinder has two pistons moving in opposite directions. This design configuration eliminates the cylinder-head and valvetrain components of conventional engines, offering a more efficient, compact and simple core engine structure, the company says. The power density is more than 1 hp per pound of engine weight.
With no valvetrain, the opoc engine has 40% less friction than conventional valve-controlled engines. The engine design features 90% cylinder scavenging, a high-pressure fuel injection system, and an electrically controlled turbocharger, allowing it to run higher levels of EGR. Four features allow the opoc engine to achieve that high 90% scavenging:
* Asymmetric port timing
* Circumferential ports
* Uni-flow air charging
* Electronically-controlled turbocharging
The ECT effectively eliminates turbo lag because the electric motor provides much faster turbine response, and also provides boost when there is low energy from the exhaust flow. The motor is actuated by an electronic controller, which can be integrated with the engine control unit. When it is being spun by the turbocharger, the electric motor acts as generator, producing electricity.
While some two-stroke engines suffer from high oil consumption, the opoc engine’s oil consumption is 0.2 grams per kilowatt-hour, as compared to 0.4 grams per kilowatt-hour of a standard four-stroke engine