April 2006 was the most recent time that this blog mentioned OPOC (Opposed-Piston, Opposed-Cylinder) engines. These are ICE (Internal Combustion Engines) that can deliver a large amounts of power in small packages.
Green Car Congress relays word from the ARPA-E Energy Innovation Summit in Washington DC (March 2010) that EcoMotors International, a Khosla-funded start-up, showcased a 100mm cylinder bore, base module.
“The 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. The fully balanced opoc engine can run on any liquid fuel.”
Since such development occurs at a time when European emission standard for a large goods vehicle will be less than 1.5 grams of CO2 per kW-hr, the EcoMotors design “features 90% cylinder scavenging, a high-pressure fuel injection system, and an electrically controlled turbocharger, allowing it to run higher levels of EGR (Exhaust Gas Recirculation).” Another way to increase efficiency is no valvetrain. “The opoc engine has 40% less friction than conventional valve-controlled engines.”
Four features allow scavenging as high as 90%:
- Asymmetric port timing
- Circumferential ports
- Uni-flow air charging
- Electronically controlled turbocharging
The electrically controlled turbocharger (ECT) incorporates an electric motor into the turbo assembly. In essence, it provides a supercharger, driven by the electric motor, as an adjunct to the exhaust-driven turbocharger. Boost pressure can be created by the electric motor, the turbocharger, or both.
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.
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