Atkinson Cycle usully works by leaving opened the admission valve at the beginning of the compression stroke, allowing for a higher expansion ratio in the combustion that increses efficiency, but also generating a blowback of fresh air into the intake ports that reduces much of the efficiency gained.
In the proposed Inverted Atkinson Cycle, the exhaust port opens again at the end of the admission stroke and keeps opened at the beginning of the compression stroke, so part of the intake air bypass the combustion cycle and is sent straing to the exhaust, allowing again for a higher expansion ratio that increases efficiency but without blowback into the intake port. There is a second benefit as this bypass air collects heat from the cylinder before leaving by direct contact with the walls and valves, cooling the combustion chamber.
The operation of this cycle requires direct injection of fuel, that is standard in Ford Ecoboost Engines, as part of the intake air bypass the combustion cycle. As the engine chamber is cooler at the start of each combustion cycle, the maximum temperature is also lower, avoiding the requirement of a NOx Catalyist and allowing the operation in lean combustion conditions, further increasing efficiency.
In turbo or supercharger engines, as Ford Ecoboost, the effect of the turbine/supercharger is cooling the engine by increasing the bypass ratio of air that goes straight to the exhaust, instead of increasing the pressure in the intake air. As much of the waste heat would be removed by operation of the turbine, the cooling system can be downsized thus simplifying the engine and further increasing efficiency. Also, as the pressure is not incresed, most of the disadvantages of turbo engines dissapear, as there is not necessity of intercooler in the intake port or reducing the compression ratio in the engine, or reinforcing the engine.
The cycle operates by opening againg the exhaust valve at the end of the admission stroke and leaving it opened at the beginning of the compression stroke.
This operation allows for a higher expansion ratio that increases efficiency, but not generates a blowback of fresh air into the intake port, but a bypass into the exhaust port.
The bypass generates and extra cooling of the combustion chamber, reducing its temperature and avoiding the generation of NOx
In turbo engines, the effect of the cycle is increasing the bypass ratio of fresh air and therefore the cooling of the engine, reducing the requirements of the cooling system.
Compared with standard EcoBoost engines, the proposed system would be:
More efficient, as compression and expansion ratios would be higher.
More simple, as there would be no NOx Catalyst and no intercooler, and the cooling system would be downsized. Also, thermal and pressure loads of the engine would be lower.
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