Until 1947, Ralph Miller, an Americ

Until 1947, Ralph Miller, an American engineer, realized the Miller cycle with high thermal efficiency by closing the intake valve in advance on the basis of a simple Otto cycle engine. Miller cycle is actually an improvement of traditional Otto cycle, not a new thermodynamic cycle. Because the intake valve closes before the lower dead center of intake, the intake stroke is shorter, so the cylinder entering the engine is less inflated, and the final engine power output is reduced. The loss of maximum output power partially offsets the improvement of thermal efficiency of Miller cycle engine. In order to ensure high power response output and high thermal efficiency, Miller further proposed to use supercharging to make up for the reduction of deflagration gas charge caused by early closing of intake valve. Because the Miller cycle is a low temperature cycle, the engine performance can be improved by increasing the knock limit.