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A new concept of an engine, called a Variable R/L Engine (VR/LE) is presented. The main feature of the engine is the continuous change of the crank-radius to connecting-rod-length ratio. (R/L) during the single engine cycle. The phase shift of the R/L=f(φ), function φ being the crank angle, can be adjusted from outside of the engine and it is a regulational parameter. The variations of the phase angle result in changes of all the engine stroke lengths and also-they are causing the changes of the thermodynamic cycle of the engine. Therefore the phase angle variations make it possible to regulate continuously the compression ratio and the displacement volume of the engine within the range which depends on the engine mechanism geometry. The presented concept can be applied to all the types of the IC piston engines, independently of their size and operation principle.

A theoretical analysis of the spark ignition VR/LE engine with the variable crank-radius to connecting-rod-length ratio R/L is presented. The studies have been performed with the help of the thermodynamic-type model (zero-dimensional) including NO formation submodel. The analysis have made it possible to determine the changes of some basic output engine parameters: thermal efficiency, work and NO concentration, as a result of the engine thermodynamic cycle variations which, in turn, result from the external regulation of the phase shift of the function R/L = f(φ), where φ is the crank angle. A comparison between the VR/LE and conventional engines is presented. The ranges of the phase angle which can give the gain in efficiency and NO emission reduction are also determined. The analysis has confirmed that the VR/LE engine concept has remarkable economy potential with application to the S1 engines and it is worth performing a research with an actual engine.