Search Results

Most automobile manufacturers have developed hybrid vehicles that combine an internal combustion engine and an electric motor, fusing the advantages of these two power sources. For example, Toyota, in its Prius II, uses a highly efficient gasoline engine based on a modified Atkinson cycle featuring a variable valve timing management. This implementation of the Atkinson cycle is not the optimal solution because some of the air is first sucked from the intake manifold into the cylinder and subsequently returned. This oscillating air stream considerably reduces the thermal conversion efficiency of this cycle. This paper analyzes in detail the loss of thermal conversion efficiency of an internal combustion engine -especially for modified Seiliger and Atkinson cycles - and a proposal is made for the improvement of aspirated and supercharged engines.

Most recent implementations of the Atkinson cycle are not ideal from the point of view of thermal conversion efficiency ( TCE ). For example, Toyota has put a gasoline engine in its Prius II which should achieve high efficiency by using a modified Atkinson cycle based on variable intake valve timing management. Firstly, this implementation of the Atkinson cycle is not the ideal solution because some of the air is first sucked from the intake manifold into the cylinder and subsequently returned back there. Consequently, the oscillating air stream reduces the thermal conversion efficiency of this cycle to a considerable extent. Secondly, this implementation of the Atkinson cycle only reaches low levels of indicated mean pressure ( IMEP ) and, thirdly, it is not suitable for part load engine operating points ( EOP ) because of the lower TCE.

The downsizing of Internal Combustion Engines (ICE) is already recognized as a very suitable method for the concurrent enhancement of Indicated Fuel Conversion Efficiency (IFCE) and the lowering of CO2 and NOx emissions. In this report, ultra-downsizing is introduced as an even higher stage of development of ICE. Ultra-downsizing will be implemented here by means of real Atkinson cycles using asymmetrical crank mechanisms, combined with multi-stage high-pressure turbocharging and very intensive intercooling. This will allow an increase of ICE performance while keeping the thermal and mechanical strain strength of engine components within the current usual limits.

Ultra-Downsizing (UD) was introduced as an even higher level of downsizing for Internal Combustion Engines ICEs, see [2] SAE 2015-01-1252. The introduction of Ultra Downsizing (UD) aims to enhance the power, efficiency, and sustainability of ICEs while maintaining the thermal and mechanical strain within acceptable limits. The following approaches are utilized: 1 True Atkinson Cycles are implemented utilizing an asymmetrical crank mechanism called Variable Compression and Stroke Ratios (VCSR). This mechanism allows for extended expansion stroke and continuous adjustment of the Volumetric Compression Ratio (VCR). 2 Unrestricted two or more stage high-pressure turbocharging and intensive intercooling: This setup enables more complete filling of the cylinder and reduces the compression work on the piston, resulting in higher specific power and efficiency. 3 The new Load Control (LC) approach is based to continuous VCR adjustment.