Atkinson Cycle and Very High-Pressure Turbocharging: Increasing Internal Combustion Engine Efficiency and Power While Reducing Emissions

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ATKINSON CYCLE AND VERY HIGH-PRESSURE TURBOCHARGING: INCREASING INTERNAL COMBUSTION ENGINE EFFICIENCY AND POWER WHILE REDUCING EMISSIONS Gheorghiu, Victor* Hamburg University of Applied Sciences Berliner Tor 21, 20099 Hamburg, Germany Keywords: Atkinson Cycle, Ultra-Downsizing, High Pressure Turbocharging, CO2 and NOx Reduction. ABSTRACT The Downsizing of internal combustion engines (ICE) is already recognized as a very suitable method for the concurrent enhancement of the indicated fuel conversion efficiency (IFCE) and lowering of the CO2 and NOx emissions [1], [2]. In this report the Ultra-Downsizing is introduced as a still higher development stage of ICE. The Ultra-Downsizing will be implemented here by means of strict Atkinson…show more content…
The performances achieved for IFCE and IMEP using this method are therefore unrealistically high and serve only as a general indication [3]. This Paper extends the previous investigations from [3] to real Atkinson cycles by using the simulation tool BOOST (AVL Co). This tool allows to take into consideration the true geometrical dimensions of the engine components (cylinder, valves, channels, pipes, manifolds, turbocharger, intercooler, silencer etc.) and the losses caused by friction and heat transfer along the intake and exhaust gas pipes. In addition, the power balance of turbochargers determines the actual boost pressure level of the engine. The turbochargers (TC) are modeled for these investigation in a simple manner. It describes the expansion process in the turbines (Tx) by means of their discharge coefficients while the air compaction in the compressors occurs up to a maximum pressure ratio, which depends on the available turbine output. To be able to simulate cycles with very high boost pressures as well, three intercooled TC are placed in line (three-stage turbocharging, see Fig. 1). When the boost pressure required for preserving the pressure limit on the cycle is low, the superfluous TC are kept in use (i.e. are not bypassed). The expansion and compression ratios of the turbines and compressors tend gradually toward 1, i.e. these TC switch off themselves thermodynamically. The asymmetrical crank mechanism used here
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