Ultra-Downsizing of ICEs Based on True Atkinson Cycle Implementations. Thermodynamic Analysis and Comparison on the Indicated Fuel Conversion Efficiency of Atkinson and Classical ICE Cycles

Abstract

<div class="section abstract"><div class="htmlview paragraph">Ultra-Downsizing (UD) was introduced as an even higher level of downsizing for Internal Combustion Engines ICEs, see [2] SAE 2015-01-1252.</div><div class="htmlview paragraph">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: <ol class="list nostyle"><li class="list-item"><span class="li-label">1</span><div class="htmlview paragraph"><b>True</b> 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).</div></li><li class="list-item"><span class="li-label">2</span><div class="htmlview paragraph">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.</div></li><li class="list-item"><span class="li-label">3</span><div class="htmlview paragraph">The new Load Control (LC) approach is based to continuous VCR adjustment. By adjusting the VCR without resorting to excessive throttling or external Exhaust Gas Recirculation (EGR), a stoichiometric Air Fuel Ratio (AFR) can be maintained. This facilitates easier exhaust gas aftertreatment using a three-way catalyst.</div></li><li class="list-item"><span class="li-label">4</span><div class="htmlview paragraph">Fuel Flexibility: The continuous VCR adaptation capability enables the engine to operate in multi-fuel mode. In addition to gasoline or diesel, the engine can also run on alternative fuels like pure hydrogen (H₂) or H₂ blended with gases like CNG, Biogas, e-fuels, or even ammonia (NH₃). This versatility allows for reduced carbon emissions and increased sustainability.</div></li></ol></div><div class="htmlview paragraph">By combining these approaches, the UD concept aims to achieve higher power output, improved efficiency, and reduced environmental impact in ICEs, all while ensuring the durability and strength of engine components remain within acceptable limits.</div><div class="htmlview paragraph">The thermodynamic analysis is done separately for <b>ideal</b> and <b>real</b> cycles in order to determine the Indicated Fuel Conversion Efficiency (IFCE), formulaically (for ideal cycles) and quantitatively (for real cycles).</div><div class="htmlview paragraph">AVL BOOST © is used to simulate the <b>real</b> cycles (within cylinder and turbocharger) and MATLAB © to process the simulation results.</div></div>