Aim of this is to present the alternative HEV (PHEV) concept, potentially more efficient than fuel-cell powertrains, which can in the same time compete with the conventional vehicles (CV) in retail prize, functionality and all drive situations!
Despite the progress of technical science the efficiency and power-output of internal combustion engines (ICE-Otto/Diesel) is still disappointingly bad:
*The Tank-to-Wheel energy efficiency …. generally less than 22% of the energy contained in diesel and 18% of that contained in petrol – the rest is lost as heat!
European Association for Battery Electric Vehicles, 2008*
Paradoxically - the inefficiency is frequently addressed on indispensable thermic losses, whereas by default its thermal efficiency depends exclusively from the compression ratio.
According to self-respiration postulation traditional ICE uses mainly four "strokes", of which — the compression stroke (high consumptive) and power stroke (high productive) are power significant. Its subtraction-principle denotes that the considerable proportion of work produced by the combustion should be cyclic-reduced by the work needed for initial adiabatic-compression of charge, whereas the compression of air takes the significant part of it.
Hereby the internal adiabatic compression (notorious dependence pressure-temperature) and its cyclic subtractive integration is holding in suspense the radical enhancement of conversion efficiency and power-output. According to exact thermodynamic calculations the compression-work wastes more than 25% by Otto, and in the case of Diesel engines more than 45% of expansion work (ideal stoichiometric conditions!).
Although the initial-compression of air is indispensable, it is not from its operational-run indivisible. So to clear the way for the significant enhancement of conversion efficiency and power output a newly ICE-Concept based on ancillary pre-compression and CAES unveils in three essential steps:
1) Introduction of ancillary pre-compression of air (100-200 x 105 Pa) by means of CAES (Compressed Air Energy Storage).
2) Introduction of compression-free two-stroke engine system. It consist of a fully-charged piston engine, parallel compounded to an exhaust turbine GT. This piston engine is similar to conventional ICE, whereas unlikely the inlet-valves are substituted with air-injectors and the piston closes the cylinder-volume at the upper dwell-point theoretically to zero (volumetric efficiency=1).
Its operational-run introduces the principle of work-addition (work cumulation = pneumatic work + expansion work + recuperation work) - granted thus with high efficiency and power output.
3) Modular aggregation of ancillary units by means of HEV interface. The already coexistent electric drive of HEV-s (supported additionally with electricity produced by exhaust turbine GT) is here used for pre-compression of air – it closes in the same time the needed energetic system-balance!
Under physical lows being considered - the concept can radically increase the efficiency (>60%) and power-output (>400 kW) of future powertrains. Versatile aspects and technological obstacles of newly engine concept are being progressively in exploration by means of CFD simulations on University-Split/Croatia. The theoretical revisions of its physical-principle performed by means of Ricardo-WAVE* simulations have already confirmed the huge-potential in enhancement of conversion efficiency (>2X) and power output (>4X) compared to contemporary combustion engines (University Split - FESB, Prof. Ph.D. G.Radica/Croatia*).