Investigation into a stepped-piston engine solution for automotive range-extender vehicles and hybrid electric vehicles to meet future green transportation objectives

Abstract

Securing the objectives for future high efficiency low CO2 vehicles is a key target for automotive manufacturers. This paper considers a high durability two-stroke cycle engine in terms of performance and computational modelling of emission characteristics for automotive range-extender or hybrid electric vehicle power plant application. The engine uses novel segregated pump charging via the application of stepped pistons and the study compares the engine characteristics with a comparable four stroke cycle engine of similar expected power output (60+ kW per litre). In the interests of cost minimisation both engines are limited to parallel two cylinder in-line configurations with the intention of still being able to achieve acceptably low noise, vibration and harshness (NVH) characteristics. In order to achieve low engine exhaust emissions computational modelling of direct injection is considered for the stepped piston engine. Significant NOx emission reduction of between 31% and 55% is observed.

Low noise, vibration and harshness solutions for in-line three-cylinder range extender and hybrid electric vehicles

“…The very low NO x emission of two-stroke engines as discussed by Blundell et al 37 and Turner et al 22 has been observed with stepped piston engines, 14,23 but the implementation of variable compression ratio (VCR) technology as discussed by Turner et al 22 could further reduce NO x emission and offer even greater CO 2 reductions. HEVs and RE-EVs already readily demonstrate fuel efficiency improvements and therefore reduced CO 2 emissions but application of VCR gives further potential reduction beyond the immediately apparent benefits while also addressing the range anxiety issues of fully electric vehicles.…”

“…Most research has been performed in this area with balance shaft application with four-stroke inline three-cylinder units as the subject engine [6][7][8][9][10]. Two-stroke cycle engines for range extenders or hybrid drive train have been researched by Stan and Personnaz [11], Mattarelli et al [12], Borgi et al [13] and Hooper [14] [15]. Some researchers have considered the in-line three-cylinder twostroke cycle engine as a suitable candidate as demonstrated by the work of Duret et al [16], Schlunke [17], Cantore and Mattarelli [18], Mattarelli [19] and Mattarelli and Rinaldini [20], but none of these examples applied a balance shaft.…”

2-Stroke Engine Options for Automotive Use: A Fundamental Comparison of Different Potential Scavenging Arrangements for Medium-Duty Truck Applications

“…Other technologies which would be interesting to study in this context might be the stepped-piston concept, which could replace an external supercharger while still permitting turbocharging to be applied. This has been investigated extensively by Hooper [50,51] and also Lee [52] in a compounded engine, as well as being a feature (in inverted form) of the engine of Witzky et al [48].…”

Energy recovery from landfill gas emissions using a stepped piston segregated scavenge engine

“…This paper considers such a method of LFG combustion using stepped piston engine technology as discussed by Hooper et al, 16 Stone, 23 Hooper et al, 24 and Hooper. [25][26][27][28] Comparisons are drawn between a twin-cylinder stepped piston engine and an equivalent four-stroke twin-cylinder engine.…”