Design and experimental development of a compact and efficient range extender engine

Abstract

The paper reviews the design and experimental development of an original range-extender single-cylinder two-stroke gasoline engine, rated at 30 kW (maximum engine speed: 4500 rpm). The goal of the project is to get most of the benefits of the two-stroke cycle (compactness, high power density, low cost), while addressing the typical issues affecting the conventional engines of this type. Among many recent similar propositions, the peculiarities of this engine, besides the cycle, are: external scavenging by means of an electric supercharger, piston controlled scavenge and exhaust ports (no poppet valves), gasoline direct injection (GDI), and a patented rotary valve for the optimization of the scavenging process, of the loop type. Lubrication is identical to a conventional four-stroke engine, and the rotary valve, connected to the crankshaft, helps to improve the balance of the piston reciprocating forces, yielding an excellent NVH behavior. It should be noted that, except the patented rotary valve, all the engine parts are standard automotive commercial components, that don’t require any specific expensive technology. In fact, the originality of the engine consists in the optimum combination of existing well assessed concepts.\ud \ud The scavenging and combustion systems of the engine are developed in the first phase of the project, including the construction and the experimental testing of a prototype. In the second phase, the air metering system of the prototype is completely modified: the piston pump is replaced by an electric supercharger, and engine load is now controlled by the supercharger speed, without throttle valve.\ud \ud The new engine is compared to a standard 4-stroke engine, developed in a previous project for the same application. The main advantages of the two-stroke engine may be summarized as follows: lower weight (−35%), higher brake efficiency (+6%, on average), less heat rejected (−18%), lower thermal and mechanical loads within the cylinder (−40%). The only concern, that will be addressed in a future phase of the study, is the compliance with very low NOx limits: in the worst scenario, the 2-stroke engine could be forced to adopt a well assessed but expensive after-treatment device

A Review of Range Extenders in Battery Electric Vehicles: Current Progress and Future Perspectives

“…The use of ICE in REEVs has been a point of focus for many research and development groups, in both academic and industrial settings. Borghi et al [27] reviewed the design and experimental development of an original range-extender single-cylinder two-stroke ICE, rated at 30 kW with the maximum engine speed of 4500 rpm, and addressed the typical issues affecting conventional engines of this type. The new engine was also compared to a standard four-stroke engine.…”

Combustion optimization for fuel economy improvement of a dedicated range-extender engine

“…Thus, the engine's torque level and torque response at low speeds are less important for the RE engine, and the peak power requirement can be also decreased. 20,21 For example, a 30 kW RE can meet the power requirement of an REEV with a curb weight of 1600 kg cruising at 120 km/h. 22 The reduced performance requirement and narrowed operating range offer an opportunity to re-optimize or simplify the design of a dedicated RE engine, and to further improve its fuel consumption and cost effectiveness.…”

Low noise, vibration and harshness solutions for in-line three-cylinder range extender and hybrid 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.…”