The Effect of Crankshaft Phasing and Port Timing Asymmetry on Opposed-Piston Engine Thermal Efficiency

Abstract

Opposed-piston, two-stroke engines reveal degrees of freedom that make them excellent candidates for next generation, highly efficient internal combustion engines for hybrid electric vehicles and power systems. This article reports simulation results that explore the influence of key control and geometrical parameters, specifically crankshaft phasing and intake and exhaust port height-to-stroke ratios, in obtaining best thermal efficiency. A model of a 0.75 L, single-cylinder opposed-piston two-stroke engine is exercised to predict fuel consumption as engine speed, load, crankshaft phasing, intake and exhaust port height-to-stroke ratios, and stoichiometry are varied for medium-duty truck and range extender applications. Under stoichiometric operation, optimal crankshaft phasing is seen at 0–5°, lower than reported in the literature. If stoichiometric operation is not mandated, best fuel consumption is achieved at an air-to-fuel equivalence ratio λ = 1.25 and 5–10° crankshaft phase angle, enabling a ~10 g/kWh (~4%) improvement in average brake-specific fuel consumption across medium-duty truck operating points. In range extender form, the engine provides 30 kW output power in accordance with a survey of range extender engines. In this role, there is a clear distinction between low-speed, high-load operation and vice versa. The decision as to which is more appropriate would be based on minimizing total owning and operating cost, itself a trade-off between better thermal efficiency (and thus lower fuel cost) and greater durability.

Comprehensive Review of Innovation in Piston Engine and Low Temperature Combustion Technologies

“…The 1st of these OPE had longer connecting rods to connect pistons mounted on top of the engine cylinders to the single crankshaft situated in the lower part of the engine. One such engine, built by Gobron-Brillié, was able to propel the 1st car over the 100 mph mark; more modern versions having 2 crankshafts were widely used in aviation (Figure 7), military equipment, and transport well into the 1st half of the 20th century but started to fade away and eventually falling out of use (Gregório, Brójo 2018;Pirault, Flint 2010;Young et al 2021).…”

“…This is a result of the engine having no cylinder head as the 2-pistons are positioned at both ends of the cylinder, keeping the heat from escaping. Since the 2-pistons per cylinder move synchronously or only with a slight offset, many of the balancing issues prevalent in a conventional piston engine do not occur (Pirault, Flint 2010;Redon et al 2014;Salvi et al 2022;Young et al 2021). This and the fact that 2-stroke OPE have no need for a valve drive gives the engine even more stability and significantly reduces mechanical losses (Pirault, Flint 2010;Redon et al 2014).…”

Una revisión del uso del hidrógeno en motores de encendido por compresión (diésel) y un análisis de su posible uso en motores duales en Colombia

“…En términos físicos, esto implicaría que la llama de hidrógeno se extingue mucho más cerca de las paredes en comparación con los combustibles fósiles. Dicho fenómeno promueve un mayor calentamiento (se aumenta la transferencia de calor) del pistón, el cilindro y la culata, lo cual puede recortar la vida del motor [29]. Expandiendo el análisis, se presentaría posiblemente un fenómeno indeseado en el motor dual: la ignición de la mezcla.…”

Optimizing the fuel efficiency of an opposed piston engine for electric power generation

“…For this type of lower power, downsized, range extender or hybrid vehicle application, the opposed piston (OP) engine presents several advantages compared to the conventional ICE design. [6][7][8] First, it is important to note that in an OP engine, two pistons on separate crankshafts are aligned, facing each other in a single cylinder and make up the combustion chamber, as shown in Figure 1. The two opposing pistons are inherently balanced; therefore, engine downsizing can be achieved by reducing the number of cylinders while keeping the combustion volume per cylinder the same and heat losses to a minimum.…”

“…For this type of lower power, downsized, range extender or hybrid vehicle application, the opposed piston (OP) engine presents several advantages compared to the conventional ICE design. 6–8…”