Initial Results on a New Light-Duty 2.7-L Opposed-Piston Gasoline Compression Ignition Multi-Cylinder Engine

Abstract

Gasoline compression ignition (GCI) is a cost-effective approach to achieving diesel-like efficiencies with low emissions. The fundamental architecture of the two-stroke Achates Power Opposed-Piston Engine (OP Engine) enables GCI by decoupling piston motion from cylinder scavenging, allowing for flexible and independent control of cylinder residual fraction and temperature leading to improved low load combustion. In addition, the high peak cylinder pressure and noise challenges at high-load operation are mitigated by the lower BMEP operation and faster heat release for the same pressure rise rate of the OP Engine. These advantages further solidify the performance benefits of the OP Engine and emonstrate the near-term feasibility of advanced combustion technologies, enabled by the opposed-piston architecture. This paper presents initial results from a steady state testing on a brand new 2.7L OP GCI multi-cylinder engine designed for light-duty truck applications. Successful GCI operation calls for high compression ratio, leading to higher combustion stability at low-loads, higher efficiencies, and lower cycle HC+NOX emissions. Initial results show a cycle average brake thermal efficiency of 31.7%, which is already greater than 11% conventional engines, after only ten weeks of testing. Emissions results suggest that Tier 3 Bin 160 levels can be achieved using a traditional diesel after-treatment system. Combustion noise was well controlled at or below the USCAR limits. In addition, initial results on catalyst light-off mode with GCI are also presented.

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

“…In addition to small scale prototypes a full-scale engine has been built by a development team at Achates Power Inc. Developments are made both is diesel and gasoline CI technologies (Abani et al 2017;Pirault, Flint 2010;Redon et al 2014;Salvi et al 2022). The developers have also initiated initial road tests in heavy-duty trucks (Fromm 2022).…”

“…The higher TE of an OPE stems from a lower surface area for heat losses, relative to the cylinder volume (Abani et al 2017;Redon et al 2014;Salvi et al 2022). 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.…”

“…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).…”

“…The 2-pistons per cylinder allow for longer travel along the cylinder without compromising engine top speed or the need for a crankshaft with a long stroke. The longer stroke per cylinder helps with cylinder scavenging, increased air flow, air/fuel mixing and extends the expansion of combustion gasses (Abani et al 2017;Pirault, Flint 2010;Redon et al 2014;Salvi et al 2022).…”

Numerical optimization of supercharging and combustion on a two-stroke compression ignition aircraft engine

“…2S engines have demonstrated to be able to reach very high brake thermal efficiencies: the big naval CI engines can easily exceed 50%, 5 and a new generation of light duty opposed piston engines is targeting this figure, running on both Diesel fuel and gasoline [6][7][8][9] Clearly, loss of fuel at the exhaust must be absolutely avoided, and a proper lubrication should minimize friction between the moving parts: unfortunately, these conditions cannot be obtained with conventional highspeed SI 2S engines, adopting a crankcase pump. In a typical aircraft application with a brake power target higher than 110 kW, air is delivered to cylinders by means of a turbocharger, supported by a supercharger during transient operations and for starting the engine.…”