Fuel Injection System for Opposed-Piston Gasoline Compression-Ignited (OP-GCI) Engines

Opposed-piston engines have been in production since before the 1930’s because of their inherent low heat losses and high thermal efficiency. Now, opposed-piston gasoline compression ignition (OP-GCI) engines are being developed for automotive transportation with stringent emissions targets. Due to the opposed-piston architecture and the absence of a cylinder head, fuel injection requirements and packaging are significantly different than conventional 4-stroke engines with central-mounted injectors. The injection process and spray characteristics are fundamental to achieving a successful combustion system with high efficiency, low emissions, and low combustion noise.

In this paper, the fuel injection system for the Achates 2.7L, 3-cylinder OP-GCI engine is described. The fuel system was designed for 1800 bar maximum fuel pressure with two injectors mounted diametrically opposed in each cylinder. Two fuel rails were mounted on each side of the engine and were supplied independently from two crank-driven unit pumps mounted at the front of the engine. CFD tools were used to investigate nozzle design and spray characteristics for minimal wall wetting and good air utilization. Simulation results indicated that relatively narrow spray angles of 10 to 30 degrees performed well. The fuel system was designed and built at Delphi Technologies and successfully tested on a dynamometer engine at Achates Power.