Operation of a Natural Gas Direct Injection Compression Ignition Single Cylinder Research Engine

The medium and heavy-duty powertrain industry trend is to reduce reliance on diesel fuel and is aligned with continued efforts of achieving ultra-low emissions and high brake efficiencies. Compression Ignition (CI) of late cycle Directly Injected (DI) Natural Gas (NG) shows the potential to match diesel performance in terms of brake efficiency and power density, with the benefit of utilizing a lower carbon content fuel. A primary challenge is to achieve stable ignition of directly injected NG over a wide engine speed and load range without the need for a separate ignition source. This project aims to demonstrate the CI of DI NG through experimental studies with a Single Cylinder Research Engine (SCRE), leading to the development of a mono-fueled NG engine with equivalent performance to that of current diesel technology, 25% lower CO₂ emissions, and low engine out methane emissions. The SCRE has a single cylinder displacement of 2.5L and utilizes a high-pressure direct-injection gaseous injector with pilot gas injection capabilities. This is combined with technologies targeting the end-of-compression temperatures required to achieve the autoignition of late cycle injection of NG. These technologies include increased compression ratio and auxiliary charge air heating. The SCRE experimental studies have been successful in demonstrating robust ignition of DI NG, producing high efficiency, stable operation with acceptable pressure rise rates, and good combustion stability. The technology offers direct control of combustion phasing and heat release rate through injection strategy, including pilot and main injection timing and injection pressure. Studies have been conducted to expand the operating range of the SCRE and characterize the interactions of response variables to achieve high efficiency and low emissions operation at increased engine loads, with a final target of 24 bar BMEP.