Development & Testing of an Expansion Chamber for the Reduction of NOx Emissions in a Two-Stroke Lean Burn Gas Engine
New national and local environmental clean air regulations mandate a reduction in NOx emissions from stationary lean burn internal combustion engines. The Ajax expansion chamber uses exhaust pulsations to optimize the scavenging of the power cylinders while providing substantial increases in the mass of fresh air that is trapped inside the cylinders. This configuration results in improved performance, cooler combustion, and reduced NOx levels. This tuned exhaust system features diverging and converging sections of pipe. The system produces a negative rapid scavenging pulse (vacuum) to facilitate the removal of residual gases from the power cylinders, followed by a large reflected positive pressure pulse to maximize the amount of fresh air that is trapped in the power cylinders. A further benefit of this apparatus is an increase in available horsepower from the engine. The control of scavenging and trapping fresh air is accomplished strictly by the shapes and lengths of the sections of the tuned exhaust system. This method of exhaust emissions reduction does not rely on any moving mechanical devices nor does it require system adjustments and maintenance to achieve the emissions reduction. This paper documents the methodology used to develop the patent pending technology used in the expansion chamber, as well as a presentation of testing results.