Project number: MT-15-01

Funding source: Caltrans

Contract number: 65A0533

Funding amount: $89,991

Performance period: 8/15/2015 to 8/14/2016

Project Description

The goal of the investigation was to determine the feasibility of using a humid air system for reducing NOx emissions of CNG engines. Humid air system or fumigation has been an effective approach in reducing diesel NOx emissions. In this method, water vapor is injected in the intake air supplied to the engine cylinders. The process reduces the local temperature in the cylinder and raises the specific heat of the air-fuel mixture which also contributes to the elimination of the hot spots in the engine's cylinders. With decreased temperature, NOx reduction is achieved. With an optimized system, fumigation could reduce NOx emissions without significant increases in hydrocarbon emissions. Other benefits of this process include longer life of the engine components due to reduced cycle temperature and reductions in carbon deposits.