Comparison of the structure of diffusion flames of the mixtures of CNG with hydrogen

Abstract

A comparative study of the flame structure and characteristics of diffusion flames of the mixtures of compressed natural gas (CNG) with hydrogen in a coflowing stream of air is presented. The volumetric content of natural gas in the fuel mixture was varied between 0 to 35%. The jet exit Reynolds number was varied from 150 to 3000. Measurements included flame length, radiative fraction of heat release, emission indices of NO, NOx, and CO, and in-flame temperature and composition profiles. Results indicate the following: The increase of natural gas concentration in the hydrogen-natural gas mixture increases both the flame luminosity and flame length., increases the radiative heat-loss fraction and soot concentration, monotonically decreases both NO and NOx emission, increases the CO emission index, and decreases the peak temperature in the near-burner, mid-flame, and farnozzle regions.