Influence of Combustion Initial Conditions on Emissions Production Rates and Released Heat for Methane Fuel Mixtures

Ali S Al-Shahrani

doi:10.4236/wjet.2017.52027

Abstract

An estimation of combustion products (pollutants) which include CO, CO2 and NO mole fraction are reported in this paper for premixed methane/air flames. Different mixtures were used in this study, including lean, stoichiometric and rich subjected to varying degrees of pressures and temperatures ranging from 5 - 40 bars and 350 - 600 K, respectively. In this work, computer software was used to calculate the produced emissions species as well as the final (adiabatic) temperatures for each mixture. Results show that rich mixture of methane fuel produces the highest rate for carbon monoxide (CO) with slight increase as pressure and temperature increase. Where the stoichiometric mixture produces the highest rate of carbon dioxide (CO2). Results showed that this type of emission decreases with the increase of pressure and temperature. On the other hand, nitric acid (NO) was found to be the highest for the lean mixture with sharp increase as pressure and temperature increase. Finally, the combustion heat (Q) for each mixture where plotted against pressure and it was found that the rich mixture of methane produced the highest rates. Results also showed that combustion heat increases sharply with increased pressures and temperatures.

Highlights

Atmospheric pollution has become a worldwide concern
Three different air-fuel mixtures have been used for methane fuel (CH4), to evaluate the amount of emissions produced in mole fraction for each combustion process
This paper starts with briefs for effects of elevated pressures and temperatures on production rates of emissions which is a major concern nowadays

Summary

Introduction

Atmospheric pollution has become a worldwide concern. This concern led to the consideration to the effects of injecting large amounts of any species on the ozone balance in the atmosphere. The aim of combustion devices of engines is to produce high temperatures for heat or power generation whilst producing the least pollutant emissions under controllable conditions. Even though premixed conditions are the aim, limited time for evaporation and mixing creates non-uniformities short in fuel concentrations In all of these situations, the final mixture will react under conditions where there is a range of equivalence ratios or mixture fractions over which the reaction will take place [5]. It becomes an essential issue to conduct researches which might help to understand the nature of such emissions, and more importantly, the effective ways of minimizing its formation rates [6] [7] This was done via using in-house computer model at different pressures and temperatures. It calculates the moles fraction of burnt gases (species of interest, CO, CO2, NO, emissions) and heat of combustion (Q kJ/kg) produced from chemical reaction

Methods

Results

Conclusion