Laminar burning velocity measurements of methane and carbon dioxide mixtures (biogas) over wide ranging temperatures and pressures

• Published in: Fuel (Guildford) Vol. 116; pp. 743 - 750
• Main Authors: Hinton, Nathan, Stone, Richard
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.01.2014; Elsevier
• Subjects: Applied sciences; Biogas; Biomass; Burning velocity; Carbon dioxide; Combustion; Energy; Energy. Thermal use of fuels; Engines; Engines and turbines; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Equivalence ratio; Exact sciences and technology; Fuels; Laminar; Methane; Natural energy; Reduction; Methane; Biogas; Carbon dioxide; Burning velocity; Correlation coefficient; Diluent; Measurement; Laminar flame; Gaseous fuel; Stability; Combustion; Spark ignition engine; High temperature; Combustion velocity; High pressure; Dual fuel engine; Dilution; Renewable energy; Flammability; Gas engine; Gas turbine; Performance; Comparative study
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2013.08.069

•Laminar burning velocities of biogas mixtures were measured using a combustion vessel.•Mixtures of varying methane/carbon dioxide fraction and equivalence ratio were tested.•Values were obtained and correlated for a range of pressures and temperatures.•Burning velocity increases with temperature and decreases with pressure.•Increasing carbon dioxide content reduces burning velocity and delays onset of cellularity. Biogas is an important renewable energy resource that is mostly methane but contains up to 40% carbon dioxide by volume. As the carbon dioxide is a diluent, it reduces the laminar burning velocity, the flame stability and the flammability range, all of which can have adverse effects on combustion system performance. When used in gas turbines, spark ignited gas engines and dual fuel engines it is important to have laminar burning velocity data for high temperatures and pressures. These data have been obtained by using the pressure rise data from constant volume combustion, so that a single experiment yields burning velocity data (linked by the isentropic compression) for a range of pressures and temperatures. The pressure/temperature dependency has been decoupled by conducting experiments with different initial temperatures and pressures. The results from experiments with different carbon dioxide fractions and equivalence ratios have been fitted to a correlation with twelve coefficients. Data have been obtained with up to 40% carbon dioxide, pressures of up to 18bar, temperatures of up to 660K and equivalence ratios in the range 0.7–1.4. Results showed a decrease in burning velocity with pressure and an increase with temperature. The effect of dilution with carbon dioxide was a reduction in burning velocity, to around 65% of that of pure methane when the carbon dioxide fraction was 40% for stoichiometric mixtures. There is only a very limited amount of prior burning velocity data for high temperatures and pressures, but where possible, comparisons have been made with published data.