Experimental Measurement of Laminar Burning Velocity and Flammability Limits of Landfill Gas at Atmospheric and Elevated Pressures

Abstract

Landfill gas (LFG) produced from depletion of biological waste has the potential to become one of the main energy resources in the future. In this study, laminar burning velocity (ul), Markstein length, and flammability limits of different compositions of landfill gas (LFG) are measured using the Schlieren flame front visualization method in an 11 liter constant volume combustion chamber. Three common compositions of LFG with carbon dioxide (CO2) volumetric fraction of fuel ranging from 0.3 to 0.5 are examined. Pressure was changed from atmospheric pressure to 5 bar with an increment of 2 bar. The effects of equivalence ratio, pressure, and CO2 content of fuel on laminar burning velocity are investigated, and rich and lean burn limits of different compositions of fuel are obtained. Numerical investigation is also performed using the CHEMKIN package via GRI3.0 and UBC2.1 chemical kinetic mechanisms. The results indicate that increasing the pressure reduces laminar burning velocity, whereas it increases the adiabatic flame temperature as a result of alternation in the equilibrium point of combustion. Pressure considerably increases the rich burn limit equivalence ratio and expands the flammability range. Markstein length increases by increasing equivalence ratio, and its maximum value occurs at rich conditions. The results also indicate that increasing carbon dioxide content of fuel reduces laminar burning velocity at all pressures and equivalence ratios, mainly due to reduction of the adiabatic flame temperature.

Experimental and Numerical Investigation of Laminar Burning Velocities of Artificial Biogas Under Various Pressure and CO2 Concentration

“…These results are supported by the investigation of Schlieren images provided in Figure 4(a) and Figure 4(b). Many studies have also suggested similar relationship between CO2 concentration and initial mixture pressure toward laminar burning velocity value found in this study [9,13,[16][17][18][19]22].…”

“…The laminar burning velocity can be measured from spherically propagating flames by recording the increasing rate of the flame radius with respond to time [16,17]. There has been a series of studies on the effects of CO2 and initial mixtures pressure on laminar burning velocity of CH4 [18][19][20][21][22][23]. Some studies suggested that as the percentage of CO2 in fuel mixture increases, biogas laminar burning velocity decreased [10,[19][20][21][22].…”

“…There has been a series of studies on the effects of CO2 and initial mixtures pressure on laminar burning velocity of CH4 [18][19][20][21][22][23]. Some studies suggested that as the percentage of CO2 in fuel mixture increases, biogas laminar burning velocity decreased [10,[19][20][21][22]. Some studies have suggested that compared to other diluents such as N2 (Nitrogen) and H2 (Hydrogen), CO2 has much more significant effect in reducing laminar burning velocity of CH4 [18,19].…”

“…The presence of CO2 absorbed some of the heat generated from the chemical reactions within the combustion process. There has also been a series of studies on the effect of pressure on the laminar burning velocity of CH4 [16,21,22,25].…”

Combustion of Syngas in Intersecting Burners Using the Interferometry Method

“…Moreover, they have reported that an optimum jet-to-jet spacing exists for parallel burners at each Reynolds number. In a recent cross-sectional study, Askari and Ashjaee investigated the effect of the pressure on the laminar burning velocity and flammability limits of landfill gas, where their results indicate that a reducing pressure increases the laminar burning velocity. Studies over the past few years have provided important information on the effects of mixing conditions for various fuels, experimentally , and numerically …”