Experimental and Numerical Investigation of the Laminar Burning Velocity and Combustion Characteristics of Biogas at High Pressures

Abstract

Continuous variation in the composition of gaseous fuels derived from biomass is a challenge in designing efficient combustors for using them. In this study, experimental measurement of the laminar burning velocity (u l) of three different compositions of biogas fuel containing equimolar H2/CO mixtures and N2 ranging from 40 to 60% by volume is conducted. Numerical calculations of the flame structure, adiabatic flame temperature (T ad), species concentrations, and sensitivity analysis are also performed. Investigations are conducted over a practical range of equivalence ratios (ranging from 0.4 to 1.2) and at high pressures up to 4 bar. The experimental method of schlieren in a high-pressure combustion chamber is used for flame speed measurement. Numerical calculations are performed using the premixed code of CHEMKIN using four well-known reaction mechanisms. Laminar burning velocities calculated using the USC Mech Version II mechanism showed the best agreement with the experiments. The results indicated that the mole fraction of the H radical increases by equivalence ratio at the whole range considered in this study, while the OH radical declares its maximum concentration at stoichiometric conditions. This causes the maximum value of u l to occur at the equivalence ratio of 1.2. T ad increases by increasing pressure, especially near stoichiometric conditions and for lower N2-containing fuels. The equivalence ratio of the maximum flame temperature changes from the rich state (at φ = 1.05) to the stoichiometric state by increasing the N2 content of fuel from 40 to 60%. H2 plays a dominant role in the combustion of biogas fuel at high H2 concentration conditions. More than 50% of hydrogen burns before the flame front, while CO mainly burns after this position.

Laminar Burning Velocity of Biogas-Containing Mixtures. A Literature Review

“…The stationary flames were studied by (a) burner method using Bunsen burners [38,45,48,74,75] or flat flames burners [24,59,[76][77][78] or (b) the counter-flow twin flames method [79]. The non-stationary flames were studied by the constant volume method using cylindrical [22,23,26,44,46,[80][81][82] or spherical vessels [5,20,21,25,81,83,84]. The Bunsen burner method is a simple method to measure the laminar burning velocity for a conical flame [85].…”

“…For biogas-containing mixtures, several authors used the CHEMKIN package together with GRI-Mech mechanism (version 2.11 or 3.0) [22][23][24]26,41,45,56,[74][75][76]81,97] while other authors used USC Mech II mechanism [22,79]; San Diego mechanism [23,24]; C1-C3 mechanism [56] or Le Cong mechanism [77].…”

“…Scientific contributions regarding biogas explosions are available in the literature [12][13][14][15][16][17][18][19]. Some of them report values of flammability parameters of synthetic biogas (flammability limits, limiting oxygen concentration, maximum explosion pressure and maximum rate of pressure rise) [14,15], while others report laminar burning velocities from measurements or kinetic modelling [17,[20][21][22][23][24]. Recent studies regarding synthetic biogas-air mixtures [25,26], CH 4 -air-inert mixtures [27][28][29][30][31], and CH 4 -nitrous oxide-inert mixtures [32,33] were performed under various initial conditions to obtain the laminar burning velocities.…”

Experimental and Numerical Study on the Combustion Characteristics of Propane/Air Laminar Premixed Flame at Elevated Pressure

“…In the background of the current energy crisis, it is of great significance to further deepen our understanding of combustion to achieve efficient control of combustion and to find alternative energy sources. 4,5 In the last few decades, the automotive industry has directed many efforts toward the liquefied petroleum gas (LPG) to be used as an alternative fuel for the Spark Ignition (SI) engine. 6−8 Propane is the main component of LPG, and therefore, research on the basic combustion of propane is of great significance to further improve the combustion control of SI engine.…”

“…Throughout the history of human social development, from the beginning of heating, self-defense, to all kinds of industrial equipment and power plants, combustion has penetrated into every aspect of human society. − Although the energy infrastructure has undergone many innovations, fossil fuels are still the main components of energy. In the background of the current energy crisis, it is of great significance to further deepen our understanding of combustion to achieve efficient control of combustion and to find alternative energy sources. , In the last few decades, the automotive industry has directed many efforts toward the liquefied petroleum gas (LPG) to be used as an alternative fuel for the Spark Ignition (SI) engine. − Propane is the main component of LPG, and therefore, research on the basic combustion of propane is of great significance to further improve the combustion control of SI engine.…”