The Laminar Burning Velocities of Stoichiometric Methane–Air Mixture from Closed Vessels Measurements

Abstract

The present work aims to evaluate the performance of the constant-volume method by several sets of experiments carried out in three different closed vessels (a sphere and two cylinders) analyzing the obtained results in order to obtain accurate laminar burning velocities. Accurate laminar burning velocities can be used in the development of computational fluid dynamics models in order to design new internal combustion engines with a higher efficiency and lower fuel consumption leading to a lower degree of environmental pollution. The pressure-time histories obtained at various initial pressures from 0.4 to 1.4 bar and ambient initial temperature were analyzed and processed using two different correlations (one implying the cubic low coefficient and the other implying the burnt mass fraction). The laminar burning velocities obtained at various initial pressures are necessary for the realization of a complete kinetic study regarding the combustion reaction and testing the actual reaction mechanisms. Data obtained from measurements were completed and compared with data obtained from runs using two different detailed chemical kinetic mechanisms (GRI 3.0 and Warnatz) and with laminar burning velocities from literature. Our experimental burning velocities ranging from 35.3 cm/s (data from spherical vessel S obtained using the burnt mass fraction) to 37.5 cm/s (data from cylindrical vessel C1 obtained using the cubic law) are inside the interval of confidence as reported by other researchers. From the dependence of the laminar burning velocity on the initial pressure, the baric coefficients were obtained. These coefficients were further used to obtain the overall reaction orders. The baric coefficients (ranging between −0.349 and −0.212) and the overall reaction orders (ranging between 1.42 and 1.50) obtained in this study fall within the reference range of data specific to methane–air mixtures examined at ambient initial temperature.

Deflagration Dynamics of Methane–Air Mixtures in Closed Vessels at Elevated Temperatures

“…The selection of these temperatures for the laminar burning velocity (LBV) tests was intentional, aiming to mimic the common operational temperatures found in many methane-fueled systems [38]. Furthermore, these temperatures were chosen due to their ease of attainment and the ability to precisely control them, making them ideal for experiments conducted in a laboratory setting.…”

“…From the five experimental tests conducted at varying initial temperatures with the stoichiometric mixture of methane and air, we computed the average values for two critical parameters: the maximum explosion pressure (Pmax) and the peak rate of explosion pressure rise. These averages were derived from the data collected across all temperature The selection of these temperatures for the laminar burning velocity (LBV) tests was intentional, aiming to mimic the common operational temperatures found in many methanefueled systems [38]. Furthermore, these temperatures were chosen due to their ease of attainment and the ability to precisely control them, making them ideal for experiments conducted in a laboratory setting.…”

“…As the initial temperature (T 0 ) increases, so does S U , reflecting a direct relationship between temperature and combustion velocity. The literature [34][35][36][37][38] discusses LBV's dependency on the initial pressure and the stoichiometry coefficient of the mixture, with a standard pressure of P 0 = 1 bar and temperature of T 0 = 298 K, facilitating the verification of the results at the experiment's lower temperature limit (T 0 = 298.15 K). Cantera, which considers the chemical kinetics of combustion, is deemed as the most reliable for verifying computations.…”

Experimental Study of Explosion Characteristics and General Correlations of Lean H2/CO/CH4/Air Mixtures in Quiescence

“…where R is the cylinder radius; p 0 and p are the initial pressure and instantaneous pressure of the mixture, respectively; p e is the equilibrium pressure under an adiabatic constant volume condition [40] determined by the GasEq program, γ is the specific heat ratio of the unburned mixture, and c is the pressuretemperature dependence coefficient. To mitigate the effect of spark ignition and flame-wall interaction, the S L should be calculated within the specific pressure data points in the range 10-90% of the total heat release in which the flame radius R f ≤ 0:9R [41]. Figure 2(a) shows three examples of pressure rise for the H10C30M60, H20C30M50, and H30C30M40 fuels at ϕ = 0:6.…”