Papers by snehasish panigrahy
Combustion and Flame, 2021
Abstract An experimental and kinetic modeling study of the influence of NOx (i.e. NO2, NO and N2O... more Abstract An experimental and kinetic modeling study of the influence of NOx (i.e. NO2, NO and N2O) addition on the ignition behavior of methane/‘air’ mixtures is performed. Ignition delay time measurements are taken in a rapid compression machine (RCM) and in a shock tube (ST) at temperatures and pressures ranging from 900–1500 K and 1.5–3.0 MPa, respectively for equivalence ratios of 0.5–2.0 in ‘air’. The conditions chosen are relevant to spark ignition and homogeneous charge compression ignition engine operating conditions where exhaust gas recirculation can potentially add NOx to the premixed charge. The RCM measurements show that the addition of 200 ppm NO2 to the stoichiometric CH4/oxidizer mixture results in a factor of three increase in reactivity compared to the baseline case without NOx for temperatures in the range 600–1000 K. However, adding up to 1000 ppm N2O does not show any appreciable effect on the measurements. The promoting effect of NO2 was found to increase with temperature in the range 950–1150 K, while the sensitization effect decreases at higher pressures. The experimental results measured are simulated using NUIGMech1.2 comprising an updated NOx sub-chemistry in this work. A kinetic analysis indicates that the competition between the reactions ĊH3 + NO2 ↔ CH3Ȯ + NO and ĊH3 + NO2 (+M) ↔ CH3NO2 (+M), the former being a propagation reaction and the latter being a termination reaction governs NOx sensitization on CH4 ignition. Recent calculations by Matsugi and Shiina (A. Matsugi, H. Shiina, J. Phys. Chem. A. 121 (2017) 4218–4224) for the nitromethane formation reaction CH3 + NO2 (+M) ↔ CH3NO2 (+M), together with the recently calculated rate constants for HONO/HNO2 reactions significantly improve ignition delay time predictions in the temperature range 600–1000 K. Furthermore, the experiments with NO addition reveal a non-monotonous sensitization impact on CH4 ignition at lower temperatures with NO initially acting as an inhibitor at low NO concentrations and then as a promoter as NO concentrations increase in the mixture. This non-monotonous trend is attributed to the role of the chain-termination reaction ĊH3 + NO2 (+M) ↔ CH3NO2 (+M) and the impact of NO on the transition to the chain-branching steps CH2O + HȮ2 ↔ HĊO + H2O2, H2O2 (+M) ↔ ȮH + ȮH (+M), HĊO ↔ CO + Ḣ followed by CO + O2 ↔ CO2 + O and Ḣ + O2 ↔ O + ȮH. NUIGMech1.2 is systematically validated against the new ignition delay measurements taken here together with species measurements and high temperature ignition delay time data available in the literature for CH4/oxidizer mixtures diluted with NO2/N2O/NO and is observed to accurately capture the sensitization trends.
Energy, Environment, and Sustainability, 2017
Technological growth of any nation demands more fossil fuels which cause two major threats. First... more Technological growth of any nation demands more fossil fuels which cause two major threats. First one is the shortage of fossil fuel, and the second is environmental pollution. Recently, the age-old conventional combustion process is being substituted by an innovative combustion technology, called porous medium combustion. This surge of interest in porous radiant burner is driven by some of the important benefits such as high thermal efficiency, low emission characteristics, high power modulation range, extended flammability limits and high power density. In the last two decades, there has been a significant development in the research aiming at changing the operating parameters and the design configurations of the porous radiant burners to attain lower emissions and higher thermal performances. Various burners based on porous medium combustion have been developed for industrial and domestic applications and showed beneficial over their conventional burner counterparts. Porous radiant burners based on porous medium combustion technology showed good emission characteristics and offer higher thermal efficiencies. Although, durability of few burners is still a matter of concern which results in non-commercialization of these products. This chapter summarizes the development of various porous radiant burners used in both industrial and cooking applications.
Energy & Fuels, 2017
To establish the applicability of dimethyl ether (DME-CH 3 OCH 3) as an alternative fuel additive... more To establish the applicability of dimethyl ether (DME-CH 3 OCH 3) as an alternative fuel additive to liquefied petroleum gas (LPG-48% n-C 4 H 10 , 25% i-C 4 H 10 , 23% C 3 H 10 , 4% C 2 H 6) for enhancing combustion and reducing hazardous emissions, in this article, the flame behavior of LPG-air mixture blended with DME is studied within a highly conducting and radiating porous inert burner (PIB) under excess enthalpy combustion condition. The experiments are performed in a two-section PIB comprising of silicon carbide (SiC) matrix and aluminum oxide (Al 2 O 3) balls. The numerical model for solving species continuity equation, energy balance equations for gas-and the solid-phases and mass conservation equation, is compared to the experimental data from the present work. New filtration velocity data are found for the stable combustion of LPG-DME-air mixtures inside the PIB. The effect of various DME volume fractions in the LPG-DME blends on temperature distribution, radical pool concentration, CO emission, reaction zone thickness and syngas production within the PIB are investigated. The results show that with the addition of DME the peak radical pool concentration increases, which enhances the filtration velocity and thus the operating limit of the PIB. It is further demonstrated that at the same input condition, the solid-phase temperature and preheating temperature of the PIB are more for the higher value of DME volume fraction. Contrary to previous findings, increasing DME level increases the peak mole fraction of CO, CH 4 , and CH 3 CHO, however, it decreases the equilibrium CO concentration. Furthermore, in case of pure DME flame, an order of magnitude decrease in C 2 H 2 , C 3 H 3 and C 6 H 6 is observed, however, flame with higher DME fraction generates more CH 2 O and CH 3 .
Proceeding of Proceedings of the 24th National and 2nd International ISHMT-ASTFE Heat and Mass Transfer Conference (IHMTC-2017), 2018
Numerical Heat Transfer, Part A: Applications, 2016
ABSTRACT Application of the lattice Boltzmann method (LBM) in solving a combined mode conduction,... more ABSTRACT Application of the lattice Boltzmann method (LBM) in solving a combined mode conduction, convection, and radiation heat transfer problem in a porous medium is extended. Consideration is given to a 1-D planar porous medium with a localized volumetric heat generation zone. Three particle distribution functions, one each for the solid temperature, the gas temperature, and the intensity of radiation, are simultaneously used to solve the gas- and the solid-phase energy equations. The volumetric radiation source term appears in the solid-phase energy equation, and it is also computed using the LBM. To check the accuracy of the LBM results, the same problem is also solved using the finite volume method (FVM). Effects of convective coupling, flow enthalpy, solid-phase conductivity, scattering albedo porosity, and emissivity on axial temperature distribution are studied and compared with the FVM results. Effects of flow enthalpy, solid-phase conductivity, and emissivity are also studied on radiative output. LBM results are in excellent agreement with those of the FVM.
Energy, 2016
This paper deals with numerical and experimental analyses of combustion of LPG (liquefied petrole... more This paper deals with numerical and experimental analyses of combustion of LPG (liquefied petroleum gas) (48% n-butane, 25% iso-butane, 23% propane, 4% ethane by mole fraction) in a domestic cooking stove with a two-layer porous radiant burner. The combustion zone consists of SiC matrix with 90% porosity, and the preheating zone is made of 3.0 mm diameter alumina balls. In the numerical study, for the 1-D planar geometry of the burner, the gas and the solid-phase energy equations, continuity equation, species conservation equation and ideal gas equation are simultaneously solved using the finite volume method. The volumetric radiation term appearing in the solid-phase energy equation is also computed using the finite volume method. Numerical results of temperature distributions, flammability limits and pollutant emissions for various equivalence ratios and thermal loads are found to have reasonably a good agreement with the experimental data. Towards improving the thermal performance of the cooking stove, effects of SiC matrix thickness, preheater thickness, solid-phase conductivity and scattering albedo on CO emissions and radiative flux are studied. In addition, following guidelines of the World Health Organization, the most effective burner on the basis of the minimum CO emission and the maximum thermal efficiency is proposed.
Proceedings of the 15th International Heat Transfer Conference, 2014
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Papers by snehasish panigrahy