Researcher: Nozari, Hadi
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Nozari, Hadi
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Publication Metadata only Combustion characteristics of ammonia as a renewable energy source and development of reduced chemical mechanisms(American Institute of Aeronautics and Astronautics Inc, AIAA, 2015) N/A; Department of Mechanical Engineering; Karabeyoğlu, Mustafa Arif; Nozari, Hadi; Faculty Member; PhD Student; Department of Mechanical Engineering; College of Engineering; Graduate School of Sciences and Engineering; 114595; N/AIn the first section of this numerical study we investigate the combustion characteristics of ammonia-air mixtures at elevated pressure and lean conditions which are encountered in gas turbine combustors. Laminar premixed freely propagating flame and homogenous reactor models are used to calculate the combustion properties. The improvement by hydrogen addition to the fuel mixture in combustion characteristics such as laminar flame speed and ignition delay time is noticeable. Based on ammonia decomposition sensitivity analysis, it is found that the OH radicals have a leading role in controlling the fuel mole conversion and the laminar flame speed. The results of sensitivity study of total NOx formation with respect to the equivalence ratio reveal the possibility of localized rich combustion as an effective way to reduce the NOx concentration down to levels that are the same order as the modern gas turbine engines. In the second part of the study, by considering a wide range of conditions in terms of pressure, fuel mixture, and equivalence ratio we develop two reduced mechanisms based on the Konnov mechanism. The reduced mechanisms are capable of predicting total NOx emission level and laminar flame speed in an acceptable accuracy under wide range of conditions. Evaluating performance of the reduced mechanisms with respect to the full mechanism and experimental data shows that the mechanisms are able to predict the combustion properties with almost the same accuracy as the full Konnov mechanism and with nearly five times less CPU time expense.Publication Metadata only Porous medium based burner for efficient and clean combustion of ammonia-hydrogen-air systems(Pergamon-Elsevier Science Ltd, 2017) Karaca, Gizem; Tuncer, Onur; N/A; Department of Mechanical Engineering; Nozari, Hadi; Karabeyoğlu, Mustafa Arif; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 114595Due to its high hydrogen density and extensive experience base, ammonia (NH3) has been gaining special attention as a potential green energy carrier. This study focuses on premixed ammonia hydrogen air flames under standard temperature and pressure conditions using an inert silicon-carbide (SiC) porous block as a practical and effective medium for flame stabilization. Combustion experiments conducted using a lab scale burner resulted in stable combustion and high combustion efficiencies at very high ammonia concentration levels over a wide range of equivalence ratios. Noticeable power output densities have also been achieved. Preliminary results of NO,, emission measurements indicate NO. concentrations as low as 35 ppm under rich conditions. The remarkable capability of this specific burner to operate efficiently and cleanly at high ammonia concentration levels, which can easily be achieved by partial cracking of NH3, is believed to be a key accomplishment in the development of ammonia fired power generation systems.Publication Metadata only Numerical study of combustion characteristics of ammonia as a renewable fuel and establishment of reduced reaction mechanisms(Elsevier, 2015) N/A; Department of Mechanical Engineering; Nozari, Hadi; Karabeyoğlu, Mustafa Arif; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineeering; N/A; 114595With its high hydrogen density and already existing infrastructure, ammonia (NH3) is believed to be an excellent green fuel that can be used in energy generation and transportation systems. Combustion of ammonia has certain challenges (associated with its low flame speed and fuel bond NOx emissions) that need to be addressed before its widespread use in practical systems. The primary objective of this study is to develop a reduced reaction mechanism for the combustion of ammonia which can be used to expedite the design of effective ammonia combustors through numerical simulations of realistic combustor geometries with accurate kinetics models. First we have investigated the combustion characteristics of NH3/H-2/air mixtures at elevated pressure and lean conditions which are encountered in practical systems such as gas turbine combustors. Laminar premixed freely propagating flame model is used to calculate the combustion properties. The results of sensitivity study of total NOx formation with respect to the equivalence ratio indicates the possibility of localized rich combustion as an effective way to reduce the NOx concentration down to levels that are the same order as the modern gas turbine engines. In the second part of the study, by considering a wide range of conditions in terms of pressure, fuel mixture, and equivalence ratio we have developed two reduced mechanisms based on the Konnov mechanism. The reduced mechanisms are capable of predicting the total NOx emission level and the laminar flame speed at an acceptable accuracy over a wide range of conditions. Evaluating the performance of the reduced mechanisms with respect to the full mechanism and experimental data shows that the mechanisms are able to predict the combustion properties almost at the same accuracy level as the Konnov mechanism, but at a nearly five times less CPU time expense. (C) 2015 Elsevier Ltd. All rights reserved.Publication Metadata only Combustion of ammonia-rich NH3-H2-air mixtures: improvement of flame stability(American Institute of Aeronautics and Astronautics (AIAA), 2017) Tuncer, Onur; N/A; Department of Mechanical Engineering; Nozari, Hadi; Karabeyoğlu, Mustafa Arif; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 114595As a result of its high hydrogen density and extensive experience base, ammonia (NH3) has been gaining special attention as a potential green energy carrier, which can be used in power generation systems. Low flame speed is one of the main challenges of ammonia combustion for practical applications. In order to address this important matter, flame stability is experimentally studied in this paper, which focuses on premixed ammoniahydrogen-air flames under standard temperature and pressure conditions. We introduce the use of an inert silicon-carbide (SiC) porous block as a practical and effective medium for ammonia-hydrogen-air flame stabilization method, which enables stable combustion even at very high ammonia concentration levels in the fuel and over a wide range of operational conditions. Flames stabilized with the matrix of the porous media based burner have remarkably higher burning speeds and wider stability region compared to open flames or to flames held by other conventional flame holding methods. The relative effectiveness of the porous medium is believed to be related to the internal back flow of heat from the burned gases to the unburned gases by means of radiation and conduction. Effects of some major influential parameters including equivalence ratio, ammonia mixture fraction, and diameter of the burner on flame stability have been investigated. Measured temperature values at different equivalence ratios and mixture compositions are compared to the chemical kinetics predictions. Heat loss is proven to be the main reason for the deviation between the measured temperatures and the theoretical values rather than incomplete combustion. The remarkable capability of the porous medium burners to operate at very high ammonia concentrations in a wide range of equivalence ratios enables efficient combustion of ammonia in practical power generation applications. In the experiments power output densities as high as 1.1 kW/cm2 have been demonstrated.Publication Metadata only Evaluation of ammonia-hydrogen-air combustion in SiC porous medium based burner(Elsevier Science Bv, 2017) Tuncer, Onur; N/A; Department of Mechanical Engineering; Nozari, Hadi; Karabeyoğlu, Mustafa Arif; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 114595Based on its well-known merits ammonia has been gaining special attention as a potential renewable energy carrier which can be replaced in power generation systems. Considering its low flame speed as one of the main challenges of combusting ammonia, flame stability is experimentally investigated. Focus is on premixed ammonia-hydrogen-air flames with high mixture fractions of ammonia (60-90% by volume) under standard temperature and pressure conditions. Silicon-carbide (SiC) porous blocks are used for stabilizing flame in a wide range of conditions. Upper and lower stability criteria are established for various mixture compositions. Also, combustion completeness is evaluated by analyzing measured and predicted temperature. The remarkable capability of the porous medium burners to efficiently operate at very high fractions of ammonia in a wide range of equivalence ratios provides a new achievability in more efficient combustion in power generation applications.