Premixed Moderate or Intense Low-Oxygen Dilution (MILD) Combustion from a Single Jet Burner in a Laboratory-Scale Furnace

2011 ◽  
Vol 25 (7) ◽  
pp. 2782-2793 ◽  
Author(s):  
Pengfei Li ◽  
Jianchun Mi ◽  
Bassam B. Dally ◽  
Richard A. Craig ◽  
Feifei Wang
Keyword(s):  
Laboratory Scale ◽  
Low Oxygen ◽  
Mild Combustion ◽  
Single Jet

scholarly journals Numerical study of flame structure in the mild combustion regime

2015 ◽  
Vol 19 (1) ◽  
pp. 21-34 ◽  
Author(s):  
Amir Mardani ◽  
Sadegh Tabejamaat
Keyword(s):  
Fuel Injection ◽  
Numerical Study ◽  
Flame Structure ◽  
Combustion Regime ◽  
Low Oxygen ◽  
Mixing Rate ◽  
Jet Flame ◽  
Reduced Mechanism ◽  
Mild Combustion ◽  
O2 Concentration

In this paper, turbulent non-premixed CH4+H2 jet flame issuing into a hot and diluted co-flow air is studied numerically. This flame is under condition of the moderate or intense low-oxygen dilution (MILD) combustion regime and related to published experimental data. The modelling is carried out using the EDC model to describe turbulence-chemistry interaction. The DRM-22 reduced mechanism and the GRI2.11 full mechanism are used to represent the chemical reactions of H2/methane jet flame. The flame structure for various O2 levels and jet Reynolds numbers are investigated. The results show that the flame entrainment increases by a decrease in O2 concentration at air side or jet Reynolds number. Local extinction is seen in the upstream and close to the fuel injection nozzle at the shear layer. It leads to the higher flame entertainment in MILD regime. The turbulence kinetic energy decay at centre line of jet decreases by an increase in O2 concentration at hot Co-flow. Also, increase in jet Reynolds or O2 level increases the mixing rate and rate of reactions.

Theoretical Study on Chemical-Kinetic Characteristics of Oxy-Coal Mild Combustion

2016 ◽  
Author(s):  
Ruochen Liu ◽  
Enke An ◽  
Kun Wu
Keyword(s):  
Activation Energy ◽  
Oxygen Concentration ◽  
Reaction Pathway ◽  
Chemical Kinetic ◽  
State Theory ◽  
Kinetic Characteristics ◽  
Low Oxygen ◽  
Elementary Reactions ◽  
Mild Combustion ◽  
Low Oxygen Concentration

The chemical-kinetic characteristics of oxy-coal MILD combustion under different initial temperature and oxygen concentration were studied numerically. Aromatic benzene was considered representative for coal molecule. A unique reaction pathway under low oxygen concentration was obtained, the activation energy and reaction rate constant of involved elementary reactions were calculated through classic transition state theory (TST). The results show that low oxygen concentration and high temperature is advantageous for thickening flame front as well as slowing down flame propagation; as oxygen concentration and temperature increase, the global activation energy increases with greater slope; the decomposition of C5H5 dominates under high oxygen concentration, while the decomposition and oxidation of C5H5 become equally important as oxygen concentration decreases, leading to a new pathway that the complexity of overall chemical reactions develops; the radical CH2CHO is easily trigged under low oxygen concentration, its decomposition reaction dominates in the unique pathway C5H5→C5H4O→c-C4H5CH2CHO→CH3 due to larger activation energy, where more CO escapes. The simulation results have theoretical referencing value, laying foundations for the further practical work.

Characteristics of Nitric-Oxide Emissions from Traditional Flame and MILD Combustion Operating in a Laboratory-Scale Furnace

2020 ◽  
Vol 29 (4) ◽  
pp. 868-883
Author(s):  
Ziyun Shu ◽  
Feifei Wang ◽  
Chong Dai ◽  
Jicang Si ◽  
Bo Wang ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Laboratory Scale ◽  
Mild Combustion ◽  
Nitric Oxide Emissions

Actuation Studies for Active Control of Mild Combustion for Gas Turbine Application

2014 ◽  
Author(s):  
Emilien Varea ◽  
Stephan Kruse ◽  
Heinz Pitsch ◽  
Thivaharan Albin ◽  
Dirk Abel
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Active Control ◽  
Gas Turbines ◽  
Reverse Flow ◽  
Air Flow ◽  
Combustion Regime ◽  
Nox Emissions ◽  
Low Oxygen ◽  
Mild Combustion

MILD combustion (Moderate or Intense Low Oxygen Dilution) is a well known technique that can substantially reduce high temperature regions in burners and thereby reduce thermal NOx emissions. This technology has been successfully applied to conventional furnace systems and seems to be an auspicious concept for reducing NOx and CO emissions in stationary gas turbines. To achieve a flameless combustion regime, fast mixing of recirculated burnt gases with fresh air and fuel in the combustion chamber is needed. In the present study, the combustor concept is based on the reverse flow configuration with two concentrically arranged nozzles for fuel and air injections. The present work deals with the active control of MILD combustion for gas turbine applications. For this purpose, a new concept of air flow rate pulsation is introduced. The pulsating unit offers the possibility to vary the inlet pressure conditions with a high degree of freedom: amplitude, frequency and waveform. The influence of air flow pulsation on MILD combustion is analyzed in terms of NOx and CO emissions. Results under atmospheric pressure show a drastic decrease of NOx emissions, up to 55%, when the pulsating unit is active. CO emissions are maintained at a very low level so that flame extinction is not observed. To get more insights into the effects of pulsation on combustion characteristics, velocity fields in cold flow conditions are investigated. Results show a large radial transfer of flow when pulsation is activated, hence enhancing the mixing process. The flame behavior is analyzed by using OH* chemiluminescence. Images show a larger distributed reaction region over the combustion chamber for pulsation conditions, confirming the hypothesis of a better mixing between fresh and burnt gases.

scholarly journals Assessment of chemical mechanism and chemical reaction sensitivity analysis for CH4/H2 flame under mild combustion environment

2020 ◽  
Vol 24 (3 Part B) ◽  
pp. 2101-2111
Author(s):  
Zhao Yang ◽  
Xiangsheng Li ◽  
Zhenlin Wang ◽  
Zhuangqi Wang
Keyword(s):  
Stokes Equations ◽  
Chemical Mechanism ◽  
Navier Stokes ◽  
Low Oxygen ◽  
Navier Stokes Equations ◽  
Chemical Mechanisms ◽  
Concept Model ◽  
Mild Combustion ◽  
Fluent Software ◽  
Combustion Environment

To analyze the performance of different chemical mechanisms on the prediction under moderate and intense low-oxygen dilution combustion environment, six different kinds of mechanisms were tested by solving the Reynolds averaged Navier- Stokes equations in a 2-D domain with the eddy dissipation concept model by FLUENT software. Temperature and the species concentration of OH, CO, and H2O were compared with the experiment data. The experiment results showed some similarities for each chemical mechanism as well as discrepancies. The comparison of CH4 oxidation route between the GRI2.11 and GRI3.0 mechanisms was made by Chemkin code. Reaction 95 and 147 were responsible for low temperature region for GRI2.11 mechanism at downstream area.

Numerical and Experimental Studies of NO Formation Mechanisms under Methane Moderate or Intense Low-Oxygen Dilution (MILD) Combustion without Heated Air

2015 ◽  
Vol 29 (3) ◽  
pp. 1987-1996 ◽  
Author(s):  
Shiying Cao ◽  
Chun Zou ◽  
Qingsong Han ◽  
Yang Liu ◽  
Di Wu ◽  
...  
Keyword(s):  
Experimental Studies ◽  
Formation Mechanisms ◽  
Low Oxygen ◽  
No Formation ◽  
Mild Combustion ◽  
Heated Air

Moderate or Intense Low Oxygen Dilution (MILD) Combustion Characteristics of Pulverized Coal in a Self-Recuperative Furnace

2014 ◽  
Vol 28 (9) ◽  
pp. 6046-6057 ◽  
Author(s):  
Manabendra Saha ◽  
Bassam B. Dally ◽  
Paul R. Medwell ◽  
Emmet M. Cleary
Keyword(s):  
Combustion Characteristics ◽  
Pulverized Coal ◽  
Low Oxygen ◽  
Mild Combustion

Effects of Preheating and CO2 Dilution on Oxy-MILD Combustion of Natural Gas

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Mohamad Hassan Moghadasi ◽  
Rouzbeh Riazi ◽  
Sadegh Tabejamaat ◽  
Amir Mardani
Keyword(s):  
Cross Flow ◽  
Pure Oxygen ◽  
Navier Stokes ◽  
Formation Mechanisms ◽  
Inlet Temperature ◽  
Low Oxygen ◽  
Combustion Modeling ◽  
Mild Combustion ◽  
Stirred Reactor ◽  
Co Emission

Oxy-moderate or intense low-oxygen dilution (MILD) combustion, which is a novel combination of oxy-fuel technology and MILD regime, is numerically studied in the present work. The effects of external preheating and CO2 dilution level on the combustion field, emission, and CO formation mechanisms are investigated in a recuperative laboratory-scale furnace with a recirculating cross-flow. Reynolds-averaged Navier–Stokes (RANS) equations with eddy dissipation concept (EDC) model are employed to perform a 3-D simulation of the combustion field and the turbulence–chemistry interactions. In addition, a well-stirred reactor (WSR) analysis is conducted to further examine the chemical kinetics of this combination when varying the target parameters. The simulations used the skeletal USC-Mech II, which has been shown to perform well in the oxy-fuel combustion modeling. Results show that with more preheating, the uniformity of temperature distribution is noticeably enhanced at the cost of higher CO emission. Also as inlet temperature increases, the concentration of minor species rises and CO formation through the main path (CH4→CH3→CH2O→HCO→CO→CO2) is strengthened, while heavier hydrocarbons path (C2H2→CO) is suppressed. Meanwhile, greater CO2 addition notably closes the gap between maximum and exhaust temperatures. In a highly CO2-diluted mixture, chain-branching reactions releasing CH2O are strengthened, while chain-terminating reactions are weakened. CH2O production through CH3O is accelerated compared with the straight conversion of methyl to formaldehyde. When diluting the oxidant, methylene CH2(s) plays a more influential role in CO formation than when pure oxygen is used, contributing to higher CO emission.

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