Impacts of Dilution on Hydrogen Combustion Characteristics and NOx Emissions

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
P. R. Resende ◽  
Alexandre Afonso ◽  
Carlos Pinho ◽  
Mohsen Ayoobi
Keyword(s):  
Flame Stabilization ◽  
Combustion Characteristics ◽  
Operating Conditions ◽  
Nox Emissions ◽  
Detailed Chemical Kinetics ◽  
Portable Power ◽  
Small Scales ◽  
Potential Applications ◽  
Flame Behavior ◽  
Detailed Chemical

Combustion characteristics at small scales have been studied continuously due to the potential applications in portable power devices. It is known that heat release impacts at small scales result in different flame behavior as compared to conventional scales. The impacts of geometry, stoichiometry, flow rates, wall temperatures, etc., are widely studied in the literature. However, dilution impacts still need to be further studied due to its important role on controlling the flame behavior and subsequent pollutants emissions at these scales. In this work, premixed hydrogen/air combustion is simulated at an axis-symmetric microchannel (with diameter D = 0.8 mm and length L = 10 mm), where detailed chemical kinetics are implemented in simulations (32 species and 173 reactions). The heat transfer on the wall is considered by imposing a hyperbolic temperature profile on the wall, where the wall temperature increases from 300 K at the inlet to 1300 K at the outlet. With this setup, a range of equivalence ratios including a typical fuel-lean regime (ϕ = 0.7), stoichiometric regime (ϕ = 1.0), and two cases at an ultra-rich regime (ϕ = 2.0 and ϕ = 3.0) are investigated. For each equivalence ratio, excess dilution (using N2) is introduced to the mixture, and its impact is compared with other cases. With that, the impacts of dilution variations on the combustion characteristics of premixed hydrogen/air are investigated for different equivalence ratios. More specifically, several incidents such as flame dynamics, flame stabilization, extinctions, and NOx emissions are studied for the aforementioned operating conditions.

Impacts of Dilution on Hydrogen Combustion Characteristics and NOx Emissions

2017 ◽  
Author(s):  
Pedro Resende ◽  
Alexandre Afonso ◽  
Carlos Pinho ◽  
Mohsen Ayoobi
Keyword(s):  
Flame Stabilization ◽  
Combustion Characteristics ◽  
Operating Conditions ◽  
Nox Emissions ◽  
Detailed Chemical Kinetics ◽  
Portable Power ◽  
Small Scales ◽  
Potential Applications ◽  
Flame Behavior ◽  
Detailed Chemical

Combustion characteristics at small scales have been studied continuously due to the potential applications in portable power devices. It is known that heat release impacts at small scales result in different flame behavior as compared to conventional scales. The impacts of geometry, stoichiometry, flow rates, wall temperatures, etc. are widely studied in literature. However, dilution impacts still need to be further studied due to its important role on controlling the flame behavior and subsequent pollutants emissions at these scales. In this work, premixed hydrogen/air combustion is simulated at an axis-symmetric micro channel (with diameter D = 0.8mm and length L = 10mm), where detailed chemical kinetics are implemented in simulations (32 species and 173 reactions). The heat transfer on the wall is considered by imposing a hyperbolic temperature profile on the wall, where the wall temperature increases from 300 K at the inlet to 1300 K at the outlet. With this setup, a range of equivalence ratios including a typical fuel-lean regime (ϕ = 0.7), stoichiometric regime (ϕ = 1.0) and and two cases at an ultra-rich regime (ϕ = 2.0 and ϕ = 3.0) are investigated. For each equivalence ratio, excess dilution (using N2) is introduced to the mixture and its impact is compared with other cases. With that, the impacts of dilution variations on the combustion characteristics of premixed hydrogen/air are investigated for different equivalence ratios. More specifically, several incidents such as flame dynamics, flame stabilization, extinctions and NOx emissions are studied for the aforementioned operating conditions.

Scale Resolving CFD Investigations of Aerothermal Field and Emissions of a Lean Burn Aeroengine Combustor

2021 ◽  
Author(s):  
S. Paccati ◽  
L. Mazzei ◽  
A. Andreini ◽  
S. Patil ◽  
S. Shrivastava ◽  
...  
Keyword(s):  
Pressure Fluctuations ◽  
Computational Cost ◽  
Flame Stabilization ◽  
Operating Conditions ◽  
Tetrahedral Mesh ◽  
Main Stream ◽  
Nox Emissions ◽  
Lean Burn ◽  
Emission Data ◽  
Hexahedral Elements

Abstract Due to the increasingly stringent international limitations in terms of NOx emissions, the development of new combustor concepts has become extremely important in order for aircraft engines to comply with these regulations. In this framework, lean-burn technology represents a promising solution and several studies and emission data from production engines have proven that it is more promising in reducing NOx emissions than rich-burn technology. Considering the drawbacks of this combustion strategy (flame stabilization, flashback or blowout or the occurrence of large pressure fluctuations causing thermo-acoustics phenomena) as well as the difficulties and the high costs related to experimental campaigns at relevant operating conditions, Computational Fluid Dynamics (CFD) plays a key role in deepening understanding of the complex phenomena that are involved in such reactive conditions. During last years, large research efforts have been devoted to develop new advanced numerical strategies for high-fidelity predictions in simulating reactive flows that feature strong unsteadiness and high levels of turbulence intensity with affordable computational resources. In this sense, hybrid RANS-LES models represent a good compromise between accurate prediction of flame behaviour and computational cost with respect to fully-LES approaches. Stress-Blended Eddy Simulation (SBES) is a new global hybrid RANS-LES methodology which ensures an improved shielding of RANS boundary layers and a more rapid RANS-LES “transition” compared to other hybrid RANS-LES formulations. In the present work, a full annular aeronautical lean-burn combustor operated at real conditions is investigated from a numerical point of view employing the new SBES approach using poly-hexcore mesh topology, which allows to adopt an isotropic grid for more accurate scale-resolving calculations by means of fully regular hexahedral elements in the main stream. The results are compared to experimental data and to previous reference numerical results obtained with Scale Adaptive Simulation formulation on a tetrahedral mesh grid in order to underline the improvements achieved with the new advanced numerical setup.

scholarly journals Emissions and In-Cylinder Combustion Characteristics of Fischer-Tropsch and Conventional Diesel Fuels in a Modern CI Engine

2005 ◽  
Author(s):  
Alexander G. Sappok ◽  
Jeremy T. Llaniguez ◽  
Joseph Acar ◽  
Victor W. Wong
Keyword(s):  
Combustion Characteristics ◽  
Operating Conditions ◽  
Fuel Properties ◽  
Emissions Reduction ◽  
Cylinder Pressure ◽  
Fischer Tropsch ◽  
Diesel Fuels ◽  
Ultra Low Sulfur Diesel ◽  
Low Sulfur ◽  
Detailed Chemical

Derived from natural gas, coal, and even biomass Fischer-Tropsch (F-T) diesel fuels have a number of very desirable properties. The potential for emissions reduction with F-T diesel fuels in laboratory engine tests and on-road vehicle tests is well documented. While a number of chemical and physical characteristics of F-T fuels have been attributed to the observed reduction in emissions, the actual effects of both the fuel properties and in-cylinder combustion characteristics in modern diesel engines are still not well understood. In this study a 2002, six-cylinder, 5.9 liter, Cummins ISB 300 diesel engine, outfitted with an in-cylinder pressure transducer. was subjected to a subset of the Euro III 13-mode test cycle under steady-state operating conditions. Emissions and in-cylinder pressure measurements were conducted for neat F-T diesel, low sulfur diesel (LSD), ultra-low sulfur diesel (ULSD), and a blend of FT/LSD. In addition, a detailed chemical analysis of the fuels was carried out. The differences in the measured combustion characteristics and fuel properties were compared to the emissions variations between the fuels studied, and an explanation for the observed emissions behavior of the fuels was developed.

Combustion Characteristics of Small Size Gas Turbine Combustor Fueled by Biomass Gas Employing Flameless Combustion

2007 ◽  
Author(s):  
Masato Hiramatsu ◽  
Yoshifumi Nakashima ◽  
Sadamasa Adachi ◽  
Yudai Yamasaki ◽  
Shigehiko Kaneko
Keyword(s):  
Gas Turbine ◽  
Combustion Efficiency ◽  
Combustion Characteristics ◽  
Operating Conditions ◽  
Nox Emissions ◽  
Gas Turbine Combustor ◽  
Flameless Combustion ◽  
Engine Exhaust ◽  
Micro Gas Turbine

One approach to achieving 99% combustion efficiency (C.E.) and 10 ppmV or lower NOx (at 15%O2) in a micro gas turbine (MGT) combustor fueled by biomass gas at a variety of operating conditions is with the use of flameless combustion (FLC). This paper compares experimentally obtained results and CHEMKIN analysis conducted for the developed combustor. As a result, increase the number of stage of FLC combustion enlarges the MGT operation range with low-NOx emissions and high-C.E. The composition of fuel has a small effect on the characteristics of ignition in FLC. In addition, NOx in the engine exhaust is reduced by higher levels of CO2 in the fuel.

The Effects of Intake Flow Swirl on the Combustion Characteristics of Hydrogen Fueled HCCI Engines

2004 ◽  
Author(s):  
Chengke Liu ◽  
Ghazi A. Karim
Keyword(s):  
Combustion Process ◽  
Operating Conditions ◽  
Nox Emissions ◽  
Swirl Ratio ◽  
Detailed Chemical Kinetics ◽  
Initial Flow ◽  
Flow Swirl ◽  
Combustion Duration ◽  
Hcci Engines ◽  
Intake Flow

This paper describes the effects of the initial intake flow swirl on the combustion process of hydrogen-air homogeneous mixtures in HCCI engines. CFD KIVA3 code incorporated with detailed chemical kinetics was employed. The effects on the development and extent of non-uniformities in velocity, pressure, and temperature within the cylinder charge were investigated. Moreover, the effects of the initial flow swirl ratio values on the onset of autoignition and its timing, combustion duration, NOx emissions, and the onset of knock were evaluated. It is shown that an increase in the initial flow swirl ratio or speed lengthens the delay period for autoignition and extends the combustion period while reducing NOx emissions. There are optimum values of the initial swirl ratio and engine speed for a certain set of engine operating conditions that can achieve high thermal efficiencies and low NOx emissions while reducing the tendency to knock.

Numerical Simulation of Heavy Fuel Oil Combustion Characteristics and NOx Emissions in Calciner in Cement Industry

2015 ◽  
Author(s):  
Hisham Aboelsaod ◽  
Essam E. Khalil
Keyword(s):  
Molecular Nitrogen ◽  
Combustion Characteristics ◽  
Cement Industry ◽  
Operating Conditions ◽  
Fuel Oil ◽  
Combustion Model ◽  
Injection Velocity ◽  
Nox Emissions ◽  
Heavy Fuel Oil ◽  
Swirl Number

The aim of the present study is to numerically investigate the combustion characteristics of Heavy Fuel Oil (HFO) and NOx emissions inside a calciner used in cement industry. The calciner is a furnace placed before the rotary Kiln its main objectives are the reduction of CO2 emissions and air pollutions while enhancing the cement quality through separating the calcination and clinkering processes. In order to conduct the present investigations the calciner at CEMEX Egypt Cement Company was considered and real dimensions and operating conditions were applied. The combustion model was based on the conserved scalar (mixture fraction) and prescribed Probability Density Function (PDF) approach. The (RNG) k-ε turbulence model has been used. The HFO droplet trajectories were predicted by solving the momentum equations for the droplets using Lagrangian treatment. The radiation heat transfer equation was solved using P1 method. The formation of thermal NOx from molecular nitrogen was modeled according to the extended Zeldovich mechanism. The effects of varying the burner’s swirl number and viscosity grade on the combustion performance of HFO and the resulting NOx emissions were considered. The burner’s swirl number influences the mixing rate of air and fuel. A small swirl number ≤ 0.6 is not desired as it elongates the flame; increases flue gases temperatures and increases the NOx emissions inside the calciner. A swirl number ≥ 0.6 is found optimal for good combustion characteristics and NOx emissions concentration. Meanwhile, it was found that the HFO viscosity has a significant effect on the injection velocity and must be considered as a function of temperature during the analysis as this will significantly affects the combustion characteristics.

CFD Modeling and Operation Strategies for Hetero-/Homogeneous Combustion of Methane-Air Mixtures in Catalytic Microreactors Using Detailed Chemical Kinetics

2016 ◽  
Vol 11 (4) ◽  
pp. 291-304
Author(s):  
Junjie Chen ◽  
Baofang Liu
Keyword(s):  
Solid Wall ◽  
Chemical Kinetic ◽  
Vital Role ◽  
Operating Conditions ◽  
Cfd Modeling ◽  
Heterogeneous Chemistry ◽  
Detailed Chemical Kinetics ◽  
Feed Composition ◽  
Homogeneous Combustion ◽  
Detailed Chemical

Abstract The hetero-/homogeneous combustion of methane-air mixtures in platinum-coated microreactors was investigated by means of two-dimensional CFD (computational fluid dynamics) simulations with detailed chemical reaction schemes, detailed species transport, and heat transfer mechanisms in the solid wall. Detailed homogeneous and heterogeneous chemical kinetic mechanisms are employed to describe the chemistry. The effects of the reactor size, inlet velocity and feed composition were elucidated. Operation strategies for controlling the heterogeneous and homogeneous chemistry in heterogeneous-homogeneous microreactors were developed. Simulations using these mechanisms suggested that homogeneous chemistry can be sustained for gaps well below the quenching distance because of enhanced catalyst-induced heating. This finding has very important ramifications for catalyst safety and lifetime, as well as can be used to produce chemicals, e. g. in oxidative coupling and oxidative dehydrogenation reactions. The proportion of heterogeneous and homogeneous contributions depends strongly upon the reactor operating conditions. Reactor size plays a vital role in the homogeneous chemistry contribution. Smaller reactors result in reduced homogeneous chemistry contribution. Pure heterogeneous chemistry can occur under certain proper conditions, such as heat loss/heat exchange rates, feed compositions, and flow rates. The competition or synergism between homogeneous and heterogeneous chemistry was delineated.

scholarly journals An evaluation of effects of operational parameters on NOx emissions through detailed chemical kinetics simulations

2019 ◽  
Vol 158 ◽  
pp. 103-110 ◽  
Author(s):  
Øyvind Skreiberg ◽  
Tian Li ◽  
Elettra Vantaggiato ◽  
Liang Wang ◽  
Mette Bugge ◽  
...  
Keyword(s):  
Chemical Kinetics ◽  
Nox Emissions ◽  
Operational Parameters ◽  
Detailed Chemical Kinetics ◽  
Detailed Chemical

A Simulation of the Combustion of N-Heptane Fueled HCCI Engines Using a 3-D Model With Detailed Chemical Kinetics

2005 ◽  
Author(s):  
Chengke Liu ◽  
Ghazi A. Karim
Keyword(s):  
Carbon Monoxide ◽  
Combustion Chamber ◽  
Chemical Kinetics ◽  
Combustion Process ◽  
Combustion Characteristics ◽  
Chamber Wall ◽  
Detailed Chemical Kinetics ◽  
Hcci Engine ◽  
Initial Location ◽  
Detailed Chemical

A CFD multi-dimensional computational approach has been developed through a combination of a modified KIVA3 code together with a detailed chemical kinetics scheme for the oxidation of n-heptane in air while considering the effects of turbulence. The effects of adding different quantities of hydrogen, methane and carbon monoxide to the heptane on the combustion characteristics of the HCCI engine under different conditions were investigated both experimentally and numerically. The effects of changes in the combustion chamber wall surface temperature on the combustion characteristics of the HCCI engine were examined. It was found that the presence with n-heptane of some hydrogen, methane or carbon monoxide could delay to various extents the autoignition, while changes in the values of the combustion chamber wall temperature influence the autoignition timing and its initial location. It is suggested that the supplementing of the liquid fuel with gaseous fuels and/or application of a suitable glow-plug surface of optimum size and location fitted with temperature control may aid in controlling the combustion process of an HCCI engine while obtaining higher power output without producing knock.

Sign in / Sign up

Export Citation Format

Share Document