The Experts below are selected from a list of 76251 Experts worldwide ranked by ideXlab platform
Zhuyin Ren - One of the best experts on this subject based on the ideXlab platform.
-
an analytic model for the effects of nitrogen dilution and Premixing characteristics on nox formation in turbulent premixed hydrogen flames
International Journal of Hydrogen Energy, 2017Co-Authors: Hua Zhou, Lingyun Hou, Zhuyin RenAbstract:Abstract Advanced hydrogen gas turbine is a promising technology to achieve near-zero emission of carbon dioxide and higher cycle efficiency. With the increased firing temperature and pressure ratio, nitrogen reinjection combined with dry premixed combustion is promising to achieve the challenging low NOx emission. In this study, the effects of nitrogen dilution and fuel/air Premixing characteristics on the flame characteristics and NOx emission are investigated first through simulating one-dimensional premixed flames with a 13-species and 39-reaction mechanism at the elevated engine operation conditions. The variation of flame thicknesses and laminar flame speeds with nitrogen dilution is investigated. The NOx formation is characterized by the flame-front NOx and the constant NOx formation rates in the post-flame region. It is shown that the flame-front NOx is an order of 1 ppm and does not change significantly (within 20%) with nitrogen dilution. In contrast, the NOx formation rates in the post-flame region decrease monotonically with nitrogen dilution due to the decrease of oxygen concentration. A detailed analysis of NOx formation reveals that the N 2 O pathway is significant and it can account for at least 20% of the NOx formation in the post-flame region. Then an analytic model considering both the extended Zeldovich mechanism and the N 2 O pathway is constructed by assuming the involved radicals being in chemical equilibrium. The model can be employed to efficiently estimate the NOx formation in fully premixed hydrogen gas turbines. Next, the effects of fuel/air Premixing characteristics on the mean NOx formation rate in the post-flame region are quantified by reconstructing the PDF of mixture fraction. It is shown that without the nitrogen dilution, the NOx formation rate increases dramatically with fuel/air unmixedness due to the existence of local hot spots. Nitrogen dilution can dramatically reduce the NOx formation rate at the same level of unmixedness through reducing the local hot spots. Moreover, nitrogen dilution reduces the sensitivity of the NOx formation rate to fuel/air unmixedness, which greatly alleviates the mixing requirement for the Premixing nozzles in gas turbines. Finally, a model for the estimation of NOx emission is constructed, which builds the connection between NOx emission, nitrogen dilution, unmixedness and flow residence time in combustors.
Rakesh Kumar Maurya - One of the best experts on this subject based on the ideXlab platform.
-
effect of Premixing ratio injection timing and compression ratio on nano particle emissions from dual fuel non road compression ignition engine fueled with gasoline methanol port injection and diesel direct injection
Fuel, 2017Co-Authors: Mohit Saxena, Rakesh Kumar MauryaAbstract:Abstract In present study, the effect of fuel Premixing ratio, direct fuel injection timings and engine compression ratio on the soot particle emissions in nano-size range from a non-road compression ignition engine is investigated. Experiments are conducted on modified dual fuel single cylinder engine at 1500 rpm. To run the engine in dual fuel mode, port fuel injection (PFI) system is installed by modifying intake manifold of the engine and developing a PFI controller. Experiments are conducted for various fuel Premixing ratio of gasoline/methanol-diesel at different engine load, diesel fuel injection timing and compression ratios. Differential mobility spectrometer based particle sizer is used for investigation of the soot particle number-size distribution, surface area-size distribution, particle mass-size distribution and total particle number concentration from the engine exhaust at various test conditions. Results revealed that total particle number concentration is higher at full engine load and increases with fuel Premixing ratio (especially in case of methanol-diesel dual fuel operation). Additionally, the peak particle number and mass concentration reduces with an increase in compression ratio of the engine.
A R Masri - One of the best experts on this subject based on the ideXlab platform.
-
Partial Premixing and stratification in turbulent flames
Proceedings of the Combustion Institute, 2015Co-Authors: A R MasriAbstract:This paper reviews recent advances in understanding the structure of turbulent partially premixed and stratified flames. The term "partially premixed" refers here to compositionally inhomogeneous mixtures that include flammable and non-flammable fluid while "stratified" combustion refers to a reacting front propagating through a range of compositions within the flammable limits. An overview of relevant laminar flame concepts is first introduced. In laminar partially premixed flames, the interaction between rich and lean mixtures is significant leading to improvement in the flame's resistance to extinction by straining. In lean back-supported laminar stratified flames, the flux of excess heat and radicals into the lean fluid results in higher flame speeds, broader reaction zones, and extended flammability limits compared to homogeneous counterparts. Rich stratified flames are more complex due to the combined fluxes of heat as well as reactive species such as H2and CO. Recent research in turbulent partially premixed as well as stratified flames is reviewed. Detailed measurements in burners representative of those found in gas turbine combustors show that partial Premixing at the lifted flame base increases with instability. Well-characterised laboratory burners where different fuel concentration gradients may be imposed at the jet exit plane show improved flame stability due to mixed-mode combustion. Maximum stability is reached at some optimum level of compositional inhomogeneity. Highly resolved measurements in turbulent stratified flames show that the mass fractions of CO and H2increase with stratification; a result that is consistent with laminar flame studies. Such experiments are, however, very difficult and require multi-level conditioning of the data. The paper concludes with a brief review of potential numerical approaches employed in the calculations of turbulent flames with inhomogeneous inlet conditions. A key challenge here is to reproduce the effects of increasing levels of stratification and/or inhomogeneity on the compositional structure of turbulent flames.
Houzeaux Guillaume - One of the best experts on this subject based on the ideXlab platform.
-
The Effect of Partial Premixing and Heat Loss on the Reacting Flow Field Prediction of a Swirl Stabilized Gas Turbine Model Combustor
Springer Verlag, 2018Co-Authors: Gövert Simon, Mira Daniel, Kok, Jim B. W., Vázquez Mariano, Houzeaux GuillaumeAbstract:This work addresses the prediction of the reacting flow field in a swirl stabilized gas turbine model combustor using large-eddy simulation. The modeling of the combustion chemistry is based on laminar premixed flamelets and the effect of turbulence-chemistry interaction is considered by a presumed shape probability density function. The prediction capabilities of the presented combustion model for perfectly premixed and partially premixed conditions are demonstrated. The effect of partial Premixing for the prediction of the reacting flow field is assessed by comparison of a perfectly premixed and partially premixed simulation. Even though significant mixture fraction fluctuations are observed, only small impact of the non-perfect Premixing is found on the flow field and flame dynamics. Subsequently, the effect of heat loss to the walls is assessed assuming perfectly Premixing. The adiabatic baseline case is compared to heat loss simulations with adiabatic and non-adiabatic chemistry tabulation. The results highlight the importance of considering the effect of heat loss on the chemical kinetics for an accurate prediction of the flow features. Both heat loss simulations significantly improve the temperature prediction, but the non-adiabatic chemistry tabulation is required to accurately capture the chemical composition in the reacting layers.The research leading to these results has received funding through the People Program (Marie Curie Actions) of the European Union’s Seventh Framework Program (FP7, 2007-2013) for the project COPA-GT (grant agreement No. FP7-290042) as well as the European Union’s Horizon 2020 Program (2014-2020) and the Brazilian Ministry of Science, Technology and Innovation through Rede Nacional de Pesquisa (RNP) under the HPC4E Project (grant agreement No. 689772). Furthermore, computer resources and technical assistance has been provided by the Red Española de Supercomputación (RES) (grant numbers FI-2015-1-0002, FI-2015-3-0013, FI-2016-1-0001).Peer Reviewe
-
The Effect of Partial Premixing and Heat Loss on the Reacting Flow Field Prediction of a Swirl Stabilized Gas Turbine Model Combustor
'Springer Science and Business Media LLC', 2018Co-Authors: Gövert Simon, Mira Daniel, Kok, Jim B. W., Vázquez Mariano, Houzeaux GuillaumeAbstract:This work addresses the prediction of the reacting flow field in a swirl stabilized gas turbine model combustor using large-eddy simulation. The modeling of the combustion chemistry is based on laminar premixed flamelets and the effect of turbulence-chemistry interaction is considered by a presumed shape probability density function. The prediction capabilities of the presented combustion model for perfectly premixed and partially premixed conditions are demonstrated. The effect of partial Premixing for the prediction of the reacting flow field is assessed by comparison of a perfectly premixed and partially premixed simulation. Even though significant mixture fraction fluctuations are observed, only small impact of the non-perfect Premixing is found on the flow field and flame dynamics. Subsequently, the effect of heat loss to the walls is assessed assuming perfectly Premixing. The adiabatic baseline case is compared to heat loss simulations with adiabatic and non-adiabatic chemistry tabulation. The results highlight the importance of considering the effect of heat loss on the chemical kinetics for an accurate prediction of the flow features. Both heat loss simulations significantly improve the temperature prediction, but the non-adiabatic chemistry tabulation is required to accurately capture the chemical composition in the reacting layers.The research leading to these results has received funding through the People Program (Marie Curie Actions) of the European Union’s Seventh Framework Program (FP7, 2007-2013) for the project COPA-GT (grant agreement No. FP7-290042) as well as the European Union’s Horizon 2020 Program (2014-2020) and the Brazilian Ministry of Science, Technology and Innovation through Rede Nacional de Pesquisa (RNP) under the HPC4E Project (grant agreement No. 689772). Furthermore, computer resources and technical assistance has been provided by the Red Española de Supercomputación (RES) (grant numbers FI-2015-1-0002, FI-2015-3-0013, FI-2016-1-0001).Peer ReviewedPostprint (published version
-
The Effect of Partial Premixing and Heat Loss on the Reacting Flow Field Prediction of a Swirl Stabilized Gas Turbine Model Combustor
Springer, 2018Co-Authors: Gövert Simon, Mira Daniel, Vázquez Mariano, Kok, Jim B.w., Houzeaux GuillaumeAbstract:This work addresses the prediction of the reacting flow field in a swirl stabilized gas turbine model combustor using large-eddy simulation. The modeling of the combustion chemistry is based on laminar premixed flamelets and the effect of turbulence-chemistry interaction is considered by a presumed shape probability density function. The prediction capabilities of the presented combustion model for perfectly premixed and partially premixed conditions are demonstrated. The effect of partial Premixing for the prediction of the reacting flow field is assessed by comparison of a perfectly premixed and partially premixed simulation. Even though significant mixture fraction fluctuations are observed, only small impact of the non-perfect Premixing is found on the flow field and flame dynamics. Subsequently, the effect of heat loss to the walls is assessed assuming perfectly Premixing. The adiabatic baseline case is compared to heat loss simulations with adiabatic and non-adiabatic chemistry tabulation. The results highlight the importance of considering the effect of heat loss on the chemical kinetics for an accurate prediction of the flow features. Both heat loss simulations significantly improve the temperature prediction, but the non-adiabatic chemistry tabulation is required to accurately capture the chemical composition in the reacting layers. © 2017, The Author(s).Funding The research leading to these results has received funding through the People Program (Marie Curie Actions) of the European Union’s Seventh Framework Program (FP7, 2007-2013) for the project COPA-GT (grant agreement No. FP7-290042) as well as the European Union’s Horizon 2020 Program (2014-2020) and the Brazilian Ministry of Science, Technology and Innovation through Rede Nacional de Pesquisa (RNP) under the HPC4E Project (grant agreement No. 689772). Furthermore, computer resources and technical assistance has been provided by the Red Española de Supercomputación (RES) (grant numbers FI-2015-1-0002, FI-2015-3-0013, FI-2016-1-0001).Peer Reviewe
Ishwar K. Puri - One of the best experts on this subject based on the ideXlab platform.
-
Acetylene and ethylene mole fractions in methane/air partially premixed flames
Symposium (International) on Combustion, 2007Co-Authors: Li-keng Tseng, Ishwar K. Puri, Jayavant P. Gore, Tadao TakenoAbstract:Mole fractions of acetylene in flames play a major role in soot formation. An experimental and computational study of the structure of non-premixed and partially premixed methane/air flames was condducted, using a counterflow flame, with emphasis on investigating C 2 H 2 and C 2 H 4 mole fractions. The operating conditions were selected to maintain a fixed stretch rate on the oxidizer side for different levels of partial Premixing. Moderately high stretch rates were used to prevent the buoyancy effects. The high stretch rates and selection of methane as the fuel resulted in flames with negligible soot formation based on their blue color. However, measurable mole fractions of C 2 H 2 and C 2 H 4 existed at all levels of partial Premixing. Local measurements of species mole fractions were performed using sampling and gas chromatography. Numerical simulations involved 30 species, variable diffusivities, and C 2 chemistry consisting of 278 steps. Analysis of formation and consumption of C 2 H 2 and C 2 H 4 was completed using quantitative reaction path diagrams (QRPD). The results show that the predictions of C 2 H 2 and C 2 H 4 mole fractions are significantly higher than measurements. Unavoidable errors associated with probe sampling are responsible for only a part of the discrepancies. A preliminary investigation of C 3 -C 6 chemistry shows that only a small portion of the error results from the neglect of conversion to higher hydrocarbons. Therefore, critical studies of the rate constants of the relevant reactions, which are identified using the QRPD, are warranted.
-
an experimental and numerical investigation of n heptane air counterflow partially premixed flames and emission of nox and pah species
Combustion and Flame, 2006Co-Authors: Paolo Berta, Suresh K Aggarwal, Ishwar K. PuriAbstract:An experimental and numerical investigation of counterflow prevaporized partially premixed n-heptane flames is reported. The major objective is to provide well-resolved experimental data regarding the detailed structure and emission characteristics of these flames, including profiles of C1-C6, and aromatic species (benzene and toluene) that play an important role in soot formation. n-Heptane is considered a surrogate for liquid hydrocarbon fuels used in many propulsion and power generation systems. A counterflow geometry is employed, since it provides a nearly one-dimensional flat flame that facilitates both detailed measurements and simulations using comprehen- sive chemistry and transport models. The measurements are compared with predictions using a detailed n-heptane oxidation mechanism that includes the chemistry of NOx and PAH formation. The reaction mechanism was syn- ergistically improved using pathway analysis and measured benzene profiles and then used to characterize the effects of partial Premixing and strain rate on the flame structure and the production of NOx and soot precursors. Measurements and predictions exhibit excellent agreement for temperature and major species profiles (N2 ,O 2, n-C7H16 ,C O2 ,C O, H2), and reasonably good agreement for intermediate (CH4 ,C 2H4 ,C 2H2 ,C 3Hx ) and higher hydrocarbon species (C4H8 ,C 4H6 ,C 4H4 ,C 4H2 ,C 5H10 ,C 6H12) and aromatic species (toluene and benzene). Both the measurements and predictions also indicate the existence of two partially premixed regimes; a double flame regime for φ 5.0. The NOx and soot precursor emissions exhibit strong dependence on partial Premixing and strain rate in the first regime and relatively weak dependence in the second regime. At higher levels of partial Premixing, NOx emission is increased due to increased residence time and higher peak temperature. In contrast, the emissions of acetylene and PAH species are reduced by partial Premixing because their peak locations move away from the stagnation plane, resulting in lower residence time, and the increased amount of oxygen in the system drives the reactions to the oxidation pathways. The effects of partial Premixing and strain rate on the production of PAH species become progressively stronger as the number of aromatic rings increases.
-
Nonpremixed flame control with microjets
Experiments in Fluids, 2004Co-Authors: Ranjan Ganguly, Ishwar K. PuriAbstract:The hydrodynamic control of buoyant nonpremixed flames is investigated by injecting high-momentum fluid through a central microjet. The resulting flame characteristics are mapped for jets of different strengths. The flame height decreases linearly with an increase in the microjet Froude number as the flow changes from a buoyancy-dominated to a momentum-controlled regime. The flame luminosity is reduced by injecting stronger microjets. The jets alter the flame structure by establishing strong entrainment of the ambient air from the quiescent surroundings. The introduction of an inert species as the microjet fluid has a similar qualitative effect as air. Microjet assistance is as effective as partial Premixing for reducing the flame height and luminosity.
