scholarly journals EXPERIMENTAL INVESTIGATION ON THE ROLE OF THERMO-ACOUSTICS ON SOOT FORMATION

2018 ◽  
Vol 6 (6) ◽  
pp. 461-471
Author(s):  
Rahul Ravi Ravichandran ◽  
Sambit Supriya Dash ◽  
Vinayak Malhotra
Keyword(s):  
Soot Formation ◽  
Premixed Flames ◽  
Cumulative Effect ◽  
Experimental Investigations ◽  
Atmospheric Conditions ◽  
Acoustic Frequency ◽  
Wide Range ◽  
Partially Premixed Flames ◽  
Flame Behavior

Combustion is a complex phenomenon that involves the interaction of multiple phenomena, the cumulative effect of which give rise to the common flame that comprises wide range of practical, functional to propulsion applications. An interesting aspect that needs attention is the effect of the various surrounding environment phenomenon on its behavior and properties of premixed flames. It is noteworthy that soot formation is the main cause of pollution and a major cause of inefficiency of current propulsion systems. These phenomena root variety of energy interactions leading to energy transformations which in turn affect the flame behavior. Present work focuses on experimental investigations and implications of the externally induced acoustics on partially premixed flames. The subject is extensively studied as thermo-acoustics, and the current work emphases on studying its role on soot formation on premixed flames. Experimentation was carried out on a scaled setup comprising of a butane cylinder fitted with a nozzle, that houses 3 arrays consisting of 4 holes each placed equidistant to each other for entraining air. The resulting flame is impinged with acoustics from two independent and similar sources placed equidistant from the center of the nozzle. The entire process is systematically video graphed using a 60-fps regular CCD and analyzed for variation in flame heights and flickering frequencies. The observations involve fixed fuel mass flow rate with varying configuration of entrainment holes and acoustic frequency under normal ambient atmospheric conditions. The work establishes significant outcomes on the effect of acoustics on soot formation. The results are likely to encourage better understanding with applicability to commercial and domestic utilizations for energy generation for enhanced effectiveness and reduced hazards.

Formation of Soot in Ethylene-Air Partially Premixed Flames Over a Wide Range of Premixedness

2017 ◽  
Author(s):  
Aritra Chakraborty ◽  
Satya R. Chakravarthy
Keyword(s):  
Volume Fraction ◽  
Premixed Flames ◽  
Soot Volume Fraction ◽  
Premixed Flame ◽  
Fuel Flow Rate ◽  
Fuel Flow ◽  
Wide Range ◽  
Partially Premixed Flames ◽  
Laser Induced Incandescence ◽  
Partially Premixed

This paper reports an investigation of soot formation in ethylene-air partially premixed flames over a wide range of premixedness. An axisymmetric co-flow configuration is chosen to establish partially premixed flames from the fully non-premixed to fully premixed conditions. Reducing the fuel flow rate as a percentage of the maximum from the core stream and supplying the same to the annular stream leads to stratification of the reactant concentrations. The thermal power, overall equivalence ratio, and the average velocity in the both streams are maintained constant under all conditions. The soot volume fraction is estimated by light attenuation method, and laser induced incandescence is performed to map the soot distribution in the flow field. The soot volume fraction is observed to exhibit a ‘S’-type trend as the conditions are traversed from near the premixed to the non-premixed regimes. That is, when traversing from the non-premixed to near-premixed regime, below 60% fuel flow rate in core, the soot volume fraction drops drastically. The onset of sooting in the partially premixed flames is clearly seen to be at the tip of the rich-premixed flame branch of their triple flame structure, which advances upstream towards the base of the flame as the premixing is reduced. The ‘S’-type variation is clearly the effect of partial premixing, more specifically due to the presence of the lean premixed flame branch of the triple flame. Laser induced incandescence intensities are insufficient to capture the upstream advance of the soot onset with decreased premixedness. So, a quick and inexpensive technique to isolate soot luminescence through flame imaging is presented in the paper involving quasi-simultaneous imaging with a 650 nm and a BG-3 filter using a normal color camera.

Experimental and numerical study of soot formation and evolution in co-flow laminar partially premixed flames

Fuel ◽  
2018 ◽  
Vol 220 ◽  
pp. 396-402 ◽  
Author(s):  
Gianluigi De Falco ◽  
Mariano Sirignano ◽  
Mario Commodo ◽  
Laura Merotto ◽  
Francesca Migliorini ◽  
...  
Keyword(s):  
Soot Formation ◽  
Numerical Study ◽  
Premixed Flames ◽  
Partially Premixed Flames ◽  
Formation And Evolution ◽  
Partially Premixed

scholarly journals Influence of atmospheric conditions on the role of trifluoroacetic acid in atmospheric sulfuric acid–dimethylamine nucleation

2021 ◽  
Vol 21 (8) ◽  
pp. 6221-6230
Author(s):  
Ling Liu ◽  
Fangqun Yu ◽  
Kaipeng Tu ◽  
Zhi Yang ◽  
Xiuhui Zhang
Keyword(s):  
Sulfuric Acid ◽  
Trifluoroacetic Acid ◽  
Density Functional ◽  
Cluster Formation ◽  
Formation Rate ◽  
Urban Environments ◽  
Nucleation Process ◽  
Atmospheric Conditions ◽  
Wide Range

Abstract. Ambient measurements combined with theoretical simulations have shown evidence that the tropospheric degradation end-products of Freon alternatives, trifluoroacetic acid (TFA), one of the most important and abundant atmospheric organic substances, can enhance the nucleation process based on sulfuric acid (SA) and dimethylamine (DMA) in urban environments. However, TFA is widespread all over the world under different atmospheric conditions, such as temperature and nucleation precursor concentration, which are the most important factors potentially influencing the atmospheric nucleation process and thus inducing different nucleation mechanisms. Herein, using the density functional theory combined with the Atmospheric Cluster Dynamics Code, the influence of temperature and nucleation precursor concentrations on the role of TFA in the SA–DMA nucleation has been investigated. The results indicate that the growth trends of clusters involving TFA can increase with the decrease in temperature. The enhancement on particle formation rate by TFA and the contributions of the SA–DMA–TFA cluster to the cluster formation pathways can be up to 227-fold and 95 %, respectively, at relatively low temperature, low SA concentration, high TFA concentration, and high DMA concentration, such as in winter, at the relatively high atmospheric boundary layer, or in megacities far away from industrial sources of sulfur-containing pollutants. These results provide the perspective of the realistic role of TFA in different atmospheric environments, revealing the potential influence of the tropospheric degradation of Freon alternatives under a wide range of atmospheric conditions.

scholarly journals Investigation of flame behavior and dynamics prior to lean blowout in a combustor with varying mixedness of reactants for the early detection of lean blowout

2018 ◽  
Vol 11 ◽  
pp. 175682771881251 ◽  
Author(s):  
Somnath De ◽  
Arijit Bhattacharya ◽  
Sirshendu Mondal ◽  
Achintya Mukhopadhyay ◽  
Swarnendu Sen
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Premixed Flames ◽  
Early Prediction ◽  
Lean Blowout ◽  
Partially Premixed Flames ◽  
Rate Oscillations ◽  
Partially Premixed ◽  
Flame Behavior

Lean blowout is one of the major challenges faced when the gas turbine combustors are operated with lean fuel–air mixture to meet the emission norm. We experimentally study the flame behavior and the dynamics of heat release rate fluctuations during a transition to lean blowout. The study comprising flame visualization and estimating several measures to predict lean blowout for both premixed and partially premixed flames (using fuel ports F1 to F5) in a swirl stabilized dump combustor. To that end, we acquire unsteady heat release rate in terms of CH* chemiluminescence obtained through a photomultiplier tube with a narrow band-pass filter. For evaluating different statistical measures, we use National Instrument Labview software while acquiring the heat release rate oscillations. For premixed and partially premixed flames, such measures and the flame behavior show a different and, in some cases, even opposite trends as lean blowout is approached. However, in both premixed and partially premixed flames, the mean and root mean square values of the heat release rate fluctuation decrease as we decrease the equivalence ratio. Further, we show that the value of mean frequency calculated using Hilbert transform of the heat release rate fluctuations is a good indicator of lean blowout. Apart from the early prediction of lean blowout, different statistics of heat release rate oscillations, such as kurtosis and skewness, are shown to identify only the occurrence of lean blowout for premixed (F1 and F2) and flames with lower level of premixing (F3). They are not useful for the flames with high levels of unmixedness like F4 and F5. On the other side, probability density function is seen useful for both premixed and partially premixed flames. In short, we present the relative importance of different measures stated earlier for the identification and early prediction of lean blowout for both premixed and partially premixed flames.

scholarly journals Influence of atmospheric conditions on the role of trifluoroacetic acid in atmospheric sulfuric acid-dimethylamine nucleation

2020 ◽  
Author(s):  
Ling Liu ◽  
Fangqun Yu ◽  
Kaipeng Tu ◽  
Zhi Yang ◽  
Xiuhui Zhang
Keyword(s):  
Sulfuric Acid ◽  
Trifluoroacetic Acid ◽  
Density Functional ◽  
Cluster Formation ◽  
Formation Rate ◽  
Precursor Concentration ◽  
Nucleation Process ◽  
Atmospheric Conditions ◽  
Wide Range

Abstract. Ambient measurements combined with theoretical simulations have shown evidence that the tropospheric degradation end-products of Freon alternatives, trifluoroacetic acid (TFA), one of the most important and abundant atmospheric organic substances, can enhance the process of sulfuric acid (SA) – dimethylamine (DMA) – based nucleation process in urban environments. However, TFA is widespread all over the world with different atmospheric conditions, such as temperature and nucleation precursor concentration, which are the most important factors potentially influencing the atmospheric nucleation process and thus inducing different nucleation mechanisms. Herein, using the Density Functional Theory combined with the Atmospheric Cluster Dynamics Code, the influence of temperature and nucleation precursor concentration on the role of TFA in the SA-DMA nucleation has been investigated. The results indicate that the growth trends of clusters involving TFA can increase with the decrease of temperature. The enhancement of particle formation rate by TFA and the contributions of SA-DMA-TFA cluster to the cluster formation pathways can be up to as much as 227 times and 95 %, respectively, at relatively low temperature, low SA concentration, high TFA concentration and high DMA concentration, such as in winter or at relatively high atmospheric boundary layer and in megacities far away from industrial sources of sulfur-containing pollutants. These results provide the perspective of the realistic role of TFA in different atmospheric environments, revealing the potential influence of the tropospheric degradation of Freon alternatives under a wide range of atmospheric conditions.

Formation of Soot in Ethylene–Air Partially Premixed Flames Over a Wide Range of Premixedness

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
Aritra Chakraborty ◽  
Satya R. Chakravarthy
Keyword(s):  
Flow Rate ◽  
Volume Fraction ◽  
Premixed Flames ◽  
Soot Volume Fraction ◽  
Premixed Flame ◽  
Fuel Flow Rate ◽  
Fuel Flow ◽  
Wide Range ◽  
Partially Premixed Flames ◽  
Partially Premixed

This paper reports an investigation of soot formation in ethylene–air partially premixed flames (PPFs) over a wide range of premixedness. An axisymmetric co-flow configuration is chosen to establish PPFs from the fully nonpremixed to fully premixed conditions. Reducing the fuel flow rate as a percentage of the maximum from the core stream and supplying the same to the annular stream leads to stratification of the reactant concentrations. The thermal power, overall equivalence ratio, and the average velocity in both the streams are maintained constant under all conditions. The soot volume fraction is estimated by light attenuation method, and laser-induced incandescence (LII) is performed to map the soot distribution in the flow field. The soot volume fraction is observed to exhibit an “S”-type trend as the conditions are traversed from near the premixed to the nonpremixed regimes. That is, when traversing from the nonpremixed to near-premixed regime, below 60% fuel flow rate in core, the soot volume fraction drops drastically. The onset of sooting in the PPFs is clearly seen to be at the tip of the rich-premixed flame (RPF) branch of their triple flame structure, which advances upstream toward the base of the flame as the premixing is reduced. The S-type variation is clearly the effect of partial premixing, more specifically due to the presence of the lean premixed flame (LPF) branch of the triple flame. LII intensities are insufficient to capture the upstream advance of the soot onset with decreased premixedness. So, a quick and inexpensive technique to isolate soot luminescence through flame imaging is presented in the paper involving quasi-simultaneous imaging with a 650 nm and a BG-3 filter using a normal color camera.

Experimental Investigation of Gaseous Flow in a Micro-Tube

2009 ◽  
Author(s):  
Yasuhiro Yoshida ◽  
Chungpyo Hong ◽  
Yutaka Asako ◽  
Koichi Suzuki
Keyword(s):  
Mach Number ◽  
Gas Flow ◽  
Electrical Discharge Machining ◽  
Tube Length ◽  
Experimental Investigations ◽  
Arbitrary Lagrangian Eulerian ◽  
Atmospheric Conditions ◽  
Compressibility Effect ◽  
Wide Range ◽  
Tube Exit

Experimental investigations on nitrogen gas flow characteristics were performed for a micro-tube. The micro-tube was fabricated in a stainless steel block by electrical discharge machining (EDM). The tube diameter was 326 μm and the ratio of length to diameter was 200. The stagnation pressure was chosen in such a way that the exit Mach number ranged from 0.1 to 1.4. The outlet pressure was fixed at atmospheric conditions. The pressure was locally measured at five locations along tube length to determine local values of Mach number and friction factor for a wide range of flow regime from laminar to turbulent flow. The result shows that f·Re is a function of Mach number and higher than incompressible value, 64 due to the compressibility effect. The values of f·Re were compared with f·Re correlation in literature. In additional experiments, Mach number at the micro-tube exit was measured by using a Shadowgraph system which visualizes the shock wave of the gas. The micro-tube with 400 μm in diameter was used for the experiment. The super sonic flow was observed since Mach number at the micro-tube exit was beyond unity. The experimental results for laminar flow were compared with the numerical results obtained by the arbitrary-Lagrangian-Eulerian method. The both results are in excellent agreement.

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