scholarly journals Characteristics of diffusion flames with accelerated motion

2016 ◽  
Vol 20 (6) ◽  
pp. 2113-2124 ◽  
Author(s):  
Bo Lou ◽  
Yonghai Qiu ◽  
Jianhong Xu
Keyword(s):  
Growth Rate ◽  
Temperature Field ◽  
Diffusion Flame ◽  
Diffusion Flames ◽  
Visual Display ◽  
Liquefied Petroleum Gas ◽  
Combustion Heat ◽  
Accelerated Motion ◽  
Average Temperature ◽  
Flame Angle

The aim of this work is to present an experiment to study the characteristics of a laminar diffusion flame under acceleration. A Bunsen burner (nozzle diameter 8 mm), using liquefied petroleum gas as its fuel, was ignited under acceleration. The temperature field and the diffusion flame angle of inclination were visualised with the assistance of the visual display technology incorporated in MATLAB?. Results show that the 2-d temperature field under different accelerations matched the variation in average temperatures: they both experience three variations at different time and velocity stages. The greater acceleration has a faster change in average temperature with time, due to the accumulation of combustion heat: the smaller acceleration has a higher average temperature at the same speed. No matter what acceleration was used, in time, the flame angle of inclination increased, but the growth rate decreased until an angle of 90?: this could be explained by analysis of the force distribution within the flame. It is also found that, initially, the growth rate of angle with velocity under the greater acceleration was always smaller than that at lower accelerations; it was also different in flames with uniform velocity fire conditions.

Analysis of LPG diffusion flame in tube type burner

2019 ◽  
Vol 13 (3) ◽  
pp. 5278-5293
Author(s):  
Vipul Patel ◽  
Rupesh Shah
Keyword(s):  
Diffusion Flame ◽  
Emission Characteristic ◽  
Flame Stability ◽  
Liquefied Petroleum Gas ◽  
Air Velocity ◽  
Length Fraction ◽  
Low Emission ◽  
Tube Type ◽  
Stability Limits ◽  
Co Emission

The present research aims to analyse diffusion flame in a tube type burner with Liquefied petroleum gas (LPG) as a fuel. An experimental investigation is performed to study flame appearance, flame stability, Soot free length fraction (SFLF) and CO emission of LPG diffusion flame. Effects of varying air and fuel velocities are analysed to understand the physical process involved in combustion. SFLF is measured to estimate the reduction of soot. Stability limits of the diffusion flame are characterized by the blowoff velocity. Emission characteristic in terms of CO level is measured at different equivalence ratios. Experimental results show that the air and fuel velocity strongly influences the appearance of LPG diffusion flame. At a constant fuel velocity, blue zone increases and the luminous zone decreases with the increase in air velocity. It is observed that the SFLF increases with increasing air velocity at a constant fuel velocity. It is observed that the blowoff velocity of the diffusion flame increases as fuel velocity increases. Comparison of emission for flame with and without swirl indicates that swirl results in low emission of CO and higher flame stability. Swirler with 45° vanes achieved the lowest CO emission of 30 ppm at Φ = 1.3.

Thermal Mapping, via Liquid Crystals, of the Temperature Field near a Heated Surgical Probe

1973 ◽  
Vol 95 (2) ◽  
pp. 250-256 ◽  
Author(s):  
T. E. Cooper ◽  
J. P. Groff
Keyword(s):  
Blood Flow ◽  
Temperature Field ◽  
Liquid Crystals ◽  
Theoretical Model ◽  
Wheatstone Bridge ◽  
Visual Display ◽  
Two Dimensional ◽  
Test Medium ◽  
One Dimensional ◽  
Water Test

This paper discusses the use of heat for producing clinical lesions in tissue and presents the design and analysis of a resistively heated surgical probe. The probe surface temperature is accurately maintained and controlled by using a Wheatstone bridge. The probe was embedded in a clear agar–water test medium, and the temperature field generated by the probe was measured with liquid crystals, a material that provides a visual display of certain isotherms. Experimental results compare within approximately 10 percent of a two-dimensional numerical solution. A one-dimensional theoretical model is also developed which examines the influence of blood flow on the temperature field.

Simulation and Comparative Analysis on Environmental Control in Subway

2012 ◽  
Vol 209-211 ◽  
pp. 1068-1072
Author(s):  
Ming Liu ◽  
Bao Gang Zhang ◽  
Liu Wen ◽  
Zhong Zhi Huang
Keyword(s):  
Temperature Field ◽  
Energy Consumption ◽  
Comparative Analysis ◽  
Environmental Control ◽  
Thermal Environment ◽  
Airflow Velocity ◽  
Waiting Room ◽  
Local Climate ◽  
Average Temperature ◽  
Environment Control

To ensure passengers can have a comfortable thermal environment in the subway waiting room is one of the main targets in subway environment control. By using the CFD software, this paper takes an island platform with double-layer of Shenyang as the object to simulate the thermal environment of platform screen door and ventilation in the open system, then detailed analysis on the variation of the temperature field, airflow velocity field in the typical position. The results indicated that average temperature of no-PSD system platform is 2.5 ~3 °C higher than that of PSD system, standing room is 1.5 °C higher than that of PSD system , but these also meet the requirement of the standards of the environmental control and passengers’ thermal comfort. Meanwhile, through the comparative analysis to the energy consumption of the two systems, we find ventilating condition has superior to PSD system in energy saving, and it is more suitable for the local climate in the northeast.

scholarly journals The Effect of Temperature and Humidity May Reduce the Growth Rate of the Coronavirus Disease 2019 Epidemic

2020 ◽  
Author(s):  
Lei Qin ◽  
Qiang Sun ◽  
Jiani Shao ◽  
Yang Chen ◽  
Xiaomei Zhang ◽  
...  
Keyword(s):  
Growth Rate ◽  
Relative Humidity ◽  
Effect Of Temperature ◽  
Average Temperature ◽  
Temperature And Humidity ◽  
Scatter Plots ◽  
Low Humidity ◽  
Average Relative Humidity ◽  
Effects Of Temperature ◽  
The Relationship

Abstract Background: The effects of temperature and humidity on the epidemic growth of coronavirus disease 2019 (COVID-19)remains unclear.Methods: Daily scatter plots between the epidemic growth rate (GR) and average temperature (AT) or average relative humidity (ARH) were presented with curve fitting through the “loess” method. The heterogeneity across days and provinces were calculated to assess the necessity of using a longitudinal model. Fixed effect models with polynomial terms were developed to quantify the relationship between variations in the GR and AT or ARH.Results: An increased AT dramatically reduced the GR when the AT was lower than −5°C, the GR was moderately reduced when the AT ranged from −5°C to 15°C, and the GR increased when the AT exceeded 15°C. An increasedARH increased theGR when the ARH was lower than 72% and reduced theGR when the ARH exceeded 72%.Conclusions: High temperatures and low humidity may reduce the GR of the COVID-19 epidemic. The temperature and humidity curves were not linearly associated with the COVID-19 GR.

Investigation of Ducted Inverse Nonpremixed Flame Using Dynamic Systems Approach

2016 ◽  
Author(s):  
Uddalok Sen ◽  
Tryambak Gangopadhyay ◽  
Chandrachur Bhattacharya ◽  
Arpan Misra ◽  
Suman Karmakar ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Flow Rate ◽  
Diffusion Flame ◽  
Equivalence Ratio ◽  
Systems Approach ◽  
Diffusion Flames ◽  
Duct Acoustics ◽  
Practical Applications ◽  
Inverse Diffusion ◽  
Inverse Diffusion Flame

Gas turbine combustion has a number of practical applications, including aviation engines, ocean vessels, and tanks. The various advantages of normal diffusion flames, such as increased flame stability and reduced susceptibility to dynamic instabilities, has made it the de facto industrial standard. However, high NOx emission and sooting from such flames is a major problem, particularly for heavier hydrocarbons fuels. In that regard, the inverse diffusion flame offers a feasible alternative; but the dynamic response of such a flame, particularly in ducted conditions — where the unsteady heat release interacts with the duct acoustics — is relatively less researched. In the present work, an experimental investigation of a laboratory-scale inverse diffusion flame has been carried out. The inverse diffusion flame is found in applications like rocket motors, gas turbine combustors, and furnaces. In the present study, inverse diffusion flame from a coaxial burner inside a quartz tube was studied. The position of the duct with respect to the flame was kept fixed, while the global equivalence ratio was varied by keeping the air flow rate constant and changing the fuel flow rate. Various tools of nonlinear dynamics such as phase space reconstruction and recurrence quantification have also been used for dynamic characterization of such flames. The results show that the dynamics of the flame strongly depends on the global equivalence ratio.

scholarly journals Fourier Variant Homogenization of the Heat Transfer Processes in Periodic Composites

2020 ◽  
Vol 22 (3) ◽  
pp. 719-726
Author(s):  
Ewaryst Wierzbicki ◽  
Dorota Kula ◽  
Łukasz Wodzyński
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
Transfer Equation ◽  
Heat Conduction Equation ◽  
Fourier Coefficients ◽  
Heat Transfer Equation ◽  
Average Temperature ◽  
Periodic Composites ◽  
Transfer Processes ◽  
Limit Passage

AbstractThe well-known parabolic Heat Transfer Equation is a simplest recognized description of phenomena related to the heat conductivity in solids with microstructure. However, it is a tool difficult to use due to the discontinuity of coefficients appearing here. The purpose of the paper is to reformulate this equation to the form that allows to represent solutions in the form of Fourier’s expansions. This equivalent re-formulation has the form of infinite number of equations with Fourier coefficients in expansion of the temperature field as the basic unknowns. The first term in Fourier representation, being an average temperature field, should satisfy the well-known parabolic heat conduction equation with Fourier coefficients as fields controlling average temperature behavior. The proposed description takes into account changes of the composite periodicity accompanying changes in the variable perpendicular to the surfaces separating components, concerning FGM - type materials and can be treated as the asymptotic version of Heat Transfer Equation obtained as a result of a certain limit passage where the cell size remains unchanged.

scholarly journals Could Weather Fluctuations Affect Local Economic Growth? Evidence from Counties in the People's Republic of China

2020 ◽  
Vol 37 (2) ◽  
pp. 201-224
Author(s):  
Chengzheng Li ◽  
Jiajia Cong ◽  
Haiying Gu
Keyword(s):  
Economic Growth ◽  
Growth Rate ◽  
Cumulative Effect ◽  
People’S Republic Of China ◽  
People's Republic Of China ◽  
Republic Of China ◽  
Average Temperature ◽  
Temperature And Precipitation ◽  
Weather Changes ◽  
The Impact

This paper uses historical fluctuations of weather variables within counties in the People's Republic of China to identify their effects on economic growth from 1996 to 2012. We find three primary results. First, higher temperatures significantly reduce the growth rate of county-level gross domestic product per capita: an increase in the annual average temperature of 1°C lowers the growth rate by 1.05%–1.25%. The effect of higher temperatures is nonlinear. Second, fluctuations in temperature and precipitation not only have a level effect, they also have a substantial cumulative effect. Third, weather fluctuations have wide-ranging effects. Beyond their substantial effects on the growth rate of agricultural output, they also affect nonagriculture sectors, labor productivity, and investment. Our findings provide new evidence for the impact of weather changes on economic development and have major implications for adaptation policies.

Modelling NO-NO2 Conversion in Counter-Flow Diffusion Flames

2003 ◽  
Author(s):  
A. G. Kyne ◽  
M. Pourkashanian ◽  
C. W. Wilson ◽  
A. Williams
Keyword(s):  
Diffusion Flame ◽  
Diffusion Flames ◽  
Common Knowledge ◽  
Aircraft Engine ◽  
Combustion Products ◽  
Counter Flow ◽  
Kinetic Rates ◽  
Gas Turbine Exhaust ◽  
No2 Formation ◽  
Combustion Processes

As emission regulations become more stringent there is increasing interest in the formation of NO2 in combustion products where it is in higher concentration than if slowly formed from NO in the atmosphere. It is common knowledge that NO2 is significantly more toxic than NO. The chemistry of NO2 formation in combustion processes is simple in comparison to that of NO. Indeed, all NO2 is formed from oxidation of NO mainly by reaction with HO2 radicals with its conversion back to NO resulting from reactions involving O and H atoms. Since consumption and formation of NO2 always occur simultaneously, although with unbalanced kinetic rates leading to local super-equilibrium concentrations, parameters such as temperature, velocity and species concentrations fields can drastically affect the degree of conversion of NO to NO2 in combustion applications. It is not well known what these conditions are and in certain circumstances, such as aircraft engine reheat systems, the emission of NO2 is clearly visible under the form of brown fumes. A comprehensive numerical simulation was undertaken to investigate the NO-NO2 relationship in a counter-flow diffusion flame. The CHEMKIN II suite of software (Kee et al., 1989) in conjunction with the opposed diffusion flame code OPPDIF (Lutz et al, 1997) was run using the Gas Research Institute’s (GRI’s) methane reaction mechanism v.3.0. A number of different strain rates using boundary conditions typical in a gas turbine exhaust were investigated. A rate of production and sensitivity analysis was made in determining which reactions were important in the NO-NO2 conversion process.

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