scholarly journals Numerical Simulation of Air Inlet Conditions Influence on the Establishment of MILD Combustion in Stagnation Point Reverse Flow Combustor

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Xiao Liu ◽  
Hongtao Zheng
Keyword(s):  
Numerical Simulation ◽  
Stagnation Point ◽  
Reverse Flow ◽  
Air Inlet ◽  
Mild Combustion ◽  
Inlet Conditions

Void Fraction Physics Resulting From Chaos Control of Upward Gas-Liquid Slug Flow

2001 ◽  
Author(s):  
Robert M. MacMeccan ◽  
Heather M. Langford ◽  
Donald E. Beasley
Keyword(s):  
Slug Flow ◽  
Complex Dynamics ◽  
Open Loop ◽  
Experimental Investigations ◽  
Open Loop Control ◽  
Liquid Slug ◽  
Loop Control ◽  
Air Inlet ◽  
Specific Frequency ◽  
Inlet Conditions

Abstract The present investigation examines open-loop control of chaotic upward gas-liquid slug flow. Though highly structured, slug flow is deterministically chaotic in nature. Recent analytical and experimental investigations indicate that perturbation of a system parameter has the potential to reduce or increase chaos in a system. Slug flow provides an interesting medium for the investigation into control of chaotic systems due to its high degree of structure and complex physics. The response of slug flow under control in turn lends insight into its complex dynamics. The results of the present study validate open-loop control, showing that periodic perturbation of the air inlet conditions at a specific frequency destabilizes dominant system dynamics, pushing the system to less stable orbits with different flow physics.

Aerodynamic Behavior of Asymmetric Jets in 3-D Furnaces

1994 ◽  
Author(s):  
F. M. El-Mahallawy ◽  
M. A. Hassan ◽  
M. A. Ismail ◽  
H. Zafan
Keyword(s):  
Numerical Simulation ◽  
Flow Pattern ◽  
Numerical Experiments ◽  
Recirculation Zone ◽  
Reverse Flow ◽  
Three Dimensional ◽  
Flow Region ◽  
Stabilization Method ◽  
Flow Features

The purpose of this paper is to present and evaluate numerical experiments illustrating the flow features in a 3-D furnace utilizing unconventional asymmetrical jet that creates natural recirculation zone. The numerical simulation of this aerodynamic stabilization method have unveiled the three-dimensional nature of the flow pattern which possesses a quite large reverse flow region. The size and strength of the built recirculation zone would be capable of stabilizing the burning of low-quality fuels.

scholarly journals Applications of CFD Method to Gas Mixing Analysis in a Large-Scaled Tank

2007 ◽  
Author(s):  
Si Y. Lee ◽  
Richard A. Dimenna
Keyword(s):  
Liquid Surface ◽  
Operating Conditions ◽  
Evolution Rate ◽  
Cfd Modeling ◽  
Local Concentration ◽  
Gas Mixing ◽  
Recirculation Flow ◽  
Air Inlet ◽  
Inlet Conditions ◽  
Vapor Space

The computational fluid dynamics (CFD) modeling technique was applied to the estimation of maximum benzene concentration for the vapor space inside a large-scaled and high-level radioactive waste tank at Savannah River site (SRS). The objective of the work was to perform the calculations for the benzene mixing behavior in the vapor space of Tank 48 and its impact on the local concentration of benzene. The calculations were used to evaluate the degree to which purge air mixes with benzene evolving from the liquid surface and its ability to prevent an unacceptable concentration of benzene from forming. The analysis was focused on changing the tank operating conditions to establish internal recirculation and changing the benzene evolution rate from the liquid surface. The model used a three-dimensional momentum coupled with multi-species transport. The calculations included potential operating conditions for air inlet and exhaust flows, recirculation flow rate, and benzene evolution rate with prototypic tank geometry. The flow conditions are assumed to be fully turbulent since Reynolds numbers for typical operating conditions are in the range of 20,000 to 70,000 based on the inlet conditions of the air purge system. A standard two-equation turbulence model was used. The modeling results for the typical gas mixing problems available in the literature were compared and verified through comparisons with the test results. The benchmarking results showed that the predictions are in good agreement with the analytical solutions and literature data. Additional sensitivity calculations included a reduced benzene evolution rate, reduced air inlet and exhaust flow, and forced internal recirculation. The modeling results showed that the vapor space was fairly well mixed and that benzene concentrations were relatively low when forced recirculation and 72 cfm ventilation air through the tank boundary were imposed. For the same 72 cfm air inlet flow but without forced recirculation, the heavier benzene gas was stratified. The results demonstrated that benzene concentrations were relatively low for typical operating configurations and conditions. Detailed results and the cases considered in the calculations will be discussed here.

CFD Based Analysis of Burner Fuel Air Mixing Over a Range of Air Inlet and Fuel Pre-Heat Temperatures for a Siemens V94.3A Gas Turbine Burner

2006 ◽  
Author(s):  
O. R. Darbyshire ◽  
C. W. Wilson ◽  
A. Evans ◽  
S. B. M. Beck
Keyword(s):  
Gas Turbine ◽  
Computational Effort ◽  
Ambient Conditions ◽  
Fuel Gas ◽  
3 Dimensional ◽  
Continuity Equations ◽  
Air Inlet ◽  
Air Mixing ◽  
Inlet Conditions ◽  
Thermal Nox

The homogeneity of the fuel/air mix entering the combustion chamber of a gas turbine is known to be a factor in both the emissions performance (with poor mixing resulting in local hotspots and the formation of thermal NOx) and the generation of acoustic vibrations (humming). Obviously it is desirable to reduce both pollutants and unwanted acoustics as far as possible. The aim of this paper is to study the relationship between the local inlet conditions and the mixing of the fuel and air, specifically looking at the effects of fuel gas preheating and inlet air temperature on mixedness at the combustor inlet. A CFD model of the lean pre-mixed combustor for a Siemens v94.3A gas turbine was used to analyse the problem. The 3-dimensional model employs a structured mesh scheme and uses the symmetry of the burner to reduce computational effort. The model was solved using a 2nd order discretisation of the momentum and continuity equations along with the RNG k-ε turbulence model to provide closure. The boundary conditions for the model were taken from data obtained from in service measurements. Several runs were made using air inlet temperatures varying from −10°C to 30°C and gas inlet temperatures from 10°C to 450°C. The data obtained from the CFD simulations was processed to give an indication of the quality of the fuel/air mixing for each set of inlet conditions. This was then used to create a tool which can be used to determine the amount of gas pre-heat required to achieve the best possible mixing for a given set of ambient conditions. An estimation of the NOx produced at different conditions was derived from the mixing data. Analysis of the results showed that increasing the gas preheat produces an improvement in the mixing of the fuel and air in the burner. This improvement in mixing also resulted in a reduction in the estimated amount of NOx produced.

NUMERICAL SIMULATION OF THE FLOWS OVER TWO TANDEM CYLINDERS BY LATTICE BOLTZMANN METHOD

2005 ◽  
Vol 19 (28n29) ◽  
pp. 1551-1554 ◽  
Author(s):  
XIAOKE KU ◽  
JIANZHONG LIN
Keyword(s):  
Numerical Simulation ◽  
Pressure Distribution ◽  
Lattice Boltzmann Method ◽  
Stagnation Point ◽  
Lattice Boltzmann ◽  
Reynolds Numbers ◽  
Effective Distance ◽  
Minimum Pressure ◽  
Tandem Cylinders ◽  
Boltzmann Method

Flows over two tandem cylinders are simulated numerically based on the lattice Boltzmann method. The pressure distribution on the cylinders for varying distance between the two cylinders at different Reynolds numbers is depicted. The results show that the minimum pressure on the front cylinder does not occur at the stagnation point because of the existence of the back cylinder. The distance between the point with minimum pressure and the stagnation point becomes large with increasing Re number. The minimum pressure on the back cylinder varies with the distance between the two cylinders. The effective distance of interaction between two cylinders is less than 4d with d being the diameter of the cylinder.

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