Experimental Study of Aeronautical Ignition in a Swirled Confined Jet-Spray Burner

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
J. Marrero-Santiago ◽  
A. Verdier ◽  
C. Brunet ◽  
A. Vandel ◽  
G. Godard ◽  
...  
Keyword(s):  
Flame Propagation ◽  
High Speed ◽  
Equivalence Ratio ◽  
Propagation Mode ◽  
Two Phase ◽  
Local Flow ◽  
Ignition Probability ◽  
Ignition Delay Times ◽  
Planar Laser ◽  
Local Equivalence

Aeronautical gas turbine ignition is still not well understood and its management and control are mandatory for new lean-burner designs. The fundamental aspects of swirled confined two-phase flow ignition are addressed in the present work. Two facilities enable the analysis of two characteristic phases of the process. The knowledge for ignition, acoustics and instabilities (KIAI)-Spray single-injector burner was investigated in terms of local flow properties, including the air velocity and droplet fuel (n-heptane) size-velocity characterization by phase Doppler anemometry (PDA), and the study of local equivalence ratio by means of planar laser-induced fluorescence (PLIF) on a tracer (toluene). The initial spark location inside the chamber is vital to ensure successful ignition. An ignition probability map was elaborated varying the location of a 532 nm laser-induced spark in the chamber under ultralean nominal conditions (ϕ = 0.61). The outer recirculation zone (ORZ) was found to be the best region for placing a spark and successfully igniting the mixture. A strong correlation was found between the ignition probability field and the airflow turbulent kinetic energy and velocity fields. Local equivalence ratio enhances the importance of the ORZ. Once a successful ignition is accomplished on one injector, the injector-to-injector flame propagation must be examined. High-speed visualization through two synchronized perpendicular cameras was applied on the KIAI-Spray linear multi-injector burner. Four different injector-to-injector distances and four fuels of different volatilities (n-heptane, n-decane, n-dodecane, and jet-A1 kerosene) were evaluated. Spray branches and interinjector regions changed with the interinjector distance. Two different flame propagation mechanisms were identified: the direct radial propagation and the arc propagation mode. Ignition delay times were modified with the injector-to-injector distance and with the different fuels.

Experimental Study of Aeronautical Ignition in a Swirled Confined Jet-Spray Burner

2017 ◽  
Author(s):  
J. Marrero-Santiago ◽  
A. Verdier ◽  
C. Brunet ◽  
A. Vandel ◽  
G. Godard ◽  
...  
Keyword(s):  
Flame Propagation ◽  
High Speed ◽  
Equivalence Ratio ◽  
Propagation Mode ◽  
Two Phase ◽  
Local Flow ◽  
Ignition Probability ◽  
Ignition Delay Times ◽  
Planar Laser ◽  
Local Equivalence

Aeronautical gas turbine ignition is still not well understood and its management and control is mandatory for new lean-burner designs. The fundamental aspects of swirled confined two-phase flow ignition are addressed in the present work. Two facilities enable the analysis of two characteristic phases of the process. The KIAI-Spray single-injector burner was investigated in terms of local flow properties, including the air velocity and droplet fuel (n-heptane) size-velocity characterization by phase Doppler anemometry (PDA), and the study of local equivalence ratio by means of planar laser induced fluorescence (PLIF) on a tracer (toluene). The initial spark location inside the chamber is vital to ensure successful ignition. An ignition probability map was elaborated varying the location of a 532 nm laser-induced spark in the chamber under ultra-lean nominal conditions (ϕ = 0.61). The outer recirculation zone (ORZ) was found to be the best region for placing a spark and successfully igniting the mixture. A strong correlation was found between the ignition probability field and the airflow turbulent kinetic energy and velocity fields. Local equivalence ratio enhances the importance of the ORZ. Once a successful ignition is accomplished on one injector, the injector-to-injector flame propagation must be examined. High-speed visualization through two synchronized perpendicular cameras was applied on the KIAI-Spray linear multi-injector burner. Four different injector-to-injector distances and four fuels of different volatilities (n-heptane, n-decane, n-dodecane and jet-A1 kerosene) were evaluated. Spray branches and inter-injector regions changed with the inter-injector distance. Two different flame propagation mechanisms were identified: the direct radial propagation and the arc propagation mode. Ignition delay times were modified with the injector-to-injector distance and with the different fuels.

scholarly journals Spray ignition and local flow properties in a swirled confined spray-jet burner: experimental analysis

2017 ◽  
Author(s):  
Javier Marrero Santiago ◽  
Antoine Verdier ◽  
Alexis Vandel ◽  
Gilles Godard ◽  
Gilles Cabot ◽  
...  
Keyword(s):  
Equivalence Ratio ◽  
Ignition Process ◽  
Flow Properties ◽  
Air Velocity ◽  
Mean Velocity ◽  
Local Flow ◽  
Ignition Probability ◽  
Piv Measurements ◽  
Mean Values ◽  
Local Equivalence

Laser ignition was investigated in the swirled, confined CORIA Rouen Spray Burner under ultra-lean conditions (Φ=0.61) with n-heptane as the liquid fuel. Ignition probability was calculated for different spark locations and compared to the non-ignited local flow properties. Mean velocity components of the carrier flow were measured by PDA under spray presence and without spray, and are compared to mean values from PIV. PIV measurements provide information on the instantaneous airflow and the total strain rate. Fuel droplet size-velocity data was measured by PDA. Toluene-PLIF images were acquired to provide information on the local equivalence ratio and the flammability factor. Results show that the outer recirculation zone (ORZ) has a flammability factor close to 1 and the highest ignition probability (~80%). These results have a high correlation with the air velocity field and turbulent kinetic energy. Instantaneous equivalence ratio images and shear rate-velocity fields give important information on local segregation of the flow properties that help to understand the ignition process. The present work provides a useful database for numerical simulations and industry, plus new insight on spray ignition.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4674

High Speed Imaging of Forced Ignition Kernels in Non-Uniform Jet Fuel/Air Mixtures

2017 ◽  
Author(s):  
Sheng Wei ◽  
Brandon Sforzo ◽  
Jerry Seitzman
Keyword(s):  
Heat Release ◽  
High Speed ◽  
Air Flow ◽  
Cetane Number ◽  
High Energy ◽  
Liquid Fuels ◽  
High Speed Imaging ◽  
Ignition Probability ◽  
Turbine Engine ◽  
Planar Laser

This paper describes experimental measurements of forced ignition of prevaporized liquid fuels in a well-controlled facility that incorporates non-uniform flow conditions similar to those of gas turbine engine combustors. The goal here is to elucidate the processes by which the initially unfueled kernel evolves into a self-sustained flame. Three fuels are examined: a conventional Jet-A and two synthesized fuels that are used to explore fuel composition effects. A commercial, high-energy recessed cavity discharge igniter located at the test section wall ejects kernels at 15 Hz into a preheated, striated crossflow. Next to the igniter wall is an unfueled air flow; above this is a premixed, prevaporized, fuel-air flow, with a matched velocity and an equivalence ratio near 0.75. The fuels are prevaporized in order to isolate chemical effects. Differences in early ignition kernel development are explored using three, synchronized, high-speed imaging diagnostics: schlieren, emission/chemiluminescence, and OH planar laser-induced fluorescence (PLIF). The schlieren images reveal rapid entrainment of crossflow fluid into the kernel. The PLIF and emission images suggest chemical reactions between the hot kernel and the entrained fuel-air mixture start within tens of microseconds after the kernel begins entraining fuel, with some heat release possibly occurring. Initially, dilution cooling of the kernel appears to outweigh whatever heat release occurs; so whether the kernel leads to successful ignition or not, the reaction rate and the spatial extent of the reacting region decrease significantly with time. During a successful ignition event, small regions of the reacting kernel survive this dilution and are able to transition into a self-sustained flame after ∼1–2 ms. The low aromatic/low cetane number fuel, which also has the lowest ignition probability, takes much longer for the reaction zone to grow after the initial decay. The high aromatic, more easily ignited fuel, shows the largest reaction region at early times.

scholarly journals High-Speed Imaging of Forced Ignition Kernels in Nonuniform Jet Fuel/Air Mixtures

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Sheng Wei ◽  
Brandon Sforzo ◽  
Jerry Seitzman
Keyword(s):  
Heat Release ◽  
High Speed ◽  
Air Flow ◽  
Cetane Number ◽  
High Energy ◽  
Liquid Fuels ◽  
High Speed Imaging ◽  
Ignition Probability ◽  
Turbine Engine ◽  
Planar Laser

This paper describes experimental measurements of forced ignition of prevaporized liquid fuels in a well-controlled facility that incorporates nonuniform flow conditions similar to those of gas turbine engine combustors. The goal here is to elucidate the processes by which the initially unfueled kernel evolves into a self-sustained flame. Three fuels are examined: a conventional Jet-A and two synthesized fuels that are used to explore fuel composition effects. A commercial, high-energy recessed cavity discharge igniter located at the test section wall ejects kernels at 15 Hz into a preheated, striated crossflow. Next to the igniter wall is an unfueled air flow; above this is a premixed, prevaporized, fuel–air flow, with a matched velocity and an equivalence ratio near 0.75. The fuels are prevaporized in order to isolate chemical effects. Differences in early ignition kernel development are explored using three synchronized, high-speed imaging diagnostics: schlieren, emission/chemiluminescence, and OH planar laser-induced fluorescence (PLIF). The schlieren images reveal rapid entrainment of crossflow fluid into the kernel. The PLIF and emission images suggest chemical reactions between the hot kernel and the entrained fuel–air mixture start within tens of microseconds after the kernel begins entraining fuel, with some heat release possibly occurring. Initially, dilution cooling of the kernel appears to outweigh whatever heat release occurs; so whether the kernel leads to successful ignition or not, the reaction rate and the spatial extent of the reacting region decrease significantly with time. During a successful ignition event, small regions of the reacting kernel survive this dilution and are able to transition into a self-sustained flame after ∼1–2 ms. The low-aromatic/low-cetane-number fuel, which also has the lowest ignition probability, takes much longer for the reaction zone to grow after the initial decay. The high-aromatic, more easily ignited fuel, shows the largest reaction region at early times.

Ignition Probability in a Stratified Turbulent Flow With a Sunken Fire Igniter

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Brandon Sforzo ◽  
Jaecheol Kim ◽  
Jeff Jagoda ◽  
Jerry Seitzman
Keyword(s):  
Transit Time ◽  
High Speed ◽  
Equivalence Ratio ◽  
Imaging Systems ◽  
Flow Temperature ◽  
Ignition Probability ◽  
Turbine Engine ◽  
Reduced Order ◽  
Adverse Conditions ◽  
Transit Times

The evolution of a spark kernel ejected by a sunken fire igniter into a turbulent, fuel–air stratified crossflow was studied both experimentally and using a model in a configuration that is similar to the conditions found in turbine engine combustors. This study allows for variations in the transit time of the kernel across a uniform nonflammable region, before entering a second stream containing a flammable fuel–air mixture. High speed schlieren and emission imaging systems are used to visualize the evolution of the kernel and determine the probability of ignition based on measurements over many spark events. Experiments are performed for a range of mean velocities, transit times, inlet (preheat) temperatures, flammable zone equivalence ratios, and nonflammable zone equivalence ratios. In addition to the typical dependence of ignition on the equivalence ratio of the flammable mixture, the results indicate the strong influence of the kernel transit time and the inlet flow temperature on the probability of ignition. The entrainment between the kernel and the surrounding flow appears to be primarily controlled by the kernel ejection-induced flowfield. Reduced-order modeling suggests that the lowering of the kernel temperature associated with entrainment of the nonflammable mixture significantly reduces the ignition probability, and leads to the conclusion that the presence of fuel close to the igniter is necessary to ensure reliable ignition under adverse conditions.

scholarly journals Large-Eddy Simulation of Light-Round in an Annular Combustor With Liquid Spray Injection and Comparison With Experiments

2017 ◽  
Author(s):  
Théa Lancien ◽  
Kevin Prieur ◽  
Daniel Durox ◽  
Sébastien Candel ◽  
Ronan Vicquelin
Keyword(s):  
Large Eddy Simulation ◽  
Flame Propagation ◽  
High Speed ◽  
Complex Geometry ◽  
Numerical Study ◽  
Ignition Process ◽  
Two Phase ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Annular Combustor

A combined experimental and numerical study of light-round, defined as the flame propagation from burner to burner in an annular combustor, under perfectly premixed conditions has previously demonstrated the ability of large-eddy simulation (LES) to predict such ignition processes in a complex geometry using massively parallel computations. The present investigation aims at developing light-round simulations in a configuration closer to real applications by considering liquid n-heptane injection. The large-eddy simulation of the ignition sequence of a laboratory scale annular combustion chamber comprising sixteen swirled two-phase injectors is carried out with a mono-disperse Eulerian approach for the description of the liquid phase. The objective is to assess this modeling approach to describe the two-phase reactive flow during the ignition process. The simulation results are compared in terms of flame structure and light-round duration to the corresponding experimental images of the flame front recorded by a high-speed intensified CCD camera. The dynamics of the flow is also analyzed to identify and characterize mechanisms controlling flame propagation during the light-round process.

Two-Phase Flow Patterns in a Four by Four Rod Bundle

2006 ◽  
Author(s):  
Yoshitaka Mizutani ◽  
Shigeo Hosokawa ◽  
Akio Tomiyama
Keyword(s):  
Flow Pattern ◽  
High Speed ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Square Lattice ◽  
Phase Flow ◽  
Two Phase ◽  
Local Flow ◽  
Rod Bundle ◽  
Four Square

Air-water two-phase flow patterns in a four by four square lattice rod bundle consisting of an acrylic channel box of 68 mm in width and transparent rods of 12 mm in diameter were observed by utilizing a high speed video camera, FEP (fluorinated ethylene propylene) tubes for rods, and a fiberscope inserted in a rod. The FEP possesses the same refractive index as water, and thereby, whole flow patterns in the bundle and local flow patterns in subchannels were successfully visualized with little optical distortion. The ranges of liquid and gas volume fluxes, <JG> and <JL>, in the present experiments were 0.1 < <JL> < 2.0 m/s and 0.04 < <JG> < 8.85 m/s, which covered typical two-phase flow patterns appearing in a fuel bundle of a boiling water nuclear reactor. As a result, the following conclusions were obtained: (1) the region of slug flow in the <JG> – <JL> flow pattern diagram is so narrow that it can be regarded as a boundary between bubbly and churn flows, (2) the boundary between bubbly and churn flows is close to the boundary between bubbly and slug flows of the Mishima & Ishii’s flow pattern transition model, and (3) the boundary between churn and annular flows is well predicted by the Mishima & Ishii’s model.

A Pressure-Based Two-Phase Flow Method for Computation of Bubble Cavitation Flows

2007 ◽  
Author(s):  
Guoyi Peng ◽  
Ryu Egashira ◽  
Takeru Yano ◽  
Shigeo Fujikawa
Keyword(s):  
High Speed ◽  
Two Phase Flow ◽  
Stokes Equations ◽  
Volume Fraction ◽  
Phase Flow ◽  
State Equations ◽  
Two Phase ◽  
Fluid Mixture ◽  
Local Flow ◽  
Flow Method

A pressure-based two-phase flow method is proposed for computation of high-speed cavitation flows by coupling a Two-Fluids Three-Pressure bubble dynamics model and a compressible two-phase flow computation. The fluid mixture of two-phase media is composed of a liquid and spherical gas bubbles, those are supposed to disperse in the liquid phase uniformly. State equations of the liquid and gas phases are employed to relate their density with pressure, and the flow of two-phase mixture is then calculated by employing Navier-Stokes equations. Cavitation is evaluated by the volume fraction of gas phase and the average radius of cavitation bubbles in a local flow field is calculated by applying Rayleigh-Plesset equation. For simultaneous computation of above equations, a pressure-based predictor-corrector procedure is developed by applying CCUP method. As an example, flows in an orifice nozzle are treated and the reliability of computation is estimated by comparison with experimental data.

Experimental investigation on spark ignition of linear combustor at low pressure conditions

2021 ◽  
pp. 095765092110131
Author(s):  
Kaixing Wang ◽  
Fuqiang Liu ◽  
Haitao Lu ◽  
Jinhu Yang ◽  
Qianpeng Zhao ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Flame Propagation ◽  
Ignition Delay ◽  
High Speed ◽  
Equivalence Ratio ◽  
Early Stage ◽  
Lower Boundary ◽  
Low Pressure ◽  
Air Pressure ◽  
Ignition Process

In order to explore the influence of low pressure on ignition process, the ignition performance of a linear combustor with five burners was experimentally investigated at ambient temperature and low pressure. At air pressure drops of 1%, 2% and 3%, the influence of low pressure on the lower boundary of the ignition equivalence ratio and ignition delay have been carried, and the high-speed camera was used to record the flame propagation at various time. The results indicate that the minimum ignition equivalence ratio increases with the decrease of pressure. And, the lower the pressure, the more obvious the influence of pressure on the ignition boundary. At the same air pressure, the minimum ignition equivalent ratio decreases with the increase of the air pressure drop. For the process of ignition delay, the air pressure mainly affects the evaporation of droplets and the chemical delay process, and the air pressure drop mainly affects the physical delay stage. For the process of flame propagation, the flame moves between adjacent burners in a symmetrical pattern under various pressures. The air pressure mainly affects the ignition delay process, and the air pressure drop influences the ignition delay and the flame propagation in the early stage (the light-around from single burner to three-burners). The time needed to achieve stable combustion is the shortest at the air pressure drop of 2%.

Analysis of the Critical Heat-Flux Condition in High-Pressure Boiling Water Flows

1964 ◽  
Vol 86 (1) ◽  
pp. 23-33 ◽  
Author(s):  
F. E. Tippets
Keyword(s):  
Heat Flux ◽  
High Pressure ◽  
Critical Heat Flux ◽  
High Speed ◽  
Boiling Water ◽  
Two Phase ◽  
Local Flow ◽  
Flow Parameters ◽  
Fluid Properties ◽  
Data Points

Based on the two-phase flow patterns shown in high-speed motion pictures of the process, a general working equation is derived which relates the critical heat flux for high-pressure bulk boiling water in forced convection to the significant local flow parameters and fluid properties. The equation is applied to a representative selection of several hundred data points from the major available sources for the purpose of investigating trends in the data and to test the validity of the equation.

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