Investigation of Spray Formation and Turbulent Droplet Transport in High Momentum Jet Stabilized Combustor Injection Systems

Abstract This work investigates the influence of coaxial air flow on droplet distribution, velocity, and size generated by a pressure-swirl atomizer. The experiments were performed inside a generic test section with large optical access at atmospheric conditions. The flow conditions replicate the mixing duct sections of high momentum jet stabilized combustors for gas turbines, e.g. high axial air velocities without swirl generation and high preheat temperatures. High momentum jet stabilized combustors based on the FLOX® burner concept are used successfully in gas turbines due to its fuel and load flexibility and very low pollutant emissions. In previous and ongoing studies, different model combustors have been under investigation mainly with the focus of broadening fuel flexibility and operational limits. Operation with different liquid fuel injection systems in high pressure experiments showed a significant impact from the injector shape and injection strategy on the fuel air mixing behavior, the flame position and stability, and thus NOx emissions. This experiment will give a more detailed understanding of the turbulent mixing and interaction of primary and secondary atomization with the surrounding air in such burners. The setup will also allow for the testing of different injection systems for various burner configurations by the variation of injection type, location, fuel, and air flow properties. In the present experiments a pressure-swirl atomizer was set to a constant pressure drop and mass flow. Liquid fuel was replaced by deionized water due to safety concerns. The coaxial air mass flow was preheated up to 473 K and set to bulk velocities of 20 m/s, 50 m/s, and 80 m/s. Particle Image Velocimetry (PIV) was used to characterize the flow field downstream of the point of injection. The droplet size and velocity distributions were quantified by double frame shadow imaging combined with a long-distance microscope with a resolution below 1 μm per pixel. Moreover, the formation of ligaments as well as primary spray break-up was visualized. The results show a significant change of the spatial droplet distribution with increasing co-flow velocity for a given atomizer geometry. The spray cone angle widens at high co-flow velocities due to the formation of a pronounced recirculation zone behind the backward facing step of the injector near the nozzle orifice. This also leads to a change in the initial droplet momentum and the spatial distribution of large droplets. Smaller droplets are concentrated to the center of the spray due to turbulent transport. These findings assist the ongoing developments of liquid fuel injection systems for high momentum jet based combustors and provide validation data for numerical simulations of primary and secondary atomization.

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Hybrid Pressure-Swirl/Twin-Fluid Atomizer for Emission Controls

Energy Conversion and Resources ◽

10.1115/imece2006-13360 ◽

2006 ◽

Author(s):

Andrew C. S. Lee ◽

Paul E. Sojka

Keyword(s):

Flow Field ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Drop Size ◽

Air Flow ◽

Exit Plane ◽

Swirl Atomizer ◽

Pressure Swirl ◽

Pressure Swirl Atomizer

An experimental study was conducted to characterize the performance of a hybrid atomizer used in emission control devices. Characterization included drop size distribution, measured using a forward light-scattering instrument, the air flow field (axial and radial velocities), measured using 2-D PIV, and turbulence characteristics of the air flow field, measured using LDA. The air flow field showed characteristics common to turbulent free round jets beyond approximately 8 exit orifice diameters from the atomizer exit plane. The centerline velocity increased with an increase in mass flow rate, while radial velocities were two orders of magnitude smaller than centerline values. The jet spreading factor initially increased with an increase in axial distance from the exit; however, it stabilized at a value of 0.09 at z/Do=11.8. Turbulence intensity along the jet centerline stabilized at 25% at z/Do=7.9. Drop size data showed complex dependencies on liquid and air mass flow rates, and on internal geometry. The influence of liquid mass flow rate on drop size was significantly smaller for the hybrid atomizer than for the pressure swirl atomizer component housed inside the hybrid unit, thus indicating a higher turndown ratio for the hybrid device. Drop size distributions produced by the hybrid atomizer showed multiple peaks, indicating there is more than one important atomizing mechanism. Finally, reducing the gap between the pressure-swirl atomizer and the exit plane of the outer casing resulted in a reduction in drop size.

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A study on the geometric characteristic influence on the liquid fuel flow in a three-way pressure-swirl atomizer

Journal of Physics Conference Series ◽

10.1088/1742-6596/1891/1/012021 ◽

2021 ◽

Vol 1891 (1) ◽

pp. 012021

Author(s):

N I M Gurakov ◽

Hernandez Morales ◽

I A Zubrilin ◽

S A Bolychev ◽

A A Didenko ◽

...

Keyword(s):

Liquid Fuel ◽

Geometric Characteristic ◽

Fuel Flow ◽

Swirl Atomizer ◽

Pressure Swirl ◽

Pressure Swirl Atomizer

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Influence of Ambient Air Pressure on Pressure-Swirl Atomizer Spray Characteristics

Volume 2: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations ◽

10.1115/2001-gt-0043 ◽

2001 ◽

Author(s):

Arvind K. Jasuja ◽

Arthur H. Lefebvre

Keyword(s):

Gas Turbines ◽

Drop Size ◽

Cone Angle ◽

Ambient Air ◽

Air Pressure ◽

Spray Characteristics ◽

Spray Cone ◽

Swirl Atomizer ◽

Pressure Swirl ◽

Pressure Swirl Atomizer

A single-component PDPA is used to evaluate the spray characteristics of a simplex pressure-swirl atomizer when operating at high liquid flow rates and elevated ambient air pressures. Attention is focused on the effects of air pressure on mean drop size, drop-size distribution, mean velocity, volume flux, and number density. Using a constant flow rate of 75 g/s, measurements are carried out along the spray radii at a fixed distance downstream from the atomizer face of 50 mm. The air pressures of 1, 8, and 12 bars chosen for these tests correspond to air densities of 1.2, 9.6, and 14.4 kg/m3. The purpose of the investigation is to supplement the existing body of information on pressure-swirl spray characteristics, most of which were obtained at normal atmospheric ambient pressures, with new data that correspond more closely to the conditions prevailing in the primary combustion zones of modern gas turbines. The results obtained are explained mainly in terms of the influence of air pressure on spray structure, in particular spray cone angle and Weber number.

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Verification of Single Digit Emission Performance of a 24 MW Gas Turbine: SGT-600 3rd Generation DLE

Volume 4A: Combustion, Fuels and Emissions ◽

10.1115/gt2017-63089 ◽

2017 ◽

Author(s):

Arturo Manrique Carrera ◽

Philipp Geipel ◽

Anders Larsson ◽

Rikard Magnusson

Keyword(s):

Gas Turbine ◽

Gas Turbines ◽

Liquid Fuel ◽

Fuel Injection ◽

Injection System ◽

Combustion System ◽

Single Digit ◽

2Nd Generation ◽

Droplet Distribution ◽

Industrial Gas Turbine

The SGT-600 3rd generation DLE is a 24 MW industrial gas turbine which was recently upgraded from the SGT-600 2nd generation DLE. The upgraded SGT-600 is an addition to the existing low emissions gas turbine portfolio within Siemens. The objectives of the engine upgrade focused on increasing the lifetime of the components, lowering emissions and improving liquid fuel operation. In order to accomplish these objectives the combustion system was fully replaced, an improved gas fuel distribution was implemented and the first stage of the turbine was replaced. Furthermore, the liquid fuel injection system was enhanced in terms of fuel droplet distribution. Both gas and liquid fuel operation were confirmed in Siemens industrial gas turbine test facility located in Finspong, Sweden. The upgraded combustion system originates from the SGT-700 gas turbine, a 33MW class engine, which consists of 18 “3rd generation DLE” burners that replaced the original “2nd generation DLE” ones that are normally incorporated in the SGT-600 DLE gas turbines. The first stage of the turbine has also been improved and less air is needed for cooling purposes. Moreover, an additional update on the compressor air bleed control was implemented. The liquid fuel burner hardware was optimized with new fuel injection lances manufactured by electron erosion techniques in order to improve the droplet distribution. The SGT-600 3rd generation DLE is capable to operate in single digit conditions both in NOx and CO from 100% to 70% load and it is possible to extend single digit operation on NOx down to 50% load. CO emissions are below 80ppm at 50% load which is in compliance with current European regulation. Concerning liquid fuel operation the SGT-600 3rd generation DLE does not use water injection for emission control and is capable to reach below 58ppm NOx at full load while keeping CO below 40ppm down to 75% load. The present work describes the main modifications performed during the engine upgrade and the results of the performed engine tests. Finally, it should be noted that the SGT-600 3rd generation DLE is an excellent example of the development/upgrade efforts within Siemens AG. The commercialization process of the SGT-600 3rd generation DLE has been initiated and three engines are already in commercial operation up to date, and two units will be installed in the near future.

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A Study of Supercritical Jet Fuel Injection

Volume 6: Energy Systems: Analysis, Thermodynamics and Sustainability ◽

10.1115/imece2007-43445 ◽

2007 ◽

Cited By ~ 1

Author(s):

R. R. Rachedi ◽

L. Crook ◽

P. E. Sojka

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Cone Angle ◽

Density Ratio ◽

Swirl Number ◽

Penetration Length ◽

Swirl Atomizer ◽

Pressure Swirl ◽

Pressure Swirl Atomizer

An experimental investigation was conducted to examine the behavior of supercritical fluid (SCF) jets injected into supercritical environments. The behavior of the fluid, JP-10, was studied after it was passed through a pressure-swirl atomizer and entered a nitrogen environment. SCF jet behavior was characterized by the jet cone angle and penetration length. Cone angle and penetration length are reported as functions of density ratio (defined as the ratio of density of the injected fuel to the nitrogen environment), fuel mass flow rate, and pressure-swirl atomizer internal geometry. The density ratio was varied by altering the reduced temperature of the fuel (1.01<Tr<1.10) and nitrogen environment, while keeping the fuel reduced pressure constant at 1.05. Fuel mass flow rate ranged from 1.0 to 3.0 g/s (7.94 to 23.8 lbs/hr). Pressure-swirl atomizer internal geometry was varied by controlling the swirl number, ranging from straight bore to Sn=1.0. It was found that increasing the swirl number for a SCF fluid has the largest effect on jet cone angle, followed by a change in the density ratio; the mass flow rate had the least effect. The penetration length of the SCF jet increased when either the mass flow rate or density ratio increased. The mass concentration field significantly widens when the swirl number of the injector increased, as opposed to changes in the mass flow rate or density ratio which were found to have little effect.

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Evaluation of Spray Characteristics in Pharmaceutical Tablet Coating Processes: The Influences of Drum Rotational Speed and Drying Air Flow Rate

Volume 3: Combustion Science and Engineering ◽

10.1115/imece2009-12678 ◽

2009 ◽

Author(s):

Ariel R. Muliadi ◽

Paul E. Sojka

Keyword(s):

Drop Size ◽

Air Flow ◽

Air Pressure ◽

Volume Flux ◽

Supply Rate ◽

Drop Velocity ◽

Pan Coater ◽

Swirl Atomizer ◽

Pressure Swirl ◽

Pressure Swirl Atomizer

In this study, drop size, velocity, and volume flux for sprays produced by a pharmaceutical nozzle (Spraying Systems 1/4-JAU-SUE15A-PA67288–45°-SS) were characterized using a Fiber-PDA system (Dantec). Spraying was performed in a 120 cm (24 in) diameter tablet pan-coater (Accela-Cota Model 10, Thomas Engineering, UK). The separate influences of drum rotational speed and drying air flow rate were studied by making measurements at four different pan-coater operating conditions: stationary drum with drying air turned on/off, and 8 rpm rotating drum with drying air turned on/off. For each case, four different spraying conditions (liquid supply rate and atomizing air pressure) were used. PDA scans were performed along the spray semi-major and semi-minor axes at two different axial distances (7.5 and 10 cm) from the atomizer tip. Results were as follows. When both the drying air and drum rotation were absent, increasing liquid supply rate while operating the atomizer at the lower of two atomizing air pressures decreased drop size. The opposite occurred when operating at the higher of the two atomizing air pressures. This suggests that the nozzle operated as a simplex pressure-swirl atomizer at lower levels of atomizing air pressure, but as an air-assist atomizer at higher levels of atomizing air pressure. Regardless, liquid supply rate had no significant effect on drop velocity. In contrast, a decrease in atomizing air pressure or an increase in axial distance always led to an increase in drop size and a decrease in drop velocity. Supplying drying air to the pan-coater resulted in up to a 6 m/s increase in drop velocity, but had mixed effects on drop size. When the spray gun was operated as an air assist atomizer, supplying drying air to the drum led to an increase in D32. The reverse was observed when the gun operated as a simplex pressure-swirl atomizer. These two observations are most evident when operating at the lower liquid supply rate (70 g/min), suggesting that they may have arisen from drop evaporation. Increasing the drying air supply rate also reduced spray extent and volume flux magnitude. Adding drum rotation to the process generally led to (i) increased drop size and (ii) increased drop velocity. (i) likely arose from the transport of small drops away from the spray zone, while (ii) likely resulted from changes in droplet trajectories. Both are the result of the gas-phase swirling motion that is due to the drum rotation. (i) was most noticeable when the nozzle was operated as an air-assist atomizer. In addition, drum rotation decreased spray volume flux magnitude at the spray center, but increased it at other locations, essentially making the spray more dumbbell-shaped. Finally, the influence of drum rotation on drop velocity diminished when drying air flow was included. This was because the drying air momentum helped the drops oppose the effects of the swirling flow induced by the drum rotations.

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A Computational Fluid Dynamics-based Correlation to Predict Droplet Sauter Mean Diameter for Σ− Yliq Atomization Model in Pressure Swirl Atomizer

European Journal of Engineering and Technology Research ◽

10.24018/ej-eng.2021.6.7.2645 ◽

2021 ◽

Vol 6 (7) ◽

pp. 69-76

Author(s):

Sherry K. Amedorme ◽

Joseph Apodi

Keyword(s):

Fluid Dynamics ◽

Fuel Injection ◽

Liquid Velocity ◽

Operating Conditions ◽

Sauter Mean Diameter ◽

Design Variables ◽

Mean Diameter ◽

Swirl Atomizer ◽

Pressure Swirl ◽

Pressure Swirl Atomizer

Liquid atomization is crucial to ensure efficient combustion as it is an inherent part of the injector system. The combustion of fuels relies on effective atomization to increase the surface area of the fuel and consequently achieve high rates of mixing and evaporation. Pressure swirl atomizers are inexpensive and reliable type of atomizer for fuel injection owing to its superior atomization characteristics and relatively simple geometry. The Sauter mean diameter (SMD) of atomizer contributes significantly to the combustion chamber performance. This paper presents a two-step strategy to predict droplet SMD for atomisation model in pressure swirl atomizer through the combination of experimentally validated Computation Fluid Dynamics (CFD) and Optimal Latin Hypercubes (OLHC) Design of Experiments (DoE) techniques. A three-dimensional Eulerian two-phase CFD model is developed to account for liquid and gas phases as a single continuum with high-density variation at large Reynolds and Weber numbers and validated against experimental measurements, before being employed to carry out a parametric study involving operating conditions and fluid properties of the pressure swirl atomizer. The atomizer is then represented in terms of four design variables, namely liquid viscosity, liquid velocity, surface tension and atomizer exit diameter. An 87-point OLHC DoE is constructed within the design variables space using a permutation genetic algorithm resulting in an accurate SMD prediction. Results show the newly developed SMD prediction is found to be superior compared with existing correlations and indicate significant improvement in the droplets SMD.

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