Gas Turbine Inlet Air Cooling: Determination of Parameters to Evaluate Fogging Nozzle’s Atomizing Performance

2003 ◽  
Author(s):  
Sanjay Mahapatra ◽  
Jeffrey K. Gilstrap
Keyword(s):  
Gas Turbine ◽  
Surface Area ◽  
Drop Size ◽  
Cone Angle ◽  
Air Cooling ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Droplet Distribution ◽  
Turbine Inlet ◽  
Air Stream

Gas turbine inlet air-cooling using a fogging system is accomplished by using an array of high-pressure nozzles that inject micron-sized droplets in air stream. These droplets evaporate and diffuse in the air stream resulting in cooling and humidification of air. The cooled and moist inlet air increases net turbine power output, improves heat rate and reduces Nitrogen Oxides formation (NOx). The evaporation and mass diffusion of these droplets are influenced, among other factors, by its surface area to volume ratio. Large surface area facilitates drop interfacial heat transfer and smaller volume or weight aids higher droplet residence times. A fogging nozzle’s atomizing performance can be evaluated from its spray properties that include a mean drop size, droplet distribution, numerical droplet density, spray cone angle, and spray penetration. The spray industry adopts various definitions of mean drop size that suits its application and objective. Mean drop sizes or more commonly droplet diameters used in the gas turbine inlet air fogging industry are 90% cumulative volume frequency, Dv0.90 and the Sauter Mean Diameter, D32. Two sprays having identical mean or representative diameter are not necessarily similar in performance. Further, a spray from nozzle ‘A’ having a Dv0.90 less than another nozzle ‘B’ does not necessarily imply that ‘A’ is superior to ‘B’. This paper explains why the use of one or both of the above characteristic diameters does not effectively reflect a fog nozzle’ atomizing performance. This paper also analyzes various characteristic diameters and their relevance to evaporative cooling using fog nozzles. In fogging applications, the smallest and/or the largest sized drops in a spray will have significant impact on performance and neither Dv0.90 nor D32 can independently provide this information. Therefore, at least one other parameter such as the droplet distribution must be known in order to qualitatively define a spray from a fogging nozzle. This paper also determines these parameters such as the Relative Span Factor and Dispersion Boundary Factor and analyzes their importance to fogging performance.

Experimental and Numerical Studies of Diesel Spray Evaporation and Combustion in a Gas Turbine Matrix Burner

2009 ◽  
Author(s):  
Dieter Bohn ◽  
James F. Willie ◽  
Nils Ohlendorf
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Combustion Instability ◽  
Cone Angle ◽  
Spray Angle ◽  
Test Rig ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Flow Simulations ◽  
Air Inlet

Lean gas turbine combustion instability and control is currently a subject of interest for many researchers. The motivation for running gas turbines lean is to reduce NOx emissions. For this reason gas turbine combustors are being design using the Lean Premixed Prevaporized (LPP) concept. In this concept, the liquid fuel must first be atomized, vaporized and thoroughly premixed with the oxidizer before it enters the combustion chamber. One problem that is associated with running gas turbines lean and premixed is that they are prone to combustion instability. The matrix burner test rig at the Institute of Steam and Gas Turbines at the RWTH Aachen University is no exception. This matrix burner is suitable for simulating the conditions prevailing in stationary gas turbines. Till now this burner could handle only gaseous fuel injection. It is important for gas turbines in operation to be able to handle both gaseous and liquid fuels though. This paper reports the modification of this test rig in order for it to be able to handle both gaseous and liquid primary fuels. Many design issues like the number and position of injectors, the spray angle, nozzle type, droplet size distribution, etc. were considered. Starting with the determination of the spray cone angle from measurements, CFD was used in the initial design to determine the optimum position and number of injectors from cold flow simulations. This was followed by hot flow simulations to determine the dynamic behavior of the flame first without any forcing at the air inlet and with forcing at the air inlet. The effect of the forcing on the atomization is determined and discussed.

scholarly journals Dynamic Response of Fuel Nozzles for Liquid-Fueled Gas Turbine Combustors

1996 ◽  
Author(s):  
Mounir Ibrahim ◽  
Terry Sanders ◽  
Douglas Darling ◽  
Michelle Zaller
Keyword(s):  
Gas Turbine ◽  
Cone Angle ◽  
Outer Region ◽  
Test Fluid ◽  
Mean Flow ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Gas Turbine Combustors ◽  
The Mean ◽  
Piezoelectric Drive

To imitate resonances that might occur in the fuel delivery system of gas turbine combustors, the incoming liquid streams of two pressure swirl nozzles were perturbed using a piezoelectric driver. Frequencies of perturbations examined were from 3 to 20 kHz, and water was used as the test fluid. A video camera and a Phase Doppler Particle Analyzer (PDPA) were used to study the effect of perturbations on the mean flow quantities of the sprays. Various lighting arrangements were used for the video photography: back lighting, front lighting, a strobe synchronized with the input to the piezoelectric, and a laser sheet oriented along the midplane of the sprays. The study showed that the piezoelectric drive had an effect an the spray system at discrete frequencies. At these particular frequencies, by increasing the input voltage, it was found that the piezoelectric drive affected the atomization in the following ways: (1) the mean flow rate decreased, (2) the spray cone angle decreased, (3) the break up length decreased, (4) the peak of the spatial distribution of the mean droplet size decreased, and (5) the mean droplet sizes and velocities increased near the spray center line and decreased in the outer region of the spray. A hysteresis effect of the drive frequency on the spray cone angle was observed. The results indicated that more fundamental research is needed to gain an in-depth understanding of the physical processes induced in the spray by the piezoelectric drive.

scholarly journals Calculation of flow characteristics of liquid fuel supplied through pressure jet atomizers of small-sized gas turbine engines

2021 ◽  
Vol 20 (2) ◽  
pp. 19-35
Author(s):  
N. I. Gurakov ◽  
I. A. Zubrilin ◽  
M. Hernandez Morales ◽  
D. V. Yakushkin ◽  
A. A. Didenko ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Liquid Fuel ◽  
Cone Angle ◽  
Flow Characteristics ◽  
Design Parameters ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Semi Empirical

The paper presents the results of studying the flow characteristics of liquid fuel in pressure jet atomizers of small-sized gas turbine engines with nozzle diameters of 0.4-0.6 mm for various operating and design parameters. The study was carried out using experimental measurements, semi-empirical correlations and CFD (computational fluid dynamics) methods. The Euler approach, the volume- of- fluid (VOF) method, was used to model multiphase flows in CFD simulations. Good agreement was obtained between experimental and predicted data on the fuel coefficient and the primary spray cone angle at the nozzle outlet. Besides, the assessment of the applicability of semi-empirical techniques for the nozzle configurations under consideration is given. In the future, the flow characteristics in question (the nozzle flow rate, the fuel film thickness, and the primary spray cone angle) can be used to determine the mean diameter of the droplets (SMD) required to fully determine the boundary conditions of fuel injection when modeling combustion processes in combustion chambers of small-sized gas turbine engines.

Influence of Ambient Air Pressure on Pressure-Swirl Atomization

1987 ◽  
Author(s):  
X. F. Wang ◽  
A. H. Lefebvre
Keyword(s):  
Drop Size ◽  
Cone Angle ◽  
Ambient Air ◽  
Air Pressure ◽  
Spray Angle ◽  
Flow Number ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Continuous Increase ◽  
Pressure Swirl

The spray characteristics of six simplex atomizers are examined in a pressure vessel using a standard light diffraction technique. Attention is focused on the effects of liquid properties, nozzle flow number, spray cone angle, and ambient air pressure on mean drop size and drop-size distribution. For all nozzles and all liquids it is found that continuous increase in air pressure above the normal atmospheric value causes the SMD to first increase up to a maximum value and then decline. An explanation for this characteristic is provided in terms of the measurement technique employed and the various competing influences on the overall atomization process. The basic effect of an increase in air pressure is to improve atomization, but this trend is opposed by contraction of the spray angle which reduces the relative velocity between the drops and the surrounding air, and also increases the possibility of droplet coalescence.

Atomization Characteristics of Jatropha-Derived Alternative Aviation Fuels From Aircraft Engine Injector

2017 ◽  
Author(s):  
Ramachandran Sakthikumar ◽  
Deivandren Sivakumar ◽  
B. N. Raghunandan ◽  
John T. C. Hu
Keyword(s):  
Size Distribution ◽  
Drop Size ◽  
Cone Angle ◽  
Fuel Spray ◽  
Jet Fuels ◽  
Spray Characteristics ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Atmospheric Air ◽  
Atomization Characteristics

Search for potential alternative jet fuels is intensified in recent years to meet stringent environmental regulations imposed to tackle degraded air quality caused by fossil fuel combustion. The present study describes atomization characteristics of blends of jatropha-derived biofuel with conventional aviation kerosene (Jet A-1) discharging into ambient atmospheric air from a dual-orifice atomizer used in aircraft engines. The biofuel blends are characterized in detail and meet current ASTM D7566 specifications. The experiments are conducted by discharging fuel spray into quiescent atmospheric air in a fuel spray booth to measure spray characteristics such as fuel discharge behavior, spray cone angle, drop size distribution and spray patternation at six different flow conditions. The characteristics of spray cone angle are obtained by capturing images of spray and the measurements of spray drop size distribution are obtained using laser diffraction particle analyzer (LDPA). A mechanical patternator system comprising 144 measurement cells is used to deduce spray patternation at different location from the injector exit. A systematic comparison on the atomization characteristics between the sprays of biofuel blends and the 100% Jet A-1 is presented. The measured spray characteristics of jatropha-derived alternative jet fuels follow the trends obtained for Jet A-1 sprays satisfactorily both in qualitative and quantitative terms.

Influence of Geometric Features on the Performance of Pressure-Swirl Atomizers

1990 ◽  
Vol 112 (4) ◽  
pp. 579-584 ◽  
Author(s):  
S. K. Chen ◽  
A. H. Lefebvre ◽  
J. Rollbuhler
Keyword(s):  
Drop Size ◽  
Cone Angle ◽  
Diameter Ratio ◽  
Working Fluid ◽  
Spray Characteristics ◽  
Spray Cone Angle ◽  
Liquid Distribution ◽  
Spray Cone ◽  
Pressure Swirl ◽  
Discharge Orifice

The spray characteristics of several different simplex pressure-swirl nozzles are examined using water as the working fluid. Measurements of mean drop size, dropsize distribution, effective spray cone angle, and circumferential liquid distribution are carried out over wide ranges of injection pressure. Eight different nozzles are employed in order to achieve a wide variation in the length/diameter ratio of the final discharge orifice. Generally, it is found that an increase in discharge orifice length/diameter ratio (lo/do) increases the mean drop size in the spray and reduces the spray cone angle. The circumferential liquid distribution is most uniform when lo/do=2. If lo/do is raised above or lowered below this optimum value, the circumferential uniformity of the liquid distribution is impaired. The observed effects of lo/do on spray characteristics are generally the same regardless of whether the change in lo/do is accomplished by varying lo or do.

Experiments on Spray Interactions in the Wake of a Bluff Body

1988 ◽  
Vol 110 (1) ◽  
pp. 86-93 ◽  
Author(s):  
R. C. Rudoff ◽  
M. J. Houser ◽  
W. D. Bachalo
Keyword(s):  
Drop Size ◽  
Bluff Body ◽  
Cone Angle ◽  
Field Interaction ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
General Direction ◽  
Size Classes ◽  
Toroidal Vortices ◽  
Spray Field

The dynamics of spray drop interaction within the turbulent wake of a bluff body were investigated using the Aerometrics Phase Doppler Particle Analyzer, which determines both drop size and velocity. Detailed measurements obtained included spray drop size, axial and radial velocity, angle of trajectory, and size-velocity correlations. The gas-phase flow field was also ascertained via the behavior of the smallest drops. Results showed dramatic differences in drop behavior when interacting with turbulence for the various size classes. Small drops were recirculated in a pair of toroidal vortices located behind the bluff body, whereas the larger drops followed the general direction of the spray cone angle. This was documented via backlit photography. Local changes in number density were produced as a result of lateral convection and streamwise accelerations and decelerations of various drop size classes. The spray field interaction illustrated by these data effectively reveals the complexity associated with the development of the spray and casts some doubts toward attempting to describe sprays via simple integral quantities such as the Sauter mean diameter.

scholarly journals Prediction of the Initial Drop Size and Velocity Distribution in the Cold Cryogenic Spray

2020 ◽  
Vol 38 (3) ◽  
pp. 629-640
Author(s):  
Ahmed Abed Al-Kadhem Majhool ◽  
Noor Mohsin Jasim
Keyword(s):  
Velocity Distribution ◽  
Size Distribution ◽  
Liquid Nitrogen ◽  
Drop Size ◽  
Maximum Entropy Method ◽  
Cone Angle ◽  
Injection Pressure ◽  
Entropy Method ◽  
Spray Cone Angle ◽  
Spray Cone

The polydispersed nature of the spray is captured through the use of probability density functions based on the maximum entropy method to stand for the complete atomization characteristics of spray dynamics. The droplet and velocity size distributions are practical tools for the analysis of sprays cooling. The special benefit of the model is a Eulerian based which is less computationally intensive when compared to models that are based on the Lagrangian approach that tracks droplet parcel. The accuracy of using Lagrangian approach in polydispersed phase is always accurately less than Eulerian approach because it depends on the number of parcels while in Eulerian approach it depends on the proposed continuous distribution function. The main intent of the current work is to evaluate the capability of using the model for the initial predictions of the droplet size and velocity distribution for liquid nitrogen spray of solid-cone pressure swirl nozzle. The use of liquid injection pressure cases of up to 0.6MPa and spray cone angles of just 30◦ from three different sets of experimental data. The results being characterized are spray drop size distribution, liquid volume fraction and spray cone angle values. The unsteady analyses of the effect of injection pressure are studied on the cryogenic liquid nitrogen. The numerical results show that the maximum entropy method applies to liquid cryogenic spray and indicates that the model reacts correctly to changes in different injection pressures. Comparisons are also made with measured drop size distribution data that are reasonably captured and the spray cone angle is found to be in good agreement during initial and far-field spray angles.

Gas Turbine Inlet Air Fogging Systems: Application of Psychrometric Principles to Study Cooling and Humidification Processes

2003 ◽  
Author(s):  
Sanjay Mahapatra ◽  
Jeffrey K. Gilstrap
Keyword(s):  
Moisture Content ◽  
Gas Turbine ◽  
Latent Heat ◽  
Liquid Water ◽  
Air Cooling ◽  
Sensible Heat ◽  
Control Logic ◽  
Saturation Process ◽  
Turbine Inlet ◽  
Air Stream

Gas turbine inlet air-cooling utilizing a high pressure fogging system is theoretically based on the thermodynamic principle of adiabatic saturation. The dry bulb temperature of inlet air decreases by losing its sensible heat to the liquid water droplets generated by the fogging system. This sensible heat is enough to provide the latent heat necessary to evaporate and diffuse these droplets into the surrounding air stream. As a result of this heat interchange accomplished through a complex mechanism of heat transfer and fluid dynamics, the temperature and moisture content of inlet air is decreased & increased respectively resulting in an increase in its density. Neglecting the enthalpy of liquid water, which is insignificant compared to the water’s latent heat of vaporization, the total heat, i.e. enthalpy of the air stream remains unchanged. The net heat exchange outside of this control volume is zero because the droplets, which subsequently diffuse into the air stream, gain the sensible heat lost by inlet air. Therefore, the theoretical concept of adiabatic saturation is valid in this case. However, in real systems, the cooling and humidification process is seldom adiabatic. This paper applies psychrometric principles in conducting a detailed mathematical analysis of various cooling and humidification processes accomplished by fogging systems. The measurement of actual moisture content of air upstream and downstream of a fogging system is vital to gas turbine inlet air-cooling. The moisture content of air and its dry bulb temperature can provide accurate information on the system path and how well it approximates the adiabatic saturation process and determining system efficiency. The deviation from the adiabatic saturation process is attributed to several factors, such as external heat gain or loss, water temperature, etc. The measurement of moisture content can enable the fogging system control logic to control the required water flow rate through the system to obtain maximum performance without over spraying excessive water or under cooling inlet air. This paper presents possible scenarios of deviation from an adiabatic process and methods to determine fogging system total effectiveness.

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