Structure and Mass Flux Distribution of a Side-opened Hollow Cone Spray Generated by Swirl Pressure Atomizers (original) (raw)
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Effects of Flow and Atomizer Parameters on the Spray Cone Angle in a Hollow Cone Swirl Atomizer
2018
The experimental and numerical studies have been carried out to determine the influences of nozzle flow and nozzle geometry on the spray cone angle in a hollow cone swirl atomizer. The numerical study is based on the solution of conservation equations for mass and momentum and k-ε model is adopted for turbulent quantities. Experiments have been carried out with a number of nozzles fabricated by Perspex material. The spray cone angle has been measured from the photographs of spray at outside the nozzle taken by a camera. From both numerical and experimental studies the value of spray cone angle from an atomizer is found to increase sharply with an increase in inlet Reynolds number Re at its lower range but become almost constant with Re at its higher range. The spray cone angle increases with an increase in the value of Do/Ds or α and it decreases with an increase in the value of Dp/Ds or Lo/Ds.
AIAA Propulsion and Energy 2019 Forum, 2019
I would like to express my sincere to my colleagues at TÜBİTAK SAGE, especially Bora YAZICI, for their crucial advises during the preparation of this thesis. I would like to thank my mother Nihayet TOKGÖZ, my father Naci TOKGÖZ, my sister Burcu TOKGÖZ and my brother Alp Tugay TOKGÖZ for their continuous support and encouragement through my life. Special thanks go to my wife, Semra GÜMRÜK TOKGÖZ, for her understanding, patience, support, and love during this difficult period. Finally, this thesis is dedicated to my family. It would be impossible without their support and understanding. xi TABLE OF CONTENTS
Influence of liquid properties on the characteristics of hollow cone swirl spray
Pressure swirl atomizers discharging hollow cone liquid spray are commonly employed in aircraft gas turbine engines as fuel injectors. Studies on the characteristics of fuel spray discharging from such atomizers assume significance from the view of combustion considerations. The present study deals with an experimental study analyzing the role of liquid properties on the characteristics of swirling spray from an aircraft engine simplex atomizer. The experiments are carried out by discharging spray into quiescent atmospheric air at varying flow rate conditions with different liquids (pure water, water-glycerol mixture, and Jet A-1 fuel). Experimental measurements to describe the breakup process of conical liquid film and the characteristics of spray drop size are deduced with the aid of backlighting photographic technique and laser diffraction instrument Spraytec. A systematic analysis is carried out to elucidate the role of liquid properties on the sheet breakup and spray drop size characteristics. The observed trends on the variation of spray characteristics with varying flow conditions are explained by adopting already existing theoretical model on liquid sheet breakup and empirical correlations on mean drop size developed for sprays from pressure swirl atomizers.
Characteristics of spray angle for effervescent-swirl atomizers
Chemical Engineering and Processing: Process Intensification, 2015
This paper draws a link between the liquid viscosity and the spray angle for effervescent and effervescent-swirl atomizers. The spray angle determines the dispersion and coverage area of the resultant sprays. The swirling the gas-liquid mixture in atomizer led to a significant increase of the spray cone angle at low gas to liquid ratio by mass. Additionally, the orifice shape plays an important role in obtaining the spray angle. The highest values of spray angle has occurred during atomization using profiled orifice. Mathematical analysis shows that spray angle depends on the liquid viscosity, the gas and liquid flow rates and the construction of the atomizer. The data obtained are very important from point of view of the design of atomizers and coverage area of spray. 2015 Elsevier B.V. All rights reserved.
2012
This study investigated characteristics of sprays generated with two geometrically different pressure-swirl atomizers for a small-sized aviation turbine engine using Particle Image Velocimetry (PIV) and Phase-Doppler Anemometry (PDA). The former nozzle is a spill-return type; the latter one is the intended upgrade without the spill return. Single-camera and stereoscopic PIV measurements yield distribution of mean velocity measured in an axial cross section of the spray cone. PDA measurements yield drop-size distribution and axial velocity data. Performed measurements revealed significant differences in spray characteristics of the measured nozzles investigated in the same operating regimes on a cold test bench. These differences are discussed in detail. Analysis of differences between the two nozzles elucidates the possible impact of the nozzle replacement on the combustion process. This study provides an extensive database for validation of numerical models of the tested nozzles.
The influence of spill-line geometry on a spray generated by a pressure-swirl atomizer
EPJ Web of Conferences, 2016
An experimental investigation of characteristics of spray generated by a pressure-swirl atomizer (spill-return type) was performed using shadowgraphy and Phase-Doppler Anemometry (PDA). Several different geometries of the spill-return orifice were tested in terms of a spray stability and quality on a cold test bench. PDA measurement yields a drop-size distribution and velocity data while the shadowgraphy unveils a break-up process in detail. Performed measurements reveal significant differences in spray characteristics as well as differences in spray stability. The results suggest that the air core, formed inside the swirl chamber, passes through the spill orifice, which causes instability of the inner flow. These instabilities lead to a chaotic state of sheet breakup resulting in shortening of breakup distance. Obtained findings are used to propose possible changes in the atomizer design for improvement of its performance. This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits distribution, and reproduction in any medium, provided the original work is properly cited.
In this work an advanced atomizer concept to control the spray formation for heterogeneous spray combustion is investigated. The objective is to address the spray structure that preserves the flame height and modifies the width of the flame. The atomizer concept for formation of a modified spray combines a swirling liquid film generation that is atomized by an external swirling gas flow. To investigate the main characteristics of the combined atomizer, experiments and numerical simulations of the flow operation with different geometric nozzle parameters (number of gas holes) and process parameters (flow rate of liquid and gas) as well as liquid properties are carried out to produce a modified, enlarged and steady spray of small droplets. In this work, three different liquids (water without and with 40% and 60% weight of glycerol) are used as the liquid phase and air as the gas phase. In the simulations, the multiphase flow is modeled by an Eulerian-Lagrangian approach with two-way c...
IOP Conference Series: Materials Science and Engineering, 2019
Spraying dispersed fluid by swirl atomizer into a main gas stream in order to obtain homogeneous blended flow within a restricted distance from the atomizer position is a significant issue. The dispersal of sprayed fluid mass-flux from the atomizer should be correlated to mass flux distribution of the main flow gas. Consequently, it is essential to control the distribution of liquid mass flux from the injector to match the distribution of main gas flux to attain perfect mixing with identical liquid/gas mass flux ratio all over the pipe. The present study examines the liquid mass flux pattern injected from tapered swirl atomizer having various cut shapes. A mathematical approach to circumferentially evaluate the outlet mass fraction distribution from generalized tapered nozzle cut was analyzed. The derived mass fraction distribution equation is dependent on the flow-angle, the cut-angle, and the arc-angle. A CFD simulation was performed to evaluate the flow angle at the outlet from t...
Spray structure of a pressure-swirl atomizer for combustion applications
EPJ Web of Conferences, 2012
In the present work, global as well as spatially resolved parameters of a spray produced by a pressure-swirl atomizer are obtained. Small pressure-swirl atomizer for aircraft combustion chambers was run on a newly designed test bench with Jet A-1 kerosene type aviation fuel. The atomizer was tested in four regimes based on typical operation conditions of the engine. Spray characteristics were studied using two optical measurement systems, Particle Image velocimetry (PIV) and Phase-Doppler Particle Analyzer (P/DPA). The results obtained with P/DPA include information about Sauter Mean Diameter of droplets and spray velocity profiles in one plane perpendicular to the spray axis. Velocity magnitudes of droplets in an axial section of the spray were obtained using PIV. The experimental outputs also show a good confirmation of velocity profiles obtained with both instruments in the test plane. These data together will elucidate impact of the spray quality on the whole combustion process, its efficiency and exhaust gas emissions. Pressure-swirl atomizers as relatively old type of atomizing devices are nowadays often being replaced in many applications by twin-fluid atomizers. But they are still very common parts of present combustion systems mainly for low power demands. Their popularity is based on simple design and operation without additional expensive devices that could lead to unwanted increase of weight in mobile applications and also to reduction of reliability, which are important factors not only in aircraft industry. Research works focused on improvement of atomization characteristics of the pressure-swirl atomizers are persistent despite long-lasting history of their development and utilization in many industrial sectors. Today research effort stems from changes in the legislative, reflects more frequent usage of less refined fuels and answers requirements for more efficient combustion devices. In general, a swirl-flow of the liquid in a pressure-swirl atomizer is induced by feeding the liquid into a swirl chamber through one or several tangential ports, that give it high angular velocity, thereby creating an air-cored vortex. In this manner, the air-core blocks a part of the nozzle outlet orifice. Under both axial and radial forces emerges the fuel through this orifice in the form of a hollow conical sheet. As the sheet expands, its thickness decreases and it soon becomes unstable and disintegrates into ligaments and then drops in the form of a well-defined hollow-cone spray. Disintegration of the sheet depends mainly on the liquid discharge velocity and thus on the liquid injection pressure. Description of the spray development with increasing injection pressure is presented, for