Plain Jet Research Articles

Controlling sonic rectangular jet with nozzle trailing edge modification

Sonic rectangular jet emanating from a convergent nozzle of aspect ratio 2 with modified trailing edge in the form of triangular extension on its widest side is investigated experimentally at different nozzle pressure ratios corresponding to underexpanded states of sonic jet. To assess the impact of trailing edge modification on jet mixing, the sonic rectangular jet from aspect ratio two plain convergent nozzle (without trailing edge modification) is also studied. The centerline pressure decay results at nozzle pressure ratios 2, 3, 4 and 5 confirm the superiority of modified jet (jet from trailing edge modified nozzle) over plain jet from the mixing point of view. At all the pressure ratios, the modified jet possessed shorter core and weaker shock and expansion waves compared to plain jet, which is an outcome of faster mixing of modified jet with ambient fluid. The enhanced mixing caused the modified jet to decay faster than the plain jet. An appreciable core length reduction of about 32% is noticed at pressure ratio of 5. The modified jet experienced increased spread along major axis than along minor axis owing to the restriction offered by the triangular extension on jet spread along minor axis. Thus, the axis switching was absent in modified jet compared to plain jet switching axes at all pressure ratios. The shadowgraph images confirmed the presence of weaker waves in the modified jet. Also, the images confirmed the absence of Mach disk in the modified jet at pressure ratio of 5 compared to plain jet.

The catchment area of groomed jets at NNLL

Groomed jet observables have a dynamical catchment area which plays a key role in determining the leading nonperturbative power corrections and the impact of the underlying event. Based on field-theoretic arguments, certain moments of the groomed jet radius Rg capture the entirety of the kinematic and grooming parameter dependence of these effects. These moments can be computed perturbatively in the soft drop operator expansion region where these corrections are small, but yet significant to be relevant for precision physics. A precise determination of these moments is thus crucial to faithfully isolate the universal contributions of hadronization and the underlying event. Building on a previously developed effective field theory framework for the doubly differential soft drop groomed jet mass and groomed jet radius measurement, we present here a calculation of these moments at next-to-next-to-leading-logarithmic (NNLL) accuracy including matching into the plain jet mass region. We compare our predictions for these moments against parton-shower Monte Carlo simulations and find good agreement. These results have applications for precision physics with soft drop jet mass such as determination of the strong coupling constant and the top quark mass and for improving hadronization models.

Experimental Study on the Effect of Tabs with Asymmetric Projections on the Mixing Characteristics of Subsonic Jets

This study experimentally explores the effect of tabs with asymmetric projections on the mixing effectiveness of jets at different nozzle exit Mach numbers with subsonic ranges of 0.4, 0.6, and 0.8. The results obtained with the tab-controlled jet are compared with those of uncontrolled jets. In this experimental investigation, a pair of identical tabs is deployed along a diameter of a convergent nozzle with inlet and exit cross sections of a circle, where each tab has two triangular projections configured at locations offset to each other at a distance of 1 mm on a plain rectangular stem. The geometrical blockage due to the presence of both tabs is maintained at 5.09% to minimize the thrust loss incurred due to tabs. The counter-rotating vortices generated at different locations of the tabs, caused instability or shear distortions at the nozzle exit, promoting jet mixing and eventually leading to rapid velocity decay along the jet axis and accentuating the reduction of the potential core. Compared to plain jet, reductions in core length of about 70%, 76%, and 81% at Mach 0.4, 0.6, and 0.8, respectively, are observed with the tab-controlled jets. The total pressure decay characteristics in the radial profile along the tab and normal-to-tab orientations have shown significant distortion in the jet structure, making it asymmetrical again owing to the asymmetrical positioning of projections on the tabs. Besides, in comparison with the plain nozzle, the total pressure decay characteristics in the radial profiles of tab-controlled jets are significantly different along the axial locations in the downstream direction due to the same reason of the asymmetrical positioning of triangular projections on the tabs. The primary research goal of this experimental investigation with asymmetrical tabs is to promote jet mixing asymmetrically to achieve thrust vectoring of jets.

Search for jet quenching effects on the plain jet mass in Pb+Pb collisions at the LHC with a multiphase transport model

The plain jet mass distributions of reconstructed jets are investigated in p+p and 0–10 $$\%$$ most central Pb+Pb collisions at $$\sqrt{s_{\textrm{NN}}} = 2.76~\textrm{TeV}$$ using a dynamical multiphase transport model with a string melting mechanism. It is observed that the mean charged jet mass increases with increasing jet transverse momentum and jet radius in central Pb+Pb collisions. It is demonstrated that the plain jet mass of reconstructed partonic jet is shifted to a higher value after the evolution of partonic stage due to jet quenching in central Pb+Pb collisions. However, the jet mass shift effect is strongly weakened by non-perturbative effects from hadronization and hadronic rescatterings. This makes it difficult to observe significant hot medium modification effects on the plain jet mass distribution in the final state of relativistic heavy-ion collisions.

Recent Progress in Flow Control and Heat Transfer Enhancement of Impinging Sweeping Jets Using Double Feedback Fluidic Oscillators: A Review

Abstract Jet impingement finds an important role in several industrial applications which require high thermal-hydraulic performance of heat exchange systems. The self-exciting sweeping jets produced by fluidic oscillators provide superior thermal and hydraulic performance as compared to plain jets. The fluidic oscillator increases the jet impingement area on the target surface by maintaining a steady and controlled oscillatory flow. The continuous advancements in the design improvement of fluidic oscillators have led to further enhancements of heat and fluid flow characteristics. In this context, double feedback fluidic oscillators have shown promising jet flow control features and jet impingement cooling characteristics. Therefore, the current study has been devoted to analyzing and assessing the recent research progress in design improvements of double feedback fluid oscillators and the augmentation of thermal-hydraulic characteristics of impinging sweeping. Moreover, the variations in the heat transfer and hydraulic performance of impinging jets for different shapes of target surfaces have been comprehensively examined. In the end, research gaps for future work have been highlighted.

Study on atomization performance of multi-orifice air-assisted plain jet atomizers

In this study, the atomization characteristics of several multi-orifice air-assisted plain jet atomizers are investigated. By multiple experimental ways, fuel flow distribution, spray angle and the Sauter mean diameter (SMD) distribution are obtained. Several simulation works are also conducted, showing the internal flow field of the atomizer that can explain the experimental results. The results proved the efficiency of the atomizers, the SMD can be as low as 40 µm and a 25*15 mm well-atomized zone is found on each side of the atomizer. Increasing the inlet air velocity will widen the spray, causing the spray angle to increase from 36.1° for V = 40 m/s to 46.6° for V = 70 m/s. Meanwhile the droplets' diameter are decreased, the SMD range at line Y = 5 mm decreased from 55 to 80 µm to 33–55 µm downstream one of the tested atomizers. The structural parameter influences the spray characteristics by altering the atomizers' internal flow field. The air–fuel mixture tends to concentrate at the rear part of the distributing pipe for larger orifices, causing the peak point of the fuel flux curve to change from X = 39 mm for 2 mm orifice diameter to X = 43.3 mm for 4 mm orifice diameter. These studies will establish an overall view of the atomizers' atomization performance and lay the foundation for the further application of multi-orifice atomizers.

Baffle jetting: CFD analysis of plain jets impinging on fuel rods

The risk of baffle jetting exists mainly in pressurized water reactors, which are designed with a counter flow configuration in the core bypass region. Baffle plates are foreseen between core barrel and core, providing the core's lateral restraint and allowing a core bypass flow. A pressure differential establishes between the coolant flow in the core baffle and the upward flow through the core. A part of the coolant bypass flow is directed through the gaps of the baffle plates towards the core. Coolant cross flow through enlarged baffle gaps can result in high velocity jetting in the case of significant pressure differences between core and baffle region. These water jets impact onto the fuel rods and may induce rod vibration that can lead to fuel rod failure.Modelling baffle jetting induced vibrations of fuel rods is still a challenge in the field of fluid structure interaction. The present work aims to extend the understanding of the unsteady flow in rod bundles to situations where baffle jetting occurs. As a first step, the used LES modelling method is evaluated on the example of a well documented test case related to fuel rods in cross flow: the flow over a circular cylinder at Re = 3900. In the successive step, the validated modelling method is applied to the CEA PANACHET experiment, mimicking baffle jetting related phenomena. This analysis helped to understand better the flow field of a corner baffle jet and further validated the modelling approach.The flow field in the core baffle corner is finally analysed for realistic reactor conditions. A plain narrow slot jet is injected parallel to a baffle wall through a 1 mm width gap perpendicular to the axial flow of a corner assembly. The analysis of the flow field showed that: (i) Swirling flow exist close to the corner rod. The calculated force coefficients lift and drag of this rod show a dominant fluctuation frequency of about 80 Hz. (ii) The baffle jet impacts on the third rod in jet direction (passing the first two rods without impact). The force coefficients of the third rod do not show a dominant oscillation frequency but show increased oscillation amplitudes. The distinguished fluctuation frequency detected for rod n°1 and the direct impact of the baffle jet on rod n°3 might explain the rod failures that have been detected for these rods.

On the flow physics and vortex behavior of rectangular orifice synthetic jets

Synthetic jet actuators possess a continuous jet like behavior in its far region and have found wide-scale engineering applications since it allows momentum transport to the flow system without any net mass transfer across the flow boundaries. The case of a non-axisymmetric synthetic jet is particularly significant since it is affected by the differential shear layer at the orifice exit, that depends on its aspect ratio. However, despite exhaustive research on both continuous and synthetic jets, very few studies have experimentally investigated the case of rectangular orifice synthetic jets, focusing on the effect of aspect ratio of the orifice as well as the actuation frequency upon the vortex behavior and the flow physics. In particular, the intriguing phenomenon of vortex bifurcation has mostly been reported only for an individual vortex or for a plain jet. Yet, in a train of vortex rings, such as that obtained in a synthetic jet, the occurrence of vortex bifurcation can be expected, although the flow physics in the wake of individual vortex rings is significantly different. The present study experimentally investigates a rectangular orifice synthetic jet at different orifice aspect ratios and actuation frequencies, focusing on exploring the conditions at which vortex bifurcation occurs, through LIF imaging and Hot-film measurements. The primary objective of these experiments is to provide a qualitative physical insight into the synthetic jet ejected from a rectangular orifice (through LIF imaging), as well as to quantitatively explore the experimental conditions that promote different flow structures (through velocity time trace, time-averaged velocity profiles and power spectral density measurements), particularly the bifurcation of vortex rings. Our experiments indicate that the phenomenon of vortex bifurcation is observed during the axial switching of vortex rings, but only in a narrow range of experimental conditions. Further, the velocity measurements have ascertained that the two prominent reasons behind this bifurcation process are a large disparity in the velocities of the vortex core and the center of vortex ring, as well as the time lag in which the separation distance between the counter-rotating vortices decrease gradually to zero.

Effect of Quarls on the Blowout Stability and Emission of Pollutants of a Liquid-Fueled Swirl Burner

Stringent emissions standards for NOx and carbon monoxide (CO) prompt lean combustor development. With this motivation, combustion stability issues emerge since the desired operating point approaches the lean blowout limit. In this paper, an atmospheric, 15 kW lean premixed prevaporizing-type swirl burner, equipped with a plain jet airblast atomizer, was investigated at various atomizing pressures and combustion air flow rates, using quarls from 0 deg to 60 deg in 15 deg steps. Both the 15 deg and the 30 deg quarls provided a 42% higher lean blowout stability on average in terms of mean mixing tube discharge velocity, compared to the baseline burner. However, the superior stability regime was encumbered by a rapidly increasing CO emission. In parallel, the NOx emission vanished due to the more dilution air and incomplete combustion. The 60 deg quarl provided a moderately extended blowout stability limitation, while the NOx emission slightly increased and the CO emission reduced compared to the baseline burner.

Flame emission spectroscopy measurement of a steam blast and air blast burner

Control and online monitoring of combustion have become critical to meet the increasingly strict pollutant emission standards. For such a purpose, optical sensing methods, like flame emission spectrometry, seem to be the most feasible technique. Spectrometry is capable to provide information about the local equivalence ratio inside the flame through the chemiluminescence intensity ratio measurement of various radicals. In the present study, a 15 kW atmospheric burner was analyzed utilizing standard diesel fuel. Its plain jet type atomizer was operated with both air and steam atomizing mediums. Up to now, injection of steam into the reaction zone has attracted less scientific attention contrary to its practical importance. Spatial plots of OH*, CH*, and C2* excited radicals were analyzed at 0.35, 0.7, and 1 bar atomization gauge pressures, utilizing both atomizing mediums. The C2* was found to decrease strongly with increasing steam addition. The OH*/CH* and OH*/C2* chemiluminescence intensity ratios along the axis showed a divergent behavior in all the analyzed cases. Nevertheless, CH*/C2* chemiluminescence intensity ratio decreased only slightly, showing low sensitivity to the position of the spectrometer. The findings may be directly applied in steady operating combustion systems, i. e., gas turbines, boilers, and furnaces.

INJECTION OF WATER-IN-OIL EMULSION JETS INTO A SUBSONIC CROSSFLOW: AN EXPERIMENTAL STUDY

Atomization and Sprays, 24 (4): 303–348 (2014) INJECTION OF WATER-IN-OIL EMULSION JETS INTO A SUBSONIC CROSSFLOW: AN EXPERIMENTAL STUDY Chris D. Bolszo, Vincent G. McDonell, ∗ Guillermo A. Gomez, & G. Scott Samuelsen Department of Mechanical and Aerospace Engineering, University of California, Irvine, California 92697-3550, USA Address all correspondence to Vincent G. McDonell E-mail: mcdonell@ucicl.uci.edu Original Manuscript Submitted: 8/6/2013; Final Draft Received: 11/13/2013 In this work, the influence of introducing water in oil, as an emulsion, in a liquid jet injected into a gaseous crossflow is investigated. Of particular interest is the relationship between emulsion charac- teristics on spray penetration and spray droplet size. Tests are conducted at atmospheric conditions, with liquid jet-to-crossflow momentum flux ratios spanning 30–120, and water addition to 40% by mass. Gas velocities range from 20 to 80 m/s and liquid velocities from 10–20 m/s are considered. Backlit high-speed video is used to document the overall spray characteristics and laser diffraction is used to measure the spray droplet sizes. Sobel edge filtering and intensity thresholding are utilized to establish the spray plume upper edge for the spray morphology, which was used to establish the spray trajectory. The Buckingham π theorem is used to identify the important functional groupings for the current physical problem. For time-averaged trajectories, an existing liquid jet trajectory equation form from Wu and co-workers successfully correlates the penetration of emulsion spray plumes. These findings show that momentum flux of the bulk emulsion jet remains the dominant factor governing jet penetration. The influence of emulsification on spray plume droplet size distributions is quanti- fied in the current work. A new nondimensional quantity is proposed to account for the effect of body forces and repulsive interfacial tension on correlating breakup. For the conditions studied, an addi- tional primary breakup mode for emulsions, interfacial tension breakup, is identified and observed to influence spray plume development and droplet size. KEY WORDS: jet in crossflow, jet penetration, droplet size, interfacial tension, laser diffraction spectroscopy, high-speed cinematography, Buckingham π theorem 1. INTRODUCTION In many applications, liquid atomization is achieved by injecting a column of liquid as a plain jet, perpendicularly (or angles near to) into a gaseous flow. This strategy has been utilized for various combustion systems including rocket propulsion, turbofan, turbojet, c 2014 by Begell House, Inc.

Cobertura de gotas de pulverização obtida com diferentes pontas e taxas de aplicação na parte aérea da cana-de-açúcar

A aplicação de produtos fitosssanitários no setor sucroalcoleiro, até recentemente, estava focada principalmente no controle de plantas daninhas. Com o aparecimento da ferrugem alaranjada, como doença de importância agrícola na cultura da cana-de-açúcar, passou a ser imperioso conhecer como a aplicação chega na parte aérea da planta. Dessa forma, o presente estudo foi desenvolvido com o objetivo de avaliar a qualidade da deposição da calda em pulverização terrestre, conduzido em esquema fatorial 2x2x2 (duas pontas de pulverização, duas taxas de aplicação e duas posições dos cartões de papéis hidrosensíveis no dossel da planta), seis repetições, com dez papéis cada. Foram utilizadas as pontas de pulverizacão XR110.02 (jato plano de uso ampliado) e TTJ60 - 110.02 (jato plano duplo, com ângulo de 60 graus entre si) utilizando-se as taxas de aplicação de 120 e 160L ha-1. Os cartões de papel hidrossensível utilizados para avaliar a deposicão das pulverizações foram distribuidos sobre as folhas de cana-de-açúcar, em duas posições distintas em relação ao dossel da planta (parte superior e inferior, aproximadamente, 0,80 e 0,50 metros do solo, dispostos na horizontal e inclinado em relação à superfície do solo, respectivamente). A cultivar utilizada foi 'RB 96-6928', com altura de 0,80m aos 120 dias do plantio. Um scaner de mesa foi utilizado para digitalizar as imagens dos papéis e avaliou-se as coberturas através do programa Conta-Gotas®. Os dados de deposição/cobertura foram submetidos à análise de variância e as médias comparadas pelo teste Tukey ao nível de 5% de probabilidade de erro. No dossel superior da cana-de-açúcar observou-se maior cobertura, quando comparado ao dossel inferior, sendo que não se observaram diferenças entre as taxas de aplicação de 120 e 160L ha-1,. A ponta TTJ60-110.02 promoveu cobertura superior à ponta XR 110.02 quando se utilizou 160L ha-1 (40,34 e 36,50%, respectivamente).

Experimental studies on rectangular jets with trapezoidal tabs

AbstractAn experimental investigation was carried out to study the flow development of a jet issuing from a 2:1 rectangular nozzle with mixing tabs using two-component hotwire anemometry. A pair of tabs of trapezoidal configuration (with 2% total blockage area) is placed on the minor-axis side of the rectangular nozzle and tested for two tab inclination angles of 135° and 45°, with respect to the flow direction. Tests were conducted for a nominal jet exit velocity of 20m/sec corresponding to a Reynolds number based on nozzle equivalent diameter of 5·013 × 104. Relative to the plain jet, the jet with tabs show significant reduction in jet-core length (by 67%) followed by a faster decay in jet centreline velocity (U/Ue). This is also accompanied by a significant upstream shift in peak centreline turbulence intensity (u’/Ue). The presence of tabs is observed to inhibit the jet growth along the minor-axis plane thereby introducing large distortion in the jet cross-sectional development that ultimately leads to jet-core bifurcation along its major-axis. While a mushroom-like flow structure develops behind the tab with 135° inclination, the flow structure behind a 45° inclined tab rather takes the shape of the tab itself. The former flow development is seen to enhance the jet growth more along the minor-axis while the latter improves the jet growth more along the major-axis plane. From application point of view, since both tab inclinations result in more or less similar jet characteristics, a 135° inclined tab would be preferable over a 45° inclined tab from the view of improved jet mixing.

Experimental Study on Lifted Flames Operated with Liquid Kerosene at Elevated Pressure and Stabilized by Outer Recirculation

This study deals with the impact of the operating conditions, e.g. pressure, preheating temperature, pressure drop across the nozzle, nozzle size and stoichiometry, on the reaction zone location and spray evaporation progress in case of a lifted flame. Lifted flames are highly valued for their NOx reduction potential and for their low susceptibility to flash-back and thermo-acoustic instabilities. These advantageous features arise from the improved homogeneity of the fuel-air mixture provided to the reaction zone. One distinctive feature of the lifted flames is the presence of the so called lift-off zone located between nozzle outlet and main reaction zone. Within the lift-off zone fuel and oxidizer remain a certain time in contact and mix together prior to the onset of the combustion reaction. This leads to a more uniform heat release distribution and lowers the nitrogen oxides emissions at lean conditions by reducing the temperature spikes. In contrast to many other studies the subject of investigation was not a plain jet flame, but a modified version of the airblast nozzle, widely used in industrial applications. The nozzle was operated with liquid kerosene. As liquid fuels are easier to handle than gaseous or solid, it is expected that many efforts in the future will focus on the development of liquid fuels surrogates. Our previous investigations have shown, that the nozzle is well suited to be operated with gaseous fuels as well (Fokaides et al, J Eng Gas Turbine Power 130, 011508 2008). The position of the reaction zone was determined by means of chemiluminescence of the OH∗ radicals and from its location the lift-off height was derived. In addition the fuel evaporation progress was measured by means of light scattering, revealing that fuel droplets and main reaction zone are well separated. It was found that the operating conditions have a versatile impact on the length of the lift-off zone and spray cone and thus on the degree of pre-evaporation and premixing. Thus, it may be concluded, that through a proper choice of operating conditions and combustor size a desired lift-off height can be adjusted in accordance with criteria, like available space, required emission levels etc.

Analysis of the 3D zone of flow establishment from a ship’s propeller

In the present study an experimental investigation of the time-averaged velocity and turbulence intensity distributions from a ship’s propeller, in “bollard pull” condition (zero speed of advance), is reported. Previous studies have focused mainly on the velocity profile of not a rotating ship propeller but a plain jet. The velocity profile of a propeller is investigated experimentally in this study. The velocity measurements were performed in laboratory by using a Laser Doppler Anemometry (LDA). The measurements demonstrated two-peaked ridges velocity profile with a low velocity core at the centre within the near wake. The two-peaked ridges combined to be one-peaked ridge at 3.68 diameters downstream indicating the end of the zone of flow establishment. The study provides useful information from a rotating ship’s propeller rather than a simplified plain jet to researchers investigating flow velocity generated from a propeller and probably resulting local scouring.

Effect of Tab Geometry on the Development of a Jet Issuing from a Rectangular Nozzle

An experimental investigation was carried out to study the effect of tab geometry on the flow characteristics of a jet issuing from a 2:1 rectangular nozzle using two-component hotwire anemometry. A pair of tabs of trapezoidal and square configurations (2% total blockage area) is placed on the minor-axis side of the rectangular nozzle and tested for two tab inclination angles of 135° and 45°, respectively. Tests were conducted for a nominal jet exit velocity of 20 ms-1 corresponding to a Reynolds number based on nozzle equivalent diameter of 5.02×104. Relative to the plain jet, the potential-core length of the jet with trapezoidal tabs shows a reduction of 62% while the jet with square tabs shows a reduction of 75%, respectively. This is also accompanied by a significant upstream shift in peak centerline turbulence intensity (u'/Ue). The tab inclination of 135° results in further enhanced jet characteristics in each case. The presence of each tab configuration is observed to inhibit the jet growth along the minor-axis plane thereby introducing large distortion in the jet cross-sectional development that ultimately leads to jet-core bifurcation along its major-axis. However, it is observed that while the jet with trapezoidal tabs switches its axis at some downstream location, the jet with square tabs does not switch axis at all. This indicates a strong influence of tab geometry on the overall jet flow development.

Study of jets from rectangular nozzles with square grooves

AbstractAn experimental study has been carried out to understand jet flow development from plain and grooved rectangular nozzles of aspect ratio 2:1 using two-component hotwire anemometry. Grooves of square configuration (side 4mm) and length 5mm were introduced in the (i) minor-axis, (ii) major-axis and, (iii) in both minor- and major-axes directions. The equivalent diameter of the plain rectangular nozzle is 37·5mm. Studies were carried out for a nominal jet exit velocity of 20ms−1 and for Reynolds number based on equivalent diameter of 54,000. The introduction of grooves in either plane does not show any influence on the potential-core length but results in faster jet-decay thereafter. It is observed that the grooves when introduced in minor-axis direction inhibit the jet growth in that plane while promoting the jet growth along major-axis plane and hence, delays the phenomena of axis-switching. However when introduced in major-axis direction, the grooves promote jet growth along major-axis plane while inhibiting jet-growth in minor-axis plane. Cross-sectional contours of mean-velocity suggest that the grooves modify the process of overall jet development significantly in the plane in which they are introduced relative to the plain jet and hence, significantly affect the axis-switching location in each case.

1116 マイクロバブルを含む噴射液体のノズル内キャビテーションと微粒化の挙動(エンジンシステムII)

1116 マイクロバブルを含む噴射液体のノズル内キャビテーションと微粒化の挙動(エンジンシステムII)

Role of hydrodynamics in supercritical antisolvent processes

An experimental study of hydrodynamics role in the supercritical antisolvent (SAS) process is here presented. Jet dispersion and atomization of a liquid phase into a dense one have been characterized for miscible systems and for commonly used conditions in SAS processes. The critical atomization jet velocity tends to the same value for all the systems studied. The dispersion has also been studied in the case of an organic solution containing the solute to be precipitated. The presence of sulfathiazole in a concentration up to 10 wt% does not influence the liquid jet dispersion. The nucleation zone has been located: crystals are not formed in the plain jet but in the entities resulting from the jet break-up. The observation of the crystals formed shows that the key-point is the mixing state more than the atomization state to form fine particles. However, atomization conditions lead to more homogeneous powder characteristics.

The Effect of Liquid-Fuel Preparation on Gas Turbine Emissions

The emissions of liquid-fuel fired gas turbine engines are strongly affected by the fuel preparation process that includes atomization, evaporation, and mixing. In the present paper, the effects of fuel atomization and evaporation on emissions from an industrial gas turbine engine were investigated. In the engine studied, the fuel injector consists of a coaxial plain jet airblast atomizer and a premixer which consists of a cylindrical tube with four mixing holes and swirler slits. The goal of this device is to establish a fully vaporized, homogeneous fuel/air mixture for introduction into the combustion chamber and the reaction zone. In the present study, experiments were conducted at atmospheric pressure and room temperature as well as at actual engine conditions (0.34MPa, 740K) both with and without the premixer. Measurements included visualization, droplet size, and velocity. By conducting tests with and without the premixing section, the effect of the mixing holes and swirler slit design on atomization and evaporation was isolated. The results were also compared with engine data and the relationship between premixer performance and emissions was evaluated. By comparing the results of tests over a range of pressures, the viability of two scaling methods was evaluated with the conclusion that spray angle correlates with fuel to atomizing air momentum ratio. For the injector studied, however, the conditions resulting in superior atomization and vaporization did not translate into superior emissions performance. This suggests that, while atomization and the evaporation of the fuel are important in the fuel preparation process, they are of secondary importance to the fuel/air mixing prior to, and in the early stages of the reaction in, governing emissions.