Begell House Inc.
Atomization and Sprays
AAS
1044-5110
27
7
2017
A STUDY ON DISCHARGE COEFFICIENTS OF CLOSED-TYPE SWIRL INJECTORS FOR A LIQUID ROCKET ENGINE
569-578
10.1615/AtomizSpr.2017019096
Kyubok
Ahn
School of Mechanical Engineering, Chungbuk National University, Chungbuk, Korea
Hwan-Seok
Choi
Combustion Chamber Department, Korea Aerospace Research Institute, Daejeon, Korea
closed-type swirl injector
discharge coefficient
swirl injector geometric constant
liquid rocket engine
An experimental and comparative study on the discharge coefficients of closed-type swirl injectors, which have a swirl chamber diameter larger than the nozzle diameter, has been performed. With a range of geometric dimensions and
therefore broad swirl injector geometric constants, 27 closed-type swirl injectors were designed and manufactured. Hydraulic cold-flow tests were conducted using tap water to measure the discharge coefficients, with pressure differentials through the injectors ranging from approximately 8 to 12 bar. The discharge coefficients obtained from the cold-flow tests were confirmed to follow a functional relationship to the swirl injector geometric constant. A novel simple empirical equation, which would be useful in the design of new closed-type swirl injectors for liquid rocket engines, is suggested. The present experimental results were compared with previous empirical equations to investigate their accuracy. It was found that most equations predicted well the measured discharge coefficients only in a narrow range of swirl injector geometric constants; on the contrary, an equation suggested by Russian researchers could anticipate those with great accuracy in a whole range of present swirl injector geometric constants.
GEOMETRIC EFFECT ON SPRAY CHARACTERISTICS OF GAS-CENTERED SWIRL COAXIAL INJECTORS: RECESS RATIO AND GAP THICKNESS
579-589
10.1615/AtomizSpr.2017018958
Gujoeng
Park
Department of Mechanical and Aerospace Engineering, Seoul National University, Seoul,
08826, Republic of Korea
Jungho
Lee
Engine Test and Evaluation Team, Korea Aerospace Research Institute, Daejeon, 34133,
Republic of Korea
Ingyu
Lee
KF-X Propulsion System Team, Korea Aerospace Industries, Ltd., Sacheon, 52529, Republic of
Korea
Youngbin
Yoon
Department of Mechanical and Aerospace Engineering, Seoul National University, Seoul,
08826, Republic of Korea
Chae Hoon
Sohn
Department of Mechanical Engineering, Sejong University, Seoul, 05006, Republic of Korea
GCSC injector
single swirl injector
momentum flux ratio
spray characteristics
recess length
gap thickness
film thickness
spray angle
The characteristics of gas-centered swirl coaxial (GCSC) injectors used in a staged-combustion cycle of Russian liquid-rocket engines were investigated. This study determined how the spray characteristics of GCSC injectors are influenced by the momentum flux ratio, gap thickness, and recess length used as important coaxial injector parameters. The film thickness and spray angle were measured by the electrical conductance and backlight image methods, respectively. The liquid film thickness and spray angle were changed according to the spray condition. The spray characteristics at low liquid pressure drop were sensitive to gas but not at high liquid pressure drop. The momentum flux ratio showed a better relationship with spray characteristics than the spray condition of liquid and gas, respectively. As the momentum flux ratio increased, the spray characteristics tended to decrease overall and this tendency occurred at a lower momentum flux ratio as the recess ratio increased. Also, the spray characteristics varied with the gap thickness. The liquid film thickness and spray angle were relatively low in small gaps, and were similar as the gap thickness increased.
ARTIFICIAL CONTROL OF SPRAY DYNAMICS APPLYING FUEL DESIGN APPROACH RELATED TO FLASH BOILING
591-610
10.1615/AtomizSpr.2017017967
Jiro
Senda
Department of Mechanical Engineering, Doshisha University, Kyoto, Japan
Eriko
Matsumura
Department of Mechanical Engineering, Doshisha University, Kyoto, Japan
flash boiling
mixed multicomponent fuel
spray atomization
evaporation process
spray dispersion
fuel design
combustion control
The authors have proposed a novel approach regarding fuel design methodology targeting both diesel and gasoline
engines and demonstrated that the fuels designed based on this approach were effective in achieving high thermal
efficiency and low pollutant emissions. Flash boiling spray is applied to improve the spray atomization and evaporation
processes by using several kinds of mixed fuels with relatively low injection pressure. This paper is a review concerning our previous research and new experimental results of superheated mixed diesel-like spray, focusing on spray dynamics. In the mixed fuels, additives or lower boiling point fuels such as CO2, gas fuel, and gasoline component, are mixed into a higher boiling point fuel such as diesel gas oil, through vapor-liquid equilibrium with a formation of a two-phase region in a pressure-temperature diagram, where liquid and vapor phases of both components are mixed in. In this scheme, the authors intend to control both the physical process, that is, the fuel vapor formation rate or spatial vapor distribution, and chemical processes, which are the mixture ignition, emission reduction of NOx and PM, and HC burnout. Then it is easy for mixed fuel to readily undergo flash boiling spray due to the formation of a two-phase region on a P-T diagram, providing as well as a relatively lean and homogeneous vapor mixture. In the experiments, the authors conducted mixed fuel application studies for the actual diesel combustion field by use of mixed fuel consisting of liquefied CO2 as an additive with n-tridecane as a typical component of diesel gas oil, and mixed fuel of gas or gasoline component with a diesel gas oil component to control the evaporation process. Furthermore, experiments of mixed fuel heating were conducted to realize the prompt evaporating spray due to a partial flashing effect and a supercritical diesel-like spray feature.
EXPERIMENTAL INVESTIGATION ON FUEL FILM FORMATION BY SPRAY IMPINGEMENT ON FLAT WALLS WITH DIFFERENT SURFACE ROUGHNESS
611-628
10.1615/AtomizSpr.2017019706
Hongliang
Luo
State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou, 310027, PR China; Department of Mechanical Systems Engineering, Graduate School of Advanced Science and Engineering, University of Hiroshima 1-4-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8527, Japan; School of Mechatronics Engineering, Foshan University, Foshan, 528225, PR China
Shintaro
Uchitomi
Department of Mechanical System Engineering, University of Hiroshima, 1-4-1 Kagamiyama,
Higashi-Hiroshima, Hiroshima 739-8527, Japan
Keiya
Nishida
Department of Mechanical System Engineering, University of Hiroshima, 1-4-1
Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8527, Japan
Youichi
Ogata
Graduate School of Advanced Science and Engineering, University of
Hiroshima, 1-4-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8527, Japan
Wu
Zhang
Mazda Motor Corporation, 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima 730-8670, Japan
Tatsuya
Fujikawa
Mazda Motor Corporation, 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima 730-8670, Japan
fuel spray
direct-injection spark-ignition engine
fuel film characteristics
wall impingement
Mie scattering method
refractive index matching method
The impingement of fuel sprays on the wall in direct-injection spark-ignition (DISI) engines affects mixture preparation, combustion performance, and pollutant emissions. A better understanding of the fuel film behaviors is required to reduce exhaust emissions and fuel consumption. In this work, the experimental results of fuel spray impinging behaviors and adhered fuel film formation were measured by Mie scattering and refractive index matching (RIM) methods. The spray tip penetration and impinging spray height were discussed; the mass, area, and thickness of the fuel film were investigated under different conditions, including wall surface roughness, injection pressure, and ambient pressure. The results show that an increase in the wall roughness decreases the spray tip penetration, increases the impinging spray height, and decreases the uniformity of the fuel film distribution. An increase in ambient pressure results in a more uniform distribution of the fuel film.
PARTICLE AND DROPLET CLUSTERING IN OSCILLATORY VORTICAL FLOWS
629-643
10.1615/AtomizSpr.2017019152
Yuval
Dagan
Faculty of Aerospace Engineering, Technion—Israel Institute of Technology,
Haifa, 3200003, Israel
David
Katoshevski
Environmental Engineering Unit, Ben-Gurion University of the Negev, P.O. Box 653,
Beer-Sheva 84105, Israel
J. Barry
Greenberg
Aerospace Engineering, Technion, Israel Institute of Technology (IIT), Haifa 32000,
Israel
spray dynamics
droplet clustering
vortex flows
A new mathematical analysis of particle and droplet clustering in a fluctuating vortex flow is presented. Two-dimensional particle and droplet dynamics equations are solved numerically and analytically, assuming an oscillating
vortex flow field. Droplet grouping was found to occur in the vicinity of an oscillating vortex and new streak-like
grouping patterns of droplets in a vortex are disclosed. The combination of circumferential and radial fluctuations
produces the most significant effects on the droplet grouping, facilitating the construction and destruction of the streak patterns, depending on the chosen flow field and droplet properties. A new analytical formulation is derived using perturbation analyses to model the swirl fluctuations on the spray, providing a simple method to evaluate the effect of droplet dispersion and droplet clustering under fluctuating vortex flows. This approach was found to be in good agreement with the numerical results in cases of low Stokes numbers for both evaporating and nonevaporating droplets. It is shown that evaporation tends to increase the droplet fluctuation amplitude with time and therefore intensifies the grouping effect. The combination of oscillation and evaporation was found to have the most significant effect on droplet grouping, where the amplitude of the proximity curve rapidly increases in a nonlinear manner. Despite the simplicity of the current model its predictions provide insight into the driving mechanisms behind the much more complex turbulent spray-combustion regime, in which similar droplet grouping patterns occur.
NUMERICAL STUDY OF ELECTRIC REYNOLDS NUMBER ON ELECTROHYDRODYNAMIC (EHD) ASSISTED ATOMIZATION
645-664
10.1615/AtomizSpr.2017016576
Patrick
Sheehy
Department of Mechanical & Industrial Engineering, Montana State University, P.O. Box
173800, Bozeman, Montana 59717-3800, USA
Mark
Owkes
Department of Mechanical and Industrial Engineering, Montana State
University, Bozeman, MT, 59717-3800, USA
NGA
CFD
fluid breakup
charge mobility
volume of fluid
electrospray
charge injection
multiphase flow
self-propagating electric field
Electrohydrodynamic assisted atomization (EHD) injects electrical charges into liquid within the injector nozzle, creating an electrically charged atomizing liquid. For many relevant engineering flows, including liquid fuel injection, the charge mobility time scale (time it takes the charges to relax to the fluid-gas boundary) is similar in magnitude to the charge convection time scale (relevant flow time), which leads to a nontrivial electric charge distribution. This distribution within the liquid fuel may enhance atomization, the extent to which is dependent on the ratio of the previous time scales which are known as the electric Reynolds number (Ree). In this work, a computational approach for simulating two-phase EHD flows is used to investigate how Ree influences the resulting atomization quality. The computational approach is second order, conservative, and used to consistently transport the phase interface along with the discontinuous electric charge density and momentum. The scheme sharply handles the discontinuous electric charge density, allowing robust and accurate simulations of electric charge relaxation. Using this method, multiple three-dimensional simulations are performed with varying Ree values which highlight the effect of Ree on the atomization efficiency of a liquid jet. Comparison of these cases shows the importance of Ree on atomization and suggests that decreasing Ree (increasing charge mobility) leads to larger electric charge densities, increased Coulomb forces, and ultimately improved breakup during the atomization process.