Begell House Inc.
Atomization and Sprays
AAS
1044-5110
28
5
2018
INFLUENCES OF BOUNDED AND COMPRESSIBLE GAS MEDIUM ON THE INSTABILITY OF AN ANNULAR POWER-LAW LIQUID JET
389-402
10.1615/AtomizSpr.2018021426
Yi-bo
Wang
State Key Laboratory of Engines, Tianjin University, Tianjin, 300072, China
Jin-Peng
Guo
State Key Laboratory of Engines, Tianjin University, Tianjin, 300072, China
Fu-Qiang
Bai
State Key Laboratory of Engines, Tianjin University, Tianjin, 300072, China; Internal Combustion Engine Research Institute, Tianjin University, Tianjin, 300072, China
Qing
Du
State Key Laboratory of Engines, Tianjin University, Tianjin, 300072, China
instability and breakup
compressible gas medium
power-law fluids
annular liquid jets
Based on the linear approximation of liquid constitutive equation, this paper investigated the instability and breakup of an annular power-law liquid jet into bounded and compressible gas medium, with both para-sinuous mode and para-various mode disturbances. The influences of gas−liquid velocity difference, Mach number, outer gas confinement, and gas−liquid density ratio were studied in detail. Numerical results show that with the increase of gas−liquid velocity difference, the jet instability
is gradually dominated by the Kelvin−Helmholtz wave. The annular jet of power-law fluids in the bounded gas stream is more unstable than that in the open gas medium. As the gas velocity increases, the gas confinement has less impact on the jet instability. The gas compressibility can effectively
destabilize the annular jet of power-law fluids and decrease the breakup scale. In low-speed gas stream, the jet breakup is mainly dominated by the para-sinuous mode. With the increase of the gas density and velocity as well as the Mach number, the para-varicose mode also exerts a significant effect on the breakup of power-law liquid jets. Especially in the cases of large Mach number and high gas velocity, either disturbance mode has the potential to dominate the breakup of power-law liquid jets.
ATOMIZATION OF HIGH-VISCOSITY AND NON-NEWTONIAN FLUIDS BY PREMIXING
403-416
10.1615/AtomizSpr.v28.i5.20
Tom
Baker
Laboratory of Technical Physics, School of Engineering, University of Liverpool, Liverpool, L69 3GH, United Kingdom; DLR − German Aerospace Center, Institute of Space Propulsion, Lampoldshausen, Langer Grund, 74239 Hardthausen, Germany
Michele
Negri
DLR, German Aerospace Center, Institute of Space Propulsion, Lampoldshausen,
Langer Grund, 74239 Hardthausen, Germany
Volfango
Bertola
Laboratory of Technical Physics, University of Liverpool, Liverpool, United
Kingdom, L69 3GH
atomization device
spray generator
viscoplastic gel
high-viscosity fluids
A novel concept of spray generator is described, which combines aerodynamic and mechanical liquid breakup to achieve liquid atomization. In particular, the concept of an air-blast (effervescent) atomizer is combined with the well-known stretch-and-fold mechanism commonly used in mixing
high-viscosity fluids. The proposed technology is suitable to generate sprays of high-viscosity and non-Newtonian fluids, and in general enables liquid atomization at significantly lower pressures than conventional nozzles. A prototype spray generator based on this concept was designed, built,
and tested with two fluids: an aqueous glycerol solution and a Carbopol polymer dispersion in water. For each fluid, the spray generator performance was studied changing the mass flow rates of fluid and air, and the rotation speed. Shadowgraph images of the spray were analyzed with a custom Matlab application to determine the cone angle and the drop size distribution.
NUMERICAL INVESTIGATION OF MULTIPHASE FLOW INSIDE A PRESSURE SWIRL ATOMIZER AT THE INITIAL STAGE OF INJECTION
417-441
10.1615/AtomizSpr.2018022872
Alireza
Razeghi
Özyegin University, Mechanical Engineering Department, Istanbul, Turkey
Özgür
Ertunç
Mechanical Engineering Department, Ozyegin University, Cekmekoy, 34794, Istanbul, Turkey
atomization
pressure-swirl
CFD
injector
multiphase
VOF
Pulse-mode operating atomizers are widely used in industry. This paper presents the fluid flow details and characteristics inside a pulse-mode operating pressure swirl atomizer (PSA). Transient flow simulations are performed inside a PSA for different Reynolds numbers. Generation of thin liquid
film is shown as a function of time. Minimum required time to establish a full hollow cone liquid sheet is shown to decrease with the Reynolds number. However, when it is nondimensionalized by the ratio of atomizer volume over volume flow rate, it has been found that the nondimensional time for
flow establishment is almost constant over the range of Reynolds numbers studied. Additionally, the time evolution of liquid film, axial velocity, tangential velocity, and pressure field inside a pressure swirl atomizer are given. It is observed that liquid film thickness decreases with Reynolds numbers while cone angle increases. Additionally, the pressure drop and discharge coefficient variation with Reynolods number are illustrated and it has been shown that the discharge coefficient is almost constant as a function of Reynolds number while pressure drop increases considerably. Furthermore,
dissipation function distribution inside a pressure swirl atomizer at two locations (middle of swirl chamber and orifice section) are given. Finally, liquid sheet circumferential distribution along threedimensional flow structures and variation of angular momentum and swirl number versus time at
various locations are illustrated. It has been shown that the swirl number decreases in the orifice section, monotonically; however, angular momentum variation is not monotonic and first decreases in the orifice section and then increases.
LAGRANGIAN APPROACH TO AXISYMMETRIC SPRAY SIMULATION OF PINTLE INJECTOR FOR LIQUID ROCKET ENGINES
443-458
10.1615/AtomizSpr.2018022652
Kanmaniraja
Radhakrishnan
Graduate School, Department of Aerospace and Mechanical Engineering, Korea
Aerospace University, Goyang, Gyeonggi-do, 10540, Republic of Korea
Min
Son
Universität der Bundeswehr München
Keonwoong
Lee
Graduate School, Korea Aerospace University, Goyang, Gyeonggi, 412-791,
Republic of Korea
Jaye
Koo
School of Aerospace and Mechanical Engineering, Korea Aerospace University,
Goyang, Gyeonggi-do, 10540,
Dept. of Aeronautical & Mech. Engrg., Hankook Aviation Univ., Republic of Korea
pintle injector
Lagrangian approach
wave model
validation
simulation
Movable pintle injectors are installed in bipropellant rocket engines to control the mass flow rate of the propellants and allow deep throttling with high combustion performance. A thin liquid sheet is formed by ejecting the liquid radially around the end of the pintle. This sheet is broken by axially injecting a gas propellant from an annular gap around the pintle nozzle. The device features a movable
pintle rod, which allows the thickness of the liquid sheet to be changed. The volume of fluid modeling is used to estimate the varying thickness of the liquid sheet, which is equal to the pintle opening up to a critical point. A procedure with these results calculates the constants in a mathematical model of the liquid sheet breakup process. The comparison of breakup model constants with the pintle opening shows that the drop size constant B0 has increased and the breakup time constant B1 has decreased up to the critical point of the pintle opening due to an increase in the liquid mass flow rate, which is changed after the critical point of the pintle opening due to a slight decrease with the increase in the liquid mass flow rate. Axisymmetric spray simulation of the pintle injector, varying the drop size constant and breakup time constant in the breakup model, was performed using the Lagrangian
approach. As a result, the comparison of the simulation result with the experimental data of the spray angle and Sauter mean diameter shows that the simulation results obtained via the calculated constants depend on the varying liquid sheet thickness and exhibited a good agreement.
CORRELATIONS FOR EVAPORATION HISTORY OF FUEL DROPLETS RELEASED INTO A HIGH-PRESSURE NITROGEN CROSS-FLOW PREMIXER
459-480
10.1615/AtomizSpr.2018024885
Ahmad Kazemi
Fard
Mechanical Engineering Department, Tarbiat Modares University, Tehran
14115-111, Iran
Hassan
Khaleghi
Department of Mechanical Engineering, Tarbiat Modares University, Tehran,Iran
cross-flow
premix tube
droplet size
evaporation history
correlation
n-heptane fuel
Eulerian–Lagrangian
We report on the fundamentals of a new method for injection of fuel droplets into a cross-flow within a premixer, to improve its performance. We investigate evaporation history of various-sized n-heptane droplets in high-pressure and -temperature nitrogen gas, using a Lagrangian–Eulerian
numerical approach. Deploying the Peng–Robinson equation and Van der Waals mixing rule for phase equilibrium of the n-heptane–nitrogen system, we consider gas solubility at the droplet surface and real gas behavior in high pressures. A number of different-sized droplets are injected both
individually and collectively into cross-flow. The results indicate that in this situation, the interaction
among droplets is negligible. To demonstrate coherence among droplets, a correlation is provided to describe droplet evaporation history with respect to initial droplet size. In addition, by injecting a continuous radial spray perpendicular to the flow in the premix tube, results reveal that droplets are arranged radially based on their initial sizes in the gas flow.