Begell House Inc.
Atomization and Sprays
AAS
1044-5110
22
9
2012
EVALUATION OF SPRAY EVOLUTION IN PHARMACEUTICAL TABLET COATING PROCESSES: THE EFFECTS OF DRUM ROTATIONAL SPEED AND DRYING AIR FLOW RATE ON SPRAYS' CHARACTERISTICS
715-731
10.1615/AtomizSpr.2012006039
Ariel
Muliadi
Small Molecule Pharmaceutical Sciences, Genentech, South San Francisco, CA, USA
Paul E.
Sojka
Maurice J. Zucrow Laboratories (formerly Thermal Sciences and Propulsion Center), School of Mechanical Engineering, Purdue University, West Lafayette, Indiana, 47907-2014, USA
pharmaceutical
spray
tablet
coating
PDA
pattern
Sprays produced by a pharmaceutical nozzle were characterized in a 120 cm (24 in.) diameter tablet pan-coater at four different sets of operating conditions: stationary drum with drying air turned on/off, and 8 rpm rotating drum with drying air turned on/off. Turning drying air on resulted in up to a 6 m/s increase in drop velocity, but had mixed effects on drop size. When the spray gun produced mostly small drops (D10 < 10 µm), supplying drying air to the drum led to an increase in D32. The reverse was observed when the spray was composed of mostly large drops. Both observations likely arose from drop evaporation. Supplying drying air also reduced spray extent and volume flux magnitude. Adding drum rotation generally led to (i) increased drop size and (ii) decreased drop velocity. Condition (i) likely arose from the transport of small drops away from the spray zone, while (ii) likely resulted from changes in droplet trajectories. Both resulted from gas-phase swirling that was induced by the drum rotation. The influence of drum rotation on drop velocity diminished when drying air flow was included as the drying air momentum helped the drops oppose the effects of the drum rotation-induced swirling flow.
ON THE DISINTEGRATION OF FAN-SHAPED LIQUID SHEETS
733-755
10.1615/AtomizSpr.2012006220
Mireia
Altimira
Department of Mechanics, Kungliga Tekniska Hogskolan, Osquars Backe 18, SE-100 44 Stockholm, Sweden
Alejandro
Rivas
Thermal and Fluids Engineering Division, Mechanical Engineering Department, Tecnun (University of Navarra), Manuel de Lardizabal 13, 20018 Donostia-San Sebastian, Spain
Juan Carlos
Ramos
Thermal and Fluids Engineering Division, Mechanical Engineering Department, Tecnun (University of Navarra), Manuel de Lardizabal 13, 20018 Donostia-San Sebastian, Spain
R.
Anton
Thermal and Fluids Engineering Division, Mechanical Engineering Department, Tecnun (University of Navarra), Manuel de Lardizabal 13, 20018 Donostia-San Sebastian, Spain
atomization
experimental characterization
visualization techniques
liquid sheet
primary breakup
rim breakup
This paper presents a combined experimental and theoretical investigation of the disintegration of fan-shaped liquid sheets produced by industrial fan-spray atomizers. The disintegration regimes observed for different geometries and operating conditions are described, proving the paramount role of nozzle flow on the final characteristics of the spray produced. The concept of breakup length is redefined to account for the stochastic nature of liquid stream disintegration. An analogy is established between the breakup of a liquid sheet dominated by the wave mode and a radial sheet, obtaining good agreement with the experiments. However, in those cases where several disintegration regimes coexist, the breakup length cannot be given by an analytical expression. Finally, the influence of the disintegration regime on both the droplet size and the spatial distribution of the droplets is investigated, confirming the strong influence of rim breakup.
LIQUID FILM DYNAMIC ON THE SPRAY IMPINGEMENT MODELING
757-775
10.1615/AtomizSpr.2012006400
Christian M. G.
Rodrigues
Aerospace Sciences Department, University of Beira Interior, Rua Marques Avila e Bolama, 6201-001 Covilha, Portugal
Jorge
Barata
Aerospace Sciences Department, University of Beira Interior, Rua Marques Avila e Bolama, 6201-001 Covilha, Portugal
Andre
Silva
AEROG, LAETA, Aeronautics and Astronautics Research Center, University of Beira Interior, Calcada Fonte do Lameiro 6201-001 Covilha, Portugal
spray impingement
droplets-wall interaction
liquid film
splash regime
The present paper addresses a liquid film submodel included into a computational model that aims at reproducing the spray impingement phenomena. This numerical extension incorporates the spread of the liquid film over the neighboring nodes due to the dynamic motion induced by the film inertia and also the exchange of mass between the liquid layer and the incident and splashing particles. Moreover, a dimensionless film thickness parameter is embedded in the submodel by mean of an experimentally deduced correlation that can be fitted and updated to specified conditions. In order to realize how the model behaves with different influencing parameters, a thorough investigation is performed: the results that are obtained with and without the inclusion of the liquid film submodel are compared against the experimental data for two crossflow velocities. The integration of the computational extension with the spread/splash transition criterion is also evaluated by considering two types of expressions: one that includes the effect of the film thickness and one that does not. The results show that the latter option combined with the submodel does not distinctly enhance the simulation results, contrary to what happens with the transition criterion that considers the film thickness as an influencing parameter. In this case, the model with the computational extension reveals better prediction results, which indicates the necessity of considering it for spray impingement simulations along with a splash threshold that depends on the liquid layer.
ENGINE COMBUSTION NETWORK (ECN): CHARACTERIZATION AND COMPARISON OF BOUNDARY CONDITIONS FOR DIFFERENT COMBUSTION VESSELS
777-806
10.1615/AtomizSpr.2012006083
Maarten
Meijer
Eindhoven University of Technology, Netherlands
Bart
Somers
TU/e, The Netherlands
Jaclyn
Johnson
Michigan Technological University, USA
Jeffrey
Naber
MTU, USA
Seong-Young
Lee
MTU, USA
Louis Marie C.
Malbec
IFP Énergies nouvelles (IFPEN), 1-4 av. Bois Preau, 92852 Rueil-Malmaison, France
Gilles
Bruneaux
IFPEN
Lyle M.
Pickett
Combustion Research Facility, Sandia National Laboratories, P.O. Box 696,
Livermore, CA 94551, USA
Michele
Bardi
ETHZ
Raul
Payri
CMT-Motores Térmicos, Universitat Politècnica de València, València, Spain
Tim
Bazyn
Caterpillar Inc., Peoria, Illinois 61629, USA
diesel
sprays
combustion
combustion vessels
experimental methodologies
boundary conditions
temperature characterization
spray modeling
TSL
The Engine Combustion Network (ECN) is a worldwide group of institutions using combustion vessels and/or performing computational fluid dynamics (CFD) simulation, whose aim is to advance the state of spray and combustion knowledge at engine-relevant conditions. A key activity is the use of spray chamber facilities that operate at high-temperature, high-pressure conditions typical of diesel combustion, which are operated at specific target conditions in order to leverage research capabilities and advanced diagnostics of all ECN participants. The first target condition, called "Spray A," has been defined with detailed ambient (900 K, 60 bar, 22.8 kg/m3, 15% oxygen) and injector (common rail, 1500 bar, KS1.5/86 nozzle, 0.090-mm orifice diameter, n-dodecane, 363 K) conditions. Establishing and improving these experimental boundary conditions in unique facilities throughout the world represents a major step forward in the establishment of high-quality, quantitative data sets for engine spray combustion. This paper is a review of the methodology to characterize and control the ambient and fuel-injector boundary conditions (e.g., temperature, pressure, composition) as offered by six different participating institutions of the ECN, each targeting the Spray A conditions and quantifying experimental uncertainty. Constant-pressure flow (CPF) and constant-volume preburn (CVP) chambers with various ambient gas composition are compared for the first time. Experimental diagnostics include the use of fast-response, radiation-corrected thermocouples for spatially resolved gas and fuel-injector temperature, laser-induced phosphorescence for surface temperature, and high-speed transducers for pressure. With guidance about the uncertainty and variation that exists between facilities, simplified models are then employed to understand how these boundary condition variations may affect aspects of spray combustion. Ambient gas and fuel temperature effects on liquid- and vapor-phase penetration are examined with established one-dimensional models. Chemical kinetics modeling in single- or multi-zone reactors is used to predict the influence of different preburn environments on the major and minor species present in the ambient gas at the start of injection, and their subsequent effect on spray ignition. This review article provides recognition of the challenge in creating well-controlled high-temperature, high-pressure environments, and identifies which boundary condition variations are expected to have the highest impact on spray combustion.