Begell House Inc.
Atomization and Sprays
AAS
1044-5110
27
2
2017
DIRECT SIMULATIONS OF LIQUID SHEET BREAKUP IN PLANAR GAS BLAST ATOMIZATION
95-116
10.1615/AtomizSpr.2016014309
Rajesh
Reddy
Shiv Nadar University
Raja
Banerjee
Department of Mechanical and Aerospace Engineering, Indian Institute of Technology Hyderabad, Yeddumailaram, Telangana 502205, India
liquid sheet breakup
volume of fluid method
spray characterization
high fidelity simulations
planar sheets
High fidelity simulations offer a promising way to study primary breakup of liquid sheets. The present work aims at simulating liquid sheet breakup under the assumption of a 2D planar prefilming gas blast atomization. An in-house finite volume method based solver has been used in the study. Interface tracking is done using volume of fluid (VOF) methodology. The study analyzes the effect of parameters such as inner core gas velocity, outer gas velocity, and liquid sheet thickness on the atomization process. The spray is characterized in terms of liquid sheet breakup length, spray cone angle, and droplet size distribution. The obtained droplet size distribution closely represents lognormal distribution. The inner core gas velocity was found to have significant impact on liquid sheet breakup length and droplet mean diameter within the parametric range of this study. Additionally, increase in liquid sheet thickness has shown an increase in the sheet breakup length.
ANALYSIS OF PRIMARY BREAKUP IMAGES FROM AN ENGINE-RELATED SHEET ATOMIZER
117-130
10.1615/AtomizSpr.2016015909
F.
Mathieu
Institute of Heat and Mass Transfer, RWTH Aachen University, 52062 Aachen, Germany
Manuel Armin
Reddemann
Institute of Heat and Mass Transfer, RWTH Aachen University, Aachen, 52062,
Germany
Reinhold
Kneer
Institute of Heat and Mass Transfer (WSA), RWTH Aachen University, Augustinerbach 6, 52056 Aa-chen, Germany
primary breakup
sheet breakup
shadowgraphy
ballistic imaging
image analysis
GDI injector
A-nozzle
In this study sheet atomization from an engine-related outwardly opening hollow-cone injector with known geometry is examined by means of high-resolution shadowgraphy of the near-nozzle region. The investigated Reynolds and Ohnesorge numbers range from 300 to 21,000 and from 0.01 to 0.26, respectively, whereas the ambience was kept constant at atmospheric conditions. First the experimental setup and the measurement procedure are introduced, followed by a discussion of the applicability of ballistic imaging. The images indicate that classical shadowgraphy is the favorable technique for the present sprays and the pursued optical resolution. The acquired images are analyzed qualitatively and sheet breakup is classified in a Reynolds-Ohnesorge diagram marking the transition region from an intact to a fully atomized sheet. Finally the Fourier transforms of the images are investigated in order to derive quantified data for fully atomized sheets. Especially the frequency bandwiths contained in the images correlate well with the driving flow properties Reynolds and Ohnesorge number.
FLOW CHARACTERISTICS OF CLOSE-TYPE SWIRL INJECTORS MANUFACTURED BY A 3D PRINTER
131-137
10.1615/AtomizSpr.2016015596
Wonjae
Yoon
School of Mechanical Engineering, Chungbuk National University, Chungbuk, Korea
Kyubok
Ahn
School of Mechanical Engineering, Chungbuk National University, Chungbuk, Korea
3D printer
close-type swirl injector
discharge coefficient
spray angle
Though 3D printers have become popular for manufacturing prototypes in a number of fields, they are rarely used to make injectors due to the relatively large tolerances and surface roughnesses. The flow characteristics of a swirl injector are known to depend mainly on its geometric shape and the injection conditions. In the present research, the possibility of whether or not a 3D printing technique can be applied to manufacture a swirl injector has been examined. Using different printing directions and methods, three close-type swirl injectors were created on a 3D printer using a light polymerized process. For each injector, cold-flow tests were conducted to measure the mass flow rates, discharge coefficients, and spray angles, while changing the injection pressures. The data obtained from the printed injectors have been compared with those from a metal injector manufactured by mechanical machining. The results show that the quality of the printed injector depended on both the printing direction and method. If one chooses a suitable method for printing a close-type swirl injector, the injector could have a discharge coefficient within a 7.5% error and a spray angle within a 12% error.
NUMERICAL STUDY OF A SELF-PULSATING INJECTOR
139-149
10.1615/AtomizSpr.2016015702
Qing-Fei
Fu
School of Astronautics, Beihang University, Beijing 100191, China; Beijing Advanced Innovation Center for Big Data-Based Precision Medicine, School of Medicine and Engineering, Beihang University, Beijing 100083,
China; School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester M13 9PL, United Kingdom
Chao-Jie
Mo
School of Astronautics, Beijing University of Aeronautics and Astronautics, Beijing, China, 100191
Li-Jun
Yang
School of Astronautics, Beihang University, Beijing 100191, China; Beijing Advanced Innovation Center for Big Data-Based Precision Medicine,
School of Medicine and Engineering, Beihang University, Beijing 100083,
China
self-pulsating injector
fluidic oscillators
numerical simulation
Coanda effect
geometrical effect
This paper presents a simulation study of the internal flow of a self-pulsating injector adapted from the design of the Coanda-effect bistable feedback fluidic oscillator. The computational fluid dynamics (CFD) method is used to study the effects of geometric parameters on pulsation characteristics. The influence of four factors on the oscillatory flow field is examined: the specific value of the outlet height to the joint inlet height (α), the specific value of the length to the height of the amplifier channel (β), the inlet velocity (Vi), and the fluid material. Focus is concentrated on the influence of these factors on oscillation frequency and amplitude. It is found that the variation of both oscillation frequency and amplitude with inlet velocity is independent of fluid material. The effects of geometric change on the oscillator are presented, which are of instructive significance for the practical design of a self-pulsating injector. In addition, the linear response regime, where oscillation frequency is perfectly linear with respect to Reynolds number, is successfully reproduced in these simulations.
MULTIRESOLUTION RECONSTRUCTION OF LOCAL DROP-SIZE DISTRIBUTIONS AND LIQUID VOLUME CONCENTRATION FROM FINITE-WIDTH LASER DIFFRACTION DATA
151-167
10.1615/AtomizSpr.2016016271
Songrit
Tanchatchawan
Engineering Department, Thailand Institute of Scientific and Technological Research, Pathum Thani, Thailand
Pumyos
Vallikul
Department of Mechanical and Aerospace Engineering, Faculty of Engineering, King Mongkut's University of Technology North Bangkok, Thailand; Center on Energy Technology and Environment, Office of the Commission on Higher Education, Ministry of Education, Thailand
Pisit
Yongyingsakthavorn
Department of Mechanical and Aerospace Engineering, Faculty of Engineering, King Mongkut's University of Technology North Bangkok, Thailand
Christophe
Dumouchel
Université et INSA de Rouen,
France
multiresolution tomographic algorithm
volume-weighted drop-size distribution
laser diffraction
This paper introduces a multiresolution tomographic algorithm to reconstruct drop-size distribution and liquid volume concentration within local regions of sprays. The reconstruction procedures allow the size of the local regions to be designed adaptively such that the reconstruction results can be obtained at multiple resolutions. The algorithm employs the strip integration together with laser diffraction measurements with overlapping beam sampling. The algorithm has been tested with both the synthetic and measured line-of-sight data of a solid-cone spray. The reconstructed results from this algorithm are in the form of local volume-weighted drop-size distributions which contain both qualitative and quantitative information of the drop-size distribution. The reconstruction results are comparable to those obtained by using the classical reconstruction technique with a smaller laser beam diameter. The comparison shows good agreement. Furthermore the proposed measurement technique consumed less calculation time and spent fewer working hours on measurement setup procedures.
EFFECT OF ATOMIZER INTERNAL GEOMETRY ON THE INTERNAL AND EXTERNAL TWO-PHASE FLOW IN EFFERVESCENT ATOMIZATION
169-188
10.1615/AtomizSpr.2016013860
Mona Hassanzadeh
Jobehdar
Department of Mechanical and Materials Engineering, University of Western Ontario, London, Ontario, Canada
Kamran
Siddiqui
Department of Mechanical and Materials Engineering, University of Western Ontario, London, Ontario, Canada
Aly H.
Gadallah
Department of Mechanical and Materials Engineering, University of Western Ontario, London, Ontario, Canada; Department of Mechanical and Power Engineering, Tanta University, Tanta, Egypt
Wajid A.
Chishty
Institute for Aerospace Research National Research Council Canada, Ottawa, Ontario, Canada
effervescent atomizer
aerator tube
mixing zone
bubble size
spray quality
droplet size
high-speed imaging
An experimental study was conducted to study the internal and external two-phase flow in an effervescent atomizer using high-speed imaging. The impact of the aerator tube configuration and mixing zone length on the size of bubbles inside the mixing zone and the spray droplet characteristics at different gas-to-liquid flow rates ratios were studied. An aerator tube with the conical end base was manufactured and tested. It is observed that the separation bubble at the trailing edge is suppressed by this configuration, which resulted in more uniform and smaller bubbles compared to the standard aerator tube with a flat base. The length of the mixing zone was found to have an impact on the bubble size distribution inside the mixing zone; more uniform and smaller bubbles are generated in the shorter mixing zone. The mixing zone length, however, does not show a distinct impact on the droplet velocity and size. It is concluded that a conical base aerator tube and a shorter mixing zone could significantly improve the spray steadiness and the atomization process.