Begell House Inc.
Atomization and Sprays
AAS
1044-5110
24
1
2014
MACROSCOPIC SPRAY CHARACTERISTICS OF A POROUS INJECTOR
1-22
10.1615/AtomizSpr.2013006408
Dohun
Kim
Department of Aerospace and Mechanical Engineering, Graduate School of Korea Aerospace University, Korea
Inchul
Lee
Department of Aerospace and Mechanical Engineering, Graduate School of Korea Aerospace University, 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
porous injector
two-dimensional injector
breakup length
spray boundary detection
momentum flux ratio
The concept of coaxial porous injector design for gas-liquid mixing involves improved momentum transfer between the gas and liquid jets by changing the gas injecting direction of a conventional liquid-centered shear coaxial injector from parallel to perpendicular using porous material. Cold-flow tests of the coaxial porous injector and the shear coaxial injector in two-dimensional configurations were carried out to compare the macroscopic characteristics of sprays from each injector and to understand the effects of spraying conditions on the breakup length and the spray angle. The spray patterns were visualized using the shadowgraphy technique. The shadowgraph images recorded in high speed were post-processed to detect the breakup length and the spray angle. The post-processing code filters the dynamic pixels, and leaves the stationary pixels, which corresponds to the liquid core and the background. The most significant differences between the porous injector and the shear injector in the two-dimensional configurations were the spray angle and the uniformity of the disintegrated liquid jet. The liquid column from the shear injector was not split off entirely, and only the portion at the interface between the gas and liquid jet was atomized by the shear force. On the other hand, the liquid jet from the porous injector dispersed more widely, and was disintegrated into droplets more completely in most experimental cases of similar axial momentum flux ratio conditions at the injector tip, and it was thought that an optimal porous element length for the best mixing performance exists at certain injection conditions.
THEORETICAL ANALYSIS OF SURFACE WAVES ON A ROUND LIQUID JET IN A GASEOUS CROSSFLOW
23-40
10.1615/AtomizSpr.2013008203
Shaolin
Wang
National Key Laboratory on Aero-Engines, School of Energy and Power Engineering, Beihang University, Beijing, 100191, China
Yong
Huang
National Key Laboratory of Science and Technology on Aero-Engine Aero-thermodynamics, School of Energy and Power Engineering, Beihang University, Beijing 100191, China;
Collaborative Innovation Center of Advanced Aircraft-Engine, Beijing 100191, China
Z. L.
Liu
National Key Laboratory on Aero-Engines, School of Energy and Power Engineering, Beihang University, Beijing, 100191, China
linear stability analysis
round liquid jet
crossflow
Rayleigh-Taylor waves
momentum ratio
A theoretical investigation is described to study the surface waves on a round liquid jet in a gaseous crossflow, especially Rayleigh-Taylor waves. The linear stability analysis was used to derive the dispersion relation. The acceleration on the liquid jet due to the transverse aerodynamic force was considered in the relation. Results indicate that the hydrodynamic instability is dominated by three terms which are caused by jet velocity, surface tension, and aerodynamic force, respectively. The surface tension contributes to the instability when the wave number is less than unity. Both gas and jet velocities can affect the optimum wavelength and the surface wave growth rate. The critical momentum ratio, at which the contribution of the liquid jet Weber number to the maximum growth rate is as large as that of the cross air Weber number to the maximum growth rate, decreases with the gas Weber number exponentially. If the momentum ratio is less than the critical value, the axial optimum wavelength can be expressed as a power function of gas Weber number. Otherwise, free jet instability theory can be used to study the surface waves on the liquid jet in cross airflow.
DEVELOPMENT OF A NEW SPRAY/WALL INTERACTION MODEL FOR DIESEL SPRAY UNDER PCCI-ENGINE RELEVANT CONDITIONS
41-80
10.1615/AtomizSpr.2013008287
Yanzhi
Zhang
School of Energy and Power Engineering, Dalian University of Technology, P. R. China
Ming
Jia
Key Laboratory of Ocean Energy Utilization and Energy Conservation of
Ministry of Education, School of Energy and Power Engineering, Dalian
University of Technology, Dalian, 116024, P.R. China
Hong
Liu
Key Laboratory of Ocean Energy Utilization and Energy Conservation of
Ministry of Education, School of Energy and Power Engineering, Dalian
University of Technology, Dalian, 116024, P.R. China
MaoZhao
Xie
Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education,
Dalian University of Technology, Dalian City, P.R. China
Tianyou
Wang
State Key Laboratory of Engines, Tianjin University, 92 Weijin Road, Tianjin 300072, China
Lei
Zhou
State Key Laboratory of Engines (SKLE) Tianjin University
spray/wall interaction model
diesel spray
injection timing
PCCI engines
A new spray/wall interaction model was developed with special emphasis on the premixed charge compression ignition (PCCI) engine-relevant conditions, i.e., high injection pressure and intermediate-to-high backpressure. The new model distinguishes between dry wall and wetted wall for a description of the complicated spray/wall interaction process. The dry wall impingement regimes include deposition and splash, whereas the wetted wall regimes consist of stick, rebound, spread, and splash. The regime transition thresholds of splash are determined based on recent experimental observations, which can account for the wide ranges of conditions related to engines. By using an updated log-normal distribution function, the sizes of the secondary droplets are determined in the improved model, which is more suitable to describe the atomization process of the secondary droplets formed by splash. Moreover, the velocities of the secondary droplets are determined by a Nukiyama-Tanasawa distribution function derived from the experimental measurements, and the ejection angle of the secondary droplet is assumed to be in the interval (2°, 30°) uniformly, which is reasonable for high injection pressure. In order to validate the new spray/wall interaction model, comparisons of the predictions from the present model with the experimental measurements and predictions from a previous spray/wall interaction model were conducted. The results indicate that the numerical predictions from the new model illustrate better agreements with the experimental data than those of the previous model, especially in the case with high injection pressure under PCCI-engine relevant conditions.
EFFECT OF THE LIQUID INJECTION ANGLE ON THE ATOMIZATION OF LIQUID JETS IN SUBSONIC CROSSFLOWS
81-96
10.1615/AtomizSpr.2013008310
H.
Almeida
Mechanical Engineering Department, Instituto Superior Tecnico, University of Lisbon, Avenida Rovisco Pais, 1049-001 Lisbon, Portugal
J. M. M.
Sousa
Mechanical Engineering Department, Instituto Superior Tecnico, University of Lisbon, Avenida Rovisco Pais, 1049-001 Lisbon, Portugal
Mário
Costa
IDMEC, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal
pressure atomizer
liquid spray
angled injection
air crossflow
This work is focused on the study of sprays produced by pressure atomizers of single-hole type when subjected to air crossflows at atmospheric pressure. The study was carried out in a wind tunnel. Prior to spray characterization, the airflow inside the wind tunnel was evaluated with the aid of laser Doppler anemometry. The sprays were first characterized using a shadowgraphy technique, which allowed for a qualitative evaluation of the overall quality of the atomization. Subsequently, the use of phase Doppler anemometry allowed performing detailed measurements of the spray droplet diameters and velocities, as a function of the injection angle, for various nondimensional atomizer distances. The main findings of this study are as follows: (i) The liquid column disintegration process is significantly affected by the liquid injection angle and, less considerably, by the liquid-to-air momentum flux ratio; (ii) the Sauter mean diameter decreases noticeably as the injection angle of the liquid increases; and (iii) the characteristics of droplet diameter and velocity distributions vary significantly as the distance to the injector increases.