Fundamental analysis of liquid breakup mechanism in a rotary atomizer with square discharge orifice

[EN] An experimental investigation of breakup mechanism in a rotary atomizer with square shape discharge orifice at ambient condition has been performed. The effects of a high aspect ratio noncircular discharge channels, particularly a square shape discharge channel, are considered. The motivation of this study is the use of this type of orifice in some small gas turbine engines as well as non-existing observation in literature concerning about high aspect ratio of discharge channel. Visualization experiments are conducted by high speed shadowgraph imaging technique with pulsed light illumination for the first time. The effects of rotational speed and volume flow rate are studied on the breakup structure. The visualizations indicates that the liquid film formed along the channel is pushed to one side of it due to Coriolis force which is dominant in this type of atomizer. Accordingly a crescent shaped liquid film is formed at the square channel exit covering two corners of the square, resulting the combination of Coriolis induced stream mode and surface tension induced stream mode breakup. Observations of the breakup process for different volume flow rates and rotational speeds indicate that the breakup of liquid film stream is dependent on injection conditions and the corresponding cross flow velocity created by atomizer rotation. The breakup regime map is provided as a function of weber number and momentum flux ratio. Four distinct regimes are identified: Rayleigh breakup, bag breakup, multimode breakup, and shear breakup. The present results leads to understanding atomization performance and creating some idea to improved spray quality in this type of atomizer.Ghorbanhoseini, M.; Rezayat, S.; Farshchi, M. (2017). Fundamental analysis of liquid breakup mechanism in a rotary atomizer with square discharge orifice. En Ilass Europe. 28th european conference on Liquid Atomization and Spray Systems. Editorial Universitat Politècnica de València. 496-503. https://doi.org/10.4995/ILASS2017.2017.5640OCS49650

Concepts for radically increasing the numerical convergence rate of the Euler equations

Integral equation and finite difference methods have been developed for solving transonic flow problems using linearized forms of the transonic small disturbance and Euler equations. A key element is the use of a strained coordinate system in which the shock remains fixed. Additional criteria are developed to determine the free parameters in the coordinate straining; these free parameters are functions of the shock location. An integral equation analysis showed that the shock is located by ensuring that no expansion shocks exist in the solution. The expansion shock appears as oscillations in the solution near the sonic line, and the correct shock location is determined by removing these oscillations. A second objective was to study the ability of the Euler equation to model separated flow

ON THE EFFECT OF USING CUBIC BOXES ON VOCABULARY ACQUISITION OF EFL YOUNG LEARNERS

Vocabulary acquisition has long been a major concern among EFL instructors teaching young learners. Among all the techniques proposed for vocabulary retention and enhancement among young learners, using cubic boxes can play a pivotal role in developing and activating young learners to acquire elementary vocabularies more effectively. It was proven in this study that cooperative vocabulary activities among those young leaners applying cubic boxes outweighs the ones who try to acquire new words via traditional pen-and-paper techniques. Thus, using cubic boxes possesses a major function in vocabulary enhancement and retention of young learners of English. Moreover, vocabulary learning based on the adaptation of the cubic boxes is highly cooperative and leads to more dynamic learning rather than individual vocabulary learning in language classrooms.  Article visualizations

Microfluidic biosensing of circulating tumor cells (CTCs): Recent progress and challenges in efficient diagnosis of cancer

Cancer metastasis is one of the foremost causes of cancer incidence and fatality in the whole of the world. Circulating tumor cells (CTC) have been confirmed to be among the most significant stimuli of metastasis in recent years and presently are the subject of extensive research aiming to be accurately identified by using biological and physical properties. Among the various studies conducted for isolation, identification, and characterization of CTCs, microfluidic systems have aroused great attention owing to their unique advantages such as low-cost, simplicity, reduction in reagent consumption, miniaturization, fast and precise control. The purpose of this review is to provide an overview of current state of the microfluidic biosensors for the screening of CTCs. Additionally, given the recent progress in this field, future outlook for the development of the microfluidics biosensing is briefly discussed

Design, development and operation of a laboratory pulsed plasma thruster for the first time in West Asia

Although the pulsed plasma thruster (PPT) was first utilized on a space mission in 1964, after more than four decades, it is still a space-rated technology which has performed various propulsion tasks, from station-keeping to three-axis attitude control for a variety of former missions. With respect to the rapid growth in the small satellite community and the growing interest for smaller satellites in recent years, the PPT is one of the promising electric propulsion devices for small satellites (e.g., CubeSats) due to the following advantages: simplicity, lightweight, robustness, low power consumption, low production cost and small dimensions. Therefore, a laboratory benchmark rectangular breech-fed pulsed plasma thruster using a self-inductor as a coupling element was designed, developed and successfully tested in a bell-type vacuum chamber at 10-4 Pa for the first time in west Asia (Iran). The PPT has been tested using a 35 μF, 2.5 kV oil-filled capacitor, producing an impulse bit varying from 300 μN-s to 1.3 mN-s at a maximum specific impulse of 1100 s. As a result a research program in Iran was initiated for working on PPTs and the miniaturization of PPTs while increasing the performance parameters. The present paper briefly reviews the PPT design and development

High-speed imaging database of water jet disintegration Part II : Temporal analysis of the primary breakup

This paper is Part II of a series of articles focusing on the disintegration of a cylindrical (Ø=0.60 mm diameter) water jet in a quiescent atmosphere, from Rayleigh to early atomization breakup regimes. Liquid fluorescence high-speed imaging is used here, instead of shadowgraphy, providing a more faithful representation of liquid jet breakup dynamics as described in Part I (Roth et al., 2021). Using these data, the aim of this article is to perform a temporal analysis of the primary breakup process and to investigate the variation of breakup length in the time-domain, under each breakup regime. The results indicate that the liquid jet velocity at the onset of primary breakup oscillates within 6% of the liquid injection velocity for all considered operating conditions. The analysis of the dynamic instability is also performed, showing the growth rate of the first three high-energy-containing modes. The results confirm that there is no single disturbance at a specific frequency whose growth rate leads to liquid jet disintegration in the second wind-induced breakup regime and the early atomization regime. However, it is found that the dimensionless mean breakup length monotonically varies with the product of the dimensionless amplitude by the dimensionless temporal growth rate. The values provided for the dominant frequencies and growth rate of disturbances can be useful for modelers simulating the breakup of liquid jets in a quiescent atmosphere. Finally, the temporally resolved image series analyzed in this article can be further investigated and compared with simulation results, by downloading the processed image data on the website: https://spray-imaging.com/water-jet.html or alternatively on Open Science Framework at: https://doi.org/10.17605/OSF.IO/CG3D

A parametric study of the effect of discharge energy on PPT performance

Pulsed Plasma Thruster (PPT) is one of the promising space propulsion devices for the micro- and nano-satellites as the following advantages: simplicity, lightweight, robustness, and low power consumption. Moreover, PPT can generate very small impulse bits with high specific impulse. Therefore PPT has great advantages as a precision attitude control. Although μPPTs and their relevant issues have been investigated to a certain degree in recent years, but as a result of the fact that PPT performance is a function of a lot of different parameters like geometrical dimensions, discharge energy, capacitor characteristics, etc and also because of its sophisticated physics; it is felt that issues related to developing an optimized μPPT needs to be investigated in greater detail for a PPT with smaller dimensions and better performance. Therefore, following the development of a laboratory benchmark rectangular breech-fed PPT, a wide range parametric study has been conducted on investigating the effect of discharge energy on PPT performance. The PPT impulse bit varied from about 0.4 mN-s to more than 1.3 mN-s while discharge energy changed from less than 10 J to more than 50 J. Specific impulse also increased from 200 s to 110 s. This paper reviews the results of the mentioned parametric study in brief

Explore and identify indicators of customer loyalty to the brand in the furniture industry by AHP

Nowadays, producers are successful in Of getting profit in more efforts to satisfy our customers in target markets And build customer loyalty to your brand. The aim of this study was to study and identify factors influencing loyalty Customer to the brand in the furniture industry using Group Decision Making method., For the purpose of study and research Been done by others, the factors affecting customer loyalty divided in to 4 main categories and 20 sub-indicators. After getting customer buyer furniture opinions via questionnaire, the priority rates of obtained criteria and sub-criteria were determined by Analytical Hierarchy Process (AHP).The results show that customers Satisfaction and marketing criteria have the highest weighting values at the first level. In addition, among 20 effective sub-criteria, Influence on customer loyalty in the furniture dustry, service quality ,reasonable price ,installment sales, warranty and perceived quality have highest priorities as 0.323, 0.151,0.129, 0.074 and 0.053 weighting values, respectively