Swirl Chamber Diameter Research Articles

Experimental studies on the unsteady atomization characteristics of a swirl injector

This paper studies the spray and dynamic respond characteristics of a swirl injector under the different unsteady experimental conditions. The flow pulsation and injector geometric parameters, such as the pulsation frequency and swirl chamber length, on the atomization features like average liquid sheet thickness and spray angle have been comprehensively measured. It is indicated that the whole pulsation range could be divided into different parts based on the pulsation frequencies of incoming flow. Experimental results reveal that the liquid sheet thickness and Sauter Mean Diameter (SMD) amplitude would decrease in the square and bimodal regions and then remain unchanged in the triangular region. Both of them would increase with the tangential channel diameter and swirl chamber length while the steady incoming pressure drop shows an opposite impact on them. Besides, the spray performance of swirl injector could be improved by rising the swirl chamber diameter.

Study of pressure-swirl atomizer with spiral path at design point and outside of design point

Studies on pressure-swirl atomizers have mainly focused on pressure-swirl atomizers with tangential input while there are limited studies on pressure-swirl atomizers with a spiral path. This study applies experimental and computational methods to provide a better understanding of flow development in this type of atomizer at the design point and outside the design point. Experimental results showed that as the pressure increases, the spray cone angle increases. This increase initially occurs with a higher slope and then the slope is toned down. While the drainage coefficient remains constant, the droplet diameter decreases as the pressure increases. It is observed that similar to the pressure-swirl atomizer with tangential input, the pressure-swirl atomizer with a spiral path has a conical hollow spray. At the constant mass flow rate, as the spiral path cross-section, the length of the swirl chamber and orifice diameter increase, the fluid film thickness and average diameter of droplets increase while the spray cone angle reduces. Further, increasing the number of spiral paths causes a wider spray cone angle, higher discharge coefficient, larger fluid film thickness, and larger droplet diameter. The results also showed that increasing the length of the orifice marginally affected the properties of the spray while significantly reducing the spray cone angle. It is important to note that the numerical results are in good agreement with the experimental data.

Pareto optimal design of swirl cooling chambers with tangential injection using CFD, GMDH-type of ANN and NSGA-II algorithm

In this research, with regards to the considered geometrical parameters, a multi-objective optimization has been performed with the goal of achieving maximum heat transfer and minimum pressure loss in a swirl chamber. This objective has been accomplished by using the Computational Fluid Dynamics (CFD) technique, GMDH type Neural Network and the NSGA-II multi-objective optimization algorithm. The design variables include the ratio of inlet slot width to swirl chamber diameter, ratio of inlet slot height to swirl chamber diameter and the inlet slot angle. These variables are just related to geometrical parameters; and the Reynolds number, tangential jet temperature and the wall temperature are considered as constant. The objective functions include the averaged Nusselt number over swirl chamber wall and the pressure loss coefficient. CFD technique is used to analyze the flow and heat transfer and to compute the values of objective functions. The polynomials that relate the objective functions to input variables are obtained by means of GMDH algorithm. The obtained models are used to predict the values of objective functions as inputs for NSGA-II multi-objective optimization. Considering the range of changes of design variables, Pareto optimal points are obtained for the objective functions, and the Pareto points with special characteristics are introduced and discussed.

Dynamic Characteristics of Open-Type Swirl Injector with Varying Geometry

Combustion instabilities in a liquid rocket engine are generated by coupling between the heat release oscillations and the acoustic pressure oscillations in the combustion chamber. These instabilities from the combustion chamber can affect the injector and the feed line, which are in front of the combustion chamber. These oscillation transfers could influence the combustion instability in liquid rocket engines. A properly designed injector can be used to prevent these transfers and suppress combustion instability. For this reason, the dynamic characteristics of the injectors must be studied. Open-type swirl injectors were designed to investigate the dynamic characteristics through experimental study. The injectors were designed with replaceable parts to change the swirl chamber length, swirl chamber diameter, tangential entry number, and manifold diameter. A hydrodynamic mechanical pulsator that produces pressure oscillations in the feed line was installed in front of the manifold of the open-type swirl injector. The pressure in the manifold, the liquid film thickness, and the pressure at the exit of the open-type swirl injector were measured to understand the dynamic characteristics of the open-type swirl injector. As a result, the open-type swirl injector’s response characteristics to pressure fluctuation inputs with different geometries were obtained. The tendencies of the output parameters acquired in the study could be used to adjust the injector design to suppress combustion instability in liquid rocket engines.

Closed-type 스월 인젝터의 스월 챔버 형상에 따른 분무특성 연구

Purdue 대학교의 Ismailov 등이 수행한 closed-type 스월 인젝터의 동특성에 대한 모델링 및 계산 결과를 실험을 통해 확인하고자 하는 과정의 일환으로 수행된 연구이다. Closed-type 스월 인젝터의 스월 챔버의 길이와 지름의 영향이 인젝터의 동특성에 미치는 영향을 관찰하고자 스월 챔버의 길이와 지름을 변화시킬 수 있는 인젝터를 제작하였다. 이러한 과정에서 closed-type 스월 인젝터의 동특성에 대한 실험을 진행하기에 앞서서 정적인 분무 특성을 확인하였다. 인젝터 전단에 설치된 유량계를 통하여 유량을 확인하였으며, Lefebvre의 방식에 따라 closed-type 스월 인젝터의 오리피스에 전극을 설치하여 매니폴드 압력에 따른 액막 두께의 변화를 측정하였다. 또한 압력별로 촬영된 순간적인 분무 사진을 통하여 매니폴드 압력에 따른 분사각과 분열길이의 변화를 관찰하였다. This study has been done as a preliminary work in the process of confirming the modeling and calculation results on the dynamic characteristics of closed-type swirl injector which were performed by Ismailov et al. in Purdue university. Closed-type swirl injectors with replaceable swirl chamber parts were designed and manufactured. The steady state spray characteristics of closed-type swirl injector with varying swirl chamber length and diameter were verified. Mass flow rate was measured with a mass flow meter installed in front of the injector, and liquid film thickness was measured by Lefebvre's method with electrodes installed at the orifice of the injector. Variation of spray cone angle and break-up length were investigated from the spray images captured under different manifold pressure conditions.

오픈형 스월 인젝터의 스월 챔버 형상 변화에 따른 동특성 연구

Swirl injectors are widely used for Liquid Rocket Engine(LRE) as fuel injection system and following researches are also being carried out throughout the world. Especially, solving combustion instability problem is essential for every type of LREs. In this study, cold test was carried out for open type swirl injector as a fundamental research to solve combustion instability problem. Pressure fluctuation was applied to the inlet flow coming into the injector and the following response characteristics were observed. The effect of swirl chamber geometry was also studied by changing both swirl chamber length and diameter.

Theoretical performance simulation of a high pressure agro-forestry swirl nozzle

Equations of dynamic systems in droplet distribution at high pressure and boundary value flows in the swirl chamber of a swirl nozzle were used in conjunction with momentum equations of forces on moving curved vanes to develop mathematical models. A computer program in C++ language was developed and used to simulate the effect of some flow and geometric parameters, including flow rate, pressure and swirl chamber diameter, on the spray performance of a high pressure agro-forestry swirl nozzle. Each of the three performance parameters of axial flow rate, spray cone angle and output discharge (or performance) coefficient were studied as a function of any two combinations of the nozzle supply pressure, exit orifice diameter and swirl chamber diameter. The study established that the spray cone angle of the discharge flow pattern varied from the minimum value of 40

G050076 旋回流方式マイクロバブル発生器における気泡微細化 : 渦流室径の影響

Swirl-type micro-bubble generator has an advantage over others in that it can generate micro-bubble easily under low supplied pressure. In order to make the device generating micro-bubbles under low supplied pressure, swirl-type micro-bubble generator was investigated by changing swirl chamber diameter. Therefore the performance of swirl-type micro-bubble generator was evaluated by measuring the diameter of generated bubbles by the image measurement method. Moreover the swirl velocity and radial velocity distribution around exit of swirl-type micro-bubble generator was measured. The area in which swirl-type micro-bubble generator generated bubbles was observed by high speed camera. It was clarified that the diameter of bubbles generated by swirl-type micro-bubble generator became small, the swirl and the radial velocity increased with swirl chamber diameter.

Experimental Study on Simplex Swirl Injector Dynamics with Varying Geometry

The effects of swirl chamber’s diameter and length on injector’s dynamic characteristics were investigated through an experimental study. A mechanical pulsator was installed in front of the manifold of a swirl injector which produces pressure oscillations in the feed line. Pressure in the manifold, liquid film thickness in the orifice and the pressure in the orifice were measured in order to understand the dynamic characteristic of the simplex swirl injector with varying geometry. A direct pressure measuring method (DPMM) was used to calculate the axial velocity of the propellant in the orifice and the mass flow rate through the orifice. These measured and calculated values were analyzed to observe the amplitude and phase differences between the input value in the manifold and the output values in the orifice. As a result, a phase-amplitude diagram was obtained which exhibits the injector’s response to certain pressure fluctuation inputs. The mass flow rate was calculated by the DPMM and measured directly through the actual injection. The effect of mean manifold pressure change was insignificant with the frequency range of manifold pressure oscillation used in this experiment. Mass flow rate was measured with the variation of injector’s geometries and amplitude of the mass flow rate was observed with geometry and pulsation frequency variation. It was confirmed that the swirl chamber diameter and length affect an injector’s dynamic characteristics. Furthermore, the direction of geometry change for achieving dynamic stability in the injector was suggested.

Flow of power-law fluids in simplex atomizers

This paper presents a computational analysis of flow of time-independent, purely-viscous, power-law fluids in simplex atomizers using the volume-of-fluid (VOF) method. Flow of shear-thinning (0.4 < n < 1), Newtonian ( n = 1) and shear thickening fluids (1 < n < 1.2) has been considered. The effect of power-law index and atomizer geometry on the flow and atomizer performance has been investigated. Three geometry parameters have been considered, viz., the atomizer constant which is the ratio of inlet area to the product of swirl chamber diameter and the exit diameter, the ratio of swirl chamber diameter to exit orifice diameter, and the length-to-diameter ratio of the exit orifice. The dimensionless film thickness at exit, spray cone angle, and the discharge coefficient for different values power-law index as well as those with varying atomizer geometry are reported. The pressure drop across the atomizer has been kept constant in all simulations. A change in the power-law index significantly alters the flow field in the in the swirl chamber of the atomizer. The velocity magnitudes and liquid film thickness at the orifice exit change with the power-law index. With fixed atomizer geometry, the pseudoplastic fluids tend to produce thinner liquid sheet, larger spray cone angle, and have lower discharge coefficient compared to dilatant fluids. Changes in the atomizer geometry have a significant impact on the flow for all values of power-law index. The spray cone angle decreases and the discharge coefficient and the film thickness increase with increasing atomizer constant. With increasing D s/ d o, the dimensionless film thickness at exit increases whereas the dimensional film thickness decreases monotonically. The discharge coefficient increases and the spray cone angle decreases with increasing D s/ d o. The discharge coefficient, the spray cone angle, and the film thickness decrease with increasing l o/ d o. A significant finding is that the variations of film thickness, spray cone angle, and discharge coefficient with a change in atomizer geometry are similar for different values of fluid power-law index, although the numerical values depend on the power-law index. This has important implications for atomizer design and industrial applications as most atomizers are designed for, and characterized with, Newtonian fluids.

배부식 방제기를 위한 디스크형 노즐 개발

This study was performed to evaluate some geometrical characteristics of disc type swirl nozzles and to develop nozzles having improved spraying performance for knapsack sprayers. Considered geometrical characteristics of the nozzles were disc thickness, orifice diameter, swirl chamber diameter and shape of the swirl chamber (nozzle chamber). 3 types of nozzle cores were compared. Main results of this study were as follows. 1. Spraying angle (A) was increased with decreasing disc thickness (x), and with increasing orifice diameter (y) or spraying pressure (z). The equation was as a follow. $$A

Influences of nozzle flow and nozzle geometry on the shape and size of an air core in a hollow cone swirl nozzle

Theoretical and experimental studies have been carried out to determine the influences of nozzle flow and nozzle geometry on the shape and size of a fully developed air core in a hollow cone swirl nozzle. The theoretical study is based on the numerical solution of conservation equations for mass and momentum along with the volume fraction of the liquid phase. An interface capturing method has been adopted in the numerical simulation of free surface flow in the nozzle. Experiments have been carried out with a number of nozzles fabricated in Perspex material. The air core diameter has been measured from photographs taken by a camera outside the nozzle. It has been observed that the shape of the fully developed air core in a conical swirl nozzle is cylindrical with a considerable bulging at the entrance to the orifice, while in the case of a conical nozzle without a finite length of orifice, the air core is uniform throughout the nozzle. The values of the air core diameter in the swirl chamber ( da1) and in the orifice ( da2) of a nozzle increase sharply with an increase in inlet Reynolds number ( Re) below 1.1 × 104, but become almost independent of Re above this (up to 1.7 × 104). The air core diameter, both in the swirl chamber and in the orifice, increases with an increase in the value of the ratio of orifice to swirl chamber diameter and the cone angle of the swirl chamber and with a decrease in the value of the ratio of entry port to swirl chamber diameter and the ratio of orifice length to swirl chamber diameter.

Initiation of air core in a simplex nozzle and the effects of operating and geometrical parameters on its shape and size

Experimental investigations have been carried out to recognize the phenomenon of initiation of air core in a simplex type swirl spray pressure nozzle and to determine the influences of nozzle geometry and nozzle flow on the size of the fully developed air core. It has been recognized that below a certain Reynolds number at inlet to the nozzle, liquid flows full through the nozzle without the formation of an air core, while, above a certain Reynolds number at inlet to the nozzle, the formation of a fully developed central air core of cylindrical shape takes place in the nozzle. A transition flow with the development of a central air core takes place within the nozzle in between the two limiting inlet Reynolds numbers. These two limiting Reynolds numbers Re L1 and Re L2 are found to be an inverse function of the ratio of orifice to swirl chamber diameter ( D o/ D s) and a direct function of the ratio of tangential entry port to swirl chamber diameter ( D p/ D s). It has been observed that the fully developed central air core is cylindrical in shape with a sudden bulging in diameter at the entrance to the orifice. The air core diameter in both converging and orifice sections of the nozzle increases with an increase in the inlet Reynolds number ( Re) at its lower range, while it becomes independent with Re at its higher range. The ratio of air core to orifice diameter (da 2/ D o) increases with an increase in D o/ D s or swirl chamber cone angle ( α), and a decrease in D p/ D s or L o/ D s (the ratio of the orifice length to swirl chamber diameter). The ratio of air core diameter in the orifice to air core diameter in the swirl chamber of the nozzle (da 2/da 1) is an inverse function of D o/ D s but a direct function of D p/ D s. Empirical relations of the ratios of air core to orifice diameter, da 1/ D o and da 2/ D o, with the pertinent dimensionless controlling parameters have been established.

Swirl atomizers operating at high water pressure

Swirl atomizers, producing hollow cone sprays, are used in many engineering applications and, for high supply pressures, they are used for air pumping, dust extraction, fire suppression and combustion. Swirl atomizers producing water sprays are here investigated experimentally to give information on atomizer performance at supply pressures up to 15.2 MPa. Some broad agreement of trends for discharge coefficient, drop diameter and spray angle is found with results obtained at lower supply pressure. Supply pressure is the most important parameter for determining the mean drop size, which is only weakly dependent on other features of the atomizer geometry. Information is presented on the effects of inlet port geometry and swirl chamber length and diameter and these show both discrepancies and agreements with published work at lower pressures. The observations indicate the existence and importance of turbulent flow inside these high velocity atomizer flows.

Mean drop sizes from pressure-swirl nozzles

A study of the factors governing the atomization process in pressure-swirl nozzles is presented. Extensive measurements of mean drop size are conducted on six simplex nozzles of different sizes and spray-cone angles. The liquids employed are water, diesel oil, and several blends of diesel oil with polybutene. These liquids provide a range of viscosity from 3 to 18 X 10~6 m2/s (3-18 cs), and a range of surface tension from 0.027 to 0.0734 kg/s2 (27-73.4 dyne/cm). The results are used to substantiate an equation for mean drop size derived from basic considerations of the hydrodynamic and aerodynamic processes that govern the atomization processes in pressureswirl nozzles. A very satisfactory correlation is demonstrated between predictions based on this equation and the actual measured values of mean drop size. Nomenclature A,B = constants, Eq. (16) Aa = air core area, m2 A0 = discharge orifice area, m2 Ap = swirl chamber port area, m2 Ds = swirl chamber diameter, m d0 = liquid orifice diameter, m m =mass flow rate, kg/s P = pressure, Pa AP = pressure differential, Pa Re = Reynolds number SMD = Sauter mean diameter, m t - film thickness in final orifice, m ts = liquid sheet thickness after exit from nozzle, m U = velocity, m/s We = Weber number X =Aa/A0 6 = spray cone half-angle, deg fj. = dynamic viscosity, kg/ms v = kinematic viscosity, m2/s p = density, kg/m3 a - surface tension, kg/s2 Subscripts A =air F = fuel L = liquid R = air relative to liquid

Film thickness measurements in a simplex swirl atomizer

The results of previous theoretical and experimental studies on the relationship between the liquid-film thickness produced at exit from pressure-swirl and airblast atomizers are reviewed. An electrical conductance method is used to measure the liquid-film thickness in the final orifice of a specially designed simplex atomizer when discharging water into air at normal atmospheric pressure. The results of these measurements are compared with various theoretical equations for predicting liquid-film thickness in this type of nozzle. Excellent agreement between theory and experiment is demonstrated for two equations, one of which is derived in this paper. Aa Ap A0 CD dp Ds dQ mL SMD t X PL 6 AP Nomenclature =air core area, m2 = total inlet ports area, m2 = discharge orifice area, m2 = discharge coefficient = inlet port diameter, m = swirl chamber diameter, m = discharge orifice diameter, m = flow number, [ = m/(APpL)Q-5 ] , m2 = liquid flow rate, kg/s = Sauter mean diameter, m = liquid-film thickness, m =Aa/A0 = liquid viscosity, kg/ms = liquid density, kg/m3 = spray cone half -angle, deg = total pressure drop across nozzle, Pa

Theoretical and experimental investigations on the coeffizient of discharge and spray cone angle of a swirl spray atomizing nozzle

An understanding of the relation between the important sprary characteristics of a swirl nozzle with its different geometrical dimensions forms the basis of a unified design procedure of the nozzles for any preassigned performance. The coefficient of discharge and spray cone angle are two of such important performance characteristics. In the present paper, an attempt has been made towards a theoretical and an experimental investigations into the effects of nozzle geometries and injection condition on the coefficient of discharge and spray cone angle. These two parameters have been theoretically evaluated through the analytical solution of hydrodynamics of flow inside the nozzle and finally their dependence with the nozzle dimensions, namely, the length and diameter of the swirl chamber, angle of the spin chamber and the orifice diameter along with the injection condition expressed as the Reynolds number at inlet to the nozzle have been established theoretically. A series of experimental investigations have also been carried out to support and compare the theoretical results. It has been recognized that within a definite range, an increase in Reynolds number Rei at inlet to the nozzle decreases the coefficient of discharge and increases the spray cone angle. Amongst the nozzle geometries, an increase in the orifice to swirl chamber diameter ratioD2/D1, spin chamber angle 2α or a decrease in swirl chamber length to diameter ratioL1/D1 decreases the coefficient of discharge and increases the spray cone angle.

Theoretical and experimental investigations on the formation of air core in a swirl spray atomizing nozzle

Theoretical and experimental studies have been made to investigate the variations of air core diameter, the most important hydrodynamic picture inside a swirl nozzle, with the pertinent guiding parameters like injection condition expressed as the Reynolds number at inlet to the nozzle and the geometrical dimensions of the nozzle, namely, the length and diameter of the swirl chamber, angle of spin chamber and the orifice diameter. The theoretical relations have been established through an approximated analytical solution of the hydrodynamics of flow of a viscous incompressible fluid in a swirl nozzle. A series of experiments have been carried out to support and compare the theoretical results. Finally, it has been recognized that for any nozzle, the air core diameter becomes a direct function of Reynolds number Re i at inlet to the nozzle only at its lower range and then remains constant. Amongst the nozzle geometrics, the ratio of orifice to swirl chamber diameter D 2/D 1 has got the most predominant effect on the air core diameter. An increase in the ratio of orifice to swirl chamber diameter D 2/D 1, and in the spin chamber angle 2α and a decrease in the swirl chamber length to diameter ratio L 1/D 1 increase the ratio of air core to orifice diameter and vice versa.

The flow characteristics of swirl (centrifugal) spray pressure nozzles with low viscosity liquids

AbstractA study has been made of the mechanics of flow of low viscosity liquids through swirl spray nozzles. Discharge coefficients and spray angles have been measured for a series of nozzles designed to systematically determine dimensional effects not predicted by frictionless theory, in particular the effect of the ratios of swirl chamber diameter to orifice diameter and of orifice length to orifice diameter. It was found that a unique relationship exists between discharge coefficient and spray angle dependent only upon the value of the orifice length/diameter ratio. This result has been explained on the basis of an ideal flow theory extended to take into account the frictional decay of the vortex motion. A general expression has been derived which permits correlation of the flow characteristics of nozzles covering a wide range of designs.