Nozzle Characteristics Research Articles

Investigation on Flow Characteristics and Performance Estimation of a Hybrid SVC Nozzle

Higher vector efficiency of fluidic thrust vectoring (FTV) technology results in less requirement on secondary flow mass, which helps to reduce the influence of secondary flow on the performance of an aero-engine. In the paper, a new concept of FTV, named as a hybrid shock vector control (SVC) nozzle, was proposed to promote the vector efficiency of a SVC nozzle. It adopts a rotatable valve with a secondary flow injection to enhance the jet penetration, so as to improve the vector performance. The flow characteristics of a hybrid SVC nozzle were investigated numerically by solving 2D RANS equations. The influence of secondary pressure ratio (SPR) and rotatable valve angle on vector performance were conducted. Then, the coupling performance of a hybrid SVC nozzle and an aero-engine was estimated, by using the approximate model of a hybrid SVC nozzle and the performance simulation model of an aero-engine. Results show that, a desirable vector efficiency of 2.96 º/ %-ω (the vector angle achieved by using secondary flow of 1% of primary flow) of a hybrid SVC nozzle was obtained. In the coupling progress, when a secondary flow of 5.3% of primary flow was extracted from fan exit to a hybrid SVC nozzle, a vector angle of 14.1°, and a vector efficiency of 2.91º/ %-ω were achieved. Meanwhile the thrust of the aero-engine thrust decreased by 5.6% and the specific fuel consumption (SFC) increased by 0.5%.

Spray Characteristics of Rotary Micro Sprinkler Nozzles Used in Orchard Pesticide Delivery

HighlightsDroplet sizes were determined for rotary micro sprinkler nozzles used in solid set canopy delivery systems.An empirical multiple-variable model was developed to predict volume median diameters in spray patterns.Sprinkler nozzles produced medium to coarse droplets to minimize pesticide drift in orchards and trellised systems.Droplet size information can be used to select optimal nozzles for either irrigation or pesticide delivery systems.Abstract. Rotary micro sprinkler nozzles can be used for both irrigation and pesticide applications in orchard systems, but little to no information is available on their droplet size distributions. In this study, the droplet size distributions were investigated and described for rotary micro sprinkler nozzles with five different orifice diameters. A particle/droplet laser image analysis system was used to measure droplet spectra at two pressures (207 and 310 kPa) and two radial distances (0.25 and 0.85 m) from the sprinkler nozzle center. Nozzle orifice sizes, rotational speeds, and flow rates were also measured. Droplet sizes varied with the orifice size, operating pressure, and sampling location. Spiral-shaped spray patterns formed due to the spinning discharge port, within which droplet densities varied with location, orifice diameter, and operating pressure. The volume medium diameters (Dv0.5) for green-black, orange-blue, black-black, blue-black, and red-gray nozzles were respectively 317, 338, 379, 352, and 218 µm at 207 kPa and 283, 250, 283, 270, and 222 µm at 310 kPa. An empirical multiple-variable regression model was developed to predict Dv0.5 in the spray patterns discharged from the nozzles. Test results demonstrated that the rotary micro sprinkler nozzles produced medium to coarse droplets that could be used to minimize spray drift while maintaining efficacy in orchard pesticide applications. Keywords: Chemical application, Droplet size, Irrigation, Rotary nozzle, Spray drift reduction.

Study on atomization particle size characteristics of two-phase flow nozzle

Nozzle spray atomization is widely used in industrial and agricultural production processes and is a very complicated physical change. The spray atomization of the nozzle is a process in which the droplets are continuously broken into finer particles under the action of force, in order to study the effect of nozzle atomization, that is, droplet size distribution characteristics. The experimental average mathematical model of droplet size distribution was established by introducing Sauter Mean Diameter (SMD). The droplet size distribution in the atomization field of the nozzle is studied by simulation. In the experimental study, the high-speed camera, external mixing air atomizing nozzle platform experimental device and image processing were used, and the atomization field was divided into multiple observation areas. Through the measurement of several local observation areas, the droplet size distribution of the whole atomization field is constructed. It provides a reference for the study of the atomization field of the nozzle and a basis for the intuitive understanding of the droplet size distribution in the atomization field of the nozzle. The effective atomization area of the nozzle atomization was selected to study the influence of the liquid flow rate, the liquid temperature and the nozzle pressure on the atomized particle size distribution of the externally mixed atomizing nozzle. The internal law is obtained, which provides a basis and reference for effectively controlling the atomization effect in the atomization field.

Effect of design parameters on flow characteristics of an aerodynamic swirl nozzle

Effect of design parameters on flow characteristics of an aerodynamic swirl nozzle

Effect of design parameters on flow characteristics of an aerodynamic swirl nozzle

This study numerically investigates the flow characteristics for the effect of various nozzle design variables, such as tangential inlet number, length of the nozzle and nozzle shape of an incompressible turbulent swirl air jet. Axial-plus-tangential flow based swirling nozzle is solved using finite volume method, where turbulence is approximated by Shear Stress Transport (SST) k-ω model. The results show that swirl into the flow results in a creation of a forced vortex. The axial velocity and its peak increase with the number of ports, and the tangential velocity is the maximum after the tangential flow is imparted. The static pressure and turbulent kinetic energy are significantly influenced by the number of tangential inlets. The most uniform turbulence is predicted for the tapered cone shape, while the strongest turbulence is observed for the curved shape with the expense of losing some uniformity near the nozzle wall.

Improving the efficiency of humidifiers based on regular nozzles for thermal treatment of air in entomological production facilities

Annotation Purpose. Investigate the possibility of ensuring a high level of efficiency of humidifiers in entomological production facilities that use out-of-circulation water cycle, while minimizing (or no) non-production water consumption and reducing energy consumption for the process, given the high dust content in indoor air. Methods. Using the requirements for materials for the manufacture of regular nozzles of film humidifiers in entomological production, ways to increase their efficiency are substantiated. The aerodynamic and kinetic characteristics of nozzles made of various materials PET (Ukraine), GLASdek3 (Sweden), PVC (Netherlands) were experimentally determined. Results. New types of regular nozzles RN are proposed, formed by sheets that have a high degree of wettability due to the applied materials or special surface geometry, and provide high efficiency of the wetting process. Conclusions 1. The study of the aerodynamic characteristics of nozzles made of various materials showed that The study of the aerodynamic characteristics of nozzles made of various materials showed that GLASdek3 and PET nozzles have advantages in terms of air resistance, for which aerodynamic drag in the operating range of airflow rates of 1.5...4 m/s is 75...450 Pa, which is 2–4 times less than for PVC nozzles. 2. At the same values of the degree of efficiency for the GLASdek3 and PET nozzles are characterized by lower values of specific energy consumption. The energy efficiency of these nozzles is approximately 1.5 times higher than that of PVC nozzles. 3. Economic analysis proved the feasibility of using nozzles made of PET sheets of domestic manufacturers, which are characterized by lower cost than modules of GLASdek3 nozzles with similar characteristics. 4. It has been established that miplast acts as a material for film humidifiers in terms of efficiency on a par with GLASdek3 and PET, however, it is not recommended to use it to create thermal humidity parameters in entomological production due to the porosity of the structure and the inability to clean it from dust. Keywords: entomological production, thermo-moisture treatment of air, humidification, contact devices, regular nozzles.

Effect of Swirl Plates on Volumetric Discharge Rate and Spray Characteristics of Hollow Cone Nozzles

The aim of the study is to determine the effect of orifice diameter, swirl plate and spray pressure on the volumetric flow, discharge coefficient and some spray characteristics of hollow cone nozzles. In the trials, five nozzle discs with 1,0, 1,2, 1,6, 2,0 and 2,4 millimetres orifice diameters and three polyacetal materials with 2 or 3 slots and one stainless steel with 2-slots swirl plate were used. Spray application were made at spray pressures of 2, 4, 6, 8 and 12 bar. The highest discharge rate at constant pressure was obtained with stainless steel and the lowest blue swirl plates. Although the number of slots was different, the effect of brown and yellow swirl plates on volumetric discharge rate variation was statistically insignificant. The discharge coefficient decreased as the diameter of the nozzle orifice increased. Accordingly, the average discharge coefficient for the 1,0 mm, 1,2, 1,6, 2,0 and 2,4 mm diameter nozzle discs was 0,411, 0,362, 0,285, 0,236 and 0.201, respectively. It was estimated that the droplet diameter in the range of 2-12 bar in the hollow cone nozzles varied between 76,3-219,0 μm and it was determined that mostly very fine and partially fine and medium sized droplets were produced.

Nozzle Flow Characteristics and Simulation of Pesticide Spraying Drone

Nozzle Flow Characteristics and Simulation of Pesticide Spraying Drone

Experimental study on flashing spray characteristics of pressure swirl nozzle with ethanol solution

Flashing spray has the potential to enhance the performance of aero-engine combustor, compared with conventional spray. In this study, the kerosene was replaced by ethanol solution, the influence of flashing degree of ethanol on spray profile, velocity distribution and droplet size distribution was investigated based on the ratio of the ambient pressure to saturation pressure using the particle image velocity and laser particle size analyzer. Results indicated that when the ratio of ambient pressure to saturation pressure was reduced, the micro-explosion effect was intensified, spray cone angle was first increased and then decreased, and the radial velocity peak and velocity gradient were improved. The downtrend of sauter mean diameter became faster and it was dominated by the ratio of ambient pressure to saturation pressure, the cumulative distribution ratio and frequency distribution were changed, small droplets produced by the micro-explosion effect mainly existed in 16% of the total droplet volume. Moreover, the formation mechanism of recirculation zone upstream of the spray field was proposed, and the difference of formation and breakup of liquid sheet between conventional spray and flashing spray was analyzed. These results provide insightful information for understanding flashing spray characteristics with pressure swirl nozzle.

Experimental Study on Spray Breakup in Turbulent Atomization Using a Spiral Nozzle

Spiral nozzles are widely used in wet scrubbers to form an appropriate spray pattern to capture the polluting gas/particulate matterwith the highest possible efficiency. Despite this fact, and a fact that it is a nozzle with a very atypical spray pattern (a full cone consisting of three concentric hollow cones), very limited amount of studies have been done so far on characterization of this type of nozzle. This work reports preliminary results on the spray characteristics of a spiral nozzle used for gas absorption processes. First, we experimentally measured the pressure impact footprint of the spray generated. Then effective spray angles were evaluated from the photographs of the spray and using the pressure impact footprint records via Archimedean spiral equation. Using the classical photography, areas of primary and secondary atomization were determined together with the droplet size distribution, which were further approximated using selected distribution functions. Radial and tangential spray velocity of droplets were assessed using the laser Doppler anemometry. The results show atypical behavior compared to different types of nozzles. In the investigated measurement range, the droplet-size distribution showed higher droplet diameters (about 1 mm) compared to, for example, air assisted atomizers. It was similar for the radial velocity, which was conversely lower (max velocity of about 8 m/s) compared to, for example, effervescent atomizers, which can produce droplets with a velocity of tens to hundreds m/s. On the contrary, spray angle ranged from 58° and 111° for the inner small and large cone, respectively, to 152° for the upper cone, and in the measured range was independent of the inlet pressure of liquid at the nozzle orifice.

Effect of Nozzle Exit Wear on the Fluid Flow Characteristics of Supersonic Oxygen Lance

Supersonic jet characteristics of oxygen lance nozzles have a significant influence on smelting; however, presently, little research has been carried out to investigate the influence of wear on the jet characteristics at the nozzle exit. A numerical model and aerodynamic testing platform were developed to analyze supersonic jet characteristics under different inlet pressures and wear levels at the nozzle exit. The numerical model was first validated by comparing the numerical results with the measured data of the aerodynamic testing experiment. Then, the effects of the inlet pressure and nozzle exit wear on the jet velocity and degree of aggregation were studied. An increase in the nozzle inlet pressure is conducive to an increase in jet velocity but also causes earlier jet convergence. An increase in the nozzle exit wear results in the faster attenuation of jet velocity, not only reducing the jet velocity but also leading to an earlier convergence point for each jet. The results of this study can provide theoretical support for the design of an oxygen lance nozzle and process optimization of smelting in industrial application.

Prediction model for the water jet falling point in fire extinguishing based on a GA-BP neural network.

Past research on the process of extinguishing a fire typically used a traditional linear water jet falling point model and the results ignored external factors, such as environmental conditions and the status of the fire engine, even though the water jet falling point location prediction was often associated with these parameters and showed a nonlinear relationship. This paper constructed a BP (Back Propagation) neural network model. The fire gun nozzle characteristics were included as model inputs, and the water discharge point coordinates were the model outputs; thus, the model could precisely predict the water discharge point with small error and high precision to determine an accurate firing position and allow for the timely adjustment of the spray gun. To improve the slow convergence and local optimality problems of the BP neural network (BPNN), this paper further used a genetic algorithm to optimize the BPNN (GA-BPNN). The BPNN can be used to optimize the weights in the network to train them for global optimization. A genetic algorithm was introduced into the neural network approach, and the water jet landing prediction model was further improved. The simulation results showed that the prediction accuracy of the GA-BP model was better than that of the BPNN alone. The established model can accurately predict the location of the water jet, making the prediction results more useful for firefighters.

Numerical Investigation of a High-Pressure Submerged Jet Using a Cavitation Model Considering Effects of Shear Stress

In the current research, a high-pressure submerged cavitation jet is investigated numerically. A cavitation model is created considering the effect of shear stress on cavitation formation. As such, this model is developed to predict the cavitation jet, and then the numerical results are validated by high-speed photography experiment. The turbulence viscosity of the renormalization group (RNG) k-ε turbulence model is used to provide a flow field for the cavitation model. Furthermore, this model is modified using a filter-based density correction model (FBDCM). The characteristics of the convergent-divergent cavitation nozzle are investigated in detail using the current CFD simulation method. It is found that shear stress plays an important role in the cavitation formation in the high-pressure submerged jet. In the result predicted by the Zwart-Gerber-Belamri (ZGB) cavitation model, where critical static pressure is used for the threshold of cavitation inception, the cavitation bubble only appears at the nozzle outlet and the length of the cavity is much shorter than the actual length captured by the high-speed photography experiment. When the shear stress term is added to the critical pressure, the length of the predicted cavity is close to the experimental result and three phenomena of the jet are captured, namely, growth, shedding, and collapsing, which agrees well with the experimental high-speed image. According to the orthogonal analysis based on the simulation result, when the jet power is unchanged, the main geometry parameter of the divergent-convergent nozzle that affects the jet performance is the divergent angle. For the nozzle with three different divergent angles of 40°, 60°, and 80°, the one with the medium angle generates the most intensive cavitation cloud, while the small one shows the weakest cavitation performance. The obtained simulation result is confirmed by cavitation erosion tests of the Al1060 plate using these three nozzles.

Flow Characteristics of Parabolic Nozzle by Changing the Shape of Nozzle Exit

This paper deals with parabolic nozzles which can be used in aerospace applications. Parabolic nozzles are mechanical devices which produces mechanical energy by converting the thermal and pressure energy produced as a result of combustion. This project aims at providing the flow characteristics of parabolic nozzle by changing the shape of the exit area. The analyses were further extended by changing the pressure values. The analysis processes were carried out using Computational Fluid Dynamics software ANSYS CFX.

Numerical Simulation of Internal Flow and External Atomization in Pressure Swirl Nozzle

A computational fluid dynamics (CFD) study is carried out on the internal flow characteristics of pressure swirl nozzle and the breakup of external liquid film outside the nozzle. The numerical simulation of two-phase flow shows the unsteady characteristics inside the nozzle and the breaking mechanism of liquid film outside the nozzle. In the nozzle, the numerical simulation reveals the three-dimensional velocity distribution in the swirl chamber and the nozzle outlet. At the same time, the study shows that the breakup of liquid film is caused by the circumferential disturbance wave produced by R-T instability under the condition of 0.7 MPa inlet pressure. The influence of inflow characteristics on the instability of liquid film is pointed out.

Research on the Dynamic Characteristics of the High Air Speed Nozzle in Isentropic Flow

The application of microsatellites has been development with the continuous expansion of space missions in resents years. The microsatellites have several characteristics such as light weight, small size and low cost. The platform flotation table is one of the simulation ways on the ground. With the continuous development of space technology, satellite ground simulation platform flotation table as a key technology which attracts lots of researchers. In this paper, the highspeed nozzle has been analyzed based on the research of Laval nozzle. The state of shock waves can be researched by the Laval nozzle and the air speed from the nozzle can be calculated. The flow field of the high speed nozzle has been simulation by the FLUENT software. The nozzle mode has been built by the GAMBIT and the model is meshed in structured grid. The simulation result shows that the air in the nozzle has many speeds in different place. The stable speeds are 390 m/s and 150m/s in the larynx and trailing end position.The maximum are reached into the nozzle and the speed is 578m/s, which is deviated from the theoretical analysis. At the constant pressure of 4 bar, the mass of nozzle flow is 0.000318758 kg/s. The mass of outlet flow is 0.000318798 kg/s, and the calculation error is 10-8. The thrust of the nozzle is also stable at 3ms, and its stability value is 50.1 mN. The maximum force of the outlet is 176 mN before the nozzle reaches stability. The simulation result can guided for the nozzle design and itis more significance for the high precision control and measurement of nozzles.

Experimental investigation of flow separation in a planar convergent-divergent nozzle

Under the conditions of nozzle pressure ratio (NPR) of 2.79, 2.82 and 2.95, the flow field was observed by dynamic pressure measurement and focusing schlieren technique, and the flow separation characteristics of a planar convergent-divergent nozzle were studied. The results show that as the NPR increases, the nozzle flow structure changes from asymmetric to a symmetrical configuration. Under the condition of NPR=2.79, the flow in the nozzle goes obviously downward to the bottom wall of the nozzle, and the restricted shock separation (RSS) occurs on the bottom wall; under the condition of NPR=2.82 and NPR=2.95, the flow in the nozzle tends to be symmetrical, RSS appears on both the top and bottom walls. Based on spectrum analysis, it is found that there is obvious low-frequency oscillation characteristics near the separation point.

Large Eddy Simulation of Two-Phase Flow Pattern and Transformation Characteristics of Flow Mixing Nozzle

ABSTRACTThe two-phase flow pattern of a flow mixing nozzle plays an important role in jet breakup and atomization. However, the flow pattern of this nozzle and its transformation characteristics are still unclear. A diesel-air injection simulation model of a flow mixing nozzle is established. Then the two-phase flow pattern and transformation characteristics of the flow mixing nozzle is studied using a numerical simulation method. The effect of the air-diesel velocity ratio, ratio of the distance between the tube orifice and nozzle hole and the tube diameter (H/D), and the diesel inlet velocity was studied in terms of the jet breakup diameter (jet diameter at the breakup position) and jet breakup length (length of the diesel jet from the breakup position to the nozzle outlet). The results show that the jet breakup diameter decreases with the decrease in H/D or the increase in the air-diesel velocity ratio and diesel inlet velocity. The jet breakup length increases first and then decreases with the increase in H/D and air-diesel velocity ratio; the trend of the diesel inlet velocity is complicated. In addition, a change in the working conditions also causes some morphological changes that cannot be quantitatively analyzed in the diesel-air flow pattern. The transition characteristics of the flow pattern are analyzed, and it is found that the main reason for the change in the flow pattern is the change in the inertial force of the air, surface tension force, and viscous force of diesel (non-dimensional Reynolds number and Weber number describe the transition characteristics in this paper). The surface tension force of diesel decreases and the viscous force of diesel and inertial force of air increase when the air-diesel velocity ratio increases or H/D decreases. However, the effects of the diesel surface tension force and viscous force effect are much smaller than that of the air inertial force, which changes the diesel-air flow pattern from a drop pattern to a vibration jet pattern, broken jet pattern, and then a chaotic jet pattern.

Numerical investigation on behaviors of interlaced jets and their interaction with bath in BOF steelmaking

The jet behavior of interlaced multiple nozzles and the impingement of multiple jets onto the surface of the molten metal bath in a steelmaking converter are numerically studied. The interlaced jet hydrodynamic behaviors such as jet profile, coalescence characteristics, and dynamic parameter distributions penetration depth and impact area, as well as time-dependent evolution of liquid bath are discussed. The results are compared with traditional nozzles. It is found that the single nozzle characteristics of staggered jet are similar to those of traditional jet. However, two sets of staggered nozzles with different flow rate and inclination angle having a less disturbance flows, cause weaker coalescence of the jets and larger area surrounded by isovelocity in the molten pool. In the initial stage of the interaction between the interlaced nozzles and the molten pool, the “low stirring zone” is more likely to concentrate in the outer side near the furnace wall than in the center of the molten pool. Two cavities, one deep and one shallow, are formed on the bath surface. The average depth of the two cavities is similar to traditional nozzles, and the diameter of the cavity is increased by about 11% compared to traditional nozzles.

Experimental study on the two-phase flow pattern and transformation characteristics of a flow mixing nozzle under a moderate flow rate

A flow mixing nozzle can produce satisfactory atomization for heavy oil. However, the study of the internal flow pattern of this nozzle, along with the spray morphology and its transformation, is currently limited to a low flow rate for the two-phase inlet. A flow mixing nozzle with a moderate inlet flow rate and various nozzle structures (H/D) was experimentally studied using a self-designed flow mixing nozzle and a self- constructed experimental platform, as described in this paper. The results demonstrate that at a moderate two-phase inlet flow rate, a clear cone is observed inside the nozzle that can be described by the cone angle and the dimensionless cone area. In short, as air inlet flow rate increases, the cone volume decreases, the jet atomization effect is enhanced, the distribution range narrows, the flow pattern changes to flow blurring, and the variation trend is the opposite of that when the water inlet flow rate is increased. An analysis of the experimental results demonstrate that the flow pattern and spray morphology of the flow mixing nozzle under a moderate inlet flow rate are determined by the inertial force of air and the inertial force and surface tension force of water. When the air flow rate is increased, the inertial force is enhanced, and the cone radial concavity is strengthened; or, the cone disappears. At this time, the spray morphology is mainly expressed as atomization. When the water flow rate increases, the water inertial force increases, and the cone changes to a radial protrusion. The spray morphology is mainly expressed as a jet or breakup.