Nozzle Characteristics Research Articles

针对精准施药的平扇形喷嘴低压雾化特性

At present, the theory of precision pesticide application in agriculture and forestry has some shortcomings. Therefore, the Phase Doppler Interferometer (PDI) was used to establish the atomization model of three common brands (Lechler, Teejet and Feizhuo) flat fan nozzles in near fog field (0.3-0.5m) at low pressure (0.20-0.30mPa). The results show that the average absolute errors of droplet velocity of three brands of nozzles are 0.629, 0.521 and 0.684 m/s respectively, and the relative errors are 9.22, 9.60 and 11.89%, respectively. The average absolute errors of theoretical data of droplet size are 17.821, 13.801 and 22.140 μ m, and the relative errors are 8.40, 5.82 and 11.67%, respectively. The experimental theoretical model has high reliability. In addition, the results show that the droplet velocity and particle size increase with the increase of the equivalent diameter of the nozzle outlet. With the increase of spray angle, droplet velocity and particle size decrease gradually, and the rate of velocity decrease gradually. The research results are of great significance to further analyse the atomization characteristics of flat fan nozzle and guide the precise application of pesticide.

Design and thermo-structural analysis of 2D exhaust nozzle with multiple composite layers

The IR(Infrared) signature generated by hot sections of the aircraft results in severely reducing aircraft survivability during the mission because this signature increases potential to be traced by IR detection system. This article deals with the novel 2D exhaust nozzle for reducing IR signature, and design process by thermo-structural analysis for satisfying thermal and structural requirements. The novel 2D exhaust nozzle is adopted as multiple composite layers with variable elliptical cross-sections for dispersing high temperature core gas flow and enhancing mixing performance with bypass air flows. Also, this study defines 1D thermo-structural model based analytical method for calculating initial performances of the 2D exhaust nozzle. In addition, initial design parameters are firstly determined by the proposed 1D thermo-structural model. Furthermore, detailed thermo-structural characteristics of the 2D exhaust nozzle are investigated by the finite element method (ABAQUS). Based on the database, the minimum thickness of the insulator layer can be determined to maintain structural rigidity and suppress increase of temperature at the outermost surface of the nozzle. Consequently, we review thermo-structural stability of the 2D exhaust nozzle by comparison of the finite element analysis and engine application tests.

Flow and aeroacoustic characteristics evaluation of microjet noise reduction concept in the nozzle design for minimum quantity lubrication

Minimum quantity lubrication (MQL) is an efficient and sustainable technology, which has been considered to be an option of conventional flood cutting process. Even though MQL provides green solution for the cooling and lubrication function during machining, it brings about unendurable aeroacoustic jet noise from the high velocity spray. The acoustic pollution has seriously affected the operator's health and efficiency so that it should be paid much attention to. In this paper, with the utilization of microjets noise reduction concept, a noise cancellation accessory for MQL nozzle has been developed. The flow field and aeroacoustic characteristics of the original nozzle and microjets have been investigated numerically to help understand the noise reduction mechanism. Variables including the main jet flow rates, the air flow rate ratios of the microjets to the main jet and the measuring azimuths on noise directivities and sound pressure level (SPL) have been analysed. It has found the flow ratio is a critical parameter, which has an optimal value in regard to the main jet flux. The simulation results have been partially verified through OASPL measurement. The overall aeroacoustic noise reduction varied from 0.70 to 4.88 dB has been observed experimentally. Finally, the noise cancellation mechanism has been discussed from the flow field and the frequency characteristics points of view. The shrinking effect of microjet injection at appropriate air flow ratios has significantly narrowed the distribution of the turbulent intensity and reduced the SPL of low and medium frequency while increased that of the high frequency in specific directions. The overall amplitude of OASPL has been reduced. However, inappropriate air flow ratios will generate additional jet noise.

Analysis of diesel engine injector nozzle spray characteristics fueled with residual fuel oil

Experimental analysis on the spray characteristics of a diesel engine injector nozzle fueled with Residual Fuel Oil (RFO) was carried out in this study. To achieve this, the fuel was characterized to determine its physicochemical properties, and an experimental set up was designed to visualize and capture the spray pattern of the fuel. The images obtained were processed and analysed using Image J software to determine the spray length, spray cone angle, spray area, spray volume, and spray velocity values of the fuel. Experimental results obtained agree with validation models and reveal that spray parameter values of RFO are higher than those of diesel fuel. The values of spray parameters of RFO such as 456mm spray length, 2.85mm Sauter Mean Diameter (SMD) and the low spray cone angle of 12.69°, led to a higher spray volume causing the engine to run on a rich mixture after initial start-up conditions. This would create such challenges as reduction in power and clogging of injector nozzle tip due to an increase in carbon deposits. Regression models generated reveal that these challenges could be eliminated when the spray parameters run on optimal values of 256mm, 6.41cm2, 16.18cm3, 0.96 mm/s and 13.59° for the spray length, spray area, spray volume, spray velocity and the spray angle respectively. These optimal values were obtained when the engine fuel injection time was set to 500μs while running on fuel of viscosity 4.305 mPa.s and temperature of 48 °C.

The Use of Air Induction Nozzles for Application of Fertilizing Preparations Containing Beneficial Microorganisms

The work presents the structure and characteristics of field sprayer nozzles, as well as their impact on the survival of beneficial organisms in the selected fertilizing preparations. EŻK and EŻKT nozzles, (EŻK and EŻKT are trade names of single and twin jet air induction nozzles, respectively), that are available on the market have shown low efficiency in the discussed characteristics. Survival of microorganisms under initial conditions at 13.6 × 106 cfu/mL and pressure of 0 MPa, under critical conditions dropped to 1.7 × 106 cfu/mL for EŻK02 and 1.2 × 106 cfu/mL for EŻKT02, in both variants at a pressure of 0.5 MPa. When increasing the flow rate of the components, i.e., the size of the outlet orifices, it was observed that the survival of microorganisms increased by about 11.3% compared to the previously tested component. This resulted from the negative impact of the following: the pressure generated by the application device, number of outlet orifices, and size of an outlet orifice. The results of survival of microorganisms are given in the colony-forming unit (CFU). In addition to providing guidelines useful in the creation of a prototype sprayer intended for use in the application of microbiological preparations, the presented characteristics are a source of information for the end user as regards the proper conditions for the application of these preparations.

Research on erosion characteristics of a novel cavitation nozzle under nonsubmerged condition

When a cavitating jet enters the atmosphere directly, its cavitating effect weakens rapidly, and the erosion energy it produces cannot be fully utilized. Regarding the problem that existing cavitation nozzles are only used in submerged condition, methods to improve the erosion ability of cavitation jets under nonsubmerged condition are studied. The nozzle is visually simulated using Fluent software, and the results show that the dynamic submerged environment at the outlet effectively expands the nearby low-pressure cavitation area. The enhancement effect of the annular cavitation nozzle on the jet cavitation effect in the atmosphere domain is verified by measuring the impact force curve of the jet and through erosion tests on brass surface. Cleaning and derusting tests show that the annular cavitation nozzle has stronger derusting ability than the high-pressure nozzle under nonsubmerged condition and under the same pressure, demonstrating that the cleaning and derusting effect mainly comes from the collapse of cavitation bubbles.

Influence of orifice geometry on atomization characteristics of pressure swirl atomizer.

The spray characteristics of the pressure swirl nozzle are experimentally studied using particle dynamics analysis (PDA) and high-speed photography system in this paper, specifically focusing on the dependence of geometrical dimensions of orifice on the spray SMD, velocity magnitude and droplet distribution, and the spray cone angle. It is indicated that the increase of orifice diameter makes the initial swirling velocity lower and the spray liquid film thicker. When the spray cone is fully expanded, the flow rate of 900 μm orifice diameter nozzle increases by 30-40% and the SMD of 900 μm orifice diameter nozzle increases by 8.5% compared with that of 700 μm orifice diameter nozzle. According to the experimental conditions, the relationship between Re and spray angle was calculated as θ = 29.97*Re0.087, ignoring the factors that had little influence on spray angle. The decrease of the orifice length makes the distance of gas-medium shearing action shorten so that thinner oil film near wall cannot be formed by the extrusion of air core, leading to the swirling intensity reducing and the suction effect weakened. The spray cone angle of the 450 μm orifice length atomizer is about 5° smaller than the nozzle of 500 μm orifice length, and more small SMD droplets are not sucked, resulting in the distribution range of spray SMD declining.

Numerical and experimental investigation of throttleable hybrid rocket motor with aerospike nozzle

Hybrid rocket motors (HRMs) easily achieve variable thrust by changing oxidizer mass flow rate. This paper represents numerical and experimental studies on the throttleable HRM with aerospike nozzle, which can enhance the performances of the throttleable HRM theoretically. By comparing the performance of the throttleable HRM with the aerospike nozzle and that with the de Laval nozzle, the characteristics of the aerospike nozzle applied to the throttleable HRM are explored. Both numerical and experimental investigations are conducted. In the simulation part, characteristic velocity, combustion efficiency, thrust coefficient and specific impulse of the HRM with the two types of nozzles at different oxidizer mass flow rate are obtained. Comparing with the HRM with the de Laval nozzle, the HRM with the aerospike nozzle can improve specific impulse by about 8.9%∼23.4% when the working pressure ratio is lower than the design pressure ratio. The combustion efficiency of the throttleable HRM with the aerospike nozzle is 3.9%∼8.6% higher than that with the de Laval nozzle because of the core structure of the aerospike nozzle. When the oxidizer mass flow rate is 50 g/s, the thrust coefficient of the aerospike nozzle is increased by 12.3% relative to that of the de Laval nozzle which flow separation occurs in. The corresponding firing tests are performed by the lab-scale motor with 90% hydrogen peroxide (HP) and polyethylene (PE) grain. The numerical and experimental results agree well. The combination of the throttleable HRM and the aerospike nozzle has the advantages to improve the performance of HRMs.

Effects of the physical properties of fuel on spray characteristics from a gas turbine nozzle

Abstract In a gas turbine combustion system, droplet distribution in the combustor directly affects the combustion process. Fuel droplet size and droplet velocity determine the fuel droplet distribution in the combustor. The present study aims to investigate effects of physical properties on spray characteristics using computational fluid dynamics (CFD) analysis. Spray modeling was performed to analyze the spray characteristics for different fuel physical properties. The hollow cone spray of a gas turbine nozzle was modeled using a LISA (Linearized Instability Sheet Atomization)-TAB(Taylor Analogy Breakup) model with commercial CFD code called, ANSYS Fluent 16.2. The model was validated against the experimental results, which were obtained by PDPA (Phase Doppler Particle Analyzer) and spray tomography. Based on this spray model, the effect of fuel physical properties on spray characteristics were determined. In addition, because the spray patterns differed various injection fluids, the spray characteristics of the gas turbine nozzle with various injection fluids were considered from the perspective of fuel physical properties. It was found that higher density, viscosity and surface tension delayed the atomization process and that density and surface tension have a more significant effect on spray atomization, than viscosity in the catastrophic breakup regime.

Computational study of nozzle spray-line distribution effects on stratified mixture formation, combustion and emissions of a high compression ratio DISI methanol engine under lean-burn condition

In this paper, five different spray-line distribution nozzles were designed to evaluate the effect of the nozzle spray-line distribution on stratified-charge combustion of methanol engine. Nozzle spray-line distribution characteristics, the stratified mixture formation, combustion and emissions of a high compression ratio direct-injection spark-ignition methanol engine for different spray-line distribution nozzles under lean-burn condition were numerically simulated. Simulation results showed that a non-uniform spray-line distribution nozzle of a 10-hole × 0.30 mm was conducive to form an ideal stratified mixture and obtain better combustion and engine performance. The maximum in-cylinder pressure of nozzle A was approximately 50.5% higher than that of nozzle E. The ignition delay and combustion duration of nozzle A were approximately both 20% lower than nozzle E. Nozzle A had lower unburned methanol, CO and soot emissions. The nozzle order of the highest NO emission was: A ≫ B > C > D > E. NO emission of nozzle A was approximately 13.6 times higher than that of nozzle E. According to the combustion and emission performance tradeoff, the nozzle order was: A > B > D > C > E. Nozzle A was preferred for actual spark ignition methanol engine applications.

Flow and atomization characteristics of a twin-fluid nozzle with internal swirling and self-priming effects

A twin-fluid nozzle was proposed for low-pressure atomization. The nozzle is featured by swirling air flows in the mixing chamber. Liquid medium is thereby inhaled due to the pressure difference. An experimental work was performed to investigate the atomization performance of the nozzle and the hydrogen peroxide solution served as the liquid medium. Droplet size and droplet velocity were measured. Effects of the diameter of the air-injection orifice and the air-injection pressure were investigated. The results show that small droplet size is achieved with the proposed nozzle. As the spray develops, Sauter mean diameter (SMD) of the droplets decreases first and then increases, irrespective of the variation of the air-injection orifice diameter and the air-injection pressure. Overall SMD varies inversely with the air-injection orifice diameter and air-injection pressure. Near the nozzle, cross-sectional velocity distribution exhibits a peak-valley pattern, which is replaced with uniformized velocity distributions away from the nozzle. Similarity of cross-sectional radial velocity distribution at different air pressures is evidenced. Furthermore, the correlation between droplet size and droplet velocity is established.

Atomization characteristics of a fan air-assisted nozzle used for coal mine dust removal: an experimental study

ABSTRACT This article focuses on the atomization characteristics of fan air-assisted nozzles, which is important in the emerging process of dust removal via air-assisted nozzles in underground coal mines. An experimental study on atomization characteristics of a fan air-assisted nozzle was conducted using a custom-built air-assisted spray system. The results reveal that the volume flow rate of the medium, i.e., either water or air, showed a negative exponentially increasing trend as itself pressure increasing and showed a linearly decreasing trend as the other pressure increasing. The drop size distribution met the Rosin-Rammler function. When the air pressure was 0.5 MPa, the drop distribution moved right, and the uniformity coefficient of the distribution fell as the water pressure increased from 0.1 MPa to 0.9 MPa; the drop distribution moved left and the uniformity coefficient raised as the water pressure increased from 0.9 MPa to 1.0 MPa. When water pressure was 0.5 MPa, the drop distribution moved left, and the uniformity coefficient fell as the air pressure increased. The drop size grew downstream; the growth speed was proportional to droplet density and water volume fraction and inversely proportional to drop size. The drop size first tended to increase then showed a decreasing trend as the water pressure increased; the value of the cutoff point increased as the water pressure increased. The drop size decreased as the air pressure increased.

Spillback nozzle characterization using pulsating LED shadowgraphy

The atomization characteristics of a commercial spillback hydraulic nozzle were investigated in terms of droplet sizes, velocities, trajectories and spray angles. To replicate the fuel spray of a commercial auxiliary marine boiler, an experimental setup was designed and used to atomize water-glycerol solutions with various viscosities. Droplet size, velocity, position and shape were obtained with a novel pulsating LED backlight imaging system that employs a CCD camera to capture pairs of frames with a delay as short as 1 μs from one another. The overall spray characteristics of the nozzle and distributions for droplet size and velocity were examined for the operating conditions currently used in the burner and by varying three parameters: pressure drop, flow rate through the nozzle and liquid viscosity. Results include droplet size and velocity distributions in different spray regions, a description of the influence of each varying parameter on global indexes such as the Sauter Mean Diameter and a comparison with traditional correlations for pressure swirl nozzles.

English

English

Ablation characteristics of rocket nozzle using HfC-SiC refractory ceramic composite

Modern hybrid rockets are susceptible to the highly ablative environment in which they operate, as introducing an adequate cooling system has so far been a challenge. Ablative material has been widely adopted for use in hybrid rockets, which can only survive for the limited operation time. The use of ablative materials such as pyrolytic composite or graphite is advantageous for use in a simple system in an uncooled state. However, ablation causes severe enlarging in the nozzle throat area and a significant drop in the pressure during operation. Recently, Ultra High-Temperature Ceramics (UHTCs) have been noted as superior in terms of ablation and oxidation resistance. The most promising HfC-SiC composite ceramic has demonstrated an enhanced performance for thermal and mechanical properties. In this study, an HfC-SiC composite was embedded in the graphite casing as a nozzle insert throat to analyze the feasibility of its application in rockets. An experimental analysis of the ablation in the HfC-SiC was carried out with a 250 N scale hybrid thruster using High Test Peroxide (HTP) and High-Density Polyethylene. The hot-fire condition was set to above 30 bar for 25 s combustion, with the purpose of producing significant erosion on the nozzle materials. The graphite nozzle of the same shape was also tested under the same experimental conditions for comparison of the erosion. The hot-fire test with the HfC-SiC insert resulted in a stable rocket performance, with improvements to the chamber pressure and the thrust, whereas the combustion performance varied undesirably in the test using the graphite nozzle due to ablation. The rate of ablation in the throat was significantly reduced to 15.81 μm/s using HfC-SiC, which is 46.5% of the erosion rate found in the graphite. The adoption of the HfC-SiC composite effectively inhibited the ablation on the throat. However, substantial erosion occurred on the interfaces due to the different ablation resistances. The feasibility of adopting hafnium-based carbide on the rocket was also evaluated based on a material analysis of the surface oxidation.

Droplet Size Distribution Characteristics of Aerial Nozzles by Bell206L4 Helicopter under Medium and Low Airflow Velocity Wind Tunnel Conditions and Field Verification Test

To investigate the spray atomization characteristics of aerial nozzles adapted to manned agricultural helicopters under medium-low airflow velocity (0 to 27.8 m/s) conditions, the droplet size test was carried out in both wind tunnel and field tests. In the wind tunnel test, the laser diffraction device (LDD) was used to test the spray droplet size of CP02, CP03, and CP04 aerial nozzles. A Bell206L4 helicopter was used in the field test. The results in the wind tunnel test showed that due to the nozzles had been used for a long time and the cause of wear, the spray stability of individual nozzles was affected during the test. The limitation of droplet size measurement by using LDD was also found. The field test results showed that the main distribution range of the droplet size measured in the field test was consistent with the results of the wind tunnel test, but the droplet size value was significantly higher and the uniformity of droplet size distribution was poorer than the wind tunnel test value due to the influence of the actual environment. However, the results of field test and wind tunnel test can still be used as a reference for each other.

Development Research and Crucial Technology Analysis of Scaled 3-Bearing Swivel Duct Nozzle Rotary Drive System

The 3-bearing swivel duct (3BSD) nozzle for short-range/vertical take-off and landing(S/VTOL) fighters is a crucial component for aircraft to achieve vertical and/or short take-off and landing, which significantly improves the manoeuvre ability of the aircraft, while the nozzle rotary drive system is the crucial technology for S/VTOL functions which has significant impact on the fighter performance. Based on the principle and characteristics of the 3BSD nozzle, this paper systematically reviews the development and evolution of the 3-bearing swivel duct nozzle, and analyses and summarizes the types and characteristics of the 3BSD nozzle rotary drive system. Three crucial technologies of the 3BSD nozzle rotary drive system are evaluated and discussed in detail. Suggestions on future research and development of equipment are given.

Drying of moist cookie doughs with innovative slot jet reattachment nozzle

The drying of moist porous media, such as pulp, paper and food products, is one of the most energy intensive processes in industry. Many convective drying processes utilize impinging jet nozzles. There have been many efforts to improve the transport characteristics of impinging jet nozzles. Utilizing the innovative slot jet reattachment (SJR) nozzle is an approach to make the convective drying process more efficient. This is mainly because SJR nozzles overcome the high flow rate constraint associated with the traditional slot jet (SJ) nozzle. In this paper, the drying characteristics of the SJR nozzle with exit angles of +20˚ and +45˚ are experimentally investigated for a snack cookie. The results are compared with those of SJ nozzle based on three criteria: identical air mass flow rate, fluid flow power, and peak exerted surface pressure. An IR camera is used to capture the sample surface temperature distribution during the drying process. The results indicate that up to 57% reduction in drying time to reach 2% dry basis moisture content level is achieved with SJR + 20° nozzle compared to that of SJ nozzle based on the equal surface peak pressure criterion.

Effect of the physical properties of liquid and ALR on the spray characteristics of a pre-filming airblast nozzle

Abstact The atomization and combustion characteristics of fuels injected in aviation gas turbine engines are very important in the research and development of gas turbine combustors and have a significant impact on engine efficiency and pollutant emissions. In this study, spray atomization characteristics of pre-filming airblast nozzles developed for use in aviation gas turbine combustors were experimentally investigated for different air to liquid ratios (ALR) and air pressure differences (ΔP (%)). Pure water and Jet A-1, which have different viscosities and surface tensions that greatly affect the atomization characteristics, were used as the working fluid. Spray atomization characteristics were investigated by simultaneous measurement of droplet sizes and velocities using PDA (phase Doppler anemometry) and spray visualization using a CCD camera coupled with a Nd:YAG laser as a light source. The atomization characteristics of water and Jet A-1 showed significant differences in spray angle, velocity distribution and mean droplet size. Jet A-1 spray with lower surface tension showed a smaller mean drop size (WMSMD) than water spray did. As the ALR increased, the mean droplet size of the two liquids decreased. From the analysis of the spray flow characteristics, the surface tension associated with aerodynamic instability was the dominant variable in the atomization process with liquid sheet disintegration. The experimental constants included in the previously proposed empirical formulas for predicting the mean droplet size of the pre-filming airblast nozzle spray were presented for the two liquids used in the experiment.

Study on flow field and temperature field characteristics of gas-liquid two-fluid snowmaking nozzle

Study on flow field and temperature field characteristics of gas-liquid two-fluid snowmaking nozzle