Nozzle Structure Research Articles

Numerical Simulation of Flow Field of Submerged Angular Cavitation Nozzle

A model of a submerged angular cavitation nozzle is established, which consists of a contraction part, parallel middle part, and expansion part. Based on the CFD technique, a numerical simulation of the flow field of the submerged cavitation nozzle is carried out, in which a multiphase mixture model, cavitation model, and renormalization group (RNG) k-ε turbulence model are applied. Considering the influence of mixture density on cavitation, the effects of the inlet contraction part, parallel middle part, and outlet expansion part on the velocity and vapor volume fraction are studied. The numerical simulation results show that the mixture density is essential in the cavitation jet. When the nozzle diameter d is fixed, the designed angular cavitation nozzle with contraction angle α = 13.5°, parallel middle part length Ld = 3d, expansion part length Le = 4d, and expansion angle β = 60° can effectively bring out cavitation. A cavitation cloud is produced near the rigid wall of the outlet expansion section and diffuses in a vortex ring shape. Optimizing the nozzle structure can improve the cavitation effect of the nozzle. The feasibility of this model is verified by relevant experimental data.

Improving combustion and lowering NO emissions of an industrial coal swirl burner by optimizing its nozzle structure

• Simulation and comparison are conducted for the burner before and after optimization. • Entrained effect of secondary air on primary air is enhanced with retrofitting ISACS. • Retrofitting ISACS has significant effects on the combustion characteristics. • Optimized burner performs better in NOx reduction, flame stability and burnout rate. To accommodate rapidly growing but highly variable renewable power in the grid and large variations in power demand, coal-fired power plants need to be flexibly operated through fast and wide load changes, still with high efficiency and reliability and low emissions. Towards reliable implementation in a power plant under flexible operation, this paper comprehensively investigates the improvement of an industrial low-NO x swirl burner via numerical simulation and various field tests. Burner aerodynamics, which play a vital role in its performance, are largely affected by the burner nozzle structure. For the low-NO x swirl burner under study, the inner secondary air cone structure is found to have the most significant impact on the burner aerodynamics and the combustion performance. For the coal fired in the power plant, the newly designed inner secondary air cone structure, which is a kind of an extended smooth diverging duct, greatly facilitates the entrainment of the primary air into the surrounding swirl secondary air stream and largely enhances lateral mixing. A large recirculation zone is formed between the primary air and the inner secondary air stream, stabilizing ignition and combustion under flexible operation conditions. This is particularly important for low-load operation. Comparatively, reducing the secondary air duct area for a higher axial momentum of the secondary air stream and adding a new particle separation ring for more dispersed particle distribution are found to have a minor impact on the burner aerodynamics. The optimized burner nozzle structure via numerical simulation has been finally adopted by the power plant for the burner retrofit, on which various field tests have been performed on the retrofitted burner. The tests show that the nozzle structure optimization remarkably improves the burner performance, which is also consistent with the numerical prediction. This study also provides useful guidance for optimizing the swirl burners of the similar type.

Design and optimization of dry powder jet cleaning nozzles for airport navigation lights

The research of this work is based on the nozzle design and optimization of dry powder (NaHCO3) jet cleaning system for airport navigation aid lamps. In this cleaning system, compressed air drives dry powder (NaHCO3) abrasive, and a gas-solid mixed high-speed jet is sprayed onto the surface of the luminaire through the nozzle to scour and clean the dirt attached to the surface of the luminaire. Based on the computational fluid dynamics and flow field theory, three types of nozzle structures, namely tapered nozzle, Laval nozzle, and flat nozzle, were studied; the DPM (Deformable part model) model in Fluent was used to analyze the internal and external flow fields of the nozzle mixed with the gas-solid two-phase flow to obtain the velocity field, pressure field and nozzle wear rate of the mixed gas, and the flat nozzle was selected and the nozzle parameters were optimized. The optimized level combination of flat type nozzle structure is obtained with a flat width of 4mm, flat height of 24.5mm, and flat length of 55mm.

Influence of nozzle structure on the flow field of the prestage of nozzle flapper servo valve

Influence of nozzle structure on the flow field of the prestage of nozzle flapper servo valve

Influence of Nozzle Structure of Oxygen Lance on Impact Dynamic Characteristics of Supersonic Jet

In order to realize the smelting effect of high oxygen supply intensity in large and medium-sized converters, a new six hole oxygen lance nozzle with double angle, double flow and staggered double structure is designed in this paper, and the jet characteristics are compared with those of the traditional structure oxygen lance. According to the theory of fluid dynamics and the principle of similarity, the velocity attenuation of the centerline of the jet and the longitudinal section of the oxygen jet are tested by using the oxygen gun jet detection experimental system. The results show that the jet performance of the staggered double structure six hole oxygen lance nozzle is better than that of the traditional structure oxygen lance nozzle. When the ratio of large hole flow is 55%-65%, the angle of large hole is 12°-14°and the angle of small hole is 16°-18°, the ratio of hole flow plays a leading role in the size of jet velocity. The greater the flow distribution, the greater the jet velocity. Using staggered double structure six hole oxygen lance can improve the stirring force of the jet to the molten pool.

A mechanics model in design of flexible nozzle with multiple movable hinge boundaries

In this paper, we propose a modified variational approach to predict the morphology of the flexible nozzle used in wind tunnel. Different from previous studies, the movements of the multiple hinges are considered as movable displacement boundary conditions during establishing the potential energy functional. The cubic spline interpolation method is employed to supply the supplementary boundary conditions in calculation of the functional minimization problem. Current analytical model is verified by experiments carried out on a fixed-flexible nozzle structure whose geometries and materials are the same as those from a commissioned supersonic nozzle. The maximum deviation between the predictions from theoretical method and laser displacement testing does not exceed 0.5 mm. This method can also deal with the large deflection beam problem with multiple movable boundaries.

Study on Separation Characteristics of Nozzles with Large Expansion Ratio of Solid Rocket Motors

In order to study the flow characteristics of a nozzle with large expansion ratio and its influence on the force on the nozzle, ground cold flow test research and a fluid–structure coupling simulation analysis were carried out (maximum expansion ratio ε = 30.25). The variation and pulsation characteristics of the pressure near the measuring point area and the inlet pressure were obtained through experiments. Through the analysis of the peak-to-peak value and average value, it was found that the average pressure after separation increases by 90%, but the peak-to-peak value increases by about five times, indicating that the pressure fluctuation after separation is much larger than before separation. The separation flow field under cold flow conditions was simulated using the CFD commercial calculation software Fluent to verify the correctness of the numerical calculations. The fluid–structure coupling analysis was carried out on a large expansion ratio (maximum expansion ratio ε = 48) full-scale nozzle, and the structural deformation characteristics of the nozzle under the separation conditions were studied. The research results show that flow separation occurs in the nozzle with a large expansion ratio under ground conditions. Before the separation point, the pressure pulsation on the nozzle wall is small, and the turbulent pulsation effect is weak. After the separation point, the pressure pulsation increases, and the turbulent pulsation effect is enhanced. When the total pressure decreases, the separation area of the nozzle increases, and the separation flow field presents a strong asymmetry. Reducing the total inlet pressure by half resulted in approximately 50 times the lateral load. Under the combined influence of the ground conditions and low total pressure, the large lateral load caused by the asymmetry of the separation flow field will cause the deformation of the nozzle structure to increase by 5.5 times. This research provides an important reference for the design and experiment of nozzles with a large expansion ratio.

Orthogonal Experimental Design Based Nozzle Geometry Optimization for the Underwater Abrasive Water Jet

This paper proposes an orthogonal experimental design based on the optimization method for the nozzle geometry of an underwater abrasive water jet, with the objective of maximizing the cutting capacity and minimizing the nozzle-erosion rate. Parameter effects on the nozzle’s cutting capability and life are analyzed. This analysis shows that while the contraction-section curve, the contraction-section axial length and the focus-section axial length mainly affected the service life of the nozzle, the nozzle-outlet diameter mainly affected the cutting capacity of the nozzle. The effect significances of the structural parameters, from high to low, are outlet diameter > axial length of contraction section > axial length of focusing section > contraction curve. According to the optimal performance index for this nozzle, the optimal nozzle structure parameters were a contraction-section curve of A4 (parabolic), an axial length of contraction section of 20 mm, an outlet diameter of 2 mm, and an axial length focusing section of 10 mm. With the optimal parameters, the nozzle performance excellence index was Q = 1.441, which is the optimization objective and 44.1% higher than the baseline of the conical nozzle; the maximum velocity at a distance of 100 mm was improved by 56% and the maximum erosion rate was reduced by 72% compared to that of the conical nozzle.

Numerical investigation of flow resistance in cone-straight nozzle

High-pressure water jet technology is applied to wellbore cleaning, descaling, auxiliary rock breaking, slit penetration, etc. In petroleum engineering. The cone-straight nozzle structure is widely used in the petroleum industry, and its internal flow resistance remains unclear, which plays an important role in nozzle geometry optimization and is the main research content in this paper. Large Eddy Simulations were used to simulate the near-wall flow field at a relatively low Reynolds number, the flow resistance is analyzed based on the numerical calculation data, and the following conclusions are drawn: The friction resistance is mainly distributed at the end of the converging section and the throat section, and there is a peak value, and the viscous force is mainly distributed in the converging section; the streamline structure can effectively reduce the skin friction resistance, and has little effect on the viscous force, which is more sensitive to the length of the nozzle; the streamline structure can change the trend of the total pressure in the nozzle, but has little effect on the kinetic energy conversion efficiency of the entire nozzle; increasing the fluid viscosity significantly increases the flow resistance in the nozzle. The purpose is to reveal the flow resistance inside the nozzle, investigate the factors affecting the flow resistance and provide theoretical support for the optimization of the nozzle structure.

Analysis of flexible air bearing and design of testing machine

The paper takes a type of flexible air bearing as the research object, and the bearing structure is analyzed in detail. Combined with the traditional analysis method of tilting pad bearing and the fluid-solid coupling theory, a new analysis model for performance prediction of the bearing was established. The performance of air bearing with inner diameter of 70mm was calculated by changing the input pressure or the inlet capillary diameter. The structure of the bearing was optimized by analyzing the calculation results, and the structure of the separate inlet nozzle was added. A bearing testing machine is designed for the flexible air bearing test to verify the improvement of bearing performance.

Discovery of SiO masers in the “Water Fountain” source, IRAS 16552–3050

AbstractWe report new detections of SiO ν = 1 and ν = 2 J = 1 → 0 masers in the “water fountain” source IRAS 16552-3050, which was observed with the Nobeyama 45 m telescope from March 2021 to April 2023. Water fountains are evolved stars whose H2O maser spectra trace high-velocity outflows of >100 Km s−. This is the second known case of SiO masers in a water fountain, after their prototypical source, W 43A. The line-of-sight velocity of the SiO masers are blue-shifted by ∼25 km s−1 from the systemic velocity. This velocity offset imply that the SiO masers are associated with nozzle structure formed by a jet penetrating the circumstellar envelope, and that new gas blobs of the jet erupted recently. Thus, the SiO masers imply this star to be in a new evolutionary stage.

Effect of Swirling Flow Nozzle on Fluid Flow and Solidification in a Round Bloom Continuous Casting Mold

The nozzle structure has an important effect on the fluid flow in the mold, which can significantly improve the solidified shell and product quality of alloy steel round bloom. The transient fluid flow, heat transfer, and solidification behavior under different nozzle structures and mold electromagnetic stirring (M-EMS) are investigated using a 3D transient mathematical model. The results show that a third small recirculation zone appears near the meniscus after the application of the swirling flow nozzle (SFN). The impact depth of SFN is shallower than that of the original submerged entry nozzle (SEN) impact, and the lower circulation zone is shifted upward. The horizontal swirling flow generated by SFN can significantly weaken the washing of the initial shell by high-temperature steel and improve the uneven growth phenomenon of the inner and outer curved solidified shell caused by mold curvature. The swirling flow produced by M-EMS in the mold can also improve the washing of the initial shell by the high-temperature jet and the uneven growth of the inner and outer curved shell. M-EMS can expand the high-temperature zone in the upper part of the mold, promote the superheat dissipation of the molten steel, and promote the growth of the solidified shell. In addition, after the application of M-EMS, the tangential velocity of -15° SFN in the meniscus is smaller, and the resulting liquid level fluctuation is lower at 5.07 mm, which is less likely to produce slag entrapment and is conducive to improving the quality of round bloom.

Modelling, Optimization, and Experimental Studies of Refrigeration CO2 Ejectors: A Review

CO2 is regarded as an effective and environmentally friendly refrigerant. Using a CO2 ejector is a proven method for enhancing the effectiveness of a transcritical CO2 refrigerant system. However, the complex internal flow of a CO2 ejector, involving supersonic effects, phase change effects, metastable effects, and so on, makes it difficult to understand. In order to summarize the current state of the technology and knowledge gaps, this work provides a comprehensive literature review on CO2 ejectors. In the first part, mathematical modelling and simulation calculations of CO2 ejectors are presented, and an overview and classification of ejector models are given. In the second part, the structural optimization part of the ejector is described in detail, and the nozzle structure, the mixing chamber length, improvements to multi-jet systems, and the impact of these factors on the system performance are analyzed. In the third part, flow visualization is used to study the complex flow phenomenon, and the effect of the shock wave on the entrained rate of the ejector is discussed. Finally, the paper outlines the relationship between all ejector technologies, working fluids, and ejector performance and makes valid recommendations for further research and development of CO2 ejectors.

Numerical analysis of the combustion characteristics of graphitic hydrogen-chlorine synthesis combustor with different intake strategies

This study investigates the effect of intake strategies on the combustion and flows characteristics of hydrogen-chlorine synthesis combustors via numerical methods. A crucial issue of hydrogen-chlorine synthesis combustor is to have a sufficiently low flame height and high conversion efficiency. In this study, the combustion performance of combustors equipped with the annular tube, plum nozzle, and porous-bullet nozzle has been thoroughly analyzed. The temperature distribution and gas flow are analyzed using the method of fluid-solid coupling, which indicates that the combustor with porous-bullet nozzle had the best gas distribution, the maximum HCl mole fraction at outlet is 97.24%, and the lowest flame height is 3.4 m, which is 27.15% lower than the combustor with the annular tube. Furthermore, the nozzle structure has a great influence on the fluid velocity in the recirculation zone of the combustor. Finally, the effect of hydrogen/chlorine equivalence ratio (ϕ) and inlet volume flow rate were analyzed, and it can be concluded that with the increase of inlet volume flow, the high-temperature area inside the combustor gradually increases. As the equivalent ratio increases, the combustor outlet's mole fraction changes with a normal distribution trend. It is the most appropriate when the chlorine gas flow rate is 1,100 m3/h and ϕ = 1.05. The research can be applied to the field of high-purity hydrogen chlorine production, providing researchers with some solutions.

Influence of nozzle structure on the combustion performance of a graphitic hydrogen-chlorine synthesis combustor

The growing semiconductor sector is driving up demand for high-purity gas-phase HCl. Large combustion zones and low HCl concentrations are problems for HCl manufacturing systems. Based on the realizable k-ε model, the eddy breakup combustion model, and the participating media radiation model, the computational fluid dynamics simulation was used as the primary means in this study. The influence of four structural factors, nozzle jet hole diameter, jet angle, and opening angle—another is nozzle mounting height, on the combustion effect of the synthesis combustor was investigated. The extent of the high-temperature zone in the synthesis combustor and the purity of the hydrogen chlorine at the outlet were used as the main evaluation criteria. The results of numerical simulations demonstrate that the better the gas mixing and combustion in the combustor, the lower the nozzle mounting height should be. Small nozzle diameters and large nozzle jet angle increase gas flow velocity in the recirculation zone close to the inner wall of the combustor. Additionally, the recirculation zone will appear in the combustor as a result of the nozzle's presence. The area of the high-temperature zone within the combustor decreases as internal gas velocity increases. On the other hand, the recirculation gas flow is not significantly impacted by the angle at the condition that the jet holes open. The results of the investigation provide a reference for the design of the miniaturization of the combustor in the non-premixed combustion synthesis of gases process.

Structure and arrangement optimization of non-diagenetic gas hydrate jet crushing nozzles based on CFD simulation

To optimize the optimal nozzle structure and multiple nozzle arrangement for hydrate jet crushing and to promote the development of solid fluidization extraction technology for shallow unconformity hydrate in China’s oceans, the submerged jet flow field of six commonly used nozzle structures in the downhole in-situ jet crushing process was analyzed on the basis of the solid fluidization extraction process in double-layer pipes, and the effect of the jet hole arrangement on the overflow performance of hydrate slurry in the outer annulus of double-layer pipes was also investigated. It was demonstrated that tapered straight nozzles were preferably selected as the nozzle type for hydrate solid fluidization mining process based on jet core stage length, jet energy dissipation rate, and jet fluid axial velocity. In the meantime, the optimum arrangement of the nozzles was preferred on the basis of the annular pressure drop and the flow resistance coefficient, with the number of single circle not higher than 3 and the axial spacing of the nozzles not lower than 50 mm. This study can provide a theoretical basis for nozzle selection and tool design for the solid fluidization jet crushing process of marine unconformable hydrates.

Flow field characteristic of water jet with air ring protective layer under submerged environment and the orthogonal optimization of nozzle structure

AbstractA water jet with an air ring protective layer is a promising rock‐breaking and cutting rate improvement method in submerged environment, such as oil–gas drilling. The jet flow field characteristic determines the jet impinge performance and is affected by nozzle structure parameters. In this study, the water jet flow with air ring under submerged environment was numerically simulated. The jet flow field structure with air ring was obtained by analyzing the distributions of jet velocity and air content at different cross sections. The effects of several critical nozzle structure parameters on jet isokinetic core length and axial velocity were investigated by adopting the orthogonal design method. The results show that the jet flow field structure with air ring in radial direction includes a high‐speed water jet zone, air ring protective layer, and air–water mixed zone, having the advantages of concentrated energy in axis region, long core section length, and low‐velocity attenuation. The influence degrees of nozzle structure parameters on jet core section length and axial velocity at X = 0.3 m are: length‐diameter ratio > outlet diameter > conic angle > air nozzle diameter > water‐air nozzle spacing and outlet diameter > length‐diameter ratio > conic angle > water‐air nozzle spacing > air nozzle diameter, respectively. The jet core section length and axial velocity both increase exponentially with the increasing outlet diameter, both first increase rapidly and then slowly decreases with the increase of conic angle and water–air nozzle spacing. There is the optimal conic angle of 15° and appropriate water–air nozzle spacing of 3–5 mm. With the increase of length–diameter ratio, they both first decrease rapidly and then slow down, indicating that conical nozzle is more suitable for water jet with air ring. And 0.9–1.2 mm is proper for the air nozzle diameter.

Effect of Special-Shaped Nozzle Structure on Water Jet Performance

The impact force and effective impact area of are water jet are two important indexes for evaluating jet performance, and the outlet shape of the nozzle has a great influence on jet performance. In this study, five nozzles with different outlet shapes were designed, and water jet test experiments were conducted at different inlet pressures using an independently built water jet impact test platform, and the influence law of nozzle shape on the center impact pressure and flow coefficient of the water jet was investigated. The influence of nozzle shape on the effective impact area and entrainment rate of water jet was further investigated by numerical simulation. The results showed that the center impact pressure of the circular nozzle was the greatest when the inlet pressure and the target distance were small. The center impact pressure, the flow coefficient, and the effective area of the triangular nozzle with sharp edges were better than the traditional circular nozzle when the inlet pressure and the target distance were increased. Although the center impact pressure of the square nozzle is lower than that of the circular nozzle, its flow coefficient and effective impact area are higher than those of the circular nozzle with increasing target distance. The water jets of the elliptical and cross nozzles were the most divergent, and the jet performance was poor.

Formation and control of longitudinal cracks in hypoperitectic steel slabs

ABSTRACT Hot delivery and charging techniques can significantly reduce energy consumption, carbon emissions, and the production cycle of products. The defect-free slab is the precondition of this techniques. Herein, the morphological characteristics of the longitudinal cracks were described in detail. The actual phase transition process and solidification shrinkage behavior were analyzed considering the effect of alloy elements. Due to the unreasonable submerged entry nozzle (SEN) structure, the vertical heat transfer is not optimal around the meniscus. When the gap cannot be filled with sufficient liquid slag, an air gap is easily formed between the solidified shell and the mould plates. The effect of uneven solidification and stress concentration on the crack formation will be enlarged by the air gap. A novel SEN with a reasonable structure can significantly improve the thickness of the liquid slag layer and solidification uniformity, and decrease the crack sensitivity of the steel.

Effect of structure parameters on low nitrogen performance of burner based on orthogonal experiment method

A flue gas internal and external double cycle low nitrogen burner was established. Using the method of orthogonal test, the number(n), inclination angle (i) and diameter (d) of the injection pipe, the end deflection angle(γ), overlap angle(β) and number (η) of the blade were set two levels respectively, and the maximum furnace temperature (Tmax), average furnace temperature (Tav) and NO emissions at the furnace outlet (MNO) were taken as experimental indexes. It is found (1) The influence degree of various factors of nozzle structure on the three indexes is n > d > i. The influence degree of cyclone structure factors on the three indexes is γ > β > η. The effects of factors i and η on the three indexes were negligible. However, the interaction of structural factors has different effects on the three indexes. (2) The size of the high temperature zone is the key reason for the formation of NOx. By adjusting the structural parameters, the fuel and oxidizer mixing process is enhanced, local high temperatures are avoided, and thermal NOx emissions are reduced. (3) In several of the cases studied, NO emissions from boilers were below 30 mg/Nm3, and in some cases below 10 mg/Nm3.