Optimum Nozzle Research Articles

Investigation of Fluid Flow and Steel Cleanliness in the Continuous Casting Strand

Fluid flow in the mold region of the continuous slab caster at Panzhihua Steel is investigated with 0.6-scale water model experiments, industrial measurements, and numerical simulations. In the water model, multiphase fluid flow in the submerged entry nozzle (SEN) and the mold with gas injection is investigated. Top surface level fluctuations, pressure at the jet impingement point, and the flow pattern in the mold are measured with changing submergence depth, SEN geometry, mold width, water flow rate, and argon gas flow rate. In the industrial investigation, the top surface shape and slag thickness are measured, and steel cleanliness including inclusions and the total oxygen (TO) content are quantified and analyzed, comparing the old and new nozzle designs. Three kinds of fluid flow pattern are observed in the SEN: ‘‘bubbly flow,’’ ‘‘annular flow,’’ and an intermediate critical flow structure. The annular flow structure induces detrimental asymmetrical flow and worse level fluctuations in the mold. The SEN flow structure depends on the liquid flow rate, the gas flow rate, and the liquid height in the tundish. The gas flow rate should be decreased at low casting speed in order to maintain stable bubbly flow, which produces desirable symmetrical flow. Two main flow patterns are observed in the mold: single roll and double roll. The single-roll flow pattern is generated by large gas injection, small SEN submergence depth, and low casting speed. To maintain a stable double-roll flow pattern, which is often optimal, the argon should be kept safely below a critical level. The chosen optimal nozzle had 45-mm inner bore diameter, downward 15 deg port angle, 2.27 port-to-bore area ratio, and a recessed bottom. The pointed-bottom SEN generates smaller level fluctuations at the meniscus, larger impingement pressure, deeper impingement, and more inclusion entrapment in the strand than the recess-bottom SEN. Mass balances of inclusions in the steel slag from slag and slab measurements show that around 20 pct of the alumina inclusions are removed from the steel into the mold slag. However, entrainment of the mold slag itself is a critical problem. Inclusions in the steel slabs increase twofold during ladle changes and tenfold during the start and end of a sequence. All of the findings in the current study are important for controlling slag entrainment.

Optimized Automatic Recovery of Nozzle Health in Inkjet Systems

During the new print head installation process, an inkjet printer carries out several servicing actions to set the print head in the optimum printing conditions. In inkjet systems using pigmented inks there are known issues such as pigment settling after long periods of storage that can clog nozzles and cause bad drop ejection. This paper summarizes a system that initializes print heads after long periods of storage and inactivity. The system measures the level of nozzle health degradation and adjusts the servicing routines correspondingly, thus minimizing the ink waste and time required to guarantee an optimum nozzle health status for printing.

Studies on ejector-venturi fume scrubber

Experimental studies on diesel fume scrubbing have been conducted in a down-flow type liquid-jet ejector-venturi scrubber. The fume particulates have been captured in the throat of the ejector-venturi by a mechanism involving inertial impaction and impingement. The effect of nozzle geometry and the motive fluid flow rates on the suction created and the volumetric fume aspiration rates have been analyzed, in order to select the optimum nozzle geometry. Using the optimum nozzle geometry the efficiency of fume collection has been experimentally investigated as function of various hydrodynamic parameters. A theoretical analysis has been performed to interpret the experimental findings and determination of nozzle loss coefficients.

Design of optimal contours of supersonic parts of solid-propellant motor nozzles with use of direct variational methods

We present the results of designing the contours of supersonic parts of the solid-propellant rocket motor (solid motor) nozzles with high expansion ratios with the aid of direct variational methods. A continual model is used for the motion of a two-phase polydispersed continuum with regard for processes of interaction both between the carrying gas and the particles suspended in it and between the particles of various fractions. The method of local variations is employed as a numerical method of searching for the extremum of a multivariate function. The computational results evidence a fair efficiency of the proposed approach for the optimization of such nozzles.

Performance Measurements of Multicycle Pulse-Detonation-Engine Exhaust Nozzles

Performance measurements of multicycle pulse-detonation-engine (PDE) exhaust nozzles were obtained using a damped thrust stand. A pulse detonation engine of 1.88 m length was operated on a cycle frequency of 30 Hz at stoichiometric conditions. Both converging and diverging bell-shaped exhaust nozzles were tested for PDE fill-fractions ranging from 0.4 to 1.1. The area ratios of the nozzles were varied from 0.25 converging to 4.00 diverging. The nozzle length was negligible compared to the overall length of the PDE. The feasibility of normalizing the PDE nozzle thrust data was investigated by testing two different PDE combustion chamber diameters (2.54 and 5.08 cm) with the same nozzle area ratios. The optimum nozzle area ratio was found to be a function of the PDE fill-fraction. For fill-fractions at or below 0.5, the optimum configuration was a PDE without an exhaust nozzle. However, as the operating fill-fraction was increased to values close to or above one, thrust enhancement was obtained with a converging nozzle. The diverging nozzles also showed a relative increase in their performance with increased fill-fraction. Unlike the converging nozzles, the diverging nozzles and baseline configuration were observed to be sensitive to the ignition delay.

A seat microvalve nozzle for optimal gas-flow capacity at large-controlled pressure

Seat microvalves are the most common microvalve type for gas-flow control. This paper presents a general method for optimizing the flow capacity of a seat valve nozzle and diminishing the requirements on the valve actuator's stroke length. Geometrical analysis and finite element (FE) simulations show that for controlling large gas flow at elevated pressure, the optimal nozzle design in terms of flow capacity for a given actuator performance is a multiple-orifice arrangement with miniaturized circular nozzles. Experimental results support the design introduced in this paper.

A New Vertical Axis Wind Rotor Using Convergent Nozzles

There is very little in the literature dealing with vertical axis wind turbines using convergent nozzles. This work is one of the first on this vital area. We introduce a new concept of amplifying wind speed before it comes in contact with the blades of a newly designed rotor by using a convergent nozzle. Instead of using large central station power plants, these new rotors can be most conveniently built in smaller units appropriate for individual load requirements. The work is particularly significant given the current trend towards distributed or dispersed generation. We also attempt to analyze the optimum nozzle dimensions for a better performance of the system; and we conduct a research program involving wind tunnel tests of five different nozzle models. 'The length and the outlet area of the nozzle were changed periodically to see their effect on the increase of wind speed. The variation of the output speed with different values of input wind speed, different input areas of nozzle, and different lengths of nozzle placed at different distances from the wind tunnel is detailed. Results of additional study of a new rotor's performance characteristics using concentrating nozzles are also been outlined.

화염의 상호작용에 의한 부분 예혼합화염의 화염날림 유속 확대

For the non-premixed interacting jet flames, it has been reported that of eight small nozzles are arranged along the circle of 40~72 times the diameter of single jet, the flames are not extinguished even in 200m/s. In this research, experiments were extended to the partially premixed cases to reduce both flame temperature and NOx emission. Nine nozzles were used- eight was evenly located along the perimeter of the imaginary circle and one at the geometric centre. The space between nozzles, S, the equivalence ratio, Φ, the exit velocity and the role of the jet from the centre nozzle were considered. Normally, flame was lifted and flame base was located inside the imaginary circle made by the nozzle. As nozzles went away from each other, blowout velocity increased and then decreased. The maximum blowout velocity diminished with the addition of air to the fuel stream. When the fuel and/or oxidizer were not fed through the centre nozzle, the maximum blowout velocity obtained by varying S and Φ was around 160m/s. Optimum nozzle separation distance at which peak blowout velocity obtained also decreased with Φ decrease. Flame base became leaner as approaching to the blowout. It seemed that lots of air was supplied to the flame stabilizing region by the entrainment and partially premixing. To approve this idea and to enhance the blowout velocity, fuel was supplied to the centre region. With the small amount of feul through centre nozzle, partially premixed flame could be sustained till sonic velocities. It seemed that the stabilizing mechanism in partially premixed interacting flame was defferent from that of non-premixed case because one was stabilized by the fuel supply through the centre nozzle but the other destabilized.

レーザーパルスジェットのノズル形状と推進性能の数値解析

The relationship between the momentum-coupling coefficient C and the nozzle cone-angle of laser pulse-jets is investigated using Computational Fluid Dynamics. Temporal variations of thrust and pressure fields inside and outside conical nozzles are obtained, and computed C is compared with measured one. As a result, the computation well reproduces the measured C and its decreasing tendency with the nozzle cone-angle. The reason of this tendency is explained in relation to two-dimensional flow characteristics in its air-refresh process. In addition, it is suggested that the laser pulse width should be short enough that the laser-heated region can be smaller than the optimum nozzle size.

Air concentrating nozzles: a promising option for wind turbines

Although the use of wind turbines has become necessary in many parts of the world, the actual developments in wind turbines do not concern countries where the average wind speeds are low. The paper introduces a new vertical axis wind rotor using a convergent nozzle for low wind speed areas. This paper brings a detailed theoretical and practical study of air concentrating nozzle and the optimum nozzle dimensions have been analysed in detail. A research programme involving wind tunnel tests of five different nozzle models has also been conducted. The length and the outlet area of the nozzle were changed periodically to see their effect on the increase of wind speed. The variation of the output speed with different values of input wind speed, different input areas of nozzle and different lengths of nozzle placed at different distances from the wind tunnel have been outlined in the paper. Results of additional study of the new rotor's performance characteristics using concentrating nozzles have also been outlined.

ENHANCEMENT OF BLOWOUT LIMIT BY THE INTERACTION OF MULTIPLE NONPREMIXED JET FLAMES

The effects of interaction between nonpremixed flames on the enlargement of blowout velocity are experimentally investigated. Nozzle separation distances, fuel flow rates, number of nozzles, and array shapes are considered to make flame interaction. Four types of nozzle arrays, which are arranged in diamond, cross, matrix, and circle shapes, are used. Interacting flame has two distinct characteristics compared with a single jet flame—higher blowout velocity and constant turbulent liftoff heights. There are optimum nozzle separation distances for the augmentation of blowout limit. Blowout velocities for the small-diameter multiple jets are higher than a single large-diameter nozzle with the same area. The flames are not extinguished even in choking conditions at the nozzle exit when there is not a nozzle at the center of optimally spaced matrix- or circle-shaped configurations. Flow visualization shows that the enhanced stability in the case without a center nozzle is due to recirculation within the fuel jet arrays.

Geometry Optimizatin of Hypersonic Wind Tunnel Nozzle

This paper describes the application of the optimization procedure for a supersonic wind tunnel two-dimensional variable nozzle contour developed in the previous report to the optimization of a hypersonic wind tunnel axisymmetric nozzle contour of Mach number higher than 5.0. In this procedure, several positions are set on the nozzle wall, and using the linearity of a displacement of each position to the flow pattern, the optimum nozzle contour is determined in a few cases of CFD analyses. To take an axisymmetric nozzle of Mach number 10.0 as an example, optimization was carried out. Mach number deviation in the uniform flow region reduced from 1.48% to 0.40% by the optimization.

Optimization of Fuel Injection Nozzles for the Reduction of NOx Emissions in Medium-speed Marine Diesel Engines(Diesel Engines, Performance and Emissions, NOx Strategies)

Numerical simulations and experiments have been carried out to investigate the effect of fuel injection nozzles on the combustion and NO_X formation processes in medium-speed marine diesel engines. Spray and combustion phenomena were examined numerically using FIRE code. Wave breakup and Zeldovich models were adopted to describe the atomization characteristics and NO_X formation processes. Spray visualization experiment was performed in the constant-volume high-pressure chamber to verify the numerical results on the spray characteristics such as spray angle and spray tip penetration. Time-resolved spray behaviors were captured by high-speed digital camera and analyzed to extract the information on the spray parameters. Numerical analysis of fuel injection system was also performed to get the profiles of fuel injection rate, which should be given as an input data for the combustion analysis. Numerical results were verified with experimental data such as cylinder pressure, ROHR (Rate of Heat Release) and NO_X emission. Finally, the effects of fuel injection nozzles on the engine performance were investigated numerically to find the optimum nozzle parameters such as fuel injection angle, nozzle hole diameter and number of nozzle holes. From this study, the optimum fuel injection nozzle (nozzle hole diameter, 0.32 mm, number of nozzle holes, 8 and fuel injection angle, 148°) was selected to reduce both the fuel consumption and NO_X emission. The reason for this selection could be explained from the highest fuel-air mixing in the early phase of injection due to the longest spray tip penetration and the highest heat release rate after 19° ATDC due to the increased injection duration.

Vertical Axis Wind Rotor with Concentration by Convergent Nozzles

This Dissertation Note describes practical tests on small vertical axis turbines using concentrating convergent nozzles. The nozzles amplify the wind-speed before the air contacts the blades. The purpose of the work relates to distributed power generation in regions with weak, mainly single-directional winds. Wind-tunnel tests of five different nozzle arrangements have been conducted. The length and outlet area of the nozzles were changed to see the effect on the increase of wind speed. The variation of the output wind-speed with different values of input wind speed, different input areas of nozzle and different lengths of nozzle have been recorded. The tests identify the optimum nozzle dimensions for improved performance of the system.

Influence of Different Cleaning Conditions on Cleaning Performance of Pilot-Scale Pulse-Jet Baghouse

In this study, a pilot-scale pulse-jet baghouse is utilized to control the particulate emission of an oil-fired boiler. The operating and design parameters, such as filtration velocity, initial tank pressure, and nozzle diameter, were varied to evaluate the cleaning effect of the pulse-jet baghouse. Two different cleaning types, (1) high initial tank pressure and one bag cleaning; and (2) low initial tank pressure and two consecutive bag cleanings, are used to compare the bag-cleaning performance in this study. It is found that the cleaning effect increases with the initial tank pressure. However, the cleaning intensity (overpressure) does not increase with the nozzle diameter. There exists an optimum nozzle diameter to achieve higher cleaning intensity and a better cleaning effect. This phenomenon results from the small volume of the baghouse compartment in this study. If an industrial size baghouse was used, it suggests that a nozzle diameter larger than 13 mm and initial tank pressure greater than 2.5 kg/cm2 should be adopted to achieve a higher cleaning effect. Between the two cleaning types, type 2 is found to be more effective to clean the bag and the energy consumption for compressed air is reduced significantly from type 1. Therefore, type 2 bag cleaning is suggested to be a better method to clean the baghouse.

Designing a Jet Mill Nozzle of Maximum Efficiency

A method of calculation for an accelerating jet mill nozzle profile which provides a maximum kinetic energy for solid particles at the nozzle outlet, is developed. The gas-solid flow in the nozzle is described by a well-known one-dimensional model. The effect of both solid loading and particle size on the optimal nozzle profile, as well as on the main flow parameters is studied. Distribution of particle velocities in the computed optimal nozzle is compared to that in a conical convergent-divergent nozzle of the same length. Computations demonstrated that optimized nozzles are profitable for fairly low solid loadings. The kinetic energy of solids at the optimized nozzle outlet is about 50% higher than that in a conical nozzle if the solid/gas mass flow ratio equals unity.

보호피막 처리에 의한 굴 레토르트 식품의 품질 개선

굴의 레토르트 가공적성을 향상시키기 위하여 굴에 포함되어 있는 섭을 제거하는 방법과 가식성 보호피막제를 사용하여 보호피막을 입히는 방법 및 그 효과에 대하여 연구하였다. 굴중의 섭을 제거하기 위하여 공기방울을 불어 올리는 방법을 사용하였는데 세척유속과 노즐의 기공 크기는 섭 제거에 있어서 중요한 요인이었다. 섭 제거 효율과 패육의 보호를 고려하여 각 회의 처리 시간을 1분간으로 하고 45 L/min으로 하는 경우는 2회 세척이 적절한 것으로 판단되며, 노즐의 기공 크기는 0.4 mm의 노즐을 사용하는 것이 유리할 것으로 사료된다. 기본 피막제로서는 sodium alginate가 적당하였으나 피막제의 농도가 높을수록 보호 피막이 잔존하여 식감을 떨어뜨리는 단점이 있었다. 피막능력을 개선시키기 위하여 보조피막제를 검토한 결과, 탈지분유>찰옥수수전분>Purity CSC>백옥분>carboxymethylcellulose 순으로 좋게 나타났다. 따라서 피막제의 조성은 sodium alginate 1.5%와 탈지분유 0.9%가 보호 피막제로서 가장 적합한 것으로 판단되었다. 보호피막을 입힌 굴을 이용하여 제조한 죽은 피막을 입히지 않은 굴과 비교한 결과 레토르트 직후에는 대조군과 색도나 안정성에서 큰 차이를 보이지 않았으나 상온에서의 저장기간이 길어짐에 따라 보호피막에 의한 효과가 크게 나타났다. 결론적으로 섭을 제거한 굴에 보호피막을 입힘으로써 굴죽의 제조 공정 중에 발생될 수 있는 물리적 손상으로부터 굴의 형체가 보호되었으며 굴죽의 저장시 발생되는 갈변현상을 방지하여 가공적성이 향상됨을 확인할 수 있었다.

Carbon Particle Cloud Generation for a Solar Particle Receiver

The development and performance of a full-scale carbon particle cloud generator together with the evaluation of nine commercial carbon blacks is reported. Large variations were found in the dispersability and settling properties of the investigated powders. Scanning electron microscope analysis of cloud samples from different powders showed unequal state of agglomeration and particle size. The particle population distribution of the most suitable powder was determined, showing that the particle cloud consisted of 99.8% spheroid primary particles (25–570 nm dia) and 0.2% large irregularly shaped agglomerates. Although the numerical fraction of the agglomerates was only 0.2%, they contributed 40% to the cloud’s geometrical cross section. Significant variations in the population distribution were found from different batches of the same particle powder. The developed full-scale particle generator was capable of sustained operation, creating a particle cloud with an extinction coefficient exceeding 40m−1 at a nominal flow rate of 25 SLPM. The dispersal efficiency of the system with the optimal ejection nozzle was 25%, compared to less than 1% for free ejection. The particle dispersal rate was 30 g/hr at 25 SLPM at an evacuation efficiency of 87%. Specific extinction cross-sections of 5.8m2/g were measured for particle mass loading higher than 2g/m3.

Optimal particle acceleration in a jet mill nozzle

The optimal profile of the accelerating nozzle of a jet mill is computed to provide a maximum particle velocity at the nozzle outlet. To describe one-dimensional monodispersed flow in the nozzle, the well-known set of differential equations is employed. The influence of both particle size and solids/gas mass flow rate on the optimal nozzle profile is studied. Computations show that an employment of optimized nozzles is beneficial for relatively low solids loading. An increase in particle velocities at the optimized nozzle outlet reaches 25% compared to those in a conical nozzle if the solids/gas mass flow ratio equals unity.

Profiling the Supersonic Part of a Plug Nozzle with a Nonuniform Transonic Flow

The effect of transonic flow nonuniformity on the profiling of optimal plug nozzles is studied in the inviscid gas approximation. Sonic and supersonic regions providing maximum thrust for given nozzle dimensions and a given outer pressure are designed for given subsonic contours and calculated nonuniform transonic flows. As in the case of uniform flow on a cylindrical sonic surface, the initial regions of the designed contours satisfy the condition that in these regions the flow Mach number is unity or near-unity. In all the examples calculated, the optimal plug nozzles produce a greater thrust than the optimal axisymmetric and annular nozzles with a near-axial flow for the same lengths and the same gas flow rates through the nozzle. It is established that contouring without regard for transonic flow nonuniformity can result in considerable thrust losses. However, these losses are due only to a decrease in the flow rate, while the specific thrust may even increase slightly.