Discharge Nozzle Research Articles

Trajectory and spreading of falling circular dense jets in shallow stagnant ambient water

This study investigates the trajectory and spreading of a horizontal circular dense jet flow discharged above the water surface, the flow of which falls into shallow stagnant ambient water. For this purpose, 27 experiments were performed using three diameters, flow rates, and falling heights to investigate jet trajectory. In addition, nine experiments with constant falling height were conducted to study jet spreading. The densimetric Froude number of the jet flow at the nozzle outlet and water surface of the present study ranged from 0.72 to 4.22 and 36.96 to 86.10, respectively. The data pertaining to this study were extracted and analyzed through image processing. The results of the experiments showed that by increasing both the momentum and falling height, the trajectory of the jet flow reached a farther distance from the discharge nozzle. The spreading of the outer boundaries of the dense circular falling jet flow tended to extend downstream of the impact point and had an elliptical motion on the bed. The relationship between radial distance from the impingement point to the outer boundary of flow and time was determined to have a power of 0.67 for flow along the flume and 0.59 for flow along the flume's width.

Numerical and experimental study of supersonically expanding argon plasma using a micrometer hollow cathode discharge

Pulsed discharge nozzles (PDNs) have been successfully used for decades to produce rotationally cold (Trot ∼ 20 K) radicals and ions of astrophysical interest and to characterize these species spectroscopically. In this work, an evolution of the PDN, the piezostack pulsed discharge nozzle (P2DN), is used for the first time to investigate the characteristics of the still poorly understood supersonic plasma expansion. The P2DN allows for a better control of the reservoir pressure of which an accurate measurement is required to characterize the plasma expansion. This new source, thus, gives the opportunity to further optimize the plasma conditions and extend its use to new target species. The spatial distribution of an argon plasma and the effect of the supersonic flow for different pressures are studied by combining a two-dimensional extended fluid model (extFM) and a direct simulation Monte Carlo (DSMC) method. The combined simulation is validated with experimental results obtained through emission spectroscopy associated with a group-code collisional-radiative model to retrieve the plasma parameters. The validated numerical approach (DSMC-extFM) allows for an accurate characterization of the plasma structure in our typical experimental conditions (a reservoir pressure ranging from 90 to 905 mbar). Thus, this simulation will be used in future studies to improve the plasma conditions to favor the synthesis of (transient) hydrocarbon species as found in space, by seeding the argon gas with a suitable precursor, such as acetylene.

Aerodynamic sealing using a segmented recirculating horizontal air curtain for buoyancy-driven flows in doorways

Dealing with buoyancy-driven flow to reduce infiltration heat is challenging for buildings such as cold storages where the indoor-outdoor temperature differences are significant. In this study, a segmented recirculating horizontal air curtain (SRHAC) is proposed to respond to the vertical thermal buoyancy profile in doorways and recover the cold air entrained by the air curtain. Specifically, SRHAC is a planar turbulent impingement jet discharged through a vertically mounted rectangular nozzle. The discharge nozzle is divided into segments and the return vent recirculates the discharged air to the rear of the discharge nozzle. In this study, the aerodynamic sealing performance of the SRHAC is investigated by considering structural, operational, and ambient parameters. Orthogonal analysis reveals the flow rate, nozzle width, and discharge angle as significant factors affecting the thermal separation efficiency of the SRHAC. Increasing the flow rate and decreasing the nozzle width leads to an increase in the jet momentum flux, thereby enhancing the thermal separation efficiency, with a maximum efficiency of 75.9 %. Setting the discharge parameters in the three sections along the height improves the thermal separation efficiency by 16.5% points. The maximum efficiencies of two-, three-, and five-segment air curtains are 83.6 %, 87.3 %, and 90.3 %, respectively. The separation efficiency of the SRHAC remains relatively stable even when the indoor-outdoor temperature difference varies between 32 and 57 K. These results establish that the SRHAC is an efficient energy-saving device, with the ratio of reduced infiltration load to energy consumption as high as 110.9.

Proper orthogonal decomposition energy analysis in a nuclear reactor coolant pump based on PIV at the best efficiency point

The nuclear reactor coolant pump (RCP) is the core equipment of a nuclear power plant (NPP), and its stable and efficient operation is one of the keys to the development of the RCP. The RCP's large-scale and high energy flow structure can be revealed through effective experimental and post-processing methods, which will help fully understand the flow mechanism. Thus, the present work aims to conduct a comprehensive study on the RCP model pump based on Particle Image Velocimetry (PIV) flow field measurement, internal flow structure analysis, and POD (Proper Orthogonal Decomposition) at the best efficiency point. From the POD overall energy analysis, it is found that even if the diffuser is installed in the spherical casing, the energy distribution of each diffuser flow channel has great difference. Through the analysis and comparison of the original flow and the flow field after POD, the main flow structure in the diffuser flow channel 2 is the wake flow vortex shedding γ area. Still, the primary energy area is the low-speed area close to the discharge nozzle after POD. Hence, the main flow structure in the diffuser flow channel is inconsistent with the primary energy area, which proves that it is not comprehensive to analyze the flow loss only from the perspective of flow field analysis. POD has apparent advantages in decomposing flow coherent structures of different scales with different energies. The high energy flow structure can be more clearly clarified through the mode decomposition of POD.

Experimental Study on PIV Measurement and CFD Investigation of the Internal Flow Characteristics in a Reactor Coolant Pump

The nuclear reactor coolant pump (RCP) is the core piece of equipment of a nuclear power plant (NPP). The energy performance and internal flow characteristics of RCPs are revealed by effective measurement methods, which are helpful to understand the flow mechanism of RCPs. The present work is intended to conduct an integrated study based on the energy performance test and Particle Image Velocimetry (PIV) flow-field non-contact measurement of the RCP. In addition, the prediction results of different turbulence models are compared with experimental results in detail. Through energy performance measurement and numerical calculation analysis, it can be found that various turbulence models have the ability to predict the performance of RCPs in engineering applications. At 0.8~1.2 Φd operating conditions, the maximum error is less than 10% and the minimum error is less than 0.1% by analyzing the energy performance of numerical calculations and experimental results. The PIV results show that the velocity of the discharge nozzle varies greatly from right (outlet of diffuser channel 2) to left (outlet of diffuser channel 12) due to different flow structures. Through the qualitative and quantitative comparison of the internal flow field, it can be concluded that, except for the low flow rate, compared with other computational models, the Realizable k-ε model can better predict the internal flow field of an RCP. The reasons for the experimental error and numerical calculation error are analyzed in detail, and the results can provide a reference for forecasting an RCP internal flow field with a special and complex structure.

Deposition behaviour of inclined momentum sediment-laden jet

As wastewater is commonly disposed of in the form of sediment-laden jet from a submarine outfall, the sediment movement when the jet evolves in the ambient water and its final deposition are of great importance to marine engineers. This study aims to investigate the settling mechanism of the sediment from an inclined discharge nozzle and quantify the deposition profile for various jet conditions in the hydrostatic environment through physical experiments and dimensional analysis. In the experimental tests, separate flow visualizations for the fluid and sediment phases are achieved to enable the simultaneous observation of sediment particles and jet fluid movement, through which the analysis of the relationship between the fluid and the sediment movement is carried out. The results show that at locations close to the nozzle (s/D = 5), sediment mean velocity has an inverse relationship with the turbulence intensity while positively correlated with the initial jet momentum. The discharge angle is found to have dominant effect on alternating the sediment velocity profile from symmetrical to asymmetrical. With the newly defined momentum settling length scale lmi, the non-dimensional formulations for deposition rate and accumulated deposition profile involving the nozzle inclination have been validated by the experimental data and are potential to be applied to the prediction of depositional rate and final deposition distribution near the outfall for the full-scale wastewater discharge events.

Application of artificial neural network for the critical flow prediction of discharge nozzle

System thermal-hydraulic (STH) code is adopted for nuclear safety analysis. The critical flow model (CFM) is significant for the accuracy of STH simulation. To overcome the defects of current CFMs (low precision or long calculation time), a CFM based on a genetic neural network (GNN) has been developed in this work. To build a powerful model, besides the critical mass flux, the critical pressure and critical quality were also considered in this model, which was seldom considered before. Comparing with the traditional homogeneous equilibrium model (HEM) and the Moody model, the GNN model can predict the critical mass flux with a higher accuracy (approximately 80% of results are within the ±20% error limit); comparing with the Leung model and the Shannak model for critical pressure prediction, the GNN model achieved the best results (more than 80% prediction results within the ±20% error limit). For the critical quality, similar precision is achieved. The GNN-based CFM in this work is meaningful for the STH code CFM development.

Carbon-13 studies of sulphur-terminated carbon chains: chemical bonding, molecular structures, and formation pathways

The rotational spectra of the singly substituted carbon-13 isotopic species of six sulphur-terminated carbon chains have been detected between 5 and 40 GHz using a supersonic discharge jet source in combination with a cavity Fourier transform microwave spectrometer. These molecules are , a closed-shell isomer of , and five radicals: , , , and . Experiments were carried out with precursors enriched in C, either high purity , a statistical sample of C/C acetylene, or . From the C hyperfine coupling constants, the unpaired electronic density along the chain can be quantified for the radical species, while precise experimental structures () can be derived for each chain except by a least-squares fit to the rotational constants. The use of is particularly revealing in that it provides important clues as to the major formation pathway for each chain in our discharge nozzle. Somewhat surprisingly, C from this precursor appears to be substituted in one of three distinct ways: statistical, a single C site, or not at all. This propensity is molecule specific, implying that multiple formation pathways are operative.

Optimization of CO Turndown for an Axially Staged Gas Turbine Combustor

Abstract This paper reports on an optimization study of the CO turndown behavior of an axially staged combustor, in the context of industrial gas turbines (GTs). The aim of this work is to assess the optimally achievable CO turndown behavior limit given system and operating characteristics, without considering flow-induced behaviors such as mixing quality and flame spatial characteristics. To that end, chemical reactor network (CRN) modeling is used to investigate the impact of various system and operating conditions on the exhaust CO emissions of each combustion stage, as well as at the combustor exit. Different combustor residence time combinations are explored to determine their contribution to the exhaust CO emissions. The two-stage combustor modeled in this study consists of a primary (Py) and a secondary (Sy) combustion stage, followed by a discharge nozzle (DN), which distributes the exhaust to the turbines. The Py is modeled using a freely propagating flame (FPF), with the exhaust gas extracted downstream of the flame front at a specific location corresponding to a specified residence time (tr). These exhaust gases are then mixed and combusted with fresh gases in the Sy, modeled by a perfectly stirred reactor (PSR) operating within a set tr. These combined gases then flow into the DN, which is modeled by a plug flow reactor (PFR) that cools the gas to varying combustor exit temperatures within a constrained tr. Together, these form a simplified CRN model of a two-stage, dry-low emissions (DLEs) combustion system. Using this CRN model, the impact of the tr distribution between the Py, Sy, and DN is explored. A parametric study is conducted to determine how inlet pressure (Pin), inlet temperature (Tin), equivalence ratio (ϕ), and Py–Sy fuel split (FS), individually impact indicative CO turndown behavior. Their coupling throughout engine load is then investigated using a model combustor, and its effect on CO turndown is explored. Thus, this aims to deduce the fundamental, chemically driven parameters considered to be most important for identifying the optimal CO turndown of GT combustors. In this work, a parametric study and a model combustor study are presented. The parametric study consists of changing a single parameter at a time, to observe the independent effect of this change and determine its contribution to CO turndown behavior. The model combustor study uses the same CRN, and varies the parameters simultaneously to mimic their change as an engine moves through its steady-state power curve. The latter study thus elucidates the difference in CO turndown behavior when all operating conditions are coupled, as they are in practical engines. The results of this study aim to demonstrate the parameters that are key for optimizing and improving CO turndown.

Laboratory microwave spectroscopy of the doubly deuterated cyanomethyl radical, D2CCN

The microwave spectrum of the doubly deuterated cyanomethyl radical (D2CCN) in its ground electronic state (2B1) has been observed for the lowest four rotational transitions (NKa,Kc = 10,1–00,0, 20,2–10,1, 21,2–10,1 and 21,1–11,0) using a Fourier transform microwave spectrometer in combination with a pulsed discharge nozzle. A total of 394 hyperfine components were measured and subjected to a least squares analysis which allowed determining twelve hyperfine constants for nitrogen and deuterium nuclei. With this new set of molecular constants we obtained accurate predictions for low N rotational transitions with hyperfine structure, and searched for this species in TMC–1.

Structure modeling and analysis for improving the strength of horizontal pump system

Generally, pumps are used as equipment to move liquids from one place to another, such as in power plants, petroleum companies, etc. One of the kinds of the pump is the Horizontal Pumping System which consists of a motor, trust room, cradle, pump, and base. This study is motivated by the problem appearing of load increase at the suction and discharge nozzle so that it exceeds the allowable load. That load surges cause the pump structure to receive large vibrations, which results in damage to some Horizontal Pump System structures. Therefore, structural analysis on the Horizontal Pumping System to determine the displacement and durability of each cradle are necessary. The purpose of this study is to determine the strength of the pump structure and design additional tools to strengthen the pump structure. In this study, SOLIDWORKS is used for 3D modeling of the Horizontal Pump System structure. Meanwhile, the strength analysis of the structure is conducted using ANSYS Static Structural. Based on the analysis results, there is a quite large displacement in the pump section associated with the suction nozzle. On the other hand, the cradle resistance is still in the elastic deformation area with a maximum value of 24881.97 psi (σy = 3.01x104 psi). Therefore, development is needed by adding a cradle in the pump section associated with a suction nozzle. By adding this cradle there is a reduction in displacement experienced by the pump. Pump displacement changes to 0.036 - 0.097 inches in x-axis, 0.009 - 0.021 inches in y-axis, and 0.001 - 0.005 inches in z-axis.

Droplet Size Distributions of Liquid‐Liquid Dispersions in Centrifugal Pumps

AbstractThe generation of liquid‐liquid dispersions with defined droplet size distributions is an important aspect for process equipment design. In this work, two centrifugal pumps with different impeller diameters were used to generate dispersions at selected operating points for a paraffin oil‐water system. The droplet break‐up phenomena within the centrifugal pumps were analyzed using a transparent pump design in combination with high‐speed imaging. Droplet size distributions at centrifugal pump discharge nozzle were recorded with optical probe measurement technologies and evaluated by means of image processing using a neural network. The influence of impeller diameter, rotational speed, volumetric flow rate and dispersed phase fraction are discussed. Experimental data is correlated using fluid properties, operating data as well as centrifugal pump dimensions. The correlations developed from results of this work serve as a basis for the equipment design of centrifugal pumps.

Experimental test of Water-Oil Emulsion Combustion

This report dwells on the scientific study of the vortical device. The device is designed for efficient combustion of fossil fuels. Oil-water emulsion was taken as an example of alternative fuel. Although the functionality of the burner device is not limited to this fuel only. The innovative burner device under investigation is based on principal of vortical motion of fuel air mixture. There is a precombustion chamber specially designed, where inflammation and partial combustion of the swirling flow takes place. The article describes experiment on defining the geometric dimensioning of the burner discharge nozzle in relation to a combustion chamber. The position of the outlet nozzle inside of the burner is the main input parameter of this research. The authors analyzed the influence of this parameter on the pressure inside the combustion chamber and the electric load of the fan for the supplying combustion air. The position ranged from 0 to 120%. The optimal position is at 50% of the total length of the burner chamber. The pressure graph has an extremum in this position, and the electric energy consumption by the fan changes less significantly with further deepening of the output nozzle than earlier. The Results are presented for cold (air blowing only) and hot experiment (burning). This experiment proved the need for the design of the inner part of the discharge nozzle, which is a design feature of the burner device for which the European patent was obtained. The patent link is presented in the list of references.

Experimental study of electrostatic spray modes of high-flowrate water with horizontal nozzle

Since the introduction of electrostatic spray technology for several decades, it has been configured most frequently with a vertical discharge nozzle. With a recent expansion in application areas, electrostatic spray with a horizontal nozzle has been studied in a narrow range of low volumetric flowrates. In this study, a horizontal discharge nozzle with an upright collector plate is experimented in consideration of its application to electrostatic precipitators. Using a large volumetric flowrate at the scale of milliliters per minute, the operation modes with horizontal nozzle are observed with high-speed digital cameras under different test conditions of nozzle sizes, nozzle-to-plate distances, and volumetric flowrates. The operation modes were classified and compared with the conventional electrostatic spraying modes. From the experiment, it is found that the nozzle diameter and the volumetric flowrate influence the spraying pattern while the applied voltage and nozzle-to-plate distance have a more defined impact on the determination of the modes. A novel spray map diagram was provided according to Reynolds number and electric field intensity. This diagram will serve to predict which modes will occur at certain geometric and flowrate conditions.

Improvement of a discharge nozzle damping attachment to suppress fires of class D

The software package COSMOSFloWorks has been used to study a discharge nozzle damping attachment. A procedure has been proposed to estimate the covering of surface with dimensions of 0.4×0.4 m by a fire-extinguishing powder. It was established that existing discharge nozzle damping attachments are not efficient because at extinguishing light metals they do not effectively reduce the speed of powder supply onto a flammable surface and fan the fire, not being able to cover the burning surface by a fire-extinguishing powder. After putting out the fire the surface that was covered with powder reveals the burnouts. We have modeled the optimal structural parameters for a discharge nozzle damping attachment in order to extinguish fires of class D in the form of a discharge nozzle damping attachment with an elliptical top and a parabolic reflector. It has been proven that a damping attachment with two working surfaces outperforms the previous damping attachment with a single working surface by 30 %. Given this, the fire-extinguishing powder covers the burning surface by a larger layer, preventing the fanning of chips from the surface of a burning metal, thereby shortening the duration of burning and improving the efficiency of a fire-extinguishing powder supply. Experimental study has confirmed that the use of a damping attachment that supplies a fire-extinguishing powder with two working surfaces in order to extinguish fires of class D increases the powder feed to a fire site, reaching above 90 %. The diameter and the shape of the attachment have been determined. The attachment must acquire the form of a diffuser with a diameter of 16 mm. Our development could be used when designing the stationary and portable fire extinguishing systems for light metals and alloys, including incendiary grenades under condition of proper selection of the powder. We have achieved positive results during field tests of the discharge nozzle damping attachment using a make-up fire to burn the shavings of magnesium alloys

The rotational spectrum and potential energy surface of the Ar-SiO complex.

The rotational spectra of five isotopic species of the Ar-SiO complex have been observed at high-spectral resolution between 8 and 18 GHz using chirped Fourier transform microwave spectroscopy and a discharge nozzle source; follow-up cavity measurements have extended these measurements to as high as 35 GHz. The spectrum of the normal species is dominated by an intense progression of a-type rotational transitions arising from increasing quanta in the Si-O stretch, in which lines up to = 12 (∼14 500 cm-1) were identified. A structural determination by isotopic substitution and a hyperfine analysis of the Ar-Si17O spectrum both suggest that the complex is a highly fluxional prolate symmetric rotor with a vibrationally averaged structure between T-shaped and collinear in which the oxygen atom lies closer to argon than the silicon atom, much like Ar-CO. To complement the experimental studies, a full dimensional potential and a series of effective vibrationally averaged, two-dimensional potential energy surfaces of Ar + SiO have been computed at the CCSD(T)-F12b/CBS level of theory. The equilibrium structure of Ar-SiO is predicted to be T-shaped with a well depth of 152 cm-1, but the linear geometry is also a minimum, and the potential energy surface has a long, flat channel between 140 and 180°. Because the barrier between the two wells is calculated to be small (of order 5 cm-1) and well below the zero-point energy, the vibrationally averaged wavefunction is delocalized over nearly 100° of angular freedom. For this reason, Ar-SiO should exhibit large amplitude zero-point motion, in which the vibrationally excited states can be viewed as resonances with long lifetimes. Calculations of the rovibrational level pattern agree to within 2% with the transition frequencies of normal and isotopic ground state Ar-SiO, and the putative K a = ±1 levels for Ar-28SiO, suggesting that the present theoretical treatment well reproduces the salient properties of the intramolecular potential.

A Computational Fluid Dynamic Study for Temperature Uniformity at a Wind Tunnel Outlet with Effects of Heat Transfer along Tunnel Walls

A Computational Fluid Dynamics (CFD) Modelling was carried out to investigate temperature uniformity at a wind tunnel outlet region to benefit its design and construction. Low temperate (110K) nitrogen entered the wind tunnel at inlet, passed through two turning area with 18 turning vanes and went into expansion session, stable session and congestion session, finally towards outlet discharge nozzle session. The model considered static nitrogen isolation layer in physical model and three more isolation layer outside the tunnel as well as possible heat transfer from ambient environment. Two case scenario for supersonic and subsonic at outlet (Mach Number 0.9 and 1.3) were conducted with a uniform temperature imposed at inlet, as well a 3rd case scenario (Mach Number 0.9) with a non-uniform temperature distribution at inlet. Existence of porous zone (to model honeycomb session) and porous interfaces (to model damping interfaces) at the stable session were also included. Contours of temperature and velocity on representative cross sections were presented, and effects of Mach number, total pressure and initial temperature distribution at inlet on temperature uniformity at outlet were discussed. Based on the numerical results, improvement of tunnel geometry for better flow uniformity at outlet regions were also suggested.

Experimental and numerical investigation on the pressure pulsation and instantaneous flow structure in a nuclear reactor coolant pump

Abstract The instantaneous vortical flow structure is one of the typical flow structures inside the nuclear reactor coolant pump (RCP), which would cause the unsteady pressure pulsations, vibrations of the unit and fatigue of components. Due to high safety requirement of the RCP during the actual operation of the nuclear power plants (NPPs), revealing instantaneous nature of vortical flow structure and its pressure pulsation becomes a crucial issue for studying the internal flow mechanism of the RCP. The purpose of this study is to shed comprehensive light on the pressure pulsation and instantaneous vortical flow structure in the RCP by using the experimental method and the numerical simulation method. Based on the result of comparison with the experiment and numerical simulation, it can be considered that the LES method can better identify instantaneous nature of vortical flow structures in the low frequency band. The instantaneous vortical flow structure is attached to the impeller RBPS (rotor blade pressure surface) and transient jet wake vortex flow structures between the impeller and diffuser under the rotor-stator interaction effect are fairly obvious by Q-criterion. On the other hand, in the axial-vorticity component distribution, the rotor-stator interaction effect between the impeller and diffuser cannot be clearly revealed. From the three-dimensional structures, the main vortex structures are in the front and back cavity of the right-hand side near the discharge nozzle and the right-hand side below the discharge nozzle in the spherical casing. Meanwhile, combined with pressure spectrum, it is convinced that their unsteady characteristic is the main reason that causes complex excitation frequencies in the low frequency band of the right-hand side near the discharge nozzle.

Experimental evaluation of temperature rise in centrifugal pumps at partial flow rates

When the centrifugal pumps operate near shut-off condition, different kinds of energy losses happen from inlet to discharge nozzle leading to lower hydraulic performance and overall efficiency. A part of dissipated energy turns into heat and increases the operating liquid temperature. This may seem to be very dangerous when talking about pumping oil or any other flammable chemical liquids. In the present investigation, several centrifugal pumps were selected to perform experimental analysis of measuring temperature rise at inlet and discharge nozzles during part load operation. Pumps were entirely insulated using glass wool to prevent heat leakage from pump casing to the environment and pure water was selected to play as the working fluid. Temperature rise of pumps was reported from start time up to assuaging steady-state condition. Obtained results demonstrated that higher rotational speed of impeller led to higher value of outlet water temperature in a shorter time rather than lower rotational speeds. Steady-state temperature values were used to establish a novel relation for temperature rise that can be implemented for wide range of centrifugal pumps.

Particle image velocimetry measurement of complex flow structures in the diffuser and spherical casing of a reactor coolant pump

Abstract Understanding of turbulent flow in the reactor coolant pump (RCP) is a premise of the optimal design of the RCP. Flow structures in the RCP, in view of the specially devised spherical casing, are more complicated than those associated with conventional pumps. Hitherto, knowledge of the flow characteristics of the RCP has been far from sufficient. Research into the nonintrusive measurement of the internal flow of the RCP has rarely been reported. In the present study, flow measurement using particle image velocimetry is implemented to reveal flow features of the RCP model. Velocity and vorticity distributions in the diffuser and spherical casing are obtained. The results illuminate the complexity of the flows in the RCP. Near the lower end of the discharge nozzle, three-dimensional swirling flows and flow separation are evident. In the diffuser, the imparity of the velocity profile with respect to different axial cross sections is verified, and the velocity increases gradually from the shroud to the hub. In the casing, velocity distribution is nonuniform over the circumferential direction. Vortices shed consistently from the diffuser blade trailing edge. The experimental results lend sound support for the optimal design of the RCP and provide validation of relevant numerical algorithms.