Nozzle Opening Research Articles

Experimental study on aerosol scrubbing efficiency of self-priming venturi scrubber submerged in water pool

Scrubber nozzles are key pieces of equipment used to remove aerosols in a wet-type filtered containment venting system (FCVS). This study deals with the aerosol scrubbing efficiency of a scrubber nozzle operating in self-priming mode. The scrubber nozzle that has been developed in this work consists of a reducer, a throat, a diffuser, a liquid suction slit, and an end cap with a rectangular section area. The aim of this study was to characterize scrubbing efficiency under various thermal hydraulic and aerosol conditions including nozzle inlet pressure (250–600 kPa(g)), nozzle inlet temperature (102–164 °C), nozzle inlet flow rate (air: 42–132 m3/h, steam: 112–269 m3/h), submergence from the nozzle exit (0.7–2.7 m), aerosol size (0.5, 0.7, 3 µm), nozzle inlet aerosol concentration (0.1–3 g/m3), and steam mass fraction in the main carrier gas (0–1). Aerosol scrubbing efficiency was measured based on the inlet and outlet aerosol concentrations of the scrubbing vessel with isokinetic sampling systems including a glass microfiber filter. Experimental results show that the scrubbing efficiency increased with increasing aerosol size, steam mass fraction, nozzle submergence, and inlet aerosol concentration. We also showed that the scrubbing efficiency increased with an increase in inlet pressure at low scrubber nozzle submergence. However, at higher scrubber nozzle submergence, the nozzle inlet pressure did not significantly influence the scrubbing efficiency. The aerosol scrubbing efficiency with the developed self-priming scrubber nozzle submerged in the pool was over 97% for various thermal–hydraulic conditions. Thus, the experimental results can be used to design a wet scrubber system considering upstream conditions such as operation of the FCVS.

High-Speed Additive Manufacturing Through High-Aspect-Ratio Nozzles

The feasibility of layer-by-layer manufacturing through high-aspect-ratio (HAR) nozzles for microextrusion of paste to deposit planes has been investigated. Various conditions for paste extrusion, including nozzle moving speed, piston speed, extrusion rate, and distance between the nozzle tip and substrate, have been evaluated. By linking various microextrusion parameters together with the aid of a critical distance concept derived from microextrusion using circular nozzles and addressing the extrusion delay in response to the change of the piston speed and air pocket problems properly, we successfully microextruded single planes, multilayer objects, and larger planes made of multiple smaller planes side by side through HAR nozzles. It is further demonstrated that the X–Y dimensions of an extruded plane in the steady-state extrusion stage are determined by the nozzle travel distance and the length of the HAR nozzle opening if microextrusion is conducted with proper conditions. However, the height of the extruded plane is not only determined by the microextrusion conditions, but also affected by the drying shrinkage of the paste after microextrusion. This demonstration of the feasibility of using a HAR nozzle machine opens the door to manufacture of multimaterial, multilayer devices with high productivity in the near future.

Modelling of the spray drying process for particle design

Spray drying is widely applied in many industries, such as the pharmaceutical, food, detergents, polymers, to convert liquids in solid particles. However, it still requires continuous innovation in order to provide more sophisticated particles, which are difficult to design by using only empirical approaches. In this context, a steady-state mathematical model for a co-current spray dryer is developed to give a more phenomenological insight in the production of inhalable particles. The model includes mass, energy and momentum balances for both particulate and gaseous phases. Particularly, and as a model inhalable compound, ciprofloxacin hydrochloride (CIP) aqueous solutions are studied. Several experimental data, obtained in a Mini-Spray Dryer B-290, BÜCHI, were available. In addition, droplet size measurements were carried out by using laser diffraction. The effect of the binary nozzle operating conditions on the mean droplet size was analyzed and a correlation to predict the mean Sauter diameter was established. The experimental data are used to fit and validate the proposed model. The validated model is used to perform parametric studies in order to evaluate the effect of the main process variables on the final product properties (e.g., particle size and density, powder moisture content) and to track key powder attributes for pulmonary administration.

Influence of nozzle opening pressure on combustion, performance and emission analysis of waste cooking oil biodiesel fuelled diesel engine

In the present analysis, the combustion, performance and emission of a waste cooking biodiesel fuelled diesel engine were compared with diesel at higher injection pressure. The experiments were performed at different loads and at 2000 rpm speed by varying the nozzle opening pressure. The injection pressure was increased from 225 bar to 235 bar. The start of combustion takes place earlier as the percentage of fuel blend ratio increases which is mainly due to shorter ignition delay. The maximum peak cylinder pressure was lower in biodiesel and its B20 blend. Improvement in brake specific fuel consumption and brake thermal efficiency was observed for B100 and B20 as compared to diesel fuel. CO, HC and smoke opacity were slightly decreased in case of biodiesel and its blend as nozzle opening pressure increases. The very small increase in NOx emission was observed for B100 and B20.

Influence of nozzle opening pressure on combustion, performance and emission analysis of waste cooking oil biodiesel fuelled diesel engine

In the present analysis, the combustion, performance and emission of a waste cooking biodiesel fuelled diesel engine were compared with diesel at higher injection pressure. The experiments were performed at different loads and at 2000 rpm speed by varying the nozzle opening pressure. The injection pressure was increased from 225 bar to 235 bar. The start of combustion takes place earlier as the percentage of fuel blend ratio increases which is mainly due to shorter ignition delay. The maximum peak cylinder pressure was lower in biodiesel and its B20 blend. Improvement in brake specific fuel consumption and brake thermal efficiency was observed for B100 and B20 as compared to diesel fuel. CO, HC and smoke opacity were slightly decreased in case of biodiesel and its blend as nozzle opening pressure increases. The very small increase in NOx emission was observed for B100 and B20.

Rainbow schlieren measurements in underexpanded jets from square supersonic micro nozzles

The slightly underexpanded free jet issued from a supersonic micro nozzle with a design Mach number of 1.5 and a square shape of 1 mm × 1 mm at the nozzle exit has been experimentally investigated using the rainbow schlieren deflectometry combined with the computed tomography where the nozzle operating pressure ratio is held constant at 4.0. Density fields in the free jet obtained from the rainbow schlieren deflectometry are the vortex sheet theory proposed by Tam. It is shown that there is good quantitative agreement between experiment and theory. It is shown that the rainbow schlieren deflectometry is a useful tool for studying the three-dimensional structure of shock containing free jets from micro-scale supersonic nozzles.

Diesel engines equipped with piezoelectric and solenoid injectors: hydraulic performance of the injectors and comparison of the emissions, noise and fuel consumption

A comprehensive comparison between solenoid and indirect acting piezoelectric injectors has been carried out. The working principle of these injector typologies is illustrated, and their hydraulic performance has been analysed and discussed on the basis of experimental data collected at a hydraulic test rig. The injector characteristics, injected flow-rate profiles, nozzle opening and closure delays, injector leakages and injected volume fluctuations with the dwell time have been compared in order to evaluate the impact of the injector driving system.The solenoid and piezoelectric injectors have been installed on a Euro 5 diesel engine, which has been tested experimentally at a dynamometer cell. Optimized double and triple injection strategies have been considered at some representative key points of the New European Driving Cycle. Engine-out emissions, brake specific fuel consumption and combustion noise are presented and discussed, with the support of a three-zone, diesel combustion diagnostic model. The research has focused on the cause-and-effect relationships between the hydraulic performance of the injectors and the results of the engine tests. The primary goal has been to assess if the differences in engine performance between the solenoidal and indirect-acting piezoelectric injector setups are due to the injector driving system or to specific features that are present in the hydraulic circuit of the considered injectors and which are not closely related to the driving system.A final evaluation of the potential of the piezoelectric technology for driving indirect acting injectors is provided on the basis of real engine results.

Numerical investigation of performance, combustion and emission characteristics of various biofuels

Alternative fuels have been a major concern in today’s era due to its promising characteristics in internal combustion engines. The computational analysis is a proven method by many researchers in determining combustion, performance and emission characteristics of an internal combustion engine, offering accurate results at par with experimental results. An attempt is being made by the author(s) in this paper for performing numerical study of nine (9) different alternative biofuels and pure diesel. Comparison has been carried out with the results of pure diesel in a single cylinder, naturally aspirated, water cooled, direct injection diesel engine with different engine load (20%, 40%, 60%, 80% and 100%), constant compression ratio (CR17.5), higher nozzle opening pressure (220 bar) and advance injection timing (23° CA before TDC). The study was performed after validating results of two experimental data using the proposed tool, which have shown that the numerical results were in good agreement with the experimental results. The numerical results of the different biofuels have depicted the possibility of using the fuels as alternative fuel for internal combustion engine.

Numerical Simulation for Prediction of Wetness Content in Wet Steam for Convergent - Divergent Nozzle

This research is to find a wetness using the (laser beam) optical Forward Scattering Method (F.S.M.) which is applicable to calculate the wetness in a convergent-divergent De-Laval steam nozzle operating (1.3 Mach number) which may be works at wet steam with pressure (1) bar and temperature (373) K .The light source of He-Ne laser of wave light (λ=0.632) µm was used to prediction the wetness in nozzle a wet steam flow. Both droplet diameter of water (Dr) and relation of intensity of light S= / are assumed to be (Dr=10,30,50,70,100 µm) and (S = 0.9,.0.8,0.7,0.6,0.5 ) respectively. From the relation of light intensity pattern of many diameter droplet of water (Dr) and different droplet size distribution N (Dr), the MATLAB program can calculate the light attenuation coefficient (Ks) consequently. The increase of the droplet size distribution, N (Dr), leads to decrease the values of (S) and (Ks). The increase of the droplet diameter causes increase of the scattered light, and the minimum value of scattering light is with (Dr= 10µm) for the tested samples. The wetness of steam (yₒ) = (1,3,557,10) % ,which depend on the [Dr, N(Dr)] in the scattered zone can be determined easily by the MATLAB program. The radius of droplet water in two – phase can be adversely calculated by using the research output that then the concentrations or wetness is previously specified.

Numerical Studies on Thrust Augmentation in High Area Ratio Rocket Nozzles by Secondary Injection

Single stage to orbit propulsion devices are being developed as part of low cost access to space endeavors. Sea level operation of high area ratio rocket nozzle used in rocket engines leads to an overexpanded flow condition resulting in high side loads. Secondary injection of propellants in high area ratio nozzle is an attractive option to overcome the inefficiency of operation of such nozzles in sea level conditions in addition to the augmentation of thrust. A numerical study on thrust augmentation in high area ratio nozzle by secondary injection of propellants is presented here. The turbulent compressible reacting flow in rocket nozzle with auxiliary injection is simulated using conservation equations for chemical species based on finite rate chemistry model and compressible Navier-Stokes equations with AUSM+-up upwind scheme based unstuctured finite volume solver. An optimized eight step, six species reduced H2-O2finite chemistry reaction model is used to model the supersonic combustion. The indigenously developed solver has an efficient rescaling algorithm to alleviate the effect of stiffness in conventional explicit algorithm for simultaneous solution of reacting flow. The code is validated using the wall pressure and hydrogen concentration values reported for the similar high area ratio rocket nozzle. Accurate prediction of nozzle performance is possible with present turbulent reacting flow simulation as it take care of all losses in nozzle flow. Extensive computations have been performed for the performance estimation of high area ratio rocket nozzle for various prospective auxiliary injection options.

Surface coating technology for medium density fiberboard

To determine the state of spray nozzle and operational parameters for optimization of coating thickness, a homemade automatic spray paint test device(type of spray gun:WA-101-082P) was used, using polyurethane (PU) wood coatings, with the spraying distance between nozzle and workpiece altered. Also, the nozzle jet direction and angle to the surface of the workpiece were varied along with nozzle operation relative to workpiece speed (Orthogonal experiment L9(34))to 36 block size is 800 mm × 200 mm × 15 mm medium density fiberboard (MDF) test specimen surface spraying process. Then, the surface coating film was measured for film thickness, film surface roughness and performance comparison and a comparative analysis was conducted. Results showed that when the air pressure was 0.28 MPa, the spraying distance was 250 mm, the nozzle angle was 30°, and the running speed was 55 mm·s-1 were optimal conditions for obtaining a thin film thickness and favorable uniformity. With these performance characteristics the coating would perform well.

On flow regime inside plain-orifice nozzle

The plain-orifice is the most common type of atomizer. The flow regime inside plain-orifice nozzle has a tremendous effect on the external spray. At present, the judgement method of the flow pattern is not uniform. The purpose of this study is to numerically investigate the relationship between the change of flow pattern, the ratio of nozzle length and nozzle diameter (L/d), the ratio of nozzle radius of the entrance and nozzle diameter (r/d) in plain-orifice nozzle. The computational fluid dynamics (CFD) code FLUENT was used to perform the numerical simulation of the cavitating flow and hydraulic flip in the nozzles. In this paper, the relationship between the change of flow pattern, r/d and L/d was obtained, and the relation curves between L/d and r/d were plotted, and a new model of flow pattern was obtained. The model established in this paper is more accurate than the empirical model to judge the change of flow pattern. The new model is helpful to modify the existing empirical model. According to the relationship, the researcher can use the method of reasonably adjusting the relationship between the nozzle structure and operating conditions to avoid the generation of hydraulic flip, and to get better atomization effect.

Internal flow characteristics of a variable mixed flow turbine with partially-rotating vane nozzle

Variable nozzle turbine has advantages of improving engine low-speed performance; thus, it is widely applied in internal combustion engines. The present study analyzed the aerodynamic performance, especially the nozzle endwall leakage flow loss of a mixed flow turbine with variable nozzle, using 3D computational fluid dynamic simulation and test validation. Then, a partially-rotating vane nozzle was proposed to reduce the nozzle endwall clearance leakage flow to improve turbine efficiency. The results showed that at small nozzle opening condition, the front-part-vane rotating design can improve turbine efficiency up to 5.95 %, and the efficiency improvement of the rear-part-vane rotating design is approximately 5.08 %. At large nozzle opening condition, the front-part-vane rotating design has the same efficiency and flow capacity as the origin design, but the rear-part-vane rotating design cannot satisfy the flow capacity requirement. Detailed flow field analysis shows that the front-part-vane rotating design affects the velocity distribution at the rotor inlet due to nozzle endwall leakage flow. The leakage flow between the front part and the rear part of the nozzle causes a pressure jump at the pivoting axis.

Exploitation of injection fusion strategies in diesel engines equipped with solenoid injectors

Pilot–main injection strategies are investigated in the short dwell-time range at medium load and speed conditions for a low-temperature combustion diesel engine endowed with indirect-acting solenoid injectors. Dwell-time sweeps have been carried out for pilot injections with different energizing times under steady-state working conditions and constant combustion phasing. The experimental results on the engine are combined with in-cylinder analyses of pressure, heat release rate, temperature and emission time histories. As the electric dwell time is reduced toward zero, combustion noise reaches a minimum at a dwell time of 120–140 µs, and a reduction of 1–4.5 dB is possible compared to levels at dwell time = 500 µs. This decrease in combustion noise is obtained in conjunction with a local reduction in engine-out nitrogen oxide emissions, but penalties occur for engine-out soot emissions and brake-specific fuel consumption. The pilot and main injection shots feature fusion phenomena at the shortest dwell-time values, thus giving rise to rate-shaped single injections, which resemble the boot-shaped profiles in direct-acting piezoelectric injectors. The increase in the velocity of the needle, which occurs during the nozzle opening phase pertaining to the main injection for closely coupled injections as dwell time is reduced, is shown to be not the primary cause responsible for the observed trends in combustion noise and soot emissions as dwell-time changes. The combination of simulation and experimental data supports the theory that the main injection interacts with the pilot mixture field: the relative phasing between pilot and main combustion and the in-cylinder equivalent ratio distribution are the dominant aspects in the definition of the engine performance in the short dwell-time range.

Pulsed fusion space propulsion: Computational Magneto-Hydro Dynamics of a multi-coil parabolic reaction chamber

Pulsed fusion propulsion might finally revolutionise manned space exploration by providing an affordable and relatively fast access to interplanetary destinations. However, such systems are still in an early development phase and one of the key areas requiring further investigations is the operation of the magnetic nozzle, the device meant to exploit the fusion energy and generate thrust. One of the last pulsed fusion magnetic nozzle design is the so called multi-coil parabolic reaction chamber: the reaction is thereby ignited at the focus of an open parabolic chamber, enclosed by a series of coaxial superconducting coils that apply a magnetic field. The field, beside confining the reaction and preventing any contact between hot fusion plasma and chamber structure, is also meant to reflect the explosion and push plasma out of the rocket. Reflection is attained thanks to electric currents induced in conductive skin layers that cover each of the coils, the change of plasma axial momentum generates thrust in reaction. This working principle has yet to be extensively verified and computational Magneto-Hydro Dynamics (MHD) is a viable option to achieve that. This work is one of the first detailed ideal-MHD analysis of a multi-coil parabolic reaction chamber of this kind and has been completed employing PLUTO, a freely distributed computational code developed at the Physics Department of the University of Turin. The results are thus a preliminary verification of the chamber's performance. Nonetheless, plasma leakage through the chamber structure has been highlighted. Therefore, further investigations are required to validate the chamber design. Implementing a more accurate physical model (e.g. Hall-MHD or relativistic-MHD) is thus mandatory, and PLUTO shows the capabilities to achieve that.

Experimental and artificial neural network based prediction of performance and emission characteristics of DI diesel engine using Calophyllum inophyllum methyl ester at different nozzle opening pressure

The present work investigates the effect of varying Nozzle Opening Pressures (NOP) from 220 bar to 250 bar on performance, emissions and combustion characteristics of Calophyllum inophyllum Methyl Ester (CIME) in a constant speed, Direct Injection (DI) diesel engine using Artificial Neural Network (ANN) approach. An ANN model has been developed to predict a correlation between specific fuel consumption (SFC), brake thermal efficiency (BTE), exhaust gas temperature (EGT), Unburnt hydrocarbon (UBHC), CO, CO2, NOx and smoke density using load, blend (B0 and B100) and NOP as input data. A standard Back-Propagation Algorithm (BPA) for the engine is used in this model. A Multi Layer Perceptron network (MLP) is used for nonlinear mapping between the input and the output parameters. An ANN model can predict the performance of diesel engine and the exhaust emissions with correlation coefficient (R2) in the range of 0.98–1. Mean Relative Errors (MRE) values are in the range of 0.46–5.8%, while the Mean Square Errors (MSE) are found to be very low. It is evident that the ANN models are reliable tools for the prediction of DI diesel engine performance and emissions. The test results show that the optimum NOP is 250 bar with B100.

Assessing low-pressure solid-set sprinkler irrigation in maize

Water and energy are limited and expensive resources. Conserving water and energy is a requirement to ensure the viability of modern pressurized irrigation systems. The objective of this research was to analyze the possibilities of reducing the nozzle operating pressure of impact sprinklers from 300kPa (standard pressure) to 200kPa (low pressure) in solid-set irrigation systems without reducing the sprinkler spacing and maintaining crop yield. Three treatments resulting from combinations of sprinkler type, and working pressure were analyzed: 1) Conventional impact sprinkler operating at 300kPa (CIS300); 2) Conventional impact sprinkler operating at 200kPa (CIS200); and 3) Modified deflecting plate impact sprinkler operating at 200kPa (DPIS200). A randomized experimental design was applied to a maize crop during two seasons (2015 and 2016). Irrigation performance was measured by catch-can monitoring at one replicate of each treatment. Maize growth, yield and its components were measured. Differences between treatments in soil water, maize growth and yield variables were analyzed using ANOVA. Seasonal irrigation uniformity evaluated at the top of the canopy was larger for the standard pressure treatment (93%) than for the low pressure treatments (82% and 84% for DPIS200 and CIS200, respectively). The average wind drift and evaporation losses for the 2016 irrigation season were higher for the CIS300 treatment (17%) than for the low pressure treatments, DPIS200 (15%) and CIS200 (13%). Low pressure treatments did not reduce grain yield compared with the standard pressure treatment. Differences in irrigation performance and maize yield between the low pressure treatments, DPIS200 and CIS200, were not statistically significant. The reduction in energy use by reducing the operating pressure from 300kPa to 200kPa would allow to increase the net farming benefit of individual and collective systems. This is particularly true if low pressure irrigation is considered at the design phase of the irrigation system.

Zonal Detached Eddy Simulations of a Dual-Stream Jet: Turbulence Rate Sensitivity

This paper investigates the effect of turbulence injection using the random flow generation technique at the inlet boundaries of the core and fan channels of a dual-stream nozzle with an external plug. The objective is to reproduce the turbulence rate at the center of the nozzle ducts’ exhaust. The nozzle design and operating conditions are typically those of an aircraft engine at cruise, although the external flow is not simulated. The paper focuses on the effects of the nozzle exhaust turbulence characteristics, namely turbulent length scales and turbulent rate, on the jet flow prediction and the mixing-layer development. The results are discussed in terms of Reynolds-averaged data and spectral content. Turbulence injection over the whole height of the nozzle ducts accelerates the Reynolds-averaged Navier–Stokes to large-eddy simulation transition in both external and internal mixing layers, which is in better agreement with the experimental results. The transition length is further reduced when the injected turbulent ratio is higher but also when the injected turbulent length scale is smaller. Of interest, the shock-cell positioning in the fan jet is also improved using random flow generation, which emphasizes the importance of accounting for upstream turbulence for this type of simulation.

Passive scalar mixing studies to identify the mixing length in a supersonic confined jet

Supersonic jet with a co-flow, closely bounded by walls is known as supersonic confined jet. Supersonic confined jet is encountered in practical devices like the supersonic ejector. Mixing of the primary and the secondary fluid inside the confined passage is complex. From a design perspective, it is necessary to have an accurate knowledge of the mixing length (L-MIX). Tracers that do not actively participate in the flow behavior but rather mark the fluids such that they faithfully follow the fluid motion are known as passive scalars. Passive scalars help in the understanding the progression of mixing amidst interacting flows. In this work, we have performed passive scalar mixing studies in a supersonic confined jet for different operating conditions using an existing low area ratio (AR = 3.7) rectangular supersonic gaseous ejector. Air is used as the working fluid in both the primary and the secondary flow. The design Mach number of the primary flow nozzle (M-PD = 1.5-3.0) and the total pressure of the primary flow (P-OP = 4.89-9.89 bar) are varied during the experiments. Using the planar laser-induced fluorescence (PLIF) technique and acetone as the passive scalar, L-MIX is determined. A 266 nm Nd-YAG laser with a repetition rate of 8 Hz is used to excite the acetone molecules in the flow field, and the emitted fluorescence is captured by an ICCD camera. A new method is proposed to study the passive scalar distribution from the acetone PLIF images through digital image processing. Spatial Scalar Fluctuations Intensity (SSFI or psi ) is a parameter defined at every transverse section along the flow direction. Based on the variation of psi along the jet, the location of L-MIX can be identified. L-MIX is defined as the length from the supersonic nozzle exit where psi first attains a value of 0.05. For the first time, L-MIX is quantified in a supersonic confined jet. L-MIX values are observed to be in the range of 3H to 6H for the cases under study, where H is the height of the confined passage. The behavior of L-MIX is closely dependent on the nozzle operating conditions. The values of L-MIX are found to be reduced by 17.67% for the over-expanded flows and increased by 15.76% for the under-expanded flows from the perfectly expanded condition. This study also provides other supersonic confined jet characteristics like the potential core length (L-PC) and the shock cell spacing (S-x) of the primary supersonic jet. Compared to the supersonic free jet, values of L-PC and S-x are found to be different in the supersonic confined jet.

Numerical and experimental studies of aggregate blocking in mortar extrusion

Numerical and experimental study of aggregate blocking in extrusion of mortar is presented. The studied system consists of a pipe with a nozzle at the tip. Fresh mortar is modeled by composite particles consisting of hard-core representing a sand particle surrounded by soft-shell layer representing interstitial cement paste. For the experimental study, two kinds of mortars are studied. The first kind is a mortar composed of monosized glass beads. This mortar is used for comparison with numerical results. The second kind of mortar is more realistic, polydispersed particles are used by replacing glass beads by standard sand. The effects of the dimension of the bottom nozzle opening, the rheological properties of the cement paste and the paste volume proportion on the blocking of mortar are studied both experimentally and numerically. For mortars composed of monosized beads, experiments and simulations both show that the main parameter governing aggregate blocking is the ratio ‘a’ between the bottom opening diameter of the nozzle and the beads diameter. Rheological properties of the paste and paste volume proportion are less influential. Experimental results obtained on both kinds of mortar confirm the limit ratio ‘a’ identified numerically in all the cases, except for the lower cement paste volume proportion (0.54 in our study) for which ‘a’ has to be slightly increased to avoid blocking.