Adjustable Nozzle Research Articles

Влияние коэффициента избытка воздуха при горении на показатели напряженности двухтактного дизеля в широком диапазоне режимов

The article describes the specific features of the forced diesel engines operating on a helical characteristic. One of them is a decreasing coefficient of excessive air during combustion with a decreasing power. Reducing the air charge of the cylinder and its available work require a greater cyclic supply of fuel to provide a given power, which affects the engine efficiency. It is possible to increase the boost pressure and the mass of the air charge of the cylinder by acting on the adjustable nozzle apparatus of a turbo-charging unit. In this case, gas parameters significantly change over the diesel cycle, which leads to changes in the indicators of thermal and mechanical tension. There have been presented the results of theoretical studies of indicators and criteria of thermal and mechanical tension of a marine two-stroke internal combustion engine operating in a wide range of modes with a constant coefficient of excessive air during combustion. Direct control of air flow at shared load modes was performed by turning the blades of an adjustable nozzle apparatus of a turbo-charging unit. The study of a diesel engine was carried out theoretically for two options: the original version (without adjustable nozzle unit) and under direct control of the air flow using an adjustable nozzle unit; the results were processed depending on the relative power of the diesel fractional load modes. There have been illustrated the graphs of dependence of the blade rotation angle of the nozzle apparatus of a turbocharging unit, relative change of the gas temperature behind the cylinder, cycle average temperature of the working fluid, average heat flux, relative change in the heat stress criterion of the piston, heat stress criterion for the cylinder, change in the pressure cycle of the working fluid, degree of increase working fluid during combustion, maximum rate of pressure rise depending on the load of the diesel engine.

Design and off-design optimisation of an organic Rankine cycle (ORC) system with an integrated radial turbine model

This paper investigates the design and thermodynamic optimisation of both sub- and transcritical organic Rankine cycle (ORC) power systems featuring radial turbines via performance calculations using mean-line models. The emphasis is on rapid performance predictions for a given turbine geometry, as well as geometric optimisation for a given heat source. From three specified quantities, which are the turbine inlet temperature, inlet pressure and mass flow rate, the other flow properties (e.g., outlet pressure and temperature) are computed, together with derived quantities which are required for cycle- or system-level assessments, such as the isentropic efficiency of the turbine. Experimental investigations from the open literature suitable for validation purposes are summarised and analysed with respect to their strengths and weaknesses. Similar computational fluid dynamic (CFD) simulations are also used to complement the available experimental data. The main contributions of this paper are that it provides a comprehensive overview of radial turbine performance modelling, and that it proposes a detailed framework that can be used for the improved development of efficient thermodynamic power systems based on a unified mean-line model that is validated against experimental data and supported by CFD results. Specifically, predictions from the mean-line model show good accuracy over a wide range of operating conditions for different turbine designs and fluids with compressibility factors from 0.6 to 1.0. Finally, in order to demonstrate its efficacy, the integrated radial turbine and ORC system design framework is used in a case study of a nominally 400-kW power system with propane as the working fluid in low-grade waste-heat application, where the turbine inlet temperature is fixed at 150 °C and the condenser temperature is fixed at 15 °C. The novelty of this work arises from the optimisation of the turbine nozzle vane position at off-design conditions. This feature, along with multi-stage radial turbine designs are shown to allow high-performance operation over a wide range of off-design conditions. Specifically, good efficiencies are demonstrated over a wide range of heat-source fluid flow rates when employing an adjustable nozzle geometry, as is the ability of radial turbines to achieve efficiencies that are not constrained by the pressure ratio across them by replacing single-stage designs with multi-stage designs.

Анализ эксплуатационных характеристик дизеля 7S50MC при непосредственном управлении расходом воздуха

The paper provides a theoretical analysis of the operational performance of a marine two-stroke diesel engine in a wide range of modes, operating on a helical characteristic. Reducing the diesel load causes a decrease in the coefficient of excess air for combustion, which is characteristic of two-stroke diesel engines with a relatively high boost pressure. To control the air flow rate, it is proposed to use an adjustable nozzle apparatus as part of a turbine of a turbocharger unit. Changing the angle of the blades of an adjustable nozzle apparatus by turning them, an impact was made on the characteristics of the turbine, compressor and, accordingly, on the operational performance of the diesel engine. With decreasing the angle of the blades of the nozzle apparatus, the effective passage area of the turbine of the turbo-charging unit decreases. This causes an increase in gas pressure in front of the turbine and, consequently, an increase in the power of the turbine and compressor. This increases the boost pressure and the available work of the air charge of the cylinder. The engine operates with a large excess air ratio for combustion and increased efficiency. There are presented the results of a comparative analysis of diesel performance caused by rotation of the blades of an adjustable nozzle apparatus and the initial version, in which the angle of the blades of the nozzle apparatus remained unchanged. The angle of rotation of the blades was selected in such a way as to ensure unchanged the coefficient of excess air for combustion in all the studied diesel operation modes. The studies showed a considerable improvement in the performance of a two-stroke diesel engine at shared load modes when using an adjustable nozzle apparatus of a turbo-charging unit.

Design of a Continuous Pellet Fueling System for Wendelstein 7-X

A continuous pellet fueling system (CPFS) is currently being designed at the Oak Ridge National Laboratory (ORNL) for the long pulse operation of the Wendelstein 7-X (W7-X) stellarator. The purpose of the CPFS is to provide deep continuous fueling for feedback-controlled high-density operation and mitigation of predicted hollow density profiles. The system will provide the capability to inject cylindrical pellets of solid hydrogen or deuterium into the plasma core, with flexibility to vary the pellet size, velocity, and injection frequency. Pellets are nominally of 3 mm in diameter and have a length between 1 and 4 mm. The heart of the CPFS is a vertically oriented, twin-screw extruder, cooled by three Gifford-McMahon cryocoolers in parallel, designed to form a continuous filament of hydrogen or deuterium. The filament width, which determines the pellet length, can be adjusted by means of a variable nozzle driven by a linear actuator at the base of the extruder. Coupled to the nozzle is a solenoid-operated gas gun and cutter assembly. A pneumatic propellant valve pulses a burst of ~60 bar helium to accelerate the cut pellet into W7-X. Three gaps in the guide tubes provide pumping locations to remove the helium propellant before it reaches the plasma. The maximum velocity of the pellet is limited by its ability to survive navigating the guide tube trajectory intact. A microwave cavity located within the guide tube provides the capability to measure the pellet size and velocity. The mechanical and thermal designs of the W7-X extruder, adjustable nozzle, and gun and cutter assembly design are described. A guide tube design and experimental pellet survivability test results are presented.

CFD simulation of vortex flashing R134a flow expanded through convergent-divergent nozzles

Vortex control is a novel two-phase convergent-divergent nozzle restrictiveness control mechanism. The flow control is achieved by adjustable nozzle inlet vortex strength. The underlying mechanism behind vortex control is still unclear. In this study, 3D CFD simulations of vortex flashing R134a flows in convergent-divergent nozzles have been conducted. Good agreement was found between the simulation and experimental results. When there is no vortex applied, the void fraction at the nozzle center remains low. When the vortex is applied, vapor bubbles are driven towards the nozzle center. The applied vortex significantly increases the interphase mass transfer near the nozzle outlet with more uniform interfacial area per unit volume and better utilization of liquid superheats at the nozzle center for evaporation. Thus, after the introduction of inlet vortex, more vapor is generated in the divergent part of the nozzle. As a result, the pressure drop across the divergent part of the nozzle is increased. There is negligible vapor content upstream of the throat even though the pressure is already below saturation pressure. When the inlet vortex is applied, with elevated pressure at the nozzle throat and constant inlet conditions, the pressure difference across the nozzle convergent part decreases and therefore the nozzle mass flow rate is reduced. The overall nozzle outflow mass flow averaged axial velocity can be increased by 30.1%, nozzle isentropic efficiency increases from 37.7% to 63.8% and nozzle mass flow rate drops from 16.0 g s−1 to 12.6 g s−1 when inlet vortex is introduced.

Natural Frequency Sensitivity Analysis of Fire-Fighting Jet System with Adaptive Gun Head

The gun head is the end effector of the fire-fighting jet system. Compared with a traditional fixed gun head, an adaptive gun head has the advantages of having an adjustable nozzle opening, a wide applicable flow range, and a high fire-extinguishing efficiency. Thus, the adaptive gun head can extinguish large fires quickly and efficiently. The fire-fighting jet system with an adaptive gun head has fluid-structure interaction and discrete-continuous coupling characteristics, and the influence of key design parameters on its natural frequencies needs to be determined by a sensitivity analysis. In this paper, the dynamic model and equations of the jet system were established based on the lumped parameter method, and the sensitivity calculation formulas of the natural frequency of the jet system to typical design parameters were derived. Natural frequencies and mode shapes of the jet system were determined based on a mode analysis. The variation law of the sensitivity of the natural frequency of the jet system to typical design parameters was revealed by the sensitivity analysis. The results show that the fluid mass inside the spray core within a certain initial gas content is the most important factor affecting the natural frequency of the jet system. There was only a 0.51% error between the value of the first-order natural frequency of the jet system determined by the modal experiment and the theoretical one, showing that good agreement with the first-order natural frequency of the jet system was found. This paper provides a theoretical basis for the dynamic optimization design of the adaptive gun head of the fire water monitor.

Study of aerodynamics of the jet spreading over cylindrical surface

The purpose of this work is to study the fields of average values of velocity in a turbulent air jet propagating along a smooth cylindrical surface with an adjustable nozzle width being b, the curvature parameter SR and Re number on both convex and concave surfaces. To identify basic patterns of physical phenomena occurring in the boundary layer, it has been established that in universal coordinates, the wall velocity profiles have a universal nature in the region of a change in the curvature parameter 0 ⩽ SR ⩽ |±0.12|, and virtually coincide with the velocity profiles of a turbulent boundary layer on a flat plate in a uniform flow past, except for the velocity peak region. This is due to the fact that the longitudinal pressure gradient is 104 ÷ 105 times lower than transverse pressure gradient. According to our data, it has been established that the excess static pressure near the streamlined surface with a distance from the nozzle and an increase in jet thickness can reach up to 30–40% of the velocity head.

Experimental investigation into the influence of vortex control on transcritical R744 ejector and cycle performance

Vortex control over a diphasic convergent-divergent nozzle through adjustable nozzle inlet vortex can improve the performance of transcritical R744 ejector cooling cycle due to its potential for flow control with less sacrifice of nozzle efficiency and no requirement of geometry change. In this study, the influence of vortex control on transcritical R744 ejector and cycle performance has been experimentally investigated. Vortex control was applied to ejectors with different geometric parameters. The results with vortex control were compared with those with series expansion valve control and needle control. Design guidelines for ejector with vortex control were provided. It was found that the total work recovery efficiency of ejector with vortex control can be better than series expansion valve control and is close to needle control. Vortex control can be used to improve system performance by adjusting the high-side pressure of the transcritical R744 ejector cycle. Under off-design conditions, system capacity and COP can be improved by 11.0% and 8.1%, respectively, by applying vortex control.

Measurement of static pressure profiles of vortex flashing R134a flow expanded through convergent–divergent nozzles

Vortex control is a novel two-phase convergent–divergent nozzle restrictiveness control mechanism which achieves flow control by adjustable nozzle inlet vortex strength. It can potentially provide flow control with less sacrifice of nozzle efficiency, which is important for two-phase ejector cooling cycle performance. It is also less vulnerable to clogging. However, the underlying mechanism behind vortex control is still unclear. In this study, static pressure profiles of vortex flashing R134a flow expanded through nozzles under various conditions have been measured. A 1D model for the estimation of vapor qualities in the initially subcooled flashing nozzle flow based on the measurement results was also developed. It was found that after the introduction of inlet vortex to the initially subcooled flashing nozzle flow, the pressure drop across the divergent part has been increased, which is caused by the increased vapor generation in the divergent part. The elevated nozzle throat pressure results in the nozzle behaving like being more restrictive. When the inlet vortex is applied to flashing nozzle flow with two-phase at the nozzle inlet or single-phase liquid nozzle flow, the influence of inlet vortex on the nozzle restrictiveness and the nozzle pressure profile is insignificant. The nozzle isentropic efficiency can be significantly increased by applying inlet vortex, which could be beneficial to ejector performance when the vortex nozzle is used in ejectors. In order to achieve satisfactory vortex control range and high nozzle isentropic efficiency, the vortex nozzle divergent part length as well as the divergent angle need to be appropriately sized.

Fabric Moisture Uniform Control to Study the Influence of Air Impingement Parameters on Fabric Drying Characteristics.

Impinging dryness is now a widely used and effective way for fabric drying due to its high heat and mass transfer coefficient. Previous studies on fabric drying have neglected the contributions of moisture uniformity and diffusion coefficient to the drying process; though, they have recently been shown to have a significant influence on drying characteristics. This report outlines a step-by-step procedure to investigate the effects of air impingement parameters on a fabric's drying characteristics by controlling the uniformity of its area moisture distribution. A hot air blower unit equipped with an angle adjustable nozzle is used to generate air flow with different velocities and temperatures while the drying process is recorded and analyzed using an infrared thermograph. In addition, a uniform padder is adapted to ensure the fabric's moisture uniformity. Impinging drying is studied under different initial conditions by changing the air flow temperature, velocity, and direction, then the applicability and suitability of the protocol are evaluated.

Application of the addition of ionic liquids using a complex wetting agent to enhance dust control efficiency during coal mining

This study investigates the effects of a compound method that involves the use of anionic, cationic and nonionic surfactants. The compound composition of the isotropic ionic and compound across of the anisotropy ionic process was proposed. An ionic liquid was introduced as an auxiliary agent to improve wetting characteristics of the mixture, resulting in a compound of wetting agent A～I. Wetting agent A and E were selected because they were more effective than others by the capillary rise method. The contact angle on Da Ning coal sample was tested. For droplets of pure water, the contact angle was 72.1°. For droplets of wetting agent A, the contact angle was 23.5°. For droplets of wetting agent E, the contact angle was 14.4°. The effect of wetting ability for the wetting agents were analyzed, and four other coal sample test results were compared. In order to test the application effect of the wetting agents. The high-pressure spray system were analyzed and developed, an adjustable nozzle and wind scooper were designed with a secondary atomization function, which improved the ability to capture dust. The application results showed that the ionic liquid improved the dust effect. The atomization effect of the circular nozzle was better than that of ellipse nozzle. When wetting agent E was added, the dust efficiency reached 90%, and the respiratory dust efficiency reached 87%. The new spray system consumes 30% less water than a traditional system, produces smaller droplets, and achieves higher dust control efficiency.

Study on mechanism of layered water injection by pressure pulse control

In this paper, the simulation analysis of layered waterflood is performed by software and the basic theory is used to verify the analysis. The simulation result data is analyzed and a reasonable control scheme is developed. According to the law of signal transmission and pressure pulse wave generation and change, it is coded so that the pulse signal is decoded by the pressure sensor as an instruction command that can be executed, and the water nozzle is changed by controlling each adjustable nozzle to execute the corresponding instruction. Opening size, and then achieve stratified water distribution.

Structural and regulating characteristics of adjustable annulus-clearance nozzle used in supercritical fluid precipitation

A new type of adjustable nozzle with an annulus clearance between the surfaces of a revolved solid and the matched hole was analyzed, which contained matching parts, regulating parts, guiding elements, and sealing part. The general regulating function of the adjustable nozzle was derived and the regulating and matching characteristics were also analyzed. Through the analysis, it was concluded that the matching-profile curve of either the revolved body or matched hole should be chosen as a straight line in order to keep the linear regulating feature. Moreover, the multi-annulus-clearance nozzle was designed, and some experiments were carried out on preparing budesonide particles with the nozzle. According to the experimental results, it was proved that the annulus nozzles is practical in preparing micro-particles by supercritical fluid precipitation method.

Ejector performance analysis under overall operating conditions considering adjustable nozzle structure

The variable-geometry ejector (VGE) is feasible for unstable heat-source utilization; the ejector can be adjusted to its design point to obtain high efficiency. Moreover, as the adjustable nozzle in the VGE significantly affects the performance of the ejector, a theoretical model is necessary to evaluate VGE performance. In this study, a two-dimensional theoretical model was proposed based on an adjustable-nozzle theory. Method of characteristics was employed to accurately predict the driving-flow development in the mixing section. In addition, the suction-flow velocity distribution on the effective area was considered. The proposed model was validated by employing the data from literature and additional experimental data obtained from a VGE test setup using R134a. The validation result shows that the proposed model predicts the ejector performance accurately; moreover, the model is more adaptive while the nozzle configuration changes. The theoretical model, proposed herein, is practical for the design and application of the VGE.

SPRAY DRIFT AND PEST CONTROL FROM AERIAL APPLICATIONS ON SOYBEANS

Pesticide drift is an issue in modern farming, mainly for crops under constant spraying as soybeans. This study aimed at assessing drift and pest control for aerial application on soybean crops. Hydraulic nozzles and rotary atomizers, regulated to a wide spectrum of droplet sizes, sprayed thiamethoxam and lambda-cyhalothrin using an agricultural aircraft Ipanema 202A at volume rate of 20 L ha-1. Treatments consisted of testing two devices: a rotary cage atomizer (Micronair AU 5000) with blade angles of 65° for larger droplets, and with angle of 55° for smaller ones; and a set of adjustable nozzles (Stol model) with deflector angle of 90° for smaller droplets, and with angle of 30° for larger ones. Drift was evaluated through quantification of active ingredient, by means of liquid chromatography, on nylon strands set 20, 40, 80, 160 and 320 m away from target area, following wind displacement. Control efficiency was measured by counting caterpillars and stinkbugs found five days after spray. Rotary atomizers produced less drift compared to adjustable nozzles at the designed setting. Furthermore, drift can be reduced through a suitable regulation of the devices, keeping an effective pest control.

Analytical Study of Articulating Turbine Rotor Blade Concept for Improved Off-Design Performance of Gas Turbine Engines

Gas turbine engines are generally optimized to operate at nearly a fixed speed with fixed blade geometries for the design operating condition. When the operating condition of the engine changes, the flow incidence angles may not be optimum with the blade geometry resulting in reduced off-design performance. Articulating the pitch angle of turbine blades in coordination with adjustable nozzle vanes can improve performance by maintaining flow incidence angles within the optimum range at all operating conditions of a gas turbine engine. Maintaining flow incidence angles within the optimum range can prevent the likelihood of flow separation in the blade passage and also reduce the thermal stresses developed due to aerothermal loads for variable speed gas turbine engine applications. U.S. Army Research Laboratory (ARL) has partnered with University of California San Diego and Iowa State University Collaborators to conduct high fidelity stator–rotor interaction analysis for evaluating the aerodynamic efficiency benefits of articulating turbine blade concept. The flow patterns are compared between the baseline fixed geometry blades and articulating conceptual blades. The computational fluid dynamics (CFD) studies were performed using a stabilized finite element method developed by the Iowa State University and University of California San Diego researchers. The results from the simulations together with viable smart material-based technologies for turbine blade actuations are presented in this paper.

Analysis of Cruising Fuel Conservation Capabilities of Multi-Mode Engine with the Third Contour

Based on the analysis results from the patent search and review of domestic and foreign publications in variable cycle engines (VCE) was created a classification of the possible schematic diagrams of VCE realizing three-stream engine technologies (the adaptive low pressure compressor (LPC) with air extraction behind stages, FLADE compressor, various feeding types of extraction air to the flowing path of the engine, etc.). To estimate a three-stream engine application as a part of the power-plant (PP) efficiency, was chosen an adaptive LPC technology scheme with the third contour air bypass beyond the critical section of a basic jet nozzle for which a mathematical model (MM) of the PP has been created on the basis of one-dimensional MM of the engine. The MM of the PP included 3D modeling results of the air inlet, the LPC with various air extractions to the third contour, and the jet nozzle taking into account the interaction between the basic stream and the third contour stream. The predicted performance of an air inlet have been used to estimate the changes in a total pressure restoration coefficient and an additional resistance coefficient along «a fluid contour» when air extraction is included in the third contour in several cruiser modes of flight. An integrated characteristic of the LPC has been received at various points and levels of air extraction to the third contour, and parameters of extracted air (depending on the point and amount of air extraction, and also on the fan operating mode) have been calculated. When analyzing the obtained calculation results, the effect of pressure lines displacement to the right (towards the large reduced rates), growth of efficiency values, and also position displacement of its maximum value to the left (towards the descent reduced rates) has been found. To estimate how air extraction of the third contour between the plates of an adjustable supersonic nozzle impacts on its aft deck resistance various parameters of the flowing out air in subsonic cruiser mode of flight have been calculated. As a result of calculations according to the PP MM, under near-the-earth conditions of the subsonic cruiser flight, the effective specific fuel consumption has been reduced by 12,5 %. The results reached allow us to expect significant subsonic effective fuel conservation of the three-stream engine. To prove the calculated results it is further necessary to achieve them under full-scale conditions using the engine-demonstrator.

A 3D printed microliquid jet with an adjustable nozzle diameter.

Microliquid jets have many applications, in particular in the fields of spectroscopy/analysis of samples susceptible to beam damage. Herein, we report a microliquid jet, manufactured with 3D printing technology, with a tuneable nozzle diameter output. This strategy increases the breadth of techniques that can be covered with a single microliquid jet.

Research on the Application of Adjustable Disc Type Nozzle Valve on Wellhead

For the reality of the variable pressure in the oil field, an adjustable disk choke valve is introduced in this paper. The structure and working performance of the valve is described in detail, too. The field application of the valve shows that the valve has such advantages as simple structure, quickly facilitate, easy installation and cleaning, long service life, safe and reliable, all these leads to the broad application prospect of the valve.

Numerical and experimental investigation on nozzle parameters for R410A ejector air conditioning system

The experimental and numerical study on R410A air conditioning system with two-phase ejector were presented in this paper. An adjustable liquid–gas ejector based on a two-phase flow simulation model was designed and manufactured for experiment in the R410A air conditioning system. Both throat diameter (Dnt) and position (Dnm) of nozzle were studied under the given conditions. The experimental results showed that Dnt of 1 mm and Dnm of 4 mm yielded the best ejector efficiency and system EER. Nozzles with different Dnt and the adjustable ejector were also studied under different conditions. The experimental results showed that the ejector with adjustable nozzle can meet the requirements of different operation conditions. It was very useful for the future application of ejector in the air conditioning system.