Adjustable Nozzle Research Articles

Expansion of the range of permissible loads of a marine four-stroke diesel engine when using an adjustable turbocharger nozzle apparatus

The paper analyses the influence of the adjustable turbocharger nozzle apparatus on the parameters and criteria determining the thermal and mechanical stress of the main marine four-stroke diesel engine. The methodology of construction of limiting characteristics of mechanical and thermal stress using approximation dependences of parameters and criteria obtained by calculation-theoretical method is developed. The main parameters limiting the range of maximum permissible diesel engine loads on mechanical and thermal stress in the initial variant and in the variant with adjustable nozzle apparatus are revealed. It is established that the increase in the angle of rotation of blades of the adjustable nozzle apparatus up to the maximum permissible value causes a decrease in the parameters of thermal stress, as a result of which the zone of maximum permissible modes of operation of the diesel engine expands. At the same time, the parameters and criteria determining the mechanical stress of the diesel engine increase, but the reduction of the zone of maximum permissible loads on mechanical stress does not reduce the range of maximum permissible loads established by changing the thermal stress parameters.

Numerical Investigation on the Effect of Fuel-Rich Degree in the RBCC Engine under the Ejector Mode

The ejector mode of the Rocket-Based Combined-Cycle (RBCC) engine is characterized by high fuel consumption. This study is aimed at investigating the influence of the rocket fuel-rich degree on the RBCC engine’s performance under the ejector mode combined with simultaneous mixing and combustion (SMC). Numerical simulations were conducted for various rocket mixing ratios (Φ=1.6~3.2) under subsonic (Maf=0.9) and supersonic (Maf=1.8) flight conditions. It was observed that a high fuel-rich degree in the rocket plume negatively impacts the eject performance under all conditions. However, it improves the overall performance (Isp) at high flight Mach numbers (Maf). For supersonic conditions, increasing the fuel-rich degree promotes greater fuel participation in combustion, thereby enhancing RBCC engine performance. Nevertheless, the subsonic-supersonic mixing layer exhibits low evolution, resulting in a decrease in reaction efficiency from 29.2% to 12.0% as the Φ decreases from 3.2 to 1.6. Consequently, there is an inefficient utilization of fuel. To optimize RBCC engine performance, the rocket fuel-rich degree can be appropriately increased. However, this increase should be limited to prevent fuel wastage arising from low reaction efficiency. Under subsonic conditions (Maf=0.9), the low kinetic energy of captured air leads to the occurrence of “negative thrust surface” and “wall impact” phenomena, which hinder the efficient and stable operation of the RBCC engine. Consequently, adjusting the fuel-rich degree alone cannot promote specific impulse (Isp), and a low fuel-rich degree is considered an ideal strategy when combined with adjustable nozzle technology.

Comparative research and experimental verification of <?A3B2 pi6?>adjustable nozzle technology for free jet

Comparative research and experimental verification of <?A3B2 pi6?>adjustable nozzle technology for free jet

Performance analysis of a novel small-scale radial turbine with adjustable nozzle for ocean thermal energy conversion

Ocean thermal energy is acknowledged as one of the most promising ocean renewable energy sources in low latitude sea areas. In the ocean thermal energy conversion system, the turbine plays a significant role, and it is responsible for converting the working medium enthalpy into the shaft output power. The present study is focused on the performance analysis of a novel radial inflow turbine with an adjustable nozzle in the OTEC system in order to adapt to the changing operating conditions of the turbine, which vary with the change in seawater temperature. At the design point, the predicted overall isentropic efficiency is 86.5%, and the shaft output power is 15.3 kW, slightly higher than the expected 15 kW. Furthermore, a parametric study is performed, respectively, for the nozzle vane stagger angle and the nozzle-impeller radial clearance to explore the favorable geometric parameters for different conditions. The turbine’s overall efficiency increases slightly with deceasing nozzle-impeller radial clearance, and the variation of the nozzle vane stagger angle is much more influential on the turbine shaft power and overall efficiency. The optimum stagger angle point moves from 32° to 36° gradually with the increase in nozzle-impeller clearance. Finally, the feasibility of an adjustable nozzle for the turbine under off-design conditions was verified by combining the radial clearance and nozzle stagger angle.

Measurement of surface tension with free-falling oscillating molten metal droplets: a numerical and experimental investigation

AbstractRayleigh’s equation has been widely used to determine surface tension from oscillating droplets. In this study, the use of a drop-on-demand droplet generator is proposed to create free-falling, oscillating, molten metal droplets for this purpose. To examine the applicability of the droplet generator, extensive numerical simulations in three and two-dimensions were performed. The effect of gravity, initial velocity and initial deformation on the frequency and pattern of the droplet oscillation was investigated. The use of this generator enables the creation of thousands of droplets in the course of a single experiment and the droplets have a much shorter exposure time to possible unwanted contaminations, due to a rapid measurement principle. Furthermore, the adjustable nozzle size of the generator provides flexibility in terms of droplet size, which affects the range of validity of Rayleigh’s method. To validate the method, the surface tension of molten copper in an argon atmosphere was determined over a temperature range of 1400–1620 K. The determined linear relation is expressed as σ [mN m−1] = (1307 ± 98) − (0.22 ± 0.015) (T−1356) (T in K).

NUMERICAL SIMULATION OF A GEAR

To navigate safely, the ship must be manoeuvrable and have good stability. The steering of the ship depends on a number of factors such as: the means of steering used, the geometric shapes of the hull (stern area), the ratios between the main dimensions (LCWL/B and B/T), the number, position and direction of rotation of the engine. and the hydro-meteorological conditions in which they sail (water, air, wind, waves). Every ship, with the exception of barges, must have a robust and safe steering system to ensure manoeuvrability and sea stability. These installations can be: rudder with hydrodynamic profile, installation with adjustable nozzles and other installations approved by the Classification Societies. In this particular study an analysis on a gear pump fitted in the azimuth system of a chemical tanker is being made, using a CFD technology. The main aim is to study the efficiency of this pump by comparing the CFD analysis results with the results in real operational condition. Main parameters focused on are outlet flow, suction column, power and pump efficiency. There are several differences registered in the case of suction column and power, but they are not that high, while parameters outlet flow and pump efficiency are almost identical.

The Results of Calculations of the Axial Turbine Stage with Different Meridional Outlines of Its Adjustable Nozzle Vane

Turbomachines with adjustable (rotary) nozzle vanes (ANV) find increasingly broader use in various technical fields owing to their featuring lower loss of efficiency in comparison with other flow rate changing methods. Improvement of their efficiency is becoming more important while fulfilling the manufacturability and reliability requirements. Three options for shaping the meridional outlines of the adjustable nozzle vane (ANV) and the blades themselves, which are rather complex items for manufacture, are studied by calculation: option 1 – with conventional cylindrical meridional surfaces and blades cut at the ends with spherical surfaces, which ensure an acceptable (around 0.3 mm) minimum tip clearance above the leading and trailing edges only at the smallest of the possible blade angles, and in the root section – only at the maximum blade angle (of the required range); option 2 – with spherical outlines and blades cut along a sphere equidistant to the outline spheres (with a clearance of around 0.3 mm); option 3 – with flat meridional outlines in the form of a polyhedral prism and blades with flat ends equidistant to the prism faces (with a clearance of around 0.3 mm); The results of calculations carried out in the ANSYS CFX software package are described and analyzed, which have shown a slight advantage in efficiency ηri (by around 2%) for options 2 and 3. For these options, the decrease in efficiency with an increase in the flowrate above its design value is less noticeable than for option 1, and with flowrates lower than the design one, the values of efficiency ηri are the same for all options.

Fabrication of Battery-Operated Roof Paint Sprayer with Automatic Charging Off System

The study was conducted at Barangay San Juan, Aborlan, Palawan, and was evaluated from April to December 2021. Fabrication of the device was based on the needs of roof painters to lessen their exposure to sunlight during roof painting. The roof paint sprayer was divided into three major parts. First, the container served as overall part with hand carry at the top, which weighs 6 kilograms when empty but approximately 11 kilograms when full. Second, the direct current motor is rated 60 W, 12 V nominal, maximum flow of 5 liters per minute, and a maximum pressure of 116 psi. The base of the motor was fitted at the bottom while the hole of the first container is connected to the inflow of the motor, and a hose with an adjustable nozzle is connected to the outflow. Third, the power source consisted of a connector cord, female socket, 12V transformer, circuit board, green LED, 12Vdc battery, battery indicator, and switch. The performance evaluation of the device revealed during testing showed that at the start the roof paint sprayer works smoothly and sprayed almost 1/3 area of the target area (10×3 meters) for almost 2 minutes but suddenly as it sprayed, the dc motor starts difficult to run until it stopped. The major benefit of the device, if studied further, will spray faster on roofs and smooth output.

Структура и свойства паяных соединений высоколегированных никелевых сплавов, полученных с помощью дугового нагрева в вакууме

Repair of blades made of the cast high-temperature nickel alloys with the volume content of γ’-phase of 50...65% and more by fusion and built-up welding practically leads to no results. Only introduction of special methods in certain cases provides restoration of a section satisfying the blade operation conditions. Therefore, the leading foreign and domestic enterprises mainly use high-temperature soldering in vacuum with general heating to repair blades of the nozzle unit, flaps of the adjustable nozzle and other parts of the gas turbine hot pass. It becomes possible to increase performance of the permanent joints (especially the small ones) by high-temperature soldering with the lowest acceptable thermal effect on the base metal through local heating in vacuum by the arc discharge with the hollow cathode. Arc soldering in vacuum with supply of the powder composite solders to the greatest extent combines advantages of built-up welding and high-temperature soldering with the general heating. Results of metallographic studies and mechanical tests of the solder joints obtained by arc soldering in vacuum with powder composite solders on samples with imitation of the surface defects showed higher performance compared to that for joints created by high-temperature soldering in vacuum with general heating.

Features of Gas Flow in the Axial Stage of a Turbine with an Adjustable Nozzle Vane Assembly

The method of changing the gas flow rate through the turbine by adjusting (turning) the nozzle vanes has been known as the most economical one for more than 50 years. It is most widely used in transport gas turbines and internal combustion engine pressurization units. Recently, many articles have appeared in the technical literature on the advisability of using adjustable nozzle vane assemblies (ANVA) in advanced aircraft engines, power generating units, and in turbo-expander units of natural gas preparation and low-temperature separation systems. In all cases of using ANVAs, their developers are attracted by the possibility of economical and reliable provision of variable operating modes of installations. The article shows by calculation that a decrease in the stage efficiency due to the presence of end gaps in the ANVA, related to the flow-over the nozzle vane ends on the profile pressure side to the suction side and subsequent interaction with the main flow through the interblade channel, can be so significant, especially with low-height vanes, that it can lead to vanishing the advantages of this flowrate changing method. Design measures for tightening the gaps in the form of peripheral and root cylindrical bosses at the profile ends, which eliminate overflows in the vane end major part and partially screening the gap are proposed and studied. A favorable effect of the proposed measures on the losses in the ANVA and in the turbine stage has been confirmed.

Intelligent production optimization method for a low pressure and low productivity shale gas well

Shale gas wells frequently suffer from liquid loading and insufficient formation pressure in the late stage of production. To address this issue, an intelligent production optimization method for low pressure and low productivity shale gas well is proposed. Based on the artificial intelligence algorithms, this method realizes automatic production and monitoring of gas well. The method can forecast the production performance of a single well by using the long short-term memory neural network and then guide gas well production accordingly, to fulfill liquid loading warning and automatic intermittent production. Combined with adjustable nozzle, the method can keep production and pressure of gas wells stable automatically, extend normal production time of shale gas wells, enhance automatic level of well sites, and reach the goal of refined production management by making production regime for each well. Field tests show that wells with production regime optimized by this method increased 15% in estimated ultimate reserve (EUR). Compared with the development mode of drainage after depletion recovery, this method is more economical and can increase and stabilize production effectively, so it has a bright application prospect.

Mathematical modeling of spatial gas flow in nozzles of nontrivial geometry

Numerical modeling of the spatial gas flow in an adjustable nozzle with an asymmetric critical section caused by the overlap of a part of the flow area by a gas flow regulator has been carried out. The mathematical model is based on three-dimensional models of gas dynamics, the method of large particles is used for calculation. When describing the unsteady flow of an inviscid gas, the system of Euler equations is used, written for a computational rectangular plane, taking into account the function of nozzle geometry. The results of calculations of flow parameters along a nozzle path with a uniform outlet section and with an obliquely cut outlet nozzle are presented. Calculations were carried out for completely open critical sections and for half overlapped. For oblique cut nozzles, the overlap of the critical section from the side of the short part and from the side of the long part of the oblique nozzle is considered.

Экспериментальные исследования силовой турбины с регулируемым сопловым аппаратом

The article discusses the results of experimental research of the impact of the law of profiling along the stage height on the characteristics of a turbine with an adjustable nozzle guide vanes. The results of the design study have been confirmed, taking into account meridional streamline bending. It is shown that in the stage profiled according to the law of constancy of the product of the radius of the flow path and the tangent of the blade angle the degree of reactivity in the root sections of the blades increases provided that the degree of reactivity at the middle diameter is the same as in a turbine with a constant blade angle, which leads to an increase in the turbine efficiency in modes with a reduced angle of arrangement of blades of the adjustable nozzle guide vanes and the degree of pressure reduction.

Сравнительный анализ судовых дизелей по предельному повышению экономичности при непосредственном управлении расходом воздуха

The paper presents a comparative analysis of the operational parameters and parameters of marine diesel engines obtained as a result of computational and theoretical studies with direct control of air flow using an adjustable turbocharger nozzle to ensure the maximum allowable efficiency of diesel engines. The objects under study are: two-stroke marine diesel engine, operating on the screw characteristics; marine four-stroke diesel working on the screw characteristics; marine four-stroke diesel working on the load characteristics. As a result of the rotation of the blades of the adjustable nozzle in the direction of reducing the angle of their installation the diesel engine efficiency increases. However, the maximum pressure of the cycle also increases, the pressure drop decreases during purging the cylinders, the effective angle of gas exit from the turbine nozzle decreases, and the compressor's surge stability margin changes. There has been studied the design potential of diesel engines for the maximum increase in their efficiency, which made it possible to accept the stable operation of the compressor in all the studied modes. In the course of the research, boundary values were found for the maximum pressure of the diesel cycle, the pressure drop for purging the cylinders and the effective angle of flow exit from the nozzle apparatus, beyond which the specified parameters did not go beyond all the studied modes of operation of diesels. Taking into account the limitations of the greatest potential for improving efficiency in the equity modes of loads has a four-stroke diesel engine, operating on the screw characteristics, the smallest capacity is the same petrol, but working on the load characteristics.

Effect of pre-swirl nozzle closure modes on unsteady flow and heat transfer characteristics in a pre-swirl system of aero-engine

The pre-swirl system is of great importance for temperature drop and cooling air supply. This study aims to investigate the influencing mechanism of heat transfer, nonuniform thermodynamic characteristics, and cooling air supply sensitivity in a pre-swirl system by the application of the flow control method of the pre-swirl nozzle. A novel test rig was proposed to actively control the supplied cooling air mass flow rate by three adjustable pre-swirl nozzles. Then, the transient problem of the pre-swirl system was numerically conducted by comparison with 60°, 120°, and 180° rotating disk cavity cases, which were verified with the experiment results. Results show that the partial nozzle closure will aggravate the fluctuation of air supply mass flow rate and temperature. When three parts of nozzles are closed evenly at 120° in the circumferential direction, the maximum value of the nonuniformity coefficient of air supply mass flow rate changes to 3.1% and that of temperature changes to 0.25%. When six parts of nozzles are closed evenly at 60° in the circumferential direction, the maximum nonuniformity coefficient of air supply mass flow rate changes to 1.4% and that of temperature changes to 0.20%. However, different partial nozzle closure modes have little effect on the average air supply parameters. Closing 14.3% of the nozzle area will reduce the air supply mass flow rate by 9.9% and the average air supply temperature by about 1 K.

A Specifically Designed Injector for Controlled Lube Oil Addition in View of Investigation of Pre-Ignition Phenomena in Dual–Fuel/Gas Engines

Internal combustion engines will continue to play a role during a transitional phase, especially in heavy-duty or marine applications. In this context, lean-burn gas/dual-fuel combustion is an attractive concept to reduce CO2, combined with considerably lower particulate and NOX pollution, and with efficiencies comparable to diesel combustion. However, ignition processes still pose considerable challenges, with pre-ignition in particular being a major issue. The underlying mechanisms are probably based on self-ignition of lube oil in hot zones. In order to investigate fundamentals of such phenomena in optically accessible test rigs, a novel injector was specifically developed to induce pre-ignitions artificially. The so-called “PieZo-Droplet-Injector” (PZDI) enables dosing of minor amounts of lubricating oil or even the injection of single droplets with diameters in the range of 100–200 µm. The working principle relies on a needle actuated with a piezo stack, which pushes a certain amount of lube oil in a bore so that (even single) droplets can be ejected through an adjustable nozzle. To confirm the PZDI functionality and to investigate droplet characteristics based on adjustable operating parameters, tests were performed under ambient conditions as well as in a constant volume combustion chamber under reasonable pressure and temperature conditions. Overall, the PZDI showed an excellent behavior in terms of capabilities to inject small amounts or even single droplets of lube oil. At last, this specially developed injector allows selective lube oil addition in an optically accessible engine test facility for upcoming examination of pre-ignition phenomena under real operating conditions.

Dynamic simulation method of adjustable nozzle considering clearance fit

Aiming at the motion stagnation and local damage failure of a 2D needled Cf/SiC adjustable nozzle during operation, the motion performance of the nozzle and the contact stress at the key parts were studied. A dynamic simulation method of the nozzle with adjustable nozzle considering clearance fit was established, and the throat contraction process was analyzed by a simulation example. Firstly, the critical analysis positions of the nozzle were determined by trial calculation, and the model was simplified and the mesh was optimized. Then, the simulation was carried out under the boundary conditions involving multiple fields. The motion characteristics of the nozzle throat during the throat contraction process were analyzed due to the velocity results, and the stress state and failure state at the key position of the nozzle during the impact process were finally determined.

Ice shell construction in Hokkaido of Japan during 1980–2012

This paper summarizes research and development of an ice shell construction carried out in inland Hokkaido of Japan from 1980 to 2012.The ice shell is made of thin-walled curved ice plate and constructed according to the following method. (1) Building up a three-dimensional formwork by inflating a two-dimensional membrane bag covered with ropes anchored to the snow-ice foundation ring. (2) Covering the formwork with a thin saturated snow layer of less than 1 cm thickness by blowing milled snow with a rotary snow blower and spraying water with an adjustable nozzle, and letting it freeze naturally at temperatures below −10°C. (3) Repeating (2) until shell thickness reaches to the design thickness, then removing the bag and ropes for reuse. A number of ice shells were constructed as temporary winter structures while improving the construction technique through the repeated construction experiences. Based on the field experiments of 10–30 m ice domes (“ Xm ice dome” means the ice dome constructed by using Xm diameter of circular membrane bag in the formwork before inflation) which measured the deflection and temperature under long term period after the completion and further observed the behavior of the collapse, it was recognized that understanding the creep behavior is extremely important for evaluating the structural safety of the ice shell.

Jet electrochemical machining simulation of intersecting line removals with adjustable nozzle diameter by a finite area element grid

Jet electrochemical machining (Jet-ECM) is a machining process which makes flexible surface structuring of metallic materials with nearly no tool wear possible. Through a nozzle cathode with an inner diameter of e.g. 100 µm a continuous electrolyte jet is applied to the workpiece surface. When an external voltage is applied, an electric charge is transported between the nozzle cathode and the anodically polarized workpiece, which causes a material removal on the workpiece based on anodic metal dissolution. By moving the nozzle cathode in x and y directions, material is removed along the contour movement of the nozzle. In the previous studies multiphysical models based on the Finite-Element-Method (FEM) or Finite-Volume-Method (FVM) were presented to simulate this removal processes. It can be derived, that the simulation of the resulting material removal for intersecting line removals is resource intensive and complex in commercially available software. Furthermore, a simulation of intersecting line removals with adjustable nozzle diameters with FVM or FEM is challenging. As a new approach a model based on a finite area element grid was built up in Python. The model applies square sections to represent resulting depth profiles of a machined workpiece. The paper explains the physical design of the model for a simulation of intersecting line removals with adjustable nozzle diameter. Such removals are shown by the help of transient calculations. The resulting depth profiles for different nozzle adjustments are discussed.

Variable-geometry nozzle for surface quality enhancement in 3D concrete printing

The 3D Concrete Printing technology (3DCP) has developed fast in the past few years. Compared to conventional construction method, the 3DCP technology offers an advantage in speed and cost. However, the surface of a structure from 3DCP technology requires post-finishing processes as the direct outcome suffers from low quality surface finish problem, such as jagged surface and staircase effect. This study aims to improve the surface finish quality in 3DCP using a developed novel variable-geometry nozzle that can directly control the extrudate geometry during the printing process at every layer. The nozzle assembly features an adjustable nozzle outlet geometry that can be controlled along the process. The mechanism requires a slicing algorithm to determine the extrudate geometry at every layer based on the designated printed structure. The corresponding algorithm was also developed and will be presented in this paper. Subsequently, the functionality of the proposed method was validated with a case study of manufacturing a structure with curved outer-surface geometry (an arch).