bluuebunny/crossref_metadata_2025 huggingface dataset:
Coordinate structure of feature geometrical location specifications
Authors: Glukhov V I , Varepo L G , Shalay V V , Simonenko K V , Belyaev P S
Published: May 2021

The paper proposes a systemic transition from the location and orientation of tolerance product features to linear and angular coordinates in the coordinate system of the product electronic model. The coordinate system is formed by designing datums set with a total informativeness content of six constrains on the object degrees of freedom, three of them being linear and three of them being angular constrains. The main design datums determine the object position in the product and form a generalized coordinate system. Auxiliary design datums determine the position of the attached object on the considered object and form an auxiliary coordinate system. Each element of the product has a certain informativeness content to limit the degrees of freedom, both linear and angular. When forming a Cartesian coordinate system, the datum element transfers piece or all of its informativeness content to it. As a result, the coordinate planes acquire different informativeness of three, two and one, and the coordinate axes acquire that of four, two and zero. The coordinate axes and planes informativeness content determines the number of linear and angular coordinates that can be set relative to them. Similarly, the feature datums informativeness means the number of linear and angular coordinates that must be specified in the coordinate system for its single-task location and orientation. The transition to a coordinate system for standardizing location and orientation deviations demonstrates compliance with a systematic approach that improves the quality of products in terms of the geometric specifications accuracy.
Account the resistances under the action of the suction
Authors: Kudryavtsev S A , Gersenshteyn I S , Sultanova Y M , Lee M
Published: May 2021

In this paper we’ll show the interrelation between pressure suction and suction object. Suction force and air flow rate are determined as a function of the air pressure supplied to the suction. Here (unlike the earlier works) airflow losses are taken into account. In casethe gaps between the suction surfaces are either too small or too large, suction force is replaced by repulsion. The math expressions that describe the interrelation between air flow rate and suction force will help us to choose optimal suction parameters.
Test planning and evaluation of maintainability indices of engineering products
Authors: Kukhtik M P , Makarov A M , Barabanov V G , Stegachjov E V
Published: May 2021

One of the most important issues of maintainability of engineering products is an experimental evaluation of quantitative maintainability indices. It is necessary to plan maintenance and repair tests of products to obtain estimates. The analytical dependencies to determine amount of check and determinative tests and value of specified maintenance time for the cases of normal and exponential distribution laws of maintainability indices have been derived in the article. The numerical examples of calculation of amount of tests and evaluation of maintainability indices of engineering products have been represented.
Assessment of printing cylinder deformation effect on nature of load distribution
Authors: Serkova L B , Varepo L G , Kolozova O A , Belyaev P S , Bezzateeva E G
Published: May 2021

Various loads have a significant effect on the operation of different equipment components. Modern national and international studies show high efficiency of applying finite element methods to research into the loading nature of various parts and systems as a whole. Unevenly distributed loads can reduce the performance of the equipment, as well as lead to the failure of components. This paper examines the effect of the position of the substrate gripper system on the deformations in the printing cylinder. The findings prove that the misalignment of the shaft and gripper bridge placement doubles the resulting deformations.
Research of the electrical complex of a conveyor with two wire drums
Authors: Domanov V I , Domanov A V , Meshchaninov I A
Published: May 2021

The electrical equipment and control system of the conveyor conveyor electric drive are considered. The functional and structural diagrams were drawn up. The analysis of the operation of one-and two-drum electric drives is carried out. Structural diagrams of the mechanical part of the conveyor were obtained. A mathematical description was compiled and modeling of the investigated electric drive was carried out. The structure and model of the elastic link are compiled taking into account the friction forces. The use of a smoothing filter in the speed reference circuit makes it possible to eliminate fluctuations in the system from the reference signal. A mathematical model of the electrical complex has been compiled and its modeling has been carried out. The results obtained confirm the effectiveness of the application of the corrective coupling based on the elastic moment signal.
Equationally extreme trees
Authors: Rybalov A N , Shevlyakov A N
Published: May 2021

We study extreme semilattices whose Hasse diagrams are trees, and prove that the linearly ordered tree of order n has the minimal average number of solutions of 1-variable equations.
Detection of network attacks by deep learning method
Authors: Tatarnikova T , Bogdanov P , Kraeva E , Stepanov S , Sidorenko A
Published: May 2021

In this paper, we discuss the possibility of using a neural network approach in solving the problem of detecting network attacks. The neural network is designed to solve the problem of classifying the transmitted traffic into not containing an attack and containing an attack. The difficulties of using a neural network in this problem are discussed. Difficulties are associated with the choice of significant information features for the formation of the date set and having as many training examples as possible for each type of attack. Solutions for the selection of significant information features are proposed. It consists in ranking the features in order of importance. A method and rules for ranking features are proposed. In the future, it is proposed to use only important features to train the neural network. The problem of uneven number of training examples for each type of attack is considered. It is proposed to preserve significant examples represented by small sample sizes by assigning weights to them. Experiments show the effectiveness of the proposals discussed in the paper.
A Cascadic Multigrid Algorithm on the Shishkin Mesh for a Singularly Perturbed Elliptic Problem
Authors: Tikhovskaya S V
Published: May 2021

A two-dimensional linear elliptic problem with parabolic and regular boundary layers is considered in the unit square. It is solved by using an upwind difference scheme on the Shishkin mesh which converges uniformly with respect to a small perturbation parameter. The scheme is resolved based on an iterative method. It is known that the application of multigrid methods leads to essential reduction of arithmetical operations amount. Earlier we investigated the cascadic two-grid method with the application of Richardson extrapolation to increase accuracy of the difference scheme uniformly with respect to a perturbation parameter for a linear elliptic equation with parabolic and regular boundary layers and the cascadic multigrid method with the application of Richardson extrapolation for a linear elliptic equation with regular boundary layers. In this paper a cascadic multigrid algorithm of the same structure is studied. We also used an interpolation formula uniform with respect to a perturbation parameter and an extrapolation of initial guess using numerical solutions on two coarse meshes to reduce the arithmetical operations amount. The application of the Richardson extrapolation method based on numerical solutions on the last three meshes leads to increase accuracy of the difference scheme by two orders uniformly with respect to a perturbation parameter. We compare the proposed cascadic multigrid method with a multigrid method with V-cycle with a special restriction operator. The results of some numerical experiments are discussed.
Research minimax and minisum Weber problems on a plane with forbidden zones
Authors: Zabudsky G G , Veremchuk N S
Published: May 2021

Weber problem is a well–known location problem of connected facilities. Two optimality criteria are considered. The first criterion is minimization of the total cost of connections among facilities. The second criterion is minimization of the maximum connection between facilities. This article deals with Weber problems on a plane with rectangular forbidden zones. Location inside in the forbidden zones is not allowed. The sides of forbidden zones are parallel to the coordinate axes. To measure distances rectangular metric is used. An overview of studies for these problems is provided. Some properties of the problems are described. For example, the possibilities of reduction of admissible areas in the search for an optimal solution are presented. Variants of different bounds of the objective functions are provided. Models of integer linear programming with Boolean variables are given. Computational experiments with using the branch and bound algorithms, the constructed models and IBM ILOG CPLEX package were carried out. Usage of the properties of reductions of admissible areas is promising both in solving of the problems by combinatorial methods and using the integer optimization apparatus.
Computer geometric modeling of quasi-rotation surfaces
Authors: Beglov I A
Published: May 2021

The paper presents an analytic description of quasi-rotation correspondence. The formulas for calculation of values characterizing geometric objects are provided on the basis of constructive description of the quasi-rotation correspondence. The values characterizing circles generated through quasi-rotation of the initial point are calculated. A system of parametric equations describing a generic quasi-rotation surface is provided. Every type of curvilinear second-degree axis – circular, elliptic, parabolic, and hyperbolic – is considered. An algorithm for surface modeling through computer algebra systems has been developed on the basis of the analytic description and tested by means of Maple software. The algorithm allows one to acquire plots of separate sheets of the surface as well as all four sheets simultaneously. The capability to acquire 3D models of quasi-rotation surfaces given the desired shape and mutual location of the axis and the generatrix is demonstrated. The developed algorithm is applicable to any flat generating curve belonging to the axis plane and defined by a single-parameter system of equations. The resultant 3D model polygon count is user-defined and only limited by computer’s processing capability assuring high surface quality. The images of several four-sheet quasi-rotation surfaces are provided. The developed algorithm allows one to design surfaces of pre-defined properties.
Critical point analysis of an irregular surface model
Authors: Kuchkarova D F , Achilova D A
Published: May 2021

The article discusses approaches to modeling a surface by its discrete values. Possible passage positions are shown when modeling the surface according to the amount of information. Existing classification schemes for models according to the structure of input data are considered. The difference in the concepts of mathematical modeling in a narrow and broad sense is shown. The concept of an irregular critical point of a surface is considered, which is associated with the concept of the rank of a map. there are two types of metric points metrizing a given space. The definition of the curvature of the vertex and the degree of curvature is given. Types of points on the surface are defined. a method is proposed for determining irregular (critical) points of a surface by differentiating a matrix of initial data. Here the second partial and mixed derivatives are calculated. Possible cases of analysis of each vertex of the surface are considered. For each vertex, its degree of curvature and the type of vertex are determined. The original matrix with the source data is converted to a new matrix, where the elements show the type of vertex for each point. The task of identifying the desired model is reduced to constructing it in each cell.
Investigation of the electro-technical complex with alternative energy sources
Authors: Belyaev P V , Podberezkin D A , Golovsky A P
Published: May 2021

The article considers hybrid electric power complexes. The prospects of their development are shown. The expediency of using alternative energy sources for sustainable electricity and heat supply to consumers is proven. A mathematical model of an autonomous electrical complex with a fuel cell and a photovoltaic station as power supply sources is presented. The necessity of taking into account mutual influence of individual subsystems of the electrical complex, as well as their influence on the complex as a whole is reasoned.
The algorithm for selecting the optimal voltage class of the gas field power supply system, taking into account the entire life cycle
Authors: Bogachkov I M , Khamitov R N
Published: May 2021

The paper proposes an algorithm for choosing the optimal voltage class of a power supply distribution grid of gas well clusters, in which there is a multiple electrical load increase during field’s life cycle. Building a mathematical model with considering factors allows to design both a trunk line and a single radial grid and evaluate the magnitude and direction of the influence of individual factors, i.e. to conduct a quantitative analysis of the gas field power supply diagram. An extreme experiment is used to construct mathematical models. The optimization parameter is accepted as economic-the minimum of discounted costs. The paper presents six response functions-regression equations. The distribution grids of a number of operating gas fields in Western Siberia have been investigated taking into account the entire life cycle of the field at “PRON” computer program. The proposed algorithm can be used in the design of the power supply system for new gas fields, which allows to select the optimal voltage class for the power supply system of gas clusters, considering the entire life of the gas field, taking into account the minimum discounted costs. It can improve the efficiency of decisions, reduce funds and design time.
Experimental study of the boiling process in a fire-tube boiler with different heat transfer fluids
Authors: Slobodina E N , Mikhailov A G
Published: May 2021

Currently various boiler modifications differing in the types of heat transfer fluid used andin the heat exchange conditions in the boiler working area are presented on the market. To improve the boiler efficiency, it is necessary to take into account the peculiarities of the heat exchange process during convection or boiling depending on the properties and type of the heat transfer fluid used.
Experimental investigation of the effect of laser radiation on evaporation of a liquid
Authors: Trushlyakov V I , Novikov A , Panichkin A , Lesnyak I , Averchenko A , Sevoyan V
Published: May 2021

To study the process of model liquid (ML) evaporation under laser irradiation, two experimental samples (ES) in the form of ML reservoirs have been developed: an experimental reservoir with transparent walls, ES1, and an experimental reservoir of metal ES2, as a prototype of a future porous structure.

The processes of ML evaporation under constant and discrete laser radiation (LR) of different power were studied.

The program and methodology of experiments were developed and preliminary results of ML evaporation processes were obtained, including: current mass and temperature for ES1, ES2. The advantage of the discrete mode of exposure LR over constant mode of LR is shown. In the discrete mode of LR at a distance of 10 mm between the focus of LR and the surface of ES2 at a power of LR of 60 W evaporated ML by 4% more than at constant LR, and at a power of LR of 90 W evaporated ML by 22% more than at constant LR.
Effect of heat treatment temperature on the properties of silicon dioxide films derived from film-forming solutions
Authors: Kozlov A G
Published: May 2021

The effect of the heat treatment temperature on the physical properties of sol-gel silicon dioxide films derived from film-forming solutions is investigated experimentally. The dependencies of the thickness of the films, their refractive index, electrical strength, resistivity, etching rate, and the level of internal mechanical stresses on the treatment temperatures in the range from 700 to 1150 °C are obtained. It was found that the dependencies of the electrical strength, the etching rate, and the level of internal mechanical stresses have the sections with the different characters. The transition region between these sections corresponds to the heat treatment temperature equal to 900-950 °C.
Investigation of hydrogen permeability through nickel membrane by mass spectrometry method
Authors: Strunin V I , Khudaibergenov Zh G
Published: May 2021

Dynamics of hydrogen permeability through nickel membrane is studied; diffusion coefficient and time of hydrogen penetration through membrane are calculated. As a result of the work, it was revealed that hydrogen diffusion through the nickel membrane occurs, and it has a saturation character one day after the application of the solution. The obtained results make it possible to evaluate the process of flooding of quartz resonators of thermostats (QRT) housings in a chemically aggressive environment and in conditions of high humidity.
Experimental studies of a valveless non spool-type pneumatic percussion mechanism of a hammer
Authors: Gruzin A V , Abramenkov D E , Gruzin A V
Published: May 2021

Performing different kinds of activities, both in mining companies and in construction of industrial, housing and civil facilities requires specialized equipment provided with attached active operating elements, for example, pneumatic hammers. The analysis and selection of a schematic diagram of a pneumatic percussion mechanism are performed using known elements-features and structural additional expanding elements-features. This allowed a development of a new design of a valveless non spool-type pneumatic percussion mechanism of a hammer, for which analytical studies of its operating modes using a mathematical model were conducted. Experimental studies were carried out with an experimental sample of a pneumatic percussion mechanism to specify the reliability of parameters for the proposed mathematical model.
Comparison of modeling the natural frequencies and vibration modes of a sound isolation panel fragment with full-scale tests
Authors: Romanenko E A , Russkikh G S , Sokolovskiy Z N
Published: May 2021

The article discusses the results of modeling natural frequencies and modes of vibration, performed in the Ansys Workbench software package in comparison with a full-scale experiment. The aim of the study is to verify the model built in Ansys Workbench. The results allow us to make a conclusion about the adequacy of the model and the possibility of its application for solving the problem of determining the natural frequencies and vibration modes.
Elastic wave propagation in a cylinder with external active friction
Authors: Sultanov K S , Khusanov B E , Rikhsieva B B
Published: May 2021

Wave propagation in an elastic cylindrical body interacting with an external moving absolutely non-deformable medium (a cage) under a shock load on the front end is considered. The friction force arising on the contact surface directly depends on the parameters of the propagating waves and, due to the external medium motion,-it is active. The stated one-dimensional problem is solved analytically by the method of characteristics. Exact solutions are obtained for the stress wave propagation in a cylinder. An increase in the wave parameters with time and distance was determined; the influence of the parameters of external load and the physical and mechanical characteristics of the cylinder on the parameters of the increase in propagating waves were determined. The place and time of equalization of the velocities of the cylinder particles and the external medium motion, and the stress state of the cylinder particles, were discussed.
Experimental study on the complete stress-strain curve of gangue aggregate concrete
Authors: Bai Guoliang , Su Yuxiang , Liu Hanqing
Published: May 2021

In order to study the complete stress-strain curve of Chinese YuShenFu district’s gangue concrete. This experiment contains seven groups of gangue concrete which are all made by different water cement ratio and different gangue replacement rate, altogether 15 standard prismatic specimens. After the axial compression of concrete’s specimens, stress-strain curves of gangue concrete were obtained. In order to study the complete stress-strain curve of gangue concrete. In this paper, 15 coal gangue prism samples (150mm×150mm×300mm) were prepared for axial compression test. The main parameters are water-cement ratio and replacement rate of gangue aggregate. The result shows that there are four stages including the whole process of gangue concrete under uniaxial compression, but the descent stage exists the phenomenon of sudden break-down. Based on the data, the gangue concrete complete stress-strain curves’ constitutive equation is fitted. The parameter of ascending section fits favorably and the parameter of descending section is dispersed.
Influence of Thermal Alternation on the Interface between Insulation Layer and Bonding Mortar
Authors: Zhu Shaofeng , Wang Yaqun , Wang Yuxi , Su Fukang
Published: May 2021

The safety of the external thermal insulation system has been widely concerned by people. In this paper, strain gauges and temperature sensor are preset at the interface of bonding layer/insulation layer, bonding layer/mortar layer. The interface stress variation rules of graphite polystyrene board, polystyrene board and homogeneous board were studied under 30 times of thermal alternating environment and the test results were analyzed in combination with physical properties of the materials. The results show that the strain at the interface of the samples composed of three kinds of thermal insulation materials increases with the increase of the number of thermal alternating cycles. The total interfacial strain of the sample composed of homogeneous board is the largest, and that of graphite polystyrene board is the smallest.
Mechanical properties of a new string capsule drainage anchor and its supporting effect in deep foundation pit
Authors: Yuan Fanglong , Yang Zhijun , Chen Yuntao
Published: May 2021

With the increase of the scale and depth of urban underground space construction in coastal soft soil area, the traditional anchoring technology has been difficult to meet the requirements of deep foundation pit excavation and support. This paper puts forward a new type of string capsule drainage anchor supporting structure, introduces its structure composition, analyzes its working mechanism and mechanical characteristics, the calculation formula of ultimate bearing capacity of small cylindrical shear failure between anchor and surrounding soil is given, finally, the supporting effect of the new structure in deep foundation pit engineering is simulated and analyzed by finite element software. It is concluded that the stress of the new type of anchor can be divided into three stages: static earth pressure, plastic zone development and plastic zone breaks through; the new anchor can quickly dissipate the pore water pressure in the surrounding soil, which is more conducive to the stability of foundation pit; the axial force distribution presents a “sawtooth” shape, and the axial force increases sharply in the expanding section; the supporting effect of the new anchor is more obvious than that of the traditional anchor, which can more effectively inhibit the horizontal displacement of the slope.
Parametric analysis of the influence coefficient of round-end concrete-filled steel tubular members
Authors: Wang Erlei , Xie Jianxiong
Published: May 2021

The long-term load has great influence on the internal force distribution, deformation, bearing capacity and other mechanical properties of round-end concrete-filled steel tubular member. Parameter analysis is carried out on the influence coefficient kcr of the round-end concrete-filled steel tubular members under the influence of long-term effects. The parameter analysis results show slenderness ratio, concrete strength, steel content and load eccentricity have great impact on the influence coefficient kcr.
Mechanical performance analysis of U-shaped steel-concrete composite deep coupling beam
Authors: Zhiren Yuan , Jiayue Ding , wang Ren , Jianhong Fan , Junfei Niu
Published: May 2021

In this paper, semi-span simply supported beam is used to simulate the mechanical behavior and failure mode of U-steel reinforced concrete composite-deep coupling beam, and three U-steel reinforced concrete composite beams, with same height-span ratio of 1/3, were tested under one-point vertical concentrated loading in mid-span. Theresults show that the mid-span yield height exceeds 60% of U-steel-concrete composite beams flange, and that the three of U-steel-concrete composite beam specimens aredamaged, there is a critical oblique crack in the inner concrete of the beam that is roughly parallel to the line between the bearing center and the loading point. It is concluded that the failure mode of this type of U-shaped steel-concrete beam begins with yieldat mid-span bottom and flanges of U-shaped steel, and ends with concrete shear failure.
Effect of Resonant Environment on Discrete Frequency Noise Generation from a Two-Dimensional Airfoil
Authors: Yamada K. , Furukawa M. , Sakurada S. , Mizokami T. , Aso S. , Sakoda K. , Fukui T.
Published: May 2021

It is known that discrete frequency noise with specific peak frequency, which is often called tonal noise, is generated from an airfoil in the flow conditions within certain Reynolds number range. In this study, the tone noise generated from the NACA0012 airfoil inclined at a small angle to the stream is investigated. The test has been conducted in two different configurations to clarify the effect of resonant environment on the noise generation: one is a duct configuration in which wall was installed at both sides across the airfoil, and the other is a wall-free configuration without any wall around the airfoil. The numerical simulation with lattice Boltzmann method (LBM) also has been conducted to investigate detailed generation mechanism of the tone noise. The experimental results show that the tone noise is generated with several peak frequencies in the wall-free configuration, while it has a single peak for the duct configuration. The simulation results are compared with the experiments at two configurations in terms of sound pressure spectrum, and the pressure fluctuation leading to the tone noise and the corresponding unsteady flow phenomenon are discussed to clarify the noise generation mechanism. A feedback loop is formed between the vortex shedding from separated blade surface boundary layer and the resulting aerodynamic sound at the trailing edge, which results in the tone noise.
Effect of Leading Edge Profile on Cavitation Performance of Mixed Flow Impeller
Authors: Sano Takeshi , Iino Masamichi , Maeda Satoshi
Published: May 2021

Cavitation inception on a pump impeller blade is affected by the blade profile around the leading edge. Even if the difference of the blade profile is limited around the local leading edge area, such as, different elliptical ratios of the leading edge, pressure limitation of cavitation inception differs drastically. This leads to the difference of cavitation erosion speed, and it is important to understand the mechanism and quantitative effect of leading edge shape on cavitation inception, to avoid troubles related to cavitation erosion. In this study, CFD and experimental investigation were carried out to clarify the effect of leading edge shape on cavitation inception. The tested pump was a mixed flow pump, which is widely used as a circulating water pump for power plants. Various leading edge shape were calculated and tested with keeping the blade camber line. Only elliptical ratio of the leading edge on the suction side was changed. As for CFD, isolated impeller, single phase analysis was carried out for 90, 100 and 110% design flow rates, blade surface area on which pressure is less than the vapour pressure was evaluated for each cases. In the experiment, 5 bladed mixed flow pump model was used, and the cavitation length was measured. Both experimental and calculated results were compared and considered. As a result, it was clarified that the optimized value of elliptical ratio is around 2 to 6, which changes depending on the flow rate. Additionally, when the elliptical ratio is 4, was almost half of the one with elliptical ratio 1. Cavity length and cavitation intensity has positive correlation, and estimated erosion speed when the elliptical ratio is4 is almost an eighth of baseline.
The effect of unsteady vortex behavior on noise characteristics in a centrifugal compressor
Authors: Tajima Kenta , Miida Hiroshi , Fujisawa Nobumichi , Ohta Yutaka
Published: May 2021

The effect of diffuser width on the noise level of a centrifugal compressor equipped with vaneless diffusers was investigated through experiments and numerical techniques. In this regard, two diffusers with different widths were installed in the compressor. In case the wider diffuser was used, there was the bandwidth (800 to 900 Hz) noise and pressure fluctuation which was closed to 1/2BPF (700 Hz). This fluctuation occurred because the leakage vortices were of two different frequencies. Type 1 vortices are the ones that were discharged from the main blade and covered Passage 1. Type 2 vortices had the same length as Type 1, but they were discharged from the splitter blade. Type 3 vortices covered both Passages 1 and 2; these were discharged from the main blade. Type 3 vortices were generated predominantly at 270°, and their frequency was approximately 700 Hz at 1/2 BPF frequency. The former two types of vortices occurred occasionally, and their frequency was approximately 1400 Hz. Type 3 vortices grew with the wider diffuser because of the higher pressure-recovery, which caused the serous loading to the impeller blades. The broadband noise fluctuation occurred by the coexistence of the two frequency vortices.
Turbopump Design: Comparison of Numerical Simulations to an Already Validated Reduced-Order Model
Authors: Apollonio A , Anderlini A , Valentini D , Pace G , Pasini A , Salvetti M V , D’Agostino L
Published: May 2021

The article expands on the ongoing assessment of the reduced order model proposed by some of the authors for the geometric definition and noncavitating performance evaluation in the preliminary design and parametric optimization of mixed-flow centrifugal turbopumps. Some of the dynamically most significant predictions of the model are compared with the experimentally validated URANS (Unsteady Reynolds-Averaged Navier-Stokes) simulations of the non-cavitating flow through a typical six-bladed unshrouded mixed-flow turbopump for liquid propellant rocket engines operating at both design and off-design flow conditions and different values of the impeller clearance. The observed discrepancies can be explained in terms of the simplifying assumptions introduced for the development of the model and their relative magnitude (< ±10%) does not adversely interfere with the accurate prediction of the turbopump performance over a wide range of operating conditions above and below design flow rate. Together with earlier experimental validations, the results dramatically confirm the capability of the proposed model to generate useful engineering solutions of the turbopump preliminary design problem at a negligible fraction of the computational cost required by 3D numerical simulations.
Coupled Mode Flutter of a Linear Compressor Cascade in Subsonic and Transonic Flow Conditions
Authors: Schuff Matthias , Chenaux Virginie Anne
Published: May 2021

Flutter onset in turbomachinery is typically investigated numerically via decoupled methods due to a high mass ratio of structure to air. The unsteady aerodynamic response of a forced motion vibration is evaluated for a positive or negative work entry. The forced motion simulations assume vacuum mode shape vibrations at certain amplitudes without modal coupling due to aerodynamic forces. This approach, also known as the energy method, is valid for a high blade mass ratio and small logarithmic decrement values. An aeroelastic study of a multi-passage linear compressor cascade was performed. In fluid-structure-coupled time-marching CFD, generic heave and pitch degrees of freedom are allowed to vibrate freely in reaction to any aerodynamic forces. For one subsonic and one transonic flow condition predicted to be stable by the classical energy method approach, aerodynamically coupled-mode flutter is observed. It is shown that variations in the starting conditions, i.e. the initial vibration and inter-blade phase angle of the system, can have a strong influence on the number of CFD iterations required until amplitudes grow. However, if coupled-mode flutter is present in the system, it will ultimately set in at a distinct inter-blade phase angle.
Mitigation Method for Pressure Fluctuations Induced by Acoustic Resonance
Authors: Tsutaya K , Liu Z , Kubo M , Miyagawa K
Published: May 2021

Multi-stage pumps used for boiler water supply of thermal power plants have large capacity and pressure. Fluctuations may cause vibration and noise in pumps, piping systems, and surrounding structures. Lots of studies have been conducted on the pressure fluctuation phenomenon of turbopump piping systems. Some of the factors are the rotor-stator interaction, a resonance between the fluid in the pipe and, excitation source and resonance between structure and pump operation. Besides, studies on mitigation method for pressure fluctuations have been conducted. Inserting orifice to add damping, adjusting the length of pipe to change resonance frequency and, installing resonator to mitigate a specific frequency. However, these studies have not quantified the solution to the pressure fluctuations, so further research is needed to elucidate the causes and establish countermeasures quantitatively. In this study, pressure fluctuations due to acoustic resonance are generated by using a speaker. An orifice, a bent tube, and a branch pipe are installed at the node and antinode of the secondary pressure standing wave in the pipe, and the effects on the standing wave are observed. Moreover, the mitigation method for the pressure standing wave is established by performing a sweep test. Numerical analysis is conducted by AMESim to validate the results of experiment. It is clarified that by inserting the orifice at the appropriate position of a standing wave, pressure fluctuations are mitigated. In the case of branch pipe, pressure fluctuations are effectively mitigated by inserting it having appropriate pipe length and boundary condition.
Control of jet structure utilizing the change in the outlet velocity distribution with time
Authors: Ichihara C , Yamaguchi D , Kobayashi R , Nishibe K , Yokota K , Sato K
Published: May 2021

Flow control using jets is widely implemented. In particular, the clarification of jet technology is indispensable in the control of the blade stall control of blades and for thermal management, such as refrigeration and air conditioning. As part of the fundamental research into the topics mentioned above, various studies of the flow characteristics of steady jets have long been conducted, and the structure of the jets investigated. However, studies on flow control by synthetic jets that essentially exhibit an unsteady flow have begun only recently. Synthetic jets have a flow wherein the jet structure forms downstream of the slot, although the net flow rate is zero, because of repeated ejection and suction. Attempts have been made to control of the jet’s direction of travel by adjusting only the jet’s frequency without any geometric changes. However, many aspects of the effect of oscillation characteristics on the jet’s structure are still unclear. Moreover, since the flow rate is low, it is not suitable for large-scale fluid control, such as that required for high-power fluid machinery. In this study, excited jets are proposed, wherein the velocity distribution change with time at the slot exit and the time-averaged flow rate are considered. An attempt was made to control the jet structure by means of the oscillation characteristics. The influences of the frequency and the phase of the slot outlet velocity distribution on the maximum jet velocity and the jet width were investigated by numerical calculations and experiments. Our research led us to conclude that the staggered vortex street is generated when the phase of the slot exit velocity distribution is π. Further, we concluded that the jet structure could be controlled by the frequency under a certain specific set of conditions.
Design Optimization of High Specific Speed Prototype Francis Turbine by Design of Experiments
Authors: Lee Nak-Joong , Hwang Young-Cheol , Inagaki Morihito , Miyagawa Kazuyoshi
Published: May 2021

In general, Francis turbines are known to last for 40 to 50 years of use. However, exchanging an old turbine for a new is expensive because of modernization costs. Therefore, many modernization projects will take place through new runner changes. The Francis turbine in this paper has a high specific speed of about 330m-kW and a runner diameter of about 4.3m. The new runner can be expected to have a more stable flow and improved performance by flow analysis. In this paper, the performance analysis of the runner was performed using the CFD by Design Of Experiments (DOE). The sensitivity of variables was examined using L18 method. Numerical analysis was performed via BladeGen, Turbogrid, ICEM CFD, and CFX, which are commercial CFD codes. The design goal is to enable not only the best efficiency point but also a more stable operation than before even at partial load conditions. Find out how to find the shape of a runner blade by searching for design points that maximize annual power generation according to newly selected operating conditions.
Heat generation of ball bearing for rocket-engine turbopump in low-temperature gas hydrogen
Authors: Kakudo Hiromitsu , Yokoyama Takashi , Takada Satoshi
Published: May 2021

Cryogenic fluid such as liquid hydrogen, liquid oxygen, and liquid methane is used for rocket propellant because of their performance. Cryogenic fluid turbopump equipped in rocket-engine is started to rotate after precooling bearings is completed. The ball bearing used for the turbopump have worse lubricating performance because the lubricant is not liquid material such as oil which coagulate at cryogenic temperature but solid material. Polytetrafluoroethylene (PTFE) is used for the lubricant in Japanese rocket engines [1]. One of the glass transition temperature of PTFE is around 100 K, and it is considered that the strength of PTFE become weak discontinuously above 100 K and poor lubrication problem would occur in bearings. Ball bearings for turbopump which need to perform high stiffness at high rotation speed don’t meet the performance suddenly when they have any slight damages. Therefore, bearings should be precooled before the engine start so that poor lubrication problems would not occur. However, there is little knowledge of the ball bearing performance in the environment of gas coolant. If ball bearings for turbopumps have good performance in the environment, turbopump can be started to rotate under the insufficient precool environment. It contributes reduction of time and propellant for the precool, and improvement of rocket performance and diversification of space transportation mission are expected. In this study, bearing rotational tests in gas coolant are conducted in the several conditions of the rotational speed and the thrust load in order to clarify the bearing performance for rocket engines in gas coolant.
High-performance ocean energy harvesting turbine design – A strategy of compound leaning
Authors: Ranjith B. , Madhan Kumar P. , Takao Manabu , Samad Abdus
Published: May 2021

Blade leaning works well for steam, hydro and gas turbines, where the flow is unidirectional. In contrary, the turbine used in an oscillating water column wave energy device has a unique design which can work only in bidirectional flow and gives a unidirectional torque. In this article, a compound leaning concept is explored through numerical modelling. An impulse turbine with 0.3m diameter and two rows of guide vanes mirroring each other was considered as a case study. Reynolds-averaged Navier-Stokes equation with k-ε turbulence closure model was solved in ANSYS-CFX code. The present numerical result matches well with the existing experimental results. The modified rotor blade gave 8.8% higher efficiency as it reduced the intensity of trailing edge vortex shedding and the downstream recirculation region.
Experimental determination of turbocharger heat flows for validation of a power separation approach
Authors: Brodbeck Philipp
Published: May 2021

This work presents a new method to measure the heat flow from a turbocharger to the ambient air. The experimental setup, performed on a hot gas test bench, includes an insulated box with two openings, encapsulating the turbocharger. These openings enable a controlled air flow through the box, which is measured at the inlet duct of the box. With temperature measurements at the inlet and outlet of the box, the quantitative heat flow can be calculated. With this information, an approach to estimate those heat flows from standard turbocharger test bench measurements can be validated and refined. The performed measurements at different turbine inlet temperatures and turbine mass flows show a good conformity with expected heat flows. Due to convective and radiative effects, the heat flows increase with both turbine mass flow and turbine inlet temperature. However, the setup with the insulated box has an effect on the overall thermal conditions, since the convection around the turbocharger decreases if the specimen is not as exposed as in common test bench setups.
The Characteristics of Rotordynamic Forces generated by Mechanical Seals
Authors: Inoue H , Yabui S , Inoue T
Published: May 2021

Evaluating rotordynamic reaction force caused by whirl excitation is very effective technique in order to investigate the dynamic properties of the mechanical seal. Especially, it is easy to understand the stability of the rotating component by investigating rotordynamic tangential force. In this paper, the stability of the mechanical seal was discussed by measuring the rotordynamic tangential force depending on the whirl frequency. Judging from the result, the mechanical seal used for this study has stable performance that the tangential force always acts against whirling direction at 1,000 rpm of rotational speed and up to 30 Hz of whirl frequency. Furthermore, whirl frequency ratio and effective damping were calculated using cross-coupled stiffness and direct damping which were obtained by solving quaternary linear equations after whirl excitation test. Whirl frequency ratio was always bellow 1.0, and effective damping was also always positive at all frequencies. Those results indicate that the mechanical seal definitely generate the force to stabilize this whirl vibration.
Effects of Misalignment of Turbine Wheel Hub with Housing
Authors: Wang Yu , Chen Hua , Ma Chao , Sun Jinhui
Published: May 2021

Alignment of a turbocharger turbine rotor hub with its housing can affect aerodynamic performance of the turbine, and studies may have been done in industry to quantify this effect. However, there is no related publication in open literature and so the effect and the underline mechanism remain trade secrets. A numerical investigation into the effect and the mechanism was carried by current authors using two turbine wheels with identical flow passage but different backdisc configurations: one with a full backdisc and the other a deeply scalloped backdisc. For each configuration, five alignments of the wheel hub with housing were studied, these include a full alignment of the rotor hub and the housing and four misalignments of the two turbine components. Effects of the alignment and turbine operating condition on aerodynamic performance of the turbines were studied. The flow field of the turbines was interrogated, and the underline mechanism that produced the performance changes was investigated. The study yields some interesting results: For the full backdisc configuration, the exposure of the backdisc and the wheel recess from housing both decrease turbine efficiency. It has been found that the exposure of the backdisc in the housing outflow creates a stagnation point at the tip of the backdisc, generating some loss. The stagnation then forces the incoming flow to move away from the hub and toward the shroud side of the wheel, producing further losses within the wheel passage. The high pressure at the tip of the backdisc also reduces the flow entering the backdisc cavity between the wheel and heat shield, thus decreases the loss in the cavity. However, this loss is relatively small compared with the loss in the main flow passage. It has also found that the misalignment has greater negative effects on aerodynamic performance of the turbine with deeply scalloped backdisc, and a stronger leakage flow from the backdisc cavity into rotor passage occurs due to the opening in the backdisc by the scalloping. Turbine operating condition has an effect too: lower U/C condition shows higher impacts of misalignment than higher U/C condition. These results are reported and analysed.
Investigation of wind properties at MUTSU Bay and TSUGARU Strait JAPAN
Authors: Honda A , Sasanuma N
Published: May 2021

Present investigation was conducted to confirm the wind properties at Mutsu Bay and Tsugaru Strait by measurement. The wind distribution along the pathway of ferry ship was investigated. Wind speed and wind direction were measured on one of the four ships operated between Aomori Harbour and Hakodate Harbour during 2018. This paper describes the wind properties measured by ferry anemometer.