bluuebunny/crossref_metadata_2025 huggingface dataset:
Indication of relative motion intensity of aerodynamic object and meters with different physical nature
Authors: Danilov S N , Moskvitin S P , Panasyuk Yu N , Pudovkin A P , Shatovkin R R , Varepo L G , Nagornova I V
Published: May 2021

The need to track the motion trajectory, of a plane for example, the parameters of a power plant, etc., requires creating meters that operate under conditions of unpredictable changes in coordinates and their derivatives. This task is done by synthesizing tracking meters, which, depending on the situation, can change both the parameters and, possibly, the structure. This is implemented by meters, which can use different combinations of state models. In accordance with the chosen method, an algorithm for indicating the intensity of relative motion-aerodynamic object – measuring system- is obtained. The intensity is indicated by the acceleration magnitude of the aerodynamic object approach to the meter, calculated on the basis of information from meters of various physical nature.
Control systems design: the method of the generalized criterion composition for multi-criteria optimization
Authors: Denisova L A , Meshcheryakov V A , Denisov O V
Published: May 2021

The article deals with optimization issues in design of an automatic control system (ACS). The method of multicriteria optimization is presented, which combines simulation of ACS and optimization procedure based on a genetic algorithm and implemented by the MATLAB / Global Optimization Toolbox. The method of the generalized criterion composition based on the initial particular criteria is also proposed. The use of this generalized criterion makes it possible to reduce the complexity of determining the optimal parameters of the ACS and allows to take into account the constraints when searching for the optimal solution.
Development of a microprocessor system for monitoring the accelerations of moving elements of technological machines
Authors: Yu Orlova E , Yu Shmelev F , Sh Gertsenshteyn I , Trapeznikova O V , Panin Yu N , Lee Minhee
Published: May 2021

During the operation of machines and aggregates, processes, that are difficult to describe in theoretical ways, occur. When studying the mechanism in detail, it is still better to resort to experimental measurements in order to gain a greater understanding of the transients that occur during its operation, movement, and shut down. Such detailed data can be used to improve the properties of the mechanism, the principles of its design, as well as to reduce its dimensions and energy consumption. An acceleration sensor was developed, which will allow to investigate the causes of problems with mechanism precision, occurrence of noise, as well as identify a poor assembly and adjust machine mechanisms.
Determination of the parameters of adjusting the gear broaching machine, according to the measurements of the spur bevel gears
Authors: Safarov D T , Kondrashov A G , Kozin K I
Published: May 2021

The process of adjusting a gear broaching machine is considered, according to the angle of the cone of the depressions and the symmetry of the side profiles of the gear wheel. Standard adjustment methods do not allow measuring the values of the taper angle of the valleys and deviations from the symmetry of the profiles. The article proposes a method for finding the main setting parameters of gear broaching machine, according to the measurement data of spur bevel gears. The measurement method is implemented in the form of a measuring system, including a special control device equipped with inductive probes, and algorithms for processing their readings. The use of the measuring system makes it possible to increase the accuracy of setting up the gear traction machine and to improve the quality of manufacturing of spur bevel gears.
Modeling measurement situation in intelligent information and measurement system to determine thermo-physical properties of materials
Authors: Selivanova Z M , Skomorokhov K V , Belyaev M P , Varepo L G , Nagornova I V
Published: May 2021

Definition of thermo-physical properties in different thermal conductivity ranges of solid materials causes the need to consider numerous affecting factors, to create an information environment and model the measurement situation in the operation of intelligent information and measurement system. The purpose of the study is to reduce the measurement error of thermo-physical properties in materials. This problem is relevant and important in the process of controlling the reference parameters of products at the manufacturers. A theoretical framework for modeling the measurement situation is developed. This includes a conceptual model for the formation of the measurement situation, and a model of the research object domain. A mathematical model of the measurement situation and the methodology of its development is created. The problem of selecting the type of measurement situation in the range of investigated materials in terms of thermal conductivity is solved. The risk calculation algorithm of forming a measurement situation in an intelligent information and measurement system for determining the thermo-physical properties of materials is developed.
The formation of the target function in the design of a small spacecraft for technological purposes
Authors: Taneeva A S
Published: May 2021

The paper deals with the issues of forming and minimizing the target function in the process of creating a small spacecraft for technological purposes. The main difference between such a spacecraft is the need to meet specific requirements for micro-accelerations. These requirements provide favorable conditions for the implementation of gravity-sensitive processes on board a small spacecraft. The constructed objective function allowed us to determine the design appearance of a small spacecraft for technological purposes. The results of the work can be used in the design of small spacecraft.
Diagnostics of rolling bearings using artificial neural networks
Authors: Vinokur A I , Kulikov G B , Suslov M V , Petrov V P , Bykov A l V , Litunov S N , Bezzateeva E G
Published: May 2021

The vibration of bearings No. 60,206 with radial clearance of 0…0.45 mm is investigated. Analysis of the frequency response (FR) of vibration acceleration reveals information frequencies of 6 Hz, 15 Hz, 26 Hz, and 46 Hz, which coincide with the calculated values. The dependence of the vibration acceleration amplitude on the radial clearance for the specified frequencies is determined. The possibility of rolling bearing wear estimation by vibroacoustic diagnostic methods using artificial neural networks is proved. Diagnostic accuracy with the 4:4-3:1 MI network ranges from 75.6% for a radial clearance of 0.15 mm to 100% for a clearance of 0 mm.
Evaluation of computational efficiency by the method of parallelization in a multi-core CPU’s in a large data array
Authors: Alisherov F A , Iskandarov S Q , Khamraeva S I , Nurmetova B B
Published: May 2021

Nowadays, with the rapid growth of data, there is a growing demand for large-scale data processing. This data processing, led to the development of computers. These include the development of computer processors, cores. This article explores the effectiveness of Microsoft framework-based parallel extension for multi-core processors for fast Fourier Transform (FFT) in fast multi-faceted computing paradigms. We have a very large number of threads as a multi-thread paradigm, and the cost of switching between threads is minimal. The global nature of computational and transactional equilibrium and built-in communication models in the parallel FFT algorithm makes it an ideal candidate for multidimensional platforms.
Embed digital watermarks in executable program memory
Authors: Belim S V , Munko S N , Belim S Yu
Published: May 2021

The article proposes a method for embedding digital watermarks into executable program code. A digital watermark is generated in the process RAM. Existing information structures, such as dynamic arrays and objects, are used to accommodate parts of the embedded message. The message embedding program modifies the size of the data structures. The digital watermark is placed in additional memory locations. Two approaches to the placement of digital watermarks are proposed. Arrays are ordered in lexicographic order. Parts of the embedded message are placed in arrays. There are no array names in the executable code. nformation for stegonographic analysis is not available. Arrays for embedding can also be selected in any order. Portions of the digital watermark are written to a dynamic unidirectional list. The unidirectional list is embedded in arrays. Embedding into objects of the same class is carried out using similar methods.
On direct product of algebraic sets over groups II
Authors: Shevlyakov A N
Published: May 2021

We consider systems of group equations of the structure S = S1(X) US2 (Y), where the set of variables X, Y are disjoint. Suppose we know the radicals of the systems Si. However we prove that the radical of the whole system Rad(S) may contain equations which are not derived from equations from Rad(Si).
Method for splitting the feasible region to increase the variability of continuous optimization test problems
Authors: Matrenin P V , Kiryanova N G
Published: May 2021

The solution of optimization problems is essential for the design and control of technical systems. The optimization problem arising in practice has a high dimension, nonlinear criteria, and constraints. There are a lot of continuous optimization tasks for testing and research of optimization algorithms performance. These tasks have a convex range of acceptable values limited to a specified range for each parameter. The problem of generating test multidimensional continuous optimization tasks with nonlinear constraints and splitting the feasible region is considered. A method was proposed for splitting the feasible region by separate domains using the multidimensional grid of forbidden solutions. As a result, the problem acquires properties closer to optimizing technical systems with complex constraints. The method allows creating an unlimited number of test optimization problems, which can be used to research and develop optimization algorithms. The method is simple to implement, and the impact on the computational complexity of tasks is insignificant. Research has been carried out on four widely used continuous single-objective optimization test functions, with the Genetic algorithm and the Particle Swarm Optimization algorithm. It is shown that the proposed method has an influence on the process of solving multidimensional continuous optimization problems by population algorithms and on the dependence of the accuracy of the algorithm on its heuristic coefficients.
Algorithm for determining the conductive low-frequency electromagnetic interference in electrical networks
Authors: Rudi D Y , Gorelov S V , Khatsevskiy K V
Published: May 2021

The electric power systems (EES) of various industrial enterprises for a number of reasons are characterized by low quality of electric energy, in particular, the presence of higher harmonics in the networks, as a result of which conductive low-frequency electromagnetic interference (EMF) occurs. This leads to the problem of the quality of electric energy in the EPS, which negatively affects the electrical equipment. The problem is vast and the question of solving various problems, one of which is the determination of conductive low-frequency electromagnetic fields by the coefficient of the nth harmonic component of the voltage, is not solved. Development of an algorithm for determining the conductive low-frequency EMF by the coefficient of the nth harmonic component of the voltage. This algorithm allows scientifically sound assessment of the electromagnetic environment in electrical networks. Creating a sequence of decisions to determine the quality criterion for the functioning of electric power systems by the coefficient of the nth harmonic component of the voltage. Based on the theory of probability and mathematical statistics, an algorithm has been developed for determining the conductive low-frequency electromagnetic field by the coefficient of the nth harmonic component of the voltage. The developed algorithm is based on the requirements of the international state standard GOST 32144-2013. Using this algorithm, a computer program has been developed that allows the automated calculation of the parameters of the electromagnetic environment (distribution parameters, the probability of their occurrence). Moreover, it makes an automated calculation of such distribution parameters of the values of the coefficient of the nth harmonic component of the voltage as the mean value and standard deviation. Also, the program performs an automated calculation of the probability of the coefficients of the nth harmonic component of the voltage exceeding the normalized values and the probability of the appearance of the conductive low-frequency EMF by the coefficient of the nth harmonic component of the voltage during the calculation period. In turn, it is also able to visualize the data arrays that were obtained in the course of various experimental studies using an oscillogram and a histogram.
Effect of asphalt concrete strength properties on energy intensity of milling
Authors: Furmanov D V , Lysakov N E , Shamahov L M
Published: May 2021

Asphalt removal is a complex, energy-intensive technological operation. The paper is devoted to the research of power and energy properties of cutting by the cutting elements of road milling machines. We have analyzed works devoted to the development of different road-building materials; based on the analysis, we deem it possible for the correlation to exist between the strength properties of asphalt concrete and the cutting resistance forces produced by the working units of road milling machines. The most suitable strength property is the contact strength of asphalt concrete determined by the static penetration method. The paper describes the methodology of experimental research in this area and presents the results of experimental studies. We prove a direct correlation between the tangential component of the cutting resistance force and limit contact stresses for three types of asphalt concrete. This makes it possible to quickly and reasonably determine the cutting resistance forces when milling asphalt concrete of different grades at different temperatures without having to conduct complex, expensive research. The established relationship between the asphalt concrete contact strength property and the tangential component of the cutting resistance force suggests that the asphalt concrete strength properties previously determined by temperature, composition, and structure can be replaced by one, namely, its contact strength. This can replace the huge list of existing materials with a single parameter — contact destruction strength.
Effect of the acrylonitrile content in nitrile-butadiene rubber on the relative residual deformation of vulcanizate
Authors: Ilyicheva T M , Eremin E N
Published: May 2021

The paper presents the results of a study of rubbers based on butadiene-nitrile rubbers (NBR) grades BNKS-40 and BNKS-18. The influence of the content of acrylonitrile (NAC) on the rheological and physico-mechanical properties of vulcanizates has been evaluated. It is shown that the content of NAC in the NBR composition significantly affects the relative residual compression deformation of the vulcanizate both under normal conditions and at elevated temperatures. The dependencies revealed in the work make it possible to make the correct choice of the rubber grade in the development of rubber resistant to compression deformation.
Study of magnetically active elastomers resonance and damping properties
Authors: Minaev A Ja , Korovkin Ju V , Stepanov G V , Valiev H H
Published: May 2021

The dynamic properties of magnetically active elastomers based on silicone polymer matrix with various ferromagnetic fillers under the external magnetic fields influence using a vibration-testing complex have been studied. The amplitude-frequency characteristics and the investigated composites resonance frequencies changes under such influences are established. Calculated dependences for determination tested samples damping properties are given. Analysis of the obtained data revealed a damping coefficients decrease in the investigated materials with an magnetic forces increase acting on the investigated magnetoactive elastomers.
Features of laser shock processing application to titanium alloys with shape memory
Authors: Sakhvadze G Zh , Splavskiy I S
Published: May 2021

The paper presents the features of applying the methods of dimension analysis and finite element simulation in relation to the processes occurring during laser shock processing (LSP) of titanium alloys with the shape memory effect (SME). It is found out that the main dimensionless parameters that control the depth of the plastic zone that occurs during LSP are the dimensionless duration of the laser pulse and the peak pressure in the shock wave. A comparative assessment is made between the simulated dependence of the dimensionless depth of the plastic zone on the dimensionless peak pressure in the shock wave and the corresponding experimental studies from the existing publications.
Computer simulation of substrate effect on 2D ferromagnetic film state
Authors: Belim S V , Tikhomirov I V
Published: May 2021

In the article computer simulation of ground state for two-dimensional film on the substrate is performed. The influence of the substrate is modeled using a periodic potential. The potential contains a parameter defining the width of the maxima and minima. The film has a simple square crystal lattice. The substrate potential structure models a square lattice. We consider the case of different film coating ratio ratios. The lattice and substrate periods are also different. If the coating coefficient is different from one, mechanical stresses are present in the film. The case with one fixed edge for the film and periodic boundary conditions was investigated. The film atoms do not form a square lattice in this case. The displacements of atoms are periodic. The period depends on the coating factor. A superlattice is present in such film.
Influence of thickness nonuniformity of piezoelectric zinc oxide layer on parameters of microelectronic BAW solidly mounted resonator
Authors: Torgash T N , Kozlov A G
Published: May 2021

The paper presents the experimental results of a study of the influence of the thickness nonuniformity of a piezoelectric zinc oxide films on electrical equivalent parameters of microelectronic BAW resonators: the static and dynamic capacitances, dynamic inductance, and dynamic resistance. These parameters were determined using the experimental frequency dependences of resonator impedance and the Butterworth-van Dyke model. The resonators under investigation had an operating frequency of 2.8…3.0 GHz; the frequency spread about 500 MHz. The quality factor of the resonators was 250…350 and the relative width of the resonant bandwidth of the resonators were equal to 0.2…0.4%.
Geometrically nonlinear calculation of thin shells taking into account shear deformations when using the form of interpolation of the sought quantities
Authors: Klochkov Yu V , Ishchanov T R , Andreev A S , Klochkov Yu M
Published: May 2021

Annotation. A finite element model for the analysis of geometrically nonlinear deformation of a thin-walled shell-type structure based on the principles of the Timoshenko type shear theory is proposed. As the basis of this model, we consider a fragment of the surface of the object under study in the form of a curved quadrilateral with nodes that coincide with its vertices. The desired unknowns at the nodes of the curved quadrilateral were the increments of the components of the displacement vector and the partial derivatives of these increments with respect to the natural coordinates of the surface of the shell object under study, as well as the increments of the components of the vector of the angles of rotation of the normal. To obtain interpolation expressions for the desired values, we implemented a fundamentally different vector form of the interpolation procedure from the standard one. The principal distinguishing feature of the above-mentioned form of interpolation is the compilation of interpolation dependencies not for each desired variable parameter as an isolated scalar value, but for the increment of the displacement vector and the increment of the vector of the angles of rotation of the normal, which act as interpolation objects. As a result, in a curved coordinate system, original interpolation dependencies were obtained for the increments of the components of the displacement vectors and the angles of rotation of the normal at an arbitrary point of the quadrilateral, which are functions of the nodal values of all the increments of the components of the above-mentioned vectors, and not just the increments of the components of one particular direction.
The effect of heat transfer on the stress-strain material state considering the final rate of heat spread
Authors: Proskuriakov N E , Lopa I V , Zverev I V
Published: May 2021

Calculation results of different wave tasks are analyzed. It is shown that deformation heating of material is intensive near the boundary surface and quickly decreases during insignificant removal from it. The conclusion is drawn that for obtaining exact solutions of wave tasks in nonisothermal statement it is necessary to consider redistribution of temperature in materials because of the heat transfer and its influence on the intense deformed condition of materials of different designs. Calculation results are given. The sensitivity of the decision to change of specific heat capacity and the thermal diffusivity entering wave equation of heat conductivity is noted.
Investigation of the modes of motion of a hydraulic drive with axial-piston hydraulic motors at low speeds
Authors: Syrkin V V , Galuza Y F , Abramova I A , Treyer V A
Published: May 2021

Technological machines for various purposes, in which hydraulic actuators are widely used, are constantly being improved in terms of power, speed and accuracy of the specified parameters. It requires making certain changes in the design of these actuators that allow them to withstand the operating modes of technological machines within the specified limits. The article considers the results of the study of the operation modes of a nonlinear hydraulic actuator with axial-piston hydraulic motors under the conditions of parametric excitation of self-oscillations due to the nonlinear nature of the friction moment in the front distributor of the hydraulic motor. The authors propose mathematical models of the modes of operation of this hydraulic drive at low speeds. They present a linearized mathematical model and the results of the study of this hydraulic drive in the form of amplitude-frequency characteristics obtained using the harmonic linearization of the dynamic equations. The results of the study allow us to estimate the parametric oscillations of the hydraulic actuator and to evaluate the minimum value of the constant component of the speed corresponding to the beginning of periodic intermittent motions, which leads to a decrease in the accuracy of performing technological movements of the actuators of technological machines.
Effect of Emulsion Powder Content in VAE Emulsion on Tensile Properties of Joint Filler
Authors: Huang Zhe , Xu Jinyu , Xia Wei , Ren Weibo , Wang Zhihang
Published: May 2021

The traditional joint filler used in our country is easy to be damaged by the environment. At present, polymer composite is used to form a new type of polymer joint filler (NPJF) to improve the properties of joint filler. In this paper, by comparing and testing the various indexes of the joint filler under tensile load under the condition of 5 kinds of latex powder content, the performance of the joint filler after molding was studied. The results show that the tensile strength and tensile modulus of the joint filler increase with the increase of latex powder content, the elongation at break and peak strain decrease first and then increase. The influence of the amount of latex powder on the tensile properties of the joint filler mainly lies in the improvement of the aggregate ash ratio, the formation of the film structure and the change of the overall microstructure.
Research on Urban Architecture Landscape Design Based on Virtual Reality Technology
Authors: Wang Meizhen
Published: May 2021

With the continuous escalation of architectural design requirements, the continuous complexity of architectural models, and the integration of computer technology, virtual reality technology in architectural design has also emerged. The application of virtual reality technology in architectural design deepens the communication between professional architects and non-professionals, makes the architectural effect more intuitive, and effectively solves the communication barriers between architects and non-professionals. This article discusses the basic theory of virtual reality technology, and studies how to apply virtual reality technology in the landscape design of modern cities. On the premise of analyzing traditional landscape design methods, analyze the disadvantages of traditional landscape design methods; by studying the advantages of virtual reality technology, we choose to construct some scenes of urban architectural landscape design for virtual reality models. The article combines virtual reality technology with architectural design to effectively solve some of the shortcomings of traditional urban landscape design.
A data-driven method to minimize sensor use for dynamic shading control
Authors: Zhu Jiaqi
Published: May 2021

Dynamic facade systems are a promising strategy to balance the benefits and drawbacks of daylight penetration through the window in a built environment. A well-operated shading system should allow for sufficient daylight access while preventing glare in response to changing weather conditions. The dynamic shading system can also help with making use of daylight to reduce the lighting energy use when integrated with electric lighting control. This paper presented a data-driven approach to control the automated shading system. The control method allows the system to be responsive to outdoor weather conditions. With data from offline daylight simulation using typical meteorological year weather, three machine learning classification algorithms were applied to train predictive models for online shading control. The proposed method was validated using a climate-based simulation. It was found that all models had a satisfying prediction performance, with an accuracy of 0.85 to 0.92. The shading control could maintain the work plane illuminance for 97% to 99% of the time during the year. It was also associated with a potential of reducing electric lighting energy use by 40% to 43% compared to that of on/off lighting control.
Study on the mechanical property of low magnesia ore high strength concrete-filled steel tubular columns
Authors: Gao Huaguo , Zhang Lingxin , Xu Shilin , Wang Qingli , Wen Shuqing , Wang Yinbiao
Published: May 2021

The high strength low magnesia ore concrete-filled steel tubular (CFST) column under eccentric loading was studied in this paper. The experiment of seven groups of different eccentricity ratio was conducted, and the details of experiment and test methods were introduced. The experimental ultimate load of each test was compared with design loads from several domestic specifications, and the bearing capacity of specimen with different confinement index was simulated. The results of load-vertical deflection curves show that when the eccentricity is the same and the capacity is 12% higher than that of steel tube high-strength concrete eccentrically compressed short columns, the distribution of longitudinal strain along the section height of steel tube in the two types of short columns basically conforms to the assumption of flat section. According to the results of the research, it was suggested to adopt confinement index of 1.1-1.4 in the practical project with the same to the common high strengthen concrete, and the layout of small eccentric load should be used in the structural design so as to better utilize the mechanical properties of the materials.
Research on the design of the integrated wall panel of the prefabricated building in substations
Authors: Li Teng , Guo Jia , Hu Shiyao , Chai Linjie , Jing Zhipeng , Cheng Rong , Wang Zhongliang
Published: May 2021

In order to meet the needs of the modular construction and prefabricated construction of the State Grid Corporation of China, higher performance requirements are put forward for the wall panels of the building. Integrated wall panels have the advantages of high integration, high assembly, short construction period and good construction quality, which can effectively reduce on-site wet work and have significant economic and social benefits. This article combines the actual engineering and existing construction technology to explore the technical application of the integrated wall panel design for assembly buildings in substations, which provides a reference for the future development of assembly buildings.
Research of electric field strength on surface of conductor and its splitting type used in extra high voltage substation
Authors: Shiling Zhang
Published: May 2021

Extra high voltage substation is an important part of the whole project locates in high altitude area, so corona audible noise exists around the operation equipment, mainly concentrated in the bundle conductor in the power station. This research on the split form and surface electric field intensity distribution of bundle conductor has a certain degree of theoretical and practical engineering application value. In this paper, an analysis of the classic formula illuminates the conductor split form, conductor diameter, bundle spacing and other factors how to affect the largest surface electric field intensity of the conductor. On this basis, we take a typical extra high voltage substation conductor as the research object. The three-dimensional model of the actual power station has been established with application of finite element simulation method in accordance with actual structure, and a preliminary calculation of surface electric field intensity also been obtained. According to the results, we analyze the reasons cause the serious corona. Then we design three-split conductor instead of two-split one, and make a comparative analysis between the two different forms. According to the three-split form mentioned above, the conductor diameter and bundle spacing are optimized. The research on the electrical field calculation and split form of bundle conductor provides references for the design of substation, and has practical value for the reduction of corona noise.
Research on design of the prefabricated foundation in substations
Authors: Li Teng , Wang Yamin , Chai Linjie , Hu Shiyao , Rong Chunyan , Shen Yongpeng , Hao Junkui
Published: May 2021

With the development of power engineering, higher requirements are put forward for construction period, project investment and social environment. Traditional wet operation methods restrict the rapid development of power engineering construction. The use of prefabricated foundations in the design of substations can effectively reduce on-site wet operations, reduce construction cycles, save labor costs and increase assembly rates. This article takes the prefabricated foundation design in substation as the research object, combines actual engineering and existing construction technology, explores the technical application of the prefabricated foundation design in substation and provides a reference for the future development direction of prefabricated buildings (structures).
Analytical Modeling of Modulated Rotating-Blade Noise : the Skipping Rope and the Darrieus Wind Turbine
Authors: Roger Michel , Moreau Stéphane
Published: May 2021

The present study is about the modulations of the aerodynamic broadband noise heard from slowly rotating rotors with few blades. It is aimed at producing a fast-running prediction tool that could be used to assess the nuisance of Vertical-Axis Wind Turbines (VAWT) in the context of urban installation. The simpler case of a skipping rope that only involves part of the modulation effect is addressed as a first step. The rope is split into segments for which an instantaneous sound-radiation model exists to yield an overall spectrogram. Finally, its time signature is reconstructed by additive synthesis. After inspection of existing databases from oscillatory-airfoil experiments, needs for data representative of the dynamic stall of VAWT blades are seen as the missing block to reconstruct a synthetic spectrogram.
Influence of cavitation on the acoustic boundary conditions in water hammer experiments
Authors: Klein Sebastian , Traudt Tobias , Oschwald Michael
Published: May 2021

A water hammer event is created by stopping a flow in a pipeline using a fast closing valve. The pressure is measured at three different positions upstream the valve. Cavitation occurs close to the valve and is detected by vapour pressure in the pipeline. Frequencies in the liquid part of the pipe were measured and statistically evaluated in order to analyse whether cavitation acts as a boundary condition of acoustics.

Without cavitation one side of the pipe is an open end, while the other side is a closed end. In presence of cavitation the cavity should act like an open end due to the high change of acoustic impedance from liquid to gaseous phase. Therefore it is expected that the oscillating behavior is changing from an open/close to an open/open system. The measured frequencies indeed show a change towards an open/open configuration. It is shown that cavitation acts as a boundary condition in this system.
Flow Structure within an Aggressive S-Shaped Intermediate Compressor Duct
Authors: Kasper Aaron , Hergt Alexander , Stürzebecher Thomas , Grund Sebastian , Flamm Jasmin , Nicke Eberhard
Published: May 2021

As part of Clean Sky 2 (Engines ITD), a working group, formed by the DLR Institute of Propulsion Technology, MTU Aero Engines and GKN Aerospace, is setting up a complete compression system module (LPC/ICD/HPC). The aim of the project is to shorten the intermediate compressor duct (ICD), which connects the low pressure compressor (LPC) and high pressure compressor (HPC). This leads to a reduction of the axial length and weight of the overall engine and thus a reduction of the specific fuel consumption. In order to identify measurement-technologies and mitigate risks for this experimental set-up, a non-rotating testrig was set up in advance to investigate two different test vehicles. In a first step an ICD demonstrator was set up, which had a reduced axial length of 25%, compared to currently operating designs. This design predicted no separation or performance losses inside of the aggressive s-shaped contour. In a second step another demonstrator was installed with an even shorter axial length of 50% axial length reduction, compared to todays state of the art configurations. In this demonstrator the design was chosen to exceed the functional limit according to today’s CFD prediction and thus explore the potential for further length reduction in the future and to create a data base for numerical tool validation. The two configurations were tested at DLR Cologne. The test channel offers the possibility to use a variety of different measurement techniques to determine the flow behavior inside the ICD. This paper presents the oil streak pattern taken on the hub area between the struts and the ones taken on the pressure and suction side of the outlet guide vanes (OGV- LPC) for both demonstrators.
Jet direction control using secondary flows
Authors: Tamanoi Y , Watanabe Y , Kobayashi R , Sato K
Published: May 2021

In recent years, studies on the fundamental principle of thrust vectoring using jets have been conducted with the aim of application to next-generation aircraft. Consequently, the improvement of aircraft motion performance is expected. Previously, a method using secondary flow with a Coanda surface was proposed for the direction control of the primary jet, and some valuable results were reported. The effect of ejection or suction on the traveling direction of the primary jet was examined. However, as many physical quantities dominate the phenomenon in this complicated situation, parametric studies are insufficient. The present study is a fundamental study of fluidic thrust vectoring. The effect of secondary injection or suction flow near the Coanda surface on the travel direction of primary jets was investigated parametrically using the momentum ratio, nozzle width ratio, etc. without changing the nozzle geometry. A larger deflection of the primary jet was observed because of the suction rather than ejection at the same momentum ratio. Furthermore, the effect of the slot width ratio on the dead zone where the traveling direction of the second jet does not depend on the momentum of the secondary flow was studied.
Advanced signal processing techniques for helicopter’s gearbox monitoring
Authors: Mauricio A , Wang W , Antoni J , Gryllias K
Published: May 2021

Planetary gearboxes nowadays serve as the heart of complicated structures such as helicopters, presenting a number of advantages. They have compact size and low weight, achieving high power density and high efficiency. Moreover the gearing can be very accurate with virtually no backlash and modular, as most stages can be stacked. Furthermore, the last years planetary gearboxes have been introduced in the area of air breathing engines, helping to deliver improved efficiency over a wide range of thrusts. Planetary gearboxes consist of various shafts, gears and bearings and operate under varying conditions under excessive friction, heat and high mechanical forces. Their use in such critical applications demands for monitoring systems that can track the health condition of different components, such as bearings and gears, focusing towards early and accurate fault detection with limited rate of false alarms and missed detections, and on trending of the system degradation targeting to prognostics. Therefore the aim of this paper is the analysis of a dedicated dataset using a basic diagnostic indicator named Squared Envelope Spectrum. The indicator is applied and evaluated on a comprehensive dataset that has been generated in 1992 by Westland Helicopters Ltd (WHL), at their Universal Transmission Test Rig, testing a CH46 aft transmission, for the United States Navy.
Turbine Design and Optimization Tool for LUMEN Expander Cycle Demonstrator
Authors: Hahn R. H. S. , Deeken J. , Oschwald M. , Schlechtriem S.
Published: May 2021

This paper describes the tool created for design and optimize supersonic partial admission impulse turbine for LRE [ 1 ] application, which is commonly used in open cycle applications, while focusing on the models used to better predict the operational conditions of turbines for small thrust range engines. Also, the tool for turbine blade profile generation and the main assumptions for its optimization are discussed and the preliminary results presented, showing the possibility to improve the turbine performance for LUMEN Demonstrator operational range
Bending and torsion vibrations of a beam excited by a moving load
Authors: Holl Helmut J. , Keplinger Lukas
Published: May 2021

The linear dynamic bending- and torsion vibrations of a simply supported Bernoulli-Euler beam under a moving load with constant velocity are analysed. The main target is to derive an analytical solution of the governing partial differential equations. The deformations of the beam are computed based on the eigenmode expansion. For the computation of the solution first the method of generalized finite integral transformation is used followed by a transformation using the Laplace-Carson integral transformation. The resulting algebraic equation then is rearranged considering the boundary and initial conditions. The inverse transformation has to consider the position of the poles and after a further transformation the solution in the time domain results. The convergence and the necessary number of eigenmodes of this procedure is analysed. For the pure bending load the analysis is performed and the beam vibrations are calculated for various longitudinal speeds. For the special case of static deflections the solution is also given. The resulting deformations are plotted over time and space and the occurring phenomena are discussed. For the pure torsion deformation the Saint-Venant torsion theory is used. The described methods for solving the equations are used again. Based on the boundary and initial conditions the solution shows a similar structure like the pure bending solution. Finally the analytic solutions are compared to a numerical calculation of a finite element model which shows good agreement of the two solutions.
Reduction of the unbalance excited vibrations during the resonance passage of a rotor
Authors: Simader Victoria , Holl Helmut J
Published: May 2021

Many rotor dynamic systems are faced with large oscillation amplitudes while passing through the resonance. The coupled differential equations for the position of the center of the shaft and the rotation angle describe the dynamic behaviour of the rotordynamic system. With an appropriate external excitation the amplitude of the oscillations can be reduced. An unbalance excited oscillator is used to study the effects of a modulated angular velocity, where the angular velocity is prescribed as linear increasing with a superimposed harmonic function. The resulting excitation force is expressed as a series of Bessel functions of the first kind. In order to achieve small amplitudes near the resonance frequency of the system, special conditions for the ratio of the modulation frequency and the angular acceleration and the argument of the Bessel function of the first kind with integer order zero are derived. These requirements are first developed for a linear oscillator with an excitation force. Due to the analogy of the solution of the equation of motion these solutions are then applied directly to an unbalance excited oscillator. The results show smaller displacement amplitudes compared to the case with only linear increasing angular velocity. For the resulting motion the required torque is computed.
Investigation of Internal Flow in Centrifugal Pump Diffuser using Laser Doppler Velocimetry (LDV) and Computational Fluid Dynamics
Authors: Sugiyama Daisuke , Ichinose Asuma , Takeda Tomoki , Miyagawa Kazuyoshi , Negishi Hideyo , Tsunoda Atsuhiro
Published: May 2021

An unshrouded impeller is being developed for high head pumps to reduce costs and disk friction losses. On the other hand, research of internal flow in a diffuser did not clearly reveal flow structure. In this experiment, we measured the velocity distribution at the diffuser inlet and outlet plane using laser doppler velocimetry (LDV) to capture the flow from the unshrouded impeller. The relation between the total pressure and velocity distribution was evaluated. The circumferential velocity and meridian velocity were measured by short-focus LDV (Diode Laser, 74mW) about the circumferential and the height direction of the vane direction. Operating conditions in this steady measurement are at the design point flow rate. The result was compared with computational fluid dynamics (CFD) simulations carried out in steady conditions at the previously defined operation points. In this experiment, a phenomenon that the streamline moved toward the shroud side was confirmed. There was also a region where the static pressure increased on the shroud side at the diffuser inlet. This phenomenon was caused by the influence of the tip leakage flow of the unshrouded impeller downstream and the gap of the impeller’s main plate. Furthermore, two high velocity regions on the hub and shroud side at the diffuser outlet were observed because of the secondary flow in the diffuser. From the above studies, it was clarified that the ununiform flow in the diffuser was caused by the influence of the secondary flow in the unshrouded impeller.
Influence of Forward Skew Blade Angle on Positive Slope Characteristics of Mixed Flow Pumps
Authors: Ikuta Akihiro , Nitta Naruki , Miyagawa Kazuyoshi , Shinozuka Yasushi , Tomimatsu Shigeyuki
Published: May 2021

Under the part-load conditions, the flow instability in a mixed-flow pump could lead to strong pressure fluctuations and vibrations, posing a great threat to the safety of the system. The current paper investigates effect of the forward skew blade angle on the positive slope characteristic in a high specific speed mixed flow pump using Reynolds averaged Navier-Stokes (RANS) equations coupled with the SST k-ω model. The simulation results are compared with the experimental data and show good accordance. In the present study, five types of the mixed-flow pumps with different skew blade angles are prepared based on the conventional pump. It is found that with the increasing of the skew angle, the positive slope region becomes wider and moves towards a deeper part-load region. Further investigations are carried out by calculating the impeller head. Results depict that compared with the dynamic pressure head H
d, the static pressure head H
st plays more significant role in the formulation of the positive slope characteristic (PSC). Besides, the relative static pressure head H
rel drops dramatically while the pump operates under the positive slope region, which matches with the pump performance well. Finally, analysis on the spanwise velocity profiles are further investigated in this paper, and results indicate that the flow accumulated near the impeller hub is one of the reasons to alleviate the head drop and shift the positive slope region to a deeper part-load condition.
Influence of Fluid-Induced Forces on Cavitating Turbopumps Rotordynamics in Forced Whirl Experiment
Authors: Bertelli F. , Pasini A. , Bottai R.
Published: May 2021

As typically highlighted in the experimental results, in unshrouded axial inducers the fluid-induced rotordynamic forces are significantly dependent on the flow coefficient and do not present a quadratic behavior with respect to the whirl ratio, as commonly reported in radial pumps. Moreover these forces show destabilizing peaks that typically increase with decreasing cavitation number. The present paper illustrates the development of a theoretical model of the rotordynamic system capable of assessing the influence of fluid-induced rotordynamic forces on the dynamic response of turbopumps under cavitating/non-cavitating conditions. The implementation of the fluid-induced rotordynamic forces in the dynamic model has been proposed through the so-called F.I.R.F. model, which is applied to a test set-up for forced whirl experiments, in order to characterize the whirl natural frequencies and the relative mode shapes. The model has been successfully applied to a rotordynamic system including an unshrouded axial inducer and the corresponding computed critical speeds are summarized in the Campbell diagrams pointing out the difference between dry and wet analysis results.