Installation Space Research Articles

Modeling of Advanced Helmholtz Resonator Liners with a Flexible Wall

Acoustic liners are an effective way to dampen aircraft noise. Conventional single-degree-of-freedom liners consist of a perforated facesheet backed with a honeycomb structure and a rigid end plate. Their damping excels near their resonance frequency, which is antiproportional to the cavity depth (-resonator) or the cavity volume (Helmholtz resonator). However, this is a challenge for low-frequency noise with long wavelengths due to the limited installation space. We therefore propose a resonator in which the back cavity is divided into two cavities by a flexible plate. The aim is to combine the damping mechanisms of the Helmholtz resonator with the material damping of the flexible plate. With carefully chosen parameters, this flexible plate resonates well below the Helmholtz frequency. We derived an analytic model based on waveguide theory to predict the impedance of the resonator concept. The Helmholtz equation was solved to (numerically) determine the scattering coefficients of a channel section in which one wall is lined with the predicted resonator impedance. The predicted dissipation agreed well with experimental data from measurements at the aeroacoustic wind tunnel DUCT-R.

Research on Adaptive Fault Diagnosis Control System of Audio Management Component Environment of Airborne Electronic Equipment

The system adopts adaptive control, and the controller of audio management component is directly applied to the controlled object. Through online calculation, the model is identified online by using the dynamic characteristics of the object, and the relationship between input and output variables is expressed. It can be corrected by entering and leaving data, which is actually to correct the controller. The initial rules of the controller are composed of default models. Through continuous self-reasoning learning, the controller is optimized to achieve data tracking, fast convergence, strong anti-interference ability and excellent performance. Combining intelligent control with adaptive technology not only expands the scope of adaptive system, but also provides an effective way for intelligent control. The environmental adaptive diagnostic control system uses adaptive technology to adjust the parameters, data and knowledge base of the controller. The system detects IO signal, AD signal and the status data sent by the sub-unit through the internal CAN bus according to the power-on self-check of the unit, and at the same time, it monitors all the status data in real time during the operation, judges the operation of each sub-component, gives an alarm in time and carries out protection control. Through the design of integrated detection module, the overall installation space of detection sensors is reduced, signal interfaces and connecting cables are reduced, and the overall adaptive diagnosis effect can be improved. Through the data recording and storage function, the system stores the operation information of each subunit, compares it with the built-in health data table, and prompts the maintenance information in time.

Experimental Determination Influence of Flow Disturbances behind the Knife Gate Valve on the Indications of the Ultrasonic Flow Meter with Clamp-On Sensors on Pipelines

The aim of this work is to experimentally determine and evaluate the value of the correction factor for ultrasonic flow meters in order to improve their accuracy. This article concerns flow velocity measurement with the use of an ultrasonic flow meter in the area of disturbed flow behind the distorting element. Clamp-on ultrasonic flow meters are popular among measurement technologies due to their high accuracy and easy, non-invasive installation, because the sensors are mounted directly on the outer surface of the pipe. In industrial applications, installation space is usually limited and, therefore, flow meters frequently have to be mounted directly behind flow disturbances. In such cases, it is necessary to determine the value of the correction factor. The disturbing element was a knife gate valve, a valve often used in flow installations. Water flow velocity tests were performed using an ultrasonic flow meter with clamp-on sensors on the pipeline. The research was performed in 2 series of measurements with different Reynolds numbers of 35,000 and 70,000, which correspond to a velocity of approximately 0.9 m/s and 1.8 m/s. The tests were carried out at different distances from the source of interference, within the range of 3–15 DN (pipe nominal diameter). The position of the sensors at successive measurement points on the circuit of the pipeline was changed by 30 degrees. Flow velocity measurements were carried out for two different levels of the valve’s closure: 1/3 and 1/2 of the valve’s height. For the collected velocity values at single measurement points, the values of the correction coefficient, K, were determined. The results of the tests and calculations prove that compensation error of measurement performed behind the disturbance without keeping the required straight sections of the pipeline is possible by using the factor K*. The analysis of the results made it possible to identify the optimal measuring point at a distance from the knife gate valve as being smaller than specified in the standards and recommendations.

Permanently updated 3D-model of actual geometries of research environments

This report describes the approach to create permanently updated 3D models of research aircraft and laboratory facilities. Therefore, optical metrology scans the research environment in its raw or as-delivered condition. The result is a virtual model of the actual geometry and, in comparison to reference data (e.g. CAD-data), the smallest inaccuracies can be identified and analyzed. The exact position of non-rigid components, like riser ducts, electronics or isolation, can be determined in the models. Further changes to the layout of these facilities are permanently digitized and added to the virtual model of the environment. This can be a new recording of the entire facility or of individual areas that are affected by the changes. The individual, newly recorded models are then integrated into the existing model. This creates an always up-to-date 3D model of the research environment, which is added to its digital twin and can be observed there. In combination with CAD data, future conversion and installation measures are planned in advance and analyzed virtually in relation to the up-to-date geometry and installation space data. In addition, the virtual models of the aircraft cabins can be used to support the lengthy approval and certification process at an early stage.

Numerical Simulation on the Influence of Inlet Flow Characteristics on the Performance of a Centrifugal Compressor

Although inlet bent pipes are usually adopted due to limited installation space, the influences of different bend pipes on the inlet flow characteristics and performance of centrifugal compressors are still unclear. The numerical simulation of a centrifugal compressor is established and validated by experimental results with the case of a straight inlet pipe. Then, the internal flow characteristics of the centrifugal compressor with a 90-degree bent pipe (p90) and Z-shaped bent pipe (pz) are simulated and discussed. The results show that the adoption of two inlet bent pipes reduces the performance of the centrifugal compressor to a certain extent, which reduces more greatly with pz, with a maximum reduction of 6.82% in pressure ratio and 14.83% in efficiency, respectively. The pressure ratio and efficiency reduction of the centrifugal compressor both increase with the increment of distortion degree, which maintains the increasing trend as the flow rate increases, and the maximum distortion degree of p90 and pz reaches 0.0351 and 0.0479, respectively. The reduction degree of the pressure ratio shows a power–law relationship with the distortion degree, while the reduction degree of efficiency shows an exponential relationship with it. The flow characteristics at the outlet section of the inlet pipe affect the flow field distribution at the inlet of the impeller, and the distortion area ranges of the total pressure and axial velocity at the inlet of the impeller are near 72°–144° in the circumferential direction for p90, while those of pz are close to 108°–180° and 288°–360°. When the flow with a high distortion degree enters the impeller, a large area with high turbulent kinetic energy is formed in the downstream flow channel, resulting in an increase in the flow loss.

Optimal Design of Planetary Reducer of Electric Actuator base on NSGA-II

To solve the problem of equipment installation space shortage in industrial automation sites, a set of hybrid transmission schemes was designed with a two-stage 2K-H(NGW) planetary reducer as the main transmission mechanism combined with a fixed shaft gear train and worm gear and worm mechanism. At the same time, to obtain the design parameters of the electric actuator more quickly and accurately, with the minimum volume and maximum efficiency of the main transmission mechanism as the design objectives, the multi-objective function mathematical model is established under the conditions of meeting the gear matching, displacement coefficient, strength, and overlap degree, and the non-dominated sorting genetic algorithm II (NSGA-II) is used to solve the mathematical model. The research results show that the volume of the main transmission mechanism is reduced by 13.6%, the transmission ratio is increased by 1.54%, but the transmission efficiency is reduced by 3.32% when the strength and life of the gear are equal.

“Evaluation of an electromagnetically actuated drum brake concept”

In publications and conferences on the subject of wheel brakes, different concepts of electromechanically actuated wheel brakes can be found, as well as investigations into their suitability for the use in passenger cars. The vast majority of these brakes are disc or drum brakes, which are actuated by an electric motor. In the present publication, a brake concept is considered, that combines an electromagnetically actuated full-pad disc brake with a 10″ duo-duplex drum brake. The brake concept is researched in a project regarding brakes for autonomous shuttles and thus dimensioned using vehicle data of an example shuttle. The electromagnet was designed using finite element methods and the overall brake prototypically realized. The validation of the system design is carried out in component and system tests. The results show the suitability of the concept for the selected vehicle in terms of dynamics, installation space and energy requirements. However, there is a strong dependence of the braking torque output on the frictional sliding speed. Using hypothesis-based testing, electromagnetic effects like eddy currents are ruled out as a possible cause and the friction coefficient within the full-pad disc brake is identified as the main cause for the loss in torque. Consequently, the associated development conflict is identified and lies in the double function of the flux-carrying material in the electromagnet, which also acts as a friction partner for the braking disc.

A new prediction model for disc cutter wear based on Cerchar Abrasivity Index

The wear evolution indicated that abrasive wear is the dominant wear mechanism for disc cutter wear. Considering the uneven rolling force distribution on the cutterhead, the relative installation radius is introduced to reflect the influence of installation radius on the rolling force, and the CSM rolling force model is corrected based on linear assumption. To accurately predict disc cutter wear, the relative sliding distance between disc cutters and rock is derived based on corrected rolling force and contact theory. The effect of installation radius, cutters radius and penetration on the relative sliding distance is investigated, the results illustrated that the relative sliding distance increase with the installation radius and penetration, conversely, the relative sliding distance increase with the disc cutter radius decrease. In addition, the relationship between wear coefficient and Cerchar Abrasivity Index (CAI) is analyzed by a series CAI test. According to CAI change trend as stylus sliding distance, the effect of stylus shear failure on the abrasivity property within initial test stage was excluded. Furthermore, A new model is proposed to predict disc cutter wear based on the relative sliding distance and wear coefficient. And the effect of installation radius, cutters radius, Uniaxial Compressive Strength (UCS), CAI et al. on the disc cutter wear is investigated, the results illustrate that the disc cutter wear increase with installation radius, penetration, UCS, CAI and spacing between adjacent cutter, conversely, the disc cutter wear increase with the cutter radius and thickness decrease. Finally, the accuracy of proposed model is verified by Yintao water conveyance tunnel project. The research of parameters provides a theoretical basis for optimizing excavation parameters and reducing cutters wear.

Heavy concrete shielding properties for carbon therapy

As medical facilities are usually built at urban areas, special concrete aggregates and evaluation methods are needed to optimize the design of concrete walls by balancing density, thickness, material composition, cost, and other factors. Carbon treatment rooms require a high radiation shielding requirement, as the neutron yield from carbon therapy is much higher than the neutron yield of protons. In this case study, the maximum carbon energy is 430 MeV/u and the maximum current is 0.27 nA from a hybrid particle therapy system. Hospital or facility construction should consider this requirement to design a special heavy concrete. In this work, magnetite is adopted as the major aggregate. Density is determined mainly by the major aggregate content of magnetite, and a heavy concrete test block was constructed for structural tests. The compressive strength is 35.7 MPa. The density ranges from 3.65 g/cm3 to 4.14 g/cm3, and the iron mass content ranges from 53.78% to 60.38% from the 12 cored sample measurements. It was found that there is a linear relationship between density and iron content, and mixing impurities should be the major reason leading to the nonuniform element and density distribution. The effect of this nonuniformity on radiation shielding properties for a carbon treatment room is investigated by three groups of Monte Carlo simulations. Higher density dominates to reduce shielding thickness. However, a higher content of high-Z elements will weaken the shielding strength, especially at a lower dose rate threshold and vice versa. The weakened side effect of a high iron content on the shielding property is obvious at 2.5 μSv/h. Therefore, we should not blindly pursue high Z content in engineering. If the thickness is constrained to 2 m, then the density can be reduced to 3.3 g/cm3, which will save cost by reducing the magnetite composition with 50.44% iron content. If a higher density of 3.9 g/cm3 with 57.65% iron content is selected for construction, then the thickness of the wall can be reduced to 174.2 cm, which will save space for equipment installation.

A Compact and High-Precision Three-Degree-of-Freedom Grating Encoder Based on a Quadrangular Frustum Pyramid Prism.

A compact and high-precision three-degrees-of-freedom (DOF; X, Y, and Z directions) grating encoder based on the quadrangular frustum pyramid (QFP) prisms is proposed in this paper to solve the insufficient installation space problem of the reading head of the multi-DOF in high-precision displacement measurement applications. The encoder is based on the grating diffraction and interference principle, and a three-DOF measurement platform is built through the self-collimation function of the miniaturized QFP prism. The overall size of the reading head is 12.3 × 7.7 × 3 cm3 and has the potential for further miniaturization. The test results show that three-DOF measurements can be realized simultaneously in the range of X-250, Y-200, and Z-100 μm due to the limitations of the measurement grating size. The measurement accuracy of the main displacement is below 500 nm on average; the minimum and maximum errors are 0.0708% and 2.8422%, respectively. This design will help further popularize the research and applications of multi-DOF grating encoders in high-precision measurements.

Study of vertically mounted photovoltaic modules and their influence on the production of electrical energy in free-standing photovoltaic systems using PVGIS-CMSAF

The paper inhere explores the impact of the azimuth angle of vertically mounted bifacial photovoltaic modules on annual electricity generation. At the recent years bifacial photovoltaic modules are introduced to the market, opening new opportunities for increasing efficiency of electricity production and decreasing of the space needed for installation. The purpose of the current study is to obtain and evaluate the annual electricity production of bifacial vertically mounted photovoltaic modules in dependence on the orientation. Comparative analysis has been made between the efficiency and annual energy yield of bifacial vertically mounted PV modules and classically installed PV modules. All the calculations and analyses have been made with the aid of the software product PVGIS-CMSAF. Despite of the controversial increase of efficiency of bifacial vertically mounted photovoltaic modules compared to classically installed photovoltaic modules, the study had confirmed some of their advantages: they require less space for installation; can be used also as PV fences or noise barriers; in some cases the land of installation can be cultivated, used for agriculture or animal husbandry.

Обоснование выбора спейсера на первом этапе лечения поздней глубокой перипротезной инфекции коленного сустава

Background Periprosthetic infection develops in 0.5 to 5.0 % of cases after knee replacement, which is a social and economic problem. The most common causes of periprosthetic infection are methicillin-resistant staphylococcus aureus (MRSA) (36 %), gram-negative bacteria, and microbial associations. The study was aimed at improving the results of the sanitizing stage of revision arthroplasty in patients with periprosthetic infection of the knee joint by a developed long-acting antimicrobial composition and improving the designs of articulating spacers of the knee joint. Materials and Methods The treatment results of 121 patients with knee joint periprosthetic infection were analyzed. Nine patients had an early periprosthetic infection and 112 had a late one. Patients in satisfactory condition with stable implant components who had early periprosthetic infection underwent surgical treatment of the purulent focuses, replacement of a polyethylene tibial insert, thorough surgical wound washing using pulse lavage, drainage, and VAC-therapy. Patients with late periprosthetic infection were divided into 3 groups on the basis of the spacer used. An articulating spacer based on the developed antimicrobial composition of prolonged action (RU 191236 patent) was used in 59 patients of the first group. Preformed spacers were implanted in 29 patients of the second group, and 18 patients of the third group got a block-shaped spacer. Results An antibacterial anti-adhesive non-toxic composition with a prolonged action based on bone cement with gentamicin and such antiseptics as poviargol, dioxydine, and high-molecular polyvinylpyrrolidone has been developed. All the patients underwent the sanitizing stage of revision arthroplasty, implant removal, and spacer installation. Periprosthetic infection recurrence developed in 3 patients of the first group, 9 patients of the second group and 7 patients of the third one. The average time from the sanitizing stage to the second final stage of revision was 3-6 (4.8 ± 1.9) months. Discussion According to scientific data, the impregnation of new antibiotics into bone cement with gentamicin does not improve the antimicrobial effect of a spacer, especially in case of antibiotic-resistant strains. Block-shaped and preformed spacers lead to infection recurrence and complications. Antiseptic impregnation with different mechanisms of action is able to affect antibiotic-resistant bacteria, and the polymer is able to prolong the effect. Conclusion The use of articulating spacers for the knee joint, which include an antimicrobial composition, allows preserving the function of the joint and reducing the number of infectious complications, which facilitates the final stage of revision arthroplasty.

Dual-Band Dual-Polarized Antenna Using a Simple Radiation Restoration and Decoupling Structure

This letter presents a simple structure dual-band dual-polarized antenna. The higher-band (HB) antenna is located coaxially under the lower-band (LB) one to save the installation space. The blocking effects of the LB antenna seriously deteriorate the HB antenna's radiation patterns. To solve this problem, we first introduced four stacked patches to restore the radiation performance. Unfortunately, using the stacked patches, the isolation between the LB and HB antennas reduces from about 25 to 20 dB. Then, we introduced four C-shaped metal strips as the decoupling structure and the isolation improves from 20 dB to more than 30 dB within a wideband. These stacked patches and metal strips are printed on top and bottom sides of the LB antenna substrate and therefore no extra substrate layer is needed. For demonstration, a prototype of the dual-band antenna operating at 1710–2690 MHz (LB) and 4200–5000 MHz (HB) is implemented. Normal directional radiation patterns are obtained with stable in-band gains of 7.5 and 9.5 dBi. Better than 33 dB measured isolation between the LB and HB antennas is realized.

An Atlas-Based Approach to Planar Variable-Structure Cable-Driven Parallel Robot Configuration-Space Representation

Variable-structure cable-driven parallel robots (VSCR) are a new class of cable robots that are able to cover nonconvex installation spaces by permitting collisions between cables and fixed objects in the environment. In this article, we show how the configuration space of a general planar VSCR can be represented as an organized set of partially overlapping regions of constant structure. The benefit of this representation, which we refer to as the “structure atlas,” is that it allows any techniques from the established cable-driven parallel robot literature to be applied locally, greatly simplifying the modeling complexity associated with VSCRs. A complete method for how such a representation can be constructed is provided, which includes identifying the set of reachable kinematic structures for a given VSCR and the area where each structure is active. We then give specific examples of how this new representation can be used for performing VSCR workspace analysis and directly solving the VSCR inverse kinematics problem. Our results are demonstrated with the aid of simulated and experimental results.

전력계통 네트워크 통신방식 변화에 따른 사이버위협 분석 및 대응방안 제시

The Energy Management System (EMS) communicates with power plants and substations, monitors the substations and plant operational status of the transmission and substation system for stability, continuity, real-time, and economy of power supply, and controls power plants and substations. Currently, the power exchange EMS communicates with power plants and substations based on the serial communication-based Distributed Network Protocol (DNP) 3.0 protocol. However, problems such as the difficulty of supply and demand of serial communication equipment and the lack of installation space for serial ports and modems are raised due to the continuous increase in new facilities to perform communication, including renewable power generation facilities. Therefore, this paper presents a TCP/IP-based communication method instead of the existing serial communication method of the power exchange EMS, and presents a security risk analysis that may occur due to changes in the communication method and a countermeasure to the security risk.

Ventilation duct silencer design for broad low-frequency sound absorption

Low frequency sound absorption in ventilation duct is an important technical issue. In this study, silencer consisting of decoupled annular Helmholtz resonators (AHR) is designed to achieve low frequency sound absorption. The proposed silencer can achieve broadband sound absorption whilst avoiding hindering ventilation. Theoretical model that based on the temporal coupled mode theory (TCMT) is derived to reveal the working mechanism. To improve feasibility of the designed silencer and to reduce the required space for installation, arc-shaped Helmholtz resonator (ASHR) is then proposed as optimisation. Such structure allows the silencer to produce multiple peak absorption frequencies in a smaller dimension. The sound absorption performance of both the structures is investigated numerically and experimentally. For the AHR silencer, measured results indicate a >95% sound absorption coefficient from 690 Hz to 1350 Hz. The ASHR silencer can generate four effective peak absorption peaks over the range 570–1720 Hz. In addition, both structures are installed as the side-branches of the duct, so ventilation condition is completely not affected. The usage of porous materials prevents design process from repeated geometrical parameter tuning and enables continuous operational frequencies. The proposed designs are experimentally verified to possess good feasibility for practical application.

Optimal switching sequence control for current stress reduction of DC-link capacitors in dual-three phase PMSM drives

The safety and installation space of DC-link capacitor is crucial for dual-three phase permanent magnet synchronous machines (DTPMSM) drives in industrial applications. Reducing the capacitor current stress can contribute to decrease the designed capacitor value and install size, thus enhance safety of drives fed by two parallel inverters. Therefore, an optimal switching sequence control scheme for DTPMSM drives is proposed to reduce the DC-link capacitor current stress in this paper. For DTPMSM drives, the maximum four adjacent voltage vectors control (MFAVC) method is usually adopted due to its control flexible and stability characteristic. Based on MFAVC, the capacitor current can be derived though the current reconstruction theory to reorder the current amplitude over one switching period. Through the rearrangement of voltage vector and duration, the theoretical analysis of capacitor current reduction is presented. On this basis, the optimal switching sequence control method can be implemented based on the minimized current sum of the two inverters. The performance of proposed method has been evaluated via. comparatively experimental tests on a prototype 3 kW DTPMSM drive, which shows superior features on reducing capacitor current stress. Furthermore, it is also found that the proposed method is helpful to redesign a small capacitor value for DTPMSM drives.

Owl-Neck-Spine-Inspired, Additively Manufactured, Joint Assemblies with Shape Memory Alloy Wire Actuators.

Nature provides a considerable number of good examples for simple and very efficient joint assemblies. One example is the enormously flexible cervical spine of American barn owls, which consists of 14 cervical vertebrae. Each pair of vertebrae produces a comparatively small individual movement in order to provide a large overall movement of the entire cervical spine. The biomimetic replication of such joints is difficult due to the delicate and geometric unrestricted joint shapes as well as the muscles that have to be mimicked. Using X-ray as well as micro-computed tomography images and with the utilisation of additive manufacturing, it was possible to produce the owl neck vertebrae in scaled-up form, to analyse them and then to transfer them into technically usable joint assemblies. The muscle substitution of these joints was realised by smart materials actuators in the form of shape memory alloy wire actuators. This actuator technology is outstanding for its muscle-like movement and for its high-energy density. The disadvantage of this wire actuator technology is the low rate of contraction, which means that a large length of wire has to be installed to generate adequate movement. For this reason, the actuator wires were integrated into additively manufactured carrier components to mimic biological joints. This resulted in joint designs that compensate for the disadvantages of the small contraction of the actuators by intelligently installing large wire lengths on comparatively small installation spaces, while also providing a sufficient force output. With the help of a test rig, the developed technical joint variants are examined and evaluated. This demonstrated the technical applicability of this biomimetic joints.

Evaluation of linear stability operating boundary for voltage source converter under grid faults

Voltage source converters have been used in high voltage direction current systems, which provides various advantages such as reduction in installation cost and space, easy connectivity with renewable energy sources and enhanced power quality. One of the most important issues is how to ride through the grid faults to ensure the stability operation of voltage source converters. In practice, however, there are practical considerations of physical restrictions such as the linear stability operating boundary, beyond which the current would be distorted, even the system would be instable. In this paper, a quantitative analysis and evaluation of the linear stability operating boundary is presented for operating the voltage source converter under grid faults. The proposed method indicates that the operating boundary mainly depends on the circuit parameters and control strategies. Simulation results have provided to verify the proposed quantitative analysis and control strategy. It is expected to provide a useful guidance for designing and controlling the voltage source converter within the linear stability operating boundary, which enhances the system and increased the reliability of the system.

Simulation methodology for the identification of critical operating conditions of planetary journal bearings in wind turbines

The usage of journal bearings as planetary bearings in wind turbines instead of roller bearings has become more common in recent years. Their usage is advantageous, due to smaller installation space needed compared to roller bearings allowing for higher power densities of wind turbine drive trains. However, this technology presents a challenge since there is currently no standardized approach for the design of planetary journal bearings regarding wear. Due to varying wind speeds and dynamic operating events a large variation of loads has to be considered in the design process of a planetary journal bearing for wind turbines. Some of these loads are considered potentially critical to the journal bearing in terms of wear. Identifying these critical load areas early in the design phase supports a reliable bearing design and wind turbine operation.This paper introduces a method to identify critical operating conditions for planetary journal bearings using a simulation tool chain, which couples a multi body simulation (MBS) model of a wind turbine with an elasto-hydrodynamic (EHD) model of the planetary journal bearing. Based on the EHD results critical operating conditions are determined for the planetary bearing. Furthermore, methods are implemented to reduce the number of required EHD simulations for analysing the bearing design. The combination of the identification of critical operating conditions, while reducing the computational effort leads to a simulation methodology, which enables a faster bearing design assessment considering the wide variation of wind turbine operating conditions. The applicability of this method is demonstrated by a simplified use case.Firstly, this paper introduces the MBS model and the parameter space that describes possible combinations of bearing loads such as forces, moments and rotational speed. Due to the number of combinations and the EHD computing effort, the identified parameter space is secondly sampled statistically to reduce the simulation effort. A risk map is derived from the EHD results, to easily indicate potentially critical operating conditions for the planetary journal bearing.