Existing Calculation Methods Research Articles

Leakage Characteristics and Experimental Research of Staggered Labyrinth Sealing

The staggered labyrinth seal is widely used in aerospace, transportation, mining, and other fields due to its advantages of adapting to high speed, reliable sealing performance, and low or even frictionless friction between dynamic and static rotors. The traditional calculation method of labyrinth seal leakage mostly focuses on the fact that the internal medium is an ideal gas and only considers a single effect, which cannot accurately describe the leakage of liquid medium lubricating oil in the labyrinth seal. Therefore, this study focuses on the leakage characteristics of labyrinth seals, and it proposes a leakage calculation method based on liquid medium in view of the shortcomings of existing calculation methods under liquid medium conditions. By considering the thermodynamic and frictional effects of the staggered labyrinth sealing, the resistance loss and thermodynamic effect of the lubricating oil in the sealing cavity were analyzed. The flow field analysis was used to reveal the leakage law of lubricating oil under different conditions, and the factors such as total inlet pressure, spindle speed, and sealing clearance were considered. Finally, the leakage characteristics of the staggered labyrinth seal and the accuracy of the calculation method of the leakage of the staggered labyrinth seal under multiple effects were revealed through experimental verification. This study provides useful guidance for the performance optimization of labyrinth seals in practical applications.

Tension performance of joint made in cold-formed square tube with self-tapping screw connections

The tension behavior of cold-formed square tube (CFST) screw connections was investigated experimentally and numerically. Ten test specimens were fabricated from the square tubes connected by external steel plates and internal tube applying self-tapping screws such that the number of screws was varied. In addition, the mechanical properties of the single-screw connections were obtained through single shear tests. Experimental results revealed that an increase in the number of screws led to higher bearing capacity and stiffness in the specimens. Shear failure of the screws was observed as the primary failure mode. When the number of the screws was equal in both types of the specimens, those with the internal tube exhibited superior tensile behavior than the ones with external steel plates. Subsequently, finite element (FE) models of the test specimens were developed. Upon validation of the test results, an extensive parametric study was conducted to further examine the influence of the design parameters on the tensile behavior of the CFST screw connections. Variation of the arrangement of screws, wall thickness of steel plates and their strength had only a minor influence on the tension behavior, and steel strength had little influence on the tension behavior and the number, spacing, and diameter of the screws were the key parameters affecting the tension behavior of the CFST screw connections. Based on the test results and FE analyses, the existing calculation method was modified, and a formula for calculating the tensile bearing capacity of the CFST screw connections was obtained. Comparison with the results indicate that the formula was conservative and reliable for determining the tensile capacity of CFST screw connections.

Comparative analysis of acoustic calculation methods for throttling devices

Objective. The identification of increased noise levels from ventilation systems during the operation of buildings necessitates complex and costly procedures to detect and eliminate noise sources, conduct dismantling work, install additional silencers, or replace ventilation equipment. Therefore, accurate acoustic calculations are one of the most critical tasks in the design of various facilities. Method. This article presents an analysis of domestic and international methods for determining the noise generated by throttling devices. The accuracy of the calculation results was evaluated by comparing them with data from field tests. Result. A sharp increase in sound power level within the throttling device was observed when the blade angle exceeded 60 degrees, significantly impacting the acoustic environment of the premises and leading to an exceedance of regulated noise levels. Conclusion. The conducted comparative analysis of existing calculation methods revealed that the domestic calculation method provides the required margin for the sound power level of the throttling device across all octave bands. A notable drawback of international calculation methods is the lack of consideration for the acoustic impact of duct fittings and the connection of the duct to the throttle, which underscores the need for further validation of these methods for complex systems.

A building operational carbon emissions database of 362 Chinese cities: Construction process and spatiotemporal characteristic analysis

The existing calculation methods of city building carbon emissions based on energy audits, city statistics and energy balance sheets have problems such as time-consuming and labour-intensive, missing data and large errors, resulting in the lack of a complete and accurate database of city building carbon emissions in China. To address this, the calculation method based on city statistical data (CSD-M) and the calculation method based on provincial energy balance sheets (PEB-M) were used to calculate the carbon emissions from city buildings. The PEB-M was corrected using CSD-M results, reducing the error to 12.8%. Based on CSD-M and modified PEB-M, a database of building carbon emissions in 362 Chinese cities was developed. Finally, the spatio-temporal characteristics of city building carbon emissions in China were analysed, and the current situation of carbon emissions in different cities was compared. This study provides a basis for future carbon reduction policies tailored to city characteristics.

Interaction characteristics between the large ship-rubber fenders-wharf structure in deep-water considering the flexibility of the wharf structure

High pile-supported wharf structures in offshore deep water have significant flexibility due to long free ends and large slenderness ratios of the pile bodies, resulting in substantial deformation of the pile body under kinds of loads. In the design of this new type of wharves, it is expected to consider the characteristic of elastic deformation of pile body absorbing a portion of the ship impact energy reasonably. However, the existing calculation method still adopts the theoretical formulas of traditional wharf structures, failure to incorporate this advanced design concept fully. In order to solve this, firstly, a comprehensive three-dimensional numerical simulation model encompassing large ship, rubber fenders and wharf structure, was developed using Ansys/LS-Dyna, and the calculation model was validated against the existing research results. Subsequently, dynamic response characteristics of wharf structures during the normal berthing of ships were examined meticulously, and the variations in absorption energy and reaction forces of rubber fenders and wharf structures were analyzed systematically. And then the analysis results were compared with previous research, the limitations of the existing design code for wharf structures were discussed as well. Finally, the findings demonstrate that peak values of absorption energy and energy transfer times increase with the increase of ship loading capacities. And the elastic deformation of the wharf structure indeed absorbs considerable partial of the impact energy effectively, with about 30 % for conditions in this study, leading to lower impact forces acted on the wharf structure. Moreover, the maximum pile top displacement of the wharf structure is also smaller than that reported in the existing literature in the same load condition, indicating that considering the structural flexibility in the design of this new type of wharf structure is more in line with reality, and it is more reasonable and economical as well.

Review about evaluation methods of recoverable reserves of deep water drive gas reservoirs in China

It has been widely accepted that China is one of the biggest natural gas consumers. Related to the imports of LNG, China stands in a very uncomfortable situation. Most domestic gas reservoirs fall within deep water drive gas reservoirs inordinately, which has entered the production depletion stage. Accurate estimation of SEC recoverable reserves of deep water drive gas reservoirs is of great significance for gas consumption planning and peak shaving. The existing calculation methods of recoverable reserves mainly consist of static methods and dynamic methods. In the early stage of exploration and development, the volumetric method has often been utilized to calculate the recoverable reserves. With the continuous development of gas reservoirs, the main methods for evaluation are dynamic methods, including the successive subtraction of production method, water drive curve method, prediction model method, attenuation curve method, improved virtual curve method, and material balance method for deep gas reservoirs.

Approaches to calculation of waterpermeable structures made of metal corrugated structures for static and dynamic loads

Problem. Today, approaches to the calculation of road culverts from metal corrugated structures do not have unified approaches, almost every country that produces metal corrugated structures has its own individual calculation approaches. Goal. The work presents the main approaches to the calculation of culverts made of metal corrugated structures for static and dynamic loads. Methodology. The analysis was carried out of the deflection theory, the ring compression theory, the theory of buckling. Results. On the basis of the conducted research, the need to improve the existing approaches in Ukraine has been established. Originality. The work considers the most common approaches to the calculation of road culverts in the USA, Canada, and Europe. Practical value. The work considers the most common methods of calculating road culverts from metal corrugated structures to solve the task of determining the advantages and disadvantages of existing calculation methods, which make it possible to analyze and choose the most perfect solution for calculating the stress-strain state.

Calculation of Column Pile Heave in Deep Excavation Based on the Rebound–Recompression Method

Excessive column pile heave may result in engineering disasters such as instability of retaining structures and cracking of existing engineering piles in deep excavations. However, factors such as support weight, changeable support restraint resistance, and soil disturbance at the bottom of the excavation are often ignored or simplified in existing calculation methods but have a significant impact on the calculation results. Based on field soil parameters obtained by the rebound–recompression method, a semi-analytical method is proposed for estimating column pile heaves in a deep excavation. This method considers the influence of soil disturbance, the weight of the retaining structure, and the changeable horizontal support restraint, making the calculation result more consistent with the realistic situation. This method can also be used to analyze load transfer between the pile and the surrounding soil. The rationality of this proposed calculation method is verified by measured data, where the variation in pile stress state during deep excavation is analyzed. Finally, a parametric study is conducted, and the results show that the excavation size and the excavation depth have a great influence. However, the heave is hardly affected by the value of the limit relative displacement. The use of long piles with small diameter and the method of small block excavation are effective means to control the column pile heave. When the excavation area is large or the effective pile length is short, the factor of the position of the column pile cannot be ignored.

Calculation Method for the Transient Hot-Spot Temperature Rise of Oil-Immersed Bushing in High-Speed Railway

Traction oil-immersed bushing is the only channel for connecting the high-speed railway system with the external power grid, and its transient hot spot is one of the most important factors reflecting its operation status. Since the traction load of a high-speed railway has obvious impulse characteristics, the existing calculation method for bushing given in IEEE Std C57.19-100™-2012 is incompatible because it is designed for steady electrical loads. Thus, in this paper, the equivalent hot spot temperature rise of the bushing under varying traction loads is calculated by the traction parameters (i.e., operating time <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_ot</i> , interval time <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_it</i> , and per unit transient traction current <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_tc</i> ). Then, the difference value of transient hot spot temperature rise is modified by analyzing the change of transient hot spot temperature rise under varying traction loads. Finally, a calculation method is proposed for the transient hot spot temperature rise of the oil-immersed bushing in high-speed railway under different traction loads. A case study of a 110 kV oil-immersed bushing shows that the proposed method is speedy and accurate.

ПРОЕКТИРОВАНИЕ ГРУНТОВЫХ АНКЕРОВ. УЧЕТ ТОРЦЕВОГО СОПРОТИВЛЕНИЯ УШИРЕНИЯ ГРУНТОВОГО АНКЕРА ПРИ РАСЧЕТЕ ЕГО НЕСУЩЕЙ СПОСОБНОСТИ ПО ГРУНТУ.

Currently, ground grouted anchor systems are widespread in geotechnical construction. One of the stages of anchor system designs is ultimate load-holding (bearing) capacity calculation. To date, a clear methodology for calculation the bearing capacity of a ground anchor is not presented by the current regulatory documents. On the other hand, the existing calculation methods for determining the bearing capacity of the anchor (which are presented in SP 381.1325800, VSN 506-88, TSN-50-302-2004 and others) do not take into account all geometric parameters and technological factors. Therefore, the results of determination bearing capacity are significantly lower than the actual ones. Also, the calculation of the bearing capacity is reduced to determination the lateral surface resistance of the anchor’s cylindrical body only. An end-bearing resistance component of the fixed anchor is not taken into account by calculation. This article raises the issue of reliable determination of the ground grouted anchor’s calculated bearing capacity, taking into account all geometric and technological factors, and also considers the stress-strain state of soil and the destruction mechanics.

Double-local conditional probability based fast calculation method for approximation regions of local rough sets

As an important extension of classical rough sets, local rough set model can effectively process data with noise. How to effectively calculate three approximation regions, namely positive region, negative region and boundary region, is a crucial issue of local rough sets. Existing calculation methods for approximation regions are based on conditional probability, the time complexity is O (|X||U||C|). In order to improve the computational efficiency of three approximation regions of local rough sets, we propose a double-local conditional probability based fast calculation method. First, to improve the computational efficiency of equivalence class, we define the double-local equivalence class. Second, based on the double-local equivalence class, we define the double-local conditional probability. Finally, given the probability thresholds and a local equivalence class, the monotonicity of double-local conditional probability is proved, on this basis, a double-local conditional probability based fast calculation method for approximation regions of local rough sets is proposed, and the time complexity is O (MAX (|X|2|C|, |X||XC||C|)). Experimental results based on 9 datasets from UCI demonstrate the effectiveness of the proposed method.

D-Q Axis Inductance Analytical Calculation for Fractional-Slot Distributed Winding IPM Motor Based on Big-Small Pole Space Method

The d-q axis inductance is the crucial parameter for the interior permanent magnet (IPM) motor. In order to facilitate the design, analysis, and optimization of IPM motors, it is of great significance to develop an accurate and simplified inductance analytical calculation method. Among the existing calculation methods, the magnetic equivalent circuit (MEC) has advantages in the inductance calculation of the IPM motor due to the simple modeling, the fine processing of the saturation region and the visualization of the magnetic field distribution. However, the traditional MEC method is only applicable to the IPM motor with integer-slot distributed winding (ISDW) or fractional-slot concentrated winding (FSCW), while lacking of in-depth research on fractional-slot distributed winding (FSDW). The magnetic circuit topology of FSDW IPM motors is not as single as that of FSCW/ISDW IPM motors. It leads to problems in the traditional MEC method when dividing the d/q axis flux path in FSDW motors. To solve this problem and expand the applications of MEC method, a big-small pole space (BSPS) method is proposed after fully considering the common characteristics of MMF distribution and reluctance distribution in FSDW motors, which fills the gap of MEC method applied to FSDW motors. The BSPS method divides the d-axis flux path according to the asymmetry of the d-axis magnetomotive force (MMF). Based on the divided flux paths, an improved nonlinear MEC model that considers the saturation of stator and rotor is established to calculate d- and q-axis inductances. The results of finite element analysis (FEA) verify the validity of the proposed MEC model with different geometry parameters. Experimental results of an 84-pole/360-slot FSDW I-type IPM wind generator further confirm the validity of the proposed MEC model

ОСОБЛИВОСТІ РОБОТИ НАПІРНИХ ПОХИЛЬНИХ ЗБІРНИХ ДРЕНАЖНИХ ТРУБОПРОВОДІВ ЗА НАЯВНОСТІ ПОХИЛУ РІВНЯ ҐРУНТОВИХ ВОД

The development of a reliable methodology for calculating drainage pipelines in reclamation systems is crucial for en-hancing agricultural production efficiency and optimizing the use of water and land resources.Many existing calculation methods do not consider the simultaneous influence of pipe slope and groundwater level slope on the characteristics and operating conditions of collecting drainage pipelines. Addressing this issue will contribute to the advancement of modern hydraulic engineering and hydromelioration.The purpose of the article is to develop a methodology for calculating the parameters of pressure collecting drainage pipelines in reclamation systems, which are laid with a slope and operate in the presence of a groundwater level slope.A system of differential equations describing the liquid motion in collecting drainage pipelines laid with a slope and operating with a certain groundwater level slope is presented in the article. This system includes a variable mass hydraulicsequation and a modified filtration equation. The original system is reduced to a dimensionless form by introducing new vari-ables. The solution to the equations system results in straightforward and easy-to-use analytical dependencies for calculating the main hydraulic and structural characteristics of precast drainage pipes.The analysis employs the concept of an infinitely long drainage pipeline operating with a groundwater level slope, equivalent to an inclined pipeline with an infinitely filtering capacity of the side surface walls. The impact of drainage pipe geometric slope and groundwater level on its design charac-teristics is evaluated.The obtained dependencies for calculating collecting drainage pipelines will enhance the efficiency and reliability of drainage systems, improve resistance to extreme weather conditions, reduce energy consumption and enhance adaptation to various operating conditions

УСТОЙЧИВОСТЬ И РЕЗЕРВЫ ЭКОЛОГИЧЕСКОЙ СИСТЕМЫ

Addressing global environmental challenges such as climate change, natural resource depletion and pollution requires effective international cooperation and a coordinated policy framework. Over the past decades, many important international treaties and agreements have been developed and adopted to address these challenges. Assessing and maintaining environmental sustainability plays a key role in developing and implementing effective conservation strategies. The article discusses issues related to the essence of sustainability of the ecological system. Emphasis is placed on the systematization and characteristics of its reserves (taking into account existing calculation methods).

Fast Calculation of Electromagnetic Vibration of Surface-Mounted PMSM Considering Teeth Saturation and Tangential Electromagnetic Force

In view of the shortcomings of the existing calculation methods of electromagnetic forces, this paper proposes an analytical method (AM) combining the magnetomotive force (MMF)-permeance method and the improved subdomain method. The amplitude of each force density component considering stator teeth saturation and current harmonics is calculated, and the specific order and frequency components in the radial and tangential electromagnetic force densities are analyzed and sorted out. In modal analysis, the stator core and the casing are regarded as cylindrical shells with axial ribs, the natural frequencies of the stator are obtained based on the energy method, and the accuracy is well verified by the modal test. Finally, the frequency response functions of low-order modes of the stator only related to the stator structure parameters are determined, and the vibration accelerations under different working conditions are obtained based on the linear superposition principle by only updating the electromagnetic forces. Compared with the multi-physical coupling finite element analysis, the total calculation time of the proposed AM is reduced by more than 92%, which facilitates the fast prediction and effective reduction of electromagnetic vibrations in the motor design stage.

Determination of the stress-strain state of models of steel cylindrical tanks using the “ANSYS” program

In the world, metal cylindrical shell constructions occupy a leading position in the construction of reservoirs for various purposes, bodies of water pressure generating towers, television towers, chimneys, lighting masts, tower cranes and similar engineering structures. In this direction, in developed countries such as the USA, Germany, Japan, and Russia, special attention is paid to increasing the load-carrying capacity of cylindrical shell structures, ensuring earthquake resistance and priority, reducing metal consumption, preventing the resulting deformations, and thereby ensuring their reliable operation. In this regard, one of the important tasks is to increase the priority of various construction structures, optimize their shape and size, improve existing calculation methods, and develop modern advanced methods of construction preparation and assembly.

Методология влияния свободной порозности и водоотдачи на процессы, происходящие в почвогрунтах оросительных каналов с земляным руслом

Purpose of the research: to consider the influence of free porosity and water loss on the filtration of water from channels with an earthen bed. Explore existing calculation methods taking into account the parameters of free porosity and fluid loss. Collect calculation material that can form the basis of a program for calculating the filtration of channels with an earthen bed, taking into account the factors influencing the first and second stages of filtration in the channels. Materials and research methods: The work used theoretical methods for calculating filtration in channels with an earthen bed, presented the calculation of the loss of flow rate Qf for filtration per 1 km of length with a steady free surface for different types of channel cross-sections, considered the basic formulas proving that water supply changes with changes in transverse cross-section of the canal, the change in the stability of the canal slopes is shown, a test calculation of the canal for filtration strength according to the maximum pressure gradients is presented, the need to compare the excess of the critical filtration pressure gradient with the permissible pressure gradient is considered. Results and its discussion. The relationship between the total, capillary and minimum moisture capacity and water yield in the thickness of soils is presented, the dependence of free porosity on the groundwater level, and the change in water permeability of soils over time are considered. As a result of the research, material was collected on the influence of free porosity and water loss on the movement of water in soils and the influence on the increase in groundwater levels in the zone of influence of canals, a methodology was presented for the influence of free porosity and water loss on the processes occurring in the soils of irrigation canals in an earthen channel, which will allow its use for modeling these processes on a computer.

Численная оценка устойчивости и деформативности конструкции земляного полотна методом замены слабого грунта на слабых основаниях

A pressing issue for the railway industry is to enhance the stability and reduce the deformability of earth embankment structures constructed on weak foundations using the method of replacing weak soil. The authors determined the width of the weak soil at the base, requiring replacement, taking into account the requirements for deformability indicators that ensure the specified geometric parameters of the earth embankment under various soil foundation conditions. The numerical modeling was based on established theoretical principles in accordance with the sequence of construction stages for a high-speed railway line on weak foundations using the geotechnical software Plaxis 2D. By considering and evaluating different thicknesses of the weak soil layer to be replaced, the authors constructed a graph of the dependence of deformation on the principal stress at the point of plastic deformation development, and determined the value of the stable safety factor. The research made it possible to propose a numerical method for determining the slope stability coefficient. Analysis of current regulatory documents and calculation methods for earth structures on weak soils has confirmed the need to refine existing calculation methods.

Transfer Function for a Controllable Pitch Propeller with Added Water Mass

Abstract The relevance of this study lies in the fact that it presents a mathematical model of the dynamics of the propulsion system of a ship that takes into consideration the mass of water added to it. The influence of this phenomenon on the resonant frequencies of the propeller shaft is examined, and a transfer function for a controllable-pitch propeller is obtained for various operating modes. The purpose of the study is to improve the calculation of the dynamic operating modes of a controllable-pitch propeller by examining the features of a visual models. The VisSim software package is used in the study. A visual model is developed that considers the influence of the rotational speed on the value of the rotational inertia attached to the variable-pitch screw of the mass of water, and a special transfer function is proposed. The study shows that a transfer function of this type has a loop enabling negative feedback. An analysis of the operation of the propeller shaft at its resonant frequency is conducted based on the application of frequency characteristics using the transfer functions obtained. We show that in the low-frequency region, a consideration of the added rotational inertia using the proposed transfer function leads to a significant difference compared to the result obtained with the existing calculation method.

Experimental study on the wind-induced buckling of open-top storage tanks with wind girders via 3D-DIC technique

Large open-top storage tanks are susceptible to buckling failure under the combination of external and internal wind pressures. Therefore, wind girders are recommended to be installed on the tank wall to improve its buckling capacity. Most previous experiments on buckling of cylindrical shells typically measured the response at a certain point with a single displacement sensor, and the buckling modes are not readily available. In this study, a measurement technique based on the three-dimensional digital image correlation method is utilized to analyze the buckling behavior of several elastic tank models with aspect ratios of 0.5 and 0.2 in the boundary layer turbulence. The critical buckling pressure and instantaneous displacement field on the windward side of models with and without wind girders are presented and compared with the results of finite element analysis. In addition, the effects of wind girders and imperfections are further discussed. The results indicate that the deformation of the tank wall can change the wind pressure, making it more difficult to return to the pre-buckling state. The wind girders can significantly restrain the buckling deformation and increase the critical buckling load. However, as the wind girders become rigid, the strengthening effect becomes almost constant, and the stiffened tanks are more sensitive to initial geometric imperfections. Based on the cylindrical shell buckling theory and existing calculation methods, an empirical formula for the critical buckling wind pressure of open-top storage tanks with different numbers of wind girders in the boundary layer is proposed.