Rectangular Pipe Research Articles

Effect of cutting blind zones on the performance of the rectangular pipe jacking machine with multiple cutterheads: A DEM study

Due to the shape discrepancy between the rectangular machine shell and the circular cutterhead, rectangular pipe jacking machines inevitably have cutting blind zones, which could waste thrust force and reduce tunneling efficiency. Few studies have been done in the past on the effects of the cutting blind zones on the jacking behavior of the rectangular tunneling machine. To investigate the performance of the rectangular pipe jacking machine under the influence of excavation blind zones, three-dimensional discrete element modeling was performed in this study, where various blind zone ratios (i.e. the area ratio of excavation blind zones to the rectangular excavation face) ranging from 2% to 10% were considered. The resultant velocity distributions of soil particles indicate that the soil stagnation phenomenon in the cutting blind zone near the non-overlapping zones between adjacent cutterheads can be alleviated by the staggered front-to-back arrangement of multiple cutterheads, while the stagnation phenomenon in the cutting blind zone close to the pipe shell is remarkable. Besides, it was advisable to keep the cutting blind zone ratio at about 5% in practical construction in view of the extra costs of over-arranging multiple cutterheads for a small cutting blind zone ratio as well as the waste of thrust force caused by an excessively large cutting blind zone ratio. Additionally, structural optimization strategies were proposed, which were intended to provide some guidance for the future design and improvement of rectangular pipe jacking machines.

Features of operation and hydraulic calculations

Issues related to the design and hydraulic calculations of the transit part of a closed tubular water supply structure of the siphon type are considered. The operating conditions of a siphon with rectangular pipes in the transition mode are estimated. Due to the formation of a hydraulic jump, the inlet section of the siphon pipes experiences increased hydrodynamic loads, leading to certain defects and destruction. The design of the siphon with two breaks along the length with a portal and a smooth inlet head or without it was modeled. As a result of modeling studies, the absence of a noticeable effect of the inlet head of the culvert on the length of the free-flow inlet section was established. It was revealed that the conditions of formation, the features of the hydraulic operation of the siphon, and the loads it experiences in the transient mode are largely determined by its design solutions. With the flooding of the inlet head, the flow of air into the pipe is hindered, and a transition mode of the second type is formed with a slight fluctuation in the water level in front of the structure upstream. The dependence of the location of the flow separation point with a decrease in the throughput of water on its value was revealed, which made it possible to obtain a graph of the dependence of the relative length of the free-flow section on the square root of the Froude number. A comparison was made with the results of studies by other authors, which showed an increase in the relative length in tubular structures of the siphon type in sections with reverse slopes at the same Froude numbers. Recommendations are given on the methodology for carrying out hydraulic calculation of tubular culverts for various purposes with minimal flow rates, and ways for further multifactorial studies of siphons on the reclamation network are indicated.

Feasibility study of simplified pipe modeling for analyzing thermal performances of radiant heating and cooling systems

Energy-efficient radiant heating and cooling require surface temperature and thermal capacity analysis. Simplified pipe modeling is applied to save time and resources for numerical analysis when evaluating the radiant system. Therefore, this study investigated the surface temperature distribution and thermal capacity of a radiant system using simplified pipe modeling. To do this, a steady-state heat transfer simulation was performed using Physibel BISCO. The difference between detailed (circular) and simple (rectangular) pipe models and the effect of material thermal conductivity of various layers were analyzed in three types of radiant heating and cooling systems: Embedded Surface System (ESS), Thermally Activated Building System (TABS), and Cooling Radiant Ceiling Panels (CRCP). The simple and detailed ESS and TABS simulation results showed similar surface temperature and heat capacity in various materials. Also, the CRCP simple and detailed models for materials differed in surface temperature and heat capacity, especially when the pipe thermal conductivity was high. The CRCP simple model overstated surface temperature and thermal capacity, which needs heat resistance to solve this overestimation. Further studies are necessary to investigate the discrepancy with different dimensioning and operation conditions, such as water temperature and flow rate.

Failure Envelope of an Underground Rectangular Pipe Gallery in Clay under Pipe–Soil Interactions

Failure Envelope of an Underground Rectangular Pipe Gallery in Clay under Pipe–Soil Interactions

Optimization of construction parameters of large rectangular pipe jacking in saturated soft ground

Optimization of construction parameters of large rectangular pipe jacking in saturated soft ground

Efficient sunlight harvesting with combined system of large Fresnel lens segmented mirror reflectors and compound parabolic concentrator without tracking sun for indoor daylight illumination

Sunlight is a great substitute for indoor artificial lighting during the daytime but still isn't so viable because of the cost of fiber-based daylighting system and its efficiency. In this paper, we report the design and development of a cost-effective non-mechanical tracking-based solar concentration system using a combination of a large Fresnel lens, segmented mirrors, and segmented compound parabolic concentrator (SCPC) for indoor daylighting application. This system presents the three-stage collection of sunlight by means of extending the collection aperture vertically while keeping the horizontal area same. First one is the concentrated light from the Fresnel lens, the second one is the direct sunlight incident onto the CPC and the third one is the direct sunlight reflected from the segmented mirrors onto the CPC. Hence the light transported through this system is adequate for illumination purposes inside the room. The manufacturing of ideal CPCs through the moulding process is both expensive and complex, and it necessitates extreme precision. Therefore, a cost-effective and efficient segmented CPC is designed and developed using a highly reflecting mirror-polished aluminum sheet which works well compared to the ideal CPC. To transport concentrated sunlight inside the room a highly reflecting horizontal light pipe is designed and developed. The collimated light at the output is challenging therefore, we have coupled inverted CPC at the exit of segmented CPC in the system. Further, to guide sunlight deep into the rooms we have coupled the entire system with a rectangular light pipe. An efficient diffuser is coupled at the end of the rectangular light pipe to illuminate the room uniformly. Various optical parameters such as illuminance, color rendering index (CRI), and correlated color temperature (CCT) values are analyzed from the result obtained which shows that the system can efficiently transport sunlight deep inside the room throughout the day. Therefore, the proposed system is very much helpful for the sustainable development of a country.

Overview of finish machining methods for the internal surfaces of rectangular pipe parts

The article deals with the proble of finish machining the internal surfaces of straight and curved pipe parts of rectangular cross-section. There is carried out analysis of technological capabilities of special finish machining technologies of internal surfaces in the Russian Federation. General information, disadvantages and advantages of these methods are presented. The selection criterion is the uniformity of machining on straight and curved parts of the pipe part. There are proved the main advantages of choosing an abrasive flow machining method as a fairly inexpensive method of finish machining. A scheme for finish machining the internal surfaces of rectangular parts is proposed. The composition of the working medium has been chosen, which allows for uniform machining, including in the corners of a rectangular cross-section.

Automated calculation of rectangular road cul-verts in the UKRRVS 22 program

Problem. The use of road culverts is currently an effective and relatively cheap means of passing surface water under the body of the road embankment. The number of road pipes on highways in areas with different topography is approximately 1.4 pipes per 1 km of the route. Road pipes, depending on the cross section, can be round, rectangular, oval, elliptical, arched, polycentric. The following are mainly used on roads: round pipes - 87%, rectangular - 9%, the rest - 4%. Automated design systems are used to calculate the characteristics of water-permeable road pipes, for example, the GRIS_T program is used to calculate the flow capacity of small artificial structures. Also, a program for the calculation of culvert road structures of the UKRRVS according to Ukrainian standards is being developed. The program includes the calculation of storm runoff according to the formula of MA-DY/SoyuzDorProekt and melt runoff; calculation of perforated road reinforced concrete round culverts for operation in non-pressurized mode. The article describes the automation of the calculation of road rectangular culverts. Goal. It is proposed to automate the calculation of road reinforced concrete rectangular culverts. Methodology. The current methods for calculating the throughput of reinforced concrete road culverts have been used. Programming was carried out in the C# language using object-oriented programming. Results. Attention is focused on rectangular pipes. Approaches to the design of rectangular road pipes in the world and Ukraine are considered. Computer-aided design systems for road pipes were analyzed. At the moment, the production uses the program for the automated calculation of culverts GRIS of the company CRE-DO DIALOGUE. The UKRRVS program is at the development stage. A modern method for calculating road reinforced concrete rectangular culverts was considered. The issue of the methodology and algorithmization of this calculation, coding and interface support has been resolved. Practical value. An algorithm for calculating road reinforced concrete rectangular culverts was developed. The article shows a part of the calculation automation code as an example. Originality. An interface for automating the calculation of road reinforced concrete rectangular culverts was developed. The UKRRVS program has been modernized. Conclusions are drawn.

Development of MEMS Airflow Volumetric Flow Sensing System with Single Piezoelectric Micromachined Ultrasonic Transducer (PMUT) Array

Compared to conventional ultrasonic flowmeters using multiple transducers, this paper reports, for the first time, an airflow volumetric flowmeter using a signal PMUT array to measure the flow rate in a rectangular pipe. The PMUT around 200 kHz is selected to fit the system requirements. All PMUT elements on this single array are then electrically grouped into transmitter and receiver. In order to minimize the crosstalk signal between transmitter and receiver, a phase shift signal is applied at the transmitter to reduce the amplitude of the crosstalk signal by 87.8%, hence, the resultant high sensing resolution. Based on the analog signal extracted from the single PMUT array, a complete flow sensing system is built by using the cross-correlation method and cosine interpolation, whereby the change in flow rate is reflected by the time of flight difference (dTof) recorded at the receiver. Meanwhile, the acoustic path self-calibration is realized by using multiple echoes. Compared with the previously reported MEMS flowmeters with dual or multiple PMUT devices, this paper proposes a single PMUT array flow sensing system, which is able to measure the flow rate changes up to 4 m3/h. With the implementation of a single device, the problem of ultrasound device/reflector misalignment during system setup is completely eradicated.

Determining features of the stressed state of a passenger car frame with an energy-absorbing material in the girder beam

The object of this study is the processes related to the emergence, perception, and redistribution of loads in the improved structure of a passenger car frame. The scientific and applied task tackled in this paper is to ensure the strength of the supporting structure of a passenger car under operating loads. In this regard, it is proposed to improve the frame of a passenger car by constructing a girder beam from two rectangular pipes filled with material with energy-absorbing properties. The regularities of the frame load have been determined by taking into consideration the proposed solutions. It was found that the maximum equivalent stresses in the frame, taking its improvement into account, are 11.2 % lower than in the structure without filler, and 11.7 % lower than in the typical design. The results reported here are explained by the fact that the use of rectangular pipes filled with energy-absorbing material contributes to an increase in the moment of resistance of the frame, and, accordingly, reduces stresses. In addition, the study has determined the natural oscillation frequencies of the frame. The results of the calculation of the strength of the weld in the zone of interaction of the girder beam with the pivot beams are given. A feature of the results obtained is that the improvement in the strength of the frame is achieved not by strengthening its components but reducing the load. The scope of practical application of the reported results concerns railroad transportation, as well as other sectors of mechanical engineering. The conditions for the practical use of these findings are the introduction of closed profiles in the structure of vehicles at the stage of their design and modernization. This study could help reduce the cost of maintaining passenger cars and improve the efficiency of their operation. In addition, the research might prove useful for designing modern railroad car structures

Formulation optimization and performance analysis of the thixotropic slurry for large-section rectangular pipe jacking in anhydrous sand

When large-section rectangular pipe jacking is performed in anhydrous sand strata, due to the special geological condition and construction specification, there are specific requirements for the performance of thixotropic slurry. In this study, an optimized traditional slurry formula and a nano-modified slurry formula (with 2% nano-SiO2 added) suitable for large-section rectangular pipe jacking in anhydrous sand formations were proposed by conducting an L25 (35) orthogonal test and a two-factor test, respectively. Five indicators were used to select the optimal slurry component proportion and nano-additive and additive concentration, including plastic viscosity (PV), filter loss (FL), water dissociation ratio (WDR), thixotropic value (TV) and yield point (YP). The influence of the component content on the slurry properties was analysed. To preliminarily verify the drag-reducing effect of the slurries prepared according to the formulas, an interface friction test was designed. The interface friction test results show that the optimized traditional slurry can reduce the pipe-soil friction coefficient to 64.7%, whereas the nano-modified slurry is 54.9%. Through scanning electron microscopy (SEM) observations, the micro mechanisms of the slurries were investigated. Furthermore, the formulas were applied in a practical pipe jacking project, and the jacking load and soil settlement were well controlled throughout the application period.

ДЕФЕКТИ МОНОЛІТНИХ ТРАНСПОРТНИХ СПОРУД І МОЖЛИВІ ШЛЯХИ ЇХ УСУНЕННЯ

Introduction. Defects that occur during the operation of monolithic transport structures, in particular overpasses, rectangular pipes and cattle drives, are considered. A comprehensive approach to the selection of constructive solutions, materials and technologies is proposed for their prevention and improvement of some provisions of the current norms for the design of such structures. Problem Statement. In the constructions of span structures of monolithic rectangular pipes, overpasses and cattle runs, during their operation under load, transverse cracks of the span structure appear, as well as shrinkage cracks, which can harm their normal operation. Purpose. The purpose of the work is the need to draw the attention of balance-keepers of structures, work customers and project organizations to the importance of ensuring proper indicators of the operational condition of transport structures at all stages of the life cycle, from project development and construction to the performance of regular work on their operational maintenance. Materials and methods. Research methods consist in identifying the influence of structural defects of monolithic transport structures on durability and safe operation. Analytical materials were used, in particular, based on the results of supervision of monolithic transport structures during the implementation of scientific support for their construction or reconstruction, as well as based on the results of survey and diagnostic work during the updating and filling of the analytical expert bridge management system (AESUM) at the facilities Poltava region. Results. The paper analyzes and provides recommendations for preventing cracking and eliminating defects in the constructions of monolithic transport structures. Conclusions. Monolithic transport facilities require complex solutions for the design of span structures and coverings, ensuring the proper organization of water drainage and compliance with the requirements of current regulatory documents and technological regulations during construction and operational works. When performing calculations of monolithic span structures of transport facilities, stricter requirements should be put forward regarding crack resistance indicators when calculating the formation and opening of cracks. It is also necessary to pay more attention to the technology of installing a cement-concrete coating. In order to reliably establish the bearing capacity of monolithic span structures, it is proposed to investigate dynamic effects during the inspection of structures and take into account the actual forces from moving loads in the presence of irregularities formed on the carriageway.

The Characteristics and Mechanisms of High-Intensity Sound in a High-Speed Multistage Compressor

An experiment with a multistage high-speed compressor is conducted to investigate the high noise with abnormal blade vibration. Different points are selected to monitor the noise in the compressor and the amplitude of blade vibration. The evolution rhythm of sound frequency and sound pressure level against speed is captured. The relation between the vibration and the noise is obtained. A research method based on an acoustic analogy is developed to investigate the characteristics and mechanisms of high-intensity sound in a rectangular cavity pipeline. The calculated distribution of the first four-order acoustic mode inside the rectangular cavity pipe is consistent with the results in the literature, and the maximum calculation error of the acoustic mode frequency value is 2.7%, which certifies the effectiveness of the method. A simplified compressor model is established to study the vortex system and the sound field characteristics of this method when high-intensity sound occurs. The results present the motion law of shedding vortices with high-intensity sound, and the calculation error of the frequency corresponding to the high-intensity sound is 3.6%. The “frequency-locked phase-locked” characteristics (i.e., character frequency) keep constant at a range of velocities, showing similarity with the phenomenon obtained in experiment above, and beta mode forms of Parker are captured. The study in the present paper makes a contribution for the cognition of mechanisms with high-intensity sound in aeroengine compressors.

Type and Size Filler Grain Selection During Abrasive Flow Machining of Non-Ferrous Alloys Rectangular Parts

Abrasive flow machining is one of the promising technologies for finishing rectangular channels, which are characterized by a constant increase in accuracy and reduction of surface roughness. During modeling of the contact interaction of grains in the corners of rectangular part cross-section in the intended abrasive flow machining, the key features of the size and filler grain selection were fixed. In the proposed spherical grain model, the cutting edge is represented by an arc of a circle that fits into the angle of the cross-section of the part. It is confirmed that if the grain size exceeds the value of the inner radius of the rounded corner of the part, an untreated zone appears, with the area calculated using the CAD system on a straight, blunt and sharp angle. It is proved that the abrasive flow machining with a filler grain size not exceeding the value of the doubled radius of the inner rounding of the rectangular cross section is carried out. The physical properties, the shape of the cutting edges and the applicability of fillers, electrolytically produced corundum, silicon carbide and synthetic diamond were analyzed. The shape of a diamond grain, in comparison with the fillers mentioned above, shows a more rounded shape of the crystal faces, which causes greater microhardness and abrasive ability. The revealed features confirm the exclusion of a possible phenomenon, caricature in the process of post-processing. It is recommended to use abrasive grains of a certain grain size for uniform pretreatment of a rough surface, followed by polishing with an ointment-like diamond paste of channels of small transverse rectangular cross-section. Using as a filler a salve-like paste containing diamond grains allows to reduce medium viscosity and machining corners of rectangular section. Abrasive flow machining with medium viscosity with synthetic heat-resistant rubber as the base and a salve-like paste containing diamond grains is used for finishing machining of non-ferrous parts. The use of working media with diamond pastes will allow the internal channels of blanks made of various non-ferrous alloys to be treated with an abrasive flow. For the minimum cross sections of rectangular pipe blanks presented in this article, it is proposed to use the working medium of the following weight composition: synthetic heat-resistant rubber - 40 %, salve-like diamond paste ASN 60/40 PTO - 60 %. A number of general recommendations are proposed for further research.

Method for calculating the forces required when bending pipes of small cross-section with a rectangular profile

Curved pipes of small cross-section rectangular profile (3,6x1,8 – 11x5,5 mm) are widely used in antenna-feeder devices of spacecraft. They are required to ensure dimensional accuracy, in the bending zone no more than ±0,05 mm, for this a choice of methods of technological modes is necessary. The object of the study is a small-section pipe billet made of copper M4, which must be bent to obtain a bending angle of 90°. The purpose of the study is to develop calculation methods necessary for the implementation of the technological process of bending small-section pipes, with justification of bending efforts. The paper analyzes the methods of bending rectangular pipes. The most rational method was chosen, bending using a rigid mandrel. Based on the selected bending method, a calculation model was compiled. The methodology and calculation algorithm have been developed and the analysis of the calculation results has been carried out. As a result of theoretical studies, with the help of calculations, the degree relationship of the effort of bending from the bending radius was revealed, the bending forces from the bending radius – the larger the bending radius, the less effort is required for bending. The calculation can be used to determine the size of the bending equipment and the bending force of the pipe of small cross-section, allows you to choose the most optimal mode of the technological process.

Effect of Nanofluid Flow in a Rectangular Heat Exchanger on the Performance of a Photovoltaic Panel

Abstract The efficiency of solar panels decreases gradually with the increase of solar cell temperature. To solve the problem, various researches have been carried out. This article studies the effect of using a cooling system on the useful energy and the overall efficiency of a photovoltaic (PV) panel. First, a numerical study has been carried out to reduce the temperature of photovoltaic panels using cooling fluids. To achieve our goal, a modeling of the heat flows between the panel components and the cooling fluid was performed, and then a matlab simulation to optimize the efficiency of the PV panel was run. A heat exchanger consisting of rectangular pipes was chosen to ensure a maximum heat exchange surface with the fluid. The choice of operating conditions and geometrical parameters was made according to the cell temperature, which must be minimal. The metrological conditions are collected from the metro central corresponding to the region of Gabes located in southern Tunisia. To further enhance the performance of solar collectors, different cooling fluids were tested including nanofluids. After testing the thermal behavior of different fluids, MgO was chosen as the best operating nanofluid. Using this nanofluid, the overall power increased by 400 W m−2 compared to that obtained with water. In addition, the electrical energy of the panels increased by 12.17% compared to water.

Study on excavation stability of shallow rectangular shield pipe jacking tunnel

Study on excavation stability of shallow rectangular shield pipe jacking tunnel

Analysis of climbing in circular and rectangular pipes with a reconfigurable sprawling robot

This paper presents an analytical description and experimental results for a reconfigurable field robot that can climb inside circular and rectangular pipes. The robot is fitted with two mechanisms that allow it to change its width and height and shift its center of mass (COM) to adapt itself to the size of the pipe. We start by describing the kinematic model of the robot as a function of its sprawl and four bar extension mechanism (FBEM). Next, we develop a force analysis based on the robot's geometry, its configuration, the position of its center of mass (COM), the diameter of the pipe, and the coefficient of friction (COF). We then develop strategies for driving, climbing and transitioning between the two modes. Although a high COF increases the robot's grip, it reduces its ability to reconfigure its shape, which it needs to transition between its climbing/driving modes. Based on this analysis, we designed a control algorithm comprised of actuation sequences to automatically drive the robot inside pipes, including the transition phases. The results show that the robot successfully executed its climbing tasks (see video).

Analytical Solution on Ground Deformation Caused by Parallel Construction of Rectangular Pipe Jacking

Pipe jacking has been widely used in urban underground engineering construction in recent years. Prediction of ground deformation caused by pipe jacking is particularly important for the safety of construction. With regard to the densely arranged pipes used in the pipe roof structure method, an analytical model of stratum disturbance caused by jacking of parallel rectangular pipes is proposed on the basis of Mindlin’s displacement solution and the stochastic medium theory. The influencing factors such as soil loss, additional thrust on the excavation face, friction between pipe jacking machine and soil, friction between subsequent pipes and soil, and the grouting pressure were comprehensively considered. Then, a 3D numerical simulation and a case study were conducted. The results showed consistent agreement with the analytical solution, and the proposed method can take into account the asymmetry of surface settlement curve induced by construction. A discussion of the ground deformation law shows that the proposed approach can reasonably predict the ground deformation and provide a reference for relevant pipe jacking construction.

Investigation of the impact of pipe geometric form on earth-to-air heat exchanger performance using Complex Finite Fourier Transform analysis. Part I: Operation in cooling mode

This paper deals with the impact of the geometric form of pipe section upon the performance of earth-to-air heat exchangers operating in cooling mode. For this purpose, three different configurations, namely circular, rectangular and elliptical were selected. Based on the heat balance analysis, a transient two-dimensional model was developed for the disturbed soil around the buried pipe. The discretization of the partial differential equation by applying the Finite Control-Volume Method yields a new generalized heat equation valid for all kinds of cylinders. Then, the resulting set of ordinary differential time-equations was linearized by using the technique of Complex Finite Fourier Transform. After successfully validating the model against available data in the literature, a thorough sensitivity analysis was carried out for assessing the impact of geometric and operating parameters including pipe length and cross-section and air speed. Further, the effect of pipe flatness relating to the rectangular and elliptical configurations was also considered through the geometric aspect ratio.The results show that the rectangular and elliptical buried pipes are more effective because they possess large exchange surfaces compared to the circular (conventional) one. For instance, at a pipe cross-section of 0.07 m2 and a geometric aspect of 9, the exchange surface between the flowing air and pipe wall in the rectangular and elliptical exchangers are larger of 88.3% and 93.6% than that of the conventional system, respectively. Moreover, at a geometric aspect of 4 and a pipe length of 60 m, the outlet temperatures supplied by the rectangular and elliptical systems are of 1.5 and 1.3 °C less than that obtained with the conventional one. Regarding the influence of pipe dimensions, it is shown that the effect of pipe length is dominant compared to that of pipe section and the performance of the system is proportional to the pipe length. Likewise, the EAHE performance increases with the increasing of the pipe geometric aspect, but a value of 4 is found to be a good compromise. Though, the performance of EAHE is found to drop dramatically at high speeds of air.