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Статті в журналах з теми "Uneven heat load"
1
Antipov, YU A., P. R. Val'yekho Malbdonado, P. P. Oshchepkov, I. K. Shatalov, and I. I. Shatalova. "Efficiency of a cogeneration plant based on a diesel engine under uneven electrical load conditions." Traktory i sel'hozmashiny 1, no. 5 (2020): 13–17. http://dx.doi.org/10.31992/0321-4443-2020-5-13-17.
Повний текст джерелаАнотація:
A feature of electrical energy is that it must be produced at a given moment as much as the con-sumer needs. However, the graphs of energy consumption are very uneven over the time of day. In order to cover peak loads, the highly mobile equipment, which is often less economical, is used. This equipment is operated at partial power modes, where its efficiency is markedly reduced. One of the real ways to get out of this situation can be the use of heat pumps (HP) in circuits with cogeneration units (CU) based on heat engines. In this case, it becomes possible to use the heat engine in an economical mode throughout the day, and direct excess electricity at night to the heat pump drive. The paper considers two options for the operation of a cogeneration plant based on a diesel engine in power supply schemes for an individual consumer under conditions of an uneven electrical load schedule. Wartsila 12V32 is taken as an example of a CU. Such plants are operated in different regions of the Russian Federation. The main data of the CU in the design mode are given. Diesel generator: electric power - 6000 kW, hourly fuel consumption - 1080 kg / h, thermal power - 5240 kW, exhaust gas temperature - 485 ° C, effective efficiency - 0.46, fuel heat utilization factor 0.89. In the first version, the CU operates in a standard mode. This ensures the generation of electrical power in accordance with the schedule. In the second version, the CU is used in conjunction with the HP to obtain additional thermal power. Calculations have shown that by including a heat pump in a cogeneration unit operating in an uneven electrical load schedule mode, it is possible to ensure that the diesel engine operates at maximum efficiency during the whole day and to increase the fuel heat utilization rate by 17-20%.
2
Li, Ming Hai, and Ding Ding Dong. "Finite Element Analysis of the Cylinder Liner of a 280 Diesel Engine." Advanced Materials Research 616-618 (December 2012): 1745–50. http://dx.doi.org/10.4028/www.scientific.net/amr.616-618.1745.
Повний текст джерелаАнотація:
The Cylinder liner is one of the key components of diesel engine. Combustion chamber set is constituted by Piston, Cylinder head, Cylinder liner and other parts. Its structure and working environment is complex. Received the gas pressure, friction force from high-speed reciprocating motion of the piston and lateral force of the piston, it results in mechanical stress and mechanical deformation. High temperature combustion and high pressure gas make the piston temperature distribution uneven, which results in piston thermal stress and thermal deformation. Therefore, the element analysis of Cylinder liner in the heat load and mechanical load is significant, the finite element analysis shows the deformation and the stress distribution of the Cylinder liner. It is meaningful for improving Cylinder liner design and reliability.
3
Yakovlev, P. V., V. A. Lebedev, and V. M. Piskunov. "Thermal conditions of load-bearing elements of radioactive waste storage facilities." E3S Web of Conferences 220 (2020): 01079. http://dx.doi.org/10.1051/e3sconf/202022001079.
Повний текст джерелаАнотація:
Facilities for storing radioactive waste with residual heat differ from other facilities in high safety standards in all operating conditions. A feature of these structures is the presence of biological protection in the form of walls and ceilings made of reinforced concrete with a large thickness. The combination of heat dissipation and the large thickness of walls and floors create conditions for the appearance of significant thermal stresses. This feature should be taken into account in the strength calculations of these buildings, taking into account the summation of seismic effects, gravitational forces and thermal stresses caused by uneven temperature fields in concrete. The paper presents the results of calculations of the combined effects of thermal stresses and earthquakes on a building. The data obtained made it possible to determine the features of the deformation of concrete structures with a combination of loads.
4
Zhang, Jie, and Tieshan Zhang. "Research on the Influence of Piston Constraint on the Temperature Field of Multi-disc Clutch." MATEC Web of Conferences 256 (2019): 02006. http://dx.doi.org/10.1051/matecconf/201925602006.
Повний текст джерелаАнотація:
The two-dimensional finite element model of multi-disc clutch friction pair was established by Abaqus simulation software, and the contact pressure of the friction surface under different piston constraints was calculated and analyzed. Considering contact pressure as the main heat-generating factor, the two-dimensional heat conduction process was numerically discretized by the implicit difference method. Then the temperature model of the multi-disc clutch friction pair was programmed in Matlab. The bench test verified the correctness of the temperature model. It is found that the temperature field between components is different and shows uneven distribution under the actual constraint. The local temperature of the component near the concentrated load is the highest, in which the radial temperature difference is the largest. The arrangement in which the piston pressure is concentrated in middle diameter produces the lowest temperature and the smallest radial temperature difference, which can effectively avoid thermal deformation of the component due to uneven temperature distribution.
5
Mellalou, Abderrahman, Walid Riad, Salma Kaotar Hnawi, Abdelaziz Tchenka, Abdelaziz Bacaoui, and Abdelkader Outzourhit. "Experimental and CFD Investigation of a Modified Uneven-Span Greenhouse Solar Dryer in No-Load Conditions under Natural Convection Mode." International Journal of Photoenergy 2021 (July 29, 2021): 1–12. http://dx.doi.org/10.1155/2021/9918166.
Повний текст джерелаАнотація:
An uneven-span modified greenhouse dryer was constructed and tested in no-load conditions under natural convection mode under the weather conditions of Marrakech, Morocco, for two distinct days. Moreover, a CFD evaluation of the uneven-span greenhouse dryer was performed as tool to visualize the air temperature distribution inside the dryer. For validating the CFD model, the temperature variations along the hours of the day were compared to the experimental results. A good agreement is obtained between the computed and measured inside air temperature with a difference not exceeding 8.46°C, with a correlation coefficient ( r ) and root mean square percentage deviations ( e ) 0.94 and 8.17, respectively. Furthermore, the maximum inside air temperature was measured to be 56°C and 52°C while the minimum inside relative humidity was measured to be 17% and 12%, for day-1 and day-2, respectively. The benefice of using asphalt as a floor covering material was revealed as an efficient way to heat the inside air at low solar radiations. The performances of the dryer were evaluated by the percentage of net heat gain variation as a way to validate the effectiveness of the dryer. This latter is found to be equal to 46% and 48% for the two days, respectively.
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Borodulin, Boris B. "Algorithm for automatic compensation of thermal deformations of thermally loaded load-bearing structures." Vestnik of Samara State Technical University. Technical Sciences Series 29, no. 4 (December 15, 2021): 6–19. http://dx.doi.org/10.14498/tech.2021.4.1.
Повний текст джерелаАнотація:
The paper considers a possible algorithm for the automatic control system of the thermal modes of load-bearing structures of the information-measuring system of autonomous objects. Thermo-deformation component of information-measuring error, which is the cause of distortion of operating and service information of an autonomous object, is reduced due to compensation of thermogradient by automatic control system of operation modes of distributed controlled heat sources. The system provides a significant reduction in the level of thermal deformation error of measurements, the cause of which is the deformation of supporting structures due to unstable and uneven heat release of information-measuring instruments placed on the structure. To compensate for thermal deformations, the system includes controlled heat sources that compensate for the thermal gradients of the supporting structure arising under the influence of the information-measuring system instruments and external thermal radiation on the structure. An effective rational control algorithm, providing compensation of the thermal gradient of the load-bearing structure to an acceptable level, is proposed. The control algorithm and the system structure are designed to be implemented by special software of the onboard computer.
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Luo, Zixue, Zixuan Feng, Bo Wu, and Qiang Cheng. "Decoupling Investigation of Furnace Side and Evaporation System in a Pulverized-Coal Oxy-Fuel Combustion Boiler." Energies 15, no. 7 (March 23, 2022): 2354. http://dx.doi.org/10.3390/en15072354.
Повний текст джерелаАнотація:
A distributed parameter model was developed for an evaporation system in a 35 MW natural circulation pulverized-coal oxy-fuel combustion boiler, which was based on a computational fluid dynamic simulation and in situ operation monitoring. A mathematical model was used to consider the uneven distribution of working fluid properties and the heat load in a furnace to predict the heat flux of a water wall and the wall surface temperature corresponding to various working conditions. The results showed that the average heat flux near the burner area in the air-firing condition, the oxy-fuel combustion with dry flue gas recycling (FGR) condition, and the oxy-fuel combustion with wet flue-gas recycle condition were 168.18, 154.65, and 170.68 kW/m2 at a load of 80%. The temperature and the heat flux distributions in the air-firing and the oxy-fuel combustion with wet FGR were similar, but both were higher than those in the oxygen-enriched combustion conditions with the dry FGR under the same load. This study demonstrated that the average metal surface temperature in the front wall during the oxy-fuel combustion condition was 3.23 °C lower than that under the air-firing condition. The heat release rate from the furnace and the vaporization system should be coordinated at a low and middle load level. The superheating surfaces should be adjusted to match the rising temperature of the flue gas while shifting the operation from air to oxy-fuel combustion, where the distributed parameter analytical approach could then be applied to reveal the tendencies for these various combustion conditions. The research provided a type of guidance for the design and operation of the oxy-fuel combustion boiler.
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Wei, De Jian, and Xin Gui Zhang. "The Heat Exchange and Stress Distributing of Expansive Soil in Site." Applied Mechanics and Materials 130-134 (October 2011): 1650–53. http://dx.doi.org/10.4028/www.scientific.net/amm.130-134.1650.
Повний текст джерелаАнотація:
Expansive soil is called as “problem soil”, which has a characteristic of swelling by absorbing water and shrinking by losing water. So buildings and sub-grade which are built on expansive soil, are easier to damage for lager deformation. Due to the large-scale urban construction, ground surface was covered in a wide range. For example, in tropics and subtropics areas, the water transfer in the expansive soil is influenced by the gradient of temperature, which is different between the central area under the road surface and road-side bare area. Because of the hysteresis of water transfer, the water content distributing is not uniform, which lead to the different swell-shrink performance in different zone, herewith will change some parameters of the expansive soil and finally affect its stress field and the displacement field. Take the road as the example: The road is a strip belt-shaped coverage. Both in dry and wet season, the thermodynamic field and water-flowing field is uneven between the central area under the road surface and road-side bare area, so the displacement field and the stress field on the cross-section under the road is uneven. Under the load of vehicle, the non-uniformity stress distributing in the soil is further aggravated, and the same to the displacement in the underlying sub-grade, which is a significant factor in aggravating the dehiscence of road surface. Comparing to general soil, expansive soil has a completely different distribution of temperate field and water-flowing condition because of its swell-shrink characteristic. By studying on the relationship between the thermodynamic field and the stress-strain in the expansive soil, it can find out how the climate affect the engineering expansive soil, and provide the theory basis for improving expansive soil.
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Kalabin, D. A., A. Yu Lipovka, and Yu L. Lipovka. "Computer simulation and full-scale measurements of the load flow in a functioning heating network." Proceedings of Irkutsk State Technical University 25, no. 1 (March 20, 2021): 44–56. http://dx.doi.org/10.21285/1814-3520-2021-1-44-56.
Повний текст джерелаАнотація:
The article aims to identify patterns in the distribution of heating energy to consumers with a varying availability of regulation equipment under real conditions of a central heating network, as well as to compare the results of computer simulation with full-scale measurements. For computer simulation, well-known mathematical methods for calculating the load flow in hydraulic circuits were used. Experimental studies of the operation modes of heat supply systems were carried out using the data of the control and monitoring systems of thermal power plants using the Siemens Simatic PCS7 software, a Portaflow 300 ultrasonic flow meter, stationary electromagnetic flow transducers, verified and certified manometers and thermometers. The graphs of the actual hydrodynamic modes of the heating network under study were obtained at outdoor air temperatures from +8 to -37°C, as well as under abnormal conditions (temperature drop in the supply pipeline and pressure drop at the heating network input). It was proposed to use jointly the simulation by means of the JA_Net software and full-scale measurements of the thermohydraulic operating modes of a centralised heat supply system, whose consumers have a various degree of regulation equipment. It was shown that the proposed complex method of qualitative and quantitative assessment of the efficiency of district heating networks makes it possible to identify the features of control of their hydraulic modes when connecting new consumers with a varying degree of automation. According to the obtained characteristics of changes in the flow rate of the coolant in the consumers’ internal systems depending on the pressure drop at the tie-in point, the lack of response to emergency situations on part of the consumers whose heat supply systems are equipped with the means of qualitative and quantitative regulation of the heat load, is associated with the process of automatic adjustment of the degree of opening of flow controllers and control valves at individual points. In future work, we will develop guidelines for levelling the imbalance of the heating network under the conditions of uneven provision of facilities with automation equipment when implementing projects for the complex modernisation of heat consumers or connecting new facilities to existing heat supply networks.
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Demchenko, Vladimir, Alina Konyk, and Vladimir Falko. "Mobile Thermal Energy Storage." NTU "KhPI" Bulletin: Power and heat engineering processes and equipment, no. 3 (December 30, 2021): 44–50. http://dx.doi.org/10.20998/2078-774x.2021.03.06.
Повний текст джерелаАнотація:
The article is devoted to topical issues related to the storage, accumulation and transportation of heat by stationary and mobile heat storage. Analysis of the current state of the district heating system indicates significant heat losses at all stages of providing the consumer with heat. The use of heat storage in heat supply systems leads to balancing the heat supply system, namely, the peak load is reduced; heat production schedules are optimized by accumulating excess energy and using it during emergency outages; heat losses caused by uneven operation of thermal equipment during heat generation are reduced; the need for primary energy and fuel consumption is reduced, as well as the amount of harmful emissions into the environment. The main focus is on mobile thermal batteries (M-TES). The use of M-TES makes it possible to build a completely new discrete heat supply system without the traditional pipeline transport of the heat carrier. The defining parameters affecting the efficiency of the M-TES are the reliability and convenience of the design, the efficiency and volume of the “working fluid”, the operating temperature of the MTA recharging and the distance of transportation from the heat source to the consumer. The article contains examples of the implementation of mobile heat accumulators in the world and in Ukraine, their technical and technological characteristics, scope and degree of efficiency. The technical indicators of the implemented project for the creation of a mobile heat accumulator located in a 20-foot container and intended for transportation by any available means of transport are given.
Дисертації з теми "Uneven heat load"
1
Radchenko, Mykola, Eugeniy Trushliakov, Andrii Radchenko, М. І. Радченко, Є. І. Трушляков, and А. М. Радченко. "Enhancing heat efficiency of air coolers of air conditioning systems by injector refrigerant circulation." Thesis, 2020. http://eir.nuos.edu.ua/xmlui/handle/123456789/4340.
Повний текст джерелаАнотація:
Radchenko, M. Enhancing heat efficiency of air coolers of air conditioning systems by injector refrigerant circulation = Підвищення теплової ефективності повітроохолоджувачів систем кондиціонування інжектором / M. Radchenko, E. Trushliakov, A. Radchenko // Матеріали XI міжнар. наук.-техн. конф. "Інновації в суднобудуванні та океанотехніці". В 2 т. – Миколаїв : НУК, 2020. – Т. 1. – С. 581–491.Анотація: Один з найпривабливіших резервів підвищення ефективності систем кондиціонування та їх застосування в різних областях полягає в ефективній роботі повітряних охолоджувачів (випарників холодоагенту). Концепція доопрацювання ефективної роботи випарників холодоагенту з неповним випаровуванням холодоагенту за рахунок рециркуляції рідкого холодоагенту інжектором (реактивним насосом) знайшла новий імпульс для подальших застосувань у зовнішніх повітряних переробних установках, щоб відповідати різним нагріванням зовнішнього тепла відповідно до фактичних кліматичних умов Умови в приміщенні відповідали різним тепловим навантаженням у приміщеннях в системах кондиціювання без змінного холодильного потоку. Запропонована концепція підвищення теплової ефективності теплообмінників з киплячими холодоагентами всередині каналів розроблена для вирішення проблеми нерівномірного розподілу холодоагенту у впускних колекторах (головках) для мікроканальних теплообмінників або між котушками холодоагенту та нерівними зовнішнім боковим нагріванням повітря на змійовиках холодоагенту шляхом переповнення їх за допомогою рециркуляції рідкого холодоагенту, що забезпечує виключення кінцевої стадії висихання випаровування холодоагенту з низькою інтенсивністю передачі тепла. Таким чином, за рахунок виключення внутрішньої проблеми нерівномірного розподілу холодоагенту та низької інтенсивності передачі тепла випаровуванням холодоагенту в каналах загальна проблема підвищення ефективності теплообмінників киплячим холодоагентом всередині каналів перетворюється на зовнішню проблему передачі тепла на повітряній стороні.
Abstract: One of the most attractive reserves of enhancing the efficiency of air conditioning (AC) systems and their application in various fields consists in efficient operation of air coolers (refrigerant evaporators). A retrofit concept of efficient operation of refrigerant evaporators with incomplete refrigerant evaporation due to liquid refrigerant recirculation by injector (jet pump) has found a new impulse for further applications in outdoor air processing units (OAPU) to match varying outdoor heat loads according to actual climatic conditions and for indoor air coils to match varying indoor heat loads in ductless Variable Refrigerant Flow (VRF) AC systems. A proposed concept of enhancing heat efficiency of heat exchangers with boiling refrigerants inside channels is intended to solve the problem of uneven refrigerant distribution in inlet manifolds (headers) for microchannel heat exchangers or between refrigerant coils and of uneven outside air heat loads on refrigerant coils by over filling them through liquid refrigerant injector recirculation that provides excluding the final dry-out stage of refrigerant evaporation with low intensity of heat transfer. Thus, due to excluding the internal problem of refrigerant uneven distribution and low intensity of heat transfer of refrigerant evaporation in channels the general problem of enhancing the efficiency of heat exchangers with boiling refrigerants inside channels is transformed into the external problem of heat transfer on air side.
Тези доповідей конференцій з теми "Uneven heat load"
1
Wang, Ji, Zhiping Chen, and Chulin Yu. "Effect of Post-Weld Heat Treatment on the Plastic Buckling of Welded Cylindrical Shells." In ASME 2012 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/pvp2012-78634.
Повний текст джерелаАнотація:
Storage tanks, silos and other welded cylindrical shell structures are usually constructed of rolled panels which are joined by patterned circumferential and longitudinal welds. Cold-formed residual stresses are produced during the cold bending process of steel panels, and obvious deformations and uneven distributed welding residual stresses are also produced because of the welding process. Studies have shown that residual stresses could weaken the critical buckling load of welded cylindrical shells under axial compression. Stress-relief post-weld heat treatment (PWHT) is a process that heats the workpiece gradually to 500∼650 °C, holding the temperature 0.5 hours then reducing the temperature slowly. Two cylindrical shell specimens are fabricated in this paper, and one is processed with stress-relief PWHT, while the other is not. The magnitude and distribution of residual stresses near the weld zone in each specimen are measured with an X-ray diffraction-based measurement system (named iXRD by the manufacturer), and initial imperfections and critical load of the specimens are obtained by the use of an axial buckling experiment platform. Thereafter, numerical simulations are conducted with measured geometric imperfections and residual stresses exerted into the finite element model. Finally, comparison of the critical loads of both cylindrical shell specimens is made, showing the effects of residual stresses on the plastic buckling of cylindrical shells under axial compression.
2
Shui, Linqi, Bo Huang, Kunkun Dong, and Chunyan Zhang. "Investigation of Heat Transfer and Flow Characteristics in Fractal Tree-Like Microchannel With Steam Cooling." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-63973.
Повний текст джерелаАнотація:
Using closed-loop steam to cool blades is beneficial to improve the gas turbine thermal efficiency. Although the steam-cooled blade can provide sufficient cooling for the main body of high temperature blade, the high thermal load is found in the leading and trailing edge. To alleviate the thermal loads as well as thermal stresses, it is necessary to optimize the cooling configuration of closed loop steam-cooled blades. The tree-like branching network systems have the unique high cooling efficiency and low flow resistance as well as even temperature distribution characteristics. Utilizing the efficient transportation branching network as the internal cooling configuration for the steam-cooled blades, is likely to provide useful hits of optimal solution for solving the uneven and insufficient cooling problems at the high thermal load regions. For this purpose, the heat transfer and flow friction features of coolant flow in the tree-like branching microchannel is studied experimentally and numerically. The results indicate that, influenced by the branch effects, the fractal tree-like microchannel provides a desirable low friction factor for the turbulent flow, and an expected better heat transfer performance under the conditions of a higher Re number and larger heat flux. In addition, compared the wall temperature distributions between the fractal tree-like microchannel and serpentine channels with different coolant, adopting the tree-like branching channel configuration combination with steam cooling could provide an excellent even cooling performance for the high temperature metal wall.
3
Zhang, Yanfei, Xiaohu Li, Jun Hong, Sun’an Wang, Baotong Li, Yanhui Sun, and Shuai Zheng. "Rotation Accuracy Analysis of Spindle Under Variable Preload." In ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-71264.
Повний текст джерелаАнотація:
Variable preload technology is used to achieve appropriate preload applied on spindle bearing based on machining conditions. However, the bearing temperature rise will be directly affected by bearing preload as well as bearing rotation accuracy. So, the main objective of this paper is to propose a method to determine the rotation accuracy of the spindle affected by the thermal expensive due to heat generation under variable preloads. Five degrees of freedom (5-DOF) quasi-static model of angular contact ball bearing was established to investigate the internal load distribution of the contact areas between the race way and balls. Then local contact heat generation of the bearing is calculated based on hertz contact theory. Finally, an experimental platform equipped with hydraulic system is designed and fabricated, which is preloaded by a hydraulic chamber. Studies have shown that the rotation accuracy presents drastically with the spindle rotational speed. Moreover, the influence of the bearing preload has a secondary importance. Comparative analysis about the rotation accuracy between starting running state and stable running state after a few hours under the same preload has been investigated. Results show that the accuracy of rotation spindle present no obviously difference when the uneven thermal deformation of parts occurs in the spindle system.
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Christian, Joshua M., Jeremy Sment, Clifford K. Ho, Lonnie Haden, and Kevin Albrecht. "Particle Lift Challenges and Solutions for Solid Particle Receiver Systems." In ASME 2019 13th International Conference on Energy Sustainability collocated with the ASME 2019 Heat Transfer Summer Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/es2019-3833.
Повний текст джерелаАнотація:
Abstract Particle receiver systems require durable, reliable, and cost-effective particle transport equipment. These lifts are critical pieces of equipment to transport the particles from the heat exchanger back into the receiver. There are challenges that must be overcome with any particle lift device including high temperatures (800°C), particle load and friction, and erosion from particle contact. There are several options commercially available for particle systems including a screw-type vertical elevator, bucket lift vertical elevator, and skip-hoist-style bulk vertical lifts. Two of the elevator types (screw and bucket) have been tested at the National Solar Thermal Test Facility (NSTTF) at Sandia National Laboratories (SNL) in Albuquerque, NM. The two elevators are currently in operation on the 1 MWth falling particle receiver at the Solar Tower. The screw-type elevator consists of a stationary internal screw with an outer casing that rotates about the screw. The frictional forces from the casing rotation drives the particles upward along the flights of the screw. The casing rotational velocity is variable which allows for mass flow rate control. Identified issues with the screw-type elevator include particle attrition, uneven loading at the inlet causes casing deflection, bearing deformation due to casing deformation, and motor stalling due to increased resistance on the casing. The SNL bucket elevator is rated for temperatures up to 600 °C and consists of steel buckets and a steel drive chain capable of lifting particles at a rate of 8 kg/s. Identified issues with the bucket type elevator include discrete (non-continuous) discharge of the particles and a non-adjustable flow rate. A skip hoist type elevator has been studied previously and seems like the most viable option on a large scale (50–100MWth power plant) with a non-continuous particle discharge. Different control scenarios were explored with the variable frequency drive of the screw-type elevator to use it as a particle-flow control device. The objective was to maintain the feed hopper inventory at a constant value for steady flow of particles through the receiver. The mass flow rate was controlled based on feedback from measurements of particle level (mass) inside the top hopper.
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Anderson, Walter, Ahmadreza Eshghinejad, and Mohammad Elahinia. "Material Characterization and Mid-Span Bending Capacity With Finite Element Simulated Predictions." In ASME 2011 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2011. http://dx.doi.org/10.1115/smasis2011-5097.
Повний текст джерелаАнотація:
Intelligent materials have been the subject of research for many years. Shape memory alloys (SMAs) are a type of intelligent material that has been targeted for many different uses; such as actuators, sensors and structural supports. SMAs are attractive as actuators due to their large energy density. Although a great deal of information is available on the axial load capacity and on the tip force for SMA tweezer-like devices, there is not enough information about the load capacity at mid-span, especially at the macro-level. Imposed displacement at mid-span experimental evaluation of an SMA beam in the austenitic and martensitic regimes has been studied. To this end, a specimen of near equi-atomic nitinol was heat-treated (shape set) into a ‘U’ shape and loaded into a custom test fixture such that the boundary conditions of the beam are approximated as roller-roller; and the sample was deformed at different temperatures while reaction forces were measured. The displacement is near maximum displacement of the U shape without causing a change in concavity, thus full-scale capacity is shown. Additionally, Unified Model (finite element) predictions of the experimental response are also presented, with good agreement. Due to the robust nature of the Unified Model, geometric parameter variations (wire diameter and radius of curvature) were then simulated to encompass the design envelop for such an actuator. The material properties needed as inputs to the Unified Model were obtained from constant temperature tensile tests of a specimen subjected to the same heat treatment (shape set straight). The resultant critical stresses were then extracted using the tangent method similar to the one described in ASTM F-2082. It is worth noting that the specimen was trained before the stress value extraction, but the transversely loaded specimen was not trained due to the difficulty involved (inherent uneven stress distribution). The contribution of this work is the presentation of experimental results for transverse (mid-span) loading of a nitinol wire and the simulation results allowing for design of a proper actuator with known constraints on force, displacement or temperature (2 of 3 needed). In other words, this work could be used as a type of 3D look-up table; e.g. for a desired force/displacement, the required temperatures are given. Future work includes developing a sensor-less control strategy for simultaneous force/displacement control.
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Henke, Martin, Nikolai Klempp, Martina Hohloch, Thomas Monz, and Manfred Aigner. "Validation of a T100 Micro Gas Turbine Steady-State Simulation Tool." In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-42090.
Повний текст джерелаАнотація:
Micro gas turbines (MGT) provide a highly efficient, low-pollutant way to generate power and heat on-site. MGTs have also proven to be a versatile technology platform for recent developments like utilization of fuels with low specific heating values and solar thermal electricity generation. Moreover, they are the foundation to build novel cycles like the inverted Brayton cycle or fuel cell hybrid power plants. Numerical simulations of steady operation points are beneficial in various phases of MGT cycle development. They are used to determine and analyze the future potentials of innovative cycles for example by predicting the electrical efficiency and they support the thermodynamic design process (by providing mass flow, pressure and temperature data). Numerical Simulation allows to approximate off-design performance of known cycles e.g. power output at different ambient conditions. Additionally, numerical simulation is used to support cycle optimization efforts by analyzing the sensitivity of component performance on cycle performance. Numerical models of the MGT components have to be tuned and validated based on experimental data from MGT test rigs. At DLR institute of combustion technology a MGT steady-state cycle simulation tool has been used to analyze a variety of cycles and has been revised for several years. In this paper, the validation process is discussed in detail. Comparing simulation data with measurement data from the DLR Turbec T100 test rig has led to extensions of the numeric models, on the one hand, and to modifications of the test rig on the other. Newly implemented numerical models account for the generator heat release to the inlet air and the power electronic limitations. The test rig was modified to improve the temperature measurement at positions with uneven spatial temperature distribution such as the turbine outlet. Analyzing these temperature distributions also yields a possible explanation for the apparent strong recuperator efficiency drop at high load levels, which was also observed by other T100 users before.
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Jawale, H. P., and Rahul Singh. "Analysis of Welded Joint Under Residual Stresses." In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-39484.
Повний текст джерелаАнотація:
Welded joint is most commonly used for building structures and machine components. Welding process involves heating followed by uneven cooling causing residual stress field. In conjunction with stresses due to external loads, in-service behaviour is affected due to residual stress in welded components. It induces defects, also alters crack initiation life, fatigue behaviour, breaking strength, corrosion resistance and increases the susceptibility of structure to failure by fracture. The residual stress is function of cooling rate and the size of weld. The role of residual stress associated with welding is therefore very important while designing mechanical parts. Conventional methods like heat treatment and shot-peening techniques becomes difficult to be applied for reduction of residual stress in general purpose applications. The work presented in this paper describes the measurement of residual stress using stress relieving method, based on hole-drilling technique. Subsequently, residual stresses are relived and measured using strain rosette near the weld zone. These strains value is converted in to stress value. Residual stress is quantified with respect to yield strength, making it possible to be considered for safe designing of weld components.
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Hoznedl, Michal, Antonín Živný, Aleš Macálka, Robert Kalista, Kamil Sedlák, Lukáš Bednář, and Ladislav Tajč. "The Pressure Field at the Output From a Low Pressure Exhaust Hood and Condenser Neck of the 1090 MW Steam Turbine: Experimental and Numerical Research." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-75248.
Повний текст джерелаАнотація:
The paper presents the results of measurements of flow parameters behind the last stage of a 1090 MW nominal power steam turbine in a nuclear power plant. The results were obtained by traversing a pneumatic probe at a distance of about 100 mm from the trailing edges of the LSB (Last Stage Blade). Furthermore, both side walls as well as the front wall of one flow of the LP (Low Pressure) exhaust hood were fitted with a dense net of static pressure taps at the level of the flange of the turbine. A total of 26 static pressures were measured on the wall at the output from the LP exhaust hood. Another 14 pressures were measured at the output from the condenser neck. The distribution of static pressures in both cross sections for full power and 600 and 800 MW power is shown. Another experiment was measured pressure and angle distribution using a ball pneumatic probe in the condenser neck area in a total of four holes at a distance up to 5 metres from the neck wall. The turbine condenser is two-flow design. In one direction perpendicular to the axis of the turbine cold cooling water comes, it heats partially. It then reverses and it heats to the maximum temperature again. The different temperature of cooling water in the different parts of the output cross section should influence the distribution of the output static pressure. Differences in pressures may cause problems with uneven load of the tube bundles of the condenser as well as problems with defining the influential edge output condition in CFD simulations of the flow of the cold end of the steam turbine Due to these reasons an extensive 3D CFD computation, which includes one stator blade as well as all moving blades of the last stage, a complete diffuser, the exhaust hood and the condenser neck, has been carried out. Geometry includes all reinforcing elements, pipes and heaters which could influence the flow behaviour in the exhaust hood and its pressure loss. Inlet boundary conditions were assumed for the case of both computations from the measurement of the flow field behind the penultimate stage. The outlet boundary condition was defined in the first case by an uneven value of the static pressure determined by the change of the temperature of cooling water. In the second case the boundary condition in accordance with the measurement was defined by a constant value of the static pressure along all the cross section of the output from the condenser neck. Results of both CFD computations are compared with experimental measurement by the distribution of pressures and other parameters behind the last stage.
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Magerramova, Liubov, Michael Volkov, Anton Salnikov, and Eugene Kratt. "Development of the Functional-Gradient Turbine Wheel With Cooled Blades Without Lock Connection." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-14772.
Повний текст джерелаАнотація:
Abstract Wheels of high-temperature turbines are traditionally produced in the form of detachable joints of the disk and blades made from different materials. The blades, which are under the influence of high gas temperatures, are made with internal channels by air cooling. The disk is subject to significant centrifugal loads, but lower temperatures. The locking connection of the blades to the disk is a stress concentrator, which leads to resource limitation. One of the solutions is the wheel of the turbine type blisk consisting of cast-cooled blades of heat-resistant alloys and a disk of granulated nickel alloys, interconnected by hot isostatic pressing. The disk can be made of granules of different sizes in different parts. This approach is based on the fact that during operation, the disk is also subject to uneven heating and loading along the radius. The blisk design of the wheel with cooled blades is developed on the basis of the turbine wheel with a detachable connection of the blades with the disk. The blades of the blisk are produced from casting heat-resistant nickel alloy. The disk portion is created from granulated alloy with different grain sizes along the disk radius. The system of supplying cooling air in the blades of the wheel is developed. The technology of manufacturing a disk consisting of granules of various sizes and technology of connection of a disk with cooled cast blades is developed. To determine the mechanical characteristics of the zones of connection of dissimilar materials samples were tested. The combined samples were made of a granulated alloy with different sizes of granules. The bimetallic samples were made of a casting blade alloy and a granulated disk alloy. Multi-parameter optimization of the blisk was carried out. The mass of the designed wheel was reduced by more than 40% compared to the original wheel with lock connection when the strength and service life conditions were satisfied.
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San Andrés, Luis, Wonbae Jung, and Seong-Ki Hong. "A Thermo-Hydrodynamic Model for Thermal Energy Flow Management in a (Semi) Floating Ring Bearing System for Automotive Turbochargers." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-14332.
Повний текст джерелаАнотація:
Abstract Oil-engine lubricated turbochargers (TCs) operate at high temperature and must withstand large temperature gradients that produce severe thermo-mechanical stresses in the TC mechanical components. Thus, an insight into the thermal energy flows and an effective thermal management are paramount to ensure reliable TC operation. The paper analyzes the transport of energy and heat flows in semi-floating ring bearings (SFRBs) for automotive TCs with integrated heat and fluid flow models for both (turbine and compressor sides) radial bearings and thrust bearings to produce a complete thermo-hydrodynamic analysis predictive tool. The model couples the energy transport equations and the lubrication Reynolds equations in the inner and outer films of a SFRB and the adjacent thrust films to a three-dimensional heat conduction in the floating ring and along with thermal soaking into the TC casing. Cold lubricant, supplied at a specific temperature and pressure, flows to fill the films of the radial bearings, and then the thrust bearings. The lubricated bearings, radial and axial, support shaft loads, static and dynamic, and produce drag power losses. The streams of lubricant warm up as they take away a sizable portion of the heat flow from the hot shaft plus that due to viscous shear drag. Another fraction of thermal energy flow sinks into the floating ring which presents a distinct temperature field varying along the radial, circumferential and axial directions. The computational analysis contemplates a TC operating at shaft speeds (Ω) ranging from 30 krpm to 240 krpm (4 kHz) and a SFRB supplied with engine oil at PSUP = 3.0 bar and TSUP = 120 °C. The analysis focuses on a brass-made turbine bearing as it is the one that disposes most thermal energy flow since the shaft surface is hot at Ts = 213 °C (just below the lubricant flash point temperature at 230 °C) while the casing temperature is TC = TSUP. The ring with length/diameter = 1.6 has radial bearings with four equally spaced feed holes and four axial grooves, and the ratio outer film clearance/inner film clearance equals 5.3 at room temperature. As shaft speed increases (= 100 m/s max. surface speed), the inner film temperature increases proportionally; albeit the heat flow from the shaft into the inner film decreases while the viscous drag power raises rapidly. The outer film heats to just a few degrees above TSUP since the non-spinning ring does not generate viscous shear drag. The ring heats unevenly, radially with a ∼20 °C temperature gradient from its inner to outer diameters (ID and OD), and axially with up to a ∼50 °C difference from the thrust bearing side that also produces a drag power loss. At a low shaft speed (45 krpm), heat flowing from the shaft overwhelms the drag power loss induced by shearing the inner film; whereas as shaft speed increases (240 krpm), the contribution from the drag power loss to the total energy flow disposed increases significantly, from 3% to 63%. The lubricant flows, inner plus outer, advect most of the thermal energy flow, 74% to 81%, over the range of shaft speeds, low to high. The floating ring conducts a sizeable portion of thermal energy flow, 39% to 49% of the total, though varying little with shaft speed. Similarly does the fraction of heat, 9% to 13% of the total, conducted into the TC casing. A more conductive ring material or an outer film with a longer length conduct more heat into the ring although the lubricant flows still carry most of the thermal energy flow generated by viscous drag losses and heat from the shaft. The results demonstrate the importance of designing a SFRB system with adequate clearances and proper materials to offer an adequate thermal management and avoiding too high temperatures that could varnish, even flash and burn, the engine oil. The improvements in the energy transport and heat flow modeling of a SFRB system will produce significant savings in TC performance.