The aim of this article is to provide some basis for the design and assembly of a bolted rotor with curvic couplings. It is well known that the key difference between a bolted rotor with curvic couplings and an integrated one is the contact interface. According to the characteristics of curvic couplings and spindle bolts, the model of a bolted rotor with curvic couplings of the turbine end of a heavy duty gas turbine was built. A method of accurately applying the preload force has been studied in this article. The three-dimensional finite-element contact method was used, non-linear behaviours such as friction and contact were also taken into account, and the dynamic contact between the spindle bolts and the sidewall of turbine wheels was included. The tendency of stress, which involved the rotor, curvic couplings, and the spindle bolts, was determined and the radial slippage trend of curvic teeth was also determined, by investigating the stress distribution and contact behaviour of the bolted rotor with curvic couplings during the course of preload, warm-up, speed-up, and running. It can be seen from the results that the contact stress of curvic couplings is dominant during the course of preload, and the bent stress is dominant when the rotating speed increased to 3000 r/min; the stress inequality on two sides of a tooth is caused by torque, so the stress proportion induced by torque should be restricted to an appropriate level to avoid anisotropy of the rotor.
The paper aims to investigate re-entrainment mechanisms of wall films. The computational fluid dynamics method was adopted to study the gas-liquid separation process considering the wall film model. The interaction between the droplets and gas was solved by Euler-Lagrange method, whereas the forming
Petroleum industry uses shear devices such as chokes, valves, orifices and pumps, which cause droplet coalescence and breakup making the downstream separation process very challenging. Droplet-droplet coalescence leads to formation of larger droplets, which accelerate the phase separation, whereas the breakup of larger droplets into smaller ones delays the separation process. Computational Fluid Dynamic (CFD) simulations are conducted by ANSYS-Fluent software to track the droplet breakup and droplet-droplet coalescence, where the interfaces between the two phases are tracked by the Volume of Fluid (VOF) model. The material of droplet is water, while the continuous phase is oil. In this study, the effect of variables such as droplet diameter, droplet relative velocities as well as droplet motion directions on the time evolution of droplet-droplet coalescence and breakup is evaluated. The simulation results confirm that smaller droplet collisions lead to coalescence under wide ranges of droplet relative velocities, while larger droplet collisions result in droplet breakup at higher relative velocities. During coalescence, two droplets combine into one droplet, which deform in several times from one direction to orthogonal direction until recovering its shape or breakup. In addition, the simulation results show that fastest coalescence takes place when droplet collisions occur at optimum relative velocity, whereas droplet breakup occurs at higher velocities than the optimum velocity, and delay in coalescence happens at lower velocity. Furthermore, the simulation results clearly show that droplet moving direction play an important role in the occurrence of droplet coalescence and breakup. Comparison of the simulation results with the collected experimental data from literature confirm that the simulations are capable of predicting the evolution time of the droplet coalescence and breakup with high accuracy.
Ñèàíüñêèé òðàíñïîðòíûé óíèâåðñèòåò, Ñèàíü, Øýíüñè, ÊÍÐ Ñ ïîìîùüþ òðåõìåðíîé êîíå÷íîýëåìåíòíîé ìîäåëè èññëåäîâàíî ðàñïðåäåëåíèå êîíòàêòíûõ íàïðÿaeåíèé â êðèâîëèíåéíûõ ñî÷ëåíåíèÿõ âûñîêîíàãðóaeåííîé ãàçîâîé òóðáèíû â óñëîâèÿõ, ñîîòâåòñòâóþùèõ ñëó÷àþ îòðûâà ëîïàòêè. Äëÿ ðàçíûõ ïîëîaeåíèé îòîðâàâøèõñÿ ëîïàòîê íà äèñêå êàaeäîé ñòóïåíè ðàñïðåäåëåíèå êîíòàêòíûõ íàïðÿaeåíèé â êðèâîëèíåéíûõ ñî÷ëåíåíèÿõ â ñëó÷àå ïðèëîaeåíèÿ óñèëèé, ñîîòâåòñòâóþùèõ îòðûâó ëîïàòêè, ðàçëè÷àåòñÿ. Ïðè ýòîì òî÷êà ïðèëîaeåíèÿ è âåëè÷èíà óñèëèÿ, à òàêaeå ðàñïðåäåëåíèå óñèëèé çàòÿaeêè áîëòîâ êðåïëåíèÿ îêàçûâàþò ñóùåñòâåííîå âëèÿíèå íà ðàñïðåäåëåíèå êîíòàêòíûõ íàïðÿaeåíèé. Êðîìå òîãî, õàðàêòåð èçìåíåíèÿ êîíòàêòíûõ íàïðÿaeåíèé êàê ñ îäíîé, òàê è ñ äðóãîé ñòîðîíû "çóáà" ñî÷ëåíåíèÿ ïðè íàëè÷èè êðóòÿùåãî ìîìåíòà ðàçëè÷àåòñÿ èç-çà óñèëèÿ, îáóñëîâëåííîãî îòðûâîì ëîïàòêè. Ïîìèìî íîðìàëüíîé öåíòðîáåaeíîé ñèëû âîçíèêàåò íåóðàâíîâåøåííàÿ èçãèáàþùàÿ ñèëà. Ïîêàçàíî, ÷òî aeåñòêîñòü ñî÷ëåíÿåìîé ÷àñòè ðîòîðà ìåaeäó òîðöàìè êîìïðåññîðà è òóðáèíû, îïðåäåëÿåìàÿ aeåñòêîñòüþ åãî ñå÷åíèÿ, îêàçûâàåò âëèÿíèå íà ðàñïðåäåëåíèå êîíòàêòíûõ íàïðÿaeåíèé â êðèâîëèíåéíûõ ñî÷ëåíåíèÿõ. Âûïîëíåí ðàñ÷åò aeåñòêîñòè äëÿ êàaeäîãî èç òàêèõ ñî÷ëåíåíèé. Êëþ÷åâûå ñëîâà: êðèâîëèíåéíîå ñî÷ëåíåíèå, òðåõìåðíûé êîíå÷íîýëåìåíòíûé ìåòîä, îòðûâ ëîïàòêè, êîíòàêòíîå íàïðÿaeåíèå. Introduction. The curvic couplings are the important components of a gas turbine widely used in the aero-engine and electric power generation industry to drive rotating equipment and safely transfer high torque without relying on friction between the contacting surfaces of the curvic couplings. Its advantages such as reliable location, precise centring ability, excellent structural stability, strong load bearing ability definitely make the curvic couplings used more and more widely in the high speed rotating machine for torque transmission. The stress of the bolt with the curvic coupling in the event of a blade release in the three-dimentional finite element model was analyzed by Richardson et al. [1] for an improved design of the curvic coupling. The centre bolted rotor with the curvic couplings of an aero-engine was studied by Zeyong et al. [2] and Baian et al. [3]. However the statuses and stresses of the curvic couplings were never involved by them. Bannister [4] carried some work to determine the equivalent flexural stiffness of a curvic coupling in order to analyze the rotor character in
The purpose of this study is to investigate the numerical simulation method regarding the coalescence and breakup of droplets occurring during the gas‐liquid separation process and their influence on the separation efficiency and pressure drop. The Euler‐Lagrange method was used, and the discrete phase was simulated as an unsteady process. The results of the study indicate that numerical simulation results show better agreement with the experiment results when the coalescence and breakup model is taken into account. During the unsteady process, it was concluded that the simulation can meet the accuracy requirements as long as the Courant number of droplets is less than 1/3. The coalescence increases the droplet diameter, which improves the separation efficiency and reduces the pressure drop, whereas the opposite effect occurs with the breakup. Compared with other factors, the influence of the surface tension on the coalescence and breakup is more apparent, and droplets with a lower surface tension may be prone to coalescing or breaking. The coalescence occurs with a lower separation velocity, whereas breakup becomes predominant with higher separation velocity. The present research provides valuable suggestions on choosing strategies to improve the separation efficiency. For droplets with small surface tension, the separation velocity is restricted to not resulting breakup, and the separation efficiency can be improved by changing the shapes and spaces of the wave plate. In contrast, for droplets with large surface tension, increasing the velocity is an effective way to improve the separation efficiency.
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