Numerical investigations on non-synchronous vibration and frequency lock-in of low-pressure steam turbine last stage

Zhu, Xiaocheng; Hu, Ping; Lin, Tingyu; Du, Zhimin

doi:10.1177/09576509211060678

Cited by 8 publications

(1 citation statement)

References 37 publications

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“…When designing the last blades, great emphasis is placed on the strength and dynamic design of the last rotor blades. [1][2][3]. For turbine designers it is important to define well the output, and for low volume conditions even the input of last stages [4][5][6] using numerical or sometimes even experimental methods.…”

Section: Introductionmentioning

confidence: 99%

Flow and Vibration in the Small Steam Turbine Last Stage

2022

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The paper deals with evaluation of experimental data obtained from the real-size 30 MW output Waste to Energy steam turbine. For many turbine regimes pressures in the last stage area were obtained. At the same time amplitudes of blade tips vibrations were measured of last rotor blades using the blade tip timing system and axial velocity of the steam at the last stage outlet. The obtained data are mutually correlated and relations are analysed between increased vibration values and pressure ratios at the last stage. Increased tip vibrations occur mainly in the area when the pressure ratio over the last blade tip and root is higher than one. In this case there is no expansion, but compression in the last stage of the turbine. The presented results contribute to understanding of processes in the last stage of the steam turbine, mainly for those regimes of turbine operation when its output is lower than 20 % of the nominal output, e.g. during the island regime.

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Section: Introductionmentioning

confidence: 99%

Flow and Vibration in the Small Steam Turbine Last Stage

2022

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4D Metamaterials with Zero Poisson's Ratio, Shape Recovery, and Energy Absorption Features

Hamzehei

Serjouei

et al. 2022

Adv Eng Mater

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Crashworthiness is the ability of the materials or structures to absorb impact energy through plastic deformations, friction, fracture, shear, bending, and even torsion. [1] Energy absorbers have been extensively used for different applications. The most prevalent applications can be found in the automotive, railway, and aerospace industries. [2,3] It is important to reduce the mortality rate caused by car crashes in the automotive industry. When it comes to passengers' safety, some critical crashworthy elements must be considered to design proper energy absorbers. The most vital item could be the initial reaction force caused by hitting an external object. [4] The lower the initial reaction force, the safer the occupants might be. A vehicle contains structural elements like rockers, pillars, and bumpers. Among these elements, the front bumper plays a vital role when it comes to energy absorption and is the most effective parameter for vehicle safety and occupants. The front bumper usually absorbs more than half of the kinetic energy during a car crash. [4] This is the main reason for magnifying the existence of high-performance energy absorbers Distinct from the initial reaction force, the crashworthy designers have been considering various main criteria for an ideal energy absorber, including high energy absorption performance, stability, and safety. Consequently, some design approaches such as gradual energy absorption (GEA), piecemeal energy absorption (PEA), and conventional energy absorption (CEA) have been proposed. [5][6][7] The absorbers designed based on the PEA and GEA approaches show different peak force levels in force-displacement relation, whereas the CEA-based absorbers show a peak force level in their forcedisplacement relation. Xu et al. [5] proposed a structure exhibiting the GEA for subway vehicles. The proposed energy absorber exhibits multistiffness behavior under the impact, showing different peak force levels as well. Afterward, the concept of piecemeal energy absorption (PEA) was introduced by Esa et al. [6] . The PEA concept is similar to the GEA concept. Due to the flexibility of the PEA concept over the GEA, this concept is extended to diverse applications. The PEA strategy provides lower damages under low-velocity impact and higher energy absorption capacity under high-velocity impact. Apart from the GEA and PEA concepts, most energy absorbers possess a CEA response. [7] The CEA response means a gradual increase in initial reaction forces under the impact and then the fluctuations in crushing forces are caused by overcoming the energy absorber's yield strength.

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Parrot Beak‐Inspired Metamaterials with Friction and Interlocking Mechanisms 3D/4D Printed in Micro and Macro Scales for Supreme Energy Absorption/Dissipation

et al. 2023

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Energy absorption and dissipation features of mechanical metamaterials have widespread applications in everyday life, ranging from absorbing shock impacts to mechanical vibrations. This article proposes novel bioinspired friction‐based mechanical metamaterials with a zero Poisson's ratio behavior inspired from parrot's beaks and manufactured additively. The mechanical performances of the corresponding metamaterials are studied at both macro and micro scales by experiments and finite element analysis (FEA). An excellent agreement is observed between the FEA and both microscopic and macroscopic scale experiments, showing the accuracy of the developed digital tool. Performances are compared to traditional triangular lattice metamaterials. Both experimental tests and FEA results demonstrate the following advantages: 1) absorbing and dissipating energy per unit of mass (SEA) at large compressive strains without global buckling; 2) bistable deformation patterns including friction‐based and interlocking mechanisms; 3) reversible deformation patterns after unloading; 4) shape recovery behavior after a heating–cooling process; and 5) the higher elastic modulus of micro metamaterials compared with their macro counterparts. This is the first demonstration of a bioinspired friction‐based design of 3D‐printed mechanical metamaterials that feature absorbing/dissipating energy, stability, and reversibility properties to cater to a wide range of sustainable meta‐cylinders in micro and macro scales.

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Numerical investigations on non-synchronous vibration and frequency lock-in of low-pressure steam turbine last stage

Cited by 8 publications

References 37 publications

Flow and Vibration in the Small Steam Turbine Last Stage

Flow and Vibration in the Small Steam Turbine Last Stage

4D Metamaterials with Zero Poisson's Ratio, Shape Recovery, and Energy Absorption Features

Parrot Beak‐Inspired Metamaterials with Friction and Interlocking Mechanisms 3D/4D Printed in Micro and Macro Scales for Supreme Energy Absorption/Dissipation

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