Analysis of Feedwater Pump Suction Pressure Decay Under Instant Turbine Load Rejection

1972 ◽  
Vol 94 (2) ◽  
pp. 83-88
Author(s):  
G. S. Liao ◽  
P. Leung
Keyword(s):  
Approximate Solutions ◽  
Maximum Load ◽  
Rate Of Change ◽  
Complete Analysis ◽  
Reliable Operation ◽  
Safe Operation ◽  
Suction System ◽  
Pressure Decay ◽  
Feedwater Pump ◽  
Regenerative Cycle

As steam-electric generating plant unit sizes increase, and as the capacities of the feedwater pumps increase, the design provision of an adequate suction for the safe operation of the feedwater pumps becomes increasingly important, especially when the pumps take suction from a deaerator within the regenerative cycle. The design provision of sufficient suction head for feedwater pumps operating under a maximum and stable turbine load is rather simple. However, the design of an adequate suction head to meet an instant turbine load rejection from maximum load is rather complex. It deals with the rate of pressure decay within the deaerator, mass of condensate stored, size of suction pipes, rate of change of condensate temperatures entering the deaerator, and numerous other transient parameters. Previously published literature [1–5] offers approximate solutions which assumed a constant temperature of condensate entering the deaerator during transient opertion under load rejection. Such an assumption generally results in an unnecessarily conservative design. Particularly, it may not be economically justifiable for very large units to be designed on that basis. This paper presents a complete analysis of this transient operating condition for the purpose of designing an economic optimum feedwater pump suction system for safe and reliable operation. Varying temperatures of the condensate entering the deaerator during transient operation are considered. Mathematic derivations augmented by numerical examples are included, to facilitate system design.

Investigation of G4-73 Centrifugal Fan Airfoil Stall Characteristics

2011 ◽  
Vol 383-390 ◽  
pp. 4221-4226
Author(s):  
Song Ling Wang ◽  
Zhe Liu ◽  
Lei Zhang
Keyword(s):  
Stokes Equations ◽  
Incidence Angle ◽  
Leading Edge ◽  
Suction Side ◽  
Navier Stokes ◽  
Centrifugal Fan ◽  
Reliable Operation ◽  
Safe Operation ◽  
Navier Stokes Equations ◽  
Strong Vortex

It’s of great significance for safe and reliable operation of fan to research on the stall characteristics of the airfoil. The 2D non-compressible Reynolds-Averaged Navier-Stokes equations was built to simulate the flow around the airfoil of G4-73No.8D centrifugal fan, a detailed numerical simulation under different angles has been carried out which based on the Realizable turbulence model with Fluent. The numerical results show that the smaller of the flow rate, the bigger incidence angle is, when the incidence angle is bigger than the critical incidence angle, the suction side stall appears. According simulation the airfoil stall appears when the incidence angle is -28°, with the increasing of the negative incidence angle, the separation point gradually moves to the leading edge. There is a strong vortex which locates at suction side =0.5,the alternating stress on the blade which caused by vortex will make the blade fatigue. If the incidence angle is less than -20°,there is no flow separation, therefore, to ensure the safe operation of the fan, the incidence angle should be less than -20°.

scholarly journals Trends in Improving Sensors for Controlling the Condition of Track Sections

2021 ◽  
Vol 264 ◽  
pp. 05045
Author(s):  
Ravshan Aliev
Keyword(s):  
Traffic Safety ◽  
Voltage Regulation ◽  
Rate Of Change ◽  
Electrical Parameters ◽  
Reliable Operation ◽  
Longitudinal Asymmetry ◽  
Compensation Methods ◽  
Track Circuits ◽  
Current Value ◽  
Element Base

Various principles can be used to implement intelligent track circuits: voltage regulation of the power supply, compensation methods for switching on rail lines and track circuit devices, receiver sensitivity adjustment, comparison of two electrical parameters of one, two, or more track circuits, as well as a combination of these methods. At present, such improvement of track circuits is becoming relevant, which would make it possible to exclude from the circuits one of the most unreliable elements - an insulating joint, use a modern microprocessor element base in devices for monitoring the state of track sections, thus ensure their reliable operation. This will significantly reduce the costs of building and operating interval control systems and increase train traffic safety. These requirements are met by intelligent track circuits, which consider the current value of the insulation resistance, the rate of change of this resistance, and the longitudinal asymmetry.

On Axially Symmetric Bending of Nearly Cylindrical Shells of Revolution

1956 ◽  
Vol 23 (1) ◽  
pp. 59-67
Author(s):  
R. A. Clark ◽  
E. Reissner
Keyword(s):  
Elastic Shell ◽  
Approximate Solutions ◽  
Rate Of Change ◽  
Axially Symmetric ◽  
Shells Of Revolution ◽  
Small Parameters ◽  
Constant Coefficients ◽  
Radial Dimension ◽  
Axial Dimension ◽  
Linear Differential

Abstract The words “nearly cylindrical” are used in this paper to describe a thin elastic shell of revolution which is such that (a) the maximum variation of the radial dimension is small compared to the average radial dimension, and (b) the rate of change of the radial dimension with respect to the axial dimension is small compared to unity. For any particular type of loading a nearly cylindrical shell may or may not exhibit a behavior similar to that of a shell which is exactly cylindrical. The purpose of this paper is to demonstrate this fact and to present a method for obtaining approximate solutions for the stresses and deflections in either event. The method involves a perturbation procedure based on the assumption that all desired quantities can be represented as expansions in powers of two small parameters. The procedure leads to a set of linear differential equations with constant coefficients, which may be solved successively.

A New Method of Quasi-Static Bifurcation Analysis and the Related Variational Theorem

1985 ◽  
Vol 9 (1) ◽  
pp. 26-31
Author(s):  
Xing Chen ◽  
Niels C. Lind
Keyword(s):  
Bifurcation Analysis ◽  
Static Problem ◽  
Approximate Solutions ◽  
Euler Method ◽  
Rate Of Change ◽  
New Method ◽  
New Approach ◽  
Variational Theorem ◽  
Creep Buckling ◽  
Thin Walled

The quasi-static problem is formulated in terms of rates. The traditional Euler method is reviewed. A new approach is developed for the quasi-static bifurcation analysis. Bifurcation is said to occur when there exists at least one additional, distinctive rate of change of a configuration in equilibrium. The related variational theorem is derived in the same manner that the Sanders variational theorem for creep was developed. An example is given for the creep buckling of a thin-walled cylindrical shell loaded in axial compression. It is concluded that the new method yields good approximate solutions but is apparently simpler than the Euler method.

scholarly journals Ensuring timely repair of power transformers based on data of complex diagnostics

2021 ◽  
Vol 288 ◽  
pp. 01034
Author(s):  
Makhsud Sultanov ◽  
Elena Zenina ◽  
Peter Shamigulov ◽  
Valentina Lunenko ◽  
Olga Zhelyaskova
Keyword(s):  
Neural Network ◽  
Life Cycle ◽  
Power System ◽  
Neural Network Model ◽  
Power Transformers ◽  
Power Equipment ◽  
Reliable Operation ◽  
Safe Operation ◽  
Power Stations ◽  
Initial Stage

Timely diagnosis of power transformers is an essential component of ensuring reliable and safe operation of power stations and substations, on which the reliability of the power system depends. Detection of defects in the initial stage allows to maintain reliable operation of transformers, helps to define the "life cycle" and simplify the planning of their replacement. The paper presents an analysis of existing approaches to the creation of power equipment diagnostics systems using the example of power transformers. A neural network model has been developed, demonstrating the possibility of using power transformers to estimate the current residual resource based on the analysis of available diagnostic data.

scholarly journals Experimental Investigation of the Fatigue Lifespan of Anchor Bolts with Consideration of Loading History

2021 ◽  
Vol 11 (23) ◽  
pp. 11399
Author(s):  
Miroslav Pástor ◽  
Pavol Lengvarský ◽  
Martin Hagara ◽  
Alžbeta Sapietová ◽  
Patrik Šarga
Keyword(s):  
Steel Structures ◽  
Economic Losses ◽  
Actual State ◽  
Second Phase ◽  
Reliable Operation ◽  
Safe Operation ◽  
Relevant Evidence ◽  
Axial Forces ◽  
Anchor Bolts ◽  
Two Phases

Preloaded bolted connections are one of the most used approaches for anchoring steel structures and equipment. Preload is induced by a mechanical tightening of the nut with the required torque. In the case of anchor bolts embedded in a concrete base, the prescribed tightening procedure has to be followed for safe and reliable operation. The present paper addresses the problem of anchoring a new casting pedestal using the original anchor bolts. The aim was to verify the original anchoring system’s reliable and safe operation, taking into account the current condition of the bolts. The analysed anchoring bolts are subjected to cyclic (disappearing) stress during the rotation of the casting pedestal. If the interplays between the anchor bolt and the concrete foundation were damaged, production would shut down, resulting in high economic losses. For this reason, the authors used a modified nut with a lightened first thread when investigating the actual state of the anchoring and setting the required preload. The shape and dimensions of the nut were determined based on the results of numerical modelling. The experimental measurements consisted of two phases. In the first phase, the values of axial forces in the anchor bolts at the required preload were set using the designed dynamometers. The second phase was focused on the operational measurements. The methodology of measuring the axial forces and the interpretation of the results obtained, including a comprehensive view of the anchoring safety, provides relevant evidence of the functionality and effectiveness of the proposed solution. Based on the results of the operational measurement and the prescribed handling of the casting pedestal, the lifespan of the anchoring was determined to be 3650 days under the loading cycles to date.

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