Fan Laws, The User And Limits In Predicting Centrifugal Compressor Off Design Performance.

LecturePg. 91-100The fan laws, particularly what the limits are in their use is described. The derivation is covered very briefly. To help understand some of the fan law uses, centrifugal impeller characteristics are covered, particularly some of the things controlling the shape of the curve. A discussion of the fan law deviations in an individual impeller is covered. Multistage centrifugals are covered using two, four, and six stage configurations. A set of stage curves are made up for use of the study. These curves reflect two basic impeller designs. The designs result in a high (15 percent) and a low (five percent) head rise. Also included is a study where the effect of molecular weight is presented. Speed variations are covered and compared to the fan law prediction with the deviations being shown

Torsional-Damping-Transient and Steady State

Panel SessionPg. 203Couplings play an important role in the solution of many turbomachinery torsional problems. Due to inherently high inertias, many systems have torsional natural frequencies in the units' operating range, and operational problems may result. The coupling is a convenient location in the train to make system torsional changes with a minimum effect on other system parameters. These modifications may incorporate a stiffness correction, the addition of damping, or both, in order to torsionally tune the system for reliable operation

Turbomachinery Problems - Lube And Seal System Revisited

LecturePg. 119-123.Even an apparently well-designed lube and seal system can and will cause turbomachinery problems to occur if all operating parameters are not considered in the design of the lube and seal system. Lube and seal system design, fabrication and installation have made great progress in basic design in the past decade. The introduction and use of API 614 has made its contribution. However - despite these advances - periodically turbomachinery suffers unscheduled outages - sometimes major damage due to the loss of lubricating oil. The paper will discuss some of the problems experienced in the past several years

Centrifugal Compressor Application Sizing, Selection, And Modelling.

Tutorialpg. 195-202The objective here is to build on the fan law paper presented at the Twentieth Turbomachinery Symposium [1]. The centrifugal sizing and modelling tutorial draws on the pseudo compressor stage curves presented in the fan law paper. The presenters will elaborate and demonstrate the effects of curve shape, gas properties, and other factors on stage matching. For comparison, fan law and actual section properties will be compared to help the ultimate practitioner with the decision of when various methods are reasonable and applicable. Estimating centrifugal compressor fit for a given application using manufacturer's catalog data will be covered, along with aerodynamic modelling of actual compressor hardware after purchase for monitoring of off-design, fouling, or potential rerating

Critical Speeds And The Importance Of Stiffness - A Case Study In The Design And Testing Of A Large Mechanical Drive Steam Turbine To API Standard 612.

LecturePg. 73-80Rotordynamics has long been one of the major considerations in the design of variable speed rotating equipment. Bearing support stiffness is a significant factor in the designer's ability to predict critical speeds and response to unbalance. This case study is used to describe the influence of support stiffness on the rotordynamics performance of a large variable speed mechanical drive steam turbine. This joint effort by the user and machinery vendor identifies several practical issues in meeting the intent of API Standard 612, Third Edition. Modem analytical techniques can be used to predict bearing support stiffness in both the horizontal and vertical directions. When the stiffness in the two directions are dissimilar, multiple critical speeds may occur, which complicate the interpretation of API 612 test results. Effects of critical speeds on response to unbalance are discussed. Also presented are some analytical and experimentally determined dynamic characteristics obtained during the design and test

Practical Approach to Surge and Surge Control Systems

TutorialPg. 147-174This paper addresses the area of compressor stability, surge and surge control and relates to the practical aspects involved. An emphasis is placed on the physical understanding of surge phenomena and on the practical limitations of surge control systems. Topics discussed are physical interpretation of instability, causative factors, types of stall, machine and process design factors, surge effects and characteristics, control system types and practical application aspects. Some case studies also are presented. The discussion primarily relates to centrifugal compressors, but several aspects pertain to axial flow compressors as well. The paper is split into three sections: Section A consists of an introduction to surge and a discussion of centrifugal compressor design and process factors that affect operating stability. Section B discusses the various types of control schemes and surge protection devices. Several examples and common pitfalls are addressed. Section C addresses the important design tool, surge system simulation. Several references are provided to enable the reader to pursue this topic in greater detail

Xist regulation and function eXplored

X chromosome inactivation (XCI) is a process in mammals that ensures equal transcript levels between males and females by genetic inactivation of one of the two X chromosomes in females. Central to XCI is the long non-coding RNA Xist, which is highly and specifically expressed from the inactive X chromosome. Xist covers the X chromosome in cis and triggers genetic silencing, but its working mechanism remains elusive. Here, we review current knowledge about Xist regulation, structure, function and conservation and speculate on possible mechanisms by which its action is restricted in cis. We also discuss dosage compensation mechanisms other than XCI and how knowledge from invertebrate species may help to provide a better understanding of the mechanisms of mammalian XCI

Compressors: selection and sizing

This practical reference provides in-depth information required to understand and properly estimate compressor capabilities and to select the proper designs. Engineers and students will gain a thorough understanding of compression principles, equipment, applications, selection, sizing, installation, and maintenance. The many examples clearly illustrate key aspects to help readers understand the ""real world"" of compressor technology.Compressors: Selection and Sizing, third edition is completely updated with new API standards. Additions requested by readers include a new section on d