Review Of Aerodynamically Induced Forces Acting On Centrifugal Compressors, And Resulting Vibration Characteristics Of Rotors

TutorialThere are several sources of non-synchronous forced vibration of centrifugal compressor rotors. Many of them are aerodynamic phenomena, created within the gas path of the compressor. Phenomena such as impeller stall, diffuser stall (with and without vanes), and flow instabilities caused by impeller to diffuser misalignment, are all characteristic flow disturbances that can cause forced vibration. In fact, often the only indications of these phenomena are found in the resulting rotor vibration signals. Several phenomena that can cause non-synchronous vibration are reviewed, and for each one, background information, as well as detailed descriptions of the flow field, or other source of the excitation, is provided. This includes the use of CFD analytical results to describe the flow where applicable. The review also includes, when available, dynamic pressure transducer test data that can be used to verify the presence of the phenomena, and rotor vibration data indicating the presence of such phenomena. This includes test data of actual machines, indicating characteristics such as frequency and amplitude

Centrifugal Compressors 101 : Part 1

Short Cours

Centrifugal Compressors 101

Short Cours

Centrifugal Compressors 101

Short Cours

A REVIEW OF AERODYNAMICALLY INDUCED FORCES ACTING ON CENTRIFUGAL COMPRESSORS, AND RESULTING VIBRATION CHARACTERISTICS OF ROTORS

TutorialThere are several sources of non-synchronous forced vibration of centrifugal compressor rotors. Many of them are aerodynamic phenomena, created within the gas path of the compressor. Phenomena such as impeller stall, diffuser stall (with and without vanes), and flow instabilities caused by impeller to diffuser misalignment, are all characteristic flow disturbances that can cause forced vibration. In fact, often the only indications of these phenomena are found in the resulting rotor vibration signals. Several phenomena that can cause non-synchronous vibration are reviewed, and for each one, background information, as well as detailed descriptions of the flow field, or other source of the excitation, is provided. This includes the use of CFD analytical results to describe the flow where applicable. The review also includes, when available, dynamic pressure transducer test data that can be used to verify the presence of the phenomena, and rotor vibration data indicating the presence of such phenomena. This includes test data of actual machines, indicating characteristics such as frequency and amplitude

Squeeze Film Damper Bearing Experimental Vs Analytical Results For Various Damper Configurations.

LecturePg. 57-70Higher speeds, longer shafts, and increased power has made squeeze film damper (SFD) bearing performance increasingly more important to control both synchronous and subsynchronous fibration in rotating machinery. SFD bearing performance from a en stage high pressure barrel centrifugal compressor that has been specifically modified for SFD bearing development is presented. SFD bearing performance is investigated for both synchronous imbalance response and rotordynamic instability. A comparison is made of experimental and analytical results for a hydrodynamic ive shoe tilt pad bearing supported by an 0 ring centered damper eccentricity, e = 0.0 and e = 0.6), mechanically spring centered damper (e = 0.0 and e = 0.8), a bottom resting damper (e = 1 .0), end a standard nondamper (rigid support). The results of the tests clearly show that a properly designed SFD is an effective means of reducing the severity of critical speeds and improving the stability threshold of rotor bearing systems

Centrifugal Compressors 101

Short Cours

A REVIEW OF AERODYNAMICALLY INDUCED FORCES ACTING ON CENTRIFUGAL COMPRESSORS, AND RESULTING VIBRATION CHARACTERISTICS OF ROTORS

TutorialThere are several sources of non-synchronous forced vibration of centrifugal compressor rotors. Many of them are aerodynamic phenomena, created within the gas path of the compressor. Phenomena such as impeller stall, diffuser stall (with and without vanes), and flow instabilities caused by impeller to diffuser misalignment, are all characteristic flow disturbances that can cause forced vibration. In fact, often the only indications of these phenomena are found in the resulting rotor vibration signals. Several phenomena that can cause non-synchronous vibration are reviewed, and for each one, background information, as well as detailed descriptions of the flow field, or other source of the excitation, is provided. This includes the use of CFD analytical results to describe the flow where applicable. The review also includes, when available, dynamic pressure transducer test data that can be used to verify the presence of the phenomena, and rotor vibration data indicating the presence of such phenomena. This includes test data of actual machines, indicating characteristics such as frequency and amplitude

Mind the gap: a comparative study of migratory behavior in social amoebae

Social amoebae aggregate to form a multicellular slug that migrates some distance. Most species produce a stalk during migration, but some do not. We show that Dictyostelium giganteum, a species that produces stalk during migration, is able to traverse small gaps and utilize bacterial resources following gap traversal by shedding live cells. In contrast, we found that Dictyostelium discoideum, a species that does not produce stalk during migration, can traverse gaps only when in the presence of other species’ stalks or other thin filaments. These findings suggest that production of stalk during migration allows traversal of gaps that commonly occurs in soil and leaf litter. Considering the functional consequences of a stalked migration may be important for explaining the evolutionary maintenance or loss of a stalked migration

A Review of Aerodynamically Induced Forces Acting on Centrifugal Compressors, and Resulting Vibration Characteristics of Rotors

TutorialThere are several sources of non-synchronous forced vibration of centrifugal compressor rotors. Many of them are aerodynamic phenomena, created within the gas path of the compressor. Phenomena such as impeller stall, diffuser stall (with and without vanes), and flow instabilities caused by impeller to diffuser misalignment, are all characteristic flow disturbances that can cause forced vibration. In fact, often the only indications of these phenomena are found in the resulting rotor vibration signals. Several phenomena that can cause non-synchronous vibration are reviewed, and for each one, background information, as well as detailed descriptions of the flow field, or other source of the excitation, is provided. This includes the use of CFD analytical results to describe the flow where applicable. The review also includes, when available, dynamic pressure transducer test data that can be used to verify the presence of the phenomena, and rotor vibration data indicating the presence of such phenomena. This includes test data of actual machines, indicating characteristics such as frequency and amplitude