Stability Analysis of a Multi-stage Gas Compressor With Swirl-brakes Using Three Dimensional Transient CFD Model

LectureMinimizing fluid induced forces through the secondary leakage flow paths in shrouded centrifugal impellers is crucial to improve the rotordynamic stability of high-pressure centrifugal gas compressors. Swirl brakes (SBs) are widely used in turbomachinery to reduce the fluid induced forces and enhance the system rotordynamic behavior. Prior to the present study, swirl-brakes of a high-pressure multistage compressor were designed using 3D steady-state computational fluid dynamics (CFD) analysis and verified through multiple fullscale closed loop tests for a compressor, operating with and without the SBs. In the present study, a 3D transient CFD analysis is conducted to calculate the fluid induced rotordynamic coefficients of a Teethon- Rotor (TOR) seal and the impeller shroud cavity. Full 360o fluid domains including the impeller, the shroud cavity, and TOR seals with either a swirl-brake or without it are numerically modeled. A mesh deformation technique is employed to follow the whirling rotor motion of the impeller. To evaluate the capability of the transient CFD model, comparisons are made between the prior test results and predictions from the current numerical study. The cross-coupled destabilizing forces as calculated from CFD are then compared with the methodologies recommended by API 617 and a few other researchers in the literature. In addition, the destabilizing forces calculated through the CFD methodology are used in rotordynamic simulations of the rotor, with and without SBs. Comparisons of simulation results to test results and field performance show good qualitative correlation. CFD predicts forces in the secondary flow path (without SBs) that cause early signs of instability observed in the compressor. The same methodology with SBs predicts cross-coupling forces that are benign, which is also confirmed by stable operation of the same compressor when rebuilt with SBs. These results are included in the paper

Towards a novel content organisation in agriculture using semantic technologies: a study with topic maps as a tool

Agricultural information management needs to be responsive to the needs of varied stakeholders, and content repurposing to suit multiple audiences is a key requirement. A framework that combines the semantic web techniques of Topic Maps (TM) and a global agricultural thesaurus, the FAO AGROVOC, has been developed on a pilot basis for five crops. The framework when overlaid on a web-based collection of information objects reveals interesting possibilities, especially in presenting the repository content in noticeably different ways to a subject-matter specialist or to an extension worker. Results are discussed and opportunities for further development are briefly described

Design and Implementation of Swirl Brakes for Enhanced Rotordynamic Stability in an Off-shore Centrifugal Compressor

Technical BriefsRotordynamic stability of gas compressors at high speeds and operating pressures is a significant technical challenge. Dynamic instability must be avoided for the sake of safe, reliable and continuous operation of turbomachinery. Experience and literature have shown that one of the main sources of instability is the swirl within the secondary leakage path in shrouded impellers, especially the swirl entering the shroud seals. The technical brief presents the design and implementation of swirl brakes for centrifugal compressors with Teeth-on-Rotor seal configurations for shrouded impellers. Discussion includes (a) aerodynamic design of swirl brakes with the help of Computational Fluid Dynamics (CFD), (b) sub-scale testing of the swirl brake design in an instrumented single-stage test rig to measure the inlet swirl ratio in a shrouded impeller, (c) full-scale prototype shop-testing and qualification, with and without the swirl brakes in a closedloop test facility, and (d) results of incorporating the swirl brakes at an off-shore compressor installation to improve rotordynamic stability

Electric-Motor-Driven Gas Compressor Packages: Starting Methods for Large Electrical Motors and Torsional Integrity

Tutoria

Electric-Motor-Driven Gas Compressor Packages: Starting Methods for Large Electrical Motors and Torsional Integrity

Tutoria

Design and Implementation of Swirl Brakes for Enhanced Rotordynamic Stability in an Off-shore Centrifugal Compressor

Technical BriefsRotordynamic stability of gas compressors at high speeds and operating pressures is a significant technical challenge. Dynamic instability must be avoided for the sake of safe, reliable and continuous operation of turbomachinery. Experience and literature have shown that one of the main sources of instability is the swirl within the secondary leakage path in shrouded impellers, especially the swirl entering the shroud seals. The technical brief presents the design and implementation of swirl brakes for centrifugal compressors with Teeth-on-Rotor seal configurations for shrouded impellers. Discussion includes (a) aerodynamic design of swirl brakes with the help of Computational Fluid Dynamics (CFD), (b) sub-scale testing of the swirl brake design in an instrumented single-stage test rig to measure the inlet swirl ratio in a shrouded impeller, (c) full-scale prototype shop-testing and qualification, with and without the swirl brakes in a closedloop test facility, and (d) results of incorporating the swirl brakes at an off-shore compressor installation to improve rotordynamic stability

Effects of prolactin on ventricular myocyte shortening and calcium transport in the streptozotocin-induced diabetic rat

© 2020 Cardiology; Cell biology; Endocrinology; Molecular Biology; Pathophysiology; Pharmacology; Physiology; prolactin; Diabetes mellitus; heart; Ventricular myocytes; Contraction; Calciu

Carbon nanotube based optical ammonia sensor

72 p.Photoluminescence emission from carbon nanotubes and their potential applications in chemical sensing have been studied in this project. Single walled carbon nanotubes were suspended in SDBS surfactant solution. The surfactant is used to separate the carbon nanotube bundles into individual tubes, as the photoluminescence is observed only from individual tubes and the bundles will effectively quench the same. Besides, it is very crucial to control various factors such as SWNT concentration, pH of the solution etc to obtain a good PL spectrum.Master of Science (Microelectronics