Impeller Stall Induced by Reverse Propagation of Non-Uniform Flow

LecturesIn the case of centrifugal compressors, minor non-uniform flow upstream of the impeller is induced by an asymmetrical configuration in the circumferential direction at the compressor suction casing. This non-uniform flow is transmitted to the impeller discharge, but this minor non-uniform flow does not usually cause an adverse effect on the impeller stage performance. However, we found this is amplified at the return channel due to flow separation at reduced flows (depending on return channel geometry), and the amplified non-uniform flow did induce impeller stall by reverse propagation from the return channel to the impeller. These non-uniform flows caused a significant operating range reduction for a large flow coefficient impeller. The aerodynamics issues were mitigated using CFD analysis techniques, and eventually confirmed by the compressor performance during shop performance testing. The OEM conducted the CFD analyses using two (2) return channel geometries with several CFD models to verify the effect of the return channel geometry on impeller stall and to Copyright© 2018 by Turbomachinery Laboratory, Texas A&M Engineering Experiment Station confirm the most suitable CFD modeling method for stall evaluation. Shop performance tests utilizing both return channel geometries were conducted and compared to the CFD analyses. These studies were conducted while collaborating with the end-user. The steady CFD calculation was conducted with frozen rotor interface between full annulus impeller and stator parts. The modeling of diffuser and return channel was varied as follows: (1) 1-pitch model for the return channel with mixing plane at diffuser (2) Full-annulus model for the return channel with a mixing plane at the diffuser (3) Full-annulus model for the return channel without a mixing plane at the diffuser From the above studies and the shop performance testing, it was confirmed that the proposed CFD modeling method could simulate the measurements taken during the shop performance tests and that the CFD modeling met

Impeller Stall Induced by Reverse Propagation of Non-Uniform Flow

LecturesIn the case of centrifugal compressors, minor non-uniform flow upstream of the impeller is induced by an asymmetrical configuration in the circumferential direction at the compressor suction casing. This non-uniform flow is transmitted to the impeller discharge, but this minor non-uniform flow does not usually cause an adverse effect on the impeller stage performance. However, we found this is amplified at the return channel due to flow separation at reduced flows (depending on return channel geometry), and the amplified non-uniform flow did induce impeller stall by reverse propagation from the return channel to the impeller. These non-uniform flows caused a significant operating range reduction for a large flow coefficient impeller. The aerodynamics issues were mitigated using CFD analysis techniques, and eventually confirmed by the compressor performance during shop performance testing. The OEM conducted the CFD analyses using two (2) return channel geometries with several CFD models to verify the effect of the return channel geometry on impeller stall and to Copyright© 2018 by Turbomachinery Laboratory, Texas A&M Engineering Experiment Station confirm the most suitable CFD modeling method for stall evaluation. Shop performance tests utilizing both return channel geometries were conducted and compared to the CFD analyses. These studies were conducted while collaborating with the end-user. The steady CFD calculation was conducted with frozen rotor interface between full annulus impeller and stator parts. The modeling of diffuser and return channel was varied as follows: (1) 1-pitch model for the return channel with mixing plane at diffuser (2) Full-annulus model for the return channel with a mixing plane at the diffuser (3) Full-annulus model for the return channel without a mixing plane at the diffuser From the above studies and the shop performance testing, it was confirmed that the proposed CFD modeling method could simulate the measurements taken during the shop performance tests and that the CFD modeling met

Järviseudun ammatti-instituutin opetusnavetan työohjeiden päivittäminen

Opinnäytetyöni käsittelee Järviseudun ammatti-instituutin opetusnavetan työohjeiden päivittämistä. Työohjeet olisi hyvä olla jokaisessa työpaikassa. Niistä on apua uuden työntekijän perehdyttämisessä sekä myös kauemmin poissa olleen työntekijän palatessa työpaikalle. Hyvät työohjeet tuovat työpaikalle myös taloudellista hyötyä, sillä ne vähentävät työtapaturmista johtuvia sairaslomia sekä luovat työntekijöille valmiudet tehokkaaseen työskentelyyn. Järviseudun ammatti-instituutin opetusnavetta on sekä työ- että oppimispaikka. Tämän vuoksi sinne halutaan kunnolliset ohjeet navetan töistä. Tavoitteena on saada helposti ymmärrettävät ohjeet, joita pystyvät hyödyntämään myös koulun ulkomaalaiset oppilaat. Tästä syystä ohjeissa käytetään kuvia tekstin ohella. Ohjeita tehtiin kahdenlaisia. Navetan perustöistä tehtiin yksityiskohtaiset kuvalliset ohjeet pienen tekstin kera. Nämä ohjeet perustuvat täysin navetan työskentelytapoihin, jotka valokuvattiin vaihe vaiheelta. Toiset ohjeet ovat enemmän teksti-muodossa, ja käsittelevät navetassa harvemmin tehtäviä työtehtäviä, jotka vaativat enemmän ammattiosaamista ja suomenkielentaitoa.This thesis is the made work instructions for Järviseutu Vocational Institute’s cowshed. Work instructions are very important in every workplace. They help when you teach new employee or when a former employee comes back to work from a long absence. Well-made work instructions are economically profitable, they decreases occupational accidents and helps employees to work effectively. Järviseutu Vocational Institute’s cowshed is a workplace and also place to study. That is a reason why work instructions have to be in good order. The objective was to create easily understandable instructions which foreigner students could also understand. That is the reason why photos with text were used in the work instructions. There are two kinds of instructions. One about the cowshed’s daily works with photos and a short text: these instructions are detailed and based on completely on the working habits in the cowshed; they were photographed step by step. The second instructions are about non-daily works. That require more professional abilities and Finnish language skills

Impeller Stall Induced By Reverse Propagation Of Non-Uniform Flow Generated At Return Channel

LectureIn the case of centrifugal compressors, minor non-uniform flow upstream of the impeller is induced by an asymmetrical configuration in the circumferential direction at the compressor suction casing. This non-uniform flow is transmitted to the impeller discharge, but this minor non-uniform flow does not usually cause an adverse effect on the impeller stage performance. However, we found this is amplified at the return channel due to flow separation at reduced flows (depending on return channel geometry), and the amplified non-uniform flow did induce impeller stall by reverse propagation from the return channel to the impeller. These non-uniform flows caused a significant operating range reduction for a large flow coefficient impeller. The aerodynamics issues were mitigated using CFD analysis techniques, and eventually confirmed by the compressor performance during shop performance testing. The OEM conducted the CFD analyses using two (2) return channel geometries with several CFD models to verify the effect of the return channel geometry on impeller stall and to confirm the most suitable CFD modeling method for stall evaluation. Shop performance tests utilizing both return channel geometries were conducted and compared to the CFD analyses. These studies were conducted while collaborating with the end-user. The steady CFD calculation was conducted with frozen rotor interface between full annulus impeller and stator parts. The modeling of diffuser and return channel was varied as follows: 1) 1-pitch model for the return channel with mixing plane at diffuser 2) Full-annulus model for the return channel with a mixing plane at the diffuser 3) Full-annulus model for the return channel without a mixing plane at the diffuser. From the above studies and the shop performance testing, it was confirmed that the proposed CFD modeling method could simulate the measurements taken during the shop performance tests and that the CFD modeling method utilized was key to properly evaluating stall phenomena

Enhanced astaxanthin production by oxidative stress using methyl viologen as a reactive oxygen species (ROS) reagent in green microalgae Coelastrum sp.

Microalgae are known to be a potential resource of high-value metabolites that can be used in the growing field of biotechnology. These metabolites constitute valuable compounds with a wide range of applications that strongly enhance a bio-based economy. Among these metabolites, astaxanthin is considered the most important secondary metabolite, having superior antioxidant properties. For commercial feasibility, microalgae with enhanced astaxanthin production need to be developed. In this study, the tropical green microalgae strain, Coelastrum sp., isolated from the environment in Malaysia, was incubated with methyl viologen, a reactive oxygen species (ROS) reagent that generates superoxide anion radicals (O2-) as an enhancer to improve the accumulation of astaxanthin. The effect of different concentrations of methyl viologen on astaxanthin accumulation was investigated. The results suggested that the supplementation of methyl viologen at low concentration (0.001 mM) was successfully used as a ROS reagent in facilitating and thereby increasing the production of astaxanthin in Coelastrum sp. at a rate 1.3 times higher than in the control

Analysis on the cryogenic stability and mechanical properties of the LHD helical coils

Transient normal-transitions have been observed in the superconducting helical coils of LHD. Propagation of a normal-zone is analyzed with a numerical simulation code that deals with the magnetic diffusion process in a pure aluminum stabilizer. During excitation tests, a number of spike signals are observed in the balance voltage of the helical coils, which seem to be caused by mechanical disturbances. The spike signals are analyzed by applying pulse height analysis and the mechanical properties of the coil windings are investigated

Essential Role of the \u3ci\u3eCrk\u3c/i\u3e Family-Dosage in DiGeorge-Like Anomaly and Metabolic Homeostasis

CRK and CRKL (CRK-like) encode adapter proteins with similar biochemical properties. Here, we show that a 50% reduction of the family-combined dosage generates developmental defects, including aspects of DiGeorge/del22q11 syndrome in mice. Like the mouse homologs of two 22q11.21 genes CRKL and TBX1, Crk and Tbx1 also genetically interact, thus suggesting that pathways shared by the three genes participate in organogenesis affected in the syndrome. We also show that Crk and Crkl are required during mesoderm development, and Crk/Crkl deficiency results in small cell size and abnormal mesenchyme behavior in primary embryonic fibroblasts. Our systems-wide analyses reveal impaired glycolysis, associated with low Hif1a protein levels as well as reduced histone H3K27 acetylation in several key glycolysis genes. Furthermore, Crk/Crkl deficiency sensitizes MEFs to 2deoxy-D-glucose, a competitive inhibitor of glycolysis, to induce cell blebbing. Activated Rapgef1, a Crk/Crkl-downstream effector, rescues several aspects of the cell phenotype, including proliferation, cell size, focal adhesions, and phosphorylation of p70 S6k1 and ribosomal protein S6. Our investigations demonstrate that Crk/Crkl-shared pathways orchestrate metabolic homeostasis and cell behavior through widespread epigenetic controls

Asymmetrical normal-zone propagation observed in the aluminum-stabilized superconductor for the LHD helical coils

Transient normal-transitions have been observed in the superconducting helical coils of the Large Helical Device (LHD). Stability tests have been performed for an R&D coil as an upgrading program of LHD, and we observed asymmetrical propagation of an initiated normal-zone. In some conditions, a normal-zone propagates only in one direction along the conductor and it hence forms a traveling normal-zone. The Hall electric field generated in the longitudinal direction in the aluminum stabilizer is a plausible candidate to explain the observed asymmetrical normal-zone propagation

Analysis of the normal transition event of the LHD helical coils

Normal transitions and a subsequent quench were experienced with the pool-cooled helical coils of the Large Helical Device (LHD) during its excitation test. Although the initiated normal zone once started to recover, a disruptive transverse propagation followed and triggered an emergency discharging program. The cryogenic stability of the composite-type superconductor has been studied by sample experiments as well as by numerical calculations. Due to the rather long magnetic diffusion time constant in the pure Al stabilizer, transient stability of the conductor seems to play an important role for driving finite propagation of a normal zone. The cause of the final quench is also discussed from the viewpoint of cooling deterioration due to a possible accumulation of He bubble