End wall flow characteristics and overall performance of an axial flow compressor stage

This review indicates the possible future directions for research on endwall flows in axial flow compressors. Theoretical investigations on the rotor blade endwall flows in axial flow compressors reported here include the secondary flow calculation and the development of the momentum integral equations for the prediction of the annulus wall boundary layer. The equations for secondary vorticity at the rotor exit are solved analytically. The solution includes the effects of rotation and the viscosity. The momentum integral equations derived include the effect of the blade boundary layers. The axial flow compressor facility of the Department of Aerospace Engineering at The Pennsylvania State University, which is used for the experimental investigations of the endwall flows, is described in some detail. The overall performance and other preliminary experimental results are presented. Extensive radial flow surveys are carried out at the design and various off design conditions. These are presented and interpreted in this report. The following experimental investigations of the blade endwall flows are carried out. (1) Rotor blade endwall flows: The following measurements are carried out at four flow coefficients. (a) The rotor blade static pressures at various axial and radial stations (with special emphasis near the blade tips). (b) The hub wall static pressures inside the rotor blade passage at various axial and tangential stations. (2) IGV endwall flows: The following measurements are carried out at the design flow coefficient. (a) The boundary layer profiles at various axial and tangential stations inside the blade passage and at the blade exit. (b) Casing static pressures and limiting streamline angles inside the blade passage

Blade end wall flows in compressors

A brief summary of previous work carried out on end wall flow phenomena is presented with major emphasis on annulus wall boundary layer

A synthetic 13-residue peptide corresponding to the hydrophobic region of bovine seminalplasmin has antibacterial activity and also causes lysis of red blood cells

Seminalplasmin (SPLN), a 47-residue peptide present in bovine seminal plasma, is one of the few proteins isolated from mammalian sources having potent antibacterial activity. SPLN also interacts with sperm acrosomal and plasma membranes. On the basis of analysis of the primary structure of SPLN with respect to its relative hydrophobicity and hydrophilicity, a region comprising of 13-amino acids, Pro-Lys-Leu-Leu-Glu-Thr-Phe-Leu-Ser-Lys-Trp-Ile-Gly, has been delineated. It is demonstrated that a synthetic peptide corresponding to this 13-residue region inhibits growth of Escherichia coli like SPLN and also has the ability to lyse red blood cells

Interaction of indolicidin, a 13-residue peptide rich in tryptophan and proline and its analogues with model membranes

Indolicidin is a 13-residue broad-spectrum antibacterial peptide isolated from bovine neutrophils. The primary structure of the peptide ILPWKWPWWPWRR-amide (IL) reveals an unusually high percentage of tryptophan residues. IL and its analogues where proline residues have been replaced by alanine (ILA) and trp replaced by phe (ILF) show comparable antibacterial activitieso While IL and ILA are haemolytic, ILF does not have this property. Since aromatic residues would strongly favour partitioning of the peptide into the lipid bilayer interface, the biological activities of IL and its analogues could conceivably arise due perturbation of the lipid bilayer of membranes. We have therefore investigated the interaction of IL and its analogues with lipid vesicles. Peptides IL and ILA bind to lipid vesicles composed of phosphatidylcholine and phosphatidylethanol amine: phosphatidyl glycerol: cardiolipin. The position of λmax and I- quenching experiments suggest that the trp residues are localized at the membrane interface and not associated with the hydrophobic core of the lipid bilayer in both the peptides. Hence, membrane permeabilization is likely to occur due to deformation of the membrane surface rather than formation of transmembrane channels by indolicidin and its analogues. Peptides ILA, IL and ILF cause the release of entrapped carboxyfluorescein from phosphatidyl choline vesicles. The peptide-lipid ratios indicate that ILF is less effective than IL and ILA in permeabilizing lipid vesicles, correlating with their haemolytic activities

Effect of Gurney Flap Configuration on the Performance of a Centrifugal Fan

The present investigation is conducted to study the effect of Gurney flap configuration on the performance of a centrifugal fan at different Reynolds numbers. Gurney flaps of different configurations, such as angle, quarter round and half round corresponding to a nominal height of 1.2 mm (1.94% of the impeller blade spacing at tip) height are attached to the pressure surface of the centrifugal fan impeller blade tip. Performance tests are carried out on the centrifugal fan with a vaneless diffuser at five Reynolds numbers viz. 0.30, 0.41, 0.55, 0.69 and 0.80×105 based on the impeller tip speed, impeller blade exit height and kinematic viscosity, both with and without Gurney flaps. From the performance curves it is found that fan performance improves significantly with Gurney flaps at low Reynolds numbers and improves marginally at high Reynolds numbers. Gurney flap of angle configuration of height as small as 1.94% of the impeller blade spacing at tip increases head coefficient by 5.2% and increases the volume flow rate across the fan by 5.4% at the lowest Reynolds number of 0.30×105. Even though there is increase in both head and flow coefficients with other Gurney flap configurations (quarter round and half round), they are always less than that for the angle Gurney flap. The effect of Reynolds number on the performance curves is found to be negligible with Gurney flaps, whereas the effect of Reynolds number on the performance curves of the impeller without Gurney flap is found to be considerable. Additional experiments conducted with Gurney flaps of two configurations, viz. angle and quarter round, with a larger height of 2.5 mm (4.05% of the impeller blade spacing at tip) attached on the pressure surface of the centrifugal fan impeller blade tip have shown that the performance of the fan with quarter round GF is better than the performance of the fan with angle GF

Ethnobotanical Survey of Medicinal Plants Used in the Treatment of Dermatogenic Diseases in Chittoor District, Andhra Pradesh, India

An ethno-medicobotanical survey of plants used in the treatment of dermatogenic diseases in Chittoor District, Andhra Pradesh was conducted. The information was collected on the basis of personal interviews with traditional healers, tribal doctors and old women of the society. The investigation revealed that 24 plant species belonging to 18 families and 21 genera are commonly used in the treatment of skin ailments

Performance Improvement of a Centrifugal Compressor by Passive Means

The present experimental investigation deals with performance improvement of a low-speed centrifugal compressor by inexpensive passive means such as turbulence generator placed at different positions and partial shroud near the rotor blade tip. The experiments are carried out at three values of tip clearance, namely 2.2%, 5.1%, and 7.9% of rotor blade height at the exit. Performance tests are carried out for a total of 13 configurations. From these measurements, partial shroud is found to give the best performance. The improvement in the compressor performance may be due to the reduction of tip leakage flows by the small extension of partial shroud (2 mm on the pressure surface side). Although there is nominal change in performance due to turbulence generator (TG), TG has beneficial effect of increased operating range

Free and bound choline blood levels after phosphatidylcholine

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/110000/1/cptclpt198264.pd