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Flow Investigations in the Crossover System of a Centrifugal Compressor Stage
Reddy, K. Srinivasa,Murty, G.V. Ramana,Dasgupta, A.,Sharma, K.V. Korean Society for Fluid machinery 2010 International journal of fluid machinery and syste Vol.3 No.1
The performance of the crossover system of a centrifugal compressor stage consisting of static components of $180^{\circ}$ U-bend, return channel vanes and exit ducting with a $90^{\circ}$ bend is investigated. This study is confined to the assessment of performance of the crossover system by varying the shape of the return channel vanes. For this purpose two different types of Return Channel Vanes (RCV1 and RCV2) were experimentally investigated. The performance of the crossover system is discussed in terms of total pressure loss coefficient, static pressure recovery coefficient and vane surface pressure distribution. The experimentation was carried out on a test setup in which static swirl vanes were used to simulate the flow at the exit of an actual centrifugal compressor impeller with a design flow coefficient of 0.053. The swirl vanes are connected to a mechanism with which the flow angle at the inlet of U-bend could be altered. The measurements were taken at five different operating conditions varying from 70% to 120% of design flow rate. On an overall assessment RCV1 is found to give better performance in comparison to RCV2 for different U-bend inlet flow angles. The performance of RCV2 was verified using numerical studies with the help of a CFD Code. Three dimensional sector models were used for simulating the flow through the crossover system. The turbulence was predicted with standard k-$\varepsilon$, 2-equation model. The iso-Mach contour plots on different planes and development of secondary flows were visualized through this study.
Babu Reddy, L.P.,Megha, R.,Chethan, B.,Raj Prakash, H.G.,Ravikiran, Y.T.,Ramana, C.H.V.V.,Kim, D. ELSEVIER 2018 INORGANIC CHEMISTRY COMMUNICATIONS Vol.98 No.-
<P><B>Abstract</B></P> <P>In the present work, we prepared magnesium ferrite/molybdenum trioxide (MFMO) nanocomposite using mechano chemical mixing method for humidity sensor at room temperature. Enhancement in active sites for water adsorption in the composite due to the presence of MoO<SUB>3</SUB> confirmed from X-ray diffraction (XRD) studies. Change in grain size distribution and increase in intergranular pores in the composite favouring water adsorption confirmed from its scanning electron microscopy (SEM) image. Increased agglomeration of nano sized particles and improved crystallinity of the composite confirmed from Transmission electron microscopy (TEM) studies and selected area electron diffraction (SAED) pattern. The composite showed maximum sensing response of 4902 as against 183 of MF in the range 11%–97% RH. The response and recovery times of the composite were found to be 45 s and 74 s respectively while those of MF 225 s and 364 s respectively. The nanocomposite sample showed stable humidity sensing ability and a low humidity hysteresis. Molybdenum trioxide plays a major role in enhancing the humidity sensing performance of MFMO composite at room temperature. The sensing mechanism discussed on the basis of chemisorptions, physisorption and capillary condensation processes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Humidity sensing response of magnisium ferrite (MF) and magnesium ferrite-molybdenum trioxide (MFMO) composite presented. </LI> <LI> The MFMO showed maximum sensing response of 4902 as against 183 of MF in the range 11%-97% RH. </LI> <LI> The response and recovery times of the composite were found to be 45 s and 74 s respectively. </LI> <LI> The sensing mechanism MFMO discussed on the basis of chemisorptions, physisorption and capillary condensation processes. </LI> </UL> </P>
M. VENKATESWARLU,G. V. RAMANA REDDY,D. V. LAKSHMI 한국산업응용수학회 2014 Journal of the Korean Society for Industrial and A Vol.18 No.3
The objective of the present study is to investigate thermal diffusion and radiation effects on unsteady MHD flow past a linearly accelerated vertical porous plate with variable temperature and also with variable mass diffusion in presence of heat source or sink under the influence of applied transverse magnetic field. The fluid considered here is a gray, absorbing/emitting radiation but a non-scattering medium. At time t > 0, the plate is linearly accelerated with a velocity u = u0t in its own plane. And at the same time, plate temperature and concentration levels near the plate raised linearly with time t. The dimensionless governing equations involved in the present analysis are solved using the closed analytical method. The velocity, temperature, concentration, skin-friction, the rate or heat transfer and the rate of mass transfer are studied through graphs in terms of different physical parameters like magnetic field parameter (M), radiation parameter (R), Schmidt parameter (Sc), Soret number (So), Heat source parameter (S), Prandtl number (Pr), thermal Grashof number (Gr), mass Grashof number (Gm) and time (t).
BOUNDS ON THE GROWTH RATE FOR THE KUO PROBLEM
S. LAVANYA,V. GANESH,G. VENKATA RAMANA REDDY The Korean Society for Computational and Applied M 2023 Journal of applied mathematics & informatics Vol.41 No.2
We consider Kuo problem of hydrodynamic stability which deals with incompressible, inviscid, parallel shear flows in the 𝛽-plane. For this problem, we derived instability region without any approximations and which intersects with Howard semi-circle region under certain condition. Also, we derived upper bound for growth rate and amplification factor of an unstable mode and proved Howard's conjecture.
On homogeneous shear flows with bottom cross section
S. Lavanya,V. Ganesh,G. Venkata Ramana Reddy 한국전산응용수학회 2023 Journal of applied mathematics & informatics Vol.41 No.5
We consider inviscid, incompressible homogeneous shear flows of variable cross section known as extended Rayleigh problem. For this extended Rayleigh problem, we derived instability region which intersect with semi-circle instability region under some condition. Also we derived condition for stability , upper bound for amplification factor and growth rate of an unstable mode.
On the bounds for Wave Stability of Stratified Shear Flows
S. Lavanya,V. Ganesh,G. Venkata Ramana Reddy 한국전산응용수학회 2024 Journal of applied mathematics & informatics Vol.42 No.1
We consider incompressible, inviscid, stratified shear flows in $\beta $ plane. First, we obtained an unbounded instability region intersect with semi-ellipse region. Second, we obtained a bounded instability regions depending on Coriolis, stratification parameters and basic velocity profile. Third, we obtained a criterion for wave stability. This has been illustrated with standard examples. Also, we obtained upper bound for growth rate.