Indian Journal of

 Engineering & Materials Sciences

http : // www.niscair.res.in

 

VOLUME 9

NUMBER 6

DECEMBER 2002

CODEN : IEMSEW

 

ISSN : 0971-4588

 

Special Issue on “ Fluid Mechanics & Fluid Power”

 

CONTENTS

 

Foreword

 399

 

 

Papers

 

Effect of different annulus heights on performance of annular gas turbine model combustor

 

403

  Gourav Garg, Sanjeev Bharani, S N Singh & V Seshadri

 

 

 

Simulation of small disturbance waves over alternate rigid and compliant panels

 409

  P K Sen, S Hegde & P W Carpenter

 

 

 

Dynamic behaviour of indirect coupled heat exchanger systems

 414

  N M Rao, B Maiti & P K Das

 

 

 

Distortion of guide vane assembly in a bulb turbine due to cavitation and reverse water flow

 

419

  R Rudramoorthy, N Kuppuswamy, D Rajenthirakumar & K V Manikandan

 

 

 

Experimental investigation of tip clearance effects on flow field in an annular turbine rotor cascade

 

424

  C Venkateswara Babu, N Sitaram & M Govardhan

 

 

 

Flow distribution in spherical header of a liquid metal-cooled fast breeder reactor

432

  K Natesan, K Velusamy, P Selvaraj & P Chellapandi

 

 

 

Design and development of water hydraulic pressure compensated flow control valve

 440

  Saurabh Pandharikar, Abhijit Khuperkar, N L Soni & R G Agrawal

 

 

 

A combined numerical-experimental study of convection in an axisymmetric differentially heated fluid layer

 

448

  Atul Srivastava & P K Panigrahi

 

 

 

Convection in differentially heated superposed air-water layers

 455

  Sunil Punjabi, Anamika Sethia & K Muralidhar

 

 

 

An experimental study of convective heat transfer from flat and ribbed surface

 464

  Andallib Tariq, S K Swain & P K Panigrahi

 

 

 

Effect of inlet swirl and dump-gap on the wall pressure distribution of a model can-combustor

 

472

  Abdur Rahim, S V Veeravalli & S N Singh

 

Effects of particle-size and size distribution on estimating erosion wear of cast iron in sand-water slurries

 

480

  B K Gandhi & S V Borse

 

 

 

Annual Index

 487

 

 


Indian Journal of Engineering & Materials Sciences
Vol. 9, December 2002, pp. 403-408

 

 

Effect of different annulus heights on performance of
annular gas turbine model combustor†

Gourav Garga, Sanjeev Bharanib, S N Singha* & V Seshadria

 

Present study is a numerical investigation on an annular gas turbine combustor model with the simulation of dump diffuser and annuli. Uniform pressure distribution around the liner is desired for designed flow-split through the liner holes. An attempt has been made to achieve uniform velocity and pressure conditions in the annuli (around the liner) by changing the annuli height thereby changing the outer annulus area-to-inner annulus area ratio. It is found that for the area ratio of 2.56, uniform velocity and constant pressure condition is achieved around the bluff body representing the liner in the combustor model.

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 9, December 2002, pp. 409-413

 

 

Simulation of small disturbance waves over alternate rigid and compliant panels

 

P K Sena, S Hegdea  & P W Carpenterb

 

In this paper, the simulation of two-dimensional small disturbance waves propagating over alternate rigid and compliant panels is discussed. Due to the abrupt change in the material properties of the wall at the junction of rigid-compliant panels, a sudden change is expected in the amplitude of the oncoming wave. An analytical-cum-numerical method is developed for the calculation of amplitude ratios at the two sides of rigid-compliant wall junctions.

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 9, December 2002, pp. 414-418

 

 

Dynamic behaviour of indirect coupled heat exchanger systems

 

N M Rao, B Maiti & P K Das

 

In this paper, the dynamic behaviour of the indirect coupled heat exchanger system has been reported. Three partial differential equations of energy balance for three fluids have been derived and solved simultaneously by adopting the finite element method. The responses of coupling fluid temperatures, hot and cold fluid temperatures have been studied for the step and sinusoidal changes in hot fluid inlet temperature. The maximum over-all effectiveness of the system has occurred at a unique value of the non-dimensional coupling fluid heat capacity rate. This unique value is identical to the value, which could be obtained from an analytically derived equation by the previous investigator. However, as expected, the situation changes when there is sinusoidal change in hot fluid inlet temperature.

 

Indian Journal of Engineering & Materials Sciences

Vol. 9, December 2002, pp. 419-423

 

 

Distortion of guide vane assembly in a bulb turbine due to cavitation
and reverse water flow

 

R Rudramoorthy, N Kuppuswamy, D Rajenthirakumar & K V Manikandan

 

This paper focuses on the problems involved in a deep setting bulb turbine in a hydro- electric power plant and possible solutions to avoid cavitation. Analysis is carried out based on the measured data on the distortion in the guide vane assembly. To eliminate cavitation and distortion in these turbines, suggestions are evolved between the deep setting and reverse tailrace water flow into the turbine assembly.

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 9, December 2002, pp. 424-431

 

Experimental investigation of tip clearance effects on flow field in an annular turbine rotor cascade

C Venkateswara Babu, N Sitaram* & M Govardhan

 

The present paper reports results of an experimental investigation on the effects of tip clearance in a high deflection annular turbine rotor cascade. The measurements are carried out at the inlet, in the blade passage and at the exit of the cascade using a five-hole probe and a seven-hole probe. The results indicate that the incoming flow to the rotor cascade is uniform and the incidence is about +2o. When the clearance is increased, the size and the magnitude of the tip clearance loss region increase. The flow near the hub experiences overturning, whereas near the casing the flow substantially underturns due to tip clearance. The underturning increases with tip clearance. Secondary and tip clearance losses steeply increase downstream of the blade trailing edge indicating losses due to the wake and clearance flow mixing with the main flow.

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 9, December 2002, pp. 432-439

 

 

Flow distribution in spherical header of a liquid metal-cooled fast breeder reactor

 

K Natesan, K Velusamy, P Selvaraj & P Chellapandi

 

Liquid sodium from primary pump of a typical Liquid Metal-cooled Fast Breeder Reactor (LMFBR) reaches a spherical header through a vertical pipe and flows to the inlet plenum of the reactor through two discharge pipes, which connect the header to the plenum. The header is provided with a central cone and flow directing baffles for the purpose of having a smooth propagation of sodium flow and hence a reduced pressure drop. 3D hydraulic analyses of sodium flow in the header for various design configurations have been carried out to investigate the effectiveness of flow baffles and to assess the pressure drop in the header. It has been found that a configuration of 3D baffle combined with a central cone reduces the pressure drop in the header to the desirable level (1.7 mlc).

 

Indian Journal of Engineering & Materials Sciences

Vol. 9, December 2002, pp. 440-447

 

 

Design and development of water hydraulic pressure compensated
flow control valve

Saurabh Pandharikar, Abhijit Khuperkar, N L Soni & R G Agrawal

 

The Pressure Compensated Flow Control Valves (PCFCVs) are required for maintaining constant flow in a hydraulic circuit as there is fluctuation in supply or return pressure and other resistance on actuators. The water hydraulic PCFCV has been designed which can control the load flow as well as pump pressure. For achieving constant flow requirement, a hydrostate has been designed which maintains a constant differential pressure across a manually settable valve and hence maintain constant flow across the valve. The pump pressure control is achieved by controlling the sensing line pressure of hydrostate with the help of an air piston actuated pilot operated relief valve. The paper discusses conceptual design, mathematical modelling, parameter optimization and design of PCFCV.

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 9, December 2002, pp. 448-454

 

 

A combined numerical-experimental study of convection in an axisymmetric differentially heated fluid layer

Atul Srivastava & P K Panigrahi

 

Buoyancy-driven convection in a horizontal differentially heated fluid layer has been analysed numerically and compared with the experimental results obtained for a circular axisymmetric fluid layer, the side walls of the cavity being thermally insulated and of constant radius. The employed Rayleigh numbers are 5861 and 12,124 and the working fluid air. The governing equations are continuity equation, Navier-Stokes equation and the energy equation. Due to the axisymmetric nature of the fluid cavity, the governing equations have been solved in r-z coordinate system. A fine uniform grid of 601x81 is employed. Experiments have been conducted in the fluid layer of 0.64 m diameter and 23 mm vertical height with the same working fluid as considered in numerical simulation. A Mach-Zehnder interferometer has been used to visualize the long-time convection patterns in the fluid layer. The goal of the study is to investigate the influence of Rayleigh number on the steady (long time) thermal field, quantitative analysis of heat transfer rates and comparison with the experimental results. A good agreement has been found in qualitative as well as quantitative sense between theoretical and experimental results.


 

 

Indian Journal of Engineering & Materials Sciences

Vol. 9, December 2002, pp. 455-463

 

 

Convection in differentially heated superposed air-water layers

 

Sunil Punjabi, Anamika Sethia & K Muralidhar

 

Convection in a differentially heated two-layer system consisting of air and water has been studied experimentally using laser-interferometry. The cavity used for flow visualization is square in cross-section and rectangular in plan having dimensions of 447×32.1×32.1 mm3. Experiments with the cavity (half-filled with water, the rest being air) are reported here. The following temperature differences have been imposed across the hot and the cold walls of the superposed layers: (i) ΔT=10 K, (ii) ΔT=15 K , and (iii) ΔT=18 K. The present study is aimed at understanding the following issues: (a) the influence of Rayleigh number on the steady thermal field, and (b) flow coupling mechanisms between the layers. The present investigations show that the thermal field in the fluid layers is primarily determined by the temperature difference and hence the Rayleigh number. Further, the two-layers are thermally coupled at a lower Rayleigh number, while the mechanical and thermal coupling both become significant at higher Rayleigh numbers.

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 9, December 2002, pp. 464-471

 

 

 

An experimental study of convective heat transfer from flat and ribbed surfaces

 

Andallib Tariq, S K Swain & P K Panigrahi

 

Heat transfer and friction characteristics of flow in a rectangular channel with a solid rib mounted on the bottom surface of the channel have been investigated experimentally. The experiments have been carried out at Reynolds number (based on hydraulic diameter of the channel) range of 12,800 to 29,400. The skin friction coefficient, Nusselt number, velocity and temperature profile results are presented. The surface temperature images obtained with the help of liquid crystal thermography supplement the understanding of flow physics with qualitative explanation. The average Nusselt number for the ribbed flow case is higher in comparison to that for the flat surface. The increase in skin friction coefficient for the ribbed flow case is comparatively less than the Nusselt number increase, indicating the effectiveness of the ribbed surface in heat transfer enhancement applications. The liquid crystal thermography images show the flow in the downstream region of the rib to be two dimensional in nature. The recirculation and reattachment region for the ribbed flow case and their role in heat transfer effectiveness is clearly visible in the liquid crystal images.

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 9, December 2002, pp. 472-479

 

 

Effect of inlet swirl and dump-gap on the wall pressure distribution of a model can-combustor

 

Abdur Rahima, S V Veeravallib & S N Singhb

 

Wall static pressure distributions along the casing and liner wall have been measured using a Scanivalve digital manometer, for a model can-combustor under isothermal flow conditions for non-swirling and swirling flow at inlet with different positions of the liner (dump-gap). It is observed that swirl reduces the size of wall recirculation zone and permits earlier flow development whereas, dump-gap alters the reattachment length for weak swirling flows only. It is also observed that liner wall pressure (specially dome region) has a strong dependence on dump-gap for strong swirling flows due to formation of a central recirculation zone.

 

Indian Journal of Engineering & Materials Sciences

Vol. 9, December 2002, pp. 480-486

 

Effects of particle size and size distribution on estimating erosion wear
of cast iron in sand-water slurries

B K Gandhia & S V Borseb

 

Erosion wear of cast iron has been evaluated in a pot tester for narrow-sized and multi-sized particulate sand-water slurries. The effects of particle size and size distribution on erosion wear have been analyzed and the applicability of median diameter or weighted mean diameter as an effective particle size for multi-sized slurry for estimating erosion wear has been investigated. It is observed that the mean particle size of the narrow-sized particulate slurry can be taken as the effective particle size for evaluating the erosion wear. However, the observed trend of variation of erosion wear with particle size is not followed by median or weighted mean diameters of multi-sized slurries, showing large deviations.