Turbomachines

 
Part-I: Flow through Draft Tube and Tail race channel (TRC)
Turbulent flow through draft tube and Tail Race Channel (TRC) of Maneri Bhali Hydroelectric Project Stage-II is simulated using CFD. The free surface is evaluated using a Euler-Euler model and the turbulence characteristics are evaluated using two equation κ-ε (turbulent-kinetic energy and eddy dissipation) model. The entire domain including the draft tub and the tailrace sections is meshed with a structured grid. Two phase turbulent flow simulations are taken up for flow through the draft tube geometry along with the tailrace. Air is taken as the secondary phase, above the water level in the tailrace channel. Several planes in the draft tube section are considered for the purpose of flow visualization. Analysis reveals the issue of improper evacuation of the flow through draft tube when all the turbine units were running at full load. This is because of a nuzzling effect near the outlet structure of the tailrace. Such restrictions induce violent vortices in the tail race channel and reverse flow in the draft tube.
Part-II: Flow through Turbine units including draft tube and TRC
The simulations considered in Part-II involve all the major components of the hydroelectric power plant including spiral casing, the runner, the draft tube and the tailrace. Results for all the four runners running at designed discharge of 35 cumecs, rated head of 247.6m and rated output of 76 MW are analysed along with the results for 10% excess of total installed capacity of 304 MW (i.e. 334 MW) as was suggested by UJVNL vide letter no. 336/E&MDesign-II/CFD dated 10th July 2010. This report aims at apprising UJVNL about the nature of flow at the present power output of the station and suggest that the rated 304 MW as well 334MW (up-rated) cannot be reached safely unless the evacuation from the tailrace is improved.
These investigations were carried out to ascertain the effect of concrete cladding on the rise in water level at the outlet of Tail race channels in THDC project. The concrete cladding is provided on the opposite bank of the river. Numerical simulations are carried out for flow in the river pocket with the provision of cladding on the opposite bank and without it. The rise in water level at TRT 1 and TRT 2 are analysed due to the presence of cladding. Results are obtained for full load as well as part load operating conditions of the plant. An estimate is also made for the equivalent power loss expected due to the rise of water levels in the tailrace tunnels due to the provision of cladding.
Hammering sound is reported in the machines from Tail Race Channel (TRC) area while operating the machines between ranges of 75MW to 90MW load at Koteshwar HEP of THDCIL, India. The main objective of present study was to identify the possible reasons for undesirable sound in the machine and TRC area under part load conditions through CFD analysis of Hydro Turbine Units. The systematic study including the selection of turbulence model, performance of selected turbulence model on physical model data and the performance of prototype plant under different operating condition is analysed. The CFD simulations reveals that the wake regime behind the guide vane and the oscillating nature of vortex rope are the possible reasons for generation of noise at part load operation between 75MW – 85 MW of the units.
Analysis of flow through hydro turbine unit including tail race channel of Manerbhali hydroelectric project Stage-I for finalization of the location of outfall gate in the tail race channel. The complete CFD analysis of the power plant is carried out into two parts.  In part – I the CFD simulation of flow through existing tail race channel are reported in isolation first. Then the simulations are carried out by placing the proposed outfall gate structure at four different locations (at 65 m, 70m, 75m and 80 m chainage distance) in the Tail Race Channel (TRC) for finding out the reverse flow in the tailrace channel and rise in water level in the TRC associated with the obstruction created due to placing the proposed outfall gate in TRC. In part – II, the complete CFD simulation of flow through turbine units including spiral cashing, stator, rotor passage, draft tube and tail race channel of Manerbhali-I hydroelectric project is reported for estimating the loss of power associated with the positioning of the proposed outfall gate at 65m, 70m and 75 m chainage distance in the tailrace channel.
Mixed flow compressors are modified version of the centrifugal flow compressors and combine the advantages of axial and centrifugal flow compressors. The present work utilises a design methodology for the impeller of the mixed flow compressor such that it can work with an efficiency and mass flow rate close to axial flow compressor along with the pressure ratio per stage, resistance to foreign particles and ruggedness comparable to a centrifugal compressor. The focus is in understanding the various design philosophies and pick out one which best suits in accordance with available inputs and parameters.