Overall Performance Of Turbine Research Articles

Numerical investigation of the effects of ITD length on low pressure nozzle

The advantage of high efficiency, low SFC (Specific Fuel Consumption), ultra-high bypass ratio turbofan engine attracts more and more attention in modern commercial engine. The intermediate turbine duct (ITD), which connects high pressure turbine (HPT) with low pressure turbine (LPT), has a critical impact on the overall performance of turbine by guiding flow coming from HPT to LPT without too much loss. Therefore, it becomes more and more urgent to master the technique of designing aggressive, even super-aggressive ITD. Much more concerns have been concentrated on the duct. However, in order to further improve turbine, LPT nozzle is arranged into ITD to shorten low pressure axle. With such design concept, it is obvious that LPT nozzle flow field is easily influenced by upstream duct structure, but receives much less interests on the contrary. In this paper, numerical method is used to investigate the effects of length of ITD with upstream swirl blades on LPT nozzle. Nine models with the same swirl and nozzle blades, while the length of ITD is the only parameter to be changed, will be discussed. Finally, several conclusions and advices for designers are summarized. After changing axial length of ducts, inlet and outlet flow field of nozzle differs, correspondingly. On the other hand, the shearing stress on nozzle blade (suction and pressure) surface presents individual feature under various inlet flow. In addition to that, “Clocking-like effect” is described in this paper, which will contribute much to the pressure loss and should be paid enough attention.

Numerical study of blade deterioration effects on an industrial gas turbine stage performance and flow field

Turbine blades deteriorate over operation and overall performance of turbine decreases due to dust entry, fuel impurities, chemical reactions with air impurities, sulphur in the fuel, incomplete combustion and unburned carbon production. In this article, the effects of blade surface roughness and geometry changes caused by operation conditions on turbine performance were numerically calculated. Numerical calculations were carried out for the fourth stage of an axial turbine which was experimentally tested in the Technical University of Hannover, Germany. Results showed a good agreement with the previous measurements. To find out the effect of blade deteriorations on turbine stage performance and flow field, blade deteriorations including blade surface roughness, tip clearance increment and fouling on vane and blade of turbine were applied in four different mass flow rates to the three-dimensional numerical model.

Numerical Study on Performance Characteristics of Draft Tube of Mixed Flow Hydraulic Turbine

Draft tube is an important component of the hydraulic reaction turbine and affects the overall performance of turbine to a large extent. The flow inside the draft tube is complex because of the whirling flow coming out of runner and its diffusion along the draft tube. The kinetic energy coming out of runner is recovered in draft tube and part of recovery meets the losses. In the present work, the computational fluid dynamics (CFD) has been used for flow simulation in complete mixed flow Francis turbine for performance analysis for energy recovery, losses and flow pattern in an elbow draft tube used in Francis turbine at different operating conditions. The overall performance of the turbine at some typical operating regimes is validated with the experimental results and found to be in close comparison.DOI: http://dx.doi.org/10.3126/hn.v10i0.7103 Hydro Nepal Vol.10 January 2012 48-52