Blade erosion

Superheaters and Reheaters A superheater raises the temperature of the steam generated above the saturation level. An important function is to minimize moisture in the last stages of a turbine to avoid blade erosion. With continued increase of evaporation temperatures and pressures, however, a point is reached at which the available superheat temperature is insufficient to prevent excessive moisture from forming in the low-pressure turbine stages. This condition is resolved by removing the vapor for reheat at constant pressure in the... 

The following briefly reviews the parameters that affect erosion and the programs instituted by Elliott to obtain basic erosion data. The data from these studies have been integrated into Elliott s erosion prediction program. Table 4-13 lists some of the more important parameters affecting expander blade erosion from solid particles. Many of these parameters directly relate to the particle itself. 

Ulke, A. and Rouleau, W. T., The Effeets of Seeondary Flows on Turbine Blade Erosion, ASME Paper No. 76-GT.74. 

Veloeity triangles at the mean seetion of the blading are to be submitted by the Seller. The blading shall be designed to minimize blade erosion eaused by tlie partieulate entrained in the flue gas witli tapered and twisted rotor and stator airfoils. The blade design used shall have at least tliree years of sueeess-ful operating time in FCC serviee for tlie frame proposed. 

Inspeetion during shutdown showed evidenee of blade erosion and pits loeated on the leading edge and the eoneave side of the trailing edge. For expanders operating at a eonstant speed, the veloeity diagram depends on the absolute speed of the mass earrier. The absolute speed, Cj, may be ealeulated from the nozzle formula ... 

Miller, H.F., Blade Erosion—FCCU Power Recovery Expanders, D-R Turbo Products Division, Olean, N.Y, 1989. 

Since moisture is a major concern for turbines designed for nuclear operation, a number of erosion-control techniques were used in the LP turbine. For example, adequate axial spacing between the stationary and the rotating blades minimizes blade erosion. Moisture is removed at all extraction points in the moisture region. 

However, the temperature range of the Rankine cycle is severely limited by the nature of the working fluid— water. Adding superheat in an attempt to circumvent this will remove the cycle from isothermal heat addition. Increasing the temperature range without superheating leads to excessive moisture content in the vapor turbines, resulting in blade erosion. 

The gas Brayton cycle adds heat in a isobaric process over a large temperature range. The temperature level is independent of the pressure level. No blade erosion occurs in the gas turbine. However, the compression process of the gas Brayton cycle requires large work input. The back-work ratio is small. 

Use of SRC-II distillates in stationary gas combustion turbines is also of significant interest. The low levels of trace metals and inorganics suggest minimal difficulty in regard to turbine blade erosion or corrosion. The higher radiant heat effect on the combustor walls caused by the lower hydrogen content... 

Boiler tube corrosion and turbine blade erosion... 

The quality of the steam produced by the steam generators must be sufficient to ensure good thermodynamic cycle efficiency and to minimise turbine blade erosion. 

It extracts some of the wetness from the steam as it expands through the turbine cylinders by selectively bleeding relatively wet steam for its feed heaters, thereby improving thermodynamic cycle efficiency and minimising turbine blade erosion. 

F.P. Bowden, Organizer, Defoimation of Solids by the Impact of Liquids (and Its Relation to Rain Damage in Aircraft and Missiles, Blade Erosion in Steam Ihrinnes, Cavitation Erosion), Philos. Trans. R. Soc. (London) A, Vol 260 (No. 1110), 1966... 

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