BLISK or IBR (Integrated Blade Rotors) are among the most innovative and challenging components in modern gas turbine engines. BLISK may be integrally cast, machined from a solid piece of material or made by welding individual blades to the rotor disc. Initially BLISK was used only in first stage LP compressor. Its low weight and excellent aerodynamic efficiency making it popular for use in the HP stage also.
CONVENTIONAL DISK Vs BLISK
Conventional rotor disk comprises rotor blades secured on the disk with the help of nuts and bolts or screws and with the help of retaining rings. The blades are generally secured with the disk in one of the three methods:
Simple but not very effective method of retaining pin and lock nut.
The fir tree base is of greater complexity and is used only where the blade loading is high.
The most common method used to secure blade with the disk is the dovetail type base design.
It can be seen that all three designs having their own complexity in manufacturing and require additional components to firmly hold the detachable rotor blades with the disk under all load conditions. Further blades are not push fit type. There is some tolerance given between two mating parts for easy fitment and removal during repair and servicing. This gap reduces the compressor efficiency since air leaks through this gap. Compressor pressure ratio reduces.
In BLISK, rotors blades are the integral part of the disk and do not require any component to hold the rotor blades. Also, the cross sectional area of the disk is less as compared to conventional disk. This reduces the weight of the compressor upto 25% - 30% and since there is no gap present at the base of the two rotor blades its compression efficiency increases.
Appreciable weight reduction up to 30%. Gives better T/W ratio.
Decreasing the number of components within the compressor and hence reducing the...
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