Multiple staged compressor with last stage airfoil cooling

#None.

#1. Field of the Invention

#The present invention relates go gas turbine engines, and more specifically to a high pressure ratio compressor with last stage airfoil cooling used in a gas turbine engine.

#FIG. 1 shows a cross section view of a first embodiment of the multiple stage compressor of the present invention.

#FIG. 2 shows a cross section view of a second embodiment of the multiple stage compressor of the present invention having heat pipes.

#The present invention is a multiple stage compressor that produces a very high pressure ratio such that cooling of the last stage or stages of the compressor air required. The compressor is intended to be used in a gas turbine engine such as an aero engine or an IGT engine. However, the present invention could be used in any turbomachine in which a multiple stage compressor is used that produces the high pressure ratio in which cooling of the last stage airfoils is required to prevent thermal damage.

#FIG. 1 shows a cross section of the compressor of the present invention in which a number of stages are present with each stage having a stator or guide vane located upstream from an associated rotor blade. In a typical multiple stage compressor of an aero engine, the outer diameter of the compressor is about at a constant radial diameter while the inner diameter is conical shaped with a decreasing airfoil spanwise height in the downstream direction. The inlet air to the compressor is at atmospheric pressure. The compressor progressively compresses the air as the compressed air passes through the multiple stages. As the air is compressed, the temperature of the compressed air increases. A typical compressor will increase the compressed air temperature about 90 degrees F. in each stage. In the last stages, the compressed air can be at such a high temperature that the airfoils can be damaged from the high temperature. The material properties of these airfoils are such that the high temperature compressed airs passing through these airfoils exceed the safe temperature level for the materials.

#In the present invention is FIG. 1, the last stage vanes 12 and blades 11 include closed loop cooling air passages to pass cooling air through the airfoils without discharging the cooling air into the high temperature compressed air stream through the compressor. The internal airfoil cooling passages can be any type of prior art closed loop cooling passage circuit that makes use of well known convection cooling and impingement cooling of airfoils. Compressed cooling air from a middle stage 15 of the compressor is bled off and passed through a cooling air passage in the rotor shaft assembly and into the inlet of the internal cooling air passage of the rotor blade. The cooling air passes through the rotor blade cooling passage and then flows through a return air passage also in the rotor shaft to be discharged into the compressor at a stage 16 upstream from the bled off stage. This is due to the loss of pressure in the cooling air from passing through the cooling passages in the rotor shaft and the rotor blade.