Steam turbine with resonance chamber
A steam turbine with a resonance chamber in the outer annulus opposite a rotating blade row. The resonance chamber provides passive resonance to place the excitation at a frequency away from the natural frequency of the blades.
1. A steam turbine comprising:
a rotor;
a circumferentially distributed rotating row of blades extending radially from a root of the blades attached to the rotor to a tip portion of the blades;
an outer annulus circumferentially enclosing the row of blades;
a resonance chamber having an opening in a region of the outer annulus defined by a radial projection of the root of the blades onto the outer annulus; and
wherein the resonance chamber is configured for a frequency between 2.5 to 6 engine orders; and wherein the resonance chamber is configured as a helmholtz resonator.
2. The steam turbine of claim 1 wherein the opening is opposite the tip portion of the blades.
3. The steam turbine of claim 1 comprising a plurality of circumferentially distributed resonance chambers.
4. The steam turbine of claim 1 , wherein the resonance chamber is configured for a frequency between 3 to 5 engine orders.
5. The steam turbine of claim 1 wherein the steam turbine is a multi-stage steam turbine having a downstream last stage wherein the row of blades are last stage blades.
6. The steam turbine of claim 1 wherein the steam turbine is a low pressure steam turbine configured to operate with an exhaust pressure at or below ambient pressure.