Patent ID: 7819623

Claim:
A clearance control apparatus for controlling the clearance between a rotary assembly and a casing surrounding the rotary assembly, said apparatus comprising: a temperature measuring device to measure the temperature of a portion of the rotary assembly; a cooling arrangement to cool the casing comprising a supply of a cooling medium, a conduit for supplying the cooling medium from the supply to the casing to cool the casing, and a flow regulator to regulate the flow of cooling medium from the supply to the casing; and a control system associated with the temperature measuring device and the cooling arrangement to control the extent of cooling of the casing, said extent of cooling being dependent upon the temperature of the aforesaid portion, wherein the flow regulator comprises a valve and the control system transmits the flow regulation signal to open or close the valve by a desired extent and a position sensor on the flow regulator to provide a flow regulation feedback signal to the control system, said flow regulation feedback signal relating to the condition of the flow regulator and the extent of supply of the cooling medium, said flow regulation signal being based upon said flow regulation feedback signal.