Shaft seal and gas turbine

A shaft seal comprising:

• a plurality of flexible thin plates having a width in an axial direction of a rotary shaft, said rotary shaft having an outer periphery, tips of said thin plates sliding against a peripheral face of said rotary shaft, and outer peripheral bases of said thin plates being secured to a casing side maintaining a gap therebetween, said thin plates being laminated in a peripheral direction of said rotary shaft, sealing the outer periphery of said rotary shaft, an acute angle formed between the thin plates and the peripheral face of said rotary shaft;
• a low pressure side side-plate and a high pressure side side-plate provided on both sides of said thin plates in the axial direction of said rotary shaft;
• a gas pressure adjusting mechanism, which when said thin plates are viewed cross-sectionally along an imaginary plane is perpendicular to a direction of the width of said thin plates, a face of each thin plate facing the rotary shaft is deemed a bottom face and a rear side is deemed a top face, and gas pressure from said high pressure side side-plate to said low pressure side side-plate is applied to said thin plates, ensuring that a gas pressure applied to said bottom face is higher than a gas pressure applied to said top face at a given point along a cross-sectional face of said thin plates,
• wherein said gas pressure adjusting mechanism comprises said low pressure side side-plate and said high pressure side side-plate, which are positioned so that the a size of a low pressure side gap between said thin plates and said low pressure side side-plate is larger than a high pressure side gap between said thin plates and said high pressure side side-plate,
• wherein said gas pressure adjusting mechanism comprises a flexible plate, which is flexible in the axial direction of said rotary shaft and is arranged on the a high pressure side of said thin plates, said flexible plate being configured such that a top end contacts the high pressure side side-plate and is spaced from said thin plates and a bottom end biases said thin plates and is spaced from the high pressure side side-plate, and
• wherein said gas pressure adjusting mechanism makes the gas, said gas entering from between the high pressure side side-plate and the peripheral face of the rotary shaft, flow along the top and bottom faces of the thin plates and spread to a diagonally opposite angle, and said gas pressure adjusting mechanism simultaneously makes a low pressure region expand at the outer peripheral base of said thin plates.