The invention provides a gas introducing device before a gas
turbine. The gas introducing device before the gas
turbine comprises a
volute and a bypass gas introducing slot part; the
volute comprises junction surfaces and a gas introducing opening; the bypass gas introducing slot part is located at the upper part of a
turbine flow passage section along an axial direction, is connected with the turbine flow passage section and is circumferentially connected with the junction surfaces of the
volute; a part, within a connection position of the junction surfaces of the volute, of the outer
peripheral face of the bypass gas introducing slot part and the volute together form a
drainage flow passage circumferentially encircling the bypass gas introducing slot part; gas introducing slot openings which are arranged along a circumferential direction and penetrate through the bypass gas introducing slot part are formed in the part of the outer
peripheral face of the bypass gas introducing slot part; the gas introducing slot openings, the
drainage flow passage and an inner cavity of the turbine flow passage section communicate. According to the gas introducing device before the gas turbine, provided by the invention, gas discharged from an engine is evenly introduced into the volute, so that flow losses are avoided, power of the gas turbine is increased, an overall
expansion ratio of a two-stage turbine is increased, and moreover, influence of gas introducing
inlet pressure and gas introducing mixing on performance of the gas turbine and a
power turbine is reduced.