JPS5874801A - Mechanism for automatically adjusting flow quantity of gas turbine cooling air - Google Patents

Abstract

PURPOSE:To maintain the temperatures in the vicinities of the root portions of moving vanes at a predetermined value to maintain high efficiency of the titled mechanism by utilizing a bimetal in a seal fin material, in the titled mechanism provided with seal fins for adjusting the flow quantity of cooling air between the rotary body side and the stationary body side. CONSTITUTION:In the cooling air system of the gas turbine, cooling air 2 flowing on the front side of a first stage moving vane 1, is adjusted by a seal fin 5 mounted on a support ring 4 on the inner side of a first stage moving vane 10, and after cooling the vane root portion, cooling air 2 is causted to flow out to the gas path. In addition, cooling airs 6 and 7 flowing on the rear side of the first stage stationary vane 1 and the front side of the second stage moving vane 10 similar cool the root portions of the respective vanes, and then flow out to the gas path. In this case, a bimetal is used as a material for seal fins 5 and 9 provided in the support ring 4 and the second stage stationary vane diaphragm 8 is used, and changes gaps 12 between the vane root portions and seal rands 13 to constantly make optimum the flow quantity of cooling air in accordance with the temperature at the vane root portion.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas turbine provided with seal fins for adjusting the flow rate of cooling air between a rotating body side and a stationary body side,
In particular, the present invention relates to a mechanism that automatically adjusts the cooling air flow rate so as to maintain a constant temperature of parts by utilizing the temperature difference of the seal fins depending on the cooling air flow rate.

Conventional gas turbines have a structure in which the fluid flowing into the turbine is contained in a gas bath, and cooling air is flown in order to keep each component at a permissible temperature or lower. In particular, as the efficiency of recent gas turbines has increased, the temperature of the i-bin inlet fluid has tended to increase, making cooling air more important.

The rotor blade roots of the gas turbine rotating body are heavier for safety reasons, and the cooling air flow rate uses cycle air, which is designed to prevent backflow of combustion gas from occurring under any conditions. There is. In addition, the gas turbine is equipped with a protection device that constantly monitors the fluid temperature near the blade root and issues an alarm and shuts down if the temperature exceeds a set value.

In order to prevent the backflow of combustion gas to the rotor blade root and keep the temperature below an allowable value, it is necessary to keep the pressure of the cooling air near the blade root constant so that it always flows toward the gas path.

FIG. 1 shows a cooling air system for the rotor side blade root of a conventional gas turbine; this figure shows the cooling air system before and after the first and second stage rotor blades in the conventional gas turbine cooling air system. 1
Cooling air 2 flowing in front of the stage rotor blade 1 is adjusted by a seal fin 5 attached to a support ring 4 located inside the first stage stationary blade 3', cools the blade root, and then flows into the gas path part. Cooling air 6 flowing behind the first-stage rotor blade 1 passes through the second-stage stator blade 7, branches at the outlet of the second-stage stator blade diaphragm 8, is regulated by a seal fin 9 attached to the second-stage stator blade diaphragm 8, and flows into the gas path section. The cooling air 11 flowing in front of the second-stage rotor blade 10 is air that is branched from the cooling air 6 at the outlet of the second-stage stator blade diaphragm 8 . In order for the air flow shown in Fig. 1 to be stable at all times and under any conditions, the pressure difference before and after the seal fin 5.9 and the gap between the rotor blade seal land and the rotor blade seal land must be maintained so that the necessary amount of cooling air always flows. It is necessary to set the amount 12 at a certain ratio.

FIG. 2 shows the relationship between the pressure ratio before and after the seal fin and the seal fin gap when the cooling air flow rate is constant.

In conventional gas turbines, the gap amount 12 in FIG. Set the cooling air flow rate and pressure at each part so that combustion gas does not flow backwards even if the Once these relationships are set, if they cannot be changed and the temperature near the rotor blade root exceeds the set value for some reason during operation, the gas turbine will be stopped.

Additionally, the flow rate of cooling air may be set in advance to be relatively large so as to prevent the temperature from becoming too high, resulting in a large loss in terms of efficiency.

An object of the present invention is to provide a highly efficient and reliable gas turbine that maintains a constant temperature near the roots of rotor blades and always maintains the minimum required flow rate of cooling air.

With the aim of minimizing the flow rate of cooling air, which greatly affects the efficiency of gas turbines, we control the temperature near the roots of the rotor blades, which require the highest reliability in gas turbines, by adjusting the air flow rate for cooling the blade roots. This is done by automatically adjusting the seal fin gap amount. This automatic adjustment utilizes the characteristics of the bimetal used as the seal fin material.When the temperature near the blade root is high, the gap is increased to allow more cooling air to flow, and conversely, when the blade root temperature is low, the gap is increased. Squeeze the cooling air a little. By adopting this mechanism, the temperature near the blade root can always be kept constant.
Since the amount of cooling air can be kept to the minimum necessary, a highly reliable and highly efficient gas turbine can be achieved.

An embodiment of the present invention will be described below with reference to FIGS. 3(a) to 3(d). The structure of the gas turbine is the same as the conventional one, and the flow of cooling air is also almost the same as the system shown in FIG.

Here, only the front side of the first stage rotor blade will be described. Seal fins embedded in the support ring 2 are used to cool the air for cooling the first blade root of the first stage rotor blade, preventing combustion gas from flowing back into the casus. (a) The required flow rate of this cooling air will naturally vary depending on the operating conditions, such as during startup, no load, partial load, full load, etc. In conventional gas turbines, the gap between the seal fins and the flow rate of cooling air are set taking into account the worst of these operating conditions, and during normal operation, more air than is required flows through the turbine.

The present invention utilizes the fact that the temperature near the seal fin 3 changes depending on the amount of cooling air flow and the backflow of combustion gas, etc.
Bimetal is used as the material of the seal fin 3, and the gap 5 between the seal fin 3 and the seal land 4 is changed to adjust the flow rate of cooling and nitrogenizing air according to each operating state. (b) Set the initial gap amount to the minimum necessary value, taking into consideration the thermal elongation on the rotating body side, the centrifugal elongation, and the thermal elongation on the stationary body side. During operation, when the temperature of the rotating body or stationary body increases and the gap becomes smaller, the flow rate of cooling air is restricted and the specified amount no longer flows, the temperature of the seal fin 3 rises, and the seal fin 3 deforms in the direction of increasing the gap. It will settle down at a position where the temperature of the seal fin is balanced. On the contrary, when the temperature of the rotating body decreases and the gap becomes larger, such as during partial load, the cooling air flow rate increases, the temperature of the seal fin decreases, the gap decreases, and the temperature of the seal fin becomes balanced. It will settle down in position. ((C), (d)) If this mechanism is adopted, the air gap will be optimal under any operating condition.

The flow rate can be maintained, and a highly reliable and highly efficient gas turbine can be achieved. FIG. 4 shows the relationship between the gap amount and the air flow rate when the pressure ratio before and after the seal fin is constant. It will be proportional to the gap amount and air flow rate.

According to the present invention, the flow rate of cooling air at the root of the rotor blade can be set to the optimum amount between the required amount and the intermediate limit in any operating state, and a highly reliable and highly efficient gas turbine can be realized.

[Brief explanation of drawings]

Fig. 1 is a system diagram of cooling air at the root of a rotor blade in a conventional gas turbine, Fig. 2 is a diagram showing the relationship between the pressure ratio before and after the seal fin and the amount of gap when the flow rate is constant, and Fig. 3 (a). (bJ, (C), (') are partial sectional views of the cooling air flow rate adjustment mechanism of the present invention, and Figure 4 is a diagram of the relationship between the gap amount and air flow rate when the seal fin front and back pressure ratio is constant. 1...1st stage moving blade, 2'...support ring, 3'...
...Seal fin, 4'...Seal land, 5'...
・Second interval between eyes and referees

Claims (1)

[Claims] 1. In a gas turbine equipped with a seal fin between a rotating body side and a stationary body side for adjusting the cooling air flow rate, the automatic gas turbine cooling air flow rate is characterized in that a bimetal is used as the material of the seal fin. Adjustment mechanism.