JPH076406B2 - Desuperheater for gas turbine - Google Patents

Description

The present invention relates to a desuperheater that lowers the temperature of air that cools blades of a gas turbine.

(Prior Art) In a gas turbine, in order to improve its thermal efficiency and specific output, an increase in turbine inlet temperature is being pursued.

However, if the inlet temperature of the gas turbine is raised, the metal temperature of the turbine blade rises, which causes problems such as exceeding the heat resistant temperature of the constituent materials and shortening the life of the turbine blade, thus requiring cooling of the blade. Especially, since the first stage vanes of the high temperature turbine are exposed to high temperature, it is necessary to introduce a part of the air compressed by the compressor into the desuperheater and supply the cooled air to the gas turbine to cool the vanes. I have to.

As this type of desuperheater, conventionally, a heat exchanger cooled with air or water or a desuperheater for spraying water has been used.

FIG. 4 shows a configuration example of a turbine plant using a heat exchanger as a desuperheater, in which the air compressed by the compressor 1 is introduced into the combustor 3 together with the fuel supplied from the fuel pipe 2 and burned. Then, the high temperature and high pressure gas is introduced into the gas turbine 4 and is driven. On the other hand, a part of the air compressed by the compressor 1 is introduced into the heat exchanger 5 and cooled by heat exchange with water flowing in the pipe 6, and then the gas turbine 4
Is supplied as cooling air inside.

FIG. 5 shows an example in which sprayed water is used as the desuperheater, and the compressed air flowing through the desuperheater 7 is cooled by the cooling water sprayed from the tip nozzle of the pipe 8 opening to the desuperheater 7. To do.

(Problems to be Solved by the Invention) However, when air is cooled by the heat exchanger as shown in FIG. 4, the pressure damage of the air in the heat exchanger is large, and the pressure of the cooled air decreases. However, there is a drawback that the cooling performance of the blade is deteriorated.

Also, as shown in Fig. 5, the desuperheater that sprays water cannot eject water in the form of fine water droplets, so the water does not evaporate sufficiently in the air and remains as water droplets that separate in the gas turbine. The blades may be locally cooled too much to damage the blades, and more water than necessary will be sprayed, so this moisture enters the gas turbine and lowers the gas temperature, which reduces the thermal efficiency of the gas turbine. There was an inconvenience that it lowered.

[Structure of Invention]

(Means for Solving Problems) The desuperheater for a gas turbine of the present invention is provided with a cooling water pipe inside or outside a desuperheater duct, and a laval nozzle is provided at the tip of the cooling water pipe inside the desuperheater duct. Is provided, and the cooling water that has become saturated water or superheated steam by heat exchange with the high temperature air flowing in the desuperheater duct is sprayed from the Laval nozzle.

(Operation) In the gas turbine desuperheater of the present invention configured as described above, since water is sprayed as fine particles from the Laval nozzle, the compressed air flowing through the desuperheater is cooled to an appropriate temperature.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

In the embodiment shown in FIG. 1, a pipe 11 is arranged in the desuperheater duct 10 so as to be curved in a spiral shape or a hairpin shape. A Laval nozzle 12 is attached to the tip of the pipe 11 for spraying the water flowing therethrough as a fine flow. In addition,
In the figure, 13 indicates a support rod for fixing the pipe 11 or the Laval nozzle 12, and 14 indicates a cooling water pressure pump.

In the desuperheater of the present invention having such a configuration, the cooling water is pressurized by the pressurizing pump 14 and press-fitted into the pipe 11. Around this pipe, high-temperature compressed air is flowing in the desuperheater duct 10 as indicated by arrows A and B, and the heat is transmitted to the cooling water in the pipe through the pipe wall of the pipe 11, To heat. When this heat exchange is sufficiently performed, the cooling water becomes saturated water, and when it is further heated, a part thereof becomes superheated steam.

In other words, the length of the pipe 11 is selected so as to be in such a state, and fins for promoting heat exchange are attached to the surface of the pipe as needed.

In general, the air pressure extracted from a gas turbine compressor is
It is around 12ata and its temperature is about 350 ℃. Therefore
When cooling water is heated to 300 ° C, water of about 90 atm becomes saturated. When such a high-pressure saturated water, or a gas-liquid two-phase flow in which part of it becomes superheated steam, is jetted into the air from the Laval nozzle 12, decompression boiling occurs near the outlet of the Laval nozzle 12, and the diameter is about a few microns. It becomes an extremely small water drop. The minute water droplets easily evaporate in the air and cool the air flowing in the desuperheater duct.

FIG. 2 shows a modification of the gas turbine desuperheater of the present invention, in which the vicinity 10 'of the outlet end of the desuperheater duct 10 is narrowed in order to increase the flow velocity of the air flow around the Laval nozzle 12. Further, FIG. 3 shows the pipe 11 in close contact with the outer wall of the desuperheater duct 10 in a spiral shape, and the vicinity 11 ′ of its tip and the Laval nozzle 12 are located inside the desuperheater duct 10. Also in the case, the cooling water in the pipe 11 is heated by the hot air in the desuperheater duct that is transmitted through the outer wall of the desuperheater duct 10,
The saturated water or superheated steam is sprayed from the Laval nozzle 12.

It should be noted that the pipe 11 and the inner wall of the desuperheater duct 10 may be closely attached and arranged in a spiral shape.

〔The invention's effect〕

As described above, according to the present invention, the cooling water can be sprayed as fine water droplets into the desuperheater duct, so that the cooling air introduced into the gas turbine can be lowered to an appropriate temperature. Further, since the air can be cooled with a small amount of cooling water, the thermal efficiency of the gas turbine is maintained at a high level, and excessive water is not introduced into the turbine to damage the blades.

[Brief description of drawings]

1 to 3 are schematic views showing an embodiment of the present invention, and FIGS. 4 and 5 are system diagrams of a gas turbine equipped with a conventional desuperheater. 1 ... Compressor, 2 ... Fuel piping, 3 ... Combustor, 4 ...
Gas turbine, 5 ... Heat exchanger, 6 ... Piping, 7 ... Desuperheater, 10 ... Dehumidifier duct, 11 ... Piping, 12 ... Laval nozzle, 13 ... Support rod, 14 ... Addition Pressure pump.

Claims (4)

[Claims] 1. A cooling water pipe is provided inside or outside the desuperheater duct, and a Laval nozzle is provided at the tip of the cooling water pipe inside the desuperheater duct, so that the cooling air pipe and hot air flowing in the desuperheater duct are provided. A desuperheater for a gas turbine, characterized in that it is configured such that saturated water or cooling water that has become superheated steam by heat exchange is sprayed from the Laval nozzle. 2. The desuperheater for a gas turbine according to claim 1, wherein a pipe for guiding the cooling water to the Laval nozzle is provided in a curved shape in the desuperheater duct. 3. The gas turbine dehumidifier according to claim 1, wherein the outlet side of the desuperheater duct is throttled so as to increase the flow velocity of the air flow around the Laval nozzle. Warmer. 4. A gas turbine desuperheater according to claim 1, characterized in that a pipe for guiding the cooling water to the Laval nozzle is arranged in spiral contact with the inner and outer walls of the desuperheater duct. vessel.