JPH0316481B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an expansion turbine, and particularly to a thrust control device for a high-pressure expansion turbine that tends to undergo thrust fluctuations during operation.

[Conventional technology]

Expansion turbines used for generating refrigeration in air separation devices and the like are used under a wide range of operating conditions from normal temperature conditions to extremely low temperature conditions in plants. Therefore, since the pressure and temperature at the entrance and exit of the expansion turbine change under each operating condition, the thrust load acting on the rotating bodies (impeller, rotating shaft, etc.) of the expansion turbine also changes. Therefore, it is necessary to incorporate a thrust bearing into the expansion turbine that can sufficiently support this thrust load.

Generally, in an expansion turbine having a full-shrouded impeller, the axial thrust acting on the rotating body is calculated from the pressure on the front and back surfaces of the impeller and the ratio of the pressure-receiving area on which this pressure acts, as shown in FIG. (Mechanical Engineering Handbook Revised 5th Edition 9-44) F=P ₁ ×A ₁ ×P ₂ ×A ₂ −P ₃ ×A ₃ −P ₄ ×A ₄ …(1) Here, F = Thrust acting on the rotating shaft P ₁ = Impeller inlet pressure P ₂ = Impeller outlet pressure P ₃ , P ₄ = Impeller back pressure A ₁ to _{A 4} = Pressure receiving area where pressures P ₁ to P ₄ act Pressure receiving area A ₁ to _{A 4} depends on the impeller shape. However, the pressures of P ₁ and P ₄ vary depending on the operating conditions of the expansion turbine. Therefore, in an expansion turbine that processes high-pressure process gas, there are operating conditions ranging from low pressure to high pressure, so the shaft thrust changes greatly depending on the operating conditions.

The magnitude of the axial thrust generated in an expansion turbine is determined by the difference between the impeller back pressure and front pressure, as shown by equation (1) above. This pressure difference fluctuates depending on operating conditions, and this fluctuation value is particularly large in expansion turbines that process process gas at high pressure, making it necessary to increase the load capacity of the thrust bearing. In addition, related devices of this type include, for example, Japanese Patent Publication No. 46-3209 and Utility Model Publication No. 59-1989.
Examples include No. 127601 and Utility Model Publication No. 55-102005.

[Problem that the invention seeks to solve]

The above-mentioned conventional technology requires a thrust bearing with a high load capacity, and therefore has disadvantages such as increased bearing loss, increased amount of bearing lubricating oil, and, in the power recovery type expansion turbine, a decrease in the amount of recovered power.

An object of the present invention is to provide a thrust control device for an expansion turbine that maintains the thrust acting on the rotating shaft within a certain range under any operating conditions.

[Means for solving problems]

The above object is achieved by sensing the temperature of the thrust bearing and controlling the pressure on the back side of the impeller.

[Effect]

By controlling the pressure behind the impeller,
The shaft thrust generated by the impeller can be maintained within a certain range, and the load capacity of the thrust bearing can be reduced.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. In the figure, the process gas in the scroll 1 passes through a nozzle 2, expands adiabatically, becomes a jet gas, enters an impeller 3, rotates the impeller 3, and then flows to a differential user 4. A labyrinth 5 is provided at the front outlet of the impeller 3 to prevent a shot path of the process gas. Further, a labyrinth 6 is provided on the outer periphery of the back surface of the impeller 3, and a labyrinth 7 is provided on the inner periphery portion, and a portion surrounded by the labyrinths 6 and 7 forms a back pressure chamber 8. The back pressure chamber 8, the scroll 1 section, and the impeller 3 outlet section are connected through lines 14 and 15 having control valves 10 and 11 disposed therebetween, respectively. Further, the thrust bearing 16 is provided with thermometers 12 and 13 on the load side and the anti-load side, respectively, to measure the temperature of the thrust bearing metal, and the control valves 10 and 11 are actuated by signals from the thermometers 12 and 13. The operating conditions are such that the control valve 11 opens when the temperature of the thermometer 12 reaches the upper limit, and the control valve 10 opens when the thermometer 13 operates. When the control valve 11 is opened by a signal from the thermometer 12, the gas in the back pressure chamber 8 is sent to the outlet of the impeller 3 through the line 15, and when the control valve 10 is opened by a signal from the thermometer 13, Since the gas from the scroll 1 section flows into the back pressure chamber 8 through the line 14, the axial thrust generated at the impeller 3 section can be maintained within a certain range.

The usage limit of a thrust bearing can generally be determined by the temperature of the bearing metal, and when a high load thrust acts on the thrust bearing, loss in the bearing increases and the temperature of the bearing metal rises. This bearing temperature limit is a value specific to each bearing, determined by the material of the bearing metal, the type of circulating lubricant, etc. Therefore, by understanding the operating temperature limit of the bearing metal in advance and setting the upper limit of the thermometers 12 and 13 so as not to exceed this operating temperature limit, any thrust bearing can be incorporated into the expansion turbine. In addition, the thrust load can be controlled within a certain range.

〔Effect of the invention〕

According to the present invention, since the load capacity of the thrust bearing can be set arbitrarily, a thrust bearing suitable for an expansion turbine can be designed, which is effective in making the thrust bearing more compact, reducing bearing loss, and reducing the amount of bearing lubrication. There is. Furthermore, the power recovery type expansion turbine has the effect of increasing the amount of recovered electric power.

[Brief explanation of drawings]

FIG. 1 is an explanatory view showing a cross section of an impeller and the types of pressures acting on the impeller, and FIG. 2 is a cross-sectional view showing an embodiment of the present invention. 1...Scroll, 2...Nozzle, 3...Impeller, 4...Diff user, 5-7...Labyrinth, 8...Back pressure chamber, 10, 11...Control valve, 12, 13...Temperature Total, 14,15
...Line, 16...Thrust bearing.

Claims (1)

[Claims] 1 A rotating shaft supported by a thrust bearing,
In an expansion turbine equipped with an impeller provided at the end of the rotating shaft and a nozzle for supplying process gas to the impeller from a scroll section, a back pressure chamber is provided on the back surface of the impeller, and the back pressure chamber and the scroll section are connected to each other. and an impeller outlet via control valves, and a thermometer for detecting the temperature of the thrust bearing and operating the control valve.