JPH01106906A - Expansion turbine - Google Patents

Abstract

PURPOSE:To prevent the damage of a bearing part, by providing a means to calculate starting torque of the rotary body of a turbine and a control means to fully close a turbine inlet when the rotary body is not rotated even if starting torque exceeds a set value. CONSTITUTION:When, during the starting of an expansion turbine employing a tilting pat type dynamic pressure gas bearing, a turbine inlet valve 1 is gradually opened, at a point of time when turbine starting torque exceeds static friction torque of bearings 11a and 11b, a turbine is run. When a turbine is not run even when starting torque calculated by a computer 6 from measurements from pressure gauges 12 and 2 at turbine outlet and inlet, a thermometer 3 at a turbine inlet, and a pressure gauge 4 at the outlet of a nozzle 7 exceeds preset allowable starting torque, the turbine inlet valve 1 is closed. Allowable starting torque can be calculated from a preload and a static friction factor. The control system prevents the damage of a bearing part due to overspeed during starting and wear of the bearing part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an expansion turbine, and particularly to an expansion turbine suitable for using a hydrodynamic gas bearing.

[Conventional technology]

Conventionally, expansion turbine protection systems are generally equipped with the following:

(1) Overspeed of rotation (2) Abnormal shaft vibration (3) Abnormal bearing temperature (4) Low oil supply pressure or bearing gas pressure However, these protection systems do not prevent bearing wear in expansion turbines that use hydrodynamic gas bearings. No consideration was given to problems such as an increase in starting torque due to this, rapid acceleration of rotation during starting, and bearing damage.

Note that related devices of this type include, for example,
Examples include JP-A No. 51-147803, JP-A No. 61-110850, and JP-A No. 61-168756.

[Problem that the invention seeks to solve]

In a tilting pad type hydrodynamic gas journal bearing, when the rotating shaft is stationary, a preload is applied to the pad to force it into contact with the rotating shaft.

This applies a preload to ensure stable bearing performance when the rotating shaft rotates and a gas film is generated between the pad and the rotating shaft due to the wedge film effect.

Therefore, when rotating the rotating body, it will not rotate unless a force is applied as a starting torque to overcome the static frictional force of the journal bearing produced by this preload.

On the other hand, in a hydrodynamic pneumatic bearing, the rotating body always comes into contact with the pad surface of the journal bearing when starting and stopping, so this contact surface gradually wears out and the static friction force increases as the operation progresses.

When the static friction force of the journal bearing increases in this way, it is necessary to increase the starting torque, so the turbine inlet pressure must be increased accordingly.

However, when the turbine is started, if the turbine inlet pressure is high, the rotational speed increases in a state of rapid acceleration, and in some cases, overspeed may be instantaneously reached.

If such a situation occurs, there is a problem that the bearings and rotating body of the turbine will be burnt out and suffer significant damage.

An object of the present invention is to start the turbine by detecting that, in an expansion turbine using a tilting pad type hydrodynamic gas bearing, wear of the pad portion has progressed and the static friction force has increased beyond a specified value. The object of the present invention is to provide an expansion turbine that can stop operation and prevent major damage.

[Means for solving problems]

The above object is achieved by providing a means for calculating a starting torque when starting a rotating body, and a control means for fully closing a turbine inlet valve when the rotating body does not rotate even if the starting torque exceeds a set value. , achieved.

[For production]

The starting torque of the rotating body is calculated by the means for calculating the starting torque at the time of starting the rotating body, and if the starting torque is larger than a preset starting torque setting value by the control means, the turbine inlet valve is fully closed. As a result, the rotating body does not rotate at more than the set starting torque, so the rotating body does not over-rotate and damage the bearing.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

First, the configuration will be shown. A turbine inlet valve 1, an inlet pressure gauge 2, and an inlet thermometer 3 are provided on the turbine inlet line, a pressure gauge 4 is provided at the outlet of the turbine nozzle 7, a pressure gauge 12 is provided at the outlet of the rotor 8, and the rotation speed of the rotating shaft 9 is A tachometer 5 is provided for detection. Further, a computing unit 6 is provided which calculates the starting torque from the detected values of the pressure gauges 2.4 and 12, the temperature 3 and the tachometer 5, compares it with the allowable starting torque, and provides an operating signal to the inlet valve 1.

A rotor 8 and a brake impeller 10 are attached to both ends of a rotating shaft 9 of the turbine, and this rotating shaft 9 is supported by dynamic pressure type journal bearings 11a and 11b.

Next, the operation of the expansion turbine protection system configured as described above will be explained.

When starting the turbine, the turbine inlet valve 1 is gradually opened to increase the pressure in the turbine inlet line and increase the turbine starting torque. When the starting torque of the turbine becomes larger than the static friction torque of the journal bearings 11a and 11b (tilting pad type hydrodynamic bearings), the turbine rotates and an instruction is displayed on the tachometer 5.

However, in this starting operation, the starting torque is calculated in advance by the calculator 6 from the measured values of the pressure gauges 12 and 2 at the turbine inlet and outlet, the temperature gauge 3 at the turbine inlet, and the pressure gauge 4 at the outlet of the nozzle 7. A comparison is made with the allowable starting torque, and if the detected value of the tachometer 5 is not detected even if the starting torque is greater than the allowable starting torque, a signal is given to the turbine inlet valve 1 to close the turbine inlet valve 1.

Here, the torque TB acting on the turbine rotor is expressed by equation (1) according to the literature (Reported by the Institute of Industrial Science, University of Tokyo, published by Nagao Kenkigugi of Nirasial Gas Turbine).

TB =-(C1*cos cx*R1-(U2
-W2 cos 73 r) R2) --(1) Also, in this formula (1), (U2-W2 CosA r)
The R2(7) value is approximately 1/10 or less of the CI acosαm R1rl) value, and the torque TB is mainly due to cl
・It is shown that it is given by CO5α meeting R1.

Here, G: Processing fluid flow rate (variable) g: Gravitational acceleration (constant) C1: Nozzle outflow velocity (variable) α: Nozzle outflow angle (turbine eigenvalue) R1: Rotor outer radius (turbine eigenvalue) Therefore, the right side in equation (1) If we ignore the terms, the variables are G and C1.
, and the others can be considered as eigenvalues of each turbine. (However, the turbine outlet pressure is sufficiently lower than the nozzle outlet pressure.) Here, the processing fluid flow rate G is the same as the flow rate passing through the nozzle, and the nozzle passing flow rate GN is GN = AN xc,
PN -----------1-(3) Here AN:
Nozzle area (turbine specific value) C1: Nozzle outflow speed PN: Nozzle speed coefficient (0.9 to 0.!35).

Further, the nozzle outflow velocity C1 can be determined from the nozzle inlet pressure, outlet pressure, and inlet temperature. (Refer to Mechanical Engineering Benelan Revised 5th Edition Pi 1-63) Therefore, if you measure the nozzle inlet pressure = turbine inlet pressure P1, inlet temperature T1, and nozzle outlet pressure P2, and understand the turbine specific values in advance. The torque acting on the low torque can be calculated from equations (2) and (3).

On the other hand, the resistance torque due to an increase in the static friction force of the bearing can be calculated from the preload that forces the bearing and rotating shaft into contact and the static friction coefficient, so if the upper limit of the static friction coefficient is known in advance, Allowable starting torque can be calculated and set.

Therefore, this allowable starting torque and the above P,,T,.

The starting torque can be calculated from P2, and compared with the preset allowable starting torque, it is detected that the rotation speed is not detected even if the starting torque exceeds the allowable starting torque, and the turbine inlet valve is closed. It is possible to prevent the turbine from rotating at more than the starting torque.

According to this embodiment, since the turbine does not rotate at more than the allowable starting torque, it is possible to prevent the turbine from rapidly accelerating and rotating at overspeed at the time of starting.

Furthermore, it is possible to detect an abnormality in the bearing section before the wear of the bearing section progresses and the bearing section burns out, causing major damage to various parts of the rotating body. This also has the effect of making maintenance easier.

In addition to this example, under startup conditions of the turbine where only the inlet pressure changes and the turbine inlet temperature and outlet pressure are approximately constant, only the turbine inlet pressure is monitored and this pressure is The turbine inlet valve 1 may be fully closed when the rotation does not occur even if the rotation exceeds a set value.

〔Effect of the invention〕

According to the present invention, it is possible to stop the startup operation of the turbine by detecting that the wear of the bearing has progressed and the static friction force of the bearing has increased beyond a specified value, thereby preventing serious damage. effective.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an expansion turbine which is an embodiment of the present invention. 1------1 turbine inlet valve, 2-----one person pressure gauge, 3-----1 population thermometer, 4--------nozzle outlet pressure gauge, 5----- -One rotation needle, 6------One computing unit, 7---------Nozzle, 8---One rotor, 9---One rotation axis, 10--------- Brake impeller, 11a, llb ----- Journal bearing 1
2...Rotor Hiro Pressure 1↑I-111 Rogue Day--Rotating shaft

Claims (1)

[Claims] 1. In an expansion turbine that employs a tilting pad type hydrodynamic gas bearing that applies a preload to a journal bearing that supports a rotating body with a turbine impeller provided at the end of the rotating shaft,
The present invention is characterized in that it includes means for calculating a starting torque when starting the rotating body, and a control means for fully closing the turbine inlet valve when the rotating body does not rotate even if the starting torque exceeds a set value. expansion turbine.