Torque Converter & Hydraulic Ratchet System - 4th

INDUSTRIAL GAS TURBINE

Unit 304 – Starting Equipment

Topic:

4.2 – Torque Converter

4.4 – Hydraulic Ratchet System

Learning Aim and Objective

To Understand the function of the Torque Converter as a

starting device.

Aim:

At the end of the lesson, you should be able to:

Explain the function and the operation of torque converter.

Explain the purpose of a Hydraulic Ratchet System.

Objective:


Background of Torque Converter :

A Torque Converter is a modified

form of a Hydrodynamic Fluid.

Allows the Gas Turbine engine to

spin independently of the generator

or centrifugal compressor.


To provide a method and apparatus to start up Electric

Generator or Centrifugal Compressor.

To multiply torque when there is a substantial difference

between input and output rotational sped.

Improved starting method for starting Generator. Especially a

generator driven by a single shaft gas turbine machine, such

as used in Cogent plants.

Improved starting method for starting compressors.

Especially, if the compressor is driven by a single shaft gas

turbine machine (used in liquefied natural gas plants).

Function of Torque Converter:

Why used Torque Converter?

A specific problem with the single-shaft gas turbine is that

everything is connected mechanically on a single common shaft.

hence the starting device must start up not only the gas turbine

itself, but also the connected load. Everything must be started up

and accelerated simultaneously from rest continuously up to full

speed.

The added load produced by an electric generator (Co-Gen Plant)

in an unloaded state can be handled by a single-shaft gas turbine's

standard starting system, so they use torque converter just for

loading and unloading the electric generator anytime they want.

But not the inertia and aerodynamic loads associated with a large

centrifugal compressor (LNG plants). They use torque converter to

startup their Large Compressor.

Location?

For LNG plants, a compressor starting torque converter

(CSTC) located between the gas turbine output shaft and the

compressor input shaft.

For Co-Gen plants, it is located between the gas turbine

output shaft and the generator input shaft.

In normal torque converter, there are at

least 3 rotating elements:

Pumps

Turbine

Stator


Torque Converter Element:

Housing

Turbine output shaftLoad Coupling

Turbine

Stator

Pump

Stator output shaft


Input

ShaftOutput

Shaft

Torque

ConverterLock-up

Device

Guide

Vanes


Torque Converter Lock-up Device

Engage Disengage

Locking Device

How Torque Converter work?

As the pump spins, the fluid is flung to the outside and

creating Vacuum which draws more fluid at the centre.

Continue…


The fluid then enters the blades of the turbine from outside

which gave changes on the direction of the fluid before it exits

through the centre of the turbine.

This directional change of fluid makes the turbine to spin.

Continue…


Since the fluid exits the turbine moving an opposite direction

of the pump. This is why a stator is placed in between the

turbine and the pump, just to counter flow the output fluid flow

out of the turbine .


Stall – The prime mover apply power to the pump but the

turbine is not rotating. During this period, it produce maximum

torque multiplication (called Stall Ratio).

Acceleration – During this period, the load is accelerating

but there are still having a relatively large difference between

pump and turbine speed. Under this condition, the converter

will produce torque multiplication that is less than what could

be achieved under stall conditions.

Coupling – once in this phase, the fluid will be in reverse

direction and now rotate in the direction of the pump and

turbine.

Three stage of Operation:

4.3 – Hydraulic Ratchet System

It is used as rotor-turning device, the purpose are:

To cool down the Rotor after turbine operation (periodic).

To assists the diesel or cranking motor in starting the Gas

Turbine.

To partially turn the rotor in 3-minute stroking intervals until it

complete 1 revolution for every half an hour. This to prevent

sagging happened to the rotor.

To provide additional torque to augment the power delivered

through the torque converter during the starting up from cold.

To assists in overcoming the “breakaway torque” demand of

the turbine rotor.

Used during maintenance outstages and inspections.

Recap

Explain the function and the operation of torque

converter.

Explain the purpose of a Hydraulic Ratchet

System.

Overview of Next Lesson…

Section „E‟ – Cooling System

Topic: Cooling air system & sealing air

Thank you for your Attention


Operation of Torque Converter :

• The hydraulic fluid for the torque converter supplied by the

gas turbine lube-oil system.

• During the startup operation of the gas turbine, the torque

converter hydraulic fluid is drained and the mechanical lock-

up device is disengaged.

• When the gas turbine has reached rated speed, the torque

converter guide vanes opened to filledup the torque converter

with hydraulic fluid.

• Once the torque converter full with hydraulic oil, the speed of

the generator or large compressor start to increase until it has

the same speed as the input shaft speed.

Continue…


Operation of Torque Converter :

•Once the two speeds has synchronous, the lock-up device will

be engaged and the torque converter hydraulic oil drained by

shutting up the guide vanes.

•In this condition, the power is transmitted only mechanically

with a very high efficiency.

Torque Converter & Hydraulic Ratchet System - 4th

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