Mitsubishi Heavy Industries, Ltd.Technical Review Vol. 41 No. 3 (Jun. 2004)

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25 MW Gas Turbine MFT-8 forCompressor Driver

Recently, energy conversion from petroleum to natural gas is being promoted, and plant constructions of gaspipe lines and gas fields are increasing globally. In plants having 25 MW class compressors, gas turbines are oftenused as compressor drivers. Against this background, Mitsubishi Heavy Industries, Ltd. (MHI) has modified its 25MW gas turbine MFT-8, highly noted for marine propulsion and power generation use, for compressor driver, andevaluated the performance and reliability of the equipment in shop load test. As a result, the installation space ofgas turbine is reduced by about 40% as compared with gas turbines of the same class of other manufacturers. Inshop actual loading test, reliability of the equipment is confirmed, and at the rated load, the same high thermalefficiency as that of the original MFT-8 is confirmed, while in addition at partial load, sufficient practical perfor-mance is observed.

1. Introduction1. Introduction1. Introduction1. Introduction1. Introduction

Recently, as energy conversion from petroleum tonatural gas is being promoted, plant constructions of gaspipe lines and gas fields have been increasing globally.In plants having 25 MW class compressors, gas turbinesare often used as drivers.

MHI's 25 MW gas turbine MFT-8, which has beenhighly evaluated for marine propulsion and power gen-eration use, has been newly modified for compressordriver, and its performance and reliability have beenevaluated in shop load test.

2. Modification for compressor driver2. Modification for compressor driver2. Modification for compressor driver2. Modification for compressor driver2. Modification for compressor driver

Fig. 1Fig. 1Fig. 1Fig. 1Fig. 1 is a cross section of the modified gas turbineMFT-8 for compressor driver. This gas turbine is com-posed of a gas generator GG8 based on the aircraft engineof Pratt & Whitney Power Systems (PWPS), and a powerturbine of MHI.

TTTTTable 1able 1able 1able 1able 1 shows the main characteristics of gas turbineMFT-8 for compressor driver. While maintaining the highthermal efficiency of the original MFT-8, it has been op-timally modified for compressor driver.

To be applicable to long-term continuous operation,which is an essential point as gas turbine for compres-sor driver, parts of the structure have been simplifiedfrom the original MFT-8 which has been developed be-cause of the necessity for reduction of weight and quickstarting as a marine propulsion engine.

Gas generator (GG 8)

Power turbine

Fig. 1 Cross section of compressor driver MFT-8

Exhaust

Inlet

26 800*

38.7*

3 333 (70%) - 5 000 (105%)

ISO-VG 32 (Mineral oil)

L 9.9 x W3.2 x H 3.5

Table 1 Specifications of MFT-8 for compressor driver

Specifications

Type Simple cycle 3-shaft

Output (kW)

Thermal efficiency (%)

Operating range (min-1)

Fuel type Natural gas fuel

Power turbine lubricating oil

Structure

Gas generator

GG 8

Compressor

Combustor

Turbine

Low pressure, axial flow, 8 stages

High pressure, axial flow, 7 stages

Cannular, 9 cans

High pressure, axial flow, 1 stage

Low pressure, axial flow, 2 stages

Axial flow, 3 stagesPower turbine (PT)

Bearing typeGG8: ball-and-roller

PT: tilting pad bearing

Package dimensions (m)

Rotating direction Clockwise (view from compressor side)

* Values in ISO standard atmospheric condition, using gas fuel, without inlet and exhaust loss, at shaft end.

SATOSHI HATA*1

HIROSHI FUKUI*1

MASAHIRO KOBAYASHI*1

OSAMU ISUMI*1

*1 Hiroshima Machinery Works

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Mitsubishi Heavy Industries, Ltd.Technical Review Vol. 41 No. 3 (Jun. 2004)

Principal changes are shown in Fig. 2Fig. 2Fig. 2Fig. 2Fig. 2 and Fig. 3Fig. 3Fig. 3Fig. 3Fig. 3.2.1 Power turbine2.1 Power turbine2.1 Power turbine2.1 Power turbine2.1 Power turbineThe power turbine of the original MFT-8 uses ball-

and-roller bearings, and expensive synthetic oil is usedas lubricating oil. For the compressor driver, the bear-ings of the power turbine are changed to tilting padbearings, and mineral oil is used for lubrication, thusreducing the running cost.

As a result of the change of bearing type of the powerturbine, the lubricating oil drain temperature is loweredby about 50oC. The thermal stress generated in the ex-haust frame around the bearing was tested by unsteadyFEM analysis as shown in Fig. 4Fig. 4Fig. 4Fig. 4Fig. 4, and the reliability wasverified.

In the stress concentrated portion of bearing sup-port , i ts s tress level was low, and i t has beenconfirmed that there is no problem in low cycle fa-tigue strength.

2.2 Auxiliary equipment2.2 Auxiliary equipment2.2 Auxiliary equipment2.2 Auxiliary equipment2.2 Auxiliary equipmentMajor changes in the gas turbine are as follows.

(1) Change of control methodFig. 5Fig. 5Fig. 5Fig. 5Fig. 5 shows a gas turbine operation screen, and

FigFigFigFigFig. . . . . 66666 shows an monitoring screen for the gas turbineand compressor.

Fig. 2 Improvements to power turbine

Power turbine shaft(Hollow shaft Solid shaft)

Gas flow

Journal and thrust bearings (Ball-and roller Tilting pad design)

Fig. 3 Improvements to auxiliary equipment

Added guide rail for maintenance Control devices

Re-arrangement of piping route and auxiliary equipment

Inlet

Exhaust

Fig. 4 Unsteady thermal stress analysis

Power turbine casing

Gas flow

Stress concentrationportion

Bearing support

High

Low

Str

ess

leve

l

MFT-8 Start & Stop button

Fig. 5 MFT-8 control touch panel

Fig. 6 Monitoring screen for operation condition of MFT-8 gas turbine and compressor

Mitsubishi Heavy Industries, Ltd.Technical Review Vol. 41 No. 3 (Jun. 2004)

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As the control device of gas generator of PWPS,Micronet of Woodward is used, while the PLC of Allen-Bradley is used as the control device of the powerturbine of MHI.

Further, by automating starting of the gas turbinemain body and starting of the auxiliary machine, ac-celeration up to 70% of power turbine rotating speed(lowest speed in operation range 3 333 min-1) is real-ized in a single action. In deceleration, a function isprovided for selecting the step-down method automati-cally depending on the cause of stop, and this isautomated including stopping of auxiliary machine.

(2) improvement to the enclosure structureMaintenance rails are provided in the enclosure,

the engine can be removed without disassembly theenclosure, and easy maintenance is realized.

3. Comparison with other manufacturers3. Comparison with other manufacturers3. Comparison with other manufacturers3. Comparison with other manufacturers3. Comparison with other manufacturers

Fig. 7Fig. 7Fig. 7Fig. 7Fig. 7 shows the example of the typical arrangementof compressor train with Mitsubishi Advanced Compres-sor (MAC) and MFT-8 for compressor driver, and TTTTTablablablablableeeee 22222shows a comparison of gas turbine package dimensionsof the same class from other manufacturers.

The package is made compact by adjusting the pipingroute and equipment layout, and the package installa-

9 5009 9005 700

1200

06

400

320

0

GL

Fig. 7 Package arrangement of MFT-8

Oil console (for power turbine and compressor) Oil cooler

Fire extinguishing equipment

Inlet air filter

Oil console (for gas generator)

Inlet air silencer

Ventilation filter

Exhaust silencer

Cooler

MFT-8 gas turbine

Compressor

Ventilation damper

Ventilation fan

tion area is reduced by about 40% as compared with othermanufacturers.

4. Load and performance test4. Load and performance test4. Load and performance test4. Load and performance test4. Load and performance test

A trial machine of MFT-8 for compressor driver wasfabricated in accordance with these changes and modifi-cations, and a shop load test was conducted for thepurpose of evaluating the reliability and performance ofthe equipment.

Fig. 8Fig. 8Fig. 8Fig. 8Fig. 8 shows an outline of the load test facility. A wa-ter dynamometer was used as the load device.

Fig. 8 Outline of test equipment for MFT-8

Exhaust duct and silencer Ventilation duct

and silencer

Inlet air duct and silencer

Ventilation fan

Water dynamometer

Oil console for Oil console for GGGG8

Oil console for GG 8

32 m2 52 m2 51m2

W=

3.2

W=

3.4

W=

4.0

L=9.9 L=15.3 L=12.8

Table 2 Comparison of gas turbine package dimensions(Unit: m)

MHI (MFT-8) Manufacturer A Manufacturer B

Installation area

Mitsubishi Heavy Industries, Ltd.Technical Review Vol. 41 No. 3 (Jun. 2004)

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To confirm the reliability of the improved points ofthe power turbine, about 100 points were measured andthe data were collected in real time.

Fig. 9Fig. 9Fig. 9Fig. 9Fig. 9 shows the results of measurement of bearingmetal temperature and shaft vibration at high load withpower turbine 100% rotating speed. The metal tempera-tures of thrust bearings and journal bearings at ratedload were, respectively, about 97oC and about 75oC, whichfall within design allowable values, and reliability wasconfirmed. Shaft vibration at rated load was about 30umP-P, which was also within design allowable values.At other points, measurements were normal, which re-liability of the equipment was verified.

Fig. 10Fig. 10Fig. 10Fig. 10Fig. 10 shows the results of measurement of perfor-mance. It was confirmed that performances at the ratedpoint and partial load were as planned. Thus, at the ratedload, the high thermal efficiency of the original MFT-8is maintained, and at partial load, sufficient practicalperformance could be confirmed.

5. Conclusions5. Conclusions5. Conclusions5. Conclusions5. Conclusions

MHI's 25 MW gas turbine MFT-8, in widespread usefor marine propulsion and power generation purposes,has been modified for compressor driver.

The controllability and maintainability have beenimproved accordingly, and the installation space ofgas turbine is reduced by about 40% as compared withgas turbines of the same class made by other manu-facturers.

Reliability of the modified MFT-8 has been confirmedin shop load test. It was verified that the modified MFT-8 has the same high thermal efficiency as the originalMFT-8 at rated load, and has sufficient practical perfor-mance at partial load.

In future, the product will be brought to the gas fieldmarket as a total package of Mitsubishi Advanced Com-pressor (MAC) and MFT-8 gas turbine.

#2 journal bearing metal temp.

20 000 21000 22 000 23 000 24 000 25 000

100

90

80

70

60

50

40

30

20

10

0

100

95

90

85

80

75

70

65

60

55

50

Fig. 9 Measurement results of power turbine bearing metal temperature and shaft vibration

Pow

er tu

rbin

e be

arin

g m

etal

tem

p. (

o C)

Power turbine shaft end output (kW)

Pow

er tu

rbin

e sh

aft v

ibra

tion

At 100% power turbine speed

Active side thrust bearing metal temp.

#1 journal bearing metal temp.

Inactive side thrust bearing metal temp.

Power turbine shaft vibration

40

38

36

34

32

30

28

26

24

22

2015 000 20 000 25 000

(MCR: 5 000 rpm)

*Test condition

Fig. 10 Measurement results of power turbine performance

The

rmal

effi

cien

cy (

%)

Power turbine shaft end output (kW)

Expected performance curve in ISO condition at100% speed (100% rotating speed: 4 762 rpm)

Expected performance curve in ISO condition at maximum continuous rotation (MCR)

Measurement points

Test condition* : Expected performance curve in 100% speed

(100% rotating speed: 4 762 rpm)

Ambient temperature: 10oCAtmospheric pressure: 101.90 kPaInlet loss: 90 mmAqExhaust loss: 160 mmAq

Satoshi Hata Hiroshi Fukui Masahiro Kobayashi Osamu Isumi