a 2500 hp addition to the ruston range

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only it thepapfit is pubfishe<l(n a{i;jj8M.EJ01:1in<3I or.ff6(Jeedif!g$,. Rele.ased for. generlitlPtJ.blication uponpresentation, Fyll credit should be given to ASME, the. Technical Division, antj the author(s). ·

A 2500 HP Addition to the Ruston Range

P. M. ANDRONOWSKI

Product Manager, Current Engines, Ruston Gas Turbines Ltd. Lincoln, England

This paper describes the newly introduced Ruston TA2500 gas turbine. The design is based on that of the well proven TA 1750 and retains its outstanding features of reliability, long life, and ease of maintenance. Component efficiencies have been improved to increase the overall thermal performance and the Ruston designed solid-state control system with its Rustronic solid-state governor has been incorporated to give greater operating flexibility. Other changes include a compressor driven auxiliary gearbox which obviates the necessity for motor driven auxiliary pumps and a new design of frame similar to that of the Ruston TB5000 gas turbine.

Contributed by the Gas Turbine Division of The American Society of Mechanical Engineers for presentation at the Gas Turbine Conference & Exhibit & Solar Energy Conference, San Diego, Calif., March 12-15, 1979. Manuscript received at ASME Headquarters January 22, 1979.

Copies will be available until December l, 1979.

UNITED ENGINEERING CENTER, 345 EAST 47th STREET, NEW YORK, N.Y. 10017

Copyright © 1979 by ASME

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A2500 HP Addition to the Ruston Range

P. M. ANDRONOWSKI

INTRODUCTION

In the early 1950's the author's company introduced into commercial service an industrial gas turbine with a power output or 1260 bhp, the Huston type TA. Development of this engine had, by 1964, increased its output to 1620 bhp and with further development and the introduction of new blade material it was released, in 1970, with an ISO rating of 1875 bhp. Designated the TA 1750 it is still in current production.

The continuing demand for this highly reliable gas turbine led to a study being initiated to look into the possibility of developing an engine of 2500 bhp based on the successful TA 1750 design. This study was begun early in 1977 and by the encl of the year the necessary design and development work had been completed and the feasibility of producing such an engine was confirmed. In the early part of the fol lowing year, 1978, the engineering o I' the peripheral equipment and the packaging of the turbine was undertaken.

The introduction to the Ruston range of a Lype TA gas turbine, vii th an ISO ra l:i ng of 2500 bhp was announced in October 1978. Designated the type TA 2500, it is based on the proven design of the earlier Lype TA machines and embodies the same characteristics of reliability and long periods between inspection and overhaul as its predecessors.

DESIGN PHILOSOPHY

The main design criteria for the design and development of an engine of 2500 bhp, based on the TA 1750 design, can be summarised as follows:

2

a)

b)

c)

cl)

The power of 2500 bhp aL ISO conditions was to be obtained by increasing component ef'l'iciencies rather than firing Lemperaturc or gas generator speed, thus ensuring the engine retained Lhe traditional long life charactcri�tics of the TA gas turbine.

Mechanical changes were to be oi· such a nature as to avoid the alLcraLion of' the mechanical properties of the TA 1750 engine e.g. critical speed, temperature and stresH levels, thus maintaining the es Labl i oohed rncclwni cal reliability of the TA engine.

All the major componcn Lc3 were Lo remain unaltered to si mp Li fy the introduction of the eng-ine in Lo proclucLion.

Controls and packaging were to follow Lhe well defined syc3tcms in use on the liuc3 Lon TB 5000 ga�:> turb j ne .

The following will show how cloc,;ely the design crj Lcrin wns in fact met in prncticP.

THEHWlUYNAMTC

Dc;-:>i_gn investiGation into component effic] encies soon confirm<·d that U1e TA 17'50 cornprpr;sor, due Lo previous uprating;-:>, was worki nr; in c-u1 �:ll'(:a far removed from i Ls high erfi c i ency pL-1Lc,au and in the region of' fast decreasing efficiency. Fig.l demonstrates this point. As can be observed, each successive uprating or the original design, resulted in a fall of compressor efficiency. [n, order to produce the mass flow and pressure required to give the currently rated output of the TA 1750, the


� ;:

5 ·0

4·5'

4·0

0 3·5 'fil " � 3·0

f a. 2·5

M Air Mass Flow lb/s P Absolute Pressure lbf/in' abs T Absolute Temperature °K N Compressor Speed rev/min

'JP =��!�:�i�c�:!�i�l��es(!)and@ ISO DESIGN POINT TA1750 TA1500

TA

1-0��-�-�--�-�-�-�--�-�-�-�--�-10 12 1 4 IB IB W U H � � W U M

Non·dimensional Air Ma s s Flow Mff1 P1

Fig.l.TA 1750 Compressor Characteristic

compressor has to run at a speed far away from the design point.

One way to correct this situation would have been to alter the compressor passage and blade angles to bring the high efficiency plateau within the run-ning speed. To do this however would have involved a major design change and was impractical within the set time limit and would have been outside the desired design criteria. Further design investigation revealed that "O" staging of the compressor and some increase in the compressor inlet area, would bring about the desired result.

This was achieved by arranging for the nondimensional air mass flow and speed at entry to the compressor second stage, to be the same as that which applied at the design point of the original TA machine. Thus the second and remaining stages of the compressor become matched and operate at the efficiency of the original. design.

In che event it was decided to modify the existing first stage blading as well as adding the "O" stage, to give a better distribution of blade loading and a smoother flow area variation.

The non-dimensional parameters at entry to the compressor second stage are:-

Original TA design

TA 2500 design

M/T p

23.47

23.42

N jT

652. 54

652.47

As can be seen the matching obtained for the TA 2500 design is very close to the original TA design.

The "0" and first stage temperature rise is 15�0c per stage as compared to approximately 13°C per stage for the remaining stages which were not altered. Otherwise the blades follow the original TA design philosophy namely free vortex, C4 profile and a low diffusion factor (. 49) Ref.l.

The compressor inlet area was increased by 18.8%. � shows the predicted compressor characteristic for the TA 2500 compressor. The gas generator speed remains unaltered but the compressor efficiency is increased by 3% to

5·0

4 ·5

� 4·0 :t' ·� 3·5 " f � 3·0 � ..

2· 5

2·0

M Air Maas Flow lb/s P Absolute Pressure lbf/in' abs T Absolute Temperature °K N Compressor Speed rov/min

l]P :��::1�c�:!�i:1��es(Dand @

EQUILIBRIUM RUNNING LINE

1 '0L_,�0--1L2- �14--1L6 -�18--2L0 -�2 2--2L4-�26--2L8-�JQ--JL2_� 34-

Non·djmenSiOnal Air Mass Flow M.ff1 P1

Fig.2. TA 2500 Compressor Characteristic

85/86% from the 14 axial stages. A mass flow increase of 12% gives a compressor mass flow of 28 lb per sec. and a pressure ratio of approximately 5:1, an increase of 13.6%

In respect of the compressor and power turbine, two courses of action were considered necessary.

a) Compressor Turbine

It was noted that as the firing temperature was raised for uprating purposes, the compressor turbine blade tip clearance increased. This is due to the form of construction used for the TA engine where the stator is located in the outer casing and as the temperature of the casing rises, it expands radially outward and carries the stator with it. The movement is compensated by the stator expanding radially inward but nevertheless as the firing temperature is raised the blade tip clearance does increase.

The stator casing is cooled by air; flowing in the same direction as the gas, it also cools the centre section of the engine and in the TA 1750 it is therefore fairly warm before it enters the stator casing. To correct this on the TA 2500 engine the cooling air is first supplied to the stator casing, i.e. the flow of the air is reversed.

ln order to further reduce the casing temperature, a suspected recirculation of air within the stator was eliminated by suitably blocking the suspected passages. The expected efficiency gain hecdme in practice of the order of 1% to 2%.

b) Power Turbine

Since it was considered desirable not t.o change the gearbox and output shaft speeds on each of the

previous occasions the rating was increased, the speed of the power turbine remained constant. The additional power therefore was obtained by an increase in the turbine blade loading, i.e. an increase of stage heat drop (6.H) and the power turbine operated off its design point and at a lower efficiency. Any further increase in power without a change in power turbine speed would have brought about an even lower efficiency. For these reasons the power turbine speed was increased from 6000 to 7950 rev/min for the TA 2500 engine.

3


4

1.0 .9 .8

c .7 "' ·;;; � ,,

.3 .2

Original TA Design Point and TA 2500 Design Point at 7950 r.p.m. µe = 1.696

""'-

pe = gJ.6.H Where AH =Stage Heat Drop based on Actual I/ p UR2 'Ip design= 0.907

q p = Actual Polytropic Efficiency UR= Blade Root Speed ft/s

.1 0o'---�-'-��2��3��-4��-5��6��7��-'-

8 Blade Loading. /le. based on actual P.T.'J p

Fig.3. Poljtropic efficiency V. Blade loading TA power turbine

� shows that the blade loading factor reverted to its original design value and that the efficiency of the TA 2500 power turbine is some 3 -4% higher than that of the TA 1750 engine.

It should also be noted, though it can be deduced from the above, that no aerodynamic changes have been made to either the power or compressor turbines.

In addition to the changes described so far it was decided to increase the firing temperature by J5°C and it was then predicted that a power of 250C bhp ISO could be obtained.

A prototype TA 2500 engine was built and extensively tested; �gives the performance lines for the engine with the line for the TA 1750 given for comparison. As can be seen the prototype TA 2500 engine gave a power in excess of 2500 bhp at 840°c (1113°K); in fact in the region of 2580 bhp. The rapid deterioration in the performance of the TA 1750 engine at the higher temperature is clearly shown, while the TA 2500 performance remains constant. This is confirmation that at higher powers the efficiency of the TA 2500 compressor is maintained.

9

1150

1100

1050

� 1000 • = E 950 I-

900

850

8000 500 1000 1500 2000 2500 Zero Loss Power (HP)

Fig.4. Zero loss Power V Tmax TA1750 and TA2500

The TA 2500 prototype test results confirmed the predicted performance and showed that the power .increase above the TA 1750 rating is approximately attributable to:-

a)

b)

improved component efficiency and air mass - 650 bhp

the increase in cycle temperature - 100 bhp

The zero loss thermal efficiency rose from 17.6% for the TA 1750 to 21.3% for the TA 2500.

Table 1 compares the performance of the two machines.

MECHANICAL DESIGN

Fig. 5 shows the type TA gas turbine with the large� combustion chamber and air transfer duct which is a feature of the engine.

As previously mentioned one of the criteria for the design of the TA 2500 was to make as few changes as possible to the major components of the TA 1750. In fact it has been possible to leave the engine externally unaltered except for cooling air piping.

TABLE 1 Full Load Performance at ISO Conditions

Compressor Pressure Ratio

Compressor Polytropic effy

Compressor Speed

Compressor Mass Flow

Firing Temperature

Compressor Turbine Pressure Ratio

Compressor Turbine Polytropic effy

Power Turbine Pressure Ratio

Power Turbine Polytropic effy

Power Turbine Speed

Power Turbine Loading Coefficient

Overall Thermal effy

TA1750

4,3 8 2"/o 12100 r.p.m.

25 lb/s

825°c 2.360 80% 1. 762 85.5% 6000

2.629 17.6%

TA2500

4.89 85.6% 11900 r.p.m.

28 lb/s

840°C

2.398 81.5% 1.977 89"/o 7950 1.696 21.3%


It

l

Fig. 5. The Ruston TA 1150 gas turbine

Internally four areas have been modified: -

1) Gas Generator

An additional stage ("0" stage) of blades has been added to the front of the compressor. � shows how this row of blades has been located on the upstream face of the stubshaft. This form of construction does not change the compressor shaft length and the compressor bearing positions are therefore unchanged. Since the additional weight of the blades is close to a bearing the change in critical speed is negligble.

Compressor speed has not changed and the gas generator stresses remain unaltered. The firing temperature having been increased by 15°C only, the general temperature levels through the engine have altered only marginally.

The first stage compressor turbine stator blades of the TA 1750 are made of IN 939 and Lhe second stage stator and all rotor blades of IN 738. These materials were chosen for their high corrosion resistance and have mechanical properties well in excess of those required, so that changes in material for the TA 2500 were deemed not to be necessary to maintain the creep life of 100,000 hours.

Fig. 6. Part section of compressor inlet end showing zero stage mechanical construction.

Combustion Chamber

The combustion chamber required some design changes to deal with the higher output. Modifications were made to the combustion chamber flame tube; a series of small holes spaced round the periphery of the t11be being adopted in place of the single large entry port on the TA 1750. Figs 7 and 8 show these differencies.

Improved combustion efficiency is demonstrated by a shorter flame, and a more uniform temperature or the flame tube of between 500-600°C. This is less than the flame tube metal temperatures of the TA 1750 and therefore no materi;1l change 1·1as required.

3) Compressor Turbine () Lator

This component remains unchanged except for the introduction of a contraflo\'I cooling air arrangement in place of a parallel flow arrangement used on the TA 1750. Thermal insulation of the stator casing by the use of internal lagging has also been improved. These changes give better control of blade tip clearances, \'/hi ch depend in part on stator e·xpansion, and hence improved turbine efficiency.

The speed of the power turbine has been raised from 6000 to 7950 rev/min to optimise blade loading and improve efficiency; this increase brings the blade tip peripheral speed to 900 ft/sec. The stress levels in the power turbine rotor have increased and are nov1 similar to those aprily ing to the compressor turbine rotor.

At the lov,er speed of 6000 rev /min a very high overspeed safety margin applied, and at the higher speed of 7950 rev/min an adequate margin is still maintained.

CONTROLS AND AUXILIARIES

During the design stages of the TA 2500 it was decided to follow the TB 5000 gas turbine concepts

5


Fig. 7. TA 1750 Flame Tube

Fig. 8. TA 2500 Flame Tube

6

and where possible adopt commonality of components.

The reasons for this decision were threefold:

a ) The TB controls reflect current practices and are well proven ..

b ) The TA controls would have needed complete cedesi,>cn to handle the greatly increased power. This would have been impossible to achieve within the time scale desired and would have resulted in a new unproven design.

c ) The use of the 'rB controls provide a greater measure of standardisation and simplifies production with benefits to the user.

There is one notable exception to the above i.n the TA 2500 concept in that a gas generator driven auxiliary gearbox has been introduced.

It has for some time been recognised that gas generator driven auxiliaries, such as lubricating and fuel pumps would give a worthwhile simplification in system design and layout and reduce the external a. c.

or d.c. power requirement. This is particularly evident in the case of pre and post lubricating requirements. Electric motors used for driving the lubricating and fuel pumps together with the associated wiring, connection boxes and other controls would be eliminated and the gearbox mounted auxiliaries at the cold end of the engine would give better accessibility to the engine for servicing, whilst being in a better environment themselves. These design features are illustrated in f�·

The TA 2500 turbine is mounted on a TB type underbase to which a matching base for the driven unit can be bolted, eliminating the need for a combined skid base. The lubricating oil tank is Located within the engine underbase.

The main lubricating oil pump is mounted on the auxiliary gearbox which supplies lubrication to the bearings during start up and when running. To provide

Fig. 9. The Ruston TA 2500 gas turbine


--- ------------------------ ------------------ ---- ----,

Lk RELIEF - - .["J . VALVE

LUB DIL TANK

T

FILTER

I I

�-<!---+-..... DRIVEN UNIT

GG THRUST

PT HOT

GG HOT

GG CENTRE JNL.

GG INLET JNL.

STAGE I GB.

STAGE II GB.

Fig.10. TA 2500 Lubricating Oil System

oil circulation after the turbine has come to rest on shut-down a small d,c, motor driven pump is provided. No other lubricating oil pumps are necessary.

For liquid fuel or dual fuel machines the gear type pump is normally mounted on the auxiliary gearbox and its engagement and disengagement is e:ffected by a magnetic clutch. This pump is the same as that used on the TB engine. The turbine can also operate on gas fuel and the dual :fuel system is provided with automatic changeover from gas to liquid fuel. The fuel is ignited by a high energy system. This is a

REGULATED FUEL GAS

QUID FUEL INLET

DEMISTER

MAIN GAS FUEL SOLENOID

VALVE

ACTUATOR

FUEL PUMP & ELEC. CLUTCH

new feature on the Ruston gas turbine but one which contributes to trouble :free starting and has been well proven. Fig.10 shows diagrammatically the arrangement of the lubricating oil system and Fig.11 the dual fuel system.

An a.c. electric or gas starter motor is mounted on the auxiliary gearbox and rotates the compressor, fuel and lubricating oil pumps at start up. Control of all auxiliary functions is by the Rustronic system which is Ruston designed and rnanu:factured. Fig. 12 shows the control cabinet with its display and control function modules installed.

MAIN LIQUID FUEL SOLENOID

VALVE

HE GENERA TOR

GAS BURNER

PURGE SOLENOID VALVE

DUPLEX BURNER PRESSURISING

VALVE

Fig. 11. TA 2500 Dual Fuel System

7

- FLAME MONITOR

- ANNUNCIATOR 60 WAY

- ��t�r(ii�1�t��;:g��1m - PT TACHO CT TACHO Et TEMP INDICATOR

BLANK OR ADDITIONAL EQUIPMENT EG VIBRATION MONITOR

- OR TEMPERATURE MONITOR OR CHART RECORDER OR MIMIC DIAGRAM

SEQUENCE LOGIC FOR ENGINE - SPACE FOR ADDITIONAL DRIVEN

EQUIPMENT SEQUENCE LOGIC

+- GOVERNOR, TEMPERATURE MONITOR MODULE Et ELECTRONIC OVERSPEED TRIP MODULE

SPACE FOB ADDITIONAL PROCESS MODULE

+- POWER SUPPLY MODULE

- BLANK PANEL

Fig. 12. TA 2500 Control Cabinet

PACKAGING

The turbine with its auxiliaries can be enclosed in a standard versatile hood of the same construction as that for the TB gas turbine.

The hood consists of a frame which can be totally or partially enclosed with acoustic or simple weatherproof panels. The panels are arranged for quick release and are sufficiently light to be manually removed. The enlosure system, fire detection and fighting facilities as well as ventilation and lifting facilities are standard optional features.

A typical packaged set is shown in Fig. 13

CONCLUSION

Dy rematching existing or slightly modifying components of the 1·1ell proven TA 1750 gas turbine, a power increase of some 30% has been obtained with a reduction in specific fuel consumption of 17%.

Minimum changes to the basic design has meant that the traditional reliability of the TA gas turbine is retained. At the.same time the use of updated systems, components and an application philosophy common to other engines in the company's

range, has resulted in a versatile package with proven service experience.

Fig. 13. A typical totally enclosed packaged set

REFERENCES

1. Diffusion factor for estimating losses and limiting blade loadings in axial flow compressor blade elements, by Seymour Leiblein, Francis C. Schwenk and Robert L. Broderick, Lewis Flight Propulsion Laboratory, Cleveland, Ohio.


a 2500 hp addition to the ruston range

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