2145362 Gas Turbine

Somsak Chaiyapinunt

Gas turbines, like other heat engines, achieve conversion of heat energy of a fuel into

mechanical energy by carrying out a sequence of processes, i.e. a cycle, on its working fluid. Typically

a parcel of this fluid is first compressed and then heated either by burning a fuel in the fluid or by

bringing the fluid into contact with an external source of heat energy. The hot high pressure flow then

expands back to atmospheric pressure and in doing so provides both sufficient work to drive the

original compression process and residual work to drive an external load.

Unlike the petrol or diesel engine however in a gas turbine these processes do not take place

within the same compartment but in separate compartments or components, i.e., a compressor, a

combustion chamber (or heat exchanger), and a turbine. A consequence of this type of arrangement is

that, under a steady rotational speed of the component, i.e., pressure, temperature, velocity, are steady.

Additionally as a parcel of fluid passes from one component to another component it continually

displaces a parcel of fluid in front of it and it is itself replaced behind by the next parcel. The gas

turbine is therefore characterized by steady flow processes as opposed to the essentially non-flow

processes of reciprocating machinery.

Motivation

Gas turbines are becoming increasingly used as power plants for a wide variety of applications

around the world. Originally they were developed solely for aircraft propulsion where their inherent

low specific weight (i.e. mass/unit power) made them essential for high speed flight. For this particular

purpose they have been developed to a high degree of efficiency both thermodynamically and

mechanically.

Due partly to the impetus from the aircraft engine field and also to other significant operational

advantages, industrial gas turbines have been and are being developed for such diverse applications as

electrical power peak lopping stations, fire fighting pump sets, natural gas pumping and compressor

units, factory power and process heating plants, heavy lorry propulsion, rail and ship propulsion.

Objective

To study the performance of a gas turbine unit

Brief Description of Apparatus

The Turbine Technologies, Ltd. Minilab Gas Turbine Power System is a complete, self-

contained jet engine laboratory featuring the purpose built SR-30 Jet engine. The unit consists of a

centrifugal flow compressor, annular combustor and axial flow power turbine. The SR-30 Engine is

typical of the basic engine core found in turbofan, turboprop and turboshaft gas turbine engines. These

types of engines are used for aircraft, defense system and maritime propulsion as well as stationary

industrial power generation. Fig. 1 shows The Turbine Technologies, Ltd. Minilab Gas Turbine Power

System along with the notebook computer for data collection.

Figure 1 Gas Turbine Power System along with the notebook computer for data collection.

Systems

The minilab gas turbine power system is comprised of a turbojet engine tied with various

support equipment that enables engine operation. They are gas turbine unit, accessories and cabinetry.

Gas turbine unit

The gas turbine unit (SR-30 turbine engine) is shown in a cutaway image in Fig. 2. It consists

of a centrifugal flow compressor, annular combustor and axial flow turbine. The additional equipments

in the gas turbine unit are an inlet, diffuser, fuel atomization nozzle, fuel controller, transition liner,

vane guide ring and thrust nozzle. The details of the related equipments of the gas turbine unit can be

seen in the appendix.

Figure 2 The SR-30 Turbojet engine.

Accessories

All engine ancillary accessories are located separate from the engine itself. They are fuel

system, oil system, ignition system and starting air system. The details of the related equipments of the

accessories can be seen in the appendix.

Cabinetry

The minilab features a fully integrated test cell mounted atop the system cabinetry. They are a

test section, operator panel, auto start system, chassis and electrical system. The details of the related

equipments of the cabinetry can be seen in the appendix.

Operating Instructions

Starting

This section provides a set of standard procedures to follow while operating the gas turbine

unit. Fig. 3 shows the system control/display panel. The summary operating checklists are provided as

follows:

Figure 3 system control/display panel.

Prestart 1. AREA CHECK ……………………………………………….…..…………….VERIFY SUITABILITY FOR OPERATION 2. AREA CHECK……………..…………………………..…………………….. VERIFY SUITABILITY FOR OPERATION 3. PERSONAL PROTECTION EQUIPMENT ……………..…………………….……………. AVAILABLE and USED 4. FIRE EXTINGUISHER……………………………………....…… LOCATE and FAMILIARIZE with OPERATION 5. CASTER WHEELS...………………….………………………..…..……….…………..………………………………..LOCKED 6. KEYED MASTER SWITCH……………….………………..………………………….…………………….………………..OFF 7. THROTTLE LEVER.……………………………………….....………...MINIMUM POWER, FULL AFT POSITION 8. VISUAL INSPECTION

a. VIEWING SHIELD ……………………………………………………………..………………..…………..... CHECKED b. INLET DUCTING ……………………………………………………………..……..………..……………….. CHECKED c. EXIT DUCTING …………………………………………………………………..……….………..…….……. CHECKED d. ENGINE MONITORING ……………………………………………………..….………………...…....…. CHECKED e. ENGINE FLUID LINES ………………………………………………………………………..…..…...………CHECKED f. ENGINE SENSOR LINES ………………………………………….………………...………….………….. CHECKED g. ENGINE INLET BELL ………………………………………………………………..…..………….………… CHECKED h. ENGINE COMPRESSOR ……………………………………………………………….……….………….. CHECKED i. ENGINE INLET AREA …………………………………………………………………..………..…...…….. CHECKED j. EXHAUST MANIFOLD EXIT AREA ……………………………………………..………….……………. CHECKED k. CABINET INTERNALS ……………………………………………………………..……..…….…………... CHECKED

9. FUEL QUANTITY …………………………………………………..………………………………………………… CHECKED 10. OIL QUANTITY …………………………………………………………………………………………………………. VERIFY 11. MINILAB ELECTRICAL SERVICE ……………………………………….…………………………………… CONNECT 12. MINILAB AIR SERVICE ……………………………………………………….……………..………………… CONNECT 13. AIR PRESSURE ………………………………………………………………………….. APPROX. 120 PSI (827 kPa) 14. COMPUTER DAQ SYSTEM 1 ……………………………………………………………… CONNECT USB CABLE 15. COMPUTER DAQ SYSTEM 2 ……………………………………………………………..………... COMPUTER ON 16. OBSERVERS …………………………………………………………………………………..………………………. BRIEFED 17. FINAL CHECK ……………………………………………………………………………….……………………. COMPLETE

Start, operation and shutdown

1. KEYED MASTER SWITCH………………………………………………………………..………………….…………………ON 2. TURBINE INLET TEMPERATURE PANEL METER (TIT)……..………….………………………….…VERIFY ON 3. ENGINE RPM PANEL METER (ENGINE RPM) ……..……………………..…………………………… VERIFY ON 5. ENGINE THROTTLE LEVER………...….…MINIMUM POWER, FULL AFT POSITION (DETENT CLICK) 6. LCD DISPLAY……………………………………..………….….VERIFY THROT POSITION FLAG ILLUMINATES 8. LCD DISPLAY……………………………………………….………………………………..….RDY – READY DISPLAYED 9. ENGINE START……………………………………………….……………………………………GREEN START BUTTON 9. ENGINE RUN……………………………………………..….……..…..….. .Engine Will Start Within 20 Seconds 10. LCD DISPLAY…………………………………………..…….…..…….……..……….…….… RUN – RUN DISPLAYED 11. OPERATE ENGINE AS REQUIRED………………..………….………FULL RANGE OF POWER AVAILABLE 12. ENGINE STOP………………………………………………….………………………………..……..RED STOP BUTTON 13 Engine is ready for restart when RDY (ready) is displayed on LCD Panel

Air clearing procedure The following procedure is used to clear the engine when certain WARNING flags warrant.

a. ENGINE…………………………………………………………………………………………………..……………………….OFF

b. THROTTLE LEVER……………………………………………..…………………………..……..….MIDDLE POSITION

c. LCD DISPLAY……………………………………..……………VERIFY THROT POSITION FLAG ILLUMINATES

d. RED STOP BUTTON………………………………………..……………………………………………………………...PUSH

e. GREEN START BUTTON…………………………………………………………………………………………………..PUSH Air will cycle for 5 seconds. Repeat as necessary.

Data collection

The data are collected using the national Instruments 6218 USB DAQ module. Thirteen (13)

system parameters are sensor measured with the stock Minilab configuration. MiniLab software is

provided by the manufaturer to use for data collection. Fig. 4 shows the display screen of the software

controls.

Figure 4 the display screen of the software controls.

Experimental Procedures

Run and maintain (about 5 minutes) the gas turbine unit at a speed about 50,000 rpm.

Start to record the data by using the data acquisition software.

Vary the speed of the gas turbine unit from 50,000 to 76,000 rpm (i.e. 50,000, 60,000, 70,000,

and 76,000 rpm).

Maintain the gas turbine unit at about 5 minutes for each rotational speed and record the data.

Experimental Results

1.1 Plot compressor inlet/outlet pressure vs. time.

1.2 Plot turbine inlet/outlet pressure vs. time.

1.3 Plot fuel flow vs. time.

1.4 Plot thrust vs. time.

1.5 Plot rotational speed vs. time.

Discuss all graphs in details. (i.e. how each parameter varies with other parameters?, what does each

graph tell you?)

At each speed range (i.e. 4 speeds range: around 50,000, 60,000, 70,000, and 76,000 rpm),

choose one represent data point and find and plot the following parameters:

1.6 Plot the thrust specific fuel consumption (T.S.F.C) vs. rotational speed.

1.7 Plot the calculated thrust and measured thrust vs. rotational speed.

Discuss all graphs in details. (i.e. how each parameter varies with other parameters?, what does each

graph tell you?)

Reference

MiniLabTM

Gas Turbien Power System, Operator’s manual, Turbine Technologies Ltd. Revision 01-

11 (1.0).

Jan 9, 2016

Appendix

1. Fundamental concepts

Figure A1 shows the simplified line diagram of a simple gas turbine which comprises of a

compressor, a combustion chamber, and a turbine. The air is fed from the atmosphere to the

compressor. The high pressure air from the compressor is mixed with the fuel and combust in the

combustion chamber. The hot gas from the combustion chamber is expanded in the turbine driving the

compressor and external load. The gas is then exhausted back to the atmosphere.

Figure A1.1 Simplified Line Diagram of a Simple Gas Turbine.

1.1 Basic equations

When considered the energy flow at each component of a gas turbine unit (compressor,

combustion chamber and turbine), the energy balance for a steady fluid flow in each component can be

written as

2 2

2 2

shaft i i o oi i o o

i o

p V p VW Qm u gz m u gz

dt dt

(1)

Subscript i refers to inlet and subscript o refers to outlet.

Since p

h u

Therefore, for i oz z

2 2

2 2

shaft i oi o

V VW Qm h m h

dt dt

(2)

where ih is the inlet enthalpy and oh is the outlet enthalpy.

2 2

2 2

shaft o io i

V VW Qm h h

dt dt

(3)

For compressor (from figure 1) with the adiabatic process, equation 3 can be written as

02 01

shaft compressorWm h h

dt

(4)

where 01h is the stagnation enthalpy at compressor inlet.

02h is the stagnation enthalpy at compressor outlet.

For combustion chamber, equation 3 can be written as

03 02

combustionQm h h

dt

(5)

Where 02h is the stagnation enthalpy at combustion chamber inlet.

03h is the stagnation enthalpy at combustion chamber outlet.

For turbine with the adiabatic process, equation 5 can be written as

04 03

turbineWm h h

dt

(6)

where 03h is the stagnation enthalpy at turbine inlet.

04h is the stagnation enthalpy at turbine outlet.

The gas in the gas turbine can be treated as ideal gas. The relationship of the compressible flow

can be written as

1 1 1p RT (7)

2

01 1 1

1

2p p V (8)

1

2011

1

11

2

k

kp kM

p

for an isentropic process (9)

201

1

1

11

2

T kM

T

for an isentropic or irreversible adiabatic process (10)

11

1

VM

c (11)

1 1c kRT (12)

where 01p is the stagnation pressure.

1p is the static pressure.

01T is the stagnation temperature.

1T is the static temperature.

is the gas density.

R is the gas constant.

k is the specific heat ratio.

1M is the Mach number.

1V is the gas velocity.

1c is the speed of sound.

When considered the force acting on a gas turbine unit, the force balance for a steady fluid

flow can be written as

s B

cs

F F F V V dA (13)

( ) ( )T air fuel e air i e i eF m m V m V p p A (14)

where TF is the thrust from the gas turbine unit.

airm is the mass flow rate of the air entering the gas turbine unit.

fuelm is the mass flow rate of the fuel entering the gas turbine unit.

eV is the velocity of the gas exiting from the gas turbine unit.

iV is the velocity of the air entering the gas turbine unit.

ep is the pressure of the gas exiting from the gas turbine unit.

ip is the pressure of the air entering the gas turbine unit.

eA is the exit area of the gas turbine unit.

/. . .

f fgweight of fuel burned hourT S F C

Thrust force T

(15)

where . . .T S F C = thrust specific fuel consumption, ( / ( )fuel thrustN N hr ).

f = fuel volume flow rate (litre/hr).

f g = specific weight of the fuel (N/litre).

f = density of the fuel (kg/m3).

The working cycle for gas turbine unit is called Brayton cycle. The Brayton cycle under the

isentropic (reversible adiabatic process) is shown in figure A2.

1-2: adiabatic and reversible (isentropic) compression,

2-3: constant pressure heat addition,

3-4: adiabatic and reversible (isentropic) expansion and

4-1: constant pressure heat rejection

Figure A1.2 P-V Diagram for an ideal Gas Turbine Cycle.

1.2 The calculation for the experimental results of the Gas Turbine Unit

For the purpose of understanding the gross behavior of the gas turbine performance, certain

assumptions have been made to simplify the mathematical model of the system. The assumptions are:

one-dimensional flow, steady flow process, the measured properties at the compressor outlet, the

turbine inlet, turbine outlet and the exhaust area are the stagnation properties (temperature and

pressure). Neglect the loss in the silencer that attached to the engine.

A0-1 A5

T1, P1, A1

CV

Figure A1.3 The gas turbine unit and the silencer with the applied control volume.

Calculation procedure

1. Calculate the inlet air static pressure ( 1p ) from the measured dynamic pressure 0 1( )p p at

the compressor inlet (the reading of the pressure at station 1 is the dynamic pressure of the air

entering the compressor (measured by pitot static tube)), by assuming the stagnation pressure 0( )p is

equal to 101.3 kPa.

2. Calculate the inlet air density ( 1 ) from the inlet air pressure, (i.e. 11

1

p

RT).

3. Calculate the average velocity of the air at the compressor inlet from the measured dynamic

pressure 0 1( )p p at the compressor inlet, ( 0 11

1

2( )

p pV ).

4. Calculate the mass flow rate of the air entering the compressor, ( 1 1 1airm V A ).

5. Calculate the average velocity of the air at the silencer inlet by neglecting pressure loss of

the silencer, ( 1 10 1

0 1

V A

VA

)

6. Calculate the Mach number of the air entering the compressor, ( 0 10 1

0 1

VM

c

and 0 1 0 1c kRT ).

7. Calculate the mass flow rate of the fuel entering the gas turbine unit from the measured

value, ( f f fm ).

8. Calculate the Mach number of the exit gas from eq. 9 by assuming the static pressure of the

exit gas ( 5p ) be atmospheric pressure, (

1

055

21

1

k

k

atm

pM

p k

)

9. Calculate exit gas static temperature from the measured stagnation temperature,

055

2

5

11

2

TT

kM

10. Calculate the exit gas velocity, ( 5 5 5V M kRT ).

11. Calculate the thrust force, 5 0 1 1 0 1( ) ( )T air fuel air gF m m V m V p A .

12. Calculate the thrust specific fuel consumption from the expression in eq. 15.

Let f = 832 kg/m3 for the fuel (Diesel), 1A = 0.00305 m

2, 0 1A =0.016286 m

2, 5A = 0.00229 m

2 and

R= 287 J/(kg-K).

Temperature used in the calculation has to be absolute temperature.

2. Detail of the Apparatus

Systems

The MiniLab Gas Turbine Power System is comprised of a turbojet engine tied to various

support equipment that enables engine operation. The engine is similar in design to power plants

typical of aircraft, marine and rail propulsion systems. It is also comparable to industrial and power

generation type gas turbines used in gensets. The only significant difference from these examples is

size. Because of this small size, some of the systems normally found on the engine itself have been

relocated to the system cabinetry for convenience and ease of operation. The following sections briefly

describe the principle of components of the MiniLab, their function and operation.

2.1 Gas Turbine

The SR-30 Turbojet Engine is designed and manufactured by Turbine Technologies, LTD

specifically for the MiniLab Gas Turbine Power System. The SR-30 Turbojet Engine Cutaway in

Figure 5.6 is the same engine as installed in the MiniLab with proportions of selected components

removed to reveal the inner workings of the engine.

A pure turbojet, the SR-30 Engine is representative of all straight jet engines in which

combustion results in an expanding gas that is sufficiently capable of producing useful work and

propulsive thrust. Consisting of a centrifugal flow compressor, annular combustor and axial flow

compressor turbine, the SR-30 Engine is typical of the gas generator core found in turboprop and

turboshaft engines.

Following the gas flow path is the easiest way to understand the relatively simple working of a

jet engine. Each major component of the engine is investigated in turn with consideration given to how

the individual parts contribute to the overall function of the engine. Showcasing the internal

configuration of the basic turbojet, the SR-30 Cutaway image in Figure 5.1 facilitates a qualitative

understanding of gas turbine fundamentals and establishes a foundation for more advanced theoretical

study or experimental exploration of the operating SR-30 Engine itself installed in the MiniLab Gas

Turbine Power System.

The following sections provide a brief introduction to each of the principal engine components.

2.1.1 Inlet

The inlet is the first engine component to encounter the gaseous working fluid (atmospheric

air) necessary for the operation of the gas turbine engine. Not to be confused with the external inlet

and ducting installed on the MiniLab cabinetry (or the aerodynamic inlet on the nacelle of a jet

transport aircraft, for example) the engine inlet performs the final conditioning or treatment of the inlet

air prior to its entering the interior of the engine. The inlet bell of the SR-30 Engine is illustrative of a

typical subsonic inlet duct in which ambient air is directly routed to the face of the compressor. A

purely aerodynamic device, the inlet is not subject to temperature extremes. In the case of the SR-30

Engine, the inlet is investment cast from aerospace quality aluminum, machined to mate with the rest

of the engine and polished on the interior surface to promote the smooth flow of air through the inlet.

Figure A2.1 SR-30 Engine Components Cutaway

2.1.2 Centrifugal Flow Compressor

The compressor (rotor), along with the axial flow turbine, makes up the rotating assembly of

the turbojet engine. The SR-30 Engine utilizes a centrifugal (radial flow) compressor, with the flow

path being referenced to the rotation axis of the compressor itself. As viewed from the front of the

engine looking aft, the engine rotates in a counter-clockwise direction to properly function. Through

this mechanical rotation, energy is imparted to the inlet air. The compressor, also known as an

impeller, typically rotates anywhere from 50,000 to 90,000 revolutions per minute (RPM) depending

upon the amount of load the engine thrust is experiencing. This high rotational speed device takes inlet

air at the impeller hub and centrifugally accelerates it in a radial direction toward the outer

circumference of the impeller where it is discharged through the diffuser. The compressor blade

geometry and the corresponding aerodynamic and fluid forces resulting from the rotation effect a

useful change in the velocity and pressure of the working fluid. At 90,000 RPM, the tip speed of the

compressor is at its greatest radius and therefore the approximate velocity of the air leaving the

compressor 1550 ft/s (473 m/s). Aside from aerodynamic requirements, the compressor must be

mechanically designed to endure the stress encountered while rotating at operating RPM’s. Either

aluminum or steel alloys are used in the manufacture of the compressor.

2.1.3 Diffuser

The diffuser (stator) works in conjunction with the compressor to further process the working

fluid. The compressor discharge air is directed through the diffuser where the fluid velocity is

decreased and the static pressure increased. The SR-30 Engine has a maximum pressure ratio of

approximately 3, meaning the pressure of the air exiting the diffuser is 3 times that of atmospheric. At

sea level on a standard day this would result in a total pressure of 44 psi (303 kPa). This discharge air

also undergoes a 90 degree change in direction, transitioning from a radial to axial flow (oriented

along the length of the engine). The compressor and diffuser working together comprise the

compressor stage of the engine. Like the inlet, the diffuser is investment cast from aluminum and

finish machined.

2.1.4 Annular Combustor

High pressure air leaving the diffuser now enters the combustion chamber or combustor. The

purpose of the combustor is to further increase the potential energy content of the working fluid

through combustion of a gaseous fuel and air mixture. The SR-30 Engine features an annular type

combustor composed of two perforated tubes fixed in a concentric relation to one another. The

combustor is oriented in a reverse flow arrangement with the inlet of the combustor situated at the rear

of the engine. This arrangement allows for the most physically compact engine. Only a small fraction

of the available compressor air is necessary to support combustion. Mixed at the inlet end of the

combustor, this primary air and fuel is ignited during engine start by a high voltage spark type igniter

plug. Once the engine is started, the igniter is no longer necessary as the combustion process becomes

self-sustaining. Air in excess of that needed for combustion, termed secondary air, enters through the

larger combustor holes and helps to both stabilize and position the combustion flame within the

combustor walls and to cool the combustion gases to a value suitable for engine operation (limited by

component material properties). Typical combustion temperature ranges from 400C to 800C. Because

of these higher temperatures, the annular combustor is manufactured from Inconel sheet, rolled into

the proper shape and welded. The individual primary and secondary air holes are laser cut.

2.1.5 Fuel Atomization Nozzle

Fuel enters the combustion inlet through six equally spaced fuel atomization nozzles located at

the extreme rear of the engine (mounted so as to protrude into the inlet of the reverse flow annular

combustor). The nozzles are designed to fully atomize the fuel as it exits the nozzle. Atomization aids

in the efficient, clean and thorough combustion of the fuel and air mixture. Combustion is further

enhanced by the introduction of turbulence within the fuel nozzle to combustor mounting assembly.

The advanced nozzle design permits a wide range of heavy type fuels (diesel, kerosene) to be used in

the engine without the need for preheating or other forms of fuel conditioning. The amount of fuel

necessary to operate the engine varies with the desired power output. A common measure of fuel

usage is Specific Fuel Consumption (SFC) which relates the amount of fuel per unit of thrust per unit

of time. The SR-30 Engine has an SFC of approximately .80 at high RPM (high thrust).

2.1.6 Fuel Controller

Fuel is provided to the atomization nozzles via the fuel controller. The engine speed is

regulated by controlling the amount of fuel entering the combustor through the fuel atomization

nozzles. Fuel is delivered to the controller at constant pressure. The controller then regulates the

amount of fuel reaching the atomization nozzles through a high pressure, return flow throttling

technique. At low engine speeds, the majority of fuel entering the fuel controller is allowed to return to

the fuel source. When higher engine speeds are desired, the fuel controller return line is restricted

causing more fuel to reach the nozzles.

The engine is fully throttleable over the entire performance envelope from idle to maximum

power. There is no restriction on the speed or rate at which the fuel controller may be moved. The fuel

controller movement causes a nearly instantaneous response in engine power.

2.1.7 Transition Liner

Hot combustion gases leaving the annular combustor are turned back 180 degrees by the

transition liner. While combustor gases move in the reverse direction, the transition liner returns the

flow path to the normal front to back direction.

2.1.8 Vane Guide Ring

The vane guide ring (stator) is the first component in the turbine stage and permits the turbine

to extract useful work from the combustion process. This ring consists of a shrouded series of small

airfoil blades each facing into the oncoming combustion gas flow as directed by the transition liner. As

the flow path narrows between the individual blades, the hot, high pressure combustion gases are

accelerated to a high velocity, high energy flow. The vane guide ring further directs this accelerating

gas in such a manner as to produce the most effective reaction against the turbine blades.

Like the combustor components, the vane guide ring is manufactured from Inconel 718 alloy.

2.1.9 Axial Flow Turbine

The turbine (rotor) absorbs energy from the accelerating gas flow and converts it into usable

mechanical power. Further acceleration of the expanding flow takes place through the turbine blades.

Much like blades of the vane guide ring, the individual turbine blades are also airfoil shaped. A

combination of aerodynamic and reaction forces cause the turbine to rotate. Coupled to the

compressor, the sole job of the turbine is to effect a rotation of the compressor to perpetuate the engine

flow process. Only the power necessary to drive the compressor is extracted from the flow as it

expands through the turbine blades. The remaining energy is available and utilized for the generation

of propulsive thrust.

The turbine wheel is designed as an integrally bladed disk commonly called a blisk. The

turbine wheel blisk is precision vacuum investment cast from CMR 247 Super Alloy.

2.1.10 Thrust Nozzle

A convergent tube of gradually decreasing cross-section, the thrust nozzle converts the

remaining combustion heat energy into kinetic energy. The gas accelerates through the nozzle at high

velocity resulting in propulsive thrust at the nozzle exit. The thrust nozzle also serves as a turbine

wheel containment ring in the vent the turbine wheel were to come apart while the engine is running.

2.1.11 Miscellaneous

Numerous other components such as bearings, seals, fittings, galley ways and fasteners are

found throughout the engine.

2.2 SR-30 Gas Turbine Engine Accessories

For simplicity and ease of operation, all engine ancillary accessories are located separate from

the engine itself.

2.2.1 Fuel

The MiniLab fuel system is comprised of a fuel reservoir, fuel pump and fuel delivery lines.

The stainless steel fuel reservoir, accessed from the rear of the MiniLab cabinet, holds 7 gallons (26.5

ltrs) of fuel. Fuel is pumped from the reservoir by an electrically driven fuel pump, passed through a

fuel filter and sent through the fuel lines to the fuel controller. Fuel in excess of that needed by the fuel

controller is routed back to the fuel reservoir.

2.2.2 Oil

The MiniLab features a fully recirculating oil system. The oil system is comprised of an oil

reservoir, oil pump and oil delivery lines. The stainless steel oil reservoir, accessed from the rear of the

MiniLab cabinet, holds 1 gallon (3.8 ltrs.) of oil. Oil is pumped from the reservoir by an electrically

driven oil pump, passed through an oil filter and sent through the oil delivery lines to the engine. Oil

flows through oil galley-ways in the engine that directs oil to the main bearings upon which the

compressor and turbine ride. The oil is used to cool and lubricate these bearing. After the oil flows

through the bearings, it is returned to the oil reservoir.

2.2.3 Ignition

A dedicated exciter box provides high voltage to the single spark igniter used to initiate

combustion. Combustion is self sustaining once the engine starts. The exciter box is shut off and the

igniter ceases to spark.

2.2.4 Starting Air

Compressed air is used to start the engine. A standard air fitting is provided on the back of the

MiniLab cabinet for the connection of standard shop air. A solenoid valve controls the flow of air from

this fitting to the engine via an air line. The air line attaches to the engine and is oriented to direct air

tangentially against the engine compressor. This air rotates the compressor up to a speed sufficient to

start the engine.

2.3 Cabinetry

2.3.1 Test Section

The MiniLab features a fully integrated test cell mounted atop the system cabinetry. Front and

rear viewing shields allow observation of the engine/generator during operation while providing a

safety barrier between the engine and observers. Access to the engine is gained by opening the test cell

about its side hinged connection. All engine fluid, electrical and sensor lines pass through the floor of

the test cell into the cabinet below.

2.3.2 Operator Panel

Various controls and indicators are provided to assist the operator in using the MiniLab.

1. Keyed Master Switch: The key lockable system master switch controls the supply of electrical

power to the main bus that powers all MiniLab System components. When selected ON, power is

available to the MiniLab. When selected OFF, no power is available to any system component,

thereby preventing the engine from running. In all cases, removing MiniLab electrical power by

selecting this switch to OFF will cause the engine to stop running.

2. Green Start Button: The start button’s primary function is to initiate the automatic engine start

sequence through the OneTouch Gas Turbine Auto Start System. This button controls a number of the

OneTouch system functions depending upon the current system state. See Section 5.3.3 for more

information.

3. Red Stop Button: The stop button’s primary function is to command the OneTouch System to stop

or shutdown a running engine. Pressing this button will immediately cause the engine to stop

operating. If, for any reason, this button fails to stop the engine, the Keyed Master Switch can be used

as a backup to stop the engine. This button controls a number of other OneTouch System functions

depending upon the current system state. See Section 5.3.3 for more information.

4. Oil Pressure Gauge: The oil pressure gauge provides a direct indication of oil pressure available to

the engine for cooling and lubrication. The oil pressure setting is established at the factory prior to

shipment and should fall in the range specified in Section 2.

5. P3 Gauge: The P3 gauge indicates gauge pressure in the combustion can of the engine. This value

provides a relative measurement of engine power.

6. Fuel Pressure Gauge: The fuel pressure gauge provides a direct indication of fuel pressure directed

to the engine fuel control unit. The fuel pressure setting is established at the factory prior to shipment

and should fall in the range specified in Section 2.

7. Air Pressure Gauge: The air pressure gauge provides a direct indication of air pressure available

for engine starting. The indicated air pressure must fall in the range specified in Section 2 for proper

engine starting.

8. Turbine Inlet Temperature – TIT – Panel Meter: The TIT panel meter indicates the temperature

of the combustion gases just prior to entering the compressor turbine. Maximum TIT is specified in

Section 2.

9. Engine Rotational Speed – RPM – Panel Meter: The RPM panel meter indicates the rotational

speed of the compressor and turbine (also know and n1 speed) of the SR-30 Engine. The higher the

RPM, the greater the flow through the engine and the higher the indicated thrust. Maximum RPM is

specified in Section 2.

10. OneTouch LCD Display Panel: All OneTouch System indications are presented on the LCD

Display Panel. This panel is backlit for low light settings.

11. Power Lever (Throttle): The T-Handled Power Lever controls the amount of thrust the engine

produces by throttling the amount of fuel allowed to flow into the fuel nozzles (via the fuel controller).

The power lever is set up in the conventional way: full power is away from the operator, idle power is

towards the operator. The power lever also controls a number of OneTouch functions depending upon

the current system state. See Section 5.3.3 for more information.

2.3.3 OneTouch Gas Turbine Auto Start System

The OneTouch Gas Turbine Auto Start System simplifies operation of the MiniLab through the

automation of the engine start sequence. It further assists the operator by continuously monitoring

critical engine temperatures and RPM as well as verifying an adequate supply of fuel and oil during

operation.

The OneTouch System utilizes a dedicated computer and purpose designed controller board to

provide the automation functions. The computer and controller, along with a dedicated power supply

and LCD Display are packaged into the OneTouch box and mounted beneath the MiniLab operator

panel.

Operation of the MiniLab equipped with the OneTouch System is both intuitive and

straightforward. The keyed master switch limits MiniLab operation to those that are authorized to do

so. With the keyed switch on, power is immediately applied to the OneTouch System computer.

During system initialization, several screens are displayed that provide basic MiniLab information

such as unit serial number, registered owner and cumulative system time displayed as engine run-time

and total engine start/stop cycles. The availability of this information is particularly helpful when

making operational or service inquiries to the factory.

A key, two buttons and the traditional T-handled power lever located on the MiniLab operator

panel are all that is necessary to operate the MiniLab through the OneTouch System. A backlit LCD

display panel integral to the operator panel severs as the primary user interface. During normal

operation, the LCD display indicates all monitored engine parameters and provides a simple indication

of system state. Should the OneTouch System command an engine shutdown, the cause for the

shutdown will be displayed. Additional diagnostic functions are available through a combinatorial

selection of the two buttons and power lever.

Following initialization, the OneTouch System will display the normal operation screen and

indicate the engine is ready to start through the RDY or ready flag. The throttle lever needs to be in the

full aft position to arm the START button. If the throttle is in any other position, an indication on the

display screen will flag the operator to reset the throttle. Pressing the green START button commences

the Auto Start sequence. The RDY flag will change to STR indicating the staring sequence in

underway. Engine rotation begins through the introduction of starting air. Rotational speed is

displayed as a percentage of the maximum engine RPM limit as indicated by the N1% value. As N1

increases, fuel is introduced at the appropriate time and ignited thereby starting the combustion

process. The displayed Turbine Inlet Temperature (TIT) values will show an immediate temperature

rise indicating positive combustion. As N1 continues to increase, the P3 pressure value relating total

engine pressure to ambient will also increase. Starting air remains on until the engine achieves a stable

idle RPM and the TIT has cooled to an acceptable lever. Once the starting air is shut off, the display

will show the RUN flag to indicate the starting sequence was successful.

The engine is now running and may be operated as desired. For reference purposes, an elapsed

run-time counter displays the time since engine start. Stopping the engine is as easy as pressing the red

STOP button. The OneTouch System continues monitoring the engine through the entire shutdown.

The RUN flag will now change to AIR to let the operator know the engine is spooling down and only

air is passing through it. Once N1 and TIT values are within safe start limits, the OneTouch System

enables the engine for an immediate restart by indicating RDY once again. Through the OneTouch

System, the engine may be repeatedly started and stopped without any adverse affect to the engine or

the MiniLab system.

During start and operation, should any critical engine value be exceeded or a problem found

with any MiniLab system, the OneTouch System will command an engine shutdown and alert the

operator to the problem. Faults are segregated between CAUTION and WARNING depending upon

the severity of the problem and the operator intervention required to rectify the fault. A CAUTION is

indicative of a minor problem that can be immediately fixed. Low fuel or oil levels are examples of

CAUTIONs that are fixed simply by adding the appropriate fluid. A WARNING suggests the potential

for a more serious problem that must be investigated before the engine can be run again. See Table 5.2

and Table 5.3 for a complete listing of CAUTION and WARNING flags.

The air solenoid and the engine ignition system can be operated independently of the auto start

sequence for diagnostic and test purposes. To do so, and with engine off, move the throttle lever out of

the aft position so that the CAUTION – THROT POSITION screen is displayed. With this screen

displayed, push the red STOP button. A new screen will display indicating that the AIR &

IGNITION are OFF. Pressing the green START button will close the air relay for five seconds.

Pressing the red STOP button will close the ignition relay for five seconds. The display will indicate

whether the air or ignition is on or off. A working air relay will make a “snapping” sound if the air is

not hooked up and the usual compressor whine if air is connected to the MiniLab. A working ignition

system will emit a low volume ”hissing” or static like sound from the engine while the ignition is on.

It is not necessary to test these functions during normal MiniLab usage. Certain WARNING flags may

require the air test function if they are encountered, See the CAUTION and WARNING flag

descriptions that follow, Tables 5.2 and 5.3 (note: If air is connected to the MiniLab when testing the

air function, the SR-30 Engine will spool up just as it would during a start sequence. Although no fuel

will be introduced, the engine should be considered in operation requiring all operators and observers

to remain clear of the test cell inlet and exit, and that appropriate eye and hearing protection be

worn.)

2.4 Data Acquisition System

The MiniLab comes equipped with a National InstrumentsTM precision data acquisition

system permitting a full range of system parameter measurement. This system, comprising a suite of

sensors, excitation power sources, signal conditioners, data acquisition hardware and user interfaces

software, when used in conjunction with an appropriate computer, allows actual run-time data to be

displayed and recorded for later analysis. Off the shelf hardware, industry standard software and

factory setup and calibration of the data acquisition system makes data collection a trivial event

allowing the educational emphasis to be placed on system operation and analysis.

Additional information can be obtained from the respective manufacturer’s equipment and

software manuals contained in the three-ring binder included with the MiniLab. In the unlikely event

that data acquisition system software settings or sensor calibration is lost; all factory settings are

provided on CD-ROM for quick data restoration. Additional information regarding default system

settings can be found in subsequent sections of this chapter.

2.4.1 Computer

The MiniLab is typically provided with a Microsoft Windows-based laptop computer for

portability and system security. Final factory sensor settings are saved to this computer as well as a

standard user interface display for initial system familiarization and data collection runs. The computer

is equipped with a writable CD-ROM and Ethernet interface to facilitate run-time data dissemination.

For maximum flexibility, the system is designed to work with any Windows-based computer equipped

with a standard Universal Serial Bus (USB).

2.4.2 DAQ Module

The MiniLab Digital Data Acquisition System utilizes a National Instruments 6218 USB Data

Acquisition Module. The unit features a 22-bit analog to digital conversion capability. Multiple

voltage channels, thermocouples, pulse, frequency and digital I/O can be measured and controlled.

This is accomplished through 32 single-ended or 16 differential analog (up to +-10V full scale) or

thermocouple input channels, 16 programmable ranges, 500V optical isolation, 16 digital I/O lines and

four frequency/pulse channels. The integrated USB connection allows a single cable interface of up to

16 feet (5 meters) between the MiniLab and the data acquisition computer. This distance is easily

increased up to 98 feet (30 meters) through the use of powered USB hubs (serving as data repeaters).

The USB’s high-speed data transfer rate (up to 250Ks/s) allows for a real-time display of acquired

data, while eliminating the need for buffer memory in the data acquisition system itself.

Figure A2.2 National Instruments 6218 USB DAQ Module

Unused data channels are available for operator use. With sensors or transducers appropriate to

the variables of interests, interface to the DAQ Module is accomplished through convenient,

removable screw-terminal input connections.

2.4.3 Sensors

Thirteen (13) system parameters are sensor measured with the stock MiniLab configuration.

Some data acquisition channels are utilized in single-ended mode while others are used in differential

mode.

Figure A2.3 Sensor locations DAQ Module.

Figure A2.3 Sensor locations DAQ Module (cont.).

Table A2.1 DAQ channel assignments and sensor details.

Figure A2.4 Minilab sensor locations.

Figure A2.5 Compressor inlet and sensor locations.

Figure A2.6 Nozzle exit and sensor locations.

Figure A2.7 Gas turbine cutaway and engine sensor locations.