245362 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, selfcontained 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. shows The Turbine Technologies, Ltd. Minilab Gas Turbine Power System along with the notebook computer for data collection. Figure 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. 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 0. OIL QUANTITY. VERIFY. MINILAB ELECTRICAL SERVICE. CONNECT 2. MINILAB AIR SERVICE... CONNECT 3. AIR PRESSURE.. APPROX. 20 PSI (827 kpa) 4. COMPUTER DAQ SYSTEM CONNECT USB CABLE 5. COMPUTER DAQ SYSTEM 2..... COMPUTER ON 6. OBSERVERS... BRIEFED 7. FINAL CHECK.. COMPLETE Start, operation and shutdown. 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 0. LCD DISPLAY.......... RUN RUN DISPLAYED. OPERATE ENGINE AS REQUIRED... FULL RANGE OF POWER AVAILABLE 2. ENGINE STOP.....RED STOP BUTTON 3 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 628 USB DAQ module. Thirteen (3) 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. Plot compressor inlet/outlet pressure vs. time..2 Plot turbine inlet/outlet pressure vs. time..3 Plot fuel flow vs. time..4 Plot thrust vs. time..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:.6 Plot the thrust specific fuel consumption (T.S.F.C) vs. rotational speed..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 MiniLab TM Gas Turbien Power System, Operator s manual, Turbine Technologies Ltd. Revision 0- (.0). Jan 9, 206
Appendix. Fundamental concepts Figure A 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 A. Simplified Line Diagram of a Simple Gas Turbine.. 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 W shaft Q pi V i po V o m u i gz i m u o gz o dt dt i 2 o 2 () Subscript i refers to inlet and subscript o refers to outlet. Since hu p Therefore, for zi z o 2 2 shaft V i Vo i o W Q m h m h dt dt 2 2 (2)
where h i is the inlet enthalpy and h o is the outlet enthalpy. 2 2 W shaft Q Vo V m h i o h i dt dt 2 2 (3) For compressor (from figure ) with the adiabatic process, equation 3 can be written as W dt shaft compressor m h02 h0 (4) where h 0 is the stagnation enthalpy at compressor inlet. h 02 is the stagnation enthalpy at compressor outlet. For combustion chamber, equation 3 can be written as Q dt combustion 03 02 m h h (5) Where h 02 is the stagnation enthalpy at combustion chamber inlet. h 03 is the stagnation enthalpy at combustion chamber outlet. For turbine with the adiabatic process, equation 5 can be written as W dt turbine m h04 h03 (6) where h 03 is the stagnation enthalpy at turbine inlet. h 04 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 p RT (7) 2 p0 p V (8) 2 p p 0 k M 2 2 k k for an isentropic process (9)
T T 0 k 2 M for an isentropic or irreversible adiabatic process (0) 2 M V () c c krt (2) where p 0 is the stagnation pressure. p is the static pressure. T 0 is the stagnation temperature. T is the static temperature. is the gas density. R is the gas constant. k is the specific heat ratio. M is the Mach number. V is the gas velocity. c 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 F Fs FB V V da (3) cs F ( m m ) V m V ( p p ) A (4) T air fuel e air i e i e where F T is the thrust from the gas turbine unit. m air is the mass flow rate of the air entering the gas turbine unit. m fuel is the mass flow rate of the fuel entering the gas turbine unit. V e is the velocity of the gas exiting from the gas turbine unit.
V i is the velocity of the air entering the gas turbine unit. p e is the pressure of the gas exiting from the gas turbine unit. p i is the pressure of the air entering the gas turbine unit. A e is the exit area of the gas turbine unit. weight of fuel burned / hour f gf T. S. F. C (5) Thrust force T where T. S. F. C = thrust specific fuel consumption, ( N / ( N hr) ). fuel thrust f = fuel volume flow rate (litre/hr). f g = specific weight of the fuel (N/litre). f = density of the fuel (kg/m 3 ). 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. -2: adiabatic and reversible (isentropic) compression, 2-3: constant pressure heat addition, 3-4: adiabatic and reversible (isentropic) expansion and 4-: constant pressure heat rejection Figure A.2 P-V Diagram for an ideal Gas Turbine Cycle.
.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. CV A 0- A 5 T, P, A Figure A.3 The gas turbine unit and the silencer with the applied control volume. Calculation procedure. Calculate the inlet air static pressure ( p ) from the measured dynamic pressure ( p0 p ) at the compressor inlet (the reading of the pressure at station is the dynamic pressure of the air entering the compressor (measured by pitot static tube)), by assuming the stagnation pressure ( p0 ) is equal to 0.3 kpa. 2. Calculate the inlet air density ( ) from the inlet air pressure, (i.e. p RT ). 3. Calculate the average velocity of the air at the compressor inlet from the measured dynamic 2( p0 p) pressure ( p0 p ) at the compressor inlet, ( V ).
4. Calculate the mass flow rate of the air entering the compressor, ( mair V A ). 5. Calculate the average velocity of the air at the silencer inlet by neglecting pressure loss of the silencer, ( V0 VA A ) 0 V0 6. Calculate the Mach number of the air entering the compressor, ( M 0 and c0 krt0 ). c 7. Calculate the mass flow rate of the fuel entering the gas turbine unit from the measured value, ( mf f f ). 8. Calculate the Mach number of the exit gas from eq. 9 by assuming the static pressure of the exit gas ( p 5 ) be atmospheric pressure, ( M 5 k k p 05 2 ) p atm k 9. Calculate exit gas static temperature from the measured stagnation temperature, T05 T5 k 2 M 5 2 0. Calculate the exit gas velocity, ( V 5 M 5 krt 5 ).. Calculate the thrust force, FT ( mair mfuel ) V5 mairv 0 ( p g A0 ). 2. Calculate the thrust specific fuel consumption from the expression in eq. 5. 0 Let f = 832 kg/m 3 for the fuel (Diesel), A = 0.00305 m 2, A 0=0.06286 m 2, A 5 = 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. 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. 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.. 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.
2..2 Centrifugal Flow Compressor Figure A2. SR-30 Engine Components Cutaway 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 550 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..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..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..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..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..7 Transition Liner Hot combustion gases leaving the annular combustor are turned back 80 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..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 78 alloy. 2..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..0 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.. 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. 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 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. 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.. 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 n 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. 0. OneTouch LCD Display Panel: All OneTouch System indications are presented on the LCD Display Panel. This panel is backlit for low light settings.. 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 N% value. As N 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 N 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 N 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. 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 628 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 6 differential analog (up to +-0V full scale) or thermocouple input channels, 6 programmable ranges, 500V optical isolation, 6 digital I/O lines and four frequency/pulse channels. The integrated USB connection allows a single cable interface of up to 6 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 628 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 (3) 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. 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.