GAS TURBINE SYSTEM COMPONENT BOUNDARY CONDITIONS

14 Appendix E System layout boundary conditions

14.2 GAS TURBINE SYSTEM COMPONENT BOUNDARY CONDITIONS

Turbo machinery (Chapter 4):

Low pressure turbine:

Type:

Initial speed:

Master turbine: none Low pressure compressor:

Type:

Initial speed:

Master turbine: LIT High pressure turbine:

Type:

Initial speed:

Master turbine: none High pressure compressor:

Type:

Initial speed:

Master turbine:

HPT

Model A [TV95]

500 rps

Model A [TV92]

500 rps

Model A [TV95]

500 rps

Model A [TV92) 500 rps

Heat exchangers (Chapter 5):

Inter cooler:

TY pe:

Number of tubes:

Length:

Tube diameter:

Shell diameter:

Recuperator:

Type:

Number of tubes:

Recuperator Length:

Shell and tube 508

1.5 m 0.012.7 m 0.4 m

Micro channel complex 60 000

0.5 m

Dilution zone: 70 - 75%

Fuel : Kerosene

Primary losses: Darcy-Weisbach Fixed heat transfer: None

Fixed exit temperature: 700°C Pipes (Chapter 7):

Primary losses: Darcy-Weisbach Fixed heat transfer: None

Fixed exit temperature: None Dimensions: Table 14.1

I

^number

I ^I

Table 14.1: Geometry of pipes in the FlownexO si

Controllers:

PID controller [ 131 Sensed entity:

Controlled entity:

Set point:

Dead band:

Upper limit:

Lower limit PID controller [ 141

Sensed entity:

Controlled entity : Set point:

Dead band:

Upper limit:

Lower limit

Length [m]

Pipe

PID controller [ 151 Sensed entity:

Controlled entity:

Set point:

Dead band:

Upper limit:

Lower limit

Diameter [m]

LFT Rotation speed [rps]

Combustion chamber exit temperature ["C]

700 rps 1 rps 700°C 50°C

LFT Rotation speed [rps]

Combustion chamber exit temperature ["C]

950 rps 1 rps 700°C

1 00°C

LFT Rotation speed [rps]

Combustion chamber exit temperature ["C]

1200 rps 10 rps 700°C 400°C

The conceptual design for development 1477

of a micro gas turbine generator.

Appendix E: System layout and start-up sequence 14.3 MICRO GAS TURBINE SYSTEM START-UP SEQUENCES

14.3.1 Start-up: First stage

The first stage (PID Controller 13) will simulate cold starting where all the temperatures in the different components are still equal to atmospheric conditions. The generatorlmotor configuration drives the LP turbine at a starting speed of 500 rps and the TIT of 50°C. Controller 13 will control the LP turbine speed at 500 rps. The motor will drive the turbine for a short time only, thereafter, the motor will be switched off, causing the LP turbine to loose speed. In an attempt to generate more power, Controller 13 will add more heat, causing the LP turbine to speed up, providing the power needed by the turbine machine. This is accomplished by increasing the fuel to the combustion chamber, hereby adding the chemical energy to be converted into heat.

The TIT will rise until the turbine's speed is equal to the controller's set point once more. The controller controls the turbine speed by adjusting the TIT. (This is done by adding heat to speed up the turbine, or by reducing TIT to allow the gas to cool in order to reduce turbine speed.) The first stage control is done by Controller 13, and the reactions to the adjustments can be seen in Figure 14.1 and Figure 14.2.

The HP turbine also reacts to the change in temperatures, but only the LP turbine need to be controlled for the generator is driven by the latter. The HP turbine's speed can also be seen in Figure 14.1 for the first stage of start-up.

Time step

-

800 -

700 - 600 -

500 r ^Y - - - - * . ^.I

.. -

^.,

-.

,.

-

D

400 -

-

V)

-

2 ^{300 -}

m 200 -

loo -

0 T - _-1

0 5 10 15 20 25 30

--

0 5 10 15 20 25 30

Time step

Figure 14.2: TIT for the 1st stage of start-up

Illustrated in Figure 14.2, one can see Controller 3 will manipulate the TIT in order to maintain a constant LP turbine shaft speed.

14.3.2 Start-up: Second stage

The LP turbine needs to accelerate to a higher speed close to operating conditions. This process is controlled by Controller 14, replacing Controller 13. The resulting values of Controller 13 (TIT of 424°C and LP turbine speed of 500 rps) are used as the input values for Controller 14.

The second stage control is identical to the first stage, but the turbine speed limit is set at a different level.

The LP turbine speed is accelerated (Figure 14.3) by increasing the fuel mass flow to the

1000 900 BOO

-

⁷⁰⁰

- c

⁶⁰⁰

1500

2 ⁴⁰⁰

%

I- 300 200 100 0

combustion chamber (Figure 14.4).

L

Time step

ELP

tufbine speed -HP tufbine speed

--

TI

Figure 14.3: Turbine speed for the second stage of start-up

The conceptual design for development 149

of a micro gas turbine generator.

Appendix E: System lavout and start-up sequence

800

400 k

300 200 100

0

----

25 30 35 40 45 50 55 60

Time step

Figure 14.4: TIT for the second stage of st*

Note: The TIT temperature initially increased from the first stage conditions to the maximum allowable temperature of 700°C to accelerate the turbine. Controller 14 enforced a constant TIT of 700°C until the LP speed reached the target speed of 950 rps. Only then the TIT are allowed to drop to a lower condition that allows the LP turbine to rotate steady at 950 rps. The system is allowed to stabilise at these conditions for a few time steps before the third stage of the start-up process is activated.

14.3.3 Start-up: Third stage

This stage will prepare the micro gas turbine for load following, by controlling the micro gas turbine system to operate close to the expected operating conditions. Therefore, once the load is applied, the micro gas turbine system is already on a running start, but it will be discussed in more detail later in this study.

Controller 15 concludes the start-up procedure by taking over from controller 14 controlling the LP turbine speed at 1200 rps. The third start-up stage's turbine speed and TIT can be seen in Figure 14.5 and Figure 14.6 respectively.

55 60 65 70 75 80 85 90 95 100 Time step

+LP turbine speed -HP turbine speed

Figure 14.5: Turbine speed for the third stage of start-up 700 1

1 7 --

55 60 65 70 75 80 85 90 95 100

Time step

Figure 14.6: TIT for the third stage of start-up

Note: The TIT as well as both the turbine speed values is stable towards the end of this start-up simulation. The TIT value is well within the bounds of the controller (400 - 700 "C), and well clear of the upper limit of 700°C.

The controller increases the TIT initially in order to accelerate the LP turbine, but decreases the TIT as soon as the turbine's speed approaches the target range. This allows the system to operate more smoothly, limiting shocks that accompany sudden changes.

The conceptual design for development of a micro gas turbine generator.

Apwndix F: Lubrication system