2010 Gas Turbine Industrial

Fellowship Presentation

John PagliaroSolar Turbines Incorporated

Combustion Group

Summer 2010

Background Information

Activities:-Virginia Active Combustion Controls Group

-American Society of Mechanical Engineers

-Society of Engineering Science

-Society of Fire Protection Engineers

Previous Internship:-National Energy Technology Lab (NETL)

Assistant Combustion Research Associate

BS in Mechanical Engineering and Engineering

Science and Mechanics

Virginia Polytechnic Institute and

State University

Summer Objectives

1) Determine the capabilities of the Thermo-acoustic Network software by performing “break and fix” exercises

2) Note anything that could use improvement or more background info so the software is user friendly

3) Validate the software results against experiments where the oscillations behavior can be measured

4) Ensure the software designers at Georgia Tech are heading toward the final product desired by Solar Turbines

Combustion Induced Oscillations:Pressure pulses that grow inside the combustor during certain operating

conditions

Causes:Flame dynamics

Fuel/Air Premixing

Unsteady heat/temperature release

Unsteady fuel and air flow

Illustration

Combustion Instabilities

Combustion Instabilities

Why study combustion instabilities?

1) To improve emissions

2) To reduce large-amplitude structural

vibrations

3) To protect against flashback and

blowout

Thermo-acoustic Network

Incorporation Into PDTools

• PDTools uses a simplified calculation to determine the natural frequencies at which the system wants to oscillate

• The Thermo-acoustic Network software dives deeper into the physics yielding a more accurate frequency prediction

• Most of the Thermo-acoustic Network inputs are already required in PDTools

• Tabs may be added to PDTools to include the capabilities of the Thermo-acoustic Network software

– Dimension Input

– Thermo-acoustic Network Results

1) Flame location 6) Final Temperature

2) Injector Dimensions 7) Final Pressure

3) Liner Dimensions 8) Molecular Weight

4) Initial Temperature 9) Specific Heat Ratio

5) Initial Pressure 10) Mass flow rate

Shared Inputs

1) Plenum Dimensions 3) Frequency Inputs

2) Transfer Function 4) Mode Shape Inputs

New Inputs

Incorporation Into PDTools

Dimension Input

Thermo-acoustic Results

Quartz Rig Model

• Model created in Thermo-acoustic

Network software to predict

natural frequencies

• Operating conditions gathered

from Quartz Rig testing

• Injector and Rig dimensions taken

from design drawings

• All injector flow paths were

included in a 62 duct model

0.4 0.42 0.44 0.46 0.48 0.5 0.52 0.54 0.56 0.58 0.60

100

200

300

400

500

600

700Natural Frequencies for TPZ=2936,Pilot=6.0%,T2=830

Length of variable length section [m]

Fre

quency [

Hz]

Software Validation

Oscillation measurements were

recorded during various operating

conditions

Conditions Varied:

•% Pilot

•% Pressure Drop

•TPZ

•Air Inlet Temp

Test Results

TPZ (F) T2 (F) % Pilot % PD 1st Harmonic (Hz) 2nd Harmonic (Hz)

3114 767 3.98 3.94 335 674

3107 774 5.97 4.03 337 673

3019 774 4.04 3.8 330 661

3000 798 5.90 3.75 336 671

2996 717 5.44 3.49 326 652

2962 739 5.87 3.25 325 641

2936 830 6.00 2.57 329 657

2916 788 4.05 3.04 325 651

62 Duct Model Results

328 Hz

640 Hz

Non-excited

Frequencies

Validation Conclusions

Potential reasons for disagreement:

•Currently, the software only considers one dimensional flow in the

longitudinal direction

Sound could be traveling radially and circumferentially throughout

the rig and injector

•Geometry input; flow paths could be better approximated using ProE

•Operating conditions data could be skewed due to the oscillations

Statistical Analysis

Smallest 1st Harm Error Largest 1st Harm Error Average 1st Harm Error 1st Harm StDev

1 Hz 36.7 Hz 15.4 Hz 12.3

Smallest 2nd Harm Error Largest 2nd Harm Error Average 2nd Harm Error 2nd Harm StDev

8.8 Hz 57.8 Hz 30.0 Hz 17.1

Rig Sensitivity Study

Solid Fuel Line

Braided Fuel Line

•Oscillations during the solid line tests were weaker than during the braided

line tests

•Solid lines also produced a more consistent tone for the first and second

harmonic

•The model was more sensitive to changes in the affective area of fuel and air

lines compared to the affective area of the plenum

•Oscillations differed when the pilot fuel line did not contain an orifice

Quartz Rig tests were conducted with solid and

braided fuel lines to determine the effect on

acoustic response

Type Average Amp (psi) Max Frequency (Hz) Min Frequency (Hz) Range (Hz)

Solid lines 0.260 337 325 12

Braided lines 0.361 339 298 41

Average Amp (psi) Max Frequency (Hz) Min Frequency (Hz) Range (Hz)

Solid lines 0.0175 674 641 33

Braided lines 0.02 678 596 82

First Harmonic

Second Harmonic

Summary of Contributions

Successful “break and fix” exercise that yielded software improvements

A document of suggestions to make the software more user friendly

and easier to use for employees who aren’t acoustic experts

Thermo-acoustic network frequency prediction validation

Rig sensitivity study

Insight on incorporating Thermo-acoustic Network software into

PDTools

Proposed Future Objectives

1) Continue to validate the software once it is capable of predicting which natural

frequencies will resonate

2) Use the software to predict not only longitudinal instabilities but radial and

circumferential instabilities as well

3) Use the software to study the acoustic instabilities in an annular rig configuration

4) Use this information to counter oscillations and design a more environmentally

friendly gas turbine

Single Injector Model

Annular Model

What I’ve Learned

•Causes and effects of combustion instabilities

•Industry application of what I learned while earning

my Bachelor’s Degree

•Importance of communication and big picture outlook

in a team oriented environment

•Matlab experience

•Reassurance in the career path that I have chosen

Summer Fun!

Special Thanks

Thanks to Solar Turbines Incorporated and all the people who were involved in

giving me this opportunity to contribute and gain knowledge in the field that I am passionate

about.

The Combustion Group, especially Andy Luts, Mel Noble, Ram Srinivasan, Sean

Spivey, Gary Oskam, and Jim Blust

The interns, recent rotation grads, and Toni Johnson who have all helped make this summer

in San Diego an amazing experience

Questions?