1. Combustor Technology Turbo Power programme conference, 9 April 2014
Bernhard Gustafsson
GKN Aerospace Engine Systems, Aerothermodynamics
Daniel Lörstad
Siemens Industrial Turbomachinery, Combustion Group

2. Outline Turbo Power goals related to the COMB area
Future combustor requirements
Syngas
Gas turbine competitiveness, R&D hot topics
Overview of a Combustor Development Process
GKN Combustion activities
COMB past and present projects

3. Excerpts from Turbo Power goals
Turbo Power requirements related to COMB:
Improved tools and modelling capabilities
Enable fuel flexibility
Increase knowledge within renewable low-caloric value gases and liquid bio-fuels.
Increase design space, design capability and flexibility.
Produce generic knowledge that can be applied to product development and commercialisation.

4. Flexible combustors for sustainable energy production
Future combustors must be able to handle fuels from different sources and with different properties and compositions.
Fuel-flexible combustion (process-controlled combustion).
Possibilities to use low-calorific fuels from biomass. Usually a CO – H2 mixture.
Flexible operation. Combustors must be able to operate at varying loads. Waste gases, peak loads etc.
Allow exhaust gas recirculation (EGR) to facilitate carbon capture and sequestration (CCS) processing. High CO2 levels.
All this in a safe, clean and efficient manner.

5. Syngas
Synthesis gas (syngas) consists of H2, CO and some CO2 and inert.
Intermediate gas in producing synthetic natural gas
Can be produced by gasification of biomass
Combustion challenges with syngas are:
Low heating value causes high mass flow through the combustor, and possibly flame extinction.
High laminar flame speed of H2 can cause flash-back
Higher temperature at stoichiometric combustion than NG produces more NOx. Rich or lean combustion is needed, but is more prone to instabilities.

6. Gas turbine competitiveness R&D hot topics
Efficiency
High turbine inlet temperature and effective cooling
Knowledge of turbine inlet depends on combustor knowledge
Reliability, availability and life
Combustion instabilities may lead to fatigue failure
Total life cycle cost
Emission levels
Low NOx requires limited flame zone temperature and well mixed air/fuel
Reduced NOx often leads to instabilities & increased CO/UHC
Ability of flexibility
Gas/liquid fuel type and energy content strongly influences the combustion
Load flexibility to back up renewables
SGT-750
37 MW, 40%
Launched nov 2010
Data Power Efficiency
Shaft 37.1 MW %
Electric MW %
Combi 47.7 MW %
High availability
High serviceability
Environmentally friendly

7. Common questions in R&D projects
SGT-800
Performance
Life
Heat load & temperature
Turbine inlet distribution
Availability & reliability
Combustion dynamics
Thermo acoustics
Emissions: NOx, CO, UHC
Alternative fuels
Cost
Answers obtained through experience, modeling, rig and engine tests
There is a need of increased accuracy of predictions to optimize the design potential and reduce lead time and costs
Combustor flow paths, flame position and recirculation zones

8. Overview of Combustor Development Process
Aero-combustion analysis
Testing
Mechanical integrity
and design
Concept
Concept
analysis
0.1-1MSEK
Basic
CFD
AC testing
Basic
Mechanical Design
Generic development process
1-20MSEK
Detailed analyses (Complex CFD/acoustics/ chemistry)
Mechanical integrity
(heat trans/stress/life)
HP testing
Detailed
Available budget for analyses depends on risks of:
Not reaching goals
Delays & increased budget
Additional test periods
1-100MSEK
Engine testing
Proto-type design
Validation

9. GKN Combustion activities
RM12 main combustion chamber and afterburner
Space nozzle extensions
Acoustic treatments in combustors and ducts

10. COMB past and present projects
Analysis of thermo-acoustic properties of combustors including liner wall modeling (COMB24) G. Jourdain & L.-E. Eriksson. Chalmers (COMPLETED)
CFD Modeling of Flexi-Fuel Gas Turbine Combustor (COMB25 ) A. Abou-Taouk & L.-E. Eriksson. Chalmers (ONGOING)
Prediction of gas turbine combustor performance based on optimal reduced kinetics and dynamic mode decomposition (COMBxx) ?. ? , N. Andersson & L.-E. Eriksson. Chalmers (NEW)
Experimental investigation of flexible combustion at atmospheric and elevated pressure. (COMB26) I. Sigfrid, R. Whiddon, A. Kundu, A. A. Subash, R. Collin, J. Klingmann & M. Aldén. Lund University of Tech. (ONGOING)

11. Combustion instabilities
Fuel-Oxidator ratio
Residence time
Temperature
Heat release that couple, and that is in phase with, acoustic or hydrodynamic modes casues instabilities to grow.
Fatigue and (catastrophic) failure of the combustor
Heat release
Acoustic / Hydrodynamic eigenmode P V P T f
Disturbance

12. COMB 24 / Validation Rig 1 (1990)
Buzz
Screech
Premixed propane flame behind a triangular flameholder

13. Modelling techniques studied in COMB
Dynamic Mode Decomposition
Snap-shots of the flow field
Extraction of dominant dynamic modes
Extraction of eigenvalues => frequency and damping
Optimal global reaction schemes
Reduction of detailed reaction schemes for syngas and methane
Few global reactions => suitable for unstready 3D CFD (LES)
Multi-target optimised reaction schemes w.r.t.
adiabatic flame temperature
laminar flame speed
Perfectly Stirred Reactor effluents
Flame thickness and species distribution in the flame

14. COMB 24 Eigenmode analysis of Validation Rig 1
Arnoldi method
Linear Euler Equations
Linear Navier Stokes Equations
Dynamic Mode Decomposition
Unsteady RANS
Development of porous wall model for acoustic damping
Arnoldi, damped mode
DMD, undamped (correct)
Incl. porous wall, damped

15. COMB 25 Unsteady 3D CFD (Hybrid URANS/LES)
Temperature
Unsteady 3D CFD (Hybrid URANS/LES)
Optimization of global reaction schemes
4 global reactions sensitized to local fuel-air ratio
Flame position is maintained by swirl
Methane-Air mixture f=0.55
Large Eddy Simulations of an industrial burner, SGT-100, fed with Methane-Air. (A. Abou-Taouk)
Reaction rate

16. High pressure rig - DESS
COMB 26
Atmospheric rig
Atmospheric testing & High pressure testing (DESS):
Siemens RPL pilot burner
Siemens DLE burner
Simulated low-heating value fuels by dilution of inert
Advanced non-intrusive measurement techniques:
Gas analysis - emissions
Particle Image Velocimetry
Laser induced fluorescence of OH and formaldehyde
Chemiluminescence
High pressure rig - DESS
from R. Whiddon (2014)

17. COMB 26
from R. Whiddon (2014)

18. END