Low Emission GT Combustors

1. Low Emission GT Combustors R. Balachandran r.balachandran@ucl.ac.uk Department of Mechanical Engineering, University College London, Torrington Place, London, United Kingdom, WC1E 7JE

2. Ultra Low Emission Engines • Renewables gaining importance: Fossil fuels will continue to be the main stay. • Options to achieve low emissions: • Lean Burn technology • Carbon Capture (Pre-Combustion and Post-Combustion) • Efficiency improvements through novel component/system designs • Future fuels: Renewables, fuel flexibility, synthetic future fuels

3. Low emission GT engines • Ultra Low emission in aero/industrial GT combustors: • Lean premixed combustion: common approach • Low flame temperature • High fuel efficiency • Susceptible to combustion oscillations, resulting in complete plant meltdown • Flame blowout • Low emission option for land based power generation: • Integrated Gasification Combined Cycle (IGCC) • Coal, Biomass utilisation (reducing Natural gas dependence) • Fuel flexibility • CCS capability • Flame behaviour changes due to change in fuel properties (Hydrogen enriched fuels) resulting in unsteady combustion • Initial and operational cost

4. Overview of GT combustion research @UCL • Turbulent combustion • Unsteady Combustion • Fundamental flame behaviour in the presence and absence of flow perturbations • Hydrogen enrichment for combustion dynamics control • Fuel flexible combustor • Sustainable fuel (Biogas, Syngas, H2 ) • Ignition, Flame stabilisation and stability • Emission characteristics • Development of sensors and laser diagnostics techniques for flow and flame • Multi-scalar imaging to investigate local heat release • Fuel LIF, IR and chemiluminescence sensors to study mixing field • 3D PIV, Highspeed imaging for flow field characterisation

5. Combustion Oscillations in GT combustors: Feedback Mechanism p’ Flame area, Heat of reaction, Flame speed Q’ Rayleigh criteria Combustion Chamber mreactants u’, ’ Fuel properties • Amplification or attenuation of the pressure oscillation by heat addition would occur if the periodic heat release occurs in or out of phase with the pressure oscillation, respectively. • where, • p - pressure Q - heat addition • x - location t - time • T - period of the oscillation V - volume of interest • Li - i-th wave energy dissipation process Putnam & Dennis (1953)

6. Model GT Combustor @UCL • Choked fuel injection through central pipe to achieve partial premixing 80 mm Based on RB12 (Rolls-Royce combustor) Diameter of the Air passage =35 mm Bluff body diameter = 25 mm Diameter of Enclosure =70 mm • Acoustic velocity determined using the two-microphone technique and calibrated against hotwire measurements under cold flow conditions Key features: High Reynolds number, High Swirl (Vane and Tangential flow induced) Fuel flexibility, Combustion modes: premixed, partially-premixed, non-premixed • Fuel sensitivity to flow perturbations

7. Multi-scalar Imaging for combustion • Schematic and picture of the laser imaging facility used for PLIF measurements • For sequential OH PLIF, both the laser were tuned near 283 nm • The double exposure option of ICCD was used to capture OH* chemiluminescence

8. OH OH OH CH2O CH2O CH2O HR HR HR (d) (b) (c) (a) Heat-release Imaging: Premixed combustion • Spatially and temporally resolved heat release images • Investigation of flame vortex interaction in a fully premixed flame applicable to Lean Prevaporised Premixed GT combustors

9. Phase averaged PLIF imaging • Capture periodic variation in flame behaviour • Appearance of vortex decreases the global heat release estimate from this technique suggesting flame annihilation • The flame behaviour mimics self-excitation in practical combustors

10. Non-linear Flame response • Nonlinear response to inlet perturbations

11. Sequential OH PLIF capability t = 0 t = 1 ms t = 2 ms t = 3 ms • Four laser pulses illuminated premixed flame of  =0.55separated by 1 ms; resulting time resolved OH PLIF realisations shows flame surface annihilation; U =9.9 m/s, A~0.5 • These results enable better flame dynamics modelling for combustion instability prediction

12. Future Low Emission Micro-engines • Increased interest in milli-to-watt range power generation due to increased demand for MEMS (Micro Electro Mechanical Systems). • The potential of exploiting the high specific energy of hydrocarbon fuels, typically 50 - 100 times that of top range batteries currently in the market, [1], by means of micro combustion. • Versatility of combustion based, integrated systems in providing heat generation and power (Combined Heat and Power) and fuels (hydrogen from reforming) • Potential application • Personal power pack for rescue workers in disaster zone where use of battery is limited • Military application, particularly for soldiers • Laptops • Issues hindering development • high surface area to volume ratio characteristic of micro-combustors unfavourably enhances heat loss to the combustor walls, increasing near-wall destruction of radical species • Lack of efficient power generation at this scale

13. Micro combustor development at UCL • First operational micro-combustion in UK • Dimension of the combustion channel: 1 mm x 3 mm x 27 mm. • Cold start capability, no preheating required • Wide operating range and good optical access • Further research underway to develop integrated combustion systems for heat and power generation Flame speed measured between different locations

14. My Interests • Non-linear/non-normal growth of instabilities • Flame – flow interactions >> extinction/blowout • Dynamics of flames with heat loss

15. Sponsors

16. Acknowledgements • Prof Ladommatos of UCL, Prof. E. Mastorakos, Prof. A. P. Dowling, Dr N. Swaminathan, Dr. R. S. Cant, Dr. B.O. Ayoola, Dr G. Hartung & Dr. C.F. Kaminski, University of Cambridge.

17. Thank you!