Pre-Chamber Ignition A road towards High Efficiency Natural Gas Engines

1. Pre-Chamber IgnitionA road towards High Efficiency Natural Gas Engines Ashish Shah, Per Tunestål and Bengt JohanssonLund University, Sweden Energirelaterad fordonsforskning 2014 2014-10-08 Gothenberg, Sweden

2. Outline • Introduction • Motivation and relevance • Past activities and results obtained • Future plans

3. Introduction • Administrative details of the project

4. Introduction (cont.) • Aim – Develop combustion strategies for internal combustion engines operating on gaseous fuels for heavy duty applications with comparable or better fuel efficiency and operating load range than diesel counterparts • Current focus is on study of alternative ignition techniques for heavy duty natural gas engines with the following objectives: • Extend the limit of combustion dilution with excess air, Exhaust Gas Recirculation (EGR) or both. • Increase the maximum operating load

5. Motivation and Relevance • Natural Gas – an attractive alternative fuel • Lower specific CO2 emissions • Availability – naturally occurring and renewable alternatives (e.g. biogas etc.) • Variety of applications – heavy duty on-road vehicles (e.g. trucks with LNG), marine engines and power generation (e.g. Wärtsilä and MAN products) • Increasing network on natural gas fueling stations in Sweden and worldwide.

6. Why Pre-chamber ignition? Problems with open chamber spark ignited engines • Simple and cheap • Well developed and mature technology • Limit of dilution with excess air or EGR – combustion instability • High temperature combustion – High heat losses and NOx emissions • Maximum load limited by knock • Knock limited combustion phasing advance – loss in efficiency

7. Why Pre-chamber ignition? Pre-chamber ignition – a possible solution (≈ 5% Vc) • Spatially distributed ignition source • Less affected by cyclic variation of main chamber charge motion • Burning jets provide much higher ignition energy than a spark • Pre-chamber over heating may cause charge pre-ignition • Resulting ignition mechanism is less understood due to its fluid dynamic and chemical kinetic complexities (≈ 95% Vc)

8. Different strategies

9. Experiments and Results obtained so far… 2011 - 2014

10. Experimental Setups

11. Experimental Setups (cont.)

12. Lean limit with excess air

13. Indicated Efficiency

14. NOx emissions

15. Effect of Pre-chamber geometry

16. Effect of Pre-chamber geometry (cont.)

17. Conclusions • A pre-chamber ignition device without additional fueling reduces cyclic variations of combustion event but is not capable of considerably extending the lean limit. • A pre-chamber with additional fueling can considerably extend the lean limit of operation and hence improve indicated efficiency and reduces NOx emissions • A larger pre-chamber provides higher ignition energy but size is limited by fraction of pre-chamber combustion before main chamber ignition.

18. Future Plans • Study pre-chamber ignition at full load conditions (IMEPg > 20 bar) • CFD simulations of pre-chamber jets based on experimental pressure data to understand ignition mechanism resulting from PC jets • Optical diagnostics of pre-chamber ignition in the Wärtsilä large bore engine through optical access to the main chamber and/or pre-chamber. • Optical diagnostics of knock phenomenon with pre-chamber ignition.

19. Future Plan (cont.)

20. Thank youComments/Questions? Ashish ShahPh.D StudentDivision of Combustion EnginesLund University ashish.shah@energy.lth.se