Impact of High Hydrogen Operation on Combustor Performance

Abstract

As the interest in high hydrogen operation is gaining momentum, this paper quantifies the impacts associated with switching from natural gas to 100% hydrogen, leveraging both modelling techniques and experimental data. From the modeling standpoint, a perfectly stirred reactor network model was setup in Cantera. Flame speed increases of up to 50 times that of natural gas were observed with increasing hydrogen content, indicating a significant increase in flashback propensity. This suggests that DLE combustion systems might offer an advantage over RQL systems, operating at low equivalence ratios where the flame speed impact is milder. Additionally, the model shows that the blow off time can be used to classify hydrogen operation into three regimes. With increasing hydrogen content, the BOT begins similar to that of propane and declines at different rates in each regime, establishing the added operational challenges associated with high hydrogen content operation. Equivalence ratio dependencies were investigated along with NOx penalties, where a predicted penalty of ∼40–65% was observed within the flame temperature range of 1750–1950K. Experimentally, a new advanced mixer was used, enabling operation of the full spectrum of natural gas and hydrogen blends up to 100% hydrogen. The impact of hydrogen content on NOx emissions for a representative operating condition was investigated. Comparisons with the model predictions were made, revealing discrepancies, which were investigated and justified thru a mixedness and residence time framework. Finally, the authors show that the proper way to regulate future combustors running with 100% hydrogen should be based on NOx and not NOx15. The findings reported here help clarify and shape the future hydrogen enabling technologies, reaffirming the need for compact and shorter combustors than are used in current technologies.