LAMINAR BURNING SPEED MEASUREMENTS OF HYDROGEN/NATURAL GAS MIXTURES AT 10 ATM

What is it about?

Fossil fuels, when burned in the air, release large amounts of carbon dioxide (CO2) and greenhouse gases (GHG) into the air, causing a significant increase in pollution. To reduce exhaust emission of fossil fuels on the environment, we can use natural gas (NG). Extending the lean burn area similarly reduces emissions of greenhouse gases (CO and CO2) and NOx pollutants. Temperature, pressure, and reactive mixture composition all influence measuring laminar burning speed (LBS). LBS is helpful because it (i) provides a measure of combustion efficiency and heat release rate; (ii) makes it possible to validate chemical kinetic mechanisms; (iii) provides turbine design engineers with a metric for the anticipated amount of time needed to burn the fuel charge. While studies on natural gas and hydrogen combustion under atmospheric conditions exist, very few investigations exist on high pressures in the literature. Here, we report data on observations of natural gas/hydrogen LBS up to an initial pressure of 10 atm and initial temperature of 296 K. To investigate its impact on LBS, a wide range of equivalence ratios were used. As part of the validation procedure for the results, they are also contrasted with the performance of comprehensive kinetic models.

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Why is it important?

In this research, the impact of adding H2 to NG was investigated by igniting pure NG, 70% NG + 30% H2, and 50% NG + 50% H2 in a spherical reactor, maintaining initial conditions of 296 K temperature and 10 atm pressure. The LBS was calculated using pressure data through the constant volume method. Schlieren optical imaging methods were employed to confirm the existence of laminar flame patterns and to enhance the accuracy of LBS estimations. The ideal oxidant mixtures for maintaining laminar flames were identified through historical analysis and practical experiments. The maximum LBSmax for each tested mixture was observed within (ϕ = 1.0 - 1.1). The influence of H2 addition on NG's LBS was examined by comparing the LBS of pure NG with that of H2-enriched NG, revealing that H2 addition led to an increased LBS across all tested equivalence ratios.