Numerical Investigation of the Effects of Swirling Hot Co-Flow on MILD Combustion of a Hydrogen–Methane Blend

Abstract

This paper examines the effects of swirl hot co-flow on the combustion behavior of a moderate or intense low oxygen dilution (MILD) burner fueled by a mixture of methane and hydrogen. Toward this goal, the realizable k-ɛ turbulence model, GRI. 2.11 reaction mechanism, and the discrete ordinates radiation model are incorporated into a computational modeling of the reactive flow. The numerical results are, first, favorably compared against the existing experimental data. Subsequently, a number of swirl co-flows are implemented, and structures of the resultant reactive flows are investigated systematically. The outcomes indicate that increasing the swirl velocity leads to the reduction of ignition delay and significantly enhances the reaction completion. The analysis of the spatial distribution of hydroxyl and formyl (OH and HCO) radicals reveals that swirling MILD combustion radially extends the reaction zone in comparison with the conventional MILD combustion. Yet, it reduces the length of the reactive region and allows for the occurrence of heat release in a shorter axial distance from the outlet fuel nozzle. Further, the addition of swirl reduces the production of carbon monoxide through its influences upon flow temperature and generation of formyl radical. However, it is found that swirling hot co-flow intensifies NOx emissions by strengthening of prompt and thermal mechanisms of NOx production. Reducing the temperature of the recycled flue gas is deemed to be an effective way of resolving this issue.

Cooling characteristics of dilution holes in can-type combustor of micro gas turbine

“…Especially when the flame temperature is higher than 1,800 K, the generation rate of thermal NOx is found to increase substantially. 34,35 The Zeldvich 36,37 mechanism that was used in this study has been used and validated by many researchers as the widely accepted mechanism for the generation of thermodynamic NO X , 38–42 and the equation of the reaction process is as follows.…”

On the Response of Ultralean Combustion of CH4/H2 Blends in a Porous Burner to Fluctuations in Fuel Flow—an Experimental Investigation

“…Nonetheless, this still poses a substantial concern, hence there exist active plans for decarbonization of gas grids. , Injection of hydrogen to natural gas pipelines has been identified as a practical approach to reduce carbon emissions. , As a result, in recent years, there has been a surge of research interest in the combustion of hydrogen and methane mixtures, for example, refs , . Although these studies , have provided a wealth of insights into the problem, they are chiefly focused on lean premixed and partially premixed flames . This makes them pertinent to high-temperature applications typically more than 1500 K. There are, however, an increasing number of applications in which high temperatures are not needed, and generation of heat at moderate temperatures is preferred .…”

Numerical Investigation of the Plasma-Assisted MILD Combustion of a CH4/H2 Fuel Blend Under Various Working Conditions

“…Recently, the possibility of improving combustion has been demonstrated through taking different approaches [6][7][8][9][10]. This includes utilizing hybridized solar thermal energy and combustion [11][12][13], novel burner designs [14], swirl injection [15], and changes in the injection parameters [16][17][18][19]. In addition to these, the use of plasma actuators by injecting reactive chemical species has allowed achieving more efficient combustion [20].…”