Pressure Gain Combustion (PGC) offers a means of improving gas turbine thermal efficiency that can be combined with, and thus surpass gains available from higher turbine inlet temperatures alone. Conventional gas turbine combustion relies on deflagration in an idealized constant pressure combustion process that in reality is subject to a pressure loss. However, PGC achieved through detonation, provides an alternative pathway to similar combustion temperatures but with less entropy generation, and because of the gain in pressure, more work availability. Utilizing a Rotating Detonation Combustor (RDC), it is possible to achieve a near continuous detonation wave that propagates circumferentially in an annular combustor with bulk axial flow that is conducive to a conventional turbine design. In addition to high thermal efficiency, industrial and power generation turbines burning coal syngas in air or natural gas in air must also adhere to strict oxide of nitrogen (NOx) emissions.
The focus of this study is to explore, both experimentally and numerically, NOx emissions from an RDC operating on hydrogen (coal syngas) in air and natural gas/hydrogen in air. Due to short residence times within the detonation wave and rapid expansion downstream of the wave, the production of NOx has the potential to be less than a comparable non-premixed, turbulent deflagrative flame. Tests performed in an uncooled RDC with an outer diameter of 152 mm and an annular gap of 7.62 mm were conducted over a range of equivalence ratios (0.7 â 1.0) while collecting NOx and O2 emissions at multiple locations in the exhaust stream. As variations in equivalence ratio induce changes in the modes of wave propagation, it is possible to consider the impact of single versus multiple wave operation on emissions. Experimental results are compared to predicted NOx values attained through a Chemical Reactor Network (CRN) derived from a Computational Fluid Dynamics (CFD) model utilizing chemical kinetics mechanisms tuned for detonation.
