Using steam as heat carrier and working media has merits to increase electric efficiency up to 60% and decrease NOx emission to single-digit compared to dry gas turbine cycles. These attribute to the physical properties of steam as having high heat capacity to reduce local flame temperature, and hence reduce emissions by inhibiting thermal NOx forward reaction rate. In this work, ultra-high steam content with steam-to-air mass ratio up to 40% is premixed with methane air mixture before entering a swirl-stabilized HP-burner for combustion. Significant change of flame from V-shape (attached) to M shape (detached) is observed through a transparent combustion chamber. The measurement of chemiluminescence OH* is conducted with an intensified CCD-camera band-pass filtered at 320nm. Large eddy simulation is used to capture reacting flow features. Reasonably well agreements between experimental data and numerical results are obtained for both attached and detached flames in terms of OH* distribution. Distributed flame front is clearly identified with LES for wet methane combustion associated with 35% steam-to-air ratio corresponding to a high Karlovitz number flame. Slightly unstable combustion is observed when steam-to-air ratio exceeds 40% featuring an onset of flame blow-off. Interaction between precessing vortex core and the flame is presented at different level of steam dilution, and conclusions are drawn regarding flame stabilization. The in-depth understanding of ultra-wet combustion is an important step towards the use of sustainable, steam-diluted bio-syngas for electricity production.
Impact of diagonal swirler vane angle on combustion dynamic and NOx formation characteristic in a hybrid industrial combustor is numerically studied using a full compressible large eddy simulation approach. The predicted results show that increase the swirler vane angle enlarges the magnitude of the CTRZ and thus the coherent structure and off-axis motions of vortex cores which increase the pressure oscillations amplitude. Phenomenon of combustion instability does not occur due to the introduction of pilot diffusion flame. Formation rate of NOx is relatively slower in pilot diffusion flame, because excess air contained in pilot fuel streams dilutes the flame temperature. Regions with peak flame temperature and maximum formation rate of NOx located in vicinity to the sidewall of combustion chamber especially in the shell side. Proper increase of diagonal swirler vane angle to enlarges the divergence angle of flame and reduces the recirculation of hot gases and combustion products in outer recirculation zones to control peak temperature of flame is an effective means to control NOx emissions for this hybrid industrial combustor. Further increase the diagonal swirler vane angle will have relatively smaller impacts on compressing the NOx emission due to the confinement of combustion chamber.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.