Yilmaz, Harun; Cam, Omer; Yilmaz, Ilker

Swirling flows increase combustion performance via favour-ing flame stability, pollutant emissions, and combustion in-tensity. The strength of a swirling flow is characterized by a parameter known as swirl number, which is highly related to the dh /do ratio. In this study, effects of the swirler dh /do ratio on combustion and emission characteristics of the synthetic gas flames of premixed 20%CNG/30%H2 /30%CO/20%CO2 mix-ture were experimentally investigated in a laboratory-scale swirl stabilized combustor. For this purpose, twelve different swirl generators were designed and manufactured. dh /do ratios of these swirlers were set as 0.30 and 0.50, and the geometric swirl number was varied between the values of 0.4 and 1.4 (at 0.2 intervals). All experiments were conducted at a fuel-lean equivalence ratio (ϕ = 0.6), room temperature, and local at-mospheric conditions of the city of Kayseri, Turkey. A data logger was utilized to plot axial and radial temperatures and NOx, CO, and CO2 profiles, which were exploited to assess combustion and emission performance. Results showed that the dh /do ratio had a non-monotonic effect on the behaviour of combustion and emission of the tested synthetic gas mix-ture. Depending on the swirl number, increments and dec-rements were observed in temperature and emission values. ENERGETIKA. 2021. T. 67. Nr. 1–2. P. 48–54

Yilmaz, Harun; Cam, Omer; Yilmaz, Ilker

In a combustion device, unsteady heat release causes acoustic energy to increase when acoustic damping (energy loss) is not that effective, and, as a result, thermo-acoustic flame instabilities occur. In this study, effects of the swirler dh/do ratio (at different swirl numbers) on dynamic flame behaviour of the premixed 20%CNG/30%H2/30%CO/20%CO2 mixture under externally altered acoustic boundary conditions and stability limits (flashback and blowout equivalence ratios) of such mixture were investigated in a laboratory-scale var-iable geometric swirl number combustor. Therefore, swirl generators with different dh/do ratios (0.3 and 0.5) and geometric swirl numbers (0.4, 0.6, 0.8, 1.0 1.2 and 1.4) were designed and manufactured. Acoustic boundary conditions in the combustion chamber were altered using loudspeakers, and flame response to these conditions was perceived using photodiodes and pressure sensors. Dynamic flame behaviour of respective mixture was evaluated using luminous intensity and pressure profiles. Results showed that the dh/do ratio has a minor impact on dynamic flame behaviour.