Effects of swirler vane angle on palm biodiesel/natural gas combustion in swirl-stabilised gas turbine combustor

Combustion characteristics of palm biodiesel/methyl esters (PME) and natural gas (NG) blend were examined using a model gas turbine swirl burner at vane angle (θ) 30°, 45° and 60°. A twin fluid air blast atomiser was utilised for atomising liquid fuel at air-to-liquid ratio (ALR) 2.50. Swirling flow was initiated by using an axial swirler as main air passed through it. Combustible mixture was formed as swirling air flow mixed up with liquid fuel spray at burner outlet. Flame colour for PME/NG was mainly bluish, resembling that of neat PME despite subtle liftoff was observed in PME/NG swirl flames. Flame spectroscopic analysis showed that PME/NG swirl flames were more intense than baseline PME. Furthermore, θ = 60° operation led to significantly lower reaction intensity. Meanwhile, PME/NG combustion with 20%-30% NG input power fraction was observed to lower nitric oxide (NO) emission by a factor of 2.7 when compared with diesel and neat PME in θ = 60° combustion. Novel empirical models for emissions were also proposed, enabling the estimation of NO emission from PME/NG combustion at different NG input power proportions and vane angle. This research shows that PME/NG combustion is a promising way of reducing NO emission against neat PME and diesel in gas turbine operation. Moreover, flame instability provoked by liftoff in dual fuel operation is not aggravated, mainly due to nullification by intensified global reaction when NG is added. Such attributes feature PME/NG as a viable alternative fuel for use in land-based power generation gas turbines.