Comparison of Liquid Fuel/Air Mixing and NOx Emissions for a Tangential Entry Nozzle

Author(s):  
Timothy S. Snyder ◽  
Thomas J. Rosfjord ◽  
John B. McVey ◽  
Louis M. Chiappetta

An experimental program was conducted to develop a technique for designing a dry low NOx liquid fuel injection configuration for a tangential entry lean-premixed fuel nozzle. Calculations were performed to predict the effect of liquid fuel injection location, orifice size and spacing, and initial droplet size on the vaporized fuel/air mixture uniformity exiting the highly-swirled premixing nozzle. Combustion tests were conducted at pressures ranging from 10–18 atm, and inlet temperatures ranging from 650–730 K, for the different liquid fuel injection schemes analyzed from the mixing study. Liquid fuel injection configurations that were predicted to give the best fuel/air distribution generated the lowest levels of NOx. The calculated fuel/air uniformity was a weak function of the spatial density of liquid fuel injection sites and the method of injecting the liquid fuel. The injection location and initial droplet size have the greatest impacts on fuel/air uniformity. The analysis indicated that 40 micron diameter droplets mix adequately while larger droplets (80 micron) are centrifuged out of the main body of the flow and produce locally high fuel/air ratios. The NOx levels achieved for the best liquid fuel injection configuration approached those obtained for a well premixed gas fuel configuration using the same tangential entry nozzle.

Author(s):  
Y. Wang ◽  
L. Reh ◽  
D. Pennell ◽  
D. Winkler ◽  
K. Döbbeling

Stationary gas turbines for power generation are increasingly being equipped with low emission burners. By applying lean premixed combustion techniques for gaseous fuels both NOx and CO emissions can be reduced to extremely low levels (NOx emissions <25vppm, CO emissions <10vppm). Likewise, if analogous premix techniques can be applied to liquid fuels (diesel oil, Oil No.2, etc.) in gas-fired burners, similar low level emissions when burning oils are possible. For gas turbines which operate with liquid fuel or in dual fuel operation, VPL (Vaporised Premixed Lean)-combustion is essential for obtaining minimal NOx-emissions. An option is to vaporise the liquid fuel in a separate fuel vaporiser and subsequently supply the fuel vapour to the natural gas fuel injection system; this has not been investigated for gas turbine combustion in the past. This paper presents experimental results of atmospheric and high-pressure combustion tests using research premix burners running on vaporised liquid fuel. The following processes were investigated: • evaporation and partial decomposition of the liquid fuel (Oil No.2); • utilisation of low pressure exhaust gases to externally heat the high pressure fuel vaporiser; • operation of ABB premix-burners (EV burners) with vaporised Oil No.2; • combustion characteristics at pressures up to 25bar. Atmospheric VPL-combustion tests using Oil No.2 in ABB EV-burners under simulated gas turbine conditions have successfully produced emissions of NOx below 20vppm and of CO below 10vppm (corrected to 15% O2). 5vppm of these NOx values result from fuel bound nitrogen. Little dependence of these emissions on combustion pressure bas been observed. The techniques employed also ensured combustion with a stable non luminous (blue) flame during transition from gaseous to vaporised fuel. Additionally, no soot accumulation was detectable during combustion.


2018 ◽  
Vol 846 ◽  
pp. 411-427 ◽  
Author(s):  
Zhaoxin Ren ◽  
Bing Wang ◽  
Gaoming Xiang ◽  
Longxi Zheng

An oblique detonation wave in two-phase kerosene–air mixtures over a wedge is numerically studied for the first time. The features of initiation and stabilisation of the two-phase oblique detonation are emphasised, and they are different from those in previous studies on single-phase gaseous detonation. The gas–droplet reacting flow system is solved by means of a hybrid Eulerian–Lagrangian method. The two-way coupling for the interphase interactions is carefully considered using a particle-in-cell model. For discretisation of the governing equations of the gas phase, a WENO-CU6 scheme (Hu et al., J. Comput. Phys., vol. 229 (23), 2010, pp. 8952–8965) and a sixth-order compact scheme are employed for the convective terms and the diffusive terms, respectively. The inflow parameters are chosen properly from real flight conditions. The fuel vapour, droplets and their mixture are taken as the fuel in homogeneous streams with a stoichiometric ratio, respectively. The effects of evaporating droplets and initial droplet size on the initiation, transition from oblique shock to detonation and stabilisation are elucidated. The two-phase oblique detonation wave is stabilised from the oblique shock wave induced by the wedge. As the mass flow rate of droplets increases, a shift from a smooth transition with a curved shock to an abrupt one with a multi-wave point is found, and the initiation length of the oblique detonation increases, which is associated with the increase of the transition pressure. By increasing the initial droplet size, a smooth transition pattern is observed, even if the equivalence ratio remains constant, and the transition pressure decreases. The factor responsible is incomplete evaporation before the detonation fronts, which results in a complicated flame structure, including regimes of formation of oblique detonation, evaporative cooling of droplets and post-detonation reaction.


2005 ◽  
Vol 18 (4-6) ◽  
pp. 433-442
Author(s):  
Jean-Pierre Bigot ◽  
Abdellah Touil ◽  
Patrick Bonnet ◽  
Jean-Marc Lacôme

2016 ◽  
Vol 81 (5) ◽  
pp. E1124-E1129 ◽  
Author(s):  
Chutima Thongkaew ◽  
Benjamin Zeeb ◽  
Monika Gibis ◽  
Jörg Hinrichs ◽  
Jochen Weiss

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