Person to person droplets transmission characteristics in unidirectional ventilated protective isolation room: The impact of initial droplet size

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.

Download Full-text

Effect of the multiphase composition in a premixed fuel–air stream on wedge-induced oblique detonation stabilisation

Journal of Fluid Mechanics ◽

10.1017/jfm.2018.289 ◽

2018 ◽

Vol 846 ◽

pp. 411-427 ◽

Cited By ~ 13

Author(s):

Zhaoxin Ren ◽

Bing Wang ◽

Gaoming Xiang ◽

Longxi Zheng

Keyword(s):

Detonation Wave ◽

Droplet Size ◽

Oblique Shock ◽

Smooth Transition ◽

Oblique Shock Wave ◽

Two Phase ◽

Transition Pressure ◽

Initial Droplet ◽

Oblique Detonation Wave ◽

Initial Droplet Size

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.

Download Full-text