Effect of Combustor Geometry on Performance of Airblast Atomizer Under Sub-Atmospheric Conditions

Abstract

ABSTRACT:One of the certification requirements that a jet engine has to fulfil is its altitude relight capability. Relighting an aero gas turbine engine at high altitudes is more challenging than at sea level conditions. The pressure, air velocity, and temperature within the combustor at such conditions are very low, hindering the fuel atomization and evaporation process. After ignition, combustion efficiency can be relatively low due to the poor fuel atomization quality, leading to slow shaft acceleration rates. Further studies in this field can help determine and predict the fuel spray characteristics, which limit the relight and pull-away capability of the engine at these sub-idle conditions. Reported in this paper is the CFD analysis of a typical airblast atomizer, simulated at different sub-idle operating conditions. Two sets of models were used; one with a simple liner-only combustor with co-flow air, and the other with a more detailed geometry, including wall cooling slots, primary and secondary dilution holes, and co-flow air. For the simpler model, three different inner and outer liner wall spacing were modelled to examine the effect of the chamber volume on the fuel spray behaviour. The CFD models were then run at a chamber pressure of 101, 41 and 31kPa, typical of sub-idle conditions. The effect of such conditions on the atomization quality of the fuel spray was analysed. The study carried out indicates how the chamber pressure, chamber volume and AFR (through amount of co-flow air introduced) significantly affect the resulting spray characteristics. A parametric analysis was performed to extract a correlation between the spray SMD (Sauter Mean Diameter) and fuel flow rate.

Experimental Investigation of the Effect of Biodiesel Blends on a DI Diesel Engine’s Injection and Combustion

“…As can be seen, there is an increase of the overall combustion duration from 45 • for B0 to 46.7 • for B20 blend due to higher droplet diameters which lead to slower combustion. The higher the Sauter mean diameter, the less easy it is for a droplet to evaporate [18]. On the other hand, burn duration 0-10% and 0-50% are lower using B20, leading to faster combustion during combustion premixed phase until crank angle of 50% burn point.…”

“…The higher the Sauter mean diameter, the less easy it is for a droplet to evaporate [18]. On the other hand, burn duration 0-10% and 0-50% are lower using B20, leading to faster combustion during combustion premixed phase until crank angle of 50% burn point.…”

Effect of various inlet geometries on swirling flow in can combustor

“…The suitable volumes of air in the liner of the primary, secondary and dilute holes were found to be 22.51%, 22.93% and 54.56%, respectively [11]. However, the volume of combustion chamber did not have an effect on creating CRZ because the air/fuel ratio was still constant [12]. In addition, the turbulence model in this work showed that the turbulence k-ɛ standard gave better results for combustor prediction than other turbulence models [11,13,15,16,17].…”

Influence of Some Geometrical Parameters on the Characteristics of Prefilming Twin-Fluid Atomization

“…Lefebvre and his team obtained series of important achievements on twin-fluid atomizers and proved that twin-fluid atomizers have many advantages over other types of atomizers, since they require lower pump pressures and produce a finer spray [4]. The applications of twin-fluid atomizer are focused on engine combustion [6,7], humidification [8], gas cooling [9], spray painting [10] and spray drying [11], etc.…”