Abstract
The formation of pollutant emissions in jet engines is closely related to the fuel distribution inside the combustor. Hence, the characteristics of the spray formed during primary breakup are of major importance for an accurate prediction of the pollutant emissions. Currently, an Euler–Lagrangian approach for droplet transport in combination with combustion and pollutant formation models is used to predict the pollutant emissions. The missing element for predicting these emissions more accurately is well defined starting conditions for the liquid fuel droplets as they emerge from the fuel nozzle. Recently, it was demonstrated that the primary breakup can be predicted from first principles by the Lagrangian, mesh-free, Smoothed Particle Hydrodynamics (SPH) method. In the present work, 2D Direct Numerical Simulations (DNS) of a planar prefilming airblast atomizer using the SPH method are presented, which capture most of the breakup phenomena known from experiments. Strong links between the ligament breakup and the resulting spray in terms of droplet size, trajectory and velocity are demonstrated. The SPH predictions at elevated pressure conditions resemble quite well the effects observed in experiments. Significant interdependencies between droplet diameter, position and velocity are observed. This encourages to employ such multidimensional interdependence relations as a base for the development of primary atomization models.
Highlights
The design of aircraft propulsion systems, mainly gas turbines, is facing major challenges regarding the reduction of noise, pollutants and greenhouse gas emissions
The reliable prediction of pollutant emissions strongly depends on the precise prediction of the droplet trajectory through the combustion chamber, which is influenced by its starting conditions and the airflow through the atomizer [1]
The Smoothed Particle Hydrodynamics (SPH) method is a mesh-free method that relies on a Lagrangian representation of the fluid by particles moving with the velocity of the fluid
Summary
The design of aircraft propulsion systems, mainly gas turbines, is facing major challenges regarding the reduction of noise, pollutants and greenhouse gas emissions. The combustion chamber of a jet engine is the key component to meet these requirements. The design process of combustion chambers strongly relies on numerical methods, mostly Euler–Lagrangian simulations of the reacting spray. Combined with models for fuel injection, turbulent dispersion, secondary breakup and evaporation of droplets as well as models for combustion and pollutant formation, this approach enables the numerical prediction of pollutant emissions. Pressure, temperature and other parameters, the fuel atomization and the resulting spray have a significant influence on the pollutant formation processes [1]. The reliable prediction of pollutant emissions strongly depends on the precise prediction of the droplet trajectory through the combustion chamber, which is influenced by its starting conditions and the airflow through the atomizer [1]. The interaction of air and fuel droplets can be captured by the Energies 2019, 12, 2835; doi:10.3390/en12142835 www.mdpi.com/journal/energies
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