Göran Klose

A Combined Eulerian and Lagrangian Method for Prediction of Evaporating Sprays

Polydisperse sprays in complex three-dimensional flow systems are important in many technical applications. Numerical descriptions of sprays are used to achieve a fast and accurate prediction of complex two-phase flows. The Eulerian and Lagrangian methods are two essentially different approaches for the modeling of disperse two-phase flows. Both methods have been implemented into the same computational fluid dynamics package which is based on a three-dimensional body-fitted finite volume method. Considering sprays represented by a small number of droplet starting conditions, the Eulerian method is clearly superior in terms of computational efficiency. However, with respect to complex polydisperse sprays, the Lagrangian technique gives a higher accuracy. In addition, Lagrangian modeling of secondary effects such as spray-wall interaction enhances the physical description of the two-phase flow. Therefore, in the present approach the Eulerian and the Lagrangian methods have been combined in a hybrid method. The Eulerian method is used to determine a preliminary solution of the two-phase flow field. Subsequently, the Lagrangian method is employed to improve the accuracy of the first solution using detailed sets of initial conditions. Consequently, this combined approach improves the overall convergence behavior of the simulation. In the final section, the advantages of each method are discussed when predicting an evaporating spray in an intake manifold of an internal combustion engine.

Evaluation of Advanced Two-Phase Flow and Combustion Models for Predicting Low Emission Combustors

The development of low emission aero engine combustors strongly depends on the availability of accurate and efficient numerical models. The prediction of the interaction between two-phase flow and chemical combustion is one of the major objectives of the simulation of combustor flows. In this paper, predictions of a swirl stabilized model combustor are compared to experimental data. The computational method is based on an Eulerian two-phase model in conjunction with an Eddy Dissipation (ED) and a presumed-shapePDF (JPDF) combustion model. The combination of an Eulerian two-phase model with a JPDF combustion model is a novelty. It was found to give good agreement to the experimental data.

Comparison of state-of-the-art droplet turbulence interaction models for jet engine combustor conditions

The objective of this paper is to assess three state-of-the-art Lagrangian droplet turbulence interaction models for jet engine combustor operating conditions. The models can be distinguished by their underlying temporal autocorrelation function of the gaseous velocity fluctuations seen by a droplet. Two generic experiments and one realistic test case were used for validation of the models. The analysis of single particle dispersion revealed poor accuracy of the model proposed by Gosman and Ioannides at small Stokes numbers and high relative velocities. The models of Milojevic and of Blumcke gave good agreement with the experimental data. Furthermore, the accuracy of the three models in predicting real polydisperse combustor sprays was studied. It is concluded that the droplet turbulence model does not affect significantly the overall combustor prediction. Finally, characteristic parameters describing monodisperse particle dispersion have been extracted by a numerical study based on the model of Blumcke covering a wide range of combustor operation conditions. These parameters are compared to analytical results of Wang et al.

Low-NOx Combustor Development pursued within the scope of the Engine 3E German national research program in a cooperative effort among engine Manufacturer MTU, University of Karlsruhe and DLR German Aerospace Research Center

Abstract MTU Aero Engines, the University of Karlsruhe and the DLR Aerospace Research Centre co-operated within the scope of the German national aeronautical research program Engine 3E. The program was focused on improving high-bypass turbofan engines. As a part of this program, a low-emission single-annular combustor was developed. The NOx emissions of this combustor are significantly reduced by using the rich-lean combustion concept. The basic idea of this concept is to avoid stoichiometric combustion conditions by splitting the combustion domain into a fuel-rich zone (low-oxygen zone) and a fuel-lean (low temperature zone). The NOx reduction capability of a combustor of this type scales with the homogeneity of the mixture in the rich zone and the time interval needed for the transition from the rich to the lean zone. Based on the insights gained from this cooperative research, an annular combustor was developed and tested at pressures up to 20 bar and inlet temperatures up to 800 K. The tested annular combustor was found to have NOx emissions of about 40% of the ICAO 96 standard. The carbon monoxide and unburned hydrocarbon emissions of the combustor are of about the same levels as present state of the art combustors.