Session: 04-31: Emissions II

Paper Number: 152889

Modeling of Particulate Emissions From Conventional and Sustainable Jet Fuels in Aero Engine Combustors 

Non-CO2 emissions are a main factor contributing to the climatic impact of the aviation sector. Besides greenhouse gaseous emissions (i.e. NOx, UHC), soot particles can act as condensation nuclei for water vapour leading to the formation of condensation trails (contrails).
Regarding the mitigation strategies to reduce emissions, disruptive technologies such as fuel cells or hydrogen combustion are currently explored alongside hybrid-electric propulsion and the use of alternative hydrocarbon-based fuels. The latter, produced from sustainable sources, have similar thermochemical properties to conventional fossil jet fuel and can be used as drop-in fuels in existing aero engines. In addition to reducing net-CO2 emissions, drop-in sustainable aviation fuels (SAFs), especially in the form of synthetic paraffinic kerosene (SPK), can reduce particulate emissions due to their lower aromatic content compared to conventional jet fuel. 
However, studies show that deviations both in overall mass as well as in the particle size distribution (PSD) between conventional jet fuel and SAF depend on the aero engine operating point.
To assess the formation of particulate matter emissions during flight, an evaluation of the total particle mass and the particle size distribution along the flight trajectory is therefore required, including realistic aero engine- and mission-specific boundary conditions from an aero engine performance model.
This drives the necessity to develop models capable of predicting particle emissions from different types of SAFs with reasonable computational time and accuracy.
Following that, this study aims to evaluate the soot volume fraction and the PSD during an aircraft operation by simulating the combustion processes in an aero engine using a chemical reactor network (CRN) model. Here, the combustion chamber is split into the primary, secondary and dilution zone, thus representing rich-burn, quick-quench, lean-burn combustion. Each zone contains a set of perfectly stirred chemical reactors, which are set up to model the heterogeneous mixture regions in the primary zone as well as the mixing of hot gas with dilution and cooling air in the secondary and dilution zone.
A detailed kinetic model that includes gas phase chemistry and soot will be used to simulate combustion and predict soot particle formation. The soot model is based on a discrete section approach and consists of 25 bins, capable of representing heavy polycyclic aromatic hydrocarbons, soot particles and soot aggregates ranging from 1 nm up to 200 nm in equivalent spherical diameter. The CRN model will be calibrated to represent the characteristics of an annular combustion chamber used in modern turbofan engines.
Subsequently, the CRN model will be employed to predict the soot volume fraction and PSD at various aero engine operating points, with the goal of identifying trends along the flight trajectory. Moreover, this work will focus on the comparison of different jet fuel types, including conventional jet fuel as well as SPK produced by the Fischer-Tropsch process. Here, the potential reduction in soot formation and particle diameter when using sustainable fuels as a function of the operating point will be discussed.

Presenting Author: Daniel Lieder TU Braunschweig

Presenting Author Biography: Daniel Lieder commenced his academic career in 2017 as a mechanical engineering student in Bochum, driven by a long-standing passion for science and technology. Upon completion of his Bachelor's degree, he relocated to Braunschweig to pursue his Master's in Aerospace Engineering at the Technical University of Braunschweig. He subsequently commenced his current role at the end of 2023 as a Research Assistant and Doctoral Student at the Institute of Jet Propulsion and Turbomachinery at TU Braunschweig. His current research activities are focused on hybrid electric drive systems and combustion simulation.

Authors:

Daniel Lieder TU Braunschweig
Jan Göing TU Braunschweig
Robert Schmitz TU Braunschweig
Jens Friedrichs TU Braunschweig
Federica Ferraro TU Braunschweig