scholarly journals Large eddy simulation of soot formation and oxidation for different ambient temperatures and oxygen levels

2022 ◽  
Vol 306 ◽  
pp. 118094
Author(s):  
Min Zhang ◽  
Jiun Cai Ong ◽  
Kar Mun Pang ◽  
Xue-Song Bai ◽  
Jens H. Walther
2020 ◽  
Vol 279 ◽  
pp. 115774 ◽  
Author(s):  
Shijie Xu ◽  
Shenghui Zhong ◽  
Kar Mun Pang ◽  
Senbin Yu ◽  
Mehdi Jangi ◽  
...  

Fuel ◽  
2022 ◽  
Vol 313 ◽  
pp. 122735
Author(s):  
Jiun Cai Ong ◽  
Min Zhang ◽  
Morten Skov Jensen ◽  
Jens Honoré Walther

Author(s):  
Jean Lamouroux ◽  
Stéphane Richard ◽  
Quentin Malé ◽  
Gabriel Staffelbach ◽  
Antoine Dauptain ◽  
...  

Nowadays, models predicting soot emissions are, neither able to describe correctly fine effects of technological changes on sooting trends nor sufficiently validated at relevant operating conditions to match design office quantification needs. Yet, phenomenological descriptions of soot formation, containing key ingredients for soot modeling exist in the literature, such as the well-known Leung et al. model (Combust Flame 1991). This approach indeed includes contributions of nucleation, surface growth, coagulation, oxidation and thermophoretic transport of soot. When blindly applied to aeronautical combustors for different operating conditions, this model fails to hierarchize operating points compared to experimental measurements. The objective of this work is to propose an extension of the Leung model, including an identification of its constants over a wide range of condition relevant of gas turbines operation. Today, the identification process can hardly be based on laboratory flames since few detailed experimental data are available for heavy-fuels at high pressure. Thus, it is decided to directly target smoke number values measured at the engine exhaust for a variety of combustors and operating conditions from idling to take-off. A Large Eddy Simulation approach is retained for its intrinsic ability to reproduce finely unsteady behavior, mixing and intermittency. In this framework, The Leung model for soot is coupled to the TFLES model for combustion. It is shown that pressure-sensitive laws for the modelling constant of the soot surface chemistry are sufficient to reproduce engine emissions. Grid convergence is carried out to verify the robustness of the proposed approach. Several cases are then computed blindly to assess the prediction capabilities of the extended model. This study paves the way for the systematic use of a high fidelity tool solution in design office constraints for combustion chamber development.


2020 ◽  
Vol 215 ◽  
pp. 51-65 ◽  
Author(s):  
Bulut Tekgül ◽  
Heikki Kahila ◽  
Ossi Kaario ◽  
Ville Vuorinen

Author(s):  
Andrea Giusti ◽  
Epaminondas Mastorakos ◽  
Christoph Hassa ◽  
Johannes Heinze ◽  
Eggert Magens ◽  
...  

In this work, a single sector lean burn model combustor operating in pilot only mode has been investigated using both experiments and computations with the main objective of analyzing the flame structure and soot formation at conditions relevant to aero-engine applications. Numerical simulations were performed using the large eddy simulation (LES) approach and the conditional moment closure (CMC) combustion model with detailed chemistry and a two-equation model for soot. The CMC model is based on the time-resolved solution of the local flame structure and allows to directly take into account the phenomena associated to molecular mixing and turbulent transport, which are of great importance for the prediction of emissions. The rig investigated in this work, called big optical single sector rig, allows to test real scale lean burn injectors. Experiments, performed at elevated pressure and temperature, corresponding to engine conditions at part load, include planar laser-induced fluorescence of OH (OH-PLIF) and phase Doppler anemometry (PDA) and have been complemented with new laser-induced incandescence (LII) measurements for soot location. The wide range of measurements available allows a comprehensive analysis of the primary combustion region and can be exploited to further assess and validate the LES/CMC approach to capture the flame behavior at engine conditions. It is shown that the LES/CMC approach is able to predict the main characteristics of the flame with a good agreement with the experiment in terms of flame shape, spray characteristics and soot location. Finite-rate chemistry effects appear to be very important in the region close to the injection location leading to the lift-off of the flame. Low levels of soot are observed immediately downstream of the injector exit, where a high amount of vaporized fuel is still present. Further downstream, the fuel vapor disappears quite quickly and an extended region characterized by the presence of pyrolysis products and soot precursors is observed. The strong production of soot precursors together with high soot surface growth rates lead to high values of soot volume fraction in locations consistent with the experiment. Soot oxidation is also very important in the downstream region resulting in a decrease of the soot level at the combustor exit. The results show a very promising capability of the LES/CMC approach to capture the main characteristics of the flame, soot formation, and location at engine relevant conditions. More advanced soot models will be considered in future work in order to improve the quantitative prediction of the soot level.


Author(s):  
Aniket R. Inamdar ◽  
Sanjiva K. Lele ◽  
Mark Z. Jacobson

This study uses a Fickian-Distribution parameterization [Chen & Lamb, 1994] to model the effects of ice habits on contrail formation within a large eddy simulation (LES). Box model cases were first performed at various ambient temperatures and relative humidities over ice (RHi) and results compared with available laboratory data of ice crystal growth and habit distribution [Bailey & Hallett, 2004]. The model was then used in a full 3-D LES of contrails and results were compared with in-situ observations [Febvre et. al., 2009]. Comparisons are also made with results from simulations that used a probabilistic ice habit model [Inamdar et. al., 2013].


Author(s):  
Heeseok Koo ◽  
Malik Hassanaly ◽  
Venkat Raman ◽  
Michael E. Mueller ◽  
Klaus Peter Geigle

The computational modeling of soot in aircraft engines is a formidable challenge, not only due to the multiscale interactions with the turbulent combustion process but the equally complex physical and chemical processes that drive the conversion of gas-phase fuel molecules into solid-phase particles. In particular, soot formation is highly sensitive to the gas-phase composition and temporal fluctuations in a turbulent background flow. In this work, a large-eddy simulation (LES) framework is used to study the soot formation in a model aircraft combustor with swirl-based fuel and air injection. Two different configurations are simulated: one with and one without secondary oxidation jets. Specific attention is paid to the LES numerical implementation such that the discrete solver minimizes the dissipation of kinetic energy. Simulation of the model combustor shows that the LES approach captures the two recirculation zones necessary for flame stabilization very accurately. Further, the model reasonably predicts the temperature profiles inside the combustor. The model also captures variation in soot volume fraction with global equivalence ratio. The structure of the soot field suggests that when secondary oxidation jets are present, the inner recirculation region becomes fuel lean, and soot generation is completely suppressed. Further, the soot field is highly intermittent suggesting that a very restrictive set of gas-phase conditions promotes soot generation.


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