combustion modelling
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2021 ◽  
Vol 13 (2-3) ◽  
pp. 146-163
Author(s):  
Alejandro Aljure Osorio ◽  
Xavier Tauzia ◽  
Alain Maiboom

Diesel engines are becoming smaller as technology advances, which means that the fuel spray (or jet) interacts with the cylinder walls before combustion starts. Most fuel injection 1D models (especially for diesel fuel) do not consider this interaction. Therefore, a wall-jet sub-model was created on an Eulerian 1D diesel spray model. It was calibrated using data from the literature and validated with experimental data from a fuel spray impacting a plate in a constant volume combustion chamber. Results show that the spray moving along the wall has a higher mixing rate but less penetration as an equivalent free jet, therefore they show a similar volume. Spray-wall interaction creates a stagnation zone right before the impact with the wall, and friction of the jet with the wall is relatively low. All these phenomena are well captured by the wall-jet sub-model.


Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6732
Author(s):  
Santiago Molina ◽  
Ricardo Novella ◽  
Josep Gomez-Soriano ◽  
Miguel Olcina-Girona

The achievement of a carbon-free emissions economy is one of the main goals to reduce climate change and its negative effects. Scientists and technological improvements have followed this trend, improving efficiency, and reducing carbon and other compounds that foment climate change. Since the main contributor of these emissions is transportation, detaching this sector from fossil fuels is a necessary step towards an environmentally friendly future. Therefore, an evaluation of alternative fuels will be needed to find a suitable replacement for traditional fossil-based fuels. In this scenario, hydrogen appears as a possible solution. However, the existence of the drawbacks associated with the application of H2-ICE redirects the solution to dual-fuel strategies, which consist of mixing different fuels, to reduce negative aspects of their separate use while enhancing the benefits. In this work, a new combustion modelling approach based on machine learning (ML) modeling is proposed for predicting the burning rate of different mixtures of methane (CH4) and hydrogen (H2). Laminar flame speed calculations have been performed to train the ML model, finding a faster way to obtain good results in comparison with actual models applied to SI engines in the virtual engine model framework.


2021 ◽  
pp. 146808742110371
Author(s):  
Mattia Olcuire ◽  
Clara Iacovano ◽  
Alessandro d’Adamo ◽  
Sebastiano Breda ◽  
Tommaso Lucchini ◽  
...  

Turbulent jet ignition is seen as one of the most promising strategies to achieve stable lean-burn operation in modern spark-ignition engines thanks to its ability to promote rapid combustion. A nearly stoichiometric mixture is ignited in a small-volume pre-chamber, following which multiple hot turbulent jets are discharged in the main chamber to initiate combustion. In the present work, a detailed computational investigation on the turbulent combustion regime of premixed rich propane/air mixture in a quiescent divided chamber vessel is carried out, to study the characteristics of the jet flame without the uncertainties in mixing and turbulent conditions typical of real-engine operations. In particular, the paper investigates the dependency of flame propagation on nozzle diameter (4, 6, 8, 12 and 14 mm) and pre-chamber/main-chamber volume ratio (10% and 20%); CFD results are compared to the experimental outcomes. Results show that the combustion regime in the quiescent pre-chamber follows a well-stirred reaction mode, rendering the limitation in using conventional flamelet combustion models. Furthermore, due to the very high turbulence levels generated by the outflowing reacting jets, also the main chamber combustion develops in a well-stirred reactor type, confirming the need for a kinetics-based approach to combustion modelling. However, the picture is complicated by thickened flamelet conditions possibly being verified for some geometrical variations (nozzle diameter and pre-chamber volume). The results show a general good alignment with the experimental data in terms of both jet phasing and combustion duration, offering a renewed guideline for combustion simulations under quiescent and low Damköhler number conditions.


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