Investigation of turbulence–chemistry interactions in a heavy-duty diesel engine with a representative interactive linear eddy model

Abstract

Simulations of a heavy-duty diesel engine operated at high-load and low-load conditions were compared to each other, and experimental data in order to evaluate the influence of turbulence–chemistry interactions on heat release, pressure development, flame structure, and temperature development are quantified. A recently developed new combustion model for turbulent diffusion flames called representative interactive linear eddy model which features turbulence–chemistry interaction was compared to a well-stirred reactor model which neglects the influence of turbulent fluctuations on the mean reaction rate. All other aspects regarding the spray combustion simulation like spray break-up, chemical mechanism, and boundary conditions within the combustion chamber were kept the same in both simulations. In this article, representative interactive linear eddy model is extended with a progress variable, which enables the model to account for a flame lift-off and split injection, when it is used for diffusion combustion. In addition, the extended version of representative interactive linear eddy model offers the potential to treat partially premixed and premixed combustion as well. The well-stirred reactor model was tuned to match the experimental results, thus computed pressure and apparent heat release are in close agreement with the experimental data. Representative interactive linear eddy model was not tuned specifically for the case and thus the computed results for pressure and heat release are in reasonable agreement with experimental data. The computational results show that the interaction of the turbulent flow field and the chemistry reduce the peak temperatures and broaden up the turbulent flame structure. Since this is the first study of a real combustion engine (metal engine) with the newly developed model, representative interactive linear eddy model appears as a promising candidate for predictions of spray combustion in engines, especially in combustion regimes where turbulence–chemistry interaction plays an even more important role like, example given, in low-temperature combustion or combustion with local extinction and re-ignition.

A numerical study of the effect of nozzle diameter on diesel combustion ignition and flame stabilization

“…These two different approaches for combustion modeling allow assessing the importance of the turbulence-chemistry interaction (TCI). Comparisons of such combustion models have been reported in the literature assessing the capabilities of WM-based models and a representative interactive linear eddy model, 20 transported probability density function (TPDF)-based models [21][22][23] or flamelet-based models. [24][25][26][27][28][29] From this last group of works, Lucchini et al 26 assessed various assumptions for the flame structure to model a single-hole reacting spray in a constant-volume vessel.…”

Spray–turbulence–chemistry interactions under engine-like conditions

“…Neglecting the TCI effect may overpredict the local temperature distribution [61,62]. With respect to the autoignition process, simulation results from those models considering TCI effects show better agreement with experiments, especially under low temperatures and/or low oxygen concentrations [9][10][11].…”

“…Furthermore, the TCI effect also plays a critical role in the distributions of the mixture concentration, temperature, and intermediate species, such as OH. Previous studies [9,37,61,62] have…”

“…In the DNS of the two-stage ignition process, the location of the low-temperature autoignition may first be initiated in the fuel-lean part of the dimethyl ether (DME)/air mixture [135], at the stoichiometric mixture [136] or on the fuel-rich side of the DME/methane/air mixture [137]. The subsequent steps are similar in the two mixtures, which consist For turbulent spray flames in more realistic configurations, the interactions between the local flow, spray, and chemistry are even more complex [37,61,62], which have not been fully understood.…”

A Pressure-Coupled Representative Interactive Linear Eddy Model (RILEM) for Engine Simulations

“…Table 1 summarizes development steps on RILEM including this work. In previous implementations of RILEM [26,30,31], the coupling between the flow solver and the LEM line was realized by a volume constraint, i.e., the volumes of the flow solver domain and the LEM domain always match while the pressure is allowed to deviate. As a result of this coupling, heat losses such as wall heat losses and latent heat of evaporation required additional modeling on the LEM line.…”