Comparative study on chemical kinetic schemes for dual-fuel combustion of n-dodecane/methane blends

Masouleh, M. Ghaderi; Wehrfritz, Armin; Kaario, Ossi; Kahila, Heikki; Vuorinen, Ville

doi:10.1016/j.fuel.2016.10.114

Cited by 32 publications

(6 citation statements)

References 214 publications

(310 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The Polimi reduced mechanism has been validated and used for SF n-dodecane/air under engine-relevant conditions in our previous computational studies of n-dodecane/methane DF combustion, in Refs. [48,63] . Here, it is only validated for SF methanol/air combustion.…”

Section: Declaration Of Competing Interestmentioning

confidence: 99%

A numerical study on combustion mode characterization for locally stratified dual-fuel mixtures

Karimkashi

Kahila

Kaario

et al. 2020

Combustion and Flame

View full text Add to dashboard Cite

a b s t r a c tCombustion modes in locally stratified dual-fuel (DF) mixtures are numerically investigated for methanol/n-dodecane blends under engine-relevant pressures. In the studied constant-volume numerical setup, methanol acts as a background low-reactivity fuel (LRF) while n-dodecane serves as high-reactivity fuel (HRF), controlling local ignition delay time. The spatial distribution of n-dodecane is modeled as a sinusoidal function parametrized by stratification amplitude ( Y ) and wavelength (0.01 mm <λ< 15 mm). In contrast, methanol is assumed to be fully premixed with air at equivalence ratio 0.8. First, onedimensional setup is investigated by hundreds of chemical kinetics simulations in ( Y , λ) parameter space. Further, the concepts by Sankaran et al. (2005, Proceedings of the Combustion Institute ) and Zeldovich (1980, Combustion and Flame ) on ignition front propagation speed are applied to develop a theoretical analysis of the time-dependent diffusion-reaction problem. The theoretical analysis predicts two combustion modes, (1) spontaneous ignition and (2) deflagrative propagation, and leads to an analytical expression for the border curve called β-curve herein. One-dimensional chemical kinetics simulations confirm the presence of two combustion modes in ( Y , λ) parameter space while the β-curve explains consistently the position of phase border observed in the simulations. Finally, the role of convective mixing is incorporated to the theoretical expression for the β-curve. The effect of convection on combustion modeis assessed by carrying out two-dimensional fully-resolved simulations with different turbulence levels. Two-dimensional numerical simulation results give evidence on combustion mode switching, which is consistent with predictions of the modified β-curve for turbulent cases. The practical output of the paper is the β-curve which is proposed as a predictive tool to estimate combustion modes for various fuels or fuel combinations.

show abstract

Section: Declaration Of Competing Interestmentioning

confidence: 99%

A numerical study on combustion mode characterization for locally stratified dual-fuel mixtures

Karimkashi

Kahila

Kaario

et al. 2020

Combustion and Flame

View full text Add to dashboard Cite

show abstract

“…To estimate the effect of methane on the autoignition time stratification in the mixture space, homogeneous reactor calculations were employed, using the reduced chemical mechanism by Ranzi et al (130 species, 2323 reactions, [39]). This mechanism choice was motivated by the findings of a comprehensive mechanism assessment for methane/dodecane air mixtures reported in [40]. Additionally, the calculations were repeated for a subset of cases using the substantially more complex detailed mechanisms (Polimi [41] and LLNL [42]) yielding qualitatively the same conclusions.…”

Section: Calculations: Methane Influence On the Auto-ignition Front And Laminar Flame Spreading Ratesmentioning

confidence: 99%

Experimental investigation of pilot-fuel combustion in dual-fuel engines, Part 2: Understanding the underlying mechanisms by means of optical diagnostics

Srna

Rotz

Bolla

et al. 2019

Fuel

View full text Add to dashboard Cite

The pilot-fuel auto-ignition and combustion under engine like conditions in compressed methane/air mixtures have been investigated. Experiments were performed in an optically accessible Rapid Compression-Expansion Machine featuring quiescent charge conditions and a single-hole coaxial diesel injector mounted on the cylinder periphery. In Part 1, the phenomenology of the pilot-fuel combustion has been studied based on the thermodynamic analysis. With the addition of methane, a strongly prolonged pilot-fuel combustion duration was observed, especially at increased EGR rates. The aim of Part 2 is to improve the understanding of the underlying processes governing the pilot-fuel burning and premixed flame initiation in dual-fuel engines. For this purpose, the thermodynamic analysis was supplemented by the application of optical diagnostics including high-speed CH 2 O-PLIF, Schlieren and OH* chemiluminescence, and corroborated with homogeneous reactor and laminar flame speed calculations. The investigations focused on determining the role of (a) ignition location and number of ignition kernels, (b) stratification of the ignition delay due to the chemical influence of methane and (c) the role of flame propagation during the pilot-fuel burning. In the initial phase, the combustion was found to propagate through an auto-igniting front. When combustion reaches the lean zones with high ignition delay spatial stratification, the premixed flame propagation becomes the dominant mechanism owing to its higher spreading rate. Both processes influence the pilotfuel combustion duration. With increasing methane concentration the simulations predict increasing stratification of the ignition delay in lean regions, and a moderately increased laminar flame speed in the pilot-fuel lean regions. Overall, this explains the observed trends of longer pilot-fuel burning in the dual-fuel cases and indicates an increasing role of flame-propagation in the dual-fuel combustion pilot-fuel burning.

show abstract

“…It has been previously observed in the literature that adding methane to the ambient retards ignition compared to the ECN Spray A conditions. 6,10,17 According to Figure 2(b) and (c), adding methanol to the ambient delays IDT even further compared to methane, consistent with the observations by Karimkashi et al 62 For instance, IDT at the most reactive mixture fraction (the point with the shortest IDT within the considered range of mixture fraction) is observed to be longer in DF2 compared to DF1 at similar T amb . The quantified values of IDT are provided in the following parts of the paper as compared to LES data.…”

Section: Resultsmentioning

confidence: 99%

“…However, numerical tests carried out by the authors have shown that the relative ratio of the first- and second-stage ignition time remains approximately constant between the two mechanisms for DF n -dodecane/methane. In addition, Polimi-reduced mechanism has been recently validated for methanol combustion under engine relevant conditions by Karimkashi et al 61 and it is used in numerical simulations for DF n -dodecane/methanol by Karimkashi et al 62 This mechanism has been also compared against other mechanisms in the DF context by the authors 17 and a sensitivity analysis of the chemical mechanism is provided in our previous publication under dual-fuel conditions. 6 Finally, we note that all the modeling assumptions related to the present results are of numerical character.…”

Section: Methodsmentioning

confidence: 99%

“…These findings match well with the findings in previous numerical studies. 6,9–11,16–20 Moreover, direct numerical simulations (DNS) have provided numerical evidence on the importance of LTC and HTC in the DF ignition process. 21,22 Using renewable fuels such as methanol in DF CI engines have been studied both experimentally 23–26 and numerically.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Large-eddy simulation of diesel pilot spray ignition in lean methane-air and methanol-air mixtures at different ambient temperatures

Karimkashi

Gadalla

Kannan

et al. 2022

International Journal of Engine Research

View full text Add to dashboard Cite

In dual-fuel compression-ignition engines, replacing common fuels such as methane with renewable and widely available fuels such as methanol is desirable. However, a fine-grained understanding of diesel/methanol ignition compared to diesel/methane is lacking. Here, large-eddy simulation (LES) coupled with finite rate chemistry is utilized to study diesel spray-assisted ignition of methane and methanol. A diesel surrogate fuel ( n-dodecane) spray is injected into ambient methane-air or methanol-air mixtures at a fixed lean equivalence ratio [Formula: see text] = 0.5 at various ambient temperatures ([Formula: see text] = 900, 950, 1000 K). The main objectives are to (1) compare the ignition characteristics of diesel/methanol with diesel/methane at different [Formula: see text], (2) explore the relative importance of low-temperature chemistry (LTC) to high-temperature chemistry (HTC), and (3) identify the key differences between oxidation reactions of n-dodecane with methane or methanol. Results from homogeneous reactor calculations as well as 3 + 3 LES are reported. For both DF configurations, increasing [Formula: see text] leads to earlier first- and second-stage ignition. Methanol/ n-dodecane mixture is observed to have a longer ignition delay time (IDT) compared to methane/ n-dodecane, for example ≈ three times longer IDT at [Formula: see text] = 950 K. While the ignition response of methane to [Formula: see text] is systematic and robust, the [Formula: see text] window for n-dodecane/methanol ignition is very narrow and for the investigated conditions, only at 950 K robust ignition is observed. For methanol at [Formula: see text] = 1000 K, the lean ambient mixture autoignites before spray ignition while at [Formula: see text] = 900 K full ignition is not observed after 3 ms, although the first-stage ignition is reported. For methanol, LTC is considerably weaker than for methane and in fully igniting cases, heat release map analysis demonstrates the dominant contribution of HTC to total heat release rate for methanol. Reaction sensitivity analysis shows that stronger consumption of OH radicals by methanol compared to methane leads to the further delay in the spray ignition of n-dodecane/methanol. Finally, a simple and novel approach is developed to estimate IDT in reacting LES using zero-dimensional IDT calculations weighted by residence time from non-reacting LES data.

show abstract

Comparative study on chemical kinetic schemes for dual-fuel combustion of n-dodecane/methane blends

Cited by 32 publications

References 214 publications

A numerical study on combustion mode characterization for locally stratified dual-fuel mixtures

A numerical study on combustion mode characterization for locally stratified dual-fuel mixtures

Experimental investigation of pilot-fuel combustion in dual-fuel engines, Part 2: Understanding the underlying mechanisms by means of optical diagnostics

Large-eddy simulation of diesel pilot spray ignition in lean methane-air and methanol-air mixtures at different ambient temperatures

Contact Info

Product

Resources

About