A numerical investigation of the combustion kinetics of reactivity controlled compression ignition (RCCI) combustion in an optical engine

Liu, Xinlei; Kokjohn, Sage; Liu, Yu; Wang, Hu; Li, Hailin; Yao, Mingfa

doi:10.1016/j.fuel.2018.12.068

Cited by 46 publications

(22 citation statements)

References 33 publications

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“…A base mesh of 2.0 mm and an AMR scale of 3.0 were adopted, which generated the minimum mesh size of 0.25 mm. Based on the previous research [22,37,38], this mesh setup can achieve grid-convergence. The simulations started from the intake valve closing (IVC) timing (-160° crank angle after the top dead center (CA ATDC)) and ended at the exhaust valve opening (EVO) timing (140° CA ATDC), implying only closed-cycle modeling.…”

Section: Computational Meshmentioning

confidence: 99%

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A numerical investigation of isobaric combustion strategy in a compression ignition engine

Liu

Aljabri

Mohan

et al. 2020

International Journal of Engine Research

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Three-dimensional computational fluid dynamic simulations were conducted to study the means to achieve isobaric combustion mode in a compression ignition engine, which is intended to be used in the high-efficiency double compression-expansion engine (DCEE) concept. Compared to the conventional diesel combustion mode, the isobaric combustion mode generated a significantly lower peak combustion pressure, which was beneficial for the high load extension. For both combustion modes, the ignition was triggered downstream of the nozzle, with the heat release dominated by HCO + O2 = CO+HO2, while the injection-combustion duration for the isobaric combustion mode was significantly longer. The effects of swirl ratio, spray angle, and piston geometries on the isobaric combustion at various engine loads were also investigated. The higher swirl ratio resulted in a higher heat transfer loss and thus lower thermal efficiency. Due to the higher air utilization rates and lower heat transfer losses, cases with spray angles of 140° and 150° generated the higher thermal efficiencies. The piston bowl geometry was found to have a significant impact on the mixing and combustion processes, especially at high engine load conditions. For the conditions under study, the original piston geometry with a swirl ratio of 0 and a spray angle of 140° demonstrated the highest thermal efficiency for the isobaric combustion mode. The results of this work will provide guidance in the practical design and implementation of the DCEE concept.

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Section: Computational Meshmentioning

confidence: 99%

“…CFD results, together with the chemical kinetics mechanism, were taken as inputs. Instantaneous reactive source terms were computed by considering each cell as a perfectly stirred reactor [37,39,40].…”

Section: Data-processing Approachmentioning

confidence: 99%

A numerical investigation of isobaric combustion strategy in a compression ignition engine

Liu

Aljabri

Mohan

et al. 2020

International Journal of Engine Research

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“…The fuel chemistry coupled was a reduced PRF mechanism consisting of 73 species and 296 reactions [50]. The sub-models used in the simulation, which had been validated in simulating the combustion process of a RCCI combustion engine [42,43]. The renormalization group (RNG) k-ɛ model was adopted for the calculation of turbulence [51].…”

Section: Modeling Setupmentioning

confidence: 99%

“…Their experimental investigation showed that in the case of double-injection gasoline PPC combustion, during the low-to high-temperature reaction transition, the HCHO consumption to form OH radicals is higher, indicating faster transition for better combustion stability. However, the optical engine observations only focused on a number of specific species, making it difficult to fully clarify the engine combustion details [40,41,42,43].…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of the Combustion Kinetics of Partially Premixed Combustion (PPC) Fueled with Primary Reference Fuel

Zhao

Wang

Liu

et al. 2020

SAE Technical Paper Series

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This work numerically investigates the detailed combustion kinetics of partially premixed combustion (PPC) in a diesel engine under three different premixed ratio fuel conditions. A reduced Primary Reference Fuel (PRF) chemical kinetics mechanism was coupled with CONVERGE-SAGE CFD model to predict PPC combustion under various operating conditions. The experimental results showed that the increase of premixed ratio (PR) fuel resulted in advanced combustion phasing. To provide insight into the effects of PR on ignition delay time and key reaction pathways, a post-process tool was used. The ignition delay time is related to the formation of hydroxyl (OH). Thus, the validated Converge CFD code with the PRF chemistry and the post-process tool was applied to investigate how PR change the formation of OH during the low-to high-temperature reaction transition. The reaction pathway analyses of the formations of OH before ignition time were investigated. It was found that in the case of PR0%, the second isomerization from C7H14OOH2-4O2 to NC7KET24 and the decomposition of NC7KET24 contributed 27.6% and 46.46% of OH formation respectively. The contribution of AC8H16OOH-B to the formation of OH was just 12.13%. It can be concluded that the low temperature oxidation reactions of n-heptane were key steps in producing OH. While in the cases of PR30% and PR50%, because of the higher in-cylinder temperature, most of OH derived from the decomposition reaction of H2O2 that contributed 54.47% and 54.63% of OH formation respectively. Besides, in the PR30% and PR50%, the oxidation reactions of IC4H7 contributed 31.95% and 33.84% of OH formation respectively, and the oxidation reaction of IC4H6OH contributed 19.08% and 22.22% of OH formation respectively, which indicated that the oxidation of iso-octane also contributed to the production of OH. In addition, the distributions of mass fraction, production rate and representative creation reaction (RCR) of OH showed that in the case of PR30% and PR50%, the formation of OH outside the spray periphery were dominated by the reactions R394 (H2O2 (+ M) <=> 2 OH (+ M)), while that in the spray periphery were predominantly controlled by the reaction R21 (NC7KET24 => NC3H7CHO + CH3COCH2 + OH) and R125 (IC4H6OH + HO2 <=> CH2CCH2OH + CH2O + OH). Premixed fuel from port injection changed the formation pathway of OH during the oxidation of direct injection fuel through the reaction R125.

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“…Therefore, fundamental goals should be set to make the results generally applicable in the future combustion systems regardless of the fuel type and its physical and chemical properties. This latter requirement is usually fulfilled by steady-operating combustion applications like industrial boilers, furnaces, and gas turbines where the combustion chamber temperature is above 1000 K 2,3 , and chain breaking occurs promptly. Hence, the atomic fuel composition becomes the governing factor of the process.…”

Section: Introductionmentioning

confidence: 99%

Wavelet analysis of flame blowout of a liquid-fueled swirl burner with quarls

Józsa

Novotni

2019

noise cont engng j

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Lean swirl combustion is the leading burner concept today, used in several steadyoperating applications to ensure awide operating range and low pollutant emissions. Approaching lean blowout is highly desired by design to achieve the lowest possible NOX emission. It was shown earlier that quarls could significantly extend the operating regime of liquid-fueled swirl burners. In the present study, the accompanying acoustic noise is evaluated by continuous wavelet transformation to show the effect of various quarl geometries on lean flame blowout. However, the desired flame shape of swirl burners is V, first, and a straight flame, and then a transitory regime can be observed before the developed V-shaped flame through increasing the swirl number. If the axial thrust is excessive, blowout might occur in earlier stages. Presently, the characteristic bands before blowout were analyzed and evaluated at various quarl geometries, swirl numbers, and atomizing pressures. The latter parameter also acts as an axial thrust control to adjust the swirl number. firstly, a straight flame, then a transitory regime can be observed before the developed V-shaped flame through increasing the swirl number. If the axial thrust is excessive, blowout might occur in earlier stages. Presently, the characteristic bands before blowout were analyzed and evaluated at various quarl geometries, swirl numbers, and atomizing pressures. The latter parameter also acts as an axial thrust control to adjust the swirl number.

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A numerical investigation of the combustion kinetics of reactivity controlled compression ignition (RCCI) combustion in an optical engine

Cited by 46 publications

References 33 publications

A numerical investigation of isobaric combustion strategy in a compression ignition engine

A numerical investigation of isobaric combustion strategy in a compression ignition engine

Numerical Investigation of the Combustion Kinetics of Partially Premixed Combustion (PPC) Fueled with Primary Reference Fuel

Wavelet analysis of flame blowout of a liquid-fueled swirl burner with quarls

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