The dependence of NTC behavior on the equivalence ratio and nitrogen fraction in cool flame region

Yu, Ruiguang; Liu, Jie; Ma, Biao

doi:10.1016/j.fuel.2020.117623

Cited by 12 publications

(7 citation statements)

References 34 publications

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“…NTC of IDT is an important feature of hydrocarbon fuels for applications in internal combustion engines. NTC behavior has been studied by many scholars and experts 52,53 . The so‐called NTC behavior, in which a period of IDT appears to increase with temperature as the temperature changes from low to medium temperature, is dominated by the low‐temperature oxidation kinetics of higher alkanes.…”

Section: Resultsmentioning

confidence: 99%

“…The so‐called NTC behavior, in which a period of IDT appears to increase with temperature as the temperature changes from low to medium temperature, is dominated by the low‐temperature oxidation kinetics of higher alkanes. Currently, propane is the smallest alkane to demonstrate this NTC behavior 53 . In general, methane does not exhibit NTC behavior except at very high fuel concentrations 54 .…”

Section: Resultsmentioning

confidence: 99%

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Chemical kinetic analysis on the auto‐ignition characteristics of natural gas–diesel dual‐fuel combustion under engine‐relevant conditions

Liu

Wang

Xie

et al. 2023

Int J of Chemical Kinetics

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With the advent of energy crisis and stringent emission regulations, natural gas (NG)/diesel dual‐fuel engines have entered the popular view. In this paper, the accurate boundary conditions are determined by the Converge model and the transient parameters were introduced into the chemical kinetics model to make the operating conditions more closely match the actual engine operating conditions. The effects of different methane/n‐heptane ratios, initial temperatures, initial pressures, and equivalence ratios on the IDT of methane/n‐heptane fuel mixtures were analyzed using comprehensive chemical kinetic tools such as mole fraction analysis, ROP analysis, and sensitivity analysis. The IDT of methane/n‐heptane mixture decreased significantly with increasing the equivalence ratio, initial pressure, and the proportion of n‐heptane in the mixture, but the change of temperature was more complicated for the IDT. The NTC behavior of methane/n‐heptane mixture was also affected by the NTC behavior of n‐heptane. With the increase of initial temperature, the consumption of methane and n‐heptane appeared to be significantly accelerated. The peak of radicals and intermediate groups appeared earliest and had the highest radical concentration when the n‐heptane content was 30%. With the increase of initial pressure, the peak moments of the six radicals were further advanced, but the mole concentrations of O, OH, H radicals decreased significantly. This paper not only provides a reference for the design of NG/diesel dual‐fuel engines, but also provides a theoretical basis and data support for improving the ignition and initial condition setting strategies of the engines.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Chemical kinetic analysis on the auto‐ignition characteristics of natural gas–diesel dual‐fuel combustion under engine‐relevant conditions

Liu

Wang

Xie

et al. 2023

Int J of Chemical Kinetics

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“…). The explosion and nonexplosion conditions were searched within the temperature range of 350−2500 K and pressure range of 3.5−10 9 Pa. An explosion criterion of a 50 K increase of the initial temperature within 10 s was employed in this study. This criterion is selected to ensure that the temperature change is small and the residence time is long enough compared with the characteristic time and temperature scales in the practical applications.…”

Section: Methodsmentioning

confidence: 99%

“…The second is that they exhibit cool flames. The cool flames are governed by the low-temperature chemistry via oxygen addition to fuel radicals and subsequent isomerization and radical branching reactions . It was found that the existence of the cool flame can dramatically extend the lean and rich flammability limits of the conventional high-temperature flame. , Furthermore, a cool flame and two-stage ignition were observed for the propane/oxygen mixtures in microgravity conditions .…”

Section: Introductionmentioning

confidence: 99%

Effect of Ozone Addition on the Cool Flame and Negative Temperature Coefficient Regions of Propane–Oxygen Mixtures

2020

ACS Omega

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In this study, the effects of ozone addition on the cool flame and NTC (negative temperature coefficient) regions of stoichiometric C 3 H 8 /O 2 mixtures are computationally studied through the explosion limit profiles. The results show that with minute quantities of ozone addition (the mole fraction of ozone is 0.1%), the cool flame area is enlarged to the low-temperature region. Further increases in the mole fraction of ozone gradually weaken the NTC behavior, and a monotonic explosion limit is eventually achieved. The sensitivity analysis of the main reactions involving ozone reveals that the explosion limit is mainly controlled by the ozone unimolecular decomposition reaction O 3 (+M) = O 2 + O (+M). However, as its reverse reaction is a third-body reaction, this reaction will lose its effect on the explosion limit in the high-pressure region. On the contrary, the reaction O 3 + HO 2 = OH + O 2 + O 2 has a significant effect on the explosion limit in the high-pressure and low-temperature region, as the concentration of HO 2 increases through the rapid third-body reaction H + O 2 + M = HO 2 + M.

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“…Furthermore, the typical negative temperature coefficient (NTC) behavior was reported for larger alkanes . Recently, Yu et al first investigated the effect of equivalence ratio and N 2 addition on the explosion limit of propane . After that, Liu et al investigated the effect of O 3 addition on the cool flame region of the explosion limit of propane …”

Section: Introductionmentioning

confidence: 99%

On the Second Explosion Limits of Hydrogen, Methane, Ethane, and Propane

Tang

2020

ACS Omega

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In this work, we have first investigated the explosion limit behaviors from hydrogen to propane through numerical simulations and validated with the available experimental data. The shape of the explosion limit curves and the possible turning points ( P 1–2 , T 1–2 ), first to second limit transition, and ( P 2–3 , T 2–3 ), second to third limit transition that bound the second explosion limit as a function of the fuel carbon number, have been examined. Results show that with an increase of methane mole fraction in the hydrogen/methane system, the upper turning point ( P 1–2 , T 1–2 ) remains almost unchanged and the lower transition point ( P 2–3 , T 2–3 ) rotates counterclockwise around ( P 1–2 , T 1–2 ). With a further increase of carbon number, ( P 1–2 , T 1–2 ) moves to the lower-pressure and -temperature region and ( P 2–3 , T 2–3 ) gradually moves to the lower-pressure and higher-temperature region. The slope of the second explosion limit is inversely proportional to the carbon number, k PT = 0.0069 – 0.005/( X c – 0.7), approximately. Second, a sensitivity analysis has been conducted to study the elementary reaction on the second explosion limits. The results show that the chain branching and termination reactions governing the explosion limit of hydrogen have a little effect on the second explosion limit of methane. The C 2 H 5 O 2 H decomposition to form OH radicals is dominant in controlling the nonmonotonic behavior of the second explosion limit of C 2 H 6 . The second explosion limit behavior of propane is governed by three sets of reactions in the low-temperature oxidation process.

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The dependence of NTC behavior on the equivalence ratio and nitrogen fraction in cool flame region

Cited by 12 publications

References 34 publications

Chemical kinetic analysis on the auto‐ignition characteristics of natural gas–diesel dual‐fuel combustion under engine‐relevant conditions

Chemical kinetic analysis on the auto‐ignition characteristics of natural gas–diesel dual‐fuel combustion under engine‐relevant conditions

Effect of Ozone Addition on the Cool Flame and Negative Temperature Coefficient Regions of Propane–Oxygen Mixtures

On the Second Explosion Limits of Hydrogen, Methane, Ethane, and Propane

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