The effect of diluent gases on ignition delay times in the shock tube and in the rapid compression machine

Würmel, Judith; Silke, E J; Curran, Henry J.; Conaire, M.S. Ó; Simmie, John M.

doi:10.1016/j.combustflame.2007.06.010

Cited by 73 publications

(46 citation statements)

References 29 publications

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“…Buffer gases are also widely used to control test conditions in fundamental combustion researches [9][10][11][12][13]. The composition of buffer gases affects the heat capacity of the gas mixture, three-body collision efficiencies and concentrations of fuel and O2.…”

Section: Introductionmentioning

confidence: 99%

“…They found that, compared to N2, Ar reduces the ignition delay of iso-octane by 20%. Würmel et al [10] studied the effects of diluent gases on ignition delay in rapid compression machine (RCM) and ST. The authors found that the Ar accelerates the ignition in ST, but decelerates ignition in RCM, which is caused by the differences in the thermal conductivity and heat capacity among different buffer gases.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Buffer Gas Composition on Autoignition of Dimethyl Ether

et al. 2015

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Abstract:Experimental and numerical studies are conducted on the thermal, chemical and dilution effects of buffer gas composition on autoignition of dimethyl ether (DME). The buffer gases considered are nitrogen (N2), a mixture of N2 and argon (Ar) at a mole ratio of 50%/50% and a mixture of Ar and carbon dioxide (CO2) at a mole ratio of 61.2%/38.8%. Experiments are performed using a rapid compression machine (RCM) at compressed pressure of 10 bar, equivalence ratio (φ) of 1, and compressed temperature from 670 K to 795 K. The N2 dilution ratio considered ranges from 36.31% to 55.04%. The experimental results show that buffer gas composition has little impact on the first-stage ignition delay. However, significant differences in the total ignition delay as a function of buffer gas composition are observed in the negative temperature coefficient (NTC) region. Compared to N2, N2/Ar (50%/50%) mixture decreases the total ignition delay by 31%. The chemical effects of buffer gas composition on the first-stage and total ignition delays are negligible. With increasing N2 dilution ratio, the first-stage ignition delay slightly increases, while a significant increase in the total ignition delay is observed. Moreover, the NTC behavior of total ignition delay is noted to become more pronounced at high N2 dilution ratio. The heat release during the first-stage ignition decreases as N2 dilution ratio increases. Results of OPEN ACCESSEnergies 2015, 8 10199 numerical simulations with the Zhao DME mechanism over a wider range of temperature show good agreement with that of experiments. Further numerical simulations are conducted using pure N2, Ar and CO2 as buffer gases. Results indicate that the thermal effects are the dominant factor in low temperature and NTC regions. The chemical effects become pronounced in the NTC region, and the chemical effect of CO2 exceeds the thermal effect at the compressed temperature higher than 880 K.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of Buffer Gas Composition on Autoignition of Dimethyl Ether

et al. 2015

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“…Argon and nitrogen are mainly used as diluent gas in shock tube ignition study. Davidson and Hanson [24] and Würmel et al [25] have made a detailed discussion about the influence of diluent gas on the measured ignition delay times. It seems that nitrogen is the best choice for the diluent gas when normal combustion occurs in air.…”

Section: Methodsmentioning

confidence: 99%

“…Würmel et al [25] studied the effect of diluent gas on the ignition delay of hydrocarbon fuels by calculation. They indicated that the exothermicity of the radical growth phase causes the temperature of the mixture with high heat capacity to rise slower than that of the mixture with low heat capacity, and this leads to deceleration of the ignition.…”

Section: The Effect Of Water Vapor On the Ignition Of Kerosenementioning

confidence: 99%

The vitiation effects of water vapor and carbon dioxide on the autoignition characteristics of kerosene

et al. 2014

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In ground tests of hypersonic scramjet, the highenthalpy airstream produced by burning hydrocarbon fuels often contains contaminants of water vapor and carbon dioxide. The contaminants may change the ignition characteristics of fuels between ground tests and real flights. In order to properly assess the influence of the contaminants on ignition characteristics of hydrocarbon fuels, the effect of water vapor and carbon dioxide on the ignition delay times of China RP-3 kerosene was studied behind reflected shock waves in a preheated shock tube. Experiments were conducted over a wider temperature range of 800-1 500 K, at a pressure of 0.3 MPa, equivalence ratios of 0.5 and 1, and oxygen concentration of 20%. Ignition delay times were determined from the onset of the excited radical OH emission together with the pressure profile. Ignition delay times were measured for four cases: (1) clean gas, (2) gas vitiated with 10% and 20% water vapor in mole, (3) gas vitiated with 10% carbon dioxide in mole, and (4) gas vitiated with 10% water vapor and 10% carbon dioxide, 20% water vapor and 10% carbon dioxide in mole. The results show that carbon dioxide produces an inhibiting effect at temperatures below 1 300 K when φ = 0.5, whereas water vapor appears to accelerate the ignition process below a critical temperature of about 1 000 K when φ = 0.5. When both water vapor and carbon dioxide exist together, a minor inhibiting effect is observed at φ = 0.5, while no effect is found at φ = 1.0. The results are also discussed preliminary by considering both the combustion reaction mechanism and the thermophysics properties of the fuel mixtures. The current measurements demonstrate vitiation effects of water vapor and carbon dioxide on the autoignition characteristics of China RP-3 kerosene at air-like O 2 concentration. It is important to account for such effects when data are extrapolated from ground testing to real flight conditions.

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“…Heat transfer during and after compression was affected when carbon dioxide was added to the mixture, leading to the above-mentioned results. Würmel et al [34] explained how a diluent gas affected the ignition delay in an RCM. In this study, it can be seen that although carbon dioxide could decelerate the overall ignition of n-heptane, it could accelerate the first-stage ignition under certain experimental conditions.…”

Section: Influence Of Carbon Dioxide On Two-stage Ignitionmentioning

confidence: 99%

Experimental study of n-heptane ignition delay with carbon dioxide addition in a rapid compression machine under low-temperature conditions

et al. 2012

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The ignition delay of n-heptane homogeneous charge compression ignition (HCCI) combustion under high levels of carbon dioxide addition was quantitatively measured at elevated pressure from low to intermediate temperatures in a rapid compression machine. The experiments were conducted in the compressed temperature range 613-750 K. Both the compression ratio and fuel/air equivalence ratio were varied to investigate their effects on the ignition delay of n-heptane. Carbon dioxide was subsequently added to study the influence of the carbon dioxide level on the ignition delay of n-heptane under low-temperature conditions. It was found that carbon dioxide had different effects on the two -stages of ignition delay of n-heptane under low-temperature conditions: the concentration of carbon dioxide had little effect on the first-stage ignition time; a certain concentration of carbon dioxide accelerated the first-stage ignition but had a significantly larger impact on the second-stage ignition delay, thus increasing the overall ignition delay time. The results also showed that the first-stage ignition delay of n-heptane is only a function of temperature under low-temperature conditions. The mass of n-heptane in the combustible mixture, the equivalence ratio, and the pressure at the top dead center had little effect on the first-stage ignition time of n-heptane. rapid compression machine, n-heptane, ignition delay, low-temperature condition, carbon dioxide Citation:Guang H Y, Yang Z, Huang Z, et al. Experimental study of n-heptane ignition delay with carbon dioxide addition in a rapid compression machine under low-temperature conditions. Chin Sci Bull, 2012, 57: 39533960, doi: 10.1007/s11434-012-5331-8Environmental pressures and the energy crisis have led to increasing attention being paid to the improvement of combustion efficiency and the reduction of internal combustion (IC) engine emissions. To fundamentally improve emission levels and combustion efficiency, it is necessary to have an understanding of the combustion chemical reaction dynamics and combustion methods of IC engines. A conventional diesel engine has the advantage of a higher combustion efficiency than that of a gasoline engine, but it cannot simultaneously reduce particulate matter (PM) and NO x because of the partially rich or lean combustion in the combustion chamber. Homogeneous charge compression ignition (HCCI) has become the focus of research because of its excellent efficiency and low emission levels [1][2][3]. To control HCCI combustion, it is essential to have sufficient understanding of its ignition time and combustion speed. Processes such as fuel evaporation, diffusion, combustion, and heat transfer are very complicated in IC engines. In addition, differences exist between each working cycle, making data measurement and control of parameters between combustion cycles very difficult. Moreover, IC engines have complex structures, so it is very difficult to install test equipment or visualization windows. To solve these problems, a variety of expe...

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The effect of diluent gases on ignition delay times in the shock tube and in the rapid compression machine

Cited by 73 publications

References 29 publications

Effects of Buffer Gas Composition on Autoignition of Dimethyl Ether

Effects of Buffer Gas Composition on Autoignition of Dimethyl Ether

The vitiation effects of water vapor and carbon dioxide on the autoignition characteristics of kerosene

Experimental study of n-heptane ignition delay with carbon dioxide addition in a rapid compression machine under low-temperature conditions

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