Shock-tube study of the ignition of methane/ethane/hydrogen mixtures with hydrogen contents from 0% to 100% at different pressures

Abstract

The ignition delay times of diluted hydrogen / reference gas (92% methane, 8% ethane) / O 2 / Ar mixtures with hydrogen contents of 0, 40, 80 and 100% were determined in a highpressure shock tube at equivalence ratios  = 0.5 and 1.0 (dilution 1:5). The temperature range was 900 K  T  1800 K at pressures of about 1, 4 and 16 bar.The reference gas and the 40% hydrogen / 60% reference gas data showed typical characteristics of hydrocarbon systems and can be represented by:(reference gas) andThe pure hydrogen data exhibit a more complex pressure dependence with the 16 bar values having the slowest ignition delay times at lower temperatures and the fastest ignition delay times at higher temperatures. No dependence on the equivalence ratio was observed.The 80% hydrogen / 20% reference gas data display characteristics of hydrocarbon and hydrogen systems.The comparison of the measurements to MPFR-CHEMKIN II simulations with different mechanisms shows that the predictions of all tested mechanisms with the exception of the GRI3.0 agree well with the experimental values for reference gas, 40% hydrogen / 60% reference gas and partly for 80% hydrogen / 20% reference gas and 100% hydrogen. None of the mechanisms can represent the observed reduction of the activation energy at low 3 temperatures of pure hydrogen and of 80% hydrogen / 20% reference gas at p  4 bar.Literature mechanisms which were developed for H 2 or for mixtures with a dominating H 2 subsystem cannot predict the observed reduction of the activation energies, either.

Experimental and kinetic study on ignition delay times of methane/hydrogen/oxygen/nitrogen mixtures by shock tube

“…In this study, the ignition delay time was defined as the interval between the arrival of the reflected shock wave and the initiation of the main ignition, that is, the maximum HO· emission. The ignition delay times obtained in this manner agreed with the calculated values presented in [14]. A comparison among the experimental and calculated (GRI-Mech 3.0 [17]) ignition delay times from this study and those of Petersen et al [18], Wang et al [19] and Hughes et al [20] is shown in Figure 3.…”

“…The predicted values from these mechanisms agree well with the experimental values for pure methane. For the ignition delay times of methane, the experimental results from the present study are about 4.5 times longer than those obtained by Herzler et al using 92% methane and 8% ethane [14]. However, addition of ethane reduces the ignition delay time of methane.…”

“…Cheng and Oppenheimer's work on the ignition of methane/hydrogen mixtures was conducted at equivalence ratios below 1.0. Recently, Herzler and Naumann [14] investigated the ignition delay times of methane/ethane/hydrogen mixtures, which represented typical products of the gasification of biomass or coal, at 900-1800 K and 0.1, 0.4, or 1.6 MPa in a high pressure shock tube. The relationship of the ignition delay to both the reference gas and a 40% hydrogen/60% reference gas mixture were presented, and they suggested that none of the available mechanisms can reproduce the observed reduction in the activation energy for pure hydrogen and 80% hydrogen/20% reference gas at low temperature when the pressure is >0.4 MPa.…”

“…Ignition delay times for mixtures with hydrogen amount-of-substance fractions <40% and an equivalence ratio >1 were not reported by Herzler and Naumann. To the best of our knowledge, only few studies on ignition delay for methane/hydrogen mixtures have been reported [10][11][12][13][14], and the models are not optimal for prediction of the ignition delay time. Ignition delay data for methane/hydrogen mixtures, and in particular methane rich mixtures, are very important for modification of the model of methane/hydrogen oxidation.…”

Effects of Hydrogen Addition on High-Pressure Nonpremixed Natural Gas Combustion

“…More recently, Petersen et al (2007) used the reflected shock technique to measure ignition delay times from methane/hydrogen/air mixtures under lean burn ( = 0.5) combustion conditions over a range of pressures near 21 atm (18.2-25.1 atm) and temperatures ranging from 1141 K to 1553 K. In agreement with the earlier work of Cheng and Oppenheim, the effect of hydrogen addition on ignition delay was found to increase with increasing amounts of hydrogen in the blend-20% H 2 addition decreased the ignition delay by a factor of 3 while the addition of 40% H 2 resulted in a nearly 10 fold decrease in ignition delay compared to the base methane fuel. Similarly, Herzler and Naumann (2009) Huang et al (2006) that the effect of hydrogen in promoting ignition increases with temperature and decreases with pressure. Other fundamental premixed combustion studies have indicated that the preferential diffusion of hydrogen in a turbulent combustion event results in a higher flame propagation rate, even when the laminar flame speed is constant (Kido et al 2002).…”