Hydrogen effects on ignition delay time of methyl butanoate in a rapid compression machine

Abstract

The effect of hydrogen addition on the ignition delay time of methyl butanoate was studied using a rapid compression machine experiment and ANSYS CHEMKIN-PRO 19.0 numerical analysis. The ignition delay was measured under engine-relevant conditions by varying equivalence ratios (0.5 and 1.0), compression pressures (15 and 30 bar), compression temperatures (860-1060 K), and hydrogen mole fractions in the methyl butanoate/hydrogen mixture (0%, 25%, 50%, and 75%). The kinetic mechanism was modified by adding the methyl butanoate mechanism to the NUIG Aramco 3.0 mechanism and modifying the rate parameters of the H-atom abstraction reactions of methyl butanoate. The numerical results obtained using the modified mechanism were in good agreement with the experimental results. The methyl butanoate/hydrogen mixture did not show a negative temperature coefficient characteristic. With hydrogen addition, the ignition delay increased at low temperatures but decreased at high temperatures. The results of the chemical and dilution effect analysis using the imaginary inert H 2 showed that the chemical effects differ depending on the temperature. Most added hydrogen molecules participate in the chain propagation reactions to produce H radicals and consume OH by the reaction H 2 + OH ! H + H 2 O. This, in turn, changes the reactions of other species, such as HO 2 and H 2 O 2. The results of the reaction path analysis for the related species showed that the addition of hydrogen reduced radical reactions at low temperatures, while increasing them at high temperatures.

Prediction of ignition delay times of Jet A-1/hydrogen fuel mixture using machine learning

“…The opposite effects of hydrogen addition depending on temperature has also been reported in previous studies on hydrogen blending with methyl butanoate [36] and n-heptane/n-decane [37]. The OH radical-related reaction rates decrease at low temperatures but increase at high temperatures upon hydrogen addition, lending to the change of production rates of the OH, HO 2 and H 2 O 2 radicals [36]. Figure 7 shows that the OH mass fraction gets lower at 800 K but higher at 900 K with the increasing blending ratio of hydrogen.…”

Experimental study of ignition behaviors of pyrolysis gas of kerosene‐based endothermic hydrocarbon fuel

“…Measurements of ignition delay time at low temperature regime are carried out on the RCM setup, 19,20 as shown in Figure 1. The machine is pneumatically driven and hydraulically stopped.…”

Advantages of hydrogen addition in a passive pre‐chamber ignited SI engine for passenger car applications

“…Although there are multiple breakthroughs in the understanding of combustion characteristics of hydrogen enriched flames in multiple research devices, the applicability of this knowledge is still in its early stage. While there are plenty of research works related to constantvolume chambers, 26,27 scaled burners, 28 or rapid compression machines 29 ; the state-of-the-art in H 2 ICE is more limited and mostly focused on developing engines fueled by pure hydrogen. 30 Nonetheless, this approach is still difficult to implement for commercial transportation in passenger cars due to severe economic constraints.…”