Shock tube and kinetic study on ignition characteristics of lean methane/n-heptane mixtures at low and elevated pressures. (15th April 2020)

• Record Type: Journal Article
• Authors: Gong, Zhen; Feng, Liyan; Wei, Lai; Qu, Wenjing; Li, Lincheng
• Is Part Of: Energy. Volume 197(2020)
• Publication Date: 2020-04-15
• Subjects: Methane -- N-heptane -- Ignition delay time -- Shock tube -- Chemical kinetics; Power resources -- Periodicals; Power (Mechanics) -- Periodicals; Energy consumption -- Periodicals; 333.7905
• DOI: 10.1016/j.energy.2020.117242
• Languages: English
• ISSNs: 0360-5442

Abstract

Abstract: To acquire ignition control methods for dual-fuel marine engine and HCCI engine, ignition characteristics of lean n-heptane/methane mixture under pressure of 2.0 bar and temperature range from 1241 to 1825 K were studied by shock tube and CHEMKIN with LLNL3.1 mechanism. And ignition processes under temperature range from 700 to 1200 K and pressure range from 40 to 140 bar were investigated by CHEMKIN with NUI mechanism. The results illuminate that at low-pressure high-temperature condition, n-heptane's replacement and the increase of n-heptane content obviously reduced ignition delay times (IDT). The reduction degree of IDT decreased when n-heptane content was high. N-heptane's addition also reduced IDT. But this reduction magnitude was less than that of n-heptane's replacement. Methane's addition slightly inhibited n-heptane's auto-ignition. The reaction time of n-heptane was obviously earlier than that of methane. N-heptane decomposition induced radical formation firstly, which triggered subsequent n-heptane's H-abstraction and the advance of methane's oxidation. At ultra-high-pressure low-temperature condition, increasing n-heptane's content enhanced negative temperature coefficient (NTC) behavior. The end time point of complete consumption of two fuels was the same. Low-temperature condition inhibited n-heptane decomposition, with n-heptane's H-abstraction dominating ignition process. Highlights: Ignition properties of CH4/n-C7H16 mixture was revealed by shock tube and mechanisms. Active radicals formed from n-heptane's decomposition advanced methane's oxidation. Methane's addition slightly retarded the ignition of pure n-heptane mixture. The results provided ignition control method for natural-gas/diesel dual-fuel engine.