Numerical Study of Premixed PODE_3-4/CH₄ Flames at Engine-Relevant Conditions

• Published in: Fuels
• Main Authors: Yupeng Leng, Xiang Ji, Chengcheng Zhang, Nigel Simms, Liming Dai, Chunkan Yu
• Format: Article
• Language: English
• Published: MDPI AG 2024-03-01
• Subjects: PODE/CH₄ mixture; ignition delay time; laminar burning velocity; kinetic analysis; perfectly stirred reactor
• Online Access: https://www.mdpi.com/2673-3994/5/1/6

Polyoxymethylene dimethyl ether (PODE_n, n ≥ 1) is a promising alternative fuel to diesel with higher reactivity and low soot formation tendency. In this study, PODE_3-4 is used as a pilot ignition fuel for methane (CH₄) and the combustion characteristics of PODE_3-4/CH₄ mixtures are investigated numerically using an updated PODE_3-4 mechanism. The ignition delay time (IDT) and laminar burning velocity (LBV) of PODE_3-4/CH₄ blends were calculated at high temperature and high pressure relevant to engine conditions. It is discovered that addition of a small amount of PODE_3-4 has a dramatic promotive effect on IDT and LBV of CH₄, whereas such a promoting effect decays at higher PODE_3-4 addition. Kinetic analysis was performed to gain more insight into the reaction process of PODE_3-4/CH₄ mixtures at different conditions. In general, the promoting effect originates from the high reactivity of PODE_3-4 at low temperatures and it is further confirmed in simulations using a perfectly stirred reactor (PSR) model. The addition of PODE_3-4 significantly extends the extinction limit of CH₄ from a residence time of ~0.5 ms to that of ~0.08 ms, indicating that the flame stability is enhanced as well by PODE_3-4 addition. It is also found that NO formation is reduced in lean or rich flames; moreover, NO formation is inhibited by too short a residence time.