Large eddy simulation of auto-igniting methanol/n-dodecane blend spray flames

The study investigates the auto-ignition characteristics of methanol/n-dodecane fuel blends at varying blend ratios and ambient temperatures using large eddy simulation (LES) in OpenFOAM with the Engine Combustion Network (ECN) Spray-D injector. The primary objective is to determine the maximum methanol fraction in the blend that enables stable combustion with an engine-relevant ignition delay time (IDT) below 1 ms at ambient temperatures of 900, 950, 1000, and 1100 K . The numerical framework validation is performed against existing ECN n-dodecane data, new ECN experiments for pure methanol, and new methanol–octanol–diesel blend experiments from the Combustion Research Unit (CRU). Four cases satisfy the IDT criterion: (I) 10% methanol, 90% n-dodecane at 900 K , (II) 20%–80% at 950 K , (III) 30%–70% at 1000 K , and (IV) 70%–30% at 1100 K . Increasing the methanol content suppresses ignition due to methanol’s high heat of vaporisation and net consumption of OH radical at low temperatures. Ignition occurs under rich conditions for cases I and II, near stoichiometric conditions for case III, and under lean conditions for the methanol-dominant case IV. Case IV exhibits elevated centre-line temperature, increased NO emissions, and reduced C 2 H 2 formation. Despite these differences, all cases display a similar heat release rate at quasi steady-state. • Methanol/n-dodecane blend ratio that yield engine-relevant IDT (< 1 ms) is evaluated. • New experimental data for methanol (ECN) and methanol/diesel/octanol blends (CRU). • LES model validation for ECN and CRU data shows promising agreement. • Methanol-rich cases show elevated NO and centreline temperature, while reduced C 2 H 2 .