Multifaceted assessment of the combustion, vibration, and noise characteristics of a single-cylinder diesel engine fuelled with low carbon alcohol, biodiesel, and diesel ternary blends

• Methanol addition (≤ 20%) enhanced premixed combustion and reduced NHRR compared to diesel. • Cylinder block vibrations exceeded crankcase vibrations due to combustion-induced shock transmission. • Higher methanol content reduced overall noise levels, despite localized exhaust-side NPL increases. • B30M20D50 favoured combustion performance, while B20M30D50 offered the best NVH compromise. The dwindling supply of fossil fuels and their negative environmental impact motivate the search for alternative diesel fuels. Waste fried oil (WFO) biodiesel is a more sustainable and eco-friendly option for the alternative fuel. Adding methanol to WFO biodiesel enhanced its fuel properties. This study aims to analyse the combustion behaviour of ternary fuel blends with a higher methanol concentration. It further examines the vibration characteristics of the engine at different locations and along three orthogonal axes over a frequency range of up to 2048 Hz. The study is performed in a single-cylinder diesel engine. Engine vibrations were measured by mounting accelerometers on the cylinder block and crankcase, while noise emissions were recorded using microphones positioned on both sides of the engine. At mid- and full-load, the B30M20D50 produced 63.07 bar and 71.37 bar peak cylinder pressure, while the diesel produced 62.72 bar and 70.65 bar. The vibration levels of the engine were correlated with the rate of heat release during combustion. Higher heat release rates led to increased vibration in the crankcase and cylinder block. The engine's exhaust side produced more noise than the flywheel. At peak load, the exhaust from B20M30D50, B30M20D50, and B40M10D50 produced 2.48%, 3.86%, and 3.29% more noise than diesel, while the flywheel side produced 1.84%, 3.14%, and 2.35% more noise than diesel. While B30M20D50 exhibited superior combustion performance due to the beneficial influence of methanol, higher methanol content reduced noise and vibration, making B20M30D50 the more favourable blend in terms of NVH characteristics.