Combustion analysis of tetra hybrid nanocomposite catalyst-derived WCO biodiesel: Impact of glycerol carbonate on B20 blends

The present study investigates a waste cooking oil biodiesel (WCO-BD) pathway catalyzed by a novel tetra hybrid nanocomposite (THNC) catalyst (TiO 2 -CuO-Al 2 O 3 -Ag) and use of glycerol carbonate (GC) additive in a B20 blend as an oxygenated combustion improver. Combustion behaviour is examined in a single cylinder Yanmar L48N6CF1T1AA DI diesel engine at 3000 rpm and 50 % load. Diesel, WCO-BD, B20 and B20-GC blends (2-8 vol.% GC) are compared using in-cylinder pressure, net and cumulative heat release, mass fraction burnt, mean gas temperature, ignition delay and rate of pressure rise. THNC enables a biodiesel yield of 92 % and reusability was evaluated over five cycles (yield declining to 60.5 %). B20 attains a peak pressure of 61.1 bar at 10 °CA aTDC, which is 2.5 % below diesel (62.6 bar), while WCO-BD drops to 56.3 bar. GC addition progressively attenuates premixed heat release intensity during combustion i.e. B20-GC2, B20-GC4, B20-GC6 and B20-GC8 reach 60.5, 59.8, 57.9 and 57.7 bar, respectively, with cumulative heat release remaining within ±5 % of diesel. Maximum rate of pressure rise for B20-GC4 (6.65 bar °CA -1 ) increases by 8 % over diesel and 30 % over WCO-BD. Ignition delay is at 8.5 °CA for B20-GC2/GC4 but lengthens to 10.5 °CA for GC6/GC8, indicating onset of penalties in charge cooling at higher GC concentrations. The results show that lower GC concentrations (2-4 vol.%) can tune premixed burn intensity while preserving favorable pressure phasing that offer a controllable route to cleaner heat release in engines calibrated for diesel fuel. • Tetra hybrid nanocomposite catalyst achieved 92% WCO-biodiesel conversion. • B20-GC blends (2 - 8 vol.%) evaluated for detailed in-cylinder combustion behavior. • Moderate GC dosing (2 - 4%) reshaped heat-release phasing without penalizing B20. • B20 maintained diesel-like ignition, while neat WCO-BD showed slower combustion. • GC addition softened peak pressure and shifted CA50 into early expansion stroke. • Higher GC levels (6 - 8%) produced progressive combustion suitable for soot - NOx trade-offs.