Abstract:
Third-generation microalgae are considered superior to other biodiesel feedstocks. Biomass
to-liquid (BTL) diesel, a renewable fuel, has emerged as a promising alternative for
transportation due to its unique properties that enhance engine performance and reduce NOx
emissions compared to conventional biodiesel. This study presents a numerical investigation
into the effects of neat BTL diesel and four BTL diesel-microalgae biodiesel blends, prepared
by mixing 20, 40, 60, and 80 vol% microalgae biodiesel into BTL diesel on the performance
of a single-cylinder diesel engine. The study employs the RK multi-zone combustion model to
simulate engine behavior across five injection timings (ITs) and validated against reliable
experimental data. Neat BTL diesel demonstrated improved engine performance and exhaust
characteristics compared to conventional diesel, except for NOx emissions. The ignition delay,
combustion duration, and premixed peak heat release rate for the microalgae-BTL blends
increased by 11.04–67.24%, 0.66–13.03%, and 5.25–29.87%, respectively, while peak
cylinder pressure decreased by 0.72–5.26% relative to pure BTL diesel. The microalgae-BTL
blends caused brake-specific fuel consumption to rise by 2.14–7.51% across all ITs. Brake
thermal efficiency decreased by 0.2–1.6% for ITs between 1° and 4° CA bTDC, but increased
for ITs between 7° and 13° CA bTDC with higher biodiesel content in the blends. Additionally,
the microalgae blends reduced CO2, particulate matter (PM), and smoke emissions; however,
the increased NOx emissions compared to neat BTL diesel. The optimum IT is identified as 4°
CA bTDC for improved performance and reduced PM and smoke with an acceptable NOₓ
trade-off.
