Combustion Stability Analysis of Liquid Biofuels using Acoustic Signals

Abstract

Biodiesel and vegetable oil suffer from higher viscosity and boiling point resulting in poor atomization and evaporation rate compared to diesel fuel additional to the lower heating value which negatively affect the stability of flame. The unsteady heat release rate from flame provides unique pressure wave signature that can be captured as acoustic wave. A pressurized combustion chamber was developed and connected to a vehicular turbocharger to test combustion stability and emissions of wide range of liquid biofuels. Biodiesel and blends of palm oil/diesel from 10% (Vol.%) up to 100% pure palm oil (i.e. P10-P100) were investigated and compared to diesel as the benchmark fuel. Microphone probes at the chamber inlet and outlet were used to capture the acoustic signals to be analyzed through the Fast Fourier Transform (FFT) using MATLAB program. The analysis of the acoustic signals revealed distinguishable deviation patterns between diesel and other biofuels which showed close resemblance to the carbon monoxide (CO) emission patterns at the same operating pressures. Biodiesel was comparable to P20, while increasing palm oil blend resulted in higher deviation. Chamber pressure also showed positive effect on combustion stability and reduced the deviation between diesel and other biofuels.