Influence of 1-butanol and 1-pentanol addition to diesel fuel on exhaust and noise emissions under stationary and transient conditions

There is a growing interest in using long-chain alcohols, i.e. butanol and pentanol, in the transport sector, as a consequence of their potential production from residual biomass via fermentative processes. There is evidence that incorporation of alcohols to diesel fuel enables to overcome the well-known smoke-NOx trade-off under steady state compression ignition engine operation. Nevertheless, the impact of long-chain alcohols under engine transient conditions is not understood and their behavior under Worldwide Harmonized Light Vehicles Test Procedure (WLTP) cycle has not been reported. This investigation addresses the above-mentioned research gaps by characterization of noise and exhaust emissions (CO, total hydrocarbon content or THC, NOx and particulate matter or PM mass, PM number and PM distribution) of a diesel engine running on ultra-low sulfur diesel (ULSD) fuel and its mixtures with 1-pentanol and 1-butanol under stationary and transient conditions (WLTP). Transient PM number, mass and size distribution have been monitored using Dekati electrical pressure low impactor ELPI + coupled by Dekati Fine Particle Sampler FPS-4000, whereas transient gaseous emissions have been measured with Horiba Mexa 7100D. Increasing the long-chain alcohol content in fuel blends, significantly reduces PM number and mass for both stationary and WLTP tests, being mainly attributed to oxygen content of 1butanol and 1-pentanol. Addition of long-chain alcohols causes a decrease of emitted NOx in stationary operation, but the opposite trend was found under WLTP. Noise levels seem to slightly increase with the use of higher alcohol/ULSD fuel mixtures. Overall, it may be concluded that utilization of higher alcohol/ULSD fuel blends appears as a favorable substitute to straight ULSD fuel.

Automated summary

The study found that incorporating long-chain alcohols in fuel can significantly reduce particulate matter mass and number, and decrease NOx emissions in stationary operation of diesel engines, but exhibit an opposite trend under WLTP cycle conditions. Noise levels appear to slightly increase, and overall, the utilization of higher alcohol/ULSD fuel blends seems to be a favorable substitute to straight ULSD fuel.