Di-ethyl ether-diesel blends fuelled off-road tractor engine: Part-II: Unregulated and particulate emission characteristics
Abstract
The use of oxygenated fuels, including ethanol, methanol, diethyl ether (DEE), and dimethyl ether (DME) in CI engines has emerged as an effective way to reduce CO, HC, and PM emissions. DEE, in particular, has significant potential to be used in CI engines. Unlike DME, it exists as a liquid state at room temperature and pressure, making its handling very smooth. In this experimental study, DEE-diesel blends were used to power an off-road tractor engine. Previous studies investigated the performance and regulated emission characteristics of DEE-fueled vehicles/ engines; unregulated emissions and particulate characteristics were not studied thoroughly. This study, therefore, investigates the effect of DEE-diesel blends on unregulated and particulate emissions from the engine. Unregulated pollutants investigated in this study include individual oxides of nitrogen (NO, NOx, NO2), saturated and unsaturated hydrocarbons (n-pentane (n-C5H12), n-octane (n-C8H18), iso-butene (iso-C4H8)), and organic and inorganic species (Sulphur dioxide (SO2), formic acid (HCOOH) and formaldehyde (HCHO)). Particulate emission characteristics include total particle mass (TPM), total particle number (TPN), particulate mass-size distributions, and count mean diameter (CMD). Four test fuels were used in this study namely: DEE0, DEE15, DEE30 and DEE45 (0%, 15%, 30% and 45% DEE (v/v) blended with mineral diesel). The results from DEE-diesel blends were compared with baseline mineral diesel (DEE0). The experiments were conducted at a constant engine speed of 1500 rpm at varying engine loads. At all engine operating conditions, DEE-diesel blends resulted in significantly lower TPN compared to baseline mineral diesel. A similar trend was observed for TPM; however, DEE15 showed slightly higher TPM than baseline mineral diesel. Emissions of individual oxides of nitrogen were also relatively lower than baseline mineral diesel. The addition of DEE in mineral diesel exhibited a slight increase in unregulated emission species concentrations such as formaldehyde, formic acid, sulfur dioxide, n-pentane, n-octane, iso-butene. However, the absolute concentration levels were still quite low. This study concluded that DEE could potentially displace mineral diesel partially, without any changes in fuel injection equipment, and achieve an improvement in PM-NOx trade-off in off-road transport diesel engines.