Experimental investigation on combustion and emission characteristics of Fischer-Tropsch diesel/gasoline in a multi-cylinder heavy-duty diesel engine under different loads

•Effects of F-T diesel/gasoline blends on combustion and emission are studied.•FTG20 has higher premixed combustion than FT100 but lower than D100.•At high loads, FT100 has higher BTE than D100, and FTG20 shows further improvements.•FT100 displays significantly lower ultrafine PN than D100.•Aromatics, unsaturation and pool-fire of gasoline at high loads cause worse PN. To compare the combustion and emission characteristics of petroleum diesel (D100), Fischer-Tropsch diesel (FT100, indirect coal-to-liquid) and 80% F-T diesel blended with 20% petroleum gasoline by volume (FTG20), the three fuels were applied in a 6-cylinder heavy-duty diesel engine under different loads. The results show that the lowest premixed combustion is found for FT100, followed by FTG20 and D100, ranked in the descending order of ignitability. FT100 has higher BTE than D100 at high loads with single injection strategy. Adding gasoline to F-T diesel enhances fuel–air mixing quality and thus further increases BTE. However, too early pilot injection at low loads for FT100 and FTG20 is not beneficial to BTE improvement. Moreover, FTG20 has the highest BSHC and BSNOx at all loads. FT100 shows slightly higher BSHC and BSNOx at low loads with split injection, while lower BSNOx and similar BSHC at high loads with single injection than D100. In addition, FT100 has lower number concentration and geometric mean diameter (GMD) of ultrafine particulates (UFPs) than D100 at all loads. With the addition of gasoline, both of GMD at all loads and number concentration at low loads further decrease, but the aromatics, unsaturation and pool fire of gasoline lead to deteriorated ultrafine number concentration at high loads. With further addition of PODE to FTG20, the deteriorating UFPs at high load are improved. The results indicate that the addition of gasoline to FT100 can effectively improve BTE and reduce GMD of UFPs, but BSCO, BSNOx and number concentration at high loads are worsened, and PODE can be selected as a potential additive to reduce the UFPs at high loads.