Direct injection spark ignition (DISI) engines have been widely used in passenger cars due to their lower fuel consumption, better controllability, and high efficiency. However, DISI engines are suffering from wall wetting, imperfect mixture formation, excess soot emissions, and cyclic variations. Applying a new fuel atomization technique and using biofuels with their distinctive properties can potentially aid in improving DISI engines. In this research, the effects of isobutanol and 2-butanol and their blends with Toluene Primary Reference Fuel (TPRF) on spray characteristics, DISI engine combustion, and particle number (PN) emissions are investigated for conditions with and without flash boiling of the injected fuel. Spray characteristics are investigated using a constant volume chamber. Then, the combustion, flame propagation, and PN emissions are examined using an optical DISI engine. The fuel temperature is set to 298 K and 453 K for liquid injection and flash boiling injection, respectively. The tested blending ratio is 30 vol% butanol isomers and 70 vol% TPRF. The results of the spray test reveal that liquid fuel plumes are distinctly observed, and butanol blends show a slightly wider spray angle with lower penetration length compared to TPRF. However, under flash boiling injection, the sprays collapse towards the injector axis, forming a more extended single central vapor jet due to the plumes' interaction. Meanwhile, butanol blends yield a narrow spray angle with more extended penetration compared to TPRF. The flame visualization test shows that the flash boiling injection reduced yellow flames compared to liquid fuel injection, reflecting the improvements in mixture formation. Thus, improvements were noted in the heat release and PN emissions. Butanol addition reduced the PN emissions by 43% under regular liquid injection. Flash boiling injection provided an additional 25% reduction in PN emissions.

直喷火花点火（DISI）发动机因其较低的燃油消耗，更好的可控制性和高效率而被广泛用于乘用车中。但是，DISI发动机遭受壁湿，混合物形成不完善，烟尘排放过多和周期性变化的困扰。应用新的燃料雾化技术并使用具有独特性能的生物燃料可能会有助于改善DISI发动机。在这项研究中，研究了在有和没有喷射沸腾的条件下，异丁醇和2-丁醇及其与甲苯主要参考燃料（TPRF）的混合物对喷雾特性，DISI发动机燃烧和颗粒数（PN）排放的影响。燃料。使用恒定容积的腔室研究喷雾特性。然后，燃烧，火焰传播，使用光学DISI引擎检查PN排放。对于液体喷射和闪蒸喷射，燃料温度分别设置为298 K和453K。测试的混合比例为30体积％的丁醇异构体和70体积％的TPRF。喷雾测试的结果表明，可以清楚地观察到液体燃料羽流，并且与TPRF相比，丁醇混合物的喷雾角度略宽，穿透长度较低。然而，在快速沸腾喷射下，由于羽流的相互作用，喷雾朝着喷射器轴线塌陷，形成了更延伸的单个中央蒸气射流。同时，与TPRF相比，丁醇共混物产生的喷雾角度更窄，渗透性更强。火焰可视化测试表明，与液体燃料喷射相比，闪蒸喷射减少了黄色火焰，反映混合物形成的改善。因此，注意到在放热和PN排放方面有所改善。在常规液体注入下，添加丁醇可将PN排放量降低43％。闪蒸注入使PN排放降低了25％。