Impact of fuel spray angles and injection timing on the combustion and emission characteristics of a high-speed diesel engine

• Effect of narrow spray angle injector on combustion and emission was investigated.
• Peak combustion pressure in 60° injector is higher than that in 156° injector.
• Peak heat release in 60° injector is higher than that in 156° injector.
• Using narrow angle injector can reduce HC and CO emission.
• Using narrow angle injector can improve ISFC and IMEP characteristics.

This paper presents effect of fuel spray angles such as narrow (60°) and conventional (156°) spray angles on spray behavior, combustion and emissions characteristics. To achieve research objectives, fuel spray images measured using a visualization system and two injectors at spray angles of 60° and 156° were analyzed for spray tip penetration and spray development processes as a function of injection timing and injection pressure. The spray angle effects on combustion and emission characteristics, and engine performance were analyzed.Results revealed that 60° injector exhibited higher maximum combustion pressure, higher maximum heat release rate, and lower ignition delay than 156° injector. Under various injection timings with 156° spray angle, it is shown based on the experimental results that peak value of combustion pressure decreased when injection timing of 30° BTDC (before top dead center) was advanced. Regarding emission characteristics, the use of narrow spray angle injector is advantages in case of an early injection combustion strategy because it yields low ISHC (indicated specific hydrocarbon), ISCO (indicated specific carbon monoxide), and ISNOx (indicated specific nitrogen oxides) emissions. In addition, the IMEP (indicated mean effective pressure) in a narrow spray angle injector is higher than that in conventional spray angle injector.