正丁醇是一种很有前景的柴油替代燃料, 针对缸内火焰发展和燃烧中间产物的自发光光谱开展研究, 有助于深入理解柴油掺混正丁醇混合燃料对柴油机燃烧过程的影响规律。 因此, 在一台光学发动机上, 利用火焰高速成像技术和自发光光谱分析法, 研究纯柴油与柴油掺混不同比例正丁醇后对发动机缸内火焰发展和自发光光谱的影响。 试验过程中, 光学发动机转速为1 200 r·min-1, 喷油压力为600 bar, 进气加热到398 K, 使上止点附近达到约900 K温度。 纯柴油、 柴油掺混20%正丁醇燃料和柴油掺混40%正丁醇燃料分别用D100, DB20和DB40表示, 三种燃料在每个着火循环喷入的油量分别为17.5, 18.7和19.2 mg, 从而保证发动机输出功相同。 试验结果表明: 冷却水温不变时, 喷油时刻推迟, 滞燃期缩短, 初始火核形成时刻推迟, 蓝色预混火焰比例减小； 喷油时刻不变时, 提高冷却水温度, 滞燃期缩短, 初始火核形成时刻提前, 蓝色预混火焰比例减小。 随着正丁醇掺混比例增加, 呈现局部混合气率先着火的特征且着火时刻推迟, 蓝色预混火焰比例增加, 火焰亮度降低, 火焰亮度从大到小依次为: D100＞DB20＞DB40。 D100燃料随喷油推迟, 整体光谱的峰值向长波方向移动, 碳烟辐射增强, OH谱带的光强峰值先增大后减小, OH和CH2O谱带出现的时刻推迟, 表明高温和低温反应时刻推迟； 喷油时刻不变时, 提高冷却水温, 整体光谱的光强增加, OH和CH2O谱带的出现时刻提前, 表明高温和低温反应时刻提前。 掺混正丁醇后的DB40燃料随喷油推迟, 光谱的整体光强增加, OH和CH2O谱带的光强峰值提高, 表明推迟喷油对DB40燃料也是有助于促进高温和低温反应。 DB40燃料光谱的整体光强低于D100燃料, 其OH和CH2O的谱带出现的时刻迟于D100燃料, 表明掺混正丁醇后燃料的高温和低温反应时刻都相对D100燃料推迟。 SOI-15、 冷却水温95 ℃工况下, D100燃料的谱线经过2 ℃A就呈现出了类似碳烟黑体辐射谱的特征, 而DB40燃料先呈现出CO氧化连续谱的特征, 经过15 ℃A才呈现碳烟黑体辐射谱的特征。

N-butanol is a promising alternative fuel for diesel. The study on the self-luminosity spectra of combustion intermediates and flame development in diesel engine cylinder was helpful to understand the influence law of diesel blended n-butanol deeply on the combustion process in diesel engine cylinder. Therefore, this paper used the high-speed flame imaging technology and self-luminosity spectroscopy analysis to study the effects of pure diesel and diesel blending n-butanol on the flame development and self-luminosity spectrum of the engine cylinder on an optical engine. During the test, the optical engine speed was 1 200 r·min-1, with an injection pressure of 600 bar and an intake air heating to 398 K, bringing the temperature around the top dead center to approximately 900 K. Pure diesel, diesel blended with 20% n-butanol fuel and diesel blended with 40% n-butanol fuel were represented by D100, DB20 and DB40 respectively. The injection masses of D100, DB20 and DB40 were respectively 17.5, 18.7 and 19.2 mg per fired cycle to ensure the same engine output. The experiment results show that when the cooling water temperature remains unchanged, with a delayed start of fuel injection (SOI), the ignition delay is shortened, the initial fire nucleus formation time is delayed, the blue premixed flame proportion is reduced; when the SOI remains unchanged, with the increase of cooling water temperature, the ignition delay is shortened, the initial nucleus formation time is advanced, the proportion of blue premixed flame decreases. With the increase of n-butanol blending ratio, the characteristic of the local mixture is first ignited, the ignition time is delayed, the proportion of blue premixed flame increases, and the flame luminosity of fuel decreases. The luminosity of the flame is from D100>DB20>DB40. For D100 fuel, with delayed injection, the peak of the whole spectrum shifts to a larger wavelength direction, soot radiation is enhanced, the peak light intensity of the OH band first increases and then decreases, and the occurrence time of the OH band and the CH2O band is delayed, indicating the high temperature and the low temperature reaction delayed. When the SOI remains unchanged, with the increase of cooling water temperature, the light intensity of whole spectrum increases and the occurrence time of OH and CH2O bands is ahead of schedule, indicating the high temperature and the low temperature reaction advanced. With the SOI delay, the whole light intensity of the spectrum of DB40 fuel after the diesel blended with n-butanol, increases, the peak light intensity of the OH band and the CH2O band increases, which means that delaying injection to DB40 fuel also helps to promote high temperature and low temperature reactions. The whole intensity of the DB40 fuel spectrum is lower than that of D100 fuel, and the occurrence time of OH and CH2O bands appear later than D100 fuel, indicating that both the high temperature and the low temperature reaction of the fuel after the addition of n-butanol are delayed relative to the D100 fuel. Under the condition of SOI-15 and cooling water temperature of 95 ℃, the spectrum of D100 fuel exhibits similar characteristics of the soot blackbody radiation spectrum after 2 ℃A, while DB40 fuel first exhibits the characteristics of CO oxidation continuous spectrum, then the characteristics of the soot blackbody radiation spectrum are exhibited after 15 ℃A.