燃烧流场浓度、 温度空间分布的精细测量对发动机燃烧室设计、 计算流体动力学模型建立以及数值仿真软件的验证具有重要意义, 其中平面激光诱导荧光(PLIF)技术具有对象选择性、 高测量灵敏度、 测量信息量丰富、 实验开展简单等优势, 尤其是OH-PLIF浓度及温度测量技术以其理论成熟性及技术方便性得到更为广泛的应用。 但该技术在煤油燃烧场的应用受到较大限制, 原因在于煤油燃烧场残余煤油对OH荧光信号造成较大干扰。 针对OH荧光分布测量时煤油干扰问题, 开展了OH及煤油吸收谱及荧光发射谱理论及实验对比分析。 其中煤油蒸汽吸收谱由氘卤灯通过煤油蒸汽前后的光强强度比获得, 相比于OH在260~320 nm波段的孤立吸收线, 煤油吸收为宽带吸收, 煤油吸收线完全覆盖OH激励线, 在煤油燃烧场在此波段对OH激励测量时, 激励煤油产生荧光不可避免。 另一方面, 通过调节激励波长, 测量获得OH/煤油混合荧光与煤油荧光发射谱。 煤油蒸汽荧光发射谱为中心分别位于290及340 nm的宽带信号, OH荧光主要集中于波长300~320 nm, 煤油荧光发射谱范围覆盖OH荧光, 结合吸收谱测量结果, 说明在煤油燃烧场燃烧不充分时, 在280 nm波段激励测量OH无法通过频域滤波的方式测量获得纯OH荧光信号。 通过对煤油信号的测量并扣除实现OH荧光信号的准确测量, 主要从选择性探测方面入手, 在OH荧光测量系统基础上增加一台探测相机, 采用两台ICCD相机, 分别结合(315±15)和(360±6) nm的带通滤光片进行OH/煤油混合荧光和煤油荧光的选择性探测, 通过对应点扣除的方式, 在煤油本生灯及发动机模型煤油燃烧混合荧光信号中去除煤油荧光获得了受干扰较小的OH分布结果, 证实了干扰消除方法的可行性, 为后续煤油燃烧场浓度及温度分布测量奠定了基础。

Concentration and temperature measurement are of great significance for engine design, CFD model establishment and numerical simulation verification. Planar laser-induced fluorescence (PLIF) technology has the advantages of simple experimentation, object selectivity and high measurement sensitivity. Among them, the OH-PLIF measurement of concentration and temperature is more widely applied due to their theoretical maturity and technical convenience. However, the application of OH-PLIF in the kerosene combustion field is limited because of the great interference of residual kerosene. This paper focus on the kerosene interference problem in the measurement of OH fluorescence distribution. The absorption and fluorescence emission spectra of OH and kerosene were comparative analysis. The absorption spectrum of kerosene vapor is obtained from the intensity ratio of the strontium halogen lamp before and after its pass through the kerosene vapor. Compared with the isolated absorption line of OH in the 260~320 nm band, the kerosene absorption is a wide absorption band from 240 to 320 nm. The kerosene absorption band completely covers the OH excitation line. When the OH is excited in this band in kerosene combustion, it is inevitable to stimulate the kerosene to produce fluorescence. On the other hand, kerosene fluorescence and the OH/kerosene mixed fluorescence were measured by adjusting the excitation wavelength. The kerosene fluorescence emission centered at 290 and 340 nm, while OH fluorescence is mainly concentrated at wavelength 300~320 nm. Combined with the absorption spectrum, kerosene fluorescence covers OH fluorescence indicating that the OH measurement in the 280 nm band can not be carried out by a single frequency domain filter when there are residua. In this paper, the kerosene interference was eliminated by measuring kerosene simultaneously and deducted from mixed fluorescence then. The fluorescence was detected selectively by adding an extra camera based on the ordinary OH PLIF system. The two ICCD cameras combining (315±15) and (360±6) nm bandpass filters were used for OH/kerosene mixed fluorescence and kerosene fluorescence measurement respectively. Then the OH fluorescence of a kerosene Bunsen burner and an engine model kerosene combustion was obtained by subtracting the kerosene from mixed fluorescence pixel by pixel. These results confirmed the feasibility of the kerosene interference elimination method and laid the foundation for the measurement of temperature distribution in kerosene combustion.