针对柴油机润滑油被燃油稀释的状态监测的问题, 研究了基于紫外荧光技术的柴油机润滑油被燃油稀释的检测方法, 设计搭建了检测实验装置。 利用峰值发射波长为365 nm的紫外LED作为发射光源, 发射的紫外光通过400 nm低通滤光片过滤后进入石英比色皿中的油样, 并激发油样产生荧光, 产生的荧光通过400 nm高通滤光片过滤后, 利用探测波长范围为400～800 nm的光电传感器采集油样的荧光信号, 利用万用表读取油样的荧光强度。 设计开发了信号的放大和测量系统。 高、 低通滤光片的组合使用, 减少了紫外光源所发射的紫外光对油样的荧光强度测量的干扰。 利用该实验装置, 测量了润滑油中柴油含量分别为20.3 Wt.%, 10.0 Wt.%, 5.0 Wt.%, 2.5 Wt.%, 1.5 Wt.%和0.7 Wt.%以及不含柴油的空白油样的荧光强度, 经拟合得到柴油含量与荧光强度的方程。 最后, 为了检验该方法测量润滑油中柴油含量的准确性, 采用柴油含量为7.5 Wt.%油样进行验证, 利用该实验装置, 测量了验证油样的荧光强度, 代入拟合方程, 计算得到油样中的柴油含量, 结果表明通过该方法测量的油样中柴油含量与油样的实际柴油含量的相对误差为0.5%, 实现了实验室条件下润滑油被燃油稀释的精确测量。

Aiming at the condition monitoring problem of Diesel engine lubricating oil diluted by fuel, an experimental measuring apparatus was designed and completed to detect fluorescence intensity of oil samples by UV fluorometry. An UV LED with peak wavelength of 365 nm as emitting light source was chosen for exciting oil sample to produce fluorescence. Ultraviolet light from emitting light source passed through a 400 nm optical low pass filter and went into oil samples in quartz colorimetric utensil. Oil samples excited by ultraviolet light may produced fluorescent light. Firstly, fluorescent light was filtered by 400 nm optical high pass filter. And then filtered fluorescent light was transformed into electric signal by the photoelectric sensor with the detection wavelength range from 400 to 800 nm. After amplified by measurement circuit , digital multimeter can be used to detect the fluorescent light intensity. The signal amplification and measurement system were designed. The combination of optical high and low pass filters can reduce the interference of the ultraviolet light emitted by the ultraviolet light source to the fluorescence intensity of oil samples. Fluorescence intensity data of seven oil samples with different fuel concentrations of 20.3 Wt.%, 10.0 Wt.%, 5.0 Wt.%, 2.5 Wt.%, 1.5 Wt.%, 0.7 Wt.% and 0.0 Wt.% were obtained by the experimental apparatus as the above mentioned. The fitting equation of fuel concentration with fluorescence intensity was acquired. Finally, the oil sample of 7.5 Wt.% diesel oil content was used to verify the accuracy of the method. The fluorescence intensity of verifying oil sample was measured by the experimental apparatus. The ration of fuel to oil was calculated by fitting equation. The results showed that the ration of fuel to oil relative error between the calculated and the actual was 0.5%. The accurate measurement of the dilution of lubricating oil by fuel under the laboratory condition was realized.