燃油发动机的尾气成分检测对于发动机的状态判断、 环境污染监测等具有重要参考价值。 选择以95号汽油为燃料的除草机的发动机作为实验样机, 将发动机排出的尾气直接吹向拉曼积分球光谱仪信号采集焦点, 利用拉曼积分球光谱仪较高的气体检测限和定性、 定量检测所有分子类气体的特点, 对尾气中的气体分子成分进行检测。 探测到尾气的气体成分主要包括N₂、 O₂、 CO₂、 CO、 未燃烧的汽油等。 以氮气振动(2 331 cm^-1)的拉曼特征峰强度作为标准, 对O₂(1 553 cm^-1)、 CO₂(1 285和1 388 cm^-1)、 CO(2 144 cm^-1)、 未燃烧的汽油(2 894 cm^-1)的拉曼光谱强度进行归一化处理, 获得其相对拉曼特征峰强度。 对比发现, 空气和汽油挥发混合气的光谱中均未出现CO的特征峰, 汽油挥发混合气中的O₂、 CO₂含量与空气相比也没有明显变化, 而CO₂费米共振峰1 388和1 285 cm^-1拉曼特征峰的相对强度比发生变化。 除草机工作状态分为怠速、 一档和二档, 处于工作状态时, 尾气成分中的O₂含量均比空气中含量低, 可以定量分析发动机工作过程中消耗的O₂量。 而燃油发动机从怠速加速到一档和二档的过程中, 尾气中O₂含量相对增加。 这是由于发动机档位的提升伴随着空气的进气量增大, 则参与发动机燃烧的氧气比例相对减少。 与此同时, 尾气中CO₂含量相比于空气中的含量急剧增加, 说明燃油发动机工作过程会产生大量的CO₂, 且随着档位的提升, 发动机的动力增加, 尾气中CO₂比例也逐渐增高。 CO₂作为导致温室效应的主要原因, 化石燃料的使用也是其主要来源之一。 数据显示尾气中CO的含量与尾气中汽油的含量成正相关, 说明燃烧不充分的时候, 汽油剩余较多, CO作为不充分燃烧的产物, 其含量也会增加。 随着发动机档位的增加, N₂特征峰的绝对强度降低, 这是因为发动机尾气温度升高, 造成氮气的斯托克斯散射强度降低。 利用拉曼积分球光谱仪对不同状态下发动机尾气成分的变化进行分析, 并初步建立发动机状态与气体浓度变化的关系。 对拉曼积分球技术应用于燃油发动机尾气检测进行了初步探索并验证了其可行性。

The detection of the exhaust gas components of a fuel engine has important reference values for engine condition determination and environmental pollution monitoring. For this study, a weedkiller engine powered by No.95 gasoline was chosen as the experimental prototype, and the exhaust gas from the engine was blown directly into the signal acquisition focus of the Raman integrating sphere spectrometer. The high gas detection limit and the ability of the Raman integrating sphere spectrometer to probe all molecular gas qualitatively and quantitatively have been used to probe the molecular component of the gas in the tails. The gas component detected in the trailing gas is dominated by N₂, O₂, CO₂, CO, and unburned gas. The relative Raman characteristic peak intensities of O₂ (1 553 cm^-1), CO₂ (1 285 cm^-1 and 1 388 cm^-1), CO (2 144 cm^-1), and unburned gasoline (2 894 cm^-1) were obtained by normalizing the Raman spectral intensities using the Raman characteristic peak intensity of nitrogen vibrations as a standard. It can be found that the characteristic peak of CO does not appear in the spectrum of volatile matter of air and gasoline, and the content of O₂ and CO₂ in volatile matter of gasoline does not change significantly compared with that of air, while the relative intensity ratio of Raman characteristic peak of CO₂ Fermi formant 1 388 and 1 285 cm^-1 change. The working state of a lawnmower is divided into idler, first and second gear. When operating, the O₂ content in the exhaust components is all below that in the air, allowing quantitative analysis of the amount of O₂ consumed during engine operation. The O₂ content in the exhaust increases relatively when the fuel engine is increased from idle to first and second gear. It is because as the engine gear increases, so does the air intake, and the proportion of oxygen involved in engine combustion is relatively reduced. At the same time, the amount of CO₂ in the tailpipe gas increases dramatically compared to the amount in the air, suggesting that the working process of the fuel engine produces large amounts of CO₂. The proportion of CO₂ in the tailpipe gas gradually increases as the gear is raised and the engine power is increased. One of the main sources of CO₂, the main cause of the greenhouse effect, is the use of fossil fuels. The data shows a positive correlation between the amount of CO in the tail gas and the amount of gasoline in the tail gas, suggesting that when combustion is insufficient, there is more gasoline left, and the amount of CO as a product of insufficient combustion also increases. With increasing engine gear, the absolute intensity of the characteristic peak of N₂ decreases due to the decrease of the Stokes scattering strength of nitrogen with increasing engine exhaust temperature. In this paper, the Raman integrating sphere spectrometer is used to analyze the changes engine exhaust composition under different conditions. Moreover, the relationship between engine state and gas concentration is preliminarily established. We explore the application of Raman integrating sphere technology to fuel engine exhaust detection and verify its feasibility.