An optical diagnostic, based on laser-induced fluorescence (LIF), has been developed for on-engine measurements of real-time fuel dilution of engine oil, or fuel in oil (FiO). Fuel dilution of oil is broadly relevant to advancing engine technology including durability, calibration, and catalyst-system management, and believed to promote destructive stochastic pre-ignition (SPI) during high-load engine operations. While standard (e.g., ASTM D3524-90) methods are not capable of real-time transient measurements, the LIF technique resolves transient dilution on the minutes time scale. We have expanded on our original FiO instrument development by introducing an improved analysis based on multivariate least square chemometrics analysis. The measurement uses a fuel dye (180-1300ppm by mass), and monitors for its presence in the oil via 532-nm excitation and LIF. While the original FiO instrument utilized a two-color ratio method for analysis, the improved chemometric analysis uses the fully resolved LIF dye spectra to provide better predictive FiO accuracy (> 92%) over a wide FiO range (1.5-14%) typical of engine application. We also investigate the effect of oil temperature on the LIF signal. Limited engine applications for demonstrating and validating the improved FiO instrument are shown, and the related data used to quantify practical detection limit and sensitivity. The improved analysis is insensitive to laser power fluctuation and change in detector integration time, providing an excellent FiO sensitivity (1-2%) and detection limit (0.01 %FiO) over a wide range of loads and injection timings, illustrating this updated approach to be a promising tool for advancing engine technology.

已经开发了一种基于激光诱导荧光 (LIF) 的光学诊断方法，用于在发动机上测量发动机油或油中燃料 (FiO) 的实时燃料稀释。油的燃料稀释与推进发动机技术（包括耐用性、校准和催化剂系统管理）广泛相关，并且被认为会在高负荷发动机运行期间促进破坏性随机提前点火 (SPI)。虽然标准（例如，ASTM D3524-90）方法不能进行实时瞬态测量，但 LIF 技术可以解决分钟时间尺度上的瞬态稀释问题。我们通过引入基于多元最小二乘化学计量学分析的改进分析，扩展了我们最初的 FiO 仪器开发。测量使用燃料染料（按质量计 180-1300ppm），并通过 532 nm 激发和 LIF 监测其在油中的存在。虽然最初的 FiO 仪器使用双色比方法进行分析，但改进的化学计量分析使用完全分辨的 LIF 染料光谱，在较宽的 FiO 范围 (1.5-14%) 内提供更好的预测 FiO 准确度 (> 92%)发动机应用。我们还研究了油温对 LIF 信号的影响。展示了用于演示和验证改进的 FiO 仪器的有限引擎应用，以及用于量化实际检测限和灵敏度的相关数据。改进的分析对激光功率波动和检测器积分时间的变化不敏感，在广泛的负载和注射时间范围内提供出色的 FiO 灵敏度 (1-2%) 和检测限 (0.01 %FiO)，