Development of an Optical Sensor to Measure Direct Injection Spraying System Performance

Evaluation of direct injection sprayer’s performance is an important step for a successful direct injection sprayer technology development. A low-cost optical sensor was developed to characterize direct injection system response by dynamic measurement of fluorescent dye concentration. The method is based on sensing the fluorescence of mixture by the light-to-voltage converter equipped with integral optical green filter TSLG257. The dye is excited by one blue light LED HLMP-CB15 (emission band of 472 nm ± 32). The light transmittance was measured by the converter in two on-line positions to LED; the emitter and transmitter placed longitudinally at 45° angle and transversally at 90° angle to flow line. The measurement of transmittance for concentrations between 0 to 10 mg/l showed that the trend is linear for concentrations under 2.5 mg/l (R2 > 99%).The results showed that the offset for longitudinal measurements is bigger than for the transversal ones (about 600%) because of the direct interception of the light by the converter. The highest sensitivity is related to the transversal 90° position transmittance. The amplification of the excitation power of the LED by varying current supply between 50% and 100% gave a proportional increase of the sensitivity without affecting the linearity. Test results of sensor showed that it can be used to calibrate direct injection system accurately and to characterize the performance of the system for upstream and downstream injection location.