Fiber Optic Sensors Design And Experimental Research On Key Parameters Of Large Diesel Engine Condition Monitoring

Efficient operation of large diesel engine can not do without the comprehensive perception of key parameters through engine condition monitoring system. The key parameters contain the state information in the operation of diesel engine:Vibration parameter is the carrier of health information, and the monitoring of this aspect is also the main method of engine fault diagnosis. Flow parameter is the carrier of power information, the monitoring of this aspect based on the gas input to adjust the volume of oil in the combustion chamber determines the performance of the engine. Now, The most of diesel engine condition monitoring system is based on the traditional electrical sensor technology, but the sensing signal is sensitive to disturbance causing measurement errors because of the bad working conditions of the diesel engine. In contrast, optical fiber sensors are immune to electromagnetic interference and intrinsically safe, so they have a natural advantage for applications in harsh environments. Therefore, it is extremely important to apply the optical fiber sensing technology in the monitoring of the state parameters of the diesel engine.Under the application backgrounds of the large diesel engine condition monitoring, the research centers on vibration and flow key parameters. Based on the fiber optic sensing technology, this paper conducts model-building and deduction, structure design and simulation of acceleration sensor and flow velocity sensor. According to the design, sensor physical objects are produced and are tested by experiments.Aimed at the vibration parameters, the design research direction is lever cantilever beam structure on the basis of the summary of the research status. Firstly, we establish a preliminary model of vibration sensing and deduce three parts of the model which are its output response, mechanical fine adjustment device and prestressing force. We utilize ANSYS software to carry out simulation analysis, including modal analysis, static and dynamic response analyses, harmonic response simulation and lateral disturbance analysis, for calculating the theoretical performance parameters of the sensor. Then according to the theory of parameter, we optimize the vibration sensing model, draw the blueprint and manufacture the sensor physical objects. Finally, we conduct the testing experiment and research for sensors, including the standardizing calibration experiments, the transient impact experiments and the testing of engine vibration condition monitoring with application. The experimental results show that the sensitivity of the sensor can reach 75.6 pm/(m/s2) (100Hz), the linearity error is less than 2.31%, the repeatability error is under 2.76%, the lateral disturbance sensitivity is less 5% than the response sensitivity, the dynamic range is about 70 db, the resonance frequency is around 138 Hz, the system damping coefficient is low, those above verify the feasibility of the sensor applying to the engine vibration condition monitoring.Aimed at parameters of inlet gas flow, combined with force analysis of the fluid, a new cantilever structure velocity sensor based on surface stress is designed. First of all, the sensing model was deduced, and results show that:PDMS silicone material is more suitable for measuring air velocity than the metal material.Secondly, the ANSYS software is used to simulate the fluid structure interaction, and the static theoretical performance parameters are obtained. Then, based on the theoretical parameters, the flow sensing model is optimized, and the optical fiber velocity sensor is made. In the end, the simulation of the engine intake flow monitoring and standardized calibration experiment are carried out. The experimental results show that the sensitivity of the flow sensor is high, and its sensitivity coefficient is about 13.7. The output wavelength shift of the flow sensor is proportional to the square of velocity. The hysteresis of the flow sensor is 3.7% and the system damping ratio is greater than 1, which verifies the feasibility of the sensor in the air flow monitoring.At last, the research work of this paper is summarized, and the paper puts forward the place which needs to improve according to the practical problems encountered in the experimental test.