Development And Application Of The Piston Surface Temperature Telemetry System In Internal Combustion Engines

The temperature data of piston surface in internal combustion engine are important basic data for piston thermal load evaluation and reliability design as well as combustion and heat transfer analysis.However,it is very difficult to measure piston surface temperature due to the complex structure of internal combustion engine and the bad working environment of piston.In order to solve this problem,the fabrication of microsecond fast response thermocouple and its introduction error in measuring piston surface temperature are systematically studied in this paper.A high-speed wireless temperature measuring control device is developed,and a telemetry system for piston surface temperature of internal combustion engine is integrated and developed.A series of tests and experiments are completed.First of all,based on the cycle of transient characteristics of piston surface temperature,and the special requirements such as closed,high pressure resistance,high temperature resistant,based on the parallel wire thin-film thermocouple and coaxial thin-film thermocouple two kinds of structure,analyzes its core insulation technology research,including the PECVD chemical vapor deposition technique SiO2 insulator,precision machining insulating substrate,internal and external electrode insulation potting epoxy resin,finally optimize the proposed parallel wire thin-film thermocouple structure with Al2O3 processing plan of the insulating substrate,and the thermocouple samples are developed.The results of static and dynamic calibration experiments show that the Seebeck coefficient of the parallel conductor thin film thermocouple is 47.6 μ V/ ℃,the thermoelectric potential and temperature show a strong linear relationship,and the dynamic response time is 0.38 ms.Secondly,based on three-dimensional heat transfer simulation model,,aiming at the introduction error of thermocouple contact temperature measurement,the introduction error of thermocouple contact temperature measurement was quantitatively defined,the introduction error evaluation index system was established,and the introduction error of typical thermocouple measurement of 42 Cr Mo piston surface temperature was compared and analyzed.The results show that the introduction error of transient temperature measurement decreases with the increase of installation depth in the case of blind hole installation.In the case of through hole installation,When the thermal diffusivity of the coupling wire is consistent with that of the measured piston,and the thermal diffusivity of the matrix and casing is slightly larger than that of the measured piston,the introduction error is the least.In order to reduce the introduction error of thermocouple temperature measurement,the matching design method of thermocouple with the introduction error minimization and the introduction error correction algorithm were proposed.Finally,for the internal combustion engine piston closed,high temperature,strong vibration,strong electromagnetic interference environment,developed a set of piston surface transient temperature telemetry system,to achieve the goal of collecting temperature information at 105℃ ambient temperature,8 channels of 10 k Hz sampling frequency.The temperature resistance,vibration resistance and durability tests,as well as the engine test,are carried out.The experimental results show that the temperature measuring system can reliably measure the transient temperature of the piston,and that the temperature of the measuring point increases with the increase of the engine speed under constant torque.At constant speed,with the increase of torque,the temperature of the measuring point increases gradually.To sum up,this paper successfully developed the internal combustion engine piston surface transient temperature telemetry system,including a response time of 0.38 ms,temperature resistance of about 500℃ thermocouple;8 channel high frequency collector and real-time display,storage data of the upper computer.The system can measure the piston surface temperature,which provides a solid foundation for the improvement and upgrade of the transient temperature telemetry system.