Study On The Device Of The Steady-state Temperature Measurement Of The Piston By Storage

When the turbocharger technology and fuel with high pressure common rail system was used in internal combustion engine and engine power density increased the heat load and mechanical load increased in components of the engine combustion chamber. Piston is an important component to bear the heat load and mechanical load, and the ablation phe-nomena in the piston occur frequently. It is an important means to solve the ablation prob-lem in the piston by knowing temperature distribution in the piston when engine is run-ning. But the piston is a high-speed reciprocating motion parts, it is very difficult to meas-ure piston temperature, but also it is one of the focuses in engine testing technology.In this paper, a new device of steady state temperature measurement of piston by sto-rage was developed, including temperature trigger switch, cruise switch module and memory module. It is the small size and light weight to become true, the piston tempera-ture measurement went to practical application. The use of the trigger switch in the device made effectively manage the power and the measurement system switch between high-power and low-power. It extended the effective working time of the device and solved the problem that the power was short in temperature measurement device using volt memory. Cruise switch module effectively reduced the volume of the test system, and multiple measuring points were installed in the piston. Thermocouple low-temperature junction compensation circuit integrated in the cruise Switch module could measure the temperature in the thermal box in real-time, it is used to compensate low temperature end of the thermocouple, at the same time, to determine whether the system steadily worked. Holder and the thermal insulation temperature of the box makes the test system and the piston fixe together, there was no relative motion between thermocouple wire with tem-perature measurement system, improving reliability of thermocouple piston temperature measuring. Based on the measured data, the temperature in adiabatic Insulating box was below 90℃and it ensured chip to reliably operate.The error of system was calibrated in high temperature condition at 75℃,100℃, 120℃,135℃. The results showed that the error of each channel system fluctuated from 1.03mV to 1.08mV at 75℃, and from 0.94mV to 1.06mV at 100℃,120℃,135℃sys-tematic absolute error decreased when the environmental temperature rose, generally speaking the error changes were in the 1±0.08mV, If we got rid of the deviation of 1mV, the measurement accuracy of test system was±2℃.The highest temperature of bathtub combustion chamber appeared on the piston top, the average temperature was 264℃, the maximum instantaneous temperature is 272℃. The center temperature of the combustion chamber bottom was slightly higher than at the bottom corner, because piston skirt was cooled by lubricating oil injected. The lowest temperature was 188℃in first ring groove, the highest temperature is 224℃,and it is coking temperature of the ordinary lubricating oil, the special lubricating oil should be used in the CNG engine. With maximum throttle opening, the temperature of the piston reduced when the working condition transform from high speed to low speed transition condition, and after the working condition was stable, the temperature slightly rose. When engine speed transform from low speed, the piston temperature increased, and after reach-ing a stable condition, the piston temperature reduced. With exhaust temperature the en-gine rising, piston temperature rose; lubricating oil injected changed temperature distribu-tion of piston, but when oil temperature rose 8℃on steady working condition, there was no significant temperature change on each measuring point.There was a large error in the result that was simulated by using temperature boun-dary conditions calculated by the empirical formula, and the calculation of piston temper-ature field shall be modified by actual test temperature. The modified temperature field could achieve a high precision and the error of measured calculated data at the measured point was within 5℃, Temperature field results indicated that the overall temperature of the bathtub-shaped piston was relatively when engine speed was low, and the change of piston temperature is smooth. The engine running at high speed, the surface temperature of piston rose rapidly, and there was larger temperature gradient from the first ring groove to the top surface of the piston.