Research On Dynamic Response Rule Of Thermocouple For One Type Of Turboprop Engines Combustor

In the study of turboprop engine control system, it is very important to get combustor outlettemperature parameters quickly and accurately. Because the measurement of temperature bythermocouples is usually going behind the real time, it is necessary to study the dynamic responserules of thermocouple. In this paper, take two particular kinds of thermocouple, which is for a certaintype of turboprop engine combustor outlet temperature measurement, as the research object, studyingtheir response characteristics.Firstly, taking the tube type resistance furnace to provide stable temperature field, then take thecompared method for thermocouple calibration. The feasibility of this method has been verified bycomparing the reference temperature-voltage relationship. Fitting the test results, we get thevoltage-temperature relationship, which is quite convenient for thermocouple practical use.Secondly, measure the thermocouple static response characteristics or time constant. The resultshow (1) In the same step temperature ΔT, the higher initial temperature T0, the smaller time constant.(2) In the same initial temperature T0, we need to take both heat conduction rate and heat demand intoconsideration in case judging thermocouple time constant.(3) As the geometric parameters ofthermocouple junction are in consistent with heat transfer conditions, the time constant mainlydepends on thermocouple itself physical properties(, c): The density getting down and thehigher specific heat c make the time constant bigger. Or conversely, the density getting upand the lower specific heat c make the time constant smaller.Using FLUENT to simulate thermocouple influence on the flow field, simulations indicate:(1)For fixed installation form of thermocouple, in different flow velocity, thermocouple influence on theflow field is consistent with the trend.(2) For fixed fabricated thermocouple, installation angle islarger, the influence of flow field is smaller, but the lower speed of flow field around is to thedetriment of convection heat transfer.(3) On the whole, due to the great differences in size, no matterwhat type of installation, thermocouple is always having a weak effect on the flow field.(4)Combined with numerical simulation results and the practical application, the vertical installation is todetermine as the optimal installation form.According to the numerical simulation of the thermocouple structure and material on theinfluence of the response characteristics, we found that:(1) Comparing the three forms of protectioncasing structure such as half opening, through-hole and constrictor on thermocouple junction, to determine the contraction mouth form, which makes the thermocouple response quickly to thetemperature.(2) Establish thermocouple heat transfer model, which can provide guidance foroptimization of thermocouple structure and material selection.Simulation of hot wind tunnel test is to study the dynamic response characteristics of thethermocouple:(1) In the same step temperature ΔT and initial temperature T0, the airflow velocity ishigher, the response of the thermocouple is faster.(2) Base the fine thermocouple responsecharacteristics, take dynamic compensation experiment to get the dynamic response of thethermocouple.