The measurement of shock wave velocity by heat flux probe

Shock wave velocity is one of the most important parameters in shock tube for de-termining the running states.It can be measured through shock pressure or optical method,of which the cost will be high in large systems.Ionization-probe is an effective means of determining the velocity of detonation or strong shock waves by using the conductivity behind the shock wave, but it may not meet the experimental requirements under the condition that the shock wave veloc-ity is so low that the air behind the shock wave cannot reach the ionization temperature.A ther-mocouple flux probe with high frequency response is used in our measurement system to over-come the aforementioned disadvantages.Based on traditional ionization-probe circuit,the ther-mocouple probe measurement circuit is redesigned.The shock wave signal is amplified and locked to trigger the pulse generating circuit to obtain the shock velocity signal.The key of the circuit design is that the secondary amp signal interference is particularly large after the thermal simula-tion network,due to the load through a capacitor,therefore,the magnification of the secondary amplification circuit cannot be too high,but the amplitude of heat flux signal is determined by the magnification,so the relationship between the two factors need to be balanced.Temperature and heat flux signals are used as trigger signals respectively.The delay times contrasted with piezoe-lectric sensors are inconsistent when the trigger signal is temperature.The first pulse delays 130 microseconds,and the second delays 80 microseconds,which is because the limit trigger voltages have error.When the trigger source is heat flux signal,the circuit can be triggered without delay to obtain more accurate shock wave velocity.The resutls show that only heat flux signal can meet the time requirements of shock velocity.This method overcomes the drawbacks of traditional i-onization probe,and can be widely applied to various shock tubes for shock wave velocity meas-urement.