Ion Current Based Pressure Modeling And Control For Pulse Detonation Engine

Pulse detonation engine(PDE) is researched worldwide as a new propulsion system in theaeronautics and astronautics field. The conventional pressure sensor could only work several minutesfor the high-temperature, high-pressure and high-impulse circumstance in the PDE. Furthermore, iteffects the PDE state monitoring and pressure based control. Focusing on the high-temperaturepressure measurement of the PDE, the pressure modeling based on the ion current and the PDEoperation process control are developed. The major work is as follows:After analyzing one-dimension ZND structure of the pulse detonaton wave and the ionizationmechanism of the hydrocarbon flame, it is concluded that the main part of ionization in the detonationwave is chemical ionization. Based on the chemical ionization, the mechanism of the ion currentforming is analyzed and the mathematic model of the ion current is established. The measurementcircuit for the ion current is also proposed. Based on the ionization and the ion current model, therelationship between detonation wave pressure and the ion current is proposed. It is the foundation forthe detonation wave pressure modeling.In order to measure ion current in the detonation wave, the single-pole probe and the double-poleprobe are designed. The candidate material of the pole is compared with the chemical, physical andelectronic characteristics. The two single-cycle detonation experiment systems and the multi-cycledetonation experiment system are established to determine the selection of optimal probes. Thecompared experiments between the different probe structures, pole materials, pole lengths and the biasvoltages are developed. The multi-cycle detonation experiment is developed for the propagation speedmeasurement of the detonation wave. It is concluded that the single-pole short probe with the polematerial of Y, NiCrFe and Cu is suitable for the ion current measurement and the optimal bias voltage10V.The principle and variation of pressure in the PDE are analyzed based on the ZND detonationwave structure. The numerical model of the detonation wave pressure is founded. According to thelinear relationship between the ion current and the detonation wave pressure, the peak pressure modelbased on the decay of the ion current for the detonation wave is founded by least-squares method. Thepeak pressure model is validated by the experiment data. It shows that the model accuracy within3.5%. Because of the similarity between the pressure sensor signals and the ion current signals, theRBF neural network is employed to map the ion current to the detonation wave pressure. Afterdiscussing the training data selection, network structure and the effects of the network parameters, the non-linear model of the detonation wave based on the neural network are founded. The results of themodel validation show that the non-linear model has high accuracy and rapid response and thenetwork has satisfactory generalization.By analyzing the effect of the Taylor expansion wave, the uniform region after Taylor wave andthe center expansion wave to the pressure in the PDE, the simplified pressure models of the Taylorwave and the center expansion wave are founded according to the one-dimension unsteady flowtheory. The pressure in uniform region after the Taylor wave is modeled according the relationshipbetween the Taylor wave pressure and the uniform region pressure. Following the pressure continuityin the PDE, the pressure hybrid-model is constructed by combining the detonation wave pressurenon-linear model, the Taylor wave simplified pressure model, the uniform region pressure model andthe center expansion simplified pressure model. The pressure hybrid-model is validated by thepressure sensor measurements. The results show that the pressure hybrid-model has the satisfactoryaccuracy and could provide the reliable pressure signal for the PDE operation process control.Aiming at the PDE control, the average thrust model of the PDE is established. The PDE controlschemes based on the aerovalve are reviewed and the characters of the schemes are analyzed. Usingthe output of the pressure hybrid-model, the pressure signal, the PDE operation process controlscheme based on the pressure signal in the PDE are proposed and its performance is studied by thesimulation. The results show that the PDE could operate in the different frequency using the controlscheme base on the PDE pressure signal. The operation frequency is adjusted easily and the PDEcould generate the effective thrust.