Experimental study on dynamic response characteristics of ejector driven by periodic pulse excitation using fast Fourier transform method

Ejectors play a critical role in thermal energy systems, yet their transient behaviors under fluctuating conditions remain insufficiently characterized. This study systematically investigates the dynamic response characteristics of structurally diverse ejectors through experimental methods. A dedicated test rig incorporating a PWM-controlled solenoid valve was developed to generate precise pressure excitations. The dynamic response characteristics of ejectors with different excitation frequencies and amplitudes acting on ejectors with different structures (Lm = 26.3/34.6/43.9 mm) are analyzed. The experimental results show that the response time of the outlet and secondary flow pressure is independent of the frequency of the primary pressure disturbance, and the amplitude of the disturbance changes linearly with the primary pressure DP. Under different mixing section lengths, when pressure excitation is applied to the primary flow, the response time of ejector pressure does not change with the length of mixing section, and the response time of outlet pressure increases with the growth of mixing section. These findings establish quantitative relationships between ejector geometry and transient response parameters, providing actionable insights for (1) predicting ejector stability margins in dynamic operating conditions and (2) optimizing control strategies for thermal systems with inherent pressure fluctuations.