Experimental study on the influence of structural parameters of semi-infinite dynamic pressure probe tubing on its dynamic characteristics

To improve the accuracy of dynamic pressure measurement in gas turbine combustors, this study investigates the influence of structural parameters of pressure tubing on its dynamic response characteristics, with emphasis on nonlinear behaviors under large-amplitude excitation. Based on the theory of acoustic wave propagation in pipelines, experiments were conducted using a modulated dynamic pressure generator to test pressure tubes with various lengths(20-200 mm) and diameters(2-6 mm). Results show that tube length dominates the phase lag, with phase difference proportional to the product of length and frequency. Reflection from the mounting seat is identified as the key factor causing resonance peaks in amplitude-frequency characteristics. The effect of diameter is governed by impedance matching: when the main tube diameter matches the fixed upstream and downstream sections, the system behaves as a transmission line with continuous impedance; when mismatched, the system becomes a resonator—small diameter(high impedance) excites high-frequency resonance, while large diameter(low impedance) excites low-frequency resonance. Under large-amplitude excitation, nonlinear effects further amplify the resonance peak of the small-diameter tube, resulting in gain exceeding unity—an abnormal amplification that deviates from classical linear acoustic theory. This study reveals the frequency-domain competition between linear dissipation and nonlinear resonance in the dynamic response of pressure tubes under large-amplitude conditions, providing guidance for the design and signal correction of high-precision dynamic pressure measurement systems.