关键词: 叶端间隙, 微波测量, RD-S校正, 整剖面间隙, 相位差, 频谱校正

Abstract:

The non-contact， high-precision measurement of complex blade tip profile clearance is critical for ensuring the safe and efficient operation of aero-engines. In a 120 GHz microwave sensor-based static and dynamic measurement system， the static echo signal is affected by amplitude modulation interference， while the tip information reflected by the dynamic echo signal from complex-shaped blades is susceptible to abrupt boundary phase changes. These challenges significantly hinder accurate static and dynamic measurements of blade tip profile clearance. To address these issues， this paper first introduces the Ratio Differentiation-Spectrum （RD-S） correction method to estimate imbalance parameters under amplitude modulation. This method leverages the attenuation consistency of I/Q signals to eliminate amplitude modulation interference in static echo signals via ratio differentiation， and subsequently estimates imbalance parameters using the main and mirror frequency components. Secondly， by employing the Deimoffer theorem and integrating amplitude-phase information， the method mitigates boundary phase mutation effects and enables the measurement of tip profile clearance across any half-wavelength. The experimental results demonstrate that the proposed RD-S correction method in static measurements reduces the demodulation displacement error by an average of 79.2% in comparison with the conventional correction method， achieving an average displacement error of 1.31 μm and a nonlinearity of less than 0.06%. In dynamic measurements， the method achieves an average blade tip clearance error of less than 2.5 μm within a relative tip variation range of 300 μm. Additionally， the average measurement error for the concave depth of H-shaped blades is 2.09 μm.

Key words: blade tip clearance, microwave measurements, RD-S correction, blade tip profile clearance, phase difference, spectral correction