瞄准距离对热喷涂粒子脉冲信号半高宽的影响和校正

针对自行研发的基于窗口调制和比色测温技术的热喷涂粒子参数测量系统，从理论上分析了瞄准距离变化对脉冲信号半高宽的影响，提出了光学杠杆关系和信号特征变化两种共同起作用的影响机制，并指出两种机制在小于理想瞄准距离时对半高宽的影响相反，而在大于理想瞄准距离时的影响则因相同而叠加，使得脉冲信号半高宽随瞄准距离的变化呈现不对称U形变化规律．实测脉冲平均半高宽的变化趋势与上述规律吻合良好，根据文中提出的校正系数修正后，在非标准瞄准距离下测得的粒子平均速度的误差明显下降．

Effect of Aiming Distance on Full Width at Half Maximum(FWHM) of Signal Pulses Generated by Thermal Spray Particles and Corresponding Calibration

The effect of aiming distance on full width at half maximum(FWHM) of signal pulses was theoretically analyzed for a novel measurement system based on window-modulating velocimetry and 2-color pyrometry to diagnose multiple parameters of thermal spray particles.It reveals that the optical leverage relationship and the variance of signal characteristics serve as two main factors affecting the average FWHM of the measured signal pulses.The two factors exert a superimposed effect on the average FWHM when the aiming distance is larger than standard 75 mm,or a neutralized effect when the aiming distance is smaller than 75 mm.Consequently,when the aiming distance varies from 45 mm to 120 mm,the average FWHM appears an asymmetrical U-shaped variation to well coincide with the experimental results.Calibrating with the presented coefficients,the error level of the measured velocity of in-flight particles at non-standard aiming distance lowers significantly.