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本文视通道为一线性弹性系统,使用频率响应法,给出了对其自振频率及示功图上出现的腔振,相移和图形失真误差的理论和实验分析。要得到不失真的示功图,应使整个测量系统的频率特性在50倍被测压力基频范围内平坦。因此,应尽量提高测压通道的自振频率,这可以用加大通道直径、缩短通道长度来达到。通道的自振频率可由(8)式计算。燃烧发火时,在测压通道入口处发生压力对时间一次导数的跳跃,从而激起腔振(式(29))。腔振可通过增加通道阻尼或加接滤波网络来消除。后一法更为有效,因为此时仍可使用高自振频率的通道。示功图的相移可用热力修正法修正。
In this paper, we consider the channel as a linear elastic system, and use the frequency response method to give theoretical and experimental analysis on its natural frequency and the error of cavity distortion, phase shift and distortion on the dynamometer. To obtain a distortion-free diagram, the frequency characteristics of the entire measurement system should be flat within 50 times the fundamental frequency of the measured pressure. Therefore, we should try to improve the natural frequency of pressure measurement channel, which can increase the channel diameter, shorten the length of the channel to achieve. The natural frequency of the channel can be calculated by (8). When the fire burns, a jump in the pressure derivative of time at the inlet of the pressure measurement channel occurs, causing the cavity vibration (Equation (29)). Cavity vibration can be eliminated by adding channel damping or adding filter networks. The latter method is more efficient, because of the high natural frequency of the channel can still be used at this time. The phase diagram of the dynamometer can be corrected by thermodynamic correction.