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Indirect measurement of cylinder pressure from diesel engines using acoustic emission

机译：使用声发射间接测量柴油发动机的气缸压力

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Indirect measurement of the cylinder pressure from diesel engines is possible using acoustic emission (AE). A method is demonstrated for a large two-stroke marine diesel engine and a small four-stroke diesel engine, which involves reconstructing the cylinder crank angle domain diagram from the AE generated during the combustion phase. Raw AE was used for modelling and reconstructing the pressure waveform in the time domain but this could not be used to model the pressure rise (compression). To overcome this problem the signal was divided into two sections representing the compression part of the signal and the fuel injection/expansion stroke. The compression part of the pressure signal was reconstructed by using polynomial fitting. An auto-regressive technique was used during the injection/expansion stroke. The rms AE signal is well correlated with the pressure signal in the time and frequency domain and complex cepstrum analysis was used to model the pressure signal for the complete combustion phase (compression, injection and expansion). The main advantage of using cepstral analysis is that the model uses the frequency content of the rms AE signal rather than the energy content of the rms AE signal, which gives an advantage when the signal has lower energy content, during the compression process. By calculating the engine running speed from the rms AE signal and selecting the proper cepstrum model correlated to the combustion rms AE energy content, an analytical algorithm was developed to give a wide range of applicability over the .different conditions of engine speed, engine type and load. The pressure reconstructed from both AE and acceleration data are compared. AE has the advantage of a much higher signal-to-noise ratio and improved time resolution and is shown to be better than the acceleration.
机译：可以使用声发射（AE）间接测量柴油机的气缸压力。演示了一种用于大型二冲程船用柴油机和小型四冲程柴油机的方法，该方法包括根据燃烧阶段产生的AE重建气缸曲柄角域图。原始AE用于在时域中建模和重建压力波形，但不能用于建模压力上升（压缩）。为了克服这个问题，信号被分成代表信号压缩部分和燃料喷射/膨胀冲程的两个部分。通过多项式拟合重建压力信号的压缩部分。在注射/膨胀冲程期间使用了自动回归技术。均方根AE信号在时域和频域中与压力信号具有很好的相关性，并且使用复杂的倒谱分析对整个燃烧阶段（压缩，喷射和膨胀）的压力信号进行建模。使用倒频谱分析的主要优势在于，该模型在压缩过程中使用均方根AE信号的频率含量而不是均方根AE信号的能量含量，这在信号具有较低能量含量时具有优势。通过根据有效值AE信号计算发动机运行速度并选择与燃烧有效值AE能量含量相关的合适的倒谱模型，开发了一种解析算法，可在不同的发动机转速，发动机类型和转速条件下提供广泛的适用性加载。比较从AE和加速度数据重建的压力。 AE具有更高的信噪比和改进的时间分辨率的优势，并且被证明比加速度要好。

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