Knock intensity identification of piston aviation kerosene engine based on dual-domain feature analysis
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摘要:
为了提升对活塞式航空煤油发动机中爆震强度的识别准确性,搭建了专用试验台架并开展燃烧试验,采集了多种工况下的缸内压力信号,从中提取爆震信息。采用小波包变换对缸压信号进行分解,并通过能量熵分析提取了表征爆震等级的子频带分量,发现爆震特征频带集中在7.5~18.75 kHz。基于此频带重构爆震信息,从时域和频域中提取了22个爆震特征指标,形成双域爆震特征图像。为精准识别爆震强度,分别构建了多层感知机(MLP)和卷积神经网络(CNN)模型,以双域爆震特征指标和图像作为输入参数,并在4组工况下进行验证。结果表明:两种模型均具有较高的识别精度,其中CNN模型的平均识别精度达93.46%,较MLP模型的88.50%高出4.96%,验证了CNN模型在爆震强度识别中的准确性与合理性。
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关键词:
- 活塞式航空煤油发动机 /
- 爆震强度识别 /
- 小波包理论 /
- 双域特征分析 /
- 卷积神经网络
Abstract:To improve the accuracy of recognizing knock intensity in aviation kerosene piston engines, a dedicated test bench was built, combustion tests were conducted, and cylinder pressure signals under various operating conditions were collected to extract knock information. Wavelet packet transform was applied to decompose the pressure signals, and energy entropy analysis was used to identify sub-band components effectively characterizing knock levels. The knock feature sub-band for this engine was found to be concentrated within the 7.5—18.75 kHz range. Knock information within this band was reconstructed, and 22 knock feature indicators were extracted from the time and frequency domains, forming a bi-domain knock feature image. To accurately identify and analyze knock intensity, both a multilayer perceptron (MLP) model and a convolutional neural network (CNN) model were developed. These models used the dual-domain knock feature indicators and images as input parameters and were validated under four different operating conditions. The results demonstrated high recognition accuracy for both models, with the CNN model achieving an average accuracy of 93.46%, surpassing the MLP model’s 88.50% by 4.96%. This highlighted the CNN model’s superior accuracy and generalization capability for knock intensity recognition in aviation kerosene engines.
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表 1 航空煤油发动机基本结构参数
Table 1. Basic structural parameters of aviation kerosene engine
参数 数值或说明 活塞行程/mm 83 气缸直径/mm 100 排量/mL 650 压缩比 9∶1 曲柄连杆长度/mm 142.56 气门最大升程/mm 9 气门数 4 火花塞数 2 活塞形状 偏心碗形状 燃料类型 航空煤油(RP-3) 喷油方式 压缩空气辅助直喷 表 2 发动机爆震试验工况基本参数
Table 2. Basic parameters of the engine knock test conditions
参数 数值或说明 转速/(r/min) 2500 ~6500 节气门开度/% 20~50 点火提前角/(°) 上止点前22~39 喷油时刻/(°) −60 喷油脉宽/ms 4~7 喷射策略 油气同步喷射 点火策略 双火花塞同步点火 过量空气系数 0.85 冷却水温/℃ 90 表 3 不同工况下爆震试验中各爆震等级数量
Table 3. Number of each knock level in the knock test under different operating conditions
参数 数值 工况1 工况2 工况3 工况4 工况5 转速/(r/min) 3500 点火角/(°) 27 30 33 36 39 采样频率/kHz 240 轻度爆震/个循环 15 31 79 101 112 中度爆震/个循环 5 12 33 46 54 严重爆震/个循环 3 9 25 32 38 总计/个循环 23 52 137 179 204 表 4 圆柱形燃烧室不同共振模态下的对照频率
Table 4. Control frequencies of cylindrical combustion chambers in different resonant modes
共振模态 (m,n) αm,n fm,n/kHz 1阶切向 (1,0) 1.84 5.86 2阶切向 (2,0) 3.05 9.72 3阶切向 (3,0) 4.20 13.30 4阶切向 (4,0) 5.33 16.90 5阶切向 (5,0) 6.42 20.40 1阶径向 (0,1) 3.83 12.20 表 5 不同发动机负荷工况下的爆震试验测试集样本
Table 5. Sample test set of knock tests under different engine loading conditions
组别 转速/(r/min) 点火角/(°) 节气门开度/% 循环数 爆震数 爆震率/% 1 2500 30 20 334 62 18.56 2 2500 33 20 363 105 28.93 3 4500 30 40 389 83 21.34 4 6500 32 50 366 113 30.87 表 6 不同模型爆震强度识别精度
Table 6. Knock intensity identification accuracy of different models
% 爆震等级 MLP CNN 非爆震 88.15 93.30 轻度爆震 88.21 92.92 中度爆震 91.18 94.12 严重爆震 91.84 97.96 平均识别精度 88.50 93.46 -
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