﻿ 内燃机工况对气缸敲击振动的影响探究
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 北京化工大学学报(自然科学版)  2018, Vol. 45 Issue (1): 60-64  DOI: 10.13543/j.bhxbzr.2018.01.010 0

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REN ZhongRui, SONG LiZhe, JIANG ZhiNong. Piston-slap vibration in internal combustion engines under working conditions[J]. Journal of Beijing University of Chemical Technology (Natural Science), 2018, 45(1): 60-64. DOI: 10.13543/j.bhxbzr.2018.01.010.

文章历史

Piston-slap vibration in internal combustion engines under working conditions
REN ZhongRui , SONG LiZhe , JIANG ZhiNong
Diagnosis and Self-Recovery Engineering Research Center, College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, Beijing 100029, China
Abstract: The nonlinearity of piston-slap vibration peak-to-peak values as a function of engine speed as well as their linearity as a function of load have been verified using mathematical modeling and simulations. Engine speed, load and power torque were included in the balanced equation for internal combustion engine torque, in which piston radial acceleration refers to the geometrical relationship between power torque and piston side thrust. The severity of vibrations was formulated using the peak-to-peak values of the impulse signal of the radial acceleration around the fire phase. An integrated mathematical model confirmed both the nonlinearity between speed and vibration, and the linearity between load and vibration, and these results were verified using simulations with AVL-EXCITE. Given the dependence of piston-slap vibration on engine speed and load, an on-line monitoring system and on-site staff are able to diagnose piston-slap faults more accurately, allowing a piston-slap alarm to be implemented.
Key words: internal-combustion engine    speed    load    piston-slap vibration

1 敲缸振动的数学模型建立

 图 1 敲缸状态曲柄连杆机构动力学分析 Fig.1 Link-crank mechanism dynamics analysis for the piston-slap condition

 $\begin{array}{l} \;\;\;\;{F_{\rm{t}}} = {F_{\rm{l}}}{\rm{sin}}\left( {\theta + \varphi } \right) = \frac{{{F_{\rm{p}}}{\rm{sin}}\left( {\theta + \varphi } \right)}}{{{\rm{sin}}\varphi }} = {F_{\rm{p}}}\\ \left( {\frac{{{\rm{sin}}\;\theta \cos \;\varphi }}{{{\rm{sin}}\;\varphi }} + {\rm{cos}}\;\theta } \right) \end{array}$ (1)

Lsin φ=Rsin θ

 $\left\{ \begin{array}{l} {\rm{sin}}\;\varphi = \lambda {\rm{sin}}\;\theta \\ {\rm{cos}}\;\varphi = \sqrt {1 - {\lambda ^2}{\rm{si}}{{\rm{n}}^2}\theta } \end{array} \right.$ (2)

 $\begin{array}{l} \;\;\;{F_{\rm{t}}} = {F_{\rm{p}}}\left( {\sqrt {\frac{1}{{{\lambda ^2}}} - {\rm{si}}{{\rm{n}}^2}\theta } + {\rm{cos}}\;\theta } \right) = {m_{\rm{p}}}\ddot y\\ \left( {\sqrt {\frac{1}{{{\lambda ^2}}} - {\rm{si}}{{\rm{n}}^2}\theta } + {\rm{cos}}\;\theta } \right) \end{array}$ (3)

 $I\frac{{{{\rm{d}}^2}\theta }}{{{\rm{d}}{\mathit{t}^2}}} = {T_{\rm{p}}} - {T_{\rm{l}}}$ (4)

 ${T_{\rm{p}}} = {F_{\rm{t}}}R$ (5)

 $I\frac{{{{\rm{d}}^2}\theta }}{{{\rm{d}}{\mathit{t}^2}}} = I\frac{{{\rm{d}}\left( {\frac{{{\rm{d}}\theta }}{{{\rm{d}}\mathit{t}}}} \right)}}{{{\rm{d}}\theta }}\frac{{{\rm{d}}\theta }}{{{\rm{d}}\mathit{t}}} = I\frac{{{\rm{d}}\omega }}{{{\rm{d}}\theta }}\omega$ (6)

 $\ddot y = \frac{{I\frac{{{\rm{d}}\omega }}{{{\rm{d}}\theta }}\omega + {T_1}}}{{{\mathit{m}_{\rm{p}}}R\left( {\sqrt {\frac{1}{{{\lambda ^2}}} - {\rm{si}}{{\rm{n}}^2}\theta } + {\rm{cos}}\;\theta } \right)}} = {c_1}\frac{{{\rm{d}}\omega }}{{{\rm{d}}\theta }}n + {c_2}{T_{\rm{l}}}$ (7)

 $\left\{ \begin{array}{l} {c_1} = \mathop {\lim }\limits_{\theta \to 2\mathit{n}\pi } \frac{{\pi I}}{{30{m_{\rm{p}}}R\left( {\sqrt {\frac{1}{{{\lambda ^2}}} - {{\sin }^2}\theta } + \cos \theta } \right)}} = \\ \;\;\;\;\;\;\;\;\;\frac{{\pi \lambda I}}{{30\left( {1 + \lambda } \right){m_{\rm{p}}}R}}\\ {c_2} = \mathop {\lim }\limits_{\theta \to 2\mathit{n}\pi } \frac{1}{{{m_{\rm{p}}}R\left( {\sqrt {\frac{1}{{{\lambda ^2}}} - {{\sin }^2}\theta } + \cos \theta } \right)}} = \\ \;\;\;\;\;\;\;\;\frac{\lambda }{{\left( {1 + \lambda } \right){m_{\rm{p}}}R}} \end{array} \right.$ (8)

 ${{\ddot y}_{\rm{p}}} = \frac{\lambda }{{\left( {1 + \lambda } \right){\mathit{m}_{\rm{p}}}R}}\left( {\frac{{\pi I{\rm{d}}\omega }}{{{\rm{30d}}\theta }}n + {T_1}} \right)$ (9)

2 仿真验证及结果分析

2.1 内燃机转速与敲缸振动的非线性验证

 图 2 变转速工况下敲缸振动冲击信号示意图 Fig.2 Schematic diagrams of piston-slap vibratory impulses for different crankshaft speeds

 图 3 变转速工况下振动峰峰值曲线图 Fig.3 Plot of vibration peak-to-peak values for different crankshaft speeds
2.2 发动机负载与敲缸振动的线性验证

 图 4 变负载工况下敲缸振动冲击信号示意图 Fig.4 Schematic diagram of piston-slap vibratory impulses for different loads
 图 5 变负载工况下振动峰峰值曲线图 Fig.5 Plot of vibration peak-to-peak values for different loads
3 结论

(1) 敲缸振动峰峰值随着内燃机转速增大而增大，且呈非线性关系；内燃机负载增大时，敲缸振动峰峰值随之增大，且具有很强的线性关系。

(2) 根据敲缸振动响应对内燃机转速和负载的敏感性，在线监测系统可以在气缸敲击现象发生时分别将内燃机转速、负载与敲缸振动峰峰值作拟合处理，根据处理结果的线性拟合程度来鉴定敲缸故障，辅助现场工作人员实现敲缸预警。

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