Technical Papers
Diagnostic Method for 2-Stroke Cycle Diesel Engine* by Measurement of Vibration on Cylinder-Jacket
─ Observation of Change in Normal Vibration Pattern ─
Ryuichi Kimura**, Wataru Terashima**, Noboru Nakai**, Tetsuo Yamada***, Shou Takeda****
It is necessary to arrange the system to monitor the operational condition by various methods to achieve the safe operation of the engine. Based on the idea that the information on the engine condition can be obtained from its vibration signal, this paper carries out the experiment of the diesel engine of the actual ship. The vibration was measured for a long time (7800 hours) by means of a vibration sensor on the cylinder jacket. The hand touch can not recognize the time change of the vibration, but the three-dimensional expression of the vibration data through the frequency analysis allows the good understanding of the change of the vibration. The vibration is always changing if the vibration is observed on the long running hours of engine basis even in the stationary operation (engine revolution: 103rpm) of the diesel engine. We executed the statistical analysis as one method to estimate the condition of engine by the information from the vibration.
All the data of vibration was recorded on a normal engine condition, as a result we could not examine on an abnormal engine condition. Thus, the vibration data of low engine revolution (30rpm) was used as the data of abnormal condition in this analysis. As the result of the analysis, it is found that the abnormal can be recognized from the above-mentioned engine condition. We succeeded to make the statistical model which can diagnose an engine condition.
1. Introduction
The reliability of the main engine must be extremely high in order to ensure the safe navigation of ships. It is thus necessary to locate the phenomena of inconveniences and troubles even when they are small and insignificant, and to pinpoint the causes and take countermeasures therefore. We have known empirically that the abnormal vibration and the abnormal sound generated in a main engine are the symptom of possible failures or accidents. It is understood from these fact-findings that much information to indicate the state of the engine is contained in the radiant noise and the vibration of the engine. From such a viewpoint, the paper has aimed at the construction1),2) of the monitoring system capable of grasping the condition of the engine by positively using these information.
In any equipment including marine diesel engines, deterioration and abrasion are surely generated in each part. The phenomena gradually increased in the elapse of the running time, and eventually, leading to failures or accidents. In order to prevent these failures or accidents beforehand, it is necessary to grasp the information related thereto from various angles.
In this experiment, the vibration of the side wall part of the low-speed diesel engine was recorded for a long time, and the condition that the vibration is changed as the running time was examined. Firstly, the recorded vibration was frequency-analyzed to store the data on the vibration to construct the diagnosis system. The analysis method of the running condition introduced here includes the visual judgment, which grasps the motion of the engine based on the information by indicating the data of the radiant noise in a three-dimensional manner. The statistical analysis is then achieved in an objective manner based on the data information, in addition to the visual judgment, the results were evaluated and examined, and the diagnostic system capable of coping with the phenomenon to be changed with the time, was also considered.
* Translated from Journal of MESJ Vol.33, No.10
(Manuscript received Dec. 15, 1997)
** Kobe University of Mercantile Marine (Kobe City)
*** Kobe Nippon Kisen Kaisha, Ltd. (Kobe City)
**** Kawasaki Kisen Kaisha, Ltd. (Minato-ku Tokyo)
