Technical Papers
Fundamental Study on Total Electronic Control System for Marine Engines*
Masayoshi Nakashima*****, Tatsuo Takaishi** Keijiro Tayama***, Koji Takasaki**** Yoshinori Nagae**, Hiroyuki Ishida**
This paper describes the application of an engine total electronic control system for marine engines. This system makes it possible to control engine performance according to the operation conditions. First, concept and structure of such a system are discussed as a feasibility study. Second, results of tests to confirm the functions of electronically controlled fuel injection system and exhaust valve system are introduced.
1. Introduction
In conventional large marine diesel engines, the development focusing on the reduction of the fuel consumption has been promoted in order to improve the efficient use of the energy and the economy. As a result, the highly efficient operation has been realized in the rated operational condition. However, in the future marine diesel engines, it is requested to maintain the high efficiency in any running and operational conditions, and at the same time to ensure the reliability of the components of the engines. In addition, reduction of harmful exhaust emissions is also requested from the aspect of the global environmental pollution prevention.
The object of this study is to construct the engine total electronic control system which efficiently links various electronically controlled functions in order to satisfy the high efficiency and low pollution. Especially as the most important point in this system is the sophistication of the combustion control function, the electronically controlled hydraulic-driven type fuel injection sys-tem and the exhaust valve system are newly developed.
2. Examination of total electronic control system
2.1 Research and examination of control technology in various operational conditions
Table 1 is the summary of the requests and necessary functions under various operational conditions (starting, astern, entering/leaving the ports, under heavy weather, when low-grade fuel is used, etc.) and control means to realize them. Fig. 1 shows the outline of the sophisticated engine total electronic control system aiming at the future marine prime mover. In this system higher performance for the fuel injection system and the exhaust valve system is necessary.
The operations of the fuel injection system and the exhaust valve system of a conventional engine are achieved at the fixed timing depending on the setting of the cam shaft. In addition, as the cam speed is determined by the engine speed, sufficient performance is not always demonstrated in other conditions even when the optimization is realized at the rated point. On the other hand, if the electronically controlled hydraulic drive system, which is independent from the operation of the cam shaft is used, it will be possible to realize the optimum operation for various operational conditions.
One more important idea from the safety side is that even if one function is failed, the failure must not affect the whole system or stop the engine. And for the fuel injection system and the exhaust valve system, it is necessary to independently control each cylinder.
2.2 Construction of total electronic control system
Fig. 2 shows the global construction of the total electronic control system. The engine system is operated under the command signal from the bridge. In the engine control room, the signal is transmitted to the engine controller.
As shown in the figure, it becomes possible to sufficiently demonstrate the performance of the engine under various operational conditions by electronically controlling the fuel injection system, the exhaust valve system, the starting system, the cylinder lubrication system, the VG (Variable Geometry) turbocharger, the scavenging air swirl and the cooling system. The fuel injection system and the exhaust valve system are further described here. The control of the fuel injection system and the exhaust valve system by the total electronic control system is based on the standard data of fuel injection timing and the exhaust valve opening/closing timing on the propeller characteristic line.
* Translated from Journal of MESJ Vol. 34, No. 7 (Manuscript received on December 28, 1998)
** Mitsubishi Heavy Industries Co., Ltd. (Fukahori-machi, Nagasaki City)
*** MHI (Marunouchi, Chiyoda-ku, Tokyo)
**** Kyushu University (Kasuga-koen, Kasuga City)
***** Kyushu University (MHI till Sept, 1999)
