Fig. 11 Measured date in exhaust valve system test
Fig. 12 Exhaust valve opening speed
The optimum timing is in the vicinity of 118° at the 100% load, 123° at the 75% load, and 128° at the 50% load. It is estimated that the fuel consumption can be improved by delaying the opening timing of the exhaust valve as the load is reduced, with the reduction of approximately 1g/PS･h at 75% load, and 3g/PS･h at 50% load.
(2) Effect of exhaust valve closing timing The fuel consumption at each load is examined by changing the closing timing of the exhaust valve. The fuel consumption is improved by approximately 1g/PS･h by making an advancement of approximately 10° at 50% load.
(3) Effect of injection timing
The fuel consumption and Pmax with each load are examined by changing the injection timing. Though the fuel consumption is improved by advancing the timing, it is necessary to set the timing to an appropriate value taking into consideration the rise in Pmax and the increase in NOx.
4. Conclusion
In order to satisfy the excellent economy, the high reliability and the lower pollution to be requested for the future marine diesel engines, the further sophisticated engine total electronic control system was constructed. Each control system was examined to optimize the running conditions of the engine under various operational conditions, and the electronically controlled hydraulic drive type fuel injection system and the exhaust valve system which were most important in this system were developed, and the following results were obtained.
(1) By using the pressure of 35 MPa for the hydraulic source,
(1-1) Fuel injection system
* The injection pressure of approximately 120 MPa, the injection duration of approximately 18 deg. were obtained, achieving the targeted high performance.
* The injection mode close to the rectangular shape was obtained.
* It was confirmed that the injection quantity could be controlled according to the indicated value by the controller, and was stable also at the partial load.
(1-2) Exhaust valve system
* The targeted rapid valve opening was realized. achieving the speed of 3 m/s.
* The targeted deceleration at closing for seating was also achieved.
(2) The effect of the opening timing. the closing timing and the injection timing of the exhaust valve on the engine performance were checked by the combustion test with the single-cylinder test engine.
This study was subsided by the Technological Development Fund of Ship & Ocean Foundation under the support of the Nippon Foundation from the non-profit fund through the Motor Boat Racing, and the authors wish to express their gratitude.
Reference :
Nagao F., Nainenkikai-Kohgi, the first volume (in japanese), 33th. ed., (1996), pp261-264, & Co. Yokendo
