摘要 |
PURPOSE:To reduce the resistance of a propeller to reduce the load of the turbine and reduce the load of the turbine at a critical rotational speed to shorten the turbine driving time at the critical rotational speed by blowing compressed air toward the propeller from the stern part when the rotational speed of the turbine approaches the critical rotational speed. CONSTITUTION:In a case where the rotational speed of the turbine is gradually increased upon the increase of the vessel speed, the rotational speed is measured. When the measured value approximates the critical rotational number, compressed air is blown off from a compressed air blow-off pipe 1 through a control valve 2 which is adjustable in its flow quantity. Then, compressed air is discharged in the from of air bubbles toward the propeller 3 at the stern part. Accordingly the resistance of the propeller 3 reduces, and the load of the turbine reduces to abruptly increase the rotational speed. Hence, it is possilbe to pass through a critical rotational speed region within a short period of time. Thereafter, the supply of the compressed air is stopped, and the turbine is operated at a predetermined rotational speed. |