Авіаційно-космічна техніка та технологія (Aug 2019)
NON-STATIONARY TORSION OSCILLATIONS OF PROPULSIVE COMPLEX THAT ACCOUNT OF THE WAVE PHENOMENA IN A SHAFT LEAD AND OPERATION OF A DIESEL SPEED REGULATOR
Abstract
The ship propulsion complex is considered as a torsion system with distributed parameters, consisting of flywheels (cylinder compartments, propeller) connected by shafts. Shafts can be weightless (only rigidity) or have distributed parameters. Contemporary container ships have a shaft line 120 meters long with a power of 86 MW. Such shafting is reasonable to consider as a shaft with the distributed parameters and to take into account the forces arising at an emersion and an immersing of the propeller screw, accompanied by wave effects. Also, the influence of the regulator on the condition of the shaft is considered. It was concluded that about 70 forms should be used (two of them are used). A calculation scheme and a mathematical model are proposed that allow to perform the calculations of the torsion system as a system with distributed parameters. Exposure (exit from the water) of the propeller is accompanied by a decrease in torque on it to almost zero. This condition can last several seconds and is accompanied by a decrease in temperature of the gases entering the turbine of the turbo-charging unit (low fuel supply at almost the same rotation speed). The turbo charging unit at the same time reduces its rotation speed, which leads to a drop in the pressure of the purge air. Immersion of the propeller is accompanied by a sharp increase in torque on the propeller. The speed controller gives the maximum fuel taking into account restrictions. The diesel speed begins to decrease, and the purge air pressure rises. If about 70 forms (using two) are used in the calculations arising from non-stationary torsional vibrations, then you can get a wave running along the shaft shaft both from the propeller and from the diesel engine. These waves interact with each other and lead to a three-fold increase in torque in the propeller. A rational mode of operation of the speed controller is proposed, in which several outbreaks are skipped during the immersion of the propeller. For short shafts, the delay in the regulator may be sufficient. For long, you need to take additional measures. We can conclude that when calculating non-stationary oscillations, the use of about 70 forms (using two) and the organization of the delay of the speed controller with a sharp increase in the load on the propeller.
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