轮机概论(第四章).ppt

轮机概论 [ * ] 5、各种航行条件下主机的工况 (1)船、机、桨的配合 力、力矩和功率的平衡：螺旋桨的推力克服船舶阻力，主机提供螺旋桨推力所需扭矩和功率。 船舶阻力 船舶阻力包括：水力阻力(摩擦阻力、形状阻力、兴波阻力)、风力阻力、惯性阻力。 R-船舶阻力；Ar-阻力系数；Vs-船速。 轮机概论 [ * ] 与螺旋桨配合工作时的主机工况点 工况点：主机发出功率等于螺旋桨吸收功率，柴油机速度特性曲线与螺旋桨特性曲线的交点。 1-柴油机标定负荷速度特性 2-柴油机部分负荷速度特性 cba-螺旋桨特性 3-柴油机超负荷速度特性 柴油机速度特性变化 螺旋浆特性变化 轮机概论 [ * ] 第四节 可调螺距螺旋桨 Section 3：Controllable Pitch Propeller 桨叶螺旋面与桨毂可作相对转动，通过转动桨叶来改变螺距。 一、工作原理(★★★) 轮机概论 [ * ] 三、调距浆的优缺点(★★) 1、优点 适应性强 调节H/D，即可调节转矩，从而可是转速保持不变 轮机概论 [ * ] 第三章 船舶推进装置 2、缺点 构造复杂，制造工艺高，造价高 可靠性不强 效率低 桨叶根部易产生空泡 3、调距浆的操纵 * STERN TUBE AND STERN TUBE ?BEARINGS The ?hole ?in ?the ?hull ?structure ?for ?accom- modating the propeller shaft to the outside of the hull is called the stern tube. The propeller shaft is ?supported ?in ?the ?stern ?tube ?by ?two ?bearings— one at the inner end and one at the outer end of the stern tube—called stern tube bearings. At the inner end of the stern tube there is a stuffing box containing ?the ?packing ?gland ?(figure ?4-4), ?which is generally referred to as the stern tube gland. The stern tube gland seals the area between the shaft and stern tube but allows the shaft to rotate. The stuffing box is flanged and bolted to the stern ??tube. ??Its ??casing ??is ??divided ??into ??two compartments—the forward space which is the stuffing box proper, and the after space, provided with ?a ?flushing ?connection, ?designed ?to ?maintain a positive flow of water through the stern tube for ??lubricating, ??cooling, ??and ??flushing. ??This flushing ?connection ?is ?supplied ?by ?the ?firemain. A DRAIN CONNECTION is provided both for testing for the presence of cooling water in the bearing ?and ?for ?permitting ?sea ?water ?to ?flow through the stern tube and cool the bearing when underway, where natural seawater circulation is employed. The ?gland ?for ?the ?stuffing ?box ?is ?divided longitudinally into two parts. The gland bolts are long enough to support the gland when the latter is withdrawn at least 1 inch clear of the stuffing