General Information (Cooling System)
本发动机具有压力式冷却系统。 压力式冷却系统有两个优点。
- 压力有助于防止气穴。
- 沸腾的风险降低。
当机械力引起冷却液中形成气泡时,发生气穴。 气泡可能在气缸套上形成。 破裂的气泡可能把气缸套上的氧化膜中除去。 这样会发生腐蚀或点蚀。 如果冷却系统压力过低,气泡的浓度增加。 在压力型冷却系统中气泡浓度降低。
沸点受三种因素影响:压力, 海拔 和 冷却液中的乙二醇浓度。 液体沸点随着压力增加而增加。 液体沸点随着海拔高度增加而降低。 图 1 显示压力和海拔对水的沸点的影响。
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图 1 | g00286266 |
冷却液沸点也取决于冷却液的类型和乙二醇的浓度。 乙二醇浓度越大,沸点越高。 但是,乙二醇传热效果不及水。 因为沸点和传热的效率,乙二醇的浓度很重要。
与冷却系统相关的有三个基本故障:
- 过热
- 冷却液损失
- 过冷
如果冷却系统没有正确保养,如结垢和沉淀物等固体会降低冷却系统的传热的能力。 发动机工作温度会升高。
当发动机超载时,发动机将在拖动状态下运转。 当发动机在拖动状态下运转,也即发动机在较低的转速下运转,这样降低了冷却液液流。 在高负载下减少冷却液液流将引起过热。
泄漏使冷却液缺失。 过热的冷却液可通过冷却系统压力安全阀溢出。 较低的冷却液液位也会产生过热。 过热导致象缸盖裂纹和活塞粘缸现象发生。
缸盖或气缸套裂纹将迫使废气进入冷却系统。 额外的压力引起冷却液丢失、水泵气穴、冷却液循环量少和进一步的过热。
冷却液旁通电动水温调节器并直接流入散热器时会造成过冷。 在低环境温度下低负载工作可能引起过冷。 当水温调节器保持开启时会造成过冷。 过冷降低工作效率。 过冷使发动机机油快速污染。 这样导致曲轴箱形成油泥,气门积炭。
加热和冷却循环过快可能导致气缸盖裂纹、密封垫故障、加速磨损和燃油消耗过量。
如果怀疑冷却系统有故障,在对系统进行任何测试前,进行目视检查。
Caterpillar Information System:
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