涡旋流体机械平衡重功率损耗的数值分析

Numerical analysis of power loss on counterweight in scroll compressor

为了分析涡旋流体机械平衡重随曲轴旋转过程中与周围气体相互作用时所损耗的功率以及平衡重结构对功耗的影响,基于流体力学理论,采用计算机数值模拟方法,应用计算流体动力学软件Fluent建立了平衡腔内流体的滑移网格计算模型.通过改变平衡重所在旋转流体区域的转速得到了平衡重在不同工况条件下受到的各种阻力矩及功率损耗,分析3种结构平衡重径向侧面的压力分布情况,并对比研究平衡重结构变化对功耗的影响.计算结果表明:平衡重随曲轴旋转时径向侧面所受的压差阻力矩远大于其表面的摩擦阻力矩,压差阻力矩是产生功率损耗的主要原因,且各种阻力矩值随着转速的增大而增大;对平衡重径向侧面进行倒角或倒圆角后改善了平衡重表面及腔体内气体流动状况,平衡重所受的压差阻力矩明显减小,倒圆角后平衡重的功率损耗比未倒角时降低了20%以上.

The counterweight that rotates with the crankshaft in a scroll compressor has an interaction with the surrounding gas. In order to study the power loss due to such an interaction and counterweight geometrical effect on the loss, the flow domain in the housing that accommodates the counterweight was established by means of the moving mesh technique in CFD software Fluent. The resistance moment and power loss of the counterweight under different rotational speeds were obtained. Meanwhile the pressure distribution on the three counterweights and the effect of counterweight structure on both the resistance moment and power loss were analyzed too. The results show that the moment due to the pres- sure difference over the surfaces of the counterweight is too much larger than the moment generated by the skin friction during rotation, thus the pressure differential moment is the major cause for power loss production. Both kinds of moment are increased with increasing rotational speed. After the counterweight edges were modified with chamfer; the pressure differential moment was reduced by the improved flow condition around the counterweight so considerably that the power loss was lowered by more than 20%.