圆盘止推静压气体轴承亚音速流场的简化计算

Simplified Calculation of Subsonic Velocity Field of Externally Pressurized Gas Lubricated Circular Thrust Bearings

雷诺气体润滑方程仅涉及轴承气膜内的静压分布,对静压气体轴承流道特性的准确刻画还需要研究轴承流道内的气流速度场。将忽略惯性力的纯粘性等温气膜和等熵流动的供气孔拼接,建立了单供气孔环面节流圆盘止推轴承的流道简化模型,给出流道各部分气流马赫数、雷诺数和压力分布的计算公式。结果表明,气膜中气流速度随矢径变化的性质,取决于速度梯度为零的矢径位置;气膜中的气流雷诺数随矢径的增加不断减小。实际的计算结果表明,只要气膜入口截面上的气流马赫数小于临界声速,整个轴承流道将工作在亚音速,供气压力或气膜高度的变化对气膜起始区域边界层发展段长度的影响很小,供气孔始末端截面上压力和温度的变化也很小,忽略惯性力的纯粘性等温雷诺模型基本能够适用轴承的整个亚音速工况。气膜起始区域边界层发展段的长度,可以用气膜中雷诺数大于临界雷诺数的区域长度来近似。

Profound knowledge of flow passage characteristics of externally pressurized gas bearing need to calculate inner velocity field, while Reynolds equations only relates to static pressure distribution of gas film. Simplified flow passage model was built for externally pressurized gas lubricated circular thrust bearing with single supply hole with inherent compensation, by joint isothermal purely viscous gas film ignoring inertia force with isentropic supply hole. Calculation formula was put forward for velocity, pressure and Reynolds number of whole flow passage. The result shows that velocity distribution characteristics of gas film depends on position of radius at which velocity gradient equal to zero. Reynolds number in film decreases with increased radius throughout. From calculated results ,it is indicated that velocity of whole flow passage is subsonic, when Mach number in cross-intersection of entry film is less than unity. Under subsonic operation variation of supply pressure and gap height has little influence to length of developing boundary layer in start area of gas film. Variation of pressure and temperature between entry and terminal cross-intersection of supply hole is little too. Reynolds equations based on isothermal purely viscous gas film ignoring inertia force is basically applicable to subsonic operation of the gas bearing. Length of developing boundary layer in start area of gas film approximately equals to the area of film in which Reynolds number is greater than critical Reynolds number.