钟罩式气体流量标准装置温度梯度影响研究

Analysis of the Influence of Temperature Gradient on Bell Prover Gas Flow Standard Device

钟罩内部封闭气体稳态条件下的温度分布可用拉普拉斯方程描述,边界等温时温度为竖向一维直线方程梯度分布。建立坐标系,将钟罩位置绝对编码,两点测温法获取直线方程。考虑湿度影响导出非线性一维分布气体密度函数,进行空间积分,获钟罩任意高度区间气体质量函数,进而导出质量流量函数。当气体流动满足绝热等熵过程时,根据连续性方程导出流量计处状态下仅关于压力的体积流量函数,有效解决温度测量响应滞后问题。实例计算表明,以点温度代替梯度温度会使钟罩排出气体的质量引入显著的系统误差,必须对密度按空间积分加以修正。

The temperature distribution of the enclosed gas inside the bell under the steady-state condition can be described by the Laplace equation,and the temperature at the boundary isotherm is a vertical one-dimensional linear equation gradient distribution.The coordinate system was established,the position of the bell was absolutely encoded,and the linear equation was obtained by the two-point temperature measurement method.Considering the influence of humidity,the nonlinear one-dimensional distributed gas density function is derived,and the spatial integration is carried out to obtain the gas mass function in any height range of the bell,and then the mass flow function is derived.When the gas flow satisfies the adiabatic isentropic process,according to the continuity equation,the volume flow function of the state at the location of the flowmeter is derived,which effectively solves the problem of temperature measurement response lag.The example calculations show that the substitution of point temperature for gradient temperature will introduce significant systematic error to the mass of the bell exhaust gas,and the density must be corrected by spatial integration.