以V锥流量计在称重法水流量装置和正压法音速喷嘴气流量装置上的实验数据为基础,根据最小二乘法拟合系数所引入不确定度的数学模型，分别对NEL提出的传统V锥、wafer V锥的可膨胀系数公式和徐英等提出的可膨胀系数公式的不确定度进行评定与比较，提出可膨胀系数经验公式的不确定度主要来源于系数拟合所引入的误差。从传统V锥和wafer V锥公式对可膨胀系数规律的预测来看，V锥结构的优化对V锥流量计的标准化具有重要意义。

The experiments about V cone flowmeter both in the water flux standard instrument using weighing method and the gas flow calibration system based on the critical flow nozzles and positive pressure method were carried out. Based on the experiment value and the uncertainty mathematical model of fitting coefficient on the least squares method, uncertainty has been evaluated and compared between the expansibility factor calculation formulas proposed by NEL and Xu Ying respectively. The result can be concluded that the uncertainty about formulas mainly come from the error of fitting coefficient. After analysis of the prediction of expansibility factor respectively by traditional V cone formula and wafer V cone formula, the optimal structure of v cone is very important for the standard V cone flowmeter.