环境条件影响钟罩测量误差的热动力学分析  

Thermodynamical analysis of the effect of environmental conditions on measurement error of bell prover

作　　者：刘夷平[1] 陈超[1] 吴锦川[1] 全晓军[2] 

机构地区：[1]上海市计量测试技术研究院,上海201203 [2]上海交通大学机械与动力工程学院,上海200240

出　　处：《中国测试》2017年第6期118-122,139,共6页China Measurement & Test

基　　金：国家自然科学基金(51276109);上海市质量技术监督局科研项目(2015-35)

摘　　要：使用空调系统调节钟罩式气体流量标准装置的环境温度,其控制效果难以完全满足检定高准确度流量计的要求。为分析钟罩运行期间各状态参数随时间的变化特征,借鉴隙封活塞式气动系统,将排气过程视为一个变容出口系统,建立关于钟罩位移、下降速度、罩内压力和温度的热动力学模型。求解四元常微分方程组,结果表明,如果不考虑气体与环境之间的热交换,会导致一定的测量误差,且误差随着气体与罩壁之间的温差增加而增加。由空调引起的环境压力和温度无规则变化使钟罩内压无法达到恒定,因而排气量变化导致的测量误差难以通过装置结构的改进予以消除。Using air conditioning system to adjust the environmental temperature of bell type gas flow standard device, but its control effect is difficult to fully meet the requirements of the verification of high accuracy flowmeter. In order to obtain time-variant state parameters during the operation period of bell prover, the discharging process was regarded as a one-exit variable- volume system which was similar to clearance -sealed piston pneumatic system, and a thermodynamic model was presented for the displacement and the velocity of bell prover, as well as the pressure and the temperature inside the bell. An analysis of the thermodynamic model was implemented by solving four first order differential equations. The results show that neglecting the heat exchange between gas and environment will give rise to measurement error, which will become larger with the increased temperature difference. The random variation of environmental pressure and temperature caused by air conditioning system prevents the inner pressure from reaching constant, thus the measurement error caused by variable flow rate is hardly eliminated by the improvement of mechanical structures.

关 键 词：计量学 钟罩 热动力学 流量 

分 类 号：TH814[机械工程—仪器科学与技术]