【作者】 魏列江；

【导师】 卢堃；

【作者基本信息】 兰州理工大学 ， 流体机械及工程， 2009， 博士

【摘要】 随着流体系统向微小化方向的发展,对微小流量进行精确测量的需求越来越多。在医疗器械、流体元件检漏、不规则零件配合公差检验、微小流体器件流动特性研究、微小孔径或毛细管管径测量和生化防护等领域中,常常要对被测试件的微小流量(每分钟几毫升至几百毫升)进行高精度的测量,一般是在定常流条件下进行微小流量的测量。目前,定常流条件下测量流量时,测量系统必须具备高精度的液体恒压装置,这增加了测量系统的复杂性；再有,常用的流量仪表对于微小流量的测量存在误差大、仪表自身压力损失大等问题,难以直接应用于微小流量的测量系统中,定常流条件下测量微小流量的原理实质上就是“秒表-量杯法”,测量的自动化程度不高、操作复杂。针对目前微小流量测量中的上述问题,本文提出了一种用非定常流等效定常流测量微小流量的原理及其实现方法。基于流体力学非定常流伯努利积分理论,建立了圆角薄壁小孔、锐缘薄壁小孔和细长圆管等三种典型微小流道自由出流时,非定常流等效定常流测量应满足的水头适用条件；得出了典型微小流道中非恒定水头的非线性微分方程,分析了非定常流等效定常流测量的理论误差,并实验验证了理论分析的正确性。基于非定常流等效定常流测量微小流量的原理,成功研制出了一种人工机械心脏瓣膜返流量测量装置并实现产业化；针对静脉输液针的通流检测试验,设计出了多段标定的非定常流流量测量装置；针对水压轴向柱塞泵中配流盘摩擦副的间隙检测,设计出了通过测量间隙泄漏流量确定摩擦副间隙的测量装置。论文的主要内容：第1章,阐述了本课题的研究意义和目的,概述了微小流量测量的研究现状和发展状况,现有方法存在的问题,概述了本文的主要研究内容。第2章,在定常流条件下,建立了圆角薄壁小孔、锐缘薄壁小孔和细长圆管等三种典型微小流道自由出流的流动模型,基于流体力学定常流伯努利方程,推导出了典型微小流道出流的流量计算公式。根据微小流量测量的特点,分别设计了静态质量法、静态容积法、动态质量法和动态容积法测量装置,并指出了定常流条件下微小流量测量存在的问题。第3章,提出了用非定常流等效定常流测量微小流量的原理,在非定常流条件下,建立了典型微小流道自由出流的流动模型,基于非定常流伯努利积分,推导出了非定常水头下典型微小流道出流的流量计算公式,由此建立了非定常流等效定常流测量微小流量时,测量装置应满足的水头适用条件,并求解分析了理论误差。第4章,建立了微小流量的非定常流测量实验装置,对标准流量块进行了非定常流条件下的实际流量测量,该测量结果与定常流条件下的实际测量结果进行了对比,得出“实测的误差随着被试件过流断面面积a与测量容器过流断面面积A的比值a/A增大而增大”的结论,验证了理论分析的正确性。对测量的误差来源做了分析,提出了理论误差的补偿方法,第5章,介绍了人工机械心脏瓣膜返流量的非定常流测量装置研制过程,对本文提出的微小流量非定常流等效定常流的测量原理进行实际应用和验证。第6章,针对静脉输液针的通流检测试验,设计出了多段标定的非定常流流量测量装置；针对水压轴向柱塞泵中配流盘摩擦副的间隙检测,设计出了通过测量间隙泄漏流量确定摩擦副间隙的测量装置。最后,总结了本论文的研究工作和结论,展望了未来的研究工作。本文的主要创新点概括如下：(1)提出了用非定常流等效定常流测量微小流量的原理及其实现方法,为微小流量的测量方法及测量装置的设计提供了新的思路。(2)基于流体力学非定常流伯努利积分原理,得出了非定常流等效定常流测量微小流量的面积适用条件和水头适用条件。(3)研制成功了人工机械心脏瓣膜返流量的非定常流测量装置,并实现产业化。更多还原

【Abstract】 Accurate minute flow measurement is widely required along with fluidic systems grow smaller in size. The minimum flow may be ml/min in medical devices, leak detection of hydraulic components, tolerance check for irregular shape, study of flow characteristics of MEMS, micro tube or capillary tube diameters measurement and biochemical defense. Nowadays, minute flow measurement is under the condition of steady flow and it requires precise hydraulic constant pressure instrument. This will cause the complexity of measuring system. Besides, it is obvious that conventional flow meter is difficult to be used in minute flow measurement for great measuring errors and high pressure loss.In this dissertation, unsteady flow measuring principle is proposed and the applications of this method are developed.Based on unsteady flow Bernoulli equation, three typical models of outflow through minute flow paths are established for round corner thin-wall hole, sharp corner thin-wall hole and long hole respectively. Then corresponding flow formulas and elevation conditions for application (ECA) of the method are deduced. Nonlinear differential equations are built for unsteady minute flow under inconstant pressure. Theoretical measuring errors are computed and analyzed. Experimental instrument for unsteady minute flow measurement is established. Test results prove the correction of the theoretical analysis. For measuring the regurgitant volume of artificial mechanical cardiac valve prosthese, an unsteady flow measuring instrument is developed. This device has been industrialized. For flow check of intra-vein catheter, an unsteady flow measuring instrument is designed, which is multi-pieces marked. For valve plate couples of water axial piston pump, clearance leak flow measuring instrument is studied and manufactured. With this instrument, the clearance of the couples can be obtained.The thesis contains 6 chapters.In chapter 1, the objective and significance of the study are stated. Current research situations of minute flow measurement are analyzed and the main contents of the study are introduced.In chapter 2, under the condition of steady flow, three typical models of outflow through minute flow paths are established for minute round corner thin-wall hole, sharp corner thin-wall hole and long hole respectively. Based on steady flow Bernoulli integral equation, correspondent flow formulas are deduced. According to the characteristics of minute flow, four measuring methods are proposed,named static mass memthod,static volume method, dynamic mass method and dynamic volume method,and corresponding instruments are designed.Meanwhile,the existing problems for steady minute flow measurement are pointed out.In chapter 3,unsteady minute flow measuring principle is proposed.Based on unsteady flow Bernoulli imegral equation.three models are established for typical free outflow through minute flow paths.Then,corresponding flow formulas and elevation conditions for application(ECA)of the method are deduced.Theoretical measuring errors are analyzed.In chapter 4,experimental instrument of unsteady flow measurement is established. Unsteady flow and steady flow measuring methods are both applied to standard flow check block and the results are compared.The test results show that measuring errors will increase with the ratio of flow seetion area of tested component(a)to that of measuring instrument(A). This proves the coffeetion of the theoretical analysis.The causes of measuring errors are analyzed and error compensation methods are proposed.In chapter 5,specified measuring instrument is studied and manufactured for regurgitant volume in artificial mechanical cardiac valve prosthese.Unsteady flow measuring principle is applied in the device thus proved correct.In chapter 6,an unsteady flow measuring instrument,which is multi-pieces marked,is designed for flow check of intra-vein catheter.Clearance leak flow measuring instrument is studied and developed for valve plate couples of water axial piston pump.With this instrument,the clearance of the couples can be obtained.At last,the main results and conclusions of this work are summarized,and further research plan is brollght forward.This research is initiative as follows:(1) Unsteady minute flow measuring principle and the realization are proposed.It puts forward a new way for minute flow measurement.(2) Based on unsteady flow and Bernoulli integral equations,the elevation conditions for applications(ECA)of this method are deduced.(3)Unsteady flow measuring instrument for regurgitant volume of artificial mechanical cardiac valve prosthese is developed and industrialized.更多还原