Study on a Flowmeter with Wells Turbine for Bi-directional Airflow

提出了一种采用威尔斯式水轮机和脉冲式水轮机相结合的新型涡轮流量计，作为测量双向气流的流量传感器。对不同气流型下的井式水轮机和脉冲式水轮机的特性进行了评价。结果得到了下一步的研究结果。(1)在准稳态下，由角速度求出呼吸周期和呼吸流量是可能的。(2)利用已知的涡轮特性曲线和实测的角速度，提出了求解非定常流率的方法。(3)澄清了为了精确测量流量，必须消除涡轮特性曲线中产生的滞回。(4)往复气流型涡轮周围很少产生压差。(5)通过对比井式水轮机和脉冲式水轮机的水轮机特性曲线，可以看出脉冲式水轮机的水轮机特性曲线出现了严重的迟滞现象。(6)通过减少涡轮叶片片数，减小空气阻力，确定了减小迟滞是不可能的。(7)利用PIC微机制作了简单的涡轮转速测量系统，证实了对以呼吸速率为单位的非定常往复气流进行角速度的几乎实时计算和显示是可能的。

The new turbine flowmeter using the Wells turbine and the impulse turbine have been proposed as a flow rate sensor for bi-directional airflow measurement. Characteristics of the Wells turbine and the impulse turbine have been evaluated for the various air flow patterns. Next research results were obtained as the result.(1) It was shown that to obtain the period and the flow rate of the respiration from angular velocity in a quasi steady state was possible.(2) Using an known turbine characteristic curve and measured angular velocity, the method for obtaining the unsteady flow rate was proposed.(3) It was clarified that removal of the hysteresis which arises in the turbine characteristic curve was necessary in order to accurately measure a flow rate.(4) There is seldom the pressure difference which arises around the turbine of a reciprocating airflow type.Therefore, it was shown that discomfort was not given to an examinee, when the turbine was applied to the respiration measurement(5) By the comparison the turbine characteristic curve of the wells turbine and the impulse turbine, it was shown that the hysteresis which appears in the turbine characteristic curve of the impulse turbine is severe.(6) By reducing number of sheet of the turbine blade, reducing the air resistance, it was confirmed that to reduce the hysteresis was not possible.(7) Simple measurement system of the turbine rotational frequency using the PIC microcomputer was manufactured, and it was confirmed that to carry out calculation and display of the angular velocity are possible almost real-time for the unsteady reciprocating airflow with a flow rate as a respiration.