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

点击翻译按钮获取中文摘要

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.