Hiroshi Maki

A Study on Mass Transfer between Recirculation Zone and Outside Flow of Annular Premixed Flame

A mass transfer between recirculation zone and outside flow of an annular premixed propane flame was investigated experimentally using MgO powder tracing method and NaCl flame emission. The loacation of the stagnation point in the recirculation zone of the burning flow moved gradually from the nozzle exit with an increase of the gas exit velocity and became constant independently of the gas exit velocity in the very high velocity region. In the region of lower gas exit velocity, the average residence time of the fluid in the recirculation zone of the burning flow was evidently smaller than the time of the cold flow (air) at the same exit velocity, and both residence times decrease gradually with an increase of the gas exit velocity and became a same constant value in the region of very high velocity. Thus, the rate of mass transfer through the surface of the recirculation zone of a high velocity burning flow issuing from the annular nozzle was estimated by the data on the annular air jet.

Measurement of Pulsating Flow Rate by means of Float-Area-Type Flow Meters

In order to extend availability of a float-area-type flow meter, flow rate characteristics of the float-area-type flow meter when the frequency of pulsating flow was much larger than the resonant frequency of a float in the direction of the flow were theoretically and experimentally studied. As the result it was found that the indicated float position for the pulsating flow rate was always higher than that for steady flow rate. Limits of availability were ascertained as the result of the pulsating flow measurements.

Float-area-type Flow Meters with Constant Discharge Coefficients : General Flow Rate Characteristics When the Gradient of a Tapered Tube is Large

Discharge coefficients, including general flow rate characteristics when the gradient of a tapered tube is large, of float-area-type flow meters are generally discussed. It is experimentally pointed out that the discharge coefficients became constant when a float, having the small length of the maximum diameter part of the float and having 180° vertex angle of the cone portions upstream of the maximum diameter part of the float, and a particular tapered tube having the gradient k=0.545 are employed. When employing such a combination of the float and the tapered tube, a semi-empirical formula to predict the flow rate characteristics is obtained and the limits of applicability of the formula are experimentally explained. Finally, a float-are-type flow meter having linear relations between the flow rate and the position of the float is manufactured.

Discharge Coefficients of Float-Area-Type Flow Meters

In this paper, in order to improve the measuring accuracy of this kind of flow meter, it is experimentally pointed out that the commonly used discharge coefficients of float-area-type flow meters do not always have constant values over a wide range of characteristic Reynolds number even in the region of Re larger than critical characteristic Reynolds number Rec. It is shown that only in the case of the floats having special shapes or geometrical dimensions the discharge coefficients of this kind of flow meters have constant values independing on the non-dimensional position of float. When employing such float, semi-empirical formula to predict the flow rate characteristics is obtained, and the limits of applicability of the formula are experimentally explained.

On the Experimental Investigations of Float-Area-Type Flow Meters : Turbulent Region

From the theoretical results reported before, the flow rate characteristics of float-area-type flow meters were formulated as a function of four dimensionless parameters, when the flow in the clearance between the tapered tube and the float was laminar. In this study, the flow rate characteristics for turbulent region were experimentally examined. It was pointed out that the flow rate characteristics were greatly influenced by the separation of flow at minimum clearance. As a result, widely used floats having usual shapes were classified into two types, i.e., floats with large length of the part of the maximum diameter and those with small length of that part. It was experimentally shown that the number of dimensionless parameters influencing the flow rate characteristics were reduced to three when large-length floats were employed and to two when small-length floats were employed, respectively. Moreover, when small-length floats were employed, a semi-empirical formula to obtain the general flow rate characteristics of this kind of flow meter was proposed.