Turbine meter

A turbine meter for measuring flow rates of various fluids of different coefficients of viscosity. The turbine meter has an impeller including a cylindrical body and a plurality of vanes provided on the outer peripheral surface of the cylindrical body, a tube in which the impeller is rotatably supported, guide members disposed at the upstream side and downstream side of the impeller and adapted for guiding flow of fluid passing through the impeller, and means for permitting the adjustment of the axial distance between two cone members from the outside of the turbine meter.

BACKGROUND OF THE INVENTION 
The present invention relates to a turbine meter for use in measurement of 
flow rate of fluids and, more particularly, to a turbine meter which can 
measure the flow rates of various fluids having relatively high 
viscosities, with a function of adjusting the regions of allowable 
measurement error for various fluids having different viscosities, i.e. a 
function to optimize the measurable regions for respective fluids. 
A turbine meter has been known having a tube and an impeller rotatably 
disposed in the tube, the impeller being adapted to be rotated at a speed 
proportional to the flow velocity of the fluid. 
In this type of turbine meter, there is a relation expressed by the 
following equation (1), between the flow rate Q of the fluid and the 
angular velocity .omega. of the impeller. 
##EQU1## 
where, .alpha.: angle of impeller vane to axis of tube, 
r: mean radius of vane, 
A: area of annular passage defined by inner and outer peripheries of vane, 
Tf: resistance torque of impeller caused by viscosity of fluid against 
rotation by fluid, 
Tm: resistance torque of impeller caused by mechanical resistance against 
rotation by fluid, 
.rho.: density of fluid 
In this equation, the term of resistance torque Tm due to the mechanical 
resistance is negligibly small as compared with the term of resistance 
torque Tf due to the viscosity resistance. 
Thus, the equation (1) can be rewritten without substantial error, as 
following equation (1'). 
##EQU2## 
Representing the viscosity coefficient of the fluid by .mu., the 
above-mentioned resistance torque Tf is given as follows, depending on the 
states of flow of the fluid. 
______________________________________ 
.rho..sup.1/2 .mu..sup.1/2 Q.sup.3/2 
(in case of laminar flow) 
(2) 
(in case of flow intermediate 
(3) 
Tf.alpha. .rho.Q.sup.2 - K.mu.Q 
between laminar and turbulent 
flow) 
.rho.Q.sup.2 
(in case of turbulent flow) 
(4) 
______________________________________ 
Therefore, the ratio of angular velocity to flow rate .omega./Q are 
represented, respectively, by the following equations (5), (6) and (7), 
depending on the states of flow. 
______________________________________ 
##STR1## (5) 
##STR2## 
##STR3## (6) 
##STR4## (7) 
______________________________________ 
In these equations, K.sub.1, K.sub.2 and K.sub.3 represent, respectively, 
different constants. 
As will be understood from these equations, in case of a turbulent flow, 
i.e. in the region represented by the equation (7), the ratio .omega./Q is 
a constant which is independent of the flow rate Q. This means that the 
angular velocity .omega. of the impeller is proportional to the flow rate 
Q. It is therefore possible to measure the flow rate accurately, by 
multiplying the measured angular velocity .omega. by the proportional 
constant. On the other hand, in case of the laminar flow and the 
intermediate state of flow, the ratio .omega./Q cannot be independent of 
the flow rate Q, so that the flow rate Q is not proportional to the 
angular velocity .omega.. Thus, it is impossible to accurately measure the 
flow rate, unless a suitable correction is made. 
In case of measurement of the flow rate of a relatively low viscosity, the 
flow of fluid assumes a state of turbulent flow from a relatively low 
region of flow rate, so that the constant flow rate is obtained even at 
the low region of flow rate. This means that an accurate measurement of 
the flow rate can be achieved over a wide range of flow rate. 
In contrast to the above, in case of fluids having relatively high 
viscosities, the state of laminar flow is maintained until the flow rate 
is increased to a comparatively high level, causing a change of the ratio 
.omega./Q. Therefore, in case of fluids having relatively high 
viscosities, the accurate measurement is achieved only over a limited 
range of flow rate. 
Therefore, the conventional turbine meter, which can measure the flow rate 
of fluids of relatively less viscous fluids such as gasoline, water and 
the like considerably accurately, cannot provide satisfactorily accurately 
the flow rate of relatively viscous fluid such as heavy oil or the like 
over a wide range of flow rate, particularly at a region of relatively 
small flow rate, unless a suitable measure is taken. 
On the other hand, such a measurement system is conceivable as having means 
for making a non-linear processing of the signal produced by the turbine 
meter so as to materially make the ratio .omega./Q constant over a wide 
range of flow rate including region of relatively small flow rate. Such a 
measurement system is effective if it is intended for use in measurement 
of flow rate of only one kind of fluid, but it is disadvantageous in that 
it requires revision of content of the non-linear processing in accordance 
with the viscosities of the fluids, when it is used for a plurality of 
different fluids. 
SUMMARY OF THE INVENTION 
It is therefore a major object of the invention to provide a turbine meter 
capable of widening or spreading the range of flow rate over which the 
measurement can be made accurately, in the measurement of flow rate of 
fluid having a high coefficient of viscosity. 
It is another object of the invention to provide a turbine meter which 
affords an easy adjustment for setting the optimum range of flow rate for 
each of a plurality of different fluids. 
It is still another object of the invention to provide a general-purpose 
turbine meter which can be used for measuring the flow rate of fluids of a 
large variety of viscosities, including fluids of relatively small 
coefficient of viscosity and fluids of relatively large coefficient of 
viscosity. 
To these ends, according to the invention, there is provided a turbine 
meter comprising a tube, an impeller having a cylindrical body and a 
plurality of vanes provided on the outer peripheral surface of the 
cylindrical body, the impeller being rotatably supported in the tube, 
members for guiding the flow of fluid and provided on the upstream and 
downstream ends of the impeller, and means for permitting an adjustment of 
the axial distance between the two members from the outside of the turbine 
meter. 
In the turbine meter of the invention having above stated features, the 
state of flow of the fluid or the viscosity resistance generated at the 
impeller can be adjusted by changing the distance between two guide 
members, so that the range of accurate measurement can be widened even for 
fluids having relatively high viscosities. In addition, since this 
distance is adjustable from the outside of the turbine meter, a single 
turbine meter can be used for the measurement of flow rates of a plurality 
of fluids having different coefficients of viscosity. 
These and other objects, as well as advantageous features of the invention 
will become more clear from the following description of the preferred 
embodiments taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring first to FIG. 1, a turbine meter constructed in accordance with 
the first embodiment of the invention has a cylindrical body 1 on the 
outer peripheral surface of which provided are a plurality of vanes 2. The 
cylindrical body 1 and the vanes 2 in combination constitute an impeller 3 
which is rotatably supported in a tube 4 as a casing, by a cylindrical 
stationary shaft 5, through the medium of a journal, bush and so on. Each 
vane 2 is inclined at an angle .alpha..degree. to the axis 4a of the tube 
4. A conical shaped member 6 provided at the upstream side of the impeller 
3 is adapted to cooperate with another member 7 provided at the downstream 
side of the impeller 3 in guiding the flow of the fluid flowing through 
the impeller 3. The maximum diameter portion 8 of the guide member 6 has a 
diameter larger than the outer diameter 9 of the cylindrical member 1. A 
movable shaft 10 extending through the hollow spaces of the stationary 
shaft 5 and the guide member 7 is connected at its one end to the member 
6. The guide member 7 extended from the stationary shaft 5 has a 
hemispherical shape, and is suspended by a plate shaped supporting member 
11 fixed at both ends by the wall of the tube 4, and is placed 
substantially at the center of the tube 4. 
The impeller 3 is prevented from moving in the axial direction (directions 
of an arrow A) by the member 7 and an annular flange 22 which extends 
radially outwardly from the stationary shaft 5. The maximum diameter 
portion 12 of the member 7 has a diameter equal to the outer diameter of 
the cylindrical body 1. The member 7 is provided with through bores 13. A 
static pressure caused by the fluid flowing through these through bores 13 
acts on the downstream side end surface of the cylindrical body 1, so as 
to allow the impeller 3 to rotate in a floated manner without making any 
contact with the upstream and downstream guide members 6, 7. The threaded 
portion 14 in the member 7 through which the movable shaft 10 extends 
engages a threaded part 15 of the movable shaft 10. Therefore, the movable 
shaft 10 is moved in the axial direction as it is rotated. A worm wheel 16 
provided on the projected end of the movable shaft 10 engages a worm gear 
17. The worm gear 17 is carried by a rotary shaft 18 which is supported at 
its one end by the wall of the tube 4. The other end of the rotary shaft 
18 is projected out of the tube 4. A handle wheel 19 is fixed to the 
projecting end of the rotary shaft 18. As the handle 19 is rotated in one 
or the other direction, the torque is transmitted to the movable shaft 10, 
through the wheel 16 and the worm gear 17, so that the movable shaft 10 is 
rotated. An "O" ring 20 or the like is interposed between the rotary shaft 
18 and the tube 4 so as to form therebetween an effective fluid-tight 
seal. 
A pickup coil 21 disposed on the tube 4 and confronting the vanes 2 is 
adapted to electrically detect the rotation of the impeller 3, through 
sensing the change in magnetic flux caused by the passage of the vanes 2. 
In the turbine meter 22a of the invention having the described 
construction, the rotary shaft 18 and the worm gear 17 are rotated as the 
handle 19 is rotated. As a result, the movable shaft 10 is rotated, 
through the rotation of the worm wheel 16 meshing with the gear 17, so as 
to be displaced in the axial direction relatively to the stationary shaft 
5 and the member 7, by the screwing engagement of the portions 14, 15 with 
each other. The axial movement of the movable shaft 10 in turn causes an 
axial movement of the guide member 6 fixed to the movable shaft 10, so 
that the distance 67 between the members 6, 7 is changed. It is evident 
that the distance 67 between two members is adjustable from the outside of 
the turbine meter 22a. 
In practical use, this distance 67 between the two guide members 6, 7 is 
changed and set in accordance with the coefficient of the viscosity of the 
fluid to be measured, so that the flow of fluid coming from the upstream 
side and guided by the member 6 toward the impeller 3 is rendered 
turbulent as it collides with the vanes 2, depending on the distance 67 
between the two members 6 and 7. 
It is also to be noted that, since the maximum diameter portion 8 of the 
member 6 has a diameter larger than that of the cylindrical body 1, the 
fluid around the base portion of the vanes 2 has no substantial velocity 
component in the direction of the arrow B. Consequently, a laminar flow 
viscous resistance is imposed on the base portions of the vanes 2. 
Provided that this viscous resistance is set to be equal to the term K.mu.Q 
in the foregoing equation (3), the equations (5) to (7) are reformed, 
respectively, to the following equations (8) to (10). 
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##STR5## (8) 
##STR6## 
##STR7## (9) 
##STR8## (10) 
______________________________________ 
The advantage of the described construction of the turbine meter is known 
from the analysis of the equation (8), (9) and (10). This value -K.sub.3 
(.mu./.rho.Q) is negligibly small in the region of turbulent flow at a 
large flow rate. The measurement error in the region of turbulent flow can 
therefore be neglected. In addition, in the intermediate region of 
intermediate state of flow between the laminar and the turbulent flows, 
the ratio .omega./Q is rendered materially independent from the value of 
the flow rate Q. Therefore, this intermediate region is involved in the 
measurement range. 
FIG. 2 shows the relation between the flow rate Q and the ratio .omega./Q. 
The relations observed in a conventional turbine meter and the turbine 
meter of the invention are shown, respectively, by the curves (a) and (b). 
The regions Z1, Z2 and Z3 correspond, respectively, to the region of 
laminar flow, region of the intermediate flow state and the region of the 
turbulent flow. 
Thus, according to the invention, the state of flow of the fluid is shifted 
toward the region of turbulent flow or the region of the intermediate flow 
state. Also, it is possible to impart a desired viscous resistance. It is 
therefore possible to make a measurement of the flow rate of a plurality 
of fluids of a large variety of viscosities, including the fluid having 
relatively low viscosity and the fluid having relatively high viscosity, 
while maintaining the characteristic of the measuring instrument in good 
order. A prompt adjustment of the turbine meter for measurement of flow 
rates of different fluids is possible, if the relation between the 
coefficients of viscosity of fluids and the displacement of the member 6 
(distance between two members 6, 7) has been previously determined for the 
desired range of measurement. It is also possible to determine the amount 
of rotation of the handle 19 corresponding to the coefficients of 
viscosities of different fluids, upon consultation with a scale provided 
in relation to the handle 19. Further, by arranging such that the handle 
19 can be fixed at a predetermined position, a good measuring 
characteristic is ensured for a plurality of turbine meters fabricated in 
accordance with the same specification. Also, the turbine meters are 
rendered easily applicable to different fluids having different 
coefficients of viscosity. 
Referring now to FIG. 3 showing a second embodiment of the invention, the 
maximum diameter portion 8 of the member 6 has a diameter equal to the 
outer diameter 9 of the cylindrical body 1, while the maximum diameter 
portion 12 of the member 7 is made to have a diameter larger than the 
outer diameter 9 of the cylindrical body 1. In this turbine meter 30, only 
the viscous resistance caused at the base portion of the impeller 3 is 
adjusted, by an axial displacement of the member 6 of the upstream side, 
so as to provide a desired measuring characteristics of the turbine meters 
for preselected fluids. 
FIG. 4 shows still another embodiment of the invention in which the maximum 
diameter portions 8 and 12 of the members 6 and 7 are made to be greater 
than the outer diameter 9 of the cylindrical body 1. In this turbine meter 
30a, a viscous resistance is beforehand generated at the base portion of 
the impeller 3, and the state of flow of fluid is shifted to the region of 
intermediate flow state or to the region of the turbulent flow, and the 
viscous resistance is also adjusted, through changing the state of flow by 
displacing the member 6 of the upstream side. This embodiment therefore is 
suitable particularly in such uses as requiring a fine adjustment. 
The maximum diameter portion of either one of the guide members is made to 
be greater than the outer diameter of the cylindrical body. However, the 
present invention is not limited to the said embodiment. That is, the said 
maximum diameter portion is not necessarily made to be greater than the 
outer diameter of the cylindrical body since the flow of fluid may be 
reduced by means of the guide member of the upstream side. Further, in the 
described embodiment, the distance between two guide members are changed 
by a movement of the member 6 of the upstream side. This arrangement, 
however, is not exclusive, and the change of the distance between the 
guide members may be effected by moving the member 7 of the downstream 
side. Further, the shapes of the upstream side and downstream side guide 
members, which are described and illustrated to be conical and 
hemispherical, respectively, may be exchanged. In other words, the 
upstream side and the downstream side guide members 6, 7 can have, 
respectively, a hemispherical shape and a conical shape. It is further 
possible to make the upstream side and downstream side guide members have 
an equal conical or hemispherical shape.