Measuring and testing – Volume or rate of flow – Thermal type
Reexamination Certificate
2001-02-20
2003-08-12
Williams, Hezron (Department: 2855)
Measuring and testing
Volume or rate of flow
Thermal type
Reexamination Certificate
active
06604417
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention belongs to a fluid flow rate detection technology, and particularly relates to a flow rate sensor for detecting the flow rate of fluid flowing in a pipe line. The present invention intends to enhance the detecting accuracy of the flow rate sensor.
Further, the present invention relates to a strainer-integrated portable flowmeter which can be mounted on a pipe line through which kerosene is supplied to a kerosene burning apparatus such as a stove, boiler or the like to measure the flow rate of kerosene while removing a foreign matters such as dust or the like.
(2) Description of the Related Art
Various types of sensors have been hitherto used as a flow rate sensor (or flow velocity sensor) for measuring the flow rate (or flow velocity) of various fluid, particularly liquid, and a so-called thermal (particularly indirectly heated type) flow rate sensor is used because the cost can be easily reduced.
A sensor in which a thin-film heating element and a thin-film temperature sensing element are laminated through an insulating layer on a substrate and the substrate and the fluid in the pipe line are thermally connected to each other is used as an indirectly heated type flow rate sensor. By passing current through the heating element, the temperature sensing element is heated to vary the electrical characteristic of the temperature sensing element such as the value of the electrical resistance of the temperature sensing element. The electrical resistance value (varied on the basis of the temperature increase of the temperature sensing element) is varied in accordance with the flow rate (flow velocity) of fluid flowing in the pipe line. This is because a part of the heating value of the heating element is transferred through the substrate into the fluid, the heating value diffusing into the fluid is varied in accordance with the flow rate (flow velocity) of the fluid, and the heating value to be supplied to the temperature sensing element is varied in accordance with the variation of the heating value diffusing into the fluid, so that the electrical resistance value of the temperature sensing element is varied. The variation of the electrical resistance value of the temperature sensing element is also varied in accordance with the temperature of the fluid. Therefore, a temperature sensing device for temperature compensation is installed in an electrical circuit for measuring the variation of the electrical resistance value of the temperature sensing element to suppress the variation of the flow-rate measurement value due to the temperature of the fluid at maximum.
An indirectly heated type flow rate sensor using thin film elements as described above is disclosed in JP-08-146026(A), for example.
The conventional indirectly heated type flow rate sensor is secured to a linear pipe line portion so that the substrate of a flow rate detector or a casing which is thermally connected to the substrate is exposed from the wall surface of the pipe line to the fluid.
When the fluid is viscous fluid, particularly liquid, the flow-velocity distribution on the section perpendicular to the flow of the fluid in the pipe line becomes ununiform (there is a great difference in flow velocity between the center portion and the outer peripheral portion on the section). In the case of the conventional sensor in which the substrate or the casing portion connected to the substrate is merely exposed to the fluid at the wall of the pipe line, the flow-velocity distribution has a great effect on the precision of the flow-rate measurement. This is because the flow velocity of the fluid flowing at the center portion on the section of the pipe line is not taken into consideration, but only the flow velocity of the fluid in the neighborhood of the wall of the pipe line is taken into consideration. As described above, the conventional flow rate sensor has such a problem that it is difficult to measure the flow rate of fluid accurately when the fluid is viscous fluid. Even when fluid has low viscosity at room temperature, it induces a problem connected to the above viscosity problem because the viscosity of the fluid increases as the temperature is lowered.
The flow rate sensor is required to be used under an extremely broad temperature environment in accordance with a geographical condition, an indoor or outdoor condition, etc. Further, these conditions are added with a season condition, a day or night condition, etc., and the temperature environment is greatly varied. Therefore, there has been required a flow rate sensor which can detect the flow rate accurately under such a broad environmental temperature condition as described above.
As mentioned in the above, the temperature sensing device for temperature compensation is installed in the measuring electrical circuit. However, it is insufficient for suppressing the variation of the flow-rate measurement value due to the temperature of the fluid. Accordingly, it is required to furthermore reduce the temperature dependence of the detected flow rate value to enhance the detecting precision.
Therefore, an object of the present invention is to provide a flow rate sensor which can accurately measure the flow rate of fluid flowing in a pipe line even when the fluid is viscous fluid.
Further, an object of the present invention is to provide a flow rate sensor which can accurately measure the flow rate of the viscous fluid flowing in a pipe line under a broad environmental temperature condition on the basis of lowering the temperature dependence of the detected flow rate value.
Further, a kerosene burning apparatus such as a stove, boiler or the like burns kerosene and produces heat to increase the temperature of air and heat the inside of a room, to heat and boil a large amount of water and to produce high-pressure steam serving as a driving source.
In a boiler
401
shown in
FIGS. 27
,
28
A and
28
B, kerosene is supplied from a tank
402
through a pipe line
403
, and then burned by a burner
404
while sprayed. By using heat produced at this time, a large amount of water is boiled or high-pressure steam is produced, and the combustion gas is discharged from a funnel
405
.
Further, a strainer
407
for removing foreign matter such as dust, motes, etc. is disposed between the tank
402
and the pump
406
, and a flowmeter
408
for measuring the flow rate of kerosene is disposed between the pump
406
and the burner
404
.
However, when minute foreign matters passing through the strainer
407
are gradually accumulated or foreign matters invade between the strainer
407
and the burner
404
, these foreign matters cannot be removed and the foreign matters invade into the nozzle
409
of the burner
404
, thereby closing a part of the discharge port
409
a.
In such a case, the amount of kerosene passing through the nozzle
409
is reduced and thus the burner
404
cannot exhibit its sufficient performance, resulting in reduction of the heat value produced in the boiler
401
. Further, since kerosene is incompletely burned (combusted), the energy held by the kerosene is vainly dissipated to produce incomplete combustion gas such as carbon monoxide or the like, which causes air pollution.
In order to solve the above problem, there has been proposed an air fuel ratio control method for measuring the flow rate of kerosene flowing in a pipe line
403
with a flowmeter
408
disposed in the pipe line and supplying a suitably amount of air corresponding to the measurement value to burn kerosene.
According to this method, even when a part of the discharge port
409
a
of the nozzle
409
is closed, no incomplete combustion occurs and thus the vain consumption of the holding energy of kerosene and the air pollution due to the incomplete combustion can be prevented. If the foreign matters in the nozzle
409
is jetted from the discharged port
409
a
under jetting pressure of kerosene or the like, the burner
404
can exhibits its inherent performance and the heating value of the boiler
401
is resto
Hiraizumi Kenichi
Koike Atsushi
Takahata Takayuki
Yamagishi Kiyoshi
Baker & Daniels
Mack Corey D.
Mitsui Mining & Smelting Co. Ltd.
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