Rotary kinetic fluid motors or pumps – Working fluid passage or distributing means associated with... – Casing having tangential inlet or outlet
Patent
1994-07-18
1996-09-03
Look, Edward K.
Rotary kinetic fluid motors or pumps
Working fluid passage or distributing means associated with...
Casing having tangential inlet or outlet
416186R, 415 1, G05D 701, F04D 1500
Patent
active
055518370
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to an apparatus which regulates the flow through a centrifugal pump used in a closed pipe system.
BACKGROUND OF THE INVENTION
In closed pipe systems, for example heating systems, the demand of the loads connected to the pipe system determines the variable throughflow resistance of the entire system. The loads in a heating system are its heating bodies, where the valves of these heating bodies adapt to the particular heat demand and cause a greater or lesser throughflow resistance.
Since the circulation systems addressed here must be designed for maximum transport flow, but often operate only under partial load, the relationship between the required transport pressure and the transport flow of the centrifugal pump has a characteristic which falls in the direction of zero transport flow. However, the centrifugal pumps which up to now have been used in such circulatory systems have a characteristic which rises in the direction of zero transport flow. That is, the pump head increases as the volumetric flow rate decreases.
If one wished to operate such a centrifugal pump in the system with a steady rpm, the difference between the pressure created by the pump and the specific required pressure had to be throttled out, resulting in a substantial energy loss.
Various regulation systems have already been developed for heating systems to obtain a convenient and economical adaptation to demand. The so-called bypass control is known as a mechanical solution. In a bypass control, a portion of the transport flow is withdrawn by a feedback line of the pressure side of the pump and is again returned to the suction side. This measure does indeed reduce the useful transport flow of the system, but the system characteristic does not shift towards larger transport flows.
At the present time, regulation systems have established themselves which control the rpm of the centrifugal pump so as thereby to achieve broad adaption to various control variables, such as the difference pressure, and the external, inflow, or backflow temperature. This regulation is accomplished either by switching to various prescribed rpms, or, with the correspondingly higher complication continuously varying the rpms. What is true about this rpm regulation in general is that it has small losses compared to the devices described above for regulating the transport flow. However, such a regulatory system is not entirely without losses. Incidentally, with such a regulation too, parts of the pressure difference also must be throttled out.
SUMMARY OF THE INVENTION
It is an object of the present invention to create an apparatus which requires little technical complication, which avoids significant losses, and which adapts to changes of the operating state which occur in a system.
According to the present invention, the object of the present invention is achieved by use of a centrifugal pump whose pump characteristic falls in the direction of zero transport flow.
For the inventive apparatus, a pump characteristic is thus proposed whose pumping head at zero transport flow amounts to about 80% of the pumping head at the design point of the centrifugal pump. Especially with heating systems, use of this type of pump provides especially good adaptation to the operating conditions existing there in heating systems.
A pump characteristic which falls in the direction of zero transport flow can advantageously be realized with a centrifugal pump whose impeller blades have a blade exit angle of 60.degree. or more, preferably 90.degree.. It should be noted that such an impeller, up to now, has not been usual.
Another supporting factor to achieve a falling pump characteristic is a large number of blades, for example 11 or more. The blade exit angle and the number of blades are mutually related, so that the blade exit angle can be reduced as the number of blades is increased.
Still another supporting factor for achieving a falling pump characteristic is for the impeller to have entry edges which are only slightly inclined r
REFERENCES:
patent: 2366251 (1945-01-01), Fullemann
patent: 3205828 (1965-09-01), Rupp
patent: 4158527 (1979-06-01), Burkett
patent: 4166310 (1979-09-01), Rothe
patent: 5026256 (1991-06-01), Kuwabara
Karassik et al., Pump Handbook, 1976, pp. 2-124 to 2-135.
KSB Aktiengesellschaft
Lee Michael S.
Look Edward K.
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