The present invention generally relates to a liquid ring pump (“pump”) which vents sealing liquid (compressant) from the working chamber of the pump. More particularly, this invention relates to a method of converting liquid ring pumps using a sealing liquid venting system into a pump having a gas venting system in order to accommodate varying compression ratios.
Liquid ring pumps are well known. U.S. Pat. No. 4,498,844, Bissell discloses a liquid ring pump with a conical port member. The conical port member has a vent re-circulation port in addition to the conventional intake and discharge ports. U.S. Pat. No. 4,498,844 is incorporated herein in its entirety.
The pump shown in
The pump has a first head 20 and a second head 22. Each head has a gas inlet 20a, 22a. Each head has a gas discharge 20b, 22b. The heads 20, 22 are located at the axial ends of the liquid ring pump. Located axially between the pump heads 20, 22 is a body or housing 23. Located within the housing is a rotor 25. The rotor 25 has rotor blades 25a. The rotor blades 25a extend from a hub 25b.
The body or housing 23 provides a chamber (working chamber) in which the rotor 25 rotates to draw air or gas 26 through gas inlets 20a, 22a into the working chamber. The gas 26 is then exhausted from the working chamber through gas discharge outlets 20b, 22b.
As can be seen, the gas 26 is drawn into the working chamber through conical port members 27, 28. The gas is also exhausted from the working chamber through conical port members 27, 28. The chamber is divided into a first working chamber 23a and a second working chamber 23b by rotor shroud 25c and lobe shroud 23c.
Sealing liquid 29, see
The liquid ring pump shown in
In addition to having sealing liquid introduction pathways 31, the pump of
The design compression ratio is a ratio of the design discharge pressure to the design suction pressure. The operating compression ratio is a ratio of the operating discharge pressure to the operating suction pressure. In practice the pressure at discharge remains constant and is usually the atmospheric pressure. The suction pressure will vary depending on application.
It is known that a pump having a fixed discharge port and an operating compression ratio less than the design compression ratio will have increased pressure within the working chamber. Increased pressure requires the use of additional pump power. To minimize the need for increased pump power, the prior art, as shown in
The use of compressant or sealing liquid vent paths (liquid leakage paths) has several draw backs. Venting requires a balancing act of continually releasing and replenishing the seal liquid in order to achieve an appropriate pressure within the working chamber. If the seal liquid flow rate is increased over the normal flow rate, then the power control function of the liquid venting method is overcome and pump power can increase at low compression ratios where it can overload the drive system. Further a sudden drop in vacuum pressure from the design compression ratio to a low compression ratio results in a period in which the pump has more liquid in it than the steady state low compression ratio condition. The excess liquid can result in overloads to the drive equipment. Also, if the seal liquid to the pump is reduced, the flow out through the liquid vent paths results in diminished sealing within the pump and the gas volume pumped is reduced.
The disclosure provides for the conversion of a liquid ring pump which utilizes sealing liquid venting, into a pump which utilizes gas venting. Gas venting avoids the pitfalls associated with sealing liquid venting because, in part, it eliminates the need to continually introduce and release sealing liquid. Instead, when the pump is operating at a compression ratio less than the design compression ratio, gas can be vented from the working chamber of the pump to reduce the over compression. In return, this also reduces the shaft power requirements. The conversion of existing liquid ring pumps can be done through only minimal changes to the pump parts.
A sealing liquid pathwayof a liquid ring pump, either used for sealing liquid venting or sealing liquid introduction, is retasked to form a portion of a gas vent. The present disclosure shows retasking a sealing liquid introduction path in a pump head to provide a portion of a gas vent path. The disclosure also provides for converting a sealing liquid vent path of an existing liquid ring pump into a sealing liquid introduction path.
Converting the sealing liquid vent path to a sealing liquid introduction path requires providing a new cone which seals off a portion of the vent path extending through the pump head. The new cone also provides a new channel to allow for the entry of sealing liquid into the working chamber from a pathway in the pump head previously used to form a portion of the sealing liquid vent path. Of course the path retasked to be a sealing liquid introduction path would be repiped to receive sealant.
To provide for the gas vent, the pump head passage previously used for sealing liquid introduction is retasked so that it forms a portion of an appropriately sized passage way to vent gas to the pump discharge. Additionally, the new cone is provided with a vent passage which aligns with an opening in the pump head which was previously an opening for sealing liquid introduction but is now retasked to form an opening into a gas vent in the pump head. The new cone gas passage has a gas port through the cone's conical surface.
The retasked and converted pump permits operation with reduced seal flow to the pump because the pump no longer relies on sealing liquid venting to accommodate varying compression ratios. Additionally, the retasking allows the pump to operate with sealing volume flow rates greater than or equal to 200% of the pump prior to retasking over the entire operating vacuum range of the pump without increasing the power requirements above those of the prior pump. Accordingly, the retasked pump is insensitive to a doubling of seal rate and insensitive to quick drops in vacuum.
a is an end view of a pump head of the type shown in
The present invention converts a pump, which relies on sealing liquid vent paths, also known as liquid leakage paths, into a pump which utilizes a gas vent path. The gas vent path is now used to accommodate varying compression ratios, instead of the sealing liquid vent path. Prior to conversion of the pump, the pump can have all of the features shown in
Prior to conversion, the pump head 40 also has a sealing liquid introduction passage. The seal liquid introduction passage is formed by a channel passage 48a extending through pump head 40 and a channel 48b extending through conical member 46.
To convert the pump shown in
In providing a gas vent channel through a portion of the pump head 40 which was previously used as a portion of a sealing liquid introduction path, it is important to make sure the passageway provided has sufficient area for the release of gas from the working chamber. The smaller the passage, the greater the pressure required at the gas port 448b′ and the greater the power required by the vacuum pump to achieve that pressure at port 448b. The higher power represents increased operating cost to the end user. Tests have shown that a ratio of pump capacity to passage area of 490 to 1,160 CFM per square inch results in an adequate passage cross sectional area. Preferably, no portion of the passage should have a restricted area outside of the desired ratio range.
As best seen in
The new cone 50 is provided with a sealing liquid channel 441b which allows for sealing liquid 29 to now enter the working chamber through what was previously used as a compressant vent channel 41a. A portion of the compressant vent channel 41a is thus retasked to be a sealing liquid introduction path 441a. Also pump 40 is reconfigured so that the compressant vent passage 41a is partially sealed at 41a′. Cone 50 seals the portion 41a′ of vent passage 41a by providing a cone flange 444 that omits vent port 41b. The flange 444 thus seals vent portion 41a at 41a′. The path now retasked as the sealing liquid introduction path 441a, would be repiped as shown in
The term gas used herein is broad enough to include air.
Although an example of the invention has been disclosed, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the spirit and scope of the invention.
All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.
Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.
The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.
This application is a continuation of co-pending U.S. patent application Ser. No. 13/375,695 filed on Dec. 1, 2011, which is the national phase of PCT Application No. PCT/US10/37080 filed on Jun. 2, 2010, which claims priority to U.S. Provisional Patent Application No. 61/220,904 filed on Jun. 26, 2009, the entire contents of all of which are incorporated herein by reference.
Number | Date | Country | |
---|---|---|---|
61220904 | Jun 2009 | US |
Number | Date | Country | |
---|---|---|---|
Parent | 13375695 | Dec 2011 | US |
Child | 14820630 | US |