NO343954B1

NO343954B1 - Inverted Eductor Jet Pump

Info

Publication number: NO343954B1
Application number: NO20181300A
Authority: NO
Inventors: Inge Skagen
Original assignee: Submatech As
Priority date: 2018-10-09
Filing date: 2018-10-09
Publication date: 2019-07-29
Also published as: NO20181300A1; WO2020076162A1

Description

INVERTED EDUCTOR JET PUMP

The invention relates to a pump, and more specifically to a jet pump comprising a rotor encircling a conduit.

BACKGROUND

Eductor jet pumps work by utilizing the Venturi effect by introducing a high-pressure jet into a pipe or housing with a restriction creating an acceleration chamber, thereby creating a pressure reduction that causes a suction effect through a conduit into the housing. This enables transport of a medium to be moved or mixed through the conduit and the housing. Eductor pumps are widely known and used for various purposes. The terms eductor or ejector systems are used interchangeably but generally eductor is used when driving fluid is a liquid and ejector is used when driving fluid is a gas.

An inverted eductor or ejector jet pump work by utilizing the same effect, a driving jet stream is injected into an open ended housing, but the jet stream is encircling the conduit. The fluid is accelerated through the housing, thereby creating a pressure reduction causing a suction effect through a conduit in fluid connection with the housing. For transport of a medium with large unit size (i.e. gravel and rocks) it is not favorable to use a restriction in the acceleration chamber to further accelerate the medium as this will increase risk of blockage.

The maximum driving pressure difference in eductor sytems are the pressure difference between ambient pressure and vacuum. At surface level the maximum pressure difference is 1 atm, at 10 m water depth the pressure difference is doubled to 2 atm and at 100 m water depth the pressure difference is 11 atm. The potential pressure difference at 100 m water depth is thus approximately 10 times the pressure difference at surface level. The potential pressure difference is what makes eductor systems so efficient in underwater transport systems.

Previously known eductor and ejector jet pumps (also mixing or injecting eductors) are designed with a separate driving unit; a pump, producing the pressurized fluid to be used to create the pressure difference. Such systems have an external high pressure or a high flow pump supplying the eductor or ejector pump with the driving fluid.

Eductor systems are typically driven by an external hydraulic or electrical pump. For a hydraulic drive system, energy is first converted to hydraulic pressure, then the hydraulic pressure and flow is used to drive a hydraulic motor, again driving a water pump, creating pressure in the driving fluid. The driving fluid is transferred by hoses, pipes, bends and manifold to the eductor system to drive the system.

Electrical driven pump systems reduce the number of energy conversions but still have significant loss in transfer and transport of energy.

In energy conversions and transfers energy is lost. The different energy transfers and stages must also be tuned to each stage of energy conversion complicating system design and optimalisation. A hydraulic pump creating hydraulic pressure must be tuned to the energy available from the driving motor and the hydraulic pump volume and thereby system flow to the driving motor revolutions. A hydraulic motor driving the water pump must likewise be tuned to the specification of the pump and the driving pressure supplying pump must be tuned to the eductor to create the correct pressure for the pumps correct energy.

There is therefore a need for an improved jet pump to reduce or eliminate the above mentioned disadvantages of known techniques. It is an objective of the present invention to achieve this and to provide further advantages over the state of the art.

Documents useful for understanding the field of technology include NO321977, US8579495, EP 3046227, WO 2018/037232 and US 2010/0150742.

SUMMARY

In an embodiment, there is provided a jet pump. The jet pump comprises a pump housing comprising an inlet end and an outlet end in fluid communication via an acceleration chamber; a pressure chamber in fluid communication with and positioned upstream of the acceleration chamber, a conduit in fluid communication with the acceleration chamber, the conduit extending from the pump housing, an axial portion of the conduit being arranged inside an axial portion of the inlet end, a rotor driven by a drive unit, the rotor encircling an axial portion of the conduit, for creating a flow of fluid into the acceleration chamber via the pressure chamber from the inlet end, thereby creating a suction effect in the conduit.

According to another embodiment of the invention the rotor is encircling the conduit at the inlet end.

According to another embodiment of the invention the rotor is an impeller or a propeller.

According to another embodiment of the invention the pressure chamber is formed between the conduit and the pump housing.

According to another embodiment of the invention the conduit extends past the inlet end and into the pump housing between the inlet end and the outlet end.

According to another embodiment of the invention the conduit comprises a flexible portion.

According to another embodiment of the invention the pump housing comprises a diffusor at the outlet end.

According to another embodiment of the invention the jet pump is an inverted eductor jet pump, and the fluid is a liquid.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other characteristics will become clear from the following description of embodiments, given as non-restrictive examples, with reference to the attached schematic figures.

Figure 1 is a perspective view of an embodiment of the inverted eductor jet pump according to the invention.

Figure 2 is a sectional view through the longitudinal centre axis of an embodiment of the inverted eductor jet pump according to the invention.

Figure 3 is a sectional view of the plane A-A in figure 2.

DETAILED DESCRIPTION

The following description may use terms such as “horizontal”, “vertical”, “lateral”, “back and forth”, “up and down”, ”upper”, “lower”, “inner”, “outer”, “forward”, “rear”, etc. These terms generally refer to the views and orientations as shown in the figures and that are associated with a normal use of the invention. The terms are used for the reader’s convenience only and shall not be limiting.

Referring initially to figure 1, an embodiment of a jet pump 1 according to the invention is illustrated. The illustrated jet pump 1 is an eductor jet pump, meaning that a liquid, such as water, is used as a driving fluid, but the same principles are also applicable to an ejector jet pump. The inverted eductor jet pump 1 comprises a conduit 2. The conduit 2 may be rigid or flexible, and may be a pipe or a hose, or a combination thereof, depending on application. A rigid conduit 2 may also comprise flexible elements or portions. The conduit 2 is configured for conveying medium into the jet pump 1, the medium may be material from e.g. a seabed such as gravel, mud, clay, etc.

The jet pump 1 also comprises a pump housing 3, to which the conduit 2 is connected. The axial portion of the conduit 2 inside the housing 3 may e.g. be rigid, while the portion on the outside of the pump housing 3 may be flexible. The pump housing 3 comprises an inlet end 4 and an outlet end 5. The conduit 2 is positioned inside the inlet end 4, i.e. the inlet end 4 encircles the conduit 2. The outlet end 5 is an exhaust end where both fluid and conveyed medium is exhausted. This is described further with reference to figure 2.

The medium to be conveyed may be abrasive material like mud, rocks and gravel, or alternatively sensitive material like live fish as there is no contact between the pumped material and the rotating or driving units. Because the inlet end 4 is encircling the conduit 2, and the conduit 2 and outlet end 5 may be arranged in a straight line, e.g. fish or other medium which requires gentle handling could be sucked in and transported from one location to another.

The jet pump 1 further comprises a rotor 6. The rotor 6 may encircle an axial portion of the conduit 2, i.e. the rotor 6 has a large center hole or an opening at the centre through which the conduit 2 extends through. The rotor 6 may be an impeller or a propeller, rotatably mounted to the conduit 2 or to the pump housing 3. If the rotor 6 is mounted to the conduit 2, or a portion of the pump housing 3 at an inner diameter of the rotor 6, the blades of the rotor 6 point in a radial direction outwards from a mounting surface 15, as illustrated in the figures. If the rotor 6 is mounted to the pump housing 3, or a portion of the conduit 2 at an outer diameter of the rotor 6, the blades of the rotor 6 point in a radial direction inwards from a mounting surface.

If the rotor 6 is rotatably mounted to the conduit 2, support brackets 14 or other means may connect and keep the conduit 2 rigid and fixed relative to the pump housing 3. The rotor 6 is driven by a motor or other driving mechanism, as is described with reference to figure 2 and 3. The rotor 6 may have several different configurations; it may be an impeller type with folding vanes, or it could be a water jet impeller type.

The jet pump 1 thus combines the flow driving unit and the eductor or ejector unit into one unit to facilitate an integrated pump. I.e. the rotor 6 may be combined with the conduit 2 in one unit. In the jet pump 1 energy conversions creating the driving pressure jet is done in the eductor or ejector unit saving energy by reducing energy conversion cycles, transport of energy transferring fluid and thus creating a more energy efficient system.

The inverted eductor jet pump 1 system is utilizing only one moving part, the rotor 2 (in the instance of a Permanent Magnet (PM) motor drive) and facilitate a simplified design by reducing the number of design parameters and parts, and thus also provides for cost efficient production, improved reliability and increased maintenance cycle time.

The conveyed medium has no contact with the moving part, making the pump very reliable and wear resistant when transporting abrasive material. The pump system, compared to existing systems avoid risk of pollution due to oil spillage from hydraulic drive systems or oil filled compensated motor drive systems. The system could potentially have only one moving part (the rotor), again reducing the amount of wear and tear.

Referring now to figure 2, which illustrates a sectional side view of an jet pump 1, and figure 3, which is a sectional view in direction A of figure 2. The straight, unmarked arrows in figure 2 indicates the flow direction of the driving fluid and the conveyed medium, this is explained later. The curved arrows in figure 3 indicates the rotational direction of the rotor 6. The rotor 6 may be rotated by a drive unit 7 based on an axial driven permanent magnet (PM) motor. PM motors are very efficient and comprises few moving parts. Current may be switched in a three phase fashion in stator coils 8, creating a rotating magnetic field making a rotating force working on permanent magnets 9 embedded in the circumference of the rotor 6. The illustrated PM motor comprises 12 stator coils connected in a three phase arrangement, and in figure 3, 16 magnets are arranged on the outer circumference of the rotor 6, facilitating a 16 pole system.

The motor may alternatively be e.g. a PM motor with stator arranged around the conduit and magnets arranged on the inner circumference of the rotor.

A range of other options for driving the rotor exist, such as geared or magnetic coupled electrical motors, or geared or magnetic coupled hydraulic motors.

The rotating movement of the rotor 6 drives surrounding fluid into a pressure chamber 10, this is indicated by two short arrows at the inlet 4 in figure 2. The driving fluid is pressurized in the pressure chamber 10 and guided into the acceleration chamber 11, also indicated by two short arrows in figure 2. The inlet end 4, outlet end 5 and acceleration chamber 11 may as such form a venturi tube. The pressure chamber 10 is positioned upstream of the acceleration chamber 11, and may also comprise fluid straightening vanes (not shown). In the illustrated embodiment, the pressure chamber 10 encircles an axial portion of the conduit 2, such that a flow of conveyed medium through the conduit 2 is transported through the centre of the pressure chamber 10. The pressure chamber 10 may be a chamber formed between the pump housing 3 and an interior channel 12, the interior channel 12 being a portion of an inner frame of the pump housing 3. In the illustrated embodiment, the pump housing 3 has a narrowing diameter from the inlet 4 towards the acceleration chamber 11, while the interior channel 12 extends along the flow direction towards the acceleration chamber 11. The conduit 2 is in this embodiment housed in the interior channel 12 of the pump housing 3. Alternatively, the pressure chamber 10 may be formed between the exterior of the pump housing 3 and the inner end of the conduit 2 itself.

A fluid flow is thus created from the pressure chamber 10 into the acceleration chamber 11 in the interior of the pump housing 3. The fluid is accelerated through the acceleration chamber 11, and may be exhausted through a diffusor at the outlet end 5, indicated by two parallel arrows in figure 2. The fluid flow creates an underpressure at the interior end 13 of the conduit 2, upstream of the acceleration chamber 11, and thus creates a suction effect and movement of fluid, material or other medium to be conveyed through the conduit 2, indicated by a long arrow in figure 2. The effect can be described by Bernoulli's principle that states that an increase in the speed of a fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy.

The pressure in an open system will try to equalize causing fluid to flow to the lower pressure area. The relation between the sectional area and fluid flow in the acceleration chamber 11 and in the conduit 2 will try to equalize by accelerating the water in the conduit 5 to achieve the same velocity (same diameter pipe).

While the invention has been described with reference to the embodiment(s) mentioned above, it is to be understood that modifications and variations can be made without departing from the scope of the present invention, and such modifications and variations shall remain within the field and scope of the invention.

Claims

1. A jet pump (1), comprising;

a pump housing (3) comprising an inlet end (4) and an outlet end (5) in fluid communication via an acceleration chamber (11);

a pressure chamber (10) in fluid communication with and positioned upstream of the acceleration chamber (11);

a conduit (2) in fluid communication with the acceleration chamber (11), the conduit (2) extending from the pump housing (3);

an axial portion of the conduit (2) being arranged inside an axial portion of the inlet end (4);

characterized in a rotor (6) driven by a drive unit (7), the rotor (6) encircling an axial portion of the conduit (2), for creating a flow of fluid into the acceleration chamber (11) via the pressure chamber (10) from the inlet end (4), thereby creating a suction effect in the conduit (2).

2. The jet pump (1) according to claim 1, where the rotor (6) is encircling the conduit (2) at the inlet end (4).

3. The jet pump (1) according to claim 1, where the rotor (6) is an impeller or a propeller.

4. The jet pump (1) according to claim 3, where the pressure chamber (10) is formed between the conduit (2) and the pump housing (3).

5. The jet pump (1) according to any one of the preceding claims, where the conduit (2) extends past the inlet end (4) and into the pump housing (3) between the inlet end (4) and the outlet end (5).

6. The jet pump (1) according to any one of the preceding claims, where the conduit (2) comprises a flexible portion.

7. The jet pump (1) according to any one of the preceding claims, where the pump housing (3) comprises a diffusor at the outlet end (5).

8. The jet pump (1) according to any one of the preceding claims, where the jet pump (1) is an inverted eductor jet pump, and the fluid is a liquid.