WO2015055218A1

WO2015055218A1 - Ejector pump

Info

Publication number: WO2015055218A1
Application number: PCT/DK2014/050338
Authority: WO
Inventors: Erik Hansen
Original assignee: Ellehammer A/S
Priority date: 2013-10-18
Filing date: 2014-10-16
Publication date: 2015-04-23
Also published as: EP3063415A1; TW201516272A

Abstract

Disclosed is an ejector (1) for pumping a medium using a motive fluid, comprising a housing (2) having an inlet (3) for a medium to be pumped, an inlet (4) for a motive fluid, and an outlet (5) for a mixed fluid of the motive fluid and the entrained medium to be pumped, and a pipe having a constriction (6) part connected to the outlet (5) and a diverging (7) part at the distal end, wherein the inlet (4) for the motive fluid is divided into three sections, the first section in the average direction of the motive fluid stream being a fitting adapted for receiving the motive fluid, the second section in the average direction of the motive fluid stream being a channel for changing the directing of the motive fluid, and a third section in the average direction of the motive fluid stream being a nozzle for ejecting the motive fluid in essentially the same direction as an axial line of the pipe,

Description

Ej ector pum p

Introduction

The present invention relates to an ejector pump for pumping a me- dium using a motive fluid. In particular the present invention relates to an ejector pump with higher efficiency, i.e. a pump in which more medium may be pumped using the same amount of pressure energy of the motive fluid.

Background art

The basic elements of the ejector pump were invented in 1858 by

Henri Giffard. An ejector pump uses the venturi effect of a converging- diverging nozzle to convert pressure energy of a motive fluid into a velocity energy which creates a low pressure zone that draws in and entrains the medium to be pumped. After the converging zone the mixed fluid of motive fluid and entrained medium is conveyed to a constricted zone in which the velocity of the mixed fluid reaches a maximum. Subsequently, the mixed fluid passes to a diverging zone in which the mixed fluid expands, resulting in a pressure drop and a velocity decreases. The reduction in velocity results in a recom- pressing of the mixed fluids by converting the velocity energy back into pres- sure energy.

Subsequently, the ejector pump has been developed into various designs and uses. A suitable example includes US 2,275,627, which discloses a pumping system for supplying water at a sufficient high pressure. The pumping system includes a combination of a centrifugal pump and an ejector pump to obtain higher pressures. The motive fluid enters the ejector pump through an inlet having a curved pipe segment immediately prior to the nozzle.

Another example is disclosed in US 2,350,401 , which relates to an in-line injector for transport of hot (538 °C to 1093°C) gaseous products of combustion from a furnace.

Today, ejector pumps may be purchased from the present applicant.

An example of a standard ejector is shown in Fig. 1 of the present application. The present invention aims at providing an ejection pump with increased effi- ciency, i.e. more medium can pumped using the same or a similar amount of motive fluid energy.

Summary of the invention

The present invention relates to an ejector for pumping a medium us- ing a motive fluid, comprising

- a housing having an inlet for a medium to be pumped, an inlet for a motive fluid, and an outlet for a mixed fluid of the motive fluid and the entrained medium to be pumped,

- a pipe having a constriction part connected to the outlet and a di- verging part at the distal end,

wherein the inlet for the motive fluid is divided into three sections, the first section in the average direction of the motive fluid stream being a fitting adapted for receiving the motive fluid, the second section in the average direction of the motive fluid stream being a channel for changing the directing of the motive fluid, and a third section in the average direction of the motive fluid stream being a nozzle for ejecting the motive fluid in essentially the same direction as an axis of the pipe,

wherein the channel of the second section comprises a rear wall, said rear wall being essentially straight in a direction essentially parallel to the average direction of the motive fluid stream and wherein the cross section in a plan perpendicular to the average flow direction of motive fluid in the channel of the second section decreases in the flow direction.

The new design of the inlet has resulted in an improved efficiency of about 5-10%. It is presently believed that the motive fluid stream is deflected when it impinges on the essentially straight rear wall of the channel in a way that increases the currents in the stream so that a more turbulent stream is created in a least a part of the channel. The at least partly turbulent motive fluid stream will entrain more medium to be pumped when ejected from the nozzle.

According to the present invention the average direction of the fluid is defined as the center of the stream in a plan moving perpendicular to the stream. Thus, for a channel having a cylindrical form the center is the axis of the cylinder. Alternatively, the average direction of the fluid may be defined as the movement of the centre of mass.

The terms "essentially straight" or "essentially parallel" when used in the present description and the claims means that the actual embodiment may deviate 10% or less from straight and parallel, respectively. Thus, the rear wall of the channel may be slightly irregular or curved, while the essential improved effect of the invention is obtained. As an example, in the event the rear wall of the channel is 10cm, the rear wall may deviate 1 cm or less from straight.

Similarly, the essentially straight rear wall may deviate from being parallel to the average direction of the motive fluid stream by 10° or less.

To obtain the best result the angle between the initial average flow direction of the motive fluid in the fitting of the first section and the rear wall of the channel of the second section is between 100° and 160°. In the event the angle in too close to 90 ° the deflection of the fluid will be with a lower direction of the motive fluid towards the nozzle. In the event the angle is too high the direction of the fluid will not be changed significantly and the entering into the third section will be too abrupt.

In a certain embodiment of the invention the cross section in a plan perpendicular to the average flow direction of motive fluid in the channel of the second section decreases in the flow direction. The decreasing cross sectional area increases the pressure in the stream and/or increases the velocity. An increased average velocity when the stream enters the third section is generally desired to increase the turbulent currents.

In an aspect of the invention the essentially straight rear wall of the channel of the second section is rounded in a direction perpendicular to the average direction of the motive fluid stream. The rounded wall increases the flow velocity of the micro currents thereby contributing to the formation of a turbulent stream.

In a certain aspect of the invention the geometrical shape of the channel of the second section can be described by the movement of a generatrix. As examples, the geometrical shape may be a cylinder, a frustoconi- cal, or a polygon. In a specific embodiment the geometrical shape is a cone having suitable cutting plans to allow for a connection to the first and the third section. The altitude of the cone may be 3 to 10 times the weighted diameter of the cutting plane at the end abutting the first section. The angle between the generatrix and the flow direction of the motive fluid may vary between 100° and 160°.

In an aspect of the invention the joint between the channel of the second section and the third section forms a break. The break provides for a discontinuous flow of the motive fluid, which will enhance the turbulent streaming. In a certain aspect of the invention the length of the essentially straight rear wall is larger than the distrance from the joint or break to the tip of the third section. The relative short length of the third section results in a maintanence of the turbulent stream when it exits the tip of the nozzle, thus increasing the ability to entrain the medium.

The ejector pump of the present invention may be used for suction of any fluid. Since the ejector pump has no moving parts the ejectors are sturdy and need no or little maintenance. Thus, mediums having included sand and powder, such as coal powder may be pumped. Liquids, which may be pumped by the present invention, includes sewage water and bilge. The ejector of the invention may also be used for fuel and oil for transferring or stripping since the explosive risk may be lowered or eliminated. Other types of fluids to be pumped include the removal of water from ballast tanks and cargo tanks.

Gasses to be pumped by the ejector pump of the present invention include smoke, potentially explosive gasses, and air. Thus, engine rooms of e.g. ships may be ventilated by suction of smoke, and ballast or cargo tanks may be emptied by pumping the gasses. Due to the absence of moving parts even gasses easily ignited may be pumped.

The housing and the pipe is generally produced in metal. Suitable materials include bronze, aluminium-bronze, cast-iron and stainless steel. For maritime usage a bronze type is generally recommended to avoid excessive corrosion. The nozzle maybe prepared in any durable material. Usually it is preferred to prepare the nozzle from stainless steel. A suitable stainless steel includes AISI 329.

The motive fluid may be a liquid or a gas. Most common is the use of water and air, less common is the use of exhaust gasses and other gasses. A liquid medium like water is generally preferred for pumping other liquids. Basically, the ejector can be motivated by any medium up to a certain viscosity level.

The ejector pump may be designed in a variety of lengths and capacities. Usually, the length of the ejector is not below 40cm to obtain a satis- factory capacity (m³/h) and efficiency. The length does usually not exceed 4.5m for practical reasons. Most suitable, the length is between 1 m and 3m.

Short description of the drawings

Fig. 1 discloses a prior art ejector, in which the suction is created in- line. The ejector may be used for pumping of fluids to or from ballast tanks, cargo tanks, etc.

Fig. 2 is a depiction of an embodiment of the invention having an inlet with a linear rear wall at the mid section.

Fig. 3 shows a view of the housing from above.

Fig. 4 depicts a front view of the housing.

Detailed description of the drawing

Fig. 1 is not according to the invention and discloses a typical ejector for pumping a medium using a motive fluid. The ejector is often described as an in-line ejector because the motive fluid is ejected in the same direction as the flow of the medium to be pumped. According to the prior art ejector a house is provided which has an inlet for the medium to be pumped and an inlet for the motive fluid. An outlet is also present for the combined fluid of medium to be pumped and motive fluid.

The inlet is divided in three sections. In a first section a fitting is provided for connection to a piping system and for the initial receiving of the motive fluid. In a second section the direction of the motive fluid is gently changed in an angle of around 90° by a channel. The channel is evenly rounded to decrease the flow resistance. A third section comprises a nozzle for ejecting the flow of motive fluid in the direction of the pipe.

Fig. 2 is a cross section of an embodiment of the ejector pump 1 of the invention. The line along A-A in Fig. 4 defines the illustrated cross section. The ejector pump comprises two main components: a housing 2 and a pipe 8. The housing has an inlet 3 for the medium to be pumped. The medium may suitably be a liquid but it is also possible to pump a gas using the apparatus of the invention. The medium enters the ejector pump through a not shown piping. The piping is connected to the inlet through suitable fastening means such as rivets, blots and nuts, welding etc. In the embodiment shown in Fig. 2 the inlet is provided with a flange 9 circumventing the outer perimeter of the inlet. The flange is provided with holes (not shown) for mounting of piping using bolts and nuts. Optionally, a gasket is used between the flange and the piping to prevent leakage of medium.

The entering medium to be pumped is received in the housing by the inlet. The housing is widening in diameter immediately after the medium has entered the housing, thereby causing a decrease in pressure. After the initial widening the diameter of the house becomes constant in a mid part of the housing.

The housing further has an inlet 4 for a motive fluid. The inlet intrudes into the housing in the widening part and the mid section thereof. The inlet for the motive fluid may be divided into 3 sections. In a first section 1 1 a fitting is provided for receiving the motive fluid from a suitable source. The source may be a centrifugal pump or similar pumps capable of delivering the pressure of the motive fluid necessary for sucking the medium to be pumped at the desired velocity. Typically, the motive fluid is entering the ejector of the invention at a pressure of 2-12 bar. The inlet is provided with a flange 10 for fastening of the inlet to a suitable piping connecting the ejector to the pump. The flange may be provided with holes for allowing bolts and nuts as fastening means. The inlet fitting is defining an average direction of the motive fluid by the inner walls in direct contact with the fluid. In the specific embodiment, the motive fluid stream enters in an angle essentially perpendicular to the entering medium stream to be pumped. In the part of the first section closest to the second section, the wall may be slightly curved.

In a second section of the inlet a channel 12 is provided for changing the direction of the motive fluid. The inlet 1 1 and channel 12 of the second section may be connected so as to form a break, thereby providing a discontinuous^ flow of the motive fluid. In the illustrated embodiment, the angle between the average flow direction of the motive fluid and the channel is 125°C at the outer part of the motive fluid stream and 135°C at the inner part of the motive fluid stream. The channel comprises a rear wall 13, which is essentially straight in a direction parallel to the average direction of the motive fluid stream. The wall 14 of the channel in contact with the inner part of the motive fluid stream is straight and formed to provide for a decreasing cross section of the motive fluid as is guided through the channel. The decreasing cross- section in the motive fluid direction provides for an increased pressure of the motive fluid.

In a third section 15 a nozzle is provided. The third section and the channel of the second section may be connected so as to form a break thereby providing for a discontinuous flow of the motive fluid. The third section may be provided with an exchangeable nozzle 16, which may be exchanged upon wear or for adaption to a certain fluid. The tip of the nozzle debouches into a converging part 17 of the housing. The jet of motive fluid ejected from the tip of the nozzle forms a decrease in pressure around the tip. The decrease in pressure results in a sucking effect so that the medium to be pumped is entrained into the outlet pipe 8.

Pipe 8 is composed of a constriction part (also termed throat) 6 and a diverging part 7, also referred to as a diffuser. The constriction part is mainly a cylinder having an essentially constant diameter. The length of the constriction part may vary and serves the function of stabilising the currents in the mixed fluid. The constriction part of the pipe is connected to the diffuser in which the cross-sectional area increases along the flow direction. At the end of the diffuser the cross-sectional area is about the same as the cross- sectional area of the inlet 3.

Fig. 3 shows the housing from above through the inlet. The inner structure of the inlet shows the inner walls of the channel 12. It will be noticed that the channel has rounded walls perpendicular to the average flow direc- tion of the motive fluid. It is also noticed that the structure demarks the break between the first and the second section.

Fig. 4 discloses a front view of the housing 2, in which the nozzle 16 is visible. The nozzle is provided co-axially with the pipe 8 so as to provide for an ejection of the motive fluid into the constriction part of the pipe.

Example 1

The present invention was comparred with a conventional in-line injector as shown on Fig. 1 , see Table 1 . The conventional inline injector had a length of 963 mm. Data for the conventional in-line injector was obtained by calculation, whereas the test data for the in-line ejector of the present invention was obtained by physical tests.

The tests were conducted by initial selection of the pressure of the motive fluid. Subsequently, a valve controlling the amount of ejected fluid was adjusted until a preselected pressure on the medium was obtained. The volume stream Q of the medium was finally measured and the efficiency was calculated.

The experimental data shows that the in-line ejector of the invention has an increased efficiency comparred to the conventional in-line injector of around 5-10%.

Table 1 . Comparison of calculations from a conventional in-line ejector with experimental data obtained for the in-line injector of the invention.

Claims

P A T E N T C L A I M S

1 . An ejector (1 ) for pumping a medium using a motive fluid, comprising

- a housing (2) having an inlet (3) for a medium to be pumped, an inlet (4) for a motive fluid, and an outlet (5) for a mixed fluid of the motive fluid and the entrained medium to be pumped,

- a pipe having a constriction (6) part connected to the outlet (5) and a diverging (7) part at the distal end,

wherein the inlet (4) for the motive fluid is divided into three sections, the first section in the average direction of the motive fluid stream being a fitting adapted for receiving the motive fluid, the second section in the average direction of the motive fluid stream being a channel for changing the directing of the motive fluid, and a third section in the average direction of the motive fluid stream being a nozzle for ejecting the motive fluid in essentially the same direction as an axial line of the pipe,

wherein the channel of the second section comprises a rear wall, said rear wall being essentially straight in a direction essentially parallel to the average direction of the motive fluid stream and wherein the cross section in a plan perpendicular to the average flow direction of motive fluid in the chan- nel of the second section decreases in the flow direction.

2. The ejector according to claim 1 , wherein the angle between the initial average flow direction of the motive fluid in the fitting of the first section and the rear wall of the channel of the second section is between 100° and 160°.

3. The ejector according to claim 1 or 2, wherein the essentially the straight rear wall of the channel of the second section is rounded in a direction perpendicular to the average direction of the motive fluid stream.

4. The ejector according to any one of the claims 1 to 3, wherein the geometrical shape of the channel of the second section can be described by the movement of a generatrix.

5. The ejector according to any one of the claims 1 to 4, wherein the angle between the generatrix and the flow direction of the motive fluid varies between 100° and 160°.

6. The ejector according to any one of the claims 1 to 5, wherein the joint between the channel of the second section and the third section forms a break.