JPH0817550B2 - In-liquid motor and liquid-motor pump with cooling liquid limiting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention provides a part of a handling liquid having high dielectric strength and not corrosive, such as various hydrocarbons and mixtures thereof, and liquefied products of air components other than oxygen. And a submerged motor and a submersible motor pump having the submerged motor, which are made to flow through the motor to perform motor cooling and bearing lubrication,
It is suitable for use in a submerged motor pump for liquefied gas such as LPG (liquefied petroleum gas) and LNG (liquefied natural gas).

[Prior Art] Speeding up of pumps is a trend of the times, and is desired even in submerged motors which have recently been used for large capacity and high head applications. These pumps do not need shaft seals, and if non-contact bearings such as static pressure or dynamic pressure bearings or magnetic bearings are used for the bearings, the pumps of other types such as conventional ground type pumps can be used. When the speed is increased, it is possible to avoid all the wear damage and the like of the sliding portion, which has always been a problem, and it is possible to satisfy the weight reduction and the convenience of handling due to the speed increase.

FIG. 2 is a cross-sectional view of a main part showing a conventional example of a submersible motor pump. Reference numeral 1 is a suction vessel having a suction nozzle 2 and having an upper portion covered and immersed in liquid (water). A motor housing 5 accommodating a motor rotor 3 and a motor stator 4 and a multistage centrifugal pump 6 directly connected to the motor housing 5 are built in.

The multi-stage centrifugal pump 6 includes a suction casing 7 and an intermediate casing 8, accommodates impellers 11 and 12 attached to a pump rotating shaft 10 having a ball bearing 9 supported therein, and stores a main plate of a final stage impeller 12. The balance sheet 14 is formed so as to face the balance disk 13 formed by the back surface (upper surface in the figure), and to hold a gap A in the axial direction (oriented in the axial direction) and a gap B in the radial direction (oriented in the radial direction). Is attached to the casing, an intermediate chamber 15 is formed between the gaps a and b, and the back side (downstream side) of the balance sheet 14 is provided with a gap 16 and an escape passage.
It is designed to communicate with the motor room via 17.

The escape passage 17 has a large flow resistance when it is made to flow into the motor chamber only through the gap 16, so that when the sufficient amount of liquid is discharged through the gap ero, the intermediate chamber 15 becomes low pressure. In many cases, the axial thrust force balance due to the impeller becomes insufficient, so that the liquid is introduced as a bypass to the motor chamber, and the liquid is merged with the flow passing through the gap 16 to be guided to the motor chamber. Is.

During pump operation, a part of the fluid discharged by the final impeller, that is, 5 to 10% of the main flow rate, flows to the motor side through the gap ero of the pump shaft thrust balancer, and part of it Passes through the bearing 9, lubricates and cools it, and then flows into the motor chamber.

The liquid flowing into the motor chamber is the rotor gap of the motor.
After cooling the motor through 18 and several passages 19 formed around the outer periphery of the motor stator, the motor is discharged into the suction vessel 1 through a discharge port provided in an upper motor cover (not shown).
The flow rate distribution to the two flow paths 18 and 19 varies depending on the size and number of the flow paths 19, but in any case, the liquid fluid flows through between the double cylinders having the interval of 0.8 to 1 mm, and the motor is Was supposed to cool.

[Problems to be Solved by the Invention]

However, while the liquid fluid flows between the motor rotor and the motor stator as described above, it is preferable for cooling the motor, but it causes a rotational friction loss, which is a value that cannot be ignored particularly in a high-speed motor.

That is, in a submerged motor or the like, since the motor rotor is in the liquid and its surface area is large, the friction loss with the fluid interposed in the portion is relatively large. And the loss L _f
Is generally Where ρ is the liquid density, ω is the rotor angular velocity, D is the rotor diameter, L is the rotor length, K is the loss coefficient and the Reynolds number Re
, A is a constant.

As seen from the above formula (a), even in consideration of the fact that downsizing of the motor itself by faster Similarity rotor ^L _f αω 1.75~2 ^... (b) next, a conventional 3
A rotor of 21,000 rpm will cause a friction loss of 30 to 50 times that of a rotor of 000 rpm in the same environment, significantly reducing the overall efficiency of the pump motor, and losing most of its industrial meaning. There was a problem that it would end up. In addition,
The above equation (b) has a law of motor core volume D ² L ∝ω ^{-0.75 when} designing a motor. Therefore, if it is similarly reduced, then D ³ ∝ω ^-0.75 D ∝ω ^{-0.25, so} L _f ∝ω ³ D ⁵ ∝ ω ³ · ω ^-0.25 = ω ^1.75 ω ² is larger than that.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a submerged motor and a submerged motor pump, which solve the above-mentioned problems of the prior art and remarkably reduce friction loss with a cooling fluid in a speeded-up motor.

[Means for solving the problem]

In order to achieve the above object, the present invention is a liquid in which a part of a handling liquid having a high dielectric strength such as a liquefied gas and having a high non-corrosive property is allowed to flow into a motor to perform motor cooling and bearing lubrication. In the motor, a flinger attached to the shaft and a bush attached with a small gap around the shaft are provided around the drive side shaft of the submerged motor to limit the inflow of the handled liquid into the rotor gap as much as possible. Along with the inner circumference of the stator,
A limit plate that keeps a gap as small as possible in the axial direction from the inner circumference of the stator is installed to limit the amount of cooling liquid in the stator coil entering the rotor, and the handling liquid flowing into the rotor gap is vaporized by the heat of the motor. And is configured to reduce friction loss.

Further, a submersible motor pump using the submerged motor configured as described above is featured.

[Action]

Since the present invention is configured as described above, when a submerged motor pump is configured using the submerged motor, the pump handling liquid is a part of the main flow rate discharged from the discharge port of the impeller. It flows to the motor side through the gap of the pump shaft thrust balancer, and part of it passes through the bearing to lubricate it.
After cooling, it tries to flow into the motor.

A part of the handling liquid that has flowed in through the passage around the shaft on the drive side of the motor as described above has a part such as a flinger attached to the shaft and a bush attached with a narrow gap around the shaft. The restricting member restricts the inflow to the rotor gap as much as possible, and most of the inflowing handling liquid is guided to the motor stator side which is the stationary part. Further, the backflow of the liquid introduced to the motor stator side to the motor rotor side is limited to a minimum by a limiting plate provided in the inner peripheral portion of the motor stator so as to keep a gap as small as possible in the axial direction. It

In this way, most of the liquid passes through the motor stator side passage to cool the motor stator, then flows into the upper coil end to cool it, and then is discharged from the upper discharge port. The coil end portion is also provided with a limiting plate similar to the above-described limiting plate, so that the inflow of the handling liquid from this portion to the motor rotor side is also limited to the minimum.

On the other hand, since the handling liquid flowing into the rotor gap is limited as described above, it is evaporated by the heat of the motor generated inside and becomes a gas phase, and the motor rotor rotates in the gas phase atmosphere. Will be done. Therefore, the friction loss between the motor rotor portion and the handled liquid is reduced as follows.

Reynolds number Re of the flow is involved in K in the above-mentioned equation (a), and it is generally said that K is proportional to Re -1/5. Taking liquefied methane as an example of the liquid to be handled, in the saturated state of −162 ° C., the viscosity coefficient μ is about 1/30 of that of liquid in vapor. However, since the density ρ is about 1/590 of that of liquid in steam, Re = vd / ν (ν: kinematic viscosity coefficient ν = μ / ρ) The kinematic viscosity ν used in the above equation is 20 times (590 / 30≈20), v is the rotor peripheral speed, and d is the rotor clearance (actually the radial clearance 1 /
If 2) is taken, Re becomes 1/20 of the liquid with steam, so
K (K ∝Re ^-1/5 ) in the equation (a) is larger for steam (approximately
1.8 times). However, the friction loss L _f includes a first-order term of the density ρ as can be seen from the equation (a), and the ρ is 1/590 of the liquid as described above, and as a result, , Vapor is much smaller than liquid. That is, by gasifying the periphery of the motor rotor, even if the number of revolutions is increased to 7 times, the friction loss becomes approximately 7 ² × 1 / 330≈1 / 6 as compared with the case where the periphery is liquid at low revolutions. This is much smaller than when the liquid is forced to flow through the rotor gap with a conventional two-pole electric motor.

Although the above description has been given by taking liquefied methane as an example, the situation is the same even if other liquefied gases are applied. From this, it is understood that if the periphery of the motor rotor is surrounded by gas, the rotor friction loss does not pose any problem at high speed.

Also, when applied to other than the submerged motor pump, the submerged motor operates in substantially the same manner.

〔Example〕

 Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a vertical cross-sectional view showing an embodiment of a submersible motor pump using a submersible motor of the present invention, in which the same reference numerals as those shown in FIG. 2 are the same or similar parts. Shall be indicated.

In the figure, between the outer peripheral surface of the liner ring 12a integrally formed on the back surface of the main plate of the impeller 12 and the inner peripheral surface of the casing 8, a fixed throttle portion having a fixed axial clearance B is formed. An intermediate chamber 15 is formed between the liner ring 12a and a balance disc 13 formed integrally with the boss portion of the main plate, and the balance sheet 14 is casing with a radial gap G between the balance disc 13 and the balance disc 13. 8, the balance disk 13 and the balance sheet 14 form a variable throttle portion, and the inner diameter side of the balance sheet 14 is
The conventional point (Fig. 2) is that the bearing 9 communicates with the interior of the motor through the ball gap and the escape passage (17 in Fig. 2).
There is no change.

Further, in this embodiment, behind the bearing 9 (upper in the figure)
Is provided with a chamber 21, and in order to prevent the liquid flowing into the chamber 21 from flowing toward the motor rotor 3 side, a flinger 22 is attached to the shaft 10 and is swung outward in the radial direction of the flinger 22. A through hole d is provided to guide the liquid to the motor stator 4 side with the least resistance.

Further, in order to prevent the liquid that has passed through the bearing 9 from flowing to the motor rotor 3, a bush 23 is attached around the shaft 10 between the chamber 21 and the motor rotor 3 with a narrow gap c, Further, in order to prevent the liquid guided to the motor stator 4 side from flowing back to the rotor 3 side, the bush 23
In addition, a ring-shaped limiting plate 24 is attached to the inner peripheral portion of the stator while keeping a gap a as narrow as possible in the axial direction.

On the other hand, on the other side portion (upper portion in the figure) of the motor stator 4, an upper limiting plate 25 formed in a ring shape so as to surround the upper coil end portion 4b and an inner peripheral portion of the stator is provided. The upper limit plate 25 is provided with an inlet port G on the outer peripheral portion thereof and an upper surface portion thereof with a discharge passage L to the outside.

Further, in order to lubricate and cool the upper bearing 9a, a small hole is provided at the bottom of the discharge port 26a of the motor cover 26, and a small amount of liquid is injected from the discharge side through the internal passage, Again, after passing through the bearing 9a, the bush 23a
The liquid d into the rotor 3 side is restricted by the narrow gap d, and the upper coil end is formed by the hole formed in the upper restriction plate 25.
It facilitates the inflow of liquid to 4b. In the figure, E and F are rotor gaps corresponding to 18 and 19 in the conventional one (Fig. 2), and passages formed at several places on the outer peripheral surface of the motor stator, 27 is a motor casing, and 27a is a suction. mouth,
The arrows with blades indicate the pump handling liquid main flow path, and the small arrows indicate the motor cooling liquid flow path.

Next, the operation will be described. When the pump is in operation, 5 to 10% of the main flow rate that is sucked from the suction port 27a and discharged from the discharge port of the impeller 12 passes through the gap yellow of the pump shaft thrust balancer. Flow to the motor side, some of which
After passing through the bypass passage (c) to the motor stator 4 and the rest passing through the bearing 9 for lubrication and cooling, the shaft 10
The liquid that has flowed into the chamber 21 through the passage around is guided by the flinger 22 to the stator 4 through the through hole D, and the remaining portion passes through the slit c of the bush 24 and the rotor 3 Be led to. Therefore, the liquid that flows into the rotor 3 is limited as much as possible, and most of the liquid that has flowed in through the clearance gap is guided to the side of the motor stator 4 that is the stationary portion. Further, the backflow of the liquid introduced to the motor stator 4 side to the motor rotor 3 side is limited to the minimum by the inner peripheral portion of the motor stator and the limiting plate 24 which holds the slit a in the axial direction.

As described above, most of the liquid passes through the motor stator side passage to cool the motor stator 4, and then flows into the upper coil end 4b to cool it, and then is discharged from the upper discharge passage le. However, since the annular limiting plate 25 is also provided here, the inflow of the handling liquid from this portion to the motor rotor 3 side is also limited to the minimum by the slit b.

As described above, since the liquid to be handled flowing into the rotor gap portion E is limited as much as possible, it is evaporated by the motor heat generated inside to be in the gas phase, and the motor rotor 3 rotates in the atmosphere in the gas phase. Therefore, the friction loss between the motor rotor and the liquid to be handled is significantly reduced.

According to this embodiment, the amount of liquid flowing into the rotor clearance E around the motor rotor 3 is extremely small, and the electric / magnetic generated in the motor rotor is said to account for 20 to 30% of the electric / magnetic loss of the entire motor. The heat generated by the loss evaporates, and the latent heat thereof cools the roller 3 and at the same time maintains the rotor gap in the gas phase, so that the friction loss due to the rotation of the rotor can be made equal to that in the air.

If the amount of liquid flowing into the motor rotor 3 side is too severely limited and the rotor temperature rises too much, small holes are appropriately provided in the inner circumference of the upper limiting plate 25 to supply the cooling liquid. Also in this case, since the liquid does not flow through the rotor gap e, the surface of the rotor 3 is covered with the gas due to the film boiling state, and the friction loss does not increase.

In the independent test in the liquid, the above is the case of the immersion operation in the low temperature liquefied gas and the flow rate sufficient to take away the loss heat only in the sensible heat in the rotor gap by the separate pump in addition to the immersion. Confirmed by the fact that there is a noticeable difference in motor input seen with liquid flow through, which is equivalent to the specified liquid friction loss.

Further, when the flow rate of the liquid flowing through the gaps i and b is insufficient for the amount of heat generated by the motor, it is possible to inject the liquid from the discharge passage through the small holes e to assist the cooling of the motor.

〔The invention's effect〕

As described above, according to the present invention, a part of the handling liquid, which has high dielectric strength and is non-corrosive in the liquefied gas, is made to flow into the motor to perform motor cooling and bearing lubrication. In the motor, a flinger attached to the shaft and a bush attached with a small gap around the shaft are provided around the drive side shaft of the submerged motor to limit the inflow of the handled liquid into the rotor gap as much as possible. Along with the inner circumference of the stator,
A limit plate that keeps a gap as small as possible in the axial direction from the inner circumference of the stator is installed to limit the amount of cooling liquid in the stator coil entering the rotor, and the handling liquid flowing into the rotor gap is vaporized by the heat of the motor. Since the motor rotor rotates in the gas phase due to the configuration that reduces the friction loss, the rotational friction loss of the motor rotor is drastically reduced, and the motor efficiency is reduced without a decrease in the motor efficiency due to the increase in the loss. A submerged motor and a high speed submerged motor pump can be obtained.

In addition, the restricting member that restricts the inflow of the handled liquid into the rotor gap is composed of a flinger and a bush, and the restricting member that limits the amount of the cooling liquid for the stator coil entering the rotor is positioned as much as possible in the inner circumference of the stator and in the axial direction. By using the limiting plate that holds the narrow gap, it is possible to minimize the inflow of the handled liquid into the rotor gap portion with a simple structure.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a submersible motor pump using the submersible motor of the present invention, and FIG. 2 is a sectional view of a main part of a submersible motor pump showing a conventional example. 9 ... Bearing, 10 ... Pump / motor shaft, 12 ... Impeller,
13 …… Balance disk, 14 …… Balance sheet, 15…
… Intermediate room, 22 …… Fringer, 23,23a …… Bush, 2
4, 25 ... Limit plate, 26 ... Motor cover, a, b, c,
d ... slit.

Claims (2)

[Claims] 1. A submerged motor in which a part of a handling liquid having a high dielectric strength such as liquefied gas and which is non-corrosive is allowed to flow through the motor for motor cooling and bearing lubrication. A flinger attached to the shaft and a bush attached with a small gap around the shaft are provided around the drive-side shaft to limit the inflow of the handled liquid into the rotor gap as much as possible, and to close the inner circumference of the stator. The limiter plate that keeps a gap as small as possible in the axial direction from the inner circumference of the stator is provided to limit the amount of cooling liquid in the stator coil that enters the rotor, and the liquid that flows into the rotor gap is controlled by the heat of the motor. A submerged motor with a cooling liquid limiting device, characterized in that it is configured to reduce friction loss as a phase. 2. A pump impeller is directly connected to the drive side shaft of the motor according to claim 1, and a part of the handling liquid discharged from the pump impeller is made to flow into the motor. A submersible motor pump having a submersible motor according to claim 1, wherein a limiting member is provided around an axis between the vehicle and the motor.