Multi-flow compressors with non-parallel rotational axes

Abstract

The invention relates to the design of multi-flow displacement machines, having non-parallel axes, for the compression preferably of water vapour as refrigerant R718 in particular for cold pump, air conditioning pump and high-temperature heat pump technology. In order to achieve high delivery volume flows in such a displacement compressor, such as that described for example in documents DE 10 2018 001 519 and DE 10 2020 000 350, the invention combines a plurality of displacement compressors, having non-parallel rotational axes, in such a manner that each rotational axis of the left-handed spindle rotors of the displacement compressors is identical to one of the rotational axes of a right-handed spindle rotor of one of the other displacement compressors, as a result of which these can each be mounted on the same shaft, which leads to an axial force compensation, such as is the case for example in two-flow spindle compressors having parallel axes. The axial force compensation is helpful particularly for high-temperature heat pumps and considerably reduces the bearing forces. Water vapour as refrigerant R718 has particularly high volume ratios compared to other refrigerants, which makes high inner compression necessary for efficient compression. This can be achieved more easily using non-parallel axes. As of a four-flow displacement compressor, non-parallel axes and the axial force compensation can be implemented simultaneously by way of this invention.

Description

[0001]

[0002] State of the art:

[0003] Documents DE 10 2018 001 519 and DE 10 2020 000 350 describe twin-shaft rotary displacement machines for the compression of water vapor, preferably as the refrigerant R718, particularly for refrigeration, air conditioning, and heat pump technology. To achieve larger volume flows, which are required when using R718 as a refrigerant, than can technically be achieved with a single machine, several machines are usually operated in parallel. To achieve the high compression ratios often achieved with R718, non-cylindrical rotors are used, whose axes cannot be arranged parallel.

[0004] High axial thrust forces occur in twin-shaft rotary displacement machines. This occurs in high-pressure applications due to the high pressure differentials, and in low-pressure applications due to the large cross-sectional areas of the spindle rotors, which are not technically problematic in conventional rotary displacement machines due to the low speed. However, since high volume flows for the water refrigerant and a dry-running rotary displacement machine (oil-free) are required, such machines operate at high speeds. High speeds with high axial thrust forces are technically complex and lead to high power losses in the axial bearing. In these cases, twin-flow rotary displacement machines with parallel axes are used, in which the axial thrust forces cancel each other out.

[0005] Object of the present invention:

[0006] A targeted arrangement of the rotation axes makes it possible to combine previously incomparable properties of a rotary displacement machine. Previously, in a machine with non-parallel axes, the axial thrust forces could not cancel each other out, and vice versa. Furthermore, the number of components can be halved compared to the state of the art by combining several machines with non-parallel axes in a common housing.

[0007] According to the invention, this object is achieved by combining four or more spindle shaft units (3), each consisting of a left-hand (1.a), a right-hand (1.b), and a motor rotor (2), so that together they form a four- or multi-bladed rotary displacement machine. A left-hand spindle rotor (1.a) of one spindle shaft unit (3) is combined with the right-hand spindle rotor (1.b) of the next. The angle ß resulting between the axes of the spindle shaft units (3) can be selected at the design stage to be equal to or less than 90°. Explanation of the invention:

[0008] To combine the advantage of the canceling axial thrust forces of twin-flow rotary displacement machines with two parallel axes and the high compression ratio required for refrigerant R718, which is easier to achieve with non-parallel axes, in a positive displacement compressor, at least four spindle shaft units (3) are combined. The axial thrust forces cancel each other out in each of the spindle shaft units (3). At their core, they consist of a left-rising spindle rotor (1.a), a right-rising spindle rotor (1.b), and a motor rotor (2), preferably in the center, and can be constructed completely identically. Each axis of the spindle shaft units (3) has the same angle to any two of the other axes.In order to pair two of the spindle shaft units (3) with each other, there must be a gap (6) between the rotors at the diverging end of the axes of each spindle rotor pair (1), as they should not interact with each other. For this to happen, the right combination of angle ß and the distance between the left-rising (1.a) and right-rising spindle rotor (1.b) of a spindle shaft unit (3) must be found. The degree of toothing, i.e. how far the teeth extend beyond the pitch circle, also plays a role here. However, a large distance between the rotors should be avoided in order to keep the critical bending speed high; moreover, this would only make the compressor unnecessarily large. Depending on the length of the shafts of the spindle shaft units (3), these should be supported at two or more locations to keep the critical bending speed high.

[0009] In order to protect all spindle rotor pairs (1) from contact with each other, the use of synchronization gears (9) may be necessary.

[0010] In applications where, due to the very high compression ratio, a division into two compressor stages is required, one of the spindle rotor pairs (1) can be cleverly modified to serve as the second stage, with the remaining pairs supporting it. For this, the pressure differences that occur during operation and the resulting axial thrust forces must be taken into account. Furthermore, this spindle rotor pair (1) must be separated and sealed from the others, since the pressure of the outlet side of the other spindle rotor pairs (1) is now present on the suction side.

[0011] Fig. 1

[0012] Fig. 1 shows an example of a four-flow positive displacement compressor with four spindle rotor pairs (1), each consisting of a left-rising (1.a) and a right-rising spindle rotor (1.b), and four spindle shaft units, each consisting of a left-rising (1.a) and a right-rising spindle rotor (1.b), and a motor rotor (2) located in the center of the shafts. The axes are not parallel.

[0013] The left-rising spindle rotor (1.a) is paired with the right-rising spindle rotor (1.b) of the adjacent spindle shaft unit, forming a spindle rotor pair (1). The left-rising spindle rotor (1.a) of the adjacent spindle shaft unit is paired with the right-rising spindle rotor (1.b) of the next spindle shaft unit, and so on, until you reach the left-rising spindle rotor (1.a) from the beginning.

[0014] Fig. 2

[0015] Fig. 2 shows in a) the top view and in b) the front view of the four-flow positive displacement compressor from Fig. 1. Three of the four spindle rotor pairs (1) are clearly visible. In a) there is a gap (6) between the spindle rotor pairs (1) on the left side, as they do not interact with each other. In b) this gap (6) is between the spindle rotor pairs (1) on the right side. In a) and b) two of the four motor rotors (2) are visible each time, and it is clearly visible that the axes are not parallel to each other.

[0016] Fig. 3

[0017] Fig. 3 shows a spindle shaft unit (3) consisting of a left- (1.a) and a right-rising spindle rotor (1.b), and a motor rotor (2). The spindle shaft unit (3) can be supported by bearings (4) to the left and right of the motor rotor (2), or alternatively by bearings (5) at the shaft end. The use of bearings (4) to the left and right of the motor rotor (2) and the bearings (5) at the shaft end may be necessary for particularly large spindle shaft units (3). An optional synchronization gear is located between the left- (1.a) and right-rising spindle rotor (1.b) and the bearings (5) at the shaft end.

[0018] Fig. 4

[0019] Fig. 4 shows a four-flow positive displacement compressor with its spindle rotor pairs (1), each consisting of a left-rising (1.a), a right-rising spindle rotor (1.b) and a motor rotor (2). Furthermore, the axes are shown extended up to the intersection points (7) with one of the other axes. At the intersection points (7), two of the axes intersect at an angle ß, which can be less than or equal to 90°. Here, it is 6°. Any two of the four intersection points (7) have the same distance A, and the connecting lines between these intersection points (7) are orthogonal to one another. The connection between the two centers (8) of these connecting lines crosses them at a right angle. If this is not the case, the spindle shaft units (3) cannot be identical.

[0020] Fig. 5

[0021] Fig. 5 shows a six-flow positive displacement compressor with six axes. Three of the six motor rotors (2) and several of the spindle rotor pairs (1) are visible, each consisting of a left-rising (1.a) and a right-rising spindle rotor (1.b). Reference symbols:

[0022] 1. Spindle rotor pair a. Left-rising spindle rotor b. Right-rising spindle rotor

[0023] 2. Motor rotor

[0024] 3. Spindle shaft unit

[0025] 4. Bearings to the right and left of the motor rotor (2)

[0026] 5. Bearing at the shaft end

[0027] 6. Gap between two adjacent spindle rotor pairs (1)

[0028] 7. Intersection point of two axes

[0029] 8. Center between two crossing points (7) with distance A

[0030] 9. Synchronization gear

Claims

PATENT CLAIMS 1. Design of a multi-flow positive displacement machine for the compression preferably of water vapor as refrigerant R718, characterized in that it has at least four flows and none of the axes of the spindle shaft units (3) are parallel to each other.

2. R718 compressor according to claim 1, characterized in that it consists of several preferably identical spindle shaft units (3), each comprising at least one left-hand (1.a), one right-hand rising spindle rotor (1.b) and a motor rotor (2), wherein the motor rotor (2) is preferably arranged between the left-hand (1.a) and the right-hand rising spindle rotor (1.b). The spindle shaft units (3) are supported by two bearings (4) arranged between the left-hand (1.a) and the right-hand rising spindle rotor (1.b) and two bearings (5) on the opposite side of the spindle rotors. At least two of the four bearings are mandatory.

3. R718 compressor according to one of the preceding claims, characterized in that the axes of the spindle shaft units (3) preferably intersect at the same angle β in the extension and each pair of the intersection points (7) have the same distance A and the connecting lines of these intersection points (7) are orthogonal to each other.

4. R718 compressor according to one of the preceding claims, characterized in that a gap (6) is present between the left-rising spindle rotor (1.a) of one axis and the right-rising spindle rotor (1.b) of the other axis, which are each located on one of the diverging ends of the axes of each spindle rotor pair (1), and the envelope of the rotors does not penetrate each other.

5. R718 compressor according to one of the preceding claims, characterized in that one spindle rotor pair (1) is used as a second stage for the others, i.e., the outlet sides of the other spindle rotor pairs (1) are connected to its suction side. The suction side is also structurally separated from the suction sides of the other spindle rotor pairs (1) and sealed at the shafts.

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