Compression machine with a body oscillating between two reversal points

Abstract

A compression machine (110) includes an oscillating body (111) oscillating between two reversal points (U.sub.1, U.sub.2), wherein the oscillating body has a first mass (m.sub.1), and a maximum value of resulting compression force (F*) when the oscillating body is used is less by a predetermined factor (F) than a maximum value of the resulting compression force when an oscillating reference body (121) having a reference mass (m.sub.ref) is used in a reference compression machine (120) of same construction and using the same fluid (112), wherein the first mass exceeds the reference mass by a percentage that is a function of the predetermined factor, and wherein maximum value of the resulting compression force is reduced by the predetermined factor F by reducing cross-sectional area (A) of the oscillating reference body if the oscillating reference body were used. A related method is also provided.

Claims

1. A compression machine, comprising: an oscillating body (111) with a first mass (m.sub.1) which oscillates in movement (111a) between two reversal points (U.sub.1, U.sub.2) for decompressing and compressing at least a portion of a fluid (112) in an alternating manner; exerting a piston force (F.sub.M) on the fluid for the fluid to exert a fluid force (F.sub.F) on the oscillating body, wherein a resulting compression force (F*) is provided as a difference between the fluid force and the piston force; and using a maximum value of the resulting compression force (F*) when the oscillating body (111) used is less by a predetermined factor (F) than a maximum value of the resulting compression force (F*) when an oscillating reference body (121) having a reference mass (m.sub.ref) is used in a reference compression machine (120) of the same construction, and using the fluid (112); wherein the first mass (m.sub.1) is greater than the reference mass (m.sub.ref) by a percentage that is a function of the predetermined factor (F), and the maximum value of the resulting compression force (F*) would be reduced by the predetermined factor (F) by reducing an effective cross-sectional area (A) of the oscillating reference body (121) if the oscillating reference body (121) were used.

2. The compression machine of claim 1, wherein the oscillating body (111) oscillates between the two reversal points (U.sub.1, U.sub.2) at an oscillating frequency; the maximum value of the resulting compression force (F*) of the oscillating body (111) with the oscillating frequency is less by a second predetermined factor than the maximum value of the resulting compression force (F*) when the oscillating reference body (121) having the reference mass (m.sub.ref) and the oscillating frequency is used in the reference compression machine (120) of the same construction and using the fluid (112); the oscillation frequency is greater than the reference frequency by a percentage amount that is a function of the second predetermined factor; and the maximum value of the resulting compression force (F*) would be reduced by the second predetermined factor by reducing an effective cross-sectional area (A) of the oscillating reference body (121) if the oscillating reference body (121) were used.

3. The compression machine of claim 2, wherein the second predetermined factor comprises values selected from the group consisting of between 0.2 and 0.9, and a second percentage comprises values selected from the group consisting of 0% up to 300%, 50%, 100%, 150%, 200%, 250% and 300%.

4. The compression machine of claim 1, wherein the maximum value of the resulting compression force (F*) when the oscillating body (111) is used is less than a maximum value of a drive force (F.sub.A) that is supplied by a drive unit (115) of the compression machine.

5. The compression machine of claim 4, wherein the drive unit (115) comprises a linear motor.

6. The compression machine of claim 1, wherein the oscillating body (111) comprises a reciprocating piston, or optionally the compression machine (110) is a reciprocating piston compressor.

7. The compression machine of claim 1, wherein the predetermined factor (F) comprises a value between 0.2 and 0.9.

8. The compression machine of claim 1, wherein the percentage comprises values selected from the group consisting of 0% up to 300%, 50%, 100%, 150%, 200%, 250% and 300%.

9. A method for designing a compression machine (110) in which an oscillating body (111) oscillates between two reversal points (U.sub.1, U.sub.2), comprising: oscillating movement (111a) of the oscillating body (111) between decompressing and compressing in alternating manner at least a portion of a fluid (112) of the machine; exerting a piston force (F.sub.M) with the oscillating body on the fluid (112); exerting a fluid force (F.sub.F) with the fluid on the oscillating body (111); providing a resulting compression force (F*) as a difference between the fluid force (F.sub.F) and the piston force (F.sub.M); selecting a first mass (m.sub.1) of the oscillating body (111) such that a maximum value of the resulting compression force (F*) when the oscillating body (111) is used is less by a predetermined factor (F) than a maximum value of the resulting compression force (F*) when an oscillating reference body (121) having a reference mass (m.sub.ref) is used in a reference compression machine (120) of the same construction as the compression machine (110) and using the fluid (112), wherein the first mass (m.sub.1) is greater than the reference mass (m.sub.ref) by a percentage that is a function of the predetermined factor (F); and reducing the maximum value of the resulting compression force (F*) by the predetermined factor (F) by reducing an effective cross-sectional area (A) of the oscillating reference body (121) if the oscillating reference body (121) were used.

10. The method of claim 9 for reducing the resulting compression force (F*), wherein said resulting compression force (F*) having been reduced does not sacrifice delivery capacity of said machine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be explained in greater detail with reference to the accompanying drawings. In the drawings:

(2) FIG. 1 is a diagrammatic representation of one variant of a compression machine according to the invention (FIG. 1a) and two reference compression machines (FIGS. 1b, 1c) and

(3) FIG. 2 shows two schematic force diagrams (FIGS. 2a, 2b) plotted against time, which can be achieved with this variant of a compression machine according to the invention.

DETAILED DESCRIPTION OF INVENTION

(4) A preferred embodiment of a compression machine according to the invention is represented diagrammatically in FIG. 1a and identified with the numeral 110. The compression machine in this example is a reciprocating piston compressor 110.

(5) Reciprocating piston compressor 110 is driven by a linear motor 115. Linear motor 115 is able to supply a maximum driving force F.sub.A. With this supplied force F.sub.A, linear motor 115 drives an oscillating body of reciprocating piston compressor 110. The oscillating body is a reciprocating piston 111. Reciprocating piston 111 has a first mass m.sub.1 and an effective cross-sectional area A. Reciprocating piston 111 is moved in oscillating manner inside cylinder 113 under the force F.sub.A exerted on reciprocating piston 111 by linear motor 115 and oscillates between two reversal points U.sub.1 and U.sub.2, indicated by double-headed arrow 111a. A frequency at which this oscillating motion 111a of reciprocating piston 111 occurs is predetermined by linear motor 115.

(6) In a first stage, piston 111 moves from second reversal point U.sub.2 to first reversal point U.sub.1 and in the process compresses a fluid 112. In a second stage, piston 111 moves from reversal point U.sub.1 to second reversal point U.sub.2 and decompresses fluid 112 (corresponding proportionally to the dimension of the dead space volume). Fluid 112 is able to flow into the cylinder via a feed line 114a, and exit the cylinder via a drain line 114b. During the oscillating movement 111a, piston 111 exerts a piston force F.sub.M on fluid 112 and the fluid exerts a fluid force F.sub.F on piston 111. A resulting compression force F* is formed as the difference between piston force F.sub.M and fluid force F.sub.F.

(7) Since each force changes direction depending on the stage of oscillating motion 111a being performed by the reciprocating piston 111, the forces in FIG. 1 are each represented by a double-headed arrow.

(8) FIG. 1b is a schematic representation of a reference compression machine, which is designated with the numeral 120. Reference compression machine is also a reciprocating piston compressor. This reciprocating piston compressor 120 is of the same construction as reciprocating piston compressor 110, except that reciprocating piston 111 has been replaced with a reference body in the form of a reference reciprocating piston 121. Reference reciprocating piston 121 has the same effective cross-sectional area (diameter 42 mm) and density as reciprocating piston 111, but reference reciprocating piston 121 has a smaller volume and thus also a reference mass m.sub.ref, which is smaller than first mass m.sub.1. Reference reciprocating piston 121 is also driven by linear motor 115 to perform an oscillating movement 121a between the two reversal points U.sub.1 and U.sub.2, so that reference reciprocating piston 121 also decompresses (corresponding proportionally to the dimension of the dead space volume) and compresses fluid 112 by turns.

(9) Since first mass m.sub.1 is larger than reference mass m.sub.ref, a maximum value of the resulting compression force F* exerted by reciprocating piston compressor 110 is smaller than a maximum value of the resulting compression force F* exerted by reference reciprocating piston compressor 120 by a predetermined factor F. First mass m.sub.1 is larger than reference mass m.sub.ref, by a percentage that is a function of said factor F.

(10) This reduction of the maximum value of the resulting compression force F* by a factor F would also not be achieved if the effective cross-sectional area A of reference reciprocating piston 121 were reduced. Accordingly, FIG. 1c is a diagrammatic representation of a second reference reciprocating piston compressor 130 having a second reference reciprocating piston 131 with an effective cross-sectional area A.sub.2 (diameter 16 mm), wherein effective cross-sectional area A.sub.2 is smaller than effective cross-sectional area A. Similarly to second reference reciprocating piston 131, a second cylinder 133 of second reference reciprocating piston compressor 130 has a smaller cross section than cylinder 113. Second reference reciprocating piston compressor 130 is also driven by linear motor 115 driven and also compresses and decompresses (corresponding proportionally to the dimension of the dead space volume) fluid 112 in alternating manner via an oscillating movement 131a. The maximum value of the compression force F* resulting from second reference reciprocating piston compressor 130 is the same as the maximum value of the compression force F* resulting from reciprocating piston compressor 110.

(11) Real examples of the compressor calculated and configured in this embodiment (see FIG. 2): reference compressor: m.sub.ref=16 kg, f=10 Hz=f.sub.osc=f.sub.ref, |F*1 max@10 Hz|=12.33 kN, mass doubled m.sub.1=2m.sub.ref, |F*2 max@10 Hz|=8.9 kN; two-and-a-half times mass: m.sub.1=2.5m.sub.ref, |F*max@10 Hz|=7.35 kN.

(12) Note: There is no linear correlation between increasing the mass and reducing F*. The mass must always be increased specifically for the entire system, so it is not possible to make a blanket statement covering each system. In principle, it should be noted that an increase is useful up to the degree at which the respective quantity-related maximum value of the oscillating piston force, plotted against time/angle, is smaller than or equal to the quantity-related maximum value of the resulting compression force, again plotted against time/angle, of the reference compressor (addition of forces would not yield any advantage beyond this).

(13) Until now, we have only discussed the case in which all movements 111a, 121a and 131a take place at the same frequency. Now the case is to be considered in which the oscillating movements 121a and 131a of reference reciprocating piston 121 and those of second reference reciprocating piston 131 are each performed at a reference frequency f.sub.ref. On the other hand, the oscillating movement 111a of reciprocating piston 111 takes place at an oscillation frequency f.sub.osc, reference frequency f.sub.ref being lower than oscillation frequency f.sub.osc. In this case, the associated maximum value of the resulting compression force F* of reciprocating piston compressor 110 is also the same as the maximum value of the resulting compression force F* of second reference reciprocating piston 130 and less than the maximum value of the resulting compression force F* of reference reciprocating piston compressor 120 by a second factor. Oscillation frequency f.sub.osc and first mass m.sub.1 are each respectively greater than the reference mass m.sub.ref and reference frequency f.sub.ref a by a percentage that is a function of the second factor.

(14) Real examples of the compressor calculated and configured in this embodiment (see FIG. 2): reference compressor: m.sub.ref=16 kg, f.osc. 1=5 Hz==f.sub.ref, |F*1 max@5 Hz 1=14.93 kN, frequency1.5, f.sub.osc=7.5 Hz, |F*2 max@7.5 Hz|=13.84 kN; frequency doubled: f.sub.osc=10 Hz, |F*3 max@10 Hz|=12.33 kN.

(15) Note: There is no linear correlation between increasing the frequency and reducing F*. The frequency must always be increased specifically for the entire system, so it is not possible to make a blanket statement covering each system. In principle, it should be noted that an increase is useful up to the degree at which the respective quantity-related maximum value of the oscillating piston force, plotted against time/angle, is smaller than or equal to the quantity-related maximum value of the resulting compression force, again plotted against time/angle, of the reference compressor; addition of forces would not yield any advantage beyond this.

(16) FIG. 2 shows two schematic diagrams, which can be included in one embodiment of a compression machine according to the invention. For this particular example, a reciprocating piston compressor 110 according to FIG. 1a is assumed, in which first mass m.sub.1 of reciprocating piston 111 has a value of 50 kg. The stroke, that is to say the distance between the two reversal points U.sub.1 and U.sub.2, is 120 mm, the oscillation frequency of oscillating movement 111a is 10 Hz, one period of oscillating movement 111a lasts 100 ms. Linear motor 115 can provide a maximum driving force of 13.8 kN.

(17) FIG. 2a represent the fluid forces generated and the piston force of a reciprocating piston compressor according to FIG. 1a. A force is plotted on the vertical axis, and time t is plotted along the horizontal axis.

(18) Curve 210 shows a first fluid force F.sub.F1, which is exerted on piston 111 by fluid 112 during the first stage. Curve 220 shows a second fluid force F.sub.F2, which is exerted on piston 111 by fluid 112 during the second stage. Curve 230 shows the piston force F.sub.M. At times t.sub.1 and t.sub.3 reciprocating piston 111 is at reversal point U.sub.1 and is changing from the first to the second stage. These are the time points at which fluid 112 is most compressed. At time points t.sub.0, t.sub.2 and t.sub.4, reciprocating piston 111 is at reversal point U.sub.2 and is changing from the second to the first stage. These are the time points at which fluid 112 is most decompressed.

(19) The inventive increase in first mass m.sub.1 with respect to reference mass m.sub.ref makes it possible to reduce the quantity-related maximum values of first and second fluid forces F.sub.F1 and F.sub.F2, which occur at the two reversal points U.sub.1 and U.sub.2. The dashed lines 211 and 221 show a plot of first and second fluid forces F.sub.F1 and F.sub.F2 at the two reversal points U.sub.1 and U.sub.2 for a reference reciprocating piston compressor 120 with a reference reciprocating piston 121 having reference mass m.sub.ref. In this particular example, this reduces the maximum value of first fluid force F.sub.F1 in a quantity-related manner to the value of 20.5 kN. The maximum value of second fluid force F.sub.F2 is reduced in a quantity-related manner to the value of 12.1 kN. As was explained previously, the increase according to the invention of first mass m.sub.1 figuratively has the same effect as a flywheel in an internal combustion engine, increasing the inertia of reciprocating piston 111. Thus, the extremes of the plot of the first and second fluid forces F.sub.F1 and F.sub.F2 against reference reciprocating piston compressor 121 are truncated.

(20) FIG. 2b shows a diagram similar to that in FIG. 2a. In this case, curve 240 shows fluid force F.sub.F, which is the sum of first and second fluid forces F.sub.F1 and F.sub.F2. Curve 250 shows the resulting compression force F*, which is constituted by the difference between fluid force F.sub.F and piston force F.sub.M. Reducing the quantity-related maximum values of the first and second fluid forces F.sub.F1 and F.sub.F2, has the effect of reducing the maximum values of fluid force F.sub.F correspondingly. In this example, the resulting compression force F* has a maximum value of 7.5 kN at the first reversal point and is thus less than the maximum driving force of 13.8 kN.

(21) It should be noted that the amplitude, and therewith also the maximum value of the mass force and thus also of the piston force F.sub.M, is increased when reciprocating piston compressor 110 and reference reciprocating piston compressor 120 are driven by the same linear motor 115 with the same maximum achievable driving force at the same frequency, since a larger mass has to be set in motion by the same driving force F.sub.A. The inventive reduction of the maximum value of the resulting compression force F* by increasing first mass m.sub.1 is not necessarily either larger or smaller than the resulting increase in the maximum value of inertial force F.sub.M.

(22) Indeed, as is shown by curve 250 in FIG. 2b, for example, there are several relatively high values, based on quantity. Increasing the inertial force has the effect of reducing the original maximum, whereas another high value in terms of quantity is increased in this example and becomes the new maximum in the compression process. Thus, the linear relation between increasing the inertial force increase and reducing the original maximum compression force is lost.

LISTING OF REFERENCE SYMBOLS

(23) 110 Compression machine, reciprocating piston compressor 111 Oscillating body, reciprocating piston 111a Oscillating movement 112 Fluid 113 Cylinder 114a Feed line 114b Drain line 115 Linear motor 120 Reference compression machine, reference reciprocating piston compressor 121 Reference body, reference reciprocating piston 121a Oscillating movement 130 Reference compression machine, reference reciprocating piston compressor 131 Reference body, reference reciprocating piston 131a Oscillating movement 133 Cylinder 210, 220, 230, 240, 250 Force diagrams 211, 221 Fluid force curve of a reference reciprocating piston compressor A, A.sub.2 Effective cross-sectional area U.sub.1, U.sub.2 Reversal points F.sub.M Piston force F.sub.F Fluid force F* Resulting compression force F.sub.A Drive force m.sub.1 First mass m.sub.ref Reference mass F Factor f.sub.ref Reference frequency f.sub.osc Oscillating frequency