EP1991776A1

EP1991776A1 - Multistage compressor

Info

Publication number: EP1991776A1
Application number: EP07704481A
Authority: EP
Inventors: Klaus Bäumer; Dirk Grulich; Herbert Wiegand
Original assignee: Deutsches Zentrum fuer Luft und Raumfahrt eV
Current assignee: Deutsches Zentrum fuer Luft und Raumfahrt eV
Priority date: 2006-03-07
Filing date: 2007-02-09
Publication date: 2008-11-19
Also published as: US20090220357A1; WO2007101768A1; DE102006047657A1

Abstract

The invention relates to a multistage compressor for providing high-pressure gas in filling stations, said compressor consisting of a high-pressure compressor and a multistage booster compressor (VV). Both compressors comprise membrane pump chambers which are controlled by camshafts. The booster compressor (VV) can contain a plurality of stages (S1, S2, S3), the chambers in each stage forming groups (G1, G2, G3) of chambers. The chambers of a group are synchronously operated in phase. The chambers of two successive stages are operated in opposition of phase. The number of chambers in a group is approximately the same as the pressure ratio π, so that the size of the chambers can be standardised.

Description

Multi-stage compressor

The invention relates to a multi-stage compressor for compressing gases, and more particularly to a membrane compressor for a gas refueling system for refueling a motor vehicle powered by natural gas, methane or similar gases as well as by hydrogen.

Problematic with gases as energy storage In the motor vehicle is compared to liquid fuels in natural gas by three orders of magnitude higher storage volume requirements at ambient conditions. Therefore, it has been determined to provide natural gas at a pressure of 250 bar at the filling stations available, so that a predetermined by the technical rules pressure of 200 bar in Druckgasbehäiter a vehicle at a reference temperature of 15 ° C and not exceeded. In order to At least only about 3 times the storage space in the car must be provided in comparison to the gasoline vehicle.

In the case of gas filling plants for direct fueling with a compressor, the compression leads to an undesired heating of the gas, which has the greater effect the greater the step pressure ratio π. To achieve the desired final pressure, the pressure ratio π can be reduced by increasing the number of stages.

In gas filling plants, the insertion work to be performed leads to a heating of the gas in the compressed gas tank. The Joule-Thomson effect (temperature change of the gas by throttling) of the real gas counteracts this heating in general. However, only under very favorable conditions, d. h, at a sufficiently low temperature, the Joule-Thomson effect and the heat release to the environment are sufficient to compensate for the heating caused by the insertion work of the gas. If these favorable conditions are not met, it comes in gas refueling without cooling device during transfer or direct refueling to underfilling the gas cylinder, the reason is that the Einschiebearbeit a high temperature and thus a correspondingly high pressure in Druckgasbehäiter sets, what the available pressure difference for the filling so much lowered that the refueling process takes a long time and is therefore canceled before the compressed gas tank contains the possible gas mass according to the technical rules.

DE 197 05 601 A1 describes a natural gas refueling process without cooling the gas, in which the refueling process of the pressurized gas container is carried out until the pressure in the line to the pressurized gas container exceeds a maximum pressure. Another possibility provides that the refueling process is aborted when the mass flow falls below a threshold value. WO 97/06383 Al describes a gas charging system for high-pressure bottles. The cooling of the gas takes place here by winding the high-pressure fissure to be filled, whereby two connections for flow and return are required. In the rinse cycle, the gas is cooled by a heat exchanger or by mixing with the gas in the reservoir.

EP 0 653 585 A1 discloses a system for refueling a pressurized gas container. Therein the execution of a test shock is described and used for its evaluation, the thermal equation of state for the real gas. It also describes switching to higher pressure reservoirs (multi-bank process) during refueling. The fueling process is intermittent. There is no cooling device for the gas provided.

DE 102 18 678 B4 describes a method and an apparatus in which the gas for filling the compressed gas container is passed from a high pressure storage container via a vortex tube as Kuhlvorrichtung. The vortex tube exploits the existing pressure difference in the refueling system to divide the gas stream into a hot gas stream and cold gas stream. The latter is then fed to the compressed gas container.

DE 10 2005 006 751 A1 also discloses a device in which, with the aid of a vortex tube, a temperature reduction of gases is achieved without separation into a hot gas flow and cold gas flow.

The operation of the two last-mentioned methods and apparatus is based on supplying the gas at a supercritical pressure ratio to a swirl generator arranged axially between two pipes having a different inlet diameter. a temperature reduction of gases with a vortex tube succeeds and only if supercritical pressure conditions exist. At a critical Pressure ratio for natural gas of 1 / π ^* <0.5427 and a pressure in the reservoir of ρ _v = 250 bar, which is usually undershot, if several vehicles are refueled in quick succession, a subcritical state is reached when in the pressure gas tank, the pressure has risen to ρ _D = 135 bar. This means that when filling a compressed gas tank with natural gas in the pressure range between ρ _n = 135 bar to p _D = 200bai under the conditions prescribed by the technical rules, by using a vortex tube no temperature reduction of the gas is more to achieve.

WO 01/27475 A1 describes a star-shaped multistage membrane compressor in which the compressor chambers are arranged in a star shape around a crankshaft. The compressor chambers form the individual stages of a multi-stage compressor and therefore have different volumes. In this way, high compression ratios can be realized, but with the generation of considerable heat of compression.

Direct refueling independent of gas stations is appropriate where the construction of publicly available natural gas filling stations is not worthwhile, vehicles could be refueled there - and not only those of private transport - where they are during their downtime. This can be in industrial parks, garages or car boards. Many households or buildings have natural gas available for heating purposes. This natural gas can be compressed in the garage by means of a compressor (natural gas compressor) during the night from the usual natural gas pressure level of 50 mbar to 200bar at a reference temperature of 15 ° C. This can be refueled a motor vehicle.

Another way to use such a refueling system is seen in agriculture, where biogas is produced in large quantities. Instead of feeding this biogas into a public gas grid, this could be compressed on the spot and used to operate agricultural vehicles and Machines are used. This would make it possible in the future to replace biodiesei in agriculture. One of the requirements of this compressor is that the compressor must be capable of full refueling in one night (approx. 8 hours) at 200 bar and a reference temperature of 15 ° C.

The main problem of a multi-stage high-pressure compressor is the heating of the gas between the individual compressor stages and the cooling of the gas at the compressor outlet, which must never exceed 60 ⁰ C when entering the compressed gas tank during refueling.

The invention has the object of providing a multi-stage compressor in such a way that it is possible by direct refueling a Druckgasbehälter befüüen that a predetermined by the technical rules limit value of the pressure in the compressed gas tank is achieved at a predetermined limit temperature.

The multi-stage compressor according to the invention is defined by the patent claim 1. After that, the high-pressure compressor is preceded by a supercharger which has at least one precompressor stage, each precompressor stage containing a plurality of chambers, which are combined to form at least one group, and wherein the chambers of a group are jointly and synchronously driven.

The invention is based on the idea that in a high-pressure compressor in membrane construction to reduce the pressure ratio, the number of stages of the high-pressure compressor should not be increased, but the high pressure compressor should be preceded by a single or multi-stage supercharger. By such a supercharger not only the pressure ratio π in the high-pressure compressor can be lowered, but - without changing the dimensions of the high-pressure compressor - also increase the mass flow rate proportional to the increase in the form. By combining a supercharger with a high-pressure compressor - both designed in membrane design - a gas refueling system can be created, which meets, with respect to its mass flow rate (refueling time) the most diverse requirements. This is achieved by a single or multi-stage supercharger, if its membrane dimensions are identical to the dimensions of the first stage diaphragm of the high pressure compressor. This is the case regardless of the number of stages, if an integer value π = 2, 3, 4 ... is selected for the pressure ratio π in the supercharger.

The invention makes it possible to use standardized multi-membrane pumps. Even the sizes of the pump chambers of the different stages can be equal to one another. But it is also possible to make the pump chambers interchangeable in a pumping device with star-shaped pump chambers, so that pump chambers of different sizes are available, which can be optionally mounted in the pumping device.

In the case of direct refueling, it is possible with a multistage supercharger to maintain a supercritical pressure ratio until the end of the filling of a pressurized gas container at a tank pressure of 200 bar. This allows, as described in DE 10 2005 016 114 Al already described in detail, by using a Wirbeirohres or using a Eindüselements according to DE 100 31 155 C2 or only by adiabatic throttling to lower the gas temperature that a temperature increase can be compensated by the insertion work. In this way, even with a direct refueling, regardless of the ambient temperature, a filling with a tank pressure of 200 bar a reference temperature of 15 ° C can be realized. If the high pressure compressor according to the invention is also designed as a membrane compressor, it can be operated at the same speed via a common WeNe with the upstream diaphragm pre-compressor.

A particularly expedient embodiment of the invention provides that for very large Gasvoiumenströmen the first and subsequent stages of the supercharger are divided into several membrane chambers, if for material reasons, the necessary for a large volume flow membrane diameter is not feasible. For example, in the case of a single-stage supercharger with a pressure ratio π = 2, the first stage of the high-pressure compressor can be supplied with twice the gas mass flow compared to a high-pressure compressor which is operated without a supercharger. To achieve this, the supercharger must be equipped with two membrane chambers, which have the same dimensions as the first stage of the high pressure compressor, depending on the size of the pre-compressor to be produced in the form and increasing gas mass flow are different variations in the inventive design of the supercharger possible, which are explained below with reference to a simple mathematical consideration.

Put the geometric series

l + x + x ² + x ³ + x ^l! (1)

in which the quotient of two consecutive terms is constant and in the present case the size x describes the pressure ratio π and the exponent n the number of membrane chambers per level, so that the above equation has the following form

1 + π + π ² + π ³ + π "(2) let represent. From equation (2) results for a pressure ratio of

π = 2: 1 + 2 + 4 + 8 + 2 "π = 3: 1 + 3 + 9 + 27 + 3" _π = 4: 1 + 4 + 16 + 64 + 4 "

wherein in the practice of initially only the combination listed in the following Tabeiie are to be realized.

At a pressure ratio of π = 2, the two diaphragm chambers of the last stage of the supercharger must match in dimensions with the first stage of the downstream high-pressure compressor in membrane construction. For a pressure ratio of π = 3, this applies to the three membrane chambers and to a pressure ratio of π = 4 for the four membrane chambers of the last stage of the supercharger,

Assuming that the supercharger is operated at the same speed as the downstream high pressure compressor in membrane mode and the stroke in the individual diaphragm chambers is the same as the diaphragm stroke in the first stage of the high pressure compressor, then it can be demonstrated that the diameter of the diaphragm chambers always the membrane diameter corresponds to the first stage of the high pressure compressor. The pressure ratio π must always be the number z of the membrane chambers / stage and an integer π = 2, 3, 4 which is independent of the step pressure ratio Π _HD in the high-pressure compressor.

For a single stage supercharger with the pressure ratio π = 4, a diameter Di and

4 membrane chambers in the 1st stage: Z ₁ = 4

lets show that

L stage: V ₁ = Z, * ^ ² = 4D ₁ ² HD ₁ : V _([DI = V _{l / π} = (4D, ³ ) / 4

^D I ID1 = ( ^D 1 ~) ^{= D} !

is.

Here, V _{1 is} the volume of the first stage, D _{1 is} the diameter of the first stage of the supercharger, HDi is the diameter of the first stage of the high pressure compressor, V _{HDI is} the volume of the first stage of the high pressure compressor, D is _HDI the diameter of the first stage of the high pressure compressor, Z _n is the number of diaphragm pumps in stage n.

For a two-stage supercharger with the spinning ratio π = 3, a diameter Di and

9 membrane chambers in the 1, step, Zi = 9 3 membrane chambers in the 2nd step, Z ₂ = 3

you get 1 stage: V _] = z, * D _s ² = 9D _i ²

2 stage: V ₂ = V ₁ / π = (9D, ² ) / 3 = 3D, ²

D ₂ = (3D ₁ - / Z ₂ ) " ⁵ = (3D _P ^2/3 ) ^(U = DI HD ₁ : V ₁₁₀₁ = V ₂ / π = (3D, ² ) / 3 D ₁₁₀₁ = (D ₁ ² ) ⁰⁵ = D,

and a three-stage supercharger with the pressure ratio π = 2, a diameter Di and

8 membrane chambers in the 1st stage, Z ₁ = 8 4 membrane chambers in the 2nd stage, Z ₂ = 4 2 membrane chambers in the 3rd stage, Z ₃ = 2

you get

I, step: V ₁ = z, * D, ^" = 8D, ^~

2nd stage: V, = V ₁ / rc = (8D, ² ) / 2 = 4D,

D _a = (4D _ι - / z ₃ f ⁱ = (4D _l ^" / 4) \ O, 5 D,

3, step: V ₃ = V ₂ / π = (4D _| ² ) / 2 = 2D,

D ₃ = (2D ₁ ² / z ₃₎ ⁰ - ^s = (2D _l ^2/2) = D ^os _ι

HD ₁ : V _HDi = V ₃ / π = (2D ₁ ² ) / 2 = D _ι ² D ₁₁₀₁ = (D ₁ ² ) "- ⁵ = D ₁

A particular advantage of a pre-compressor designed in this way is that in the subdivision of the stages into individual membrane chambers, the same components can be used to save costs. These are as essential parts of the supercharger, the membranes of the membrane chambers, which all have the same dimensions as the membrane of the first stage of the downstream high-pressure compressor in membrane construction. Another advantage of the invention is that the dimensions of the membrane or the diaphragm chambers are independent of the pressure ratio, the volume flow rate and the desired outlet pressure of the supercharger. According to the invention, it is also possible to increase by a supercharger, the delivery volume of a high-pressure compressor in membrane design either initially by two to nine times compared to an operation without a pre-compressor.

In the following Ausführungsbeϊsptele the invention are explained in detail with reference to the drawings.

Show it:

1 is a schematic longitudinal section through a multi-chamber

Diaphragm pump with star-shaped diaphragm chambers arranged around a camshaft,

2 shows an embodiment of a compressor of supercharger and single or multi-stage high-pressure compressor in membrane construction,

3 is a schematic overview of the structure and the division of the membrane chambers in a compressor with single-stage supercharger and single-stage high-pressure compressor,

4 shows an exemplary embodiment with two-stage supercharger and single-stage high-pressure compressor,

5 shows an exemplary embodiment with three-stage supercharger and single-stage high-pressure compressor,

6 is a schematic representation of the camshaft in a single-stage supercharger, Fig. 7 is a view of the camshaft in a two-stage supercharger and

Fig. 8 is a view of the camshaft in a three-stage supercharger.

1 shows a diaphragm chamber pump 50 is shown schematically. In a housing 51, a camshaft 52 is mounted, which controls a plurality of star-shaped arranged around the camshaft diaphragm pump chambers 53. Each diaphragm pumping chamber 53 is defined by a flexible membrane 54 which is movable between two end positions. The diaphragm pump chamber 53 has an inlet line 64 with a check valve 55 and an outlet line 66 with a check valve 57. Gas is drawn in through the inlet line 64, and the compressed gas is expelled through the outlet line 66.

The movement of the membrane 54 is effected by a liquid cushion 58 which is contained in a cylinder 59 in which a piston 60 is movable. A spring 61 pushes the piston 60 against a ball bearing 62 which sits on the camshaft 52 and forms an eccentric for driving the piston. The piston 60 performs a linear movement in the cylinder 59, whereby the membrane 54 is moved via the Flussigkeitspolster 58 between their end positions.

In Figure 1, in addition to the ball bearing 62 further ball bearings on the camshaft 52 are shown. These serve to actuate the remaining diaphragm chambers, which are arranged in a star shape around the camshaft.

The Flussigkeitspolster 58 is supplied by a (not shown) pumping device with liquid or filled, which is also driven by the camshaft. FIG. 2 shows a compressor which consists of a supercharger VV and a high-pressure compressor HD. The supercharger consists of the multiple diaphragm compressor shown in FIG. It has four diaphragm pump chambers 11, 12, 13, 14, which are controlled by the same camshaft. The Auslassleitungen the diaphragm pump chambers are shown in Figure 2 They are connected to a collector 70, which leads to a diaphragm pump chamber HDL of the high-pressure compressor HD. The high-pressure compressor is also designed here as a camshaft-controlled diaphragm pump, wherein the remaining diaphragm pump chambers can be used as further stages of the high-pressure compressor or for other purposes.

In the supercharger VV all diaphragm pump chambers 11-14 are synchronously and in phase controlled. This means that all chambers suck in at the same time and eject the compressed gas in phase. Likewise, supercharger VV and high-pressure compressor HD are synchronized with each other, wherein the chamber HDL, which receives the compressed gas of the supercharger VV, is driven in phase opposition to the supercharger. In other words, when the supercharger discharges gas, the chamber HD1 must be in the position for receiving gas.

In the present embodiment, it is assumed that the supercharger has a compression ratio of π = 4. This means that all of the gas taken up by the supercharger in the supercharger is compressed to one quarter of its volume. On the other hand, since the volumes of four chambers are merged, resulting in the compressed state, the gas volume which corresponds approximately to the volume of one of the chambers of the supercharger. Therefore, the gas accommodating chamber HDL of the high-pressure compressor has approximately the same volume as one of the chambers of the supercharger, Figure 3 shows the structure of a single-stage supercharger with four diaphragm chambers, each having a pressure ratio of π = 4 and a discharge pressure p _A = 4 bar. The first digit in the schematic diaphragm chambers refers to the compressor stage, with the second digit is the Anzah! the membrane chambers numbered consecutively in the assigned stage. HDl designates the first stage of the downstream high-pressure compressor whose dimensions are identical to the individual diaphragm chambers of the predverdester.

Figure 4 shows the corresponding structure of a two-stage supercharger for a pressure ratio of π = 3 and a discharge pressure of p _A = 9 bar, with a total of twelve membrane chambers are used in the supercharger. Finally, the structure for a three-stage supercharger in membrane construction is shown in FIG. Here, a pressure ratio of π = 2 was selected, whereby in the third stage of the supercharger, a discharge pressure p _A = 8 bar is achieved with a total of fourteen membrane chambers.

In the Ausfbehrungsbeispie! of FIG. 3, the supercharger VV consists of a single stage Si with n = 4 chambers, the compression ratio being π-4. In the embodiment of FIG. 4, the predverdester VV consists of two stages S _x , S ₂ , each stage having n = 3 chambers, which are combined to form a group Gi - G ₃ . In the Ausführungsbeispie! of Figure 5, the supercharger VV of three stages Si, S ₂ , S ₃ , wherein in the first stage S ₁ four groups of chambers are formed and each group consists of n = 2 chambers. The compression ratio π is also 2. Also in the second stage two chambers are combined into one group; likewise in the third stage S ₃ . FIG. 6 shows the cross section and the view of the camshaft for a single-stage supercharger. Due to the eccentric shape of the camshaft, which extends over a range of 0 ° to 180 °, as can be seen from the cross section, the individual membranes are driven in the diaphragm chambers of the supercharger during half a revolution of the camshaft. The operated in the two-stroke diaphragm chambers suck in the first Fourth! until the top dead center at 90 °, the gas and compress it to then initiate the Ausschieben in the second quarter, which is completed at a cam angle of 180 °. As can be seen from the view flows in a single-stage supercharger with four diaphragm chambers, the entire gas volume in the first stage of the downstream high-pressure compressor. In the view, the first digit in the schematic eccentric of the cam period refers to the compressor stage in the supercharger, the second digit indicates the serial number of the diaphragm combs present in the relevant compressor stage.

FIG. 7 shows the cross section and the view of the camshaft using the example of a two-stage supercharger. However, in the first stage, the intake and compression of the gas starts at a camshaft position of 180 °, the top dead center is at a cam angle! of 270 ° and the pushing out into the second stage of the supercharger is completed at a cam angle of 0 °. The timing of the suction of the compression and the expulsion of the gas in the first stage of the high-pressure compressor nachgeschaiteten then takes place in the second stage as in the single-stage supercharger,

FIG. 8 shows the sequence of the control of the membranes in the membrane chambers by a camshaft for a three-stage supercharger with a low step pressure ratio of π = 2 in cross section and in the view. Of the

The first stage compression operation begins at a cam angle position of 0 °, becomes at top dead center at a cam angle of 90 ° completed, followed by the Ausschiebevorgang followed in the second compressor stage, which is completed at a cam angle of 180 °, the second compressor stage has its top dead center with a cam angle! of 270 °, followed by the Ausschiebevorgang in the third compressor stage up to a cam angle of 0 °. This in turn has its top dead center at a cam angle of 90 ° and ends with the subsequent expulsion of the gas flow from the two diaphragm chambers of the first stage of the supercharger in the first stage of a high-speed downstream high-pressure compressor. This process is completed at a cam angle of 180 °.

The gas forces to be controlled by the camshaft designed as an eccentric are balanced in their mass moment of inertia only in the two-stage design of the supercharger (FIG. 7). This means that only with an even number of compressor stages, the mass moment of inertia caused by the gas forces must be compensated. With an odd number of stages (FIGS. 6 and 8), the gas forces of one stage, which cause the mass moment of inertia not to be compensated, are compensated by a revolving counterweight on the camshaft.

Claims

claims

1. Multi-stage compressor with a high-pressure compressor (HD), which has at least one periodically driven diaphragm pump chamber (HDI),

characterized,

in that the high-pressure compressor (HD) is preceded by a precompressor (VV) which has at least one precompressor stage (S ₁ -S ₃ ), each precombustor stage containing a plurality of chambers (11-14) belonging to at least one group (Gi - G ₄ ) are summarized, and

that the chambers of a group are driven together and synchronously.

2. Multi-stage compressor according to claim 1, characterized in that the number (n) of the chambers of a group (Gi - G ₄ ) of the supercharger (VV) is substantially equal to the compression ratio (π) of this stage.

3. Multi-stage compressor according to claim 1 or 2, characterized in that the supercharger (VV) contains at least two Vorverdichterstufen (Si - S ₃ ), each chamber of the second Vorverdichterstufe (S2) of a group (G ₁ - G ₄ ) of Chambers of the first Vorverdichterstufe (Si) is fed.

4. Multi-stage compressor according to claim 3, characterized in that a third Vorverdichterstufe (S ₃ ) is provided, in which each chamber of a group of chambers of the second precompressor stage (S ₂ ) is fed,

5. Multi-stage compressor according to one of claims 1 - 4, characterized in that the chambers of one or more synchronized with each other camshaft (52) are driven and that at half a revolution of a camshaft between 0 ° and 180 ° after the two-stroke suction and Compressing the gas in the chambers (53) takes place, which is completed at top dead center at a cam angle of 90 ° and followed by a pushing out of the gas to a cam angle of 180 ° in the following stage.

6. Multi-stage compressor according to one of claims 1-5, characterized in that the compression of the gas in a plurality of chambers in one stage of the supercharger (VV) takes place synchronously in time and at the end of the compression, the gas also synchronously in time to two or more chambers following stage of the supercharger is delivered.

7. Multi-stage compressor according to one of claims 1-6, characterized in that the emerging from two or more chambers of the last stage of the supercharger gas is introduced at the end of the compression stroke in the first stage of a high pressure compressor (HD).

8. Multi-stage compressor according to one of claims 1-7, characterized in that the dimensions of the diaphragm chambers (53) of the supercharger (VV) are designed so that membranes (52) of the same diameter for different sizes of Membranverdϊchters, the one area of covering multiple pressure boosting and gas production.

9. Multi-stage compressor according to one of claims 1 - 8, characterized in that in an even-numbered stages! of the supercharger (VV) is compensated by the moment of inertia caused by the gas forces.

10. Multi-stage compressor according to one of claims 1-9, characterized in that at an odd-numbered Stufenzahi the supercharger (VV) caused by the gas forces of a stage and unbalanced mass moment of inertia is compensated by a rotating counterweight on the camshaft.