EP2182305A1 - Methode zur Regelung der Verteilung des Schmieröls in einer Verdichtereinheit und Verdichtereinheit - Google Patents

Methode zur Regelung der Verteilung des Schmieröls in einer Verdichtereinheit und Verdichtereinheit Download PDF

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Publication number
EP2182305A1
EP2182305A1 EP08425703A EP08425703A EP2182305A1 EP 2182305 A1 EP2182305 A1 EP 2182305A1 EP 08425703 A EP08425703 A EP 08425703A EP 08425703 A EP08425703 A EP 08425703A EP 2182305 A1 EP2182305 A1 EP 2182305A1
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EP
European Patent Office
Prior art keywords
compression
oil
lubricating oil
compression stage
compressor
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP08425703A
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English (en)
French (fr)
Inventor
Andrea Verondini
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Zanotti SpA
Original Assignee
Zanotti SpA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Zanotti SpA filed Critical Zanotti SpA
Priority to EP08425703A priority Critical patent/EP2182305A1/de
Publication of EP2182305A1 publication Critical patent/EP2182305A1/de
Withdrawn legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B1/00—Compression machines, plants or systems with non-reversible cycle
    • F25B1/10—Compression machines, plants or systems with non-reversible cycle with multi-stage compression
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B31/00—Compressor arrangements
    • F25B31/002—Lubrication
    • F25B31/004—Lubrication oil recirculating arrangements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/07—Details of compressors or related parts
    • F25B2400/075—Details of compressors or related parts with parallel compressors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/03—Oil level

Definitions

  • the present invention refers to a method for controlling the distribution of lubricating oil in a compression unit, said unit having a preferred, although not exclusive, use in refrigerating units.
  • the invention also refers to a compression unit for carrying out such a method.
  • the level exceeds the predetermined maximum value, there can be so-called flooding of the oil sump, in which lubricating oil enters into the cylinders in an amount above that foreseen by the design conditions and it can therefore, due to its low compressibility, cause damage like breaking of the valves and/or of the connecting rods.
  • the lubricating oil tends to mix with the coolant fluid subjected to compression.
  • the transportation of lubricating oil by the coolant fluid essentially proportional to the mass flow rate of the coolant fluid, on the one hand causes the level of the lubricating oil in the oil sump of the compressor to decrease, and on the other hand it causes the volumetric efficiency of a predetermined mass of coolant fluid to decrease, since the lubricating oil mixed in it does not produce a refrigerating effect.
  • the compression units used in refrigerating units often comprise many compression stages connected in series, each of which comprises one or more compressors. This makes it possible to respond with greater flexibility to variations in the refrigerating load and thus in the flow rate of coolant fluid that must be treated by the compression unit.
  • an intermediate cooling of the coolant fluid is arranged between the compression stages, through which, for the same compression ratio, it is possible to lower the temperature of the coolant fluid at the discharge of the compression unit.
  • the known methods for controlling the distribution of the lubricating oil in compression units with many compression stages substantially follow what is done in the case in units with a single compressor.
  • a separation device of the lubricating oil is arranged downstream of each compression stage and the lubricating oil separated through each separation device is sent to the respective compression stage.
  • a single separation device of the lubricating oil is used downstream of the compression unit and the lubricating oil separated through this separation device is sent in parallel to all of the compression stages of the compression unit.
  • the aforementioned methods do not ensure effective control of the distribution of the lubricating oil in the compression unit and in particular they do not provide a sufficient safeguard against possible flooding of the oil sumps of the compressors of the high-pressure stages. Such flooding is in practice avoided through periodic inspection of the compressors and possible manual bleeding of the excess lubricating oil from the oil sumps.
  • the technical problem forming the basis of the present invention is to provide a method for controlling the distribution of lubricating oil in a compression unit and a compression unit for carrying out such a method, through which the level of lubricating oil in the oil sumps of the compressors can be kept within an admissible range for the correct operation of the compressors themselves - avoiding, in particular, flooding of the oil sumps -, irrespective of the operating conditions of the compression unit and without the need for manual interventions from the outside.
  • the present invention therefore concerns a method for controlling the distribution of the lubricating oil in a compression unit according to claim 1 and a compression unit suitable for carrying out such a method according to claim 7.
  • Preferred characteristics of the method and of the compression unit are indicated in the respective dependent claims.
  • the invention concerns a method for controlling the distribution of lubricating oil in a compression unit comprising at least one first and a second compression stage, wherein said first and second compression stage respectively comprise at least one compressor provided with an oil sump for the lubricating oil and wherein the second compression stage is connected in series to the first compression stage, said method comprising the steps of:
  • the method of the invention advantageously makes it possible to effectively control the distribution of the lubricating oil in the compression unit in any operating condition thanks to the fact that lubricating oil is picked up from one compression stage and fed to the immediately preceding stage, i.e. the very compression stage from which the compression stage in which the pick-up is carried out receives lubricating oil transported together with the operative fluid, in particular a coolant fluid.
  • This makes it possible to simultaneously avoid both the occurrence of flooding of the oil sumps in the final (high-pressure) compression stages, and the occurrence of conditions of absence or low level of the lubricating oil in the initial (low-pressure) compression stages.
  • the second compression stage comprises a plurality of compressors connected together in parallel and the method of the invention comprises:
  • the step of placing the oil sumps in fluid communication comprises equalizing the pressures present in them.
  • the method of the invention also comprises the step of:
  • the pick-up of the lubricating oil from the second compression stage and the feeding to the first compression stage can in this way be advantageously carried out automatically, based upon an easily detectable magnitude that can be used to control the opening/closing of induction valves of the lubricating oil in the oil sump of the at least one compressor of the first compression stage.
  • the method of the invention also comprises the steps of:
  • the method of the invention also comprises the step of:
  • the feeding of the separated lubricating oil can be carried out automatically, based upon an easily detectable magnitude that can be used to control the opening/closing of induction valves of the lubricating oil of said oil sump.
  • the invention concerns a compression unit comprising at least one first and a second compression stage, wherein said first and second compression stage respectively comprise at least one compressor having an oil sump for lubricating oil and said second compression stage is connected in series to the first compression stage, characterised in that it comprises at least one duct extending between an outlet opening in the oil sump of the at least one compressor of said second compression stage and an inlet opening in the oil sump of the at least one compressor of said first compression stage, said at least one duct being suitable for placing said oil sumps in direct fluid communication.
  • Such a compression unit allows the method of the invention described above to be carried out and therefore allows all of the advantages in terms of the possibility of controlling the distribution of the lubricating oil in the compression unit to be obtained.
  • thanks to the aforementioned characteristics it is possible to keep a correct level of lubricating oil in the oil sumps of the compressor in any operating condition of the compression unit in a simple way and without the need for interventions from the outside.
  • second compression stage comprises a plurality of compressors connected together in parallel and having respective oil sumps for the lubricating oil in fluid communication with each other through a common manifold, and said at least one duct extends between an outlet opening in the common manifold and an inlet opening in the oil sump of the at least one compressor of said first compression stage.
  • the common manifold is preferably associated with the oil sumps in a position such as to allow the pressures present in them to be equalised.
  • the compression unit of the invention comprises heat exchange means arranged between the first and the second compression stage to cool an operative fluid compressed through the compression unit during the compression.
  • Such heat exchange means advantageously allow a compression with intermediate cooling to be carried out.
  • the compression unit comprises a separation device suitable for at least partially separating the lubricating oil from an operative fluid compressed through the compression unit, said separation device comprising an oil separator arranged downstream of the second compression stage.
  • the separation device is in fluid communication with the oil sump of the at least one compressor of the second compression unit.
  • the invention concerns a refrigeration unit comprising a compression unit with the characteristics described above.
  • the compression unit 1 also comprises a separation device 3 suitable for separating the lubricating oil from a compressed fluid with which it has mixed during the compression and is therefore transported away from the compressors 11, 21.
  • the separation device 3 preferably comprises at least one oil separator 30 arranged downstream of the second compression stage 20.
  • the separation device 3 is in fluid communication with the oil sumps 210 of the compressors 21 to feed the separated lubricating oil to them.
  • the flow of lubricating oil from the separation device 3 to the oil sumps 210 is controlled by the induction valves 211, and therefore by the level of lubricating oil in the oil sumps 211 and in the common manifold 22. When the induction valves 211 are open, the flow of lubricating oil occurs by pressure difference.
  • the separation device 3 comprises a collection tank 31 for the separated lubricating oil integrated in the oil separator 30.
  • the pressure difference that makes the separated lubricating oil flow out from the collection tank 31 to the oil sumps 210 is substantially equal to the increase in pressure determined in the fluid compressed through the second compression stage 20.
  • the separation device 3 comprises a collection tank 31 for the separated lubricating oil outside of the oil separator 30.
  • a differential pressure valve 32 is preferably arranged to keep the collection tank 31 at a pressure slightly above that in the oil sumps 210 and in the common manifold 22.
  • the dotted and dashed lines in figure 2 indicate the connections of the differential pressure valve 32 for detecting the pressures.
  • each oil sump 210 is provided with an inlet opening with respective induction valve 211 and the separation device 3 is in fluid communication with each oil sump 210.
  • This constructive solution has a substantial reliability with respect to malfunctions of the induction valves 211 or of the associated actuators and level sensors, since it ensures that in the case of malfunction of one of such induction valves 211 the separated lubricating oil can in any case be fed to all of the oil sumps 210, possibly subject to passage through the common manifold 22.
  • the oil sumps 210 of the compressors 21 have no inlet openings and relative induction valves to enter lubricating oil from the outside and a single inlet opening is foreseen with relative induction valve for the lubricating oil at the common manifold 22.
  • the compression unit 1 is preferably a so-called compound compression unit, i.e. it also comprises heat exchange means 4 arranged between the first compression stage 10 and the second compression stage 20, to make compression with intermediate cooling possible.
  • the heat exchange means 4 are of the conventional type and their characteristics and performances can be easily selected by a man skilled in the art based upon the specific application requirements of the compression unit 1. A preferred embodiment of the heat exchange means 4 shall be described hereafter with reference to the use of the compression unit 1 in a refrigeration unit ( figure 4 ).
  • Figure 4 illustrates a preferred, although not exclusive, use of the compression unit 1 in a refrigeration unit 100.
  • the block diagram shown in such a figure refers, as an example, to a typical refrigerating unit for the conservation of fresh and frozen foods in commercial activities.
  • the refrigeration unit 100 essentially comprises a condensation unit 5 to condense the compressed coolant fluid, a collection tank 6 for the condensed coolant fluid, a plurality of units 7 for the conservation of fresh foods connected together in parallel and a plurality of units 8 for the conservation of frozen foods.
  • the units 7 and 8 can for example be refrigerated cases for conserving and displaying the aforementioned foods.
  • Each unit 7 and 8 comprises a respective expansion element (not illustrated explicitly and in any case of the conventional type), suitable for laminating a certain mass flow rate of coolant fluid taking it to the desired pressure for evaporation in the respective unit 7 or 8.
  • the coolant fluid evaporated in the units 7 for the conservation of fresh products goes back in vapour state to the compression unit 1 upstream of the second compression stage 20 and the heat exchange means 4, whereas the coolant fluid evaporated in the units 8 for the conservation of frozen foods goes back in vapour state to the compression unit at the intake of the first compression stage 10.
  • Part of the condensed coolant fluid is also sent to the heat exchange means 4 of the compression unit 1 to carry out the intermediate cooling between the first and the second compression stage 10, 20.
  • the heat exchange means 4 are suitable for carrying out both the intermediate cooling of the coolant fluid in the compression step, and a sub-cooling of the condensed coolant fluid intended to feed the units 8 for the conservation of frozen foods. They comprise a tank 43, preferably consisting of a so-called anti-liquid bottle, provided on the inside with one or more ducts 44 for the passage of the condensed coolant fluid.
  • the intermediate cooling is carried out through controlled mixing in the tank 43 between coolant fluid in the compression step and another coolant fluid in vapour state, obtained through lamination of a flow rate of the condensed coolant fluid.
  • the pick-up of the condensed refrigerated fluid from the collection tank 6 is controlled through an on-off valve 41, for example a solenoid valve.
  • the dosaging and the lamination to take the condensed coolant fluid to the desired pressure and temperature conditions for the intermediate cooling are preferably carried out through a thermal expansion valve 42 with fixed point temperature adjustment, which detects the temperature of the coolant fluid at the intake of the second compression stage 20.
  • the sub-cooling is carried out by making condensed coolant fluid pass into the duct(s) 44, and then carrying out a heat exchange with the coolant fluid in vapour state that is located in the anti-liquid bottle 43, before sending it to the units 8 for the conservation of frozen foods.
  • the aforementioned unbalance of distribution of the lubricating oil can be controlled in a simple manner, irrespective of the operating conditions of the compression unit 1 and without the need for interventions from the outside through the method of the invention for controlling the distribution of lubricating oil in compression units.
  • a preferred embodiment of such a method shall now be described with particular reference to the embodiment of the compression unit 1 ' shown in figure 1 .
  • the method essentially foresees the steps of picking up lubricating oil from the oil sumps 210 of the compressors 21 of the second compression stage 20, and of feeding the picked up lubricating oil to the oil sumps 110 of the compressors 11 of the first compression stage 10. This is obtained by means of the duct 2 described above.
  • the method also comprises the step of placing the oil sumps 211 of the compressors 21 in fluid communication, preferably so as to obtain an equalisation of the pressures in the oil sumps. This is obtained through the common manifold 22 described above. In this case, the pick-up of the lubricating oil preferably takes place at the common manifold 22.
  • the method also comprises the step of detecting the level of lubricating oil in the oil sumps 110 of the compressors 21 of the first compression stage 10, and foresees carrying out the aforementioned step of feeding the lubricating oil picked up from the second compression stage 20 when the level detected in at least one of the oil sumps 110 is below a predetermined level. This is carried out automatically through the induction valves 111 and the associated level sensors described above.
  • the method also comprises the steps of at least partially separating the lubricating oil from the compressed fluid downstream of the second compression stage 20, and of feeding the separated lubricating oil to the oil sumps 210 of the compressors 21 of the second stage 20. Also in this case, there is preferably a step of detecting the level of the lubricating oil in the oil sumps 210, i.e. in the common manifold 22 when provided, and the step of feeding the separated lubricating oil is carried out when the detected level is below a predetermined level. This is carried out automatically through the induction valves 211 and the associated level sensors described above.
  • the feeding of the separated lubricating oil in the second compression stage can take place at the common manifold 22 instead of at the oil sumps 210.
  • a compression unit 1 comprising two compression stages.
  • the oil sumps of the compressors of a generic intermediate compression stage receive lubricating oil from the oil sumps (or, preferably, from a common manifold associated with them) of the compressors of the compression stage immediately downstream and, in turn, they feed lubricating oil (preferably from a respective common manifold) to the oil sumps of the compressors of the compression stage immediately upstream.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Applications Or Details Of Rotary Compressors (AREA)
EP08425703A 2008-10-31 2008-10-31 Methode zur Regelung der Verteilung des Schmieröls in einer Verdichtereinheit und Verdichtereinheit Withdrawn EP2182305A1 (de)

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EP08425703A EP2182305A1 (de) 2008-10-31 2008-10-31 Methode zur Regelung der Verteilung des Schmieröls in einer Verdichtereinheit und Verdichtereinheit

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EP08425703A EP2182305A1 (de) 2008-10-31 2008-10-31 Methode zur Regelung der Verteilung des Schmieröls in einer Verdichtereinheit und Verdichtereinheit

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EP2182305A1 true EP2182305A1 (de) 2010-05-05

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012095186A1 (en) * 2011-01-14 2012-07-19 Carrier Corporation Refrigeration system and method for operating a refrigeration system
JP2014145556A (ja) * 2013-01-30 2014-08-14 Mitsubishi Heavy Ind Ltd ２段圧縮装置およびそれを用いた冷凍・空調装置
DE102013014543A1 (de) * 2013-09-03 2015-03-05 Stiebel Eltron Gmbh & Co. Kg Wärmepumpenvorrichtung
CN104567063A (zh) * 2014-12-31 2015-04-29 江苏兆胜空调有限公司 一种船用混合型变频低温速冻装置
WO2017220702A1 (en) * 2016-06-24 2017-12-28 Danfoss A/S A method for controlling pressure and oil level in an oil receiver of a vapour compressions system

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3500962A (en) * 1969-05-01 1970-03-17 Vilter Manufacturing Corp Lubrication system for compressors
JPH02133758A (ja) * 1988-11-15 1990-05-22 Ebara Corp 冷凍機
JPH04371759A (ja) * 1991-06-21 1992-12-24 Hitachi Ltd 二段圧縮二段膨張式の冷凍サイクル
JPH07301465A (ja) * 1994-05-02 1995-11-14 Mitsubishi Heavy Ind Ltd 二段圧縮式冷凍装置
EP1795832A1 (de) * 2004-09-02 2007-06-13 Daikin Industries, Ltd. Kühlvorrichtung

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3500962A (en) * 1969-05-01 1970-03-17 Vilter Manufacturing Corp Lubrication system for compressors
JPH02133758A (ja) * 1988-11-15 1990-05-22 Ebara Corp 冷凍機
JPH04371759A (ja) * 1991-06-21 1992-12-24 Hitachi Ltd 二段圧縮二段膨張式の冷凍サイクル
JPH07301465A (ja) * 1994-05-02 1995-11-14 Mitsubishi Heavy Ind Ltd 二段圧縮式冷凍装置
EP1795832A1 (de) * 2004-09-02 2007-06-13 Daikin Industries, Ltd. Kühlvorrichtung

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012095186A1 (en) * 2011-01-14 2012-07-19 Carrier Corporation Refrigeration system and method for operating a refrigeration system
CN103282729A (zh) * 2011-01-14 2013-09-04 开利公司 制冷系统和用于操作制冷系统的方法
CN103282729B (zh) * 2011-01-14 2015-09-30 开利公司 制冷系统和用于操作制冷系统的方法
JP2014145556A (ja) * 2013-01-30 2014-08-14 Mitsubishi Heavy Ind Ltd ２段圧縮装置およびそれを用いた冷凍・空調装置
EP2762803A3 (de) * 2013-01-30 2015-11-18 Mitsubishi Heavy Industries, Ltd. Zweischrittkompressionsvorrichtung und Kühl-/Klimaanlage damit
DE102013014543A1 (de) * 2013-09-03 2015-03-05 Stiebel Eltron Gmbh & Co. Kg Wärmepumpenvorrichtung
CN104567063A (zh) * 2014-12-31 2015-04-29 江苏兆胜空调有限公司 一种船用混合型变频低温速冻装置
WO2017220702A1 (en) * 2016-06-24 2017-12-28 Danfoss A/S A method for controlling pressure and oil level in an oil receiver of a vapour compressions system
CN109312969A (zh) * 2016-06-24 2019-02-05 丹佛斯有限公司 一种用于控制蒸气压缩系统的油接收器中的压力和油位的方法

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