CN102834618A

CN102834618A - Lubrication of screw machines

Info

Publication number: CN102834618A
Application number: CN2011800186541A
Authority: CN
Inventors: I·K·史密斯; N·R·斯托希克
Original assignee: City University of London
Current assignee: City University of London
Priority date: 2010-02-12
Filing date: 2011-02-14
Publication date: 2012-12-19
Anticipated expiration: 2031-02-14
Also published as: GB2477777A; CN102834618B; GB2477777B; WO2011098835A3; JP5964245B2; WO2011098835A2; KR20120140659A; US20130052072A1; GB201002411D0; EP2534339A2; JP2013519820A

Abstract

A screw machine for use with a working fluid with a liquid phase present comprises rotors having meshed, lubricated helical formations. The rotors have an 'N' profile as disclosed in WO 97/43550. In use, lubrication of the helical formations of the rotors and optionally of the rotor bearings is achieved substantially exclusively with the liquid phase of the working fluid.

Description

Lubricating of screw rod machine

Technical field

The present invention relates to a kind of lubricated like screw rod machines (screw machines) such as screw rod expanders, it for example can use that steam generates electricity as working fluid.

Background technique

The positive displacement expander is applied in the generating just more and more widely.One of the most successful Stirling engine is the multiscrew machine, and its most frequently used mode of execution is a dual-screw-stem machine.This machine is open in patent GB1197432, GB1503488 and the GB2092676 of Svenska Rotor Maskiner (SRM) company.

The screw rod machine can use as compressor or expander.Topmost theory of the present invention relates to this screw rod machine of two types, but the present invention is particularly useful in the expander field.Therefore this specification relates generally to as the screw rod machine of expander and the screw rod machine that combines to be used as expander and describes the present invention.In this manual, the screw rod machine as expander will abbreviate the screw rod expander as.

The crucial part that the screw rod expander is superior to turbine expander is to operate wet working fluid (that is the fluid that, comprises gas phase and liquid phase) and the risk that almost do not have to damage.This is because the order of magnitude of the liquid speed in the screw rod machine is less than about the order of magnitude of the liquid speed that in turbo machine, runs into usually greatly.Therefore, the screw rod expander can allow the fluid of any formation from the neat liquid to the dry steam, between these phase places, keeps thermodynamical equilibrium simultaneously.On the contrary, if in working fluid, be entrained with the liquid phase of considerable part, then blade erosion takes place in turbine expander easily.

The screw rod expander comprises housing, and it has at least two overlapping but disjoint holes.These pore volumes are received the rotor of meshing spiral shape band leaf separately, their counterrotatings in the housing that is fixed.Housing surrounds rotor fully to cooperate extremely closely.The central longitudinal axis in these holes is paired coplane and parallel usually.Convex rotor (or " main rotor ") and recessed rotor (or " gate rotor ") are installed to the housing on the bearing, be used for around its axis rotation separately, each in these axis all with housing in a plurality of axially bored lines in an axes overlap.

Rotor is usually by processing such as metals such as low carbon steel, but they can be processed by high speed steel.Rotor can also be processed by stupalith.Usually, if be made of metal, then they still substitutingly, can be ground or cast by machining them.

Each rotor all has spiral faceted pebble (helical land), the spiral slot engagement between the faceted pebble of itself and at least one other rotor.The rotor of engagement forms one or more pairs of spiral gears effectively, and its salient angle (lobe) plays the effect of tooth simultaneously.Along cross-sectional view, this convex rotor or each convex rotor all have corresponding to faceted pebble and from the outside one group of salient angle protruding of its pitch circle.Likewise along cross-sectional view, this recessed rotor or each recessed rotor all have from its pitch circle and extend internally and corresponding to one group of recess of the groove of recessed rotor.The faceted pebble of convex rotor and the quantity of groove are different from the quantity of the faceted pebble and the groove of recessed rotor.

The example of the existing technology of rotor profile arrives shown in Fig. 2 (d) to 1 (d) and Fig. 2 (a) at Fig. 1 of accompanying drawing (a), and will describe in more detail after a while.

The working principle of screw rod expander is based on three dimensional volume and changes.Space between any two continuous salient angles of each rotor and the individual working of housing formation on every side chamber.The rotation that the volume of this chamber causes along with the transfer of the Line of contact between two rotors and changing.Whole length between salient angle is because of the engagement between rotor contact when accessible, and the volume of this chamber is maximum.On the contrary, when between end surfaces place rotor, having engagement contact completely, the volume of this chamber is minimum, almost near 0 value.

Fluid to be expanded gets into the screw rod expander through the opening of entry port (mainly being positioned at the frontal plane of housing) or formation high pressure.Therefore, in the chamber that the fluid filled that is allowed to limits between salient angle.When rotation carry out and rotor between Line of contact when returning, the volume that obtains in each chamber increases.When entry port is cut off, fill or the access procedure termination, and further rotation will cause fluid when moving downstream through the screw rod expander, to expand.

Low-pressure port or discharge port in the housing when convex rotor salient angle and recessed rotor lobes begin to mesh once more, are exposed in further downstream.The volume of the fluid of between further rotation compression salient angle and housing, holding back, this port is further opened.This makes fluid to discharge through discharge port near constant compression force.This process last till the volume of holding back be reduced to be almost 0 and whole fluids of holding back between the salient angle basically all discharge.

Then, this process is all repeated in each chamber.Therefore, according to the quantity of the salient angle in convex rotor and the recessed rotor, and then, in each rotation, realize continuous filling, expansion and discharge process according to the quantity of the chamber between these salient angles.

When rotor rotated, the engagement action of the salient angle engagement action with spiral gear in essence was identical.Yet in addition, the shape of salient angle must make that at any contact position potted line is formed between the rotor and between rotor and housing, between the chamber in succession internal leak takes place so that prevent.Further requirement is that the chamber between the salient angle should be big as far as possible, thereby makes the displacement of fluid maximization of each rotation.In addition, the contact force between the rotor should be lower, thereby make the internal friction loss minimize and make minimise wear.

When manufacturing required to be defined between the rotor and between rotor and housing, will have less clearance, rotor profile was to confirm the most important characteristic of the efficient of flow velocity and screw rod expander.A plurality of rotor profile have been tested a lot of years, and have changed successfully degree.

Shown in Fig. 1 (a), what screw rod expander the earliest used is very simple symmetry properties rotor profile.Along cross-sectional view, convex rotor 10 comprises that the center of its radius all is positioned on the pitch circle 14 around pitch circle equal angles a plurality of part circle (part-circular) salient angles 12 at interval.The profile of recessed rotor 16 becomes mirror image through one group of partly round recess 18 of equity with it with simple mode.Have very large pore zone such as such symmetry properties rotor profile, this can produce very big internal leak.This with the symmetry properties rotor profile get rid of comprise high-pressure ratio or even the application of medium pressure ratio outside.

In order to address this problem, SRM introduces its " A " shape profile, and it is disclosing shown in Fig. 1 (b) and in aforesaid B. P. GB1197432, GB1503488 and GB2092676 in a variety of forms.Therefore this " A " shape profile has significantly reduced internal leak and has made helical-lobe compressor obtain the efficient with the identical magnitude of reciprocator.Cyclon profile shown in Fig. 1 (c) has further reduced seepage, but this is to be cost with the salient angle that weakens recessed rotor 16.This makes the recessed rotor 16 that is in high pressure differential have the risk of distortion, and makes them be difficult to make.Hyper profile shown in Fig. 1 (d) is attempted to overcome this defective through strengthening recessed rotor 16.

In all rotor profile of above existing technology, relatively moving between the rotor of engagement is the combination of rotation and slip.

With reference to this background, it is International Patent Application PCT/GB97/01333 disclosed " N " shape rotor profile of WO97/43550 that the claimant has developed publication number.The content of WO97/43550 is incorporated this paper into way of reference.In this specification, quoting of " N " shape rotor profile referred to described in the WO97/43550 profile with the invention that limits.

" N " shape rotor profile is characterised in that; When along cross-sectional view, at least salient angle to the profile of the profile of those parts of the outside of the pitch circle of convex rotor protrusion and the recess that extends to the inside of the pitch circle of recessed rotor at least through identical rack configurations generation.The latter is along a direction and crooked along the opposite direction around recessed rotor axis around male rotor axis, and the section of rack that produces the high pressure flank of rotor produces through the action of the rotor conjugation between the rotor.

Valuably, the part of tooth bar, preferably form that part of shape that is cycloid (cycloid) of the high pressure flank of rotor lobes.Substituting ground, this part can form the parabola of broad sense, for example ax+by ^q=1 form.

Usually, the bottom of the groove of convex rotor is in as " tooth root " portion and is positioned in the pitch circle, and extend beyond its pitch circle as " tooth top " portion at the tip of the faceted pebble of recessed rotor.Preferably, these tooth root portions and tooth also produce through rack configurations.

Main rotor (or convex rotor) 1 shown in the diagrammatic cross-sectional view of the dual-screw-stem machine of Fig. 2 (a) and gate rotor (or recessed rotor) 2 pitch circle P at them ₁, P ₂Go up center O around them ₁And O ₂Rotate through corresponding angle ψ and τ=Z ₁/ Z ₂ψ=ψ/i.

The quantity of the radius of pitch circle P and corresponding epitrochanterian faceted pebble and groove is proportional.

If segmental arc is defined as the arbitrary function of angular dimensions φ and is represented by subscript d on main rotor or gate rotor:

x _d=x _d(φ) (1)

y _d=y _d(φ) (2)

Then the segmental arc in another epitrochanterian correspondence is the function of φ and ψ:

x=x(φ，ψ)=-acos(ψ/i)+x _d?coskψ+y _dsinkψ (3)

y=y(φ，ψ)=asin(ψ/i)-x _d?sinkψ+y _dcoskψ (4)

ψ is the angle of rotation of main rotor, the point of contact that first segmental arc and second segmental arc have this angle of rotation.This angle satisfy Sakun in nineteen sixty at Vintovie kompressori, the conjugate condition of describing among the Mashgiz Leningrad:

(δx _d/δφ)(δy _d/δψ)-(δx _d/δψ)(δy _d/δφ)=0 (5)

This is the differential equation of all " d " envelope of curves lines (envelope).Its expansion is:

(δy _d/δx _d)((a/i)sinψ-ky _d)-(-(a/i)cosψ+kx _d)=0 (6)

This can be expressed as the quadratic equation of sin ψ.Though it can adopt analytic method to untie, because its mixing root, so suggestion adopts number to separate.In case decision, then ψ is inserted in (3) and (4) to obtain relative epitrochanterian conjugate curve.This step requirements definition is a given segmental arc only.Another segmental arc always obtains through general step.

Even the coordinate system of these equations is independent of rotor and defines, they also are effective.Therefore, can under not with reference to the situation of rotor, specify all " d " curves.This set can be expressed some curves with simple mathematical form more, and can simplify curve in addition and generate step.

Such special coordinates system is tooth bar (rotor of a unlimited radius) coordinate system (in Fig. 2 (b), representing with R), and it shows a unit of the tooth bar that is used to produce the rotor profile shown in Fig. 2 (a).Then, the segmental arc on the tooth bar is defined as the arbitrary function of parameter:

x _d=x _d(φ) (7)

y _d=y _d(φ) (8)

In epitrochanterian second segmental arc thus as the function of φ and ψ and derive

x=x(φ,ψ)=x _d?cosψ-(y _d-r _wψ)sinψ(9)

y=y(φ,ψ)+x _d?sinψ+(y _d-r _wψ)cosψ(10)

The angle of rotation of the rotor at the segmental arc protrusion place that the ψ representative is given, it defines point of contact.This angle satisfies condition (5), and it is:

(dy _d/dx _d)(r _wψ-y _d)-(r _w-x _d)=0 (11)

Then, explicit solution ψ is inserted into (9) and (10) to obtain epitrochanterian conjugation segmental arc.

Fig. 2 (c) shows the rack configurations of Fig. 2 (b) and the relation of the rotor shown in Fig. 2 (a), and shows the rotor of tooth bar and this tooth bar generation.Fig. 2 (d) with the mode of contrast show the rotor of existing technology on the profile of the rotor shown in the stacking chart 2 (c).

No matter where provide curve, it makes things convenient for form to be:

{ax}_{d}^{p} + {by}_{d}^{q} = 1 - - - (12)

It is " conventional circle " curve.For the situation of p=q=2 and a=b=1/r, it is round.Under a and the unequal situation of b, will obtain ellipse; The a of opposite sign and b will obtain hyperbola; Under the situation of p=1 and q=2, will obtain parabola.

Except defining the facility of all curves that provide through a coordinate system; Compare with the rotor coordinate system; Tooth bar forms two advantages is provided: a) compare with other rotor; The contact path that tooth bar profile representative is the shortest, it means from naming a person for a particular job of tooth bar and protrudes on the rotor and have no overlapping or other shortcoming; B) straight line on the tooth bar will protrude on the rotor as involute.

For the stomatal size on the high pressure side that minimizes rotor profile, this profile produces this their high pressure side of two rotor undercutting (undercut) by the conjugation action of two rotors usually.This practice is used widely: in patent GB 1197432, use the odd number point on main rotor and the gate rotor; In patent GB 2092676 and GB 2112460, use circle; In patent GB 2106186, use oval; And in patent EP 0166531, use parabola.Suitable undercutting can not directly obtain from tooth bar in advance.Can find, on the tooth bar of the conjugation action that can accurately substitute rotor, only have an analytic curve.Cycloid preferably, it carries out undercutting as the epicycloid on the main rotor and as the hypocycloid on the gate rotor.This is opposite with the generation undercutting that epicycloidal odd number point produced on two rotors.Such defective significantly reduces to be able to minimize through the gate rotor external diameter in the pitch circle that makes gate rotor usually.This reduces stomatal size, but has also reduced throughput.

Conjugation action is that an epitrochanterian point (the perhaps a plurality of points on the curve) cuts another epitrochanterian its process in (perhaps they) path during the rotation.If the same time, undercutting took place when having two or more common point of contact, this produces " depression (pocket) " in profile.When significant slip takes place, if less curved portion (perhaps point) produces long curved portion, then usually undercutting can take place.

" N " shape rotor profile has overcome this defective, produces because the high-voltage section of tooth bar is moved through the rotor conjugation of the suitable profile on this tooth bar of undercutting.This tooth bar is used for producing the profile that step forms main rotor and gate rotor through common tooth bar after a while.

Below describe in detail be designed for through the step that combines obtain to the effective simple rotor lobes shape of the profile family that produces of the tooth bar of compression of air, refrigeration agent commonly used and various procedures gas.This profile almost comprises all elements of the modern screw rotor profile that provides in the disclosed documents and materials, but it is characterized by additional trickle improvement and optimization provides safe basis.

The coordinate of summarizing all the main segmental arcs on the tooth bar here with respect to the tooth bar coordinate system.

The salient angle of this profile is divided into a plurality of segmental arcs.

Boundary between the profile segmental arc is represented by capitalization and each segmental arc is defined respectively, shown in Fig. 2 (c).

The A-B section is the conventional segmental arc of

type on p=0.43 and the q=1 hour rack.

The B-C section is the straight line on the tooth bar, p=q=1.

The C-D section is the arc section on the tooth bar, p=q=2, a=b.

The D-E section is the straight line on the tooth bar.

The E-F section is the arc section on the tooth bar, p=q=2, a=b.

The F-G section is a straight line.

The G-H section is segmental arc G ₂-H ₂Undercutting, when it is p=1 and q=0.75 on the main rotor

The conventional segmental arc of type.

H-A section on the tooth bar is segmental arc A ₁-H ₁Undercutting, it is p=1 on the gate rotor, during q=0.25

The general segmental arc of type.

At each bonding point A ... The H place, adjacent section has common tangent line.

The tooth bar coordinate is through obtaining with the reverse program of equation (7) to (11).

As a result, obtain tooth bar curve E-H-A, it is shown in Fig. 2 (c).

Fig. 2 (d) shows the main rotor 3 that produced by this tooth bar program and the profile of gate rotor 4, the known profile 5,6 of this profile and the respective rotor that produces according to patent GB 2092676 5/7 textural overlapping.

By same distance between the center and identical root diameter, the profile that tooth bar produces increases by 2.7% displacement, and the salient angle of recessed rotor is thicker and therefore firmer simultaneously.

In the modification of the tooth bar shown in Fig. 2 (c), GH section and HA section are by y=R _oCos τ-R _p, y=R _oSin τ-R _pThe continuous segment GHA of the cycloid of τ form forms, wherein R _OBe (and being its hole therefore) outer radius of main rotor, R _PIt is the pitch circle radius of this main rotor.

AB, BC, CD, DE, EF and FG section all are to be produced by above equation (12).For the AB section, a=b, p=0.43, q=1.For other section, a=b=1/r, and p=q=2.The value of p and q can change ± and 10%.For BC, DE and FG section, r is greater than the pitch circle radius of main rotor, and preferably infinitely great, makes each this section to be straight line.When p=q=2, CD and EF section are the arc sections of a=b curve.

" N " shape rotor profile of more than describing is based on the mathematical theory of gear.Therefore, different to the rotor profile that Fig. 1 (d) describes with reference to figure 1 (a) with before, relatively moving between the rotor is almost near pure rolling: the contact zones between the rotor are in very the position near its pitch circle.

" N " shape rotor profile is compared with other rotor profile has a lot of extra advantages, comprising: the transmission device of low moment of torsion, so the contact force between the rotor is less; Recessed rotor is firm; Displacement is big and cause the potted line of low seepage short.Generally speaking, its use has improved the heat-shielding performance of screw rod expander, and especially in the heat-shielding performance at lower end speed place, its situation than other rotor profile in the current use of record can improve 10%.

Common practise of the prior art is that lubricated if the helix structure of rotor does not have, then " regularly " gear of external engagement must be set to arrange the also relative movement of synchronous rotor.The transmission of the synchronous torque between the rotor comes into force via timing gear, so it has avoided the direct contact between the meshing spiral structure of rotor.Like this, it is not lubricated that timing gear allows the helix structure of rotor.

Substituting ground, outside timing gear can omit, and makes the synchronous meshing relation by them of rotor determine separately.This hints that inevitably the transmission from a rotor to the synchronous torque of another rotor is the meshing spiral structure via them.Under the sort of situation, the helix structure of rotor must be lubricated, and to avoid the hard contact between the rotor, the result causes wearing and tearing and possibly kill.

Start from the consideration to these substituting approach of the synchronous of rotor and their different lubricating requirement, the screw rod expander has two main types: " oil-filled " type and " not having oil " type.

The oil that carries in the oil-filled machine dependence working fluid lubricates the helix structure and the bearing thereof of rotor, and between the canned rotor and the gap between rotor and the housing on every side.But oil-filled machine needs the external shaft sealing does not need inner sealing, and it is simple aspect Machine Design.Therefore, its low cost of manufacture, and compact and efficient.

On the contrary, not having oily machine can not make oil mix with working fluid.Therefore, timing gear is set to avoid contact between the helix structure of rotor.Each timing gear rotates through a corresponding rotor, and those gears are in the external engagement of housing, and wherein they externally lubricate through oil.Therefore, " not having oil " refers to the inside of housing, but not entire machine.In order to prevent oil entering housing and to bring in the working fluid, need on each axle between housing and the gear, carry out inner sealing and external shaft sealing.The result is that it is obviously huger than oil-filled machine not have oily machine, and more much higher than the manufacture cost of oil-filled machine.Yet the rotor that does not have oily machine can rotate with higher speed, and does not have too much viscous resistance.Therefore, the flow that does not have each unit volume of oily machine is higher than oil-filled machine.

Oil-filled machine and no oily machine all need be used for the external heat exchanger of lubricant oil before the machine of packing into once more.In the application of expander, the purposes of heat exchanger is different in oil-filled machine and no oily machine.

Not having oily machine uses heat exchanger to come cold oil.In order to accomplish circulation, fuel tank, oil purifier and recycle pump all need make oil turn back to bearing and timing gear.On the contrary, it is oily from the working fluid of discharging, to remove that oil-filled machine needs the separator in expander downstream.Then, the oil of separation must be in pump by pressurization once more, and heat exchanger must be before oil turns back to the high voltage terminal of housing heated oils.This has been avoided making the working fluid that gets into housing to turn cold, otherwise this will reduce the efficient of expander.

These lubrication systems increase the overall cost of two types expander, but the cost that increases does not have the much bigger of oily expander than being used to.In fact, the overall cost of not having an oily expander usually on the order of magnitude greater than the cost of the oil-filled expander of the capacity of grade.

Except cost, do not have oil and oil-filled lubrication system and all have other defective.

The difficulty that the trial of the no oily expander of production has caused is that inner shaft seals the oil that can not fully isolate working fluid and lubricated timing gear.At working fluid is highly to be soluble under the situation of hydrocarbon or refrigeration agent of lubricant oil, and this problem is outstanding especially.

Under the situation of oil-filled expander, in fact can not after expanding, oil fully be separated from working fluid and remove.This causes oil in other part of system, to build up, thereby has produced operational issue.Certainly, in no oily expander, also have identical problem, its seal arrangement can not make oil and working fluid fully isolate.Yet it is more better than oil-filled expander in this respect usually not have oily expander.Therefore,, possibly need to adopt no oily expander, although it is bulky, complicacy and cost are higher for the responsive especially application of oil pollution.

As stated, the rotor of screw rod expander is installed to the housing on the bearing, in order to rotate around its corresponding axis.Can use various types of bearings.Certainly lubricating at this also is a problem.

Most screw rod machines use rolling body bearing to come support rotor.This allows bearing fit tolerance very little, so make between the rotor and rotor and housing between the gap that must keep minimize.Therefore this make internal leak minimize and thereby make maximizing efficiency.

Rolling body bearing comprises ball bearing and roller bearing.Their function is to keep rotating contact through one group of spherical ball on two surfaces separately or the cylindrical or conical roller of tack.If be provided with suitably, rolling body bearing can support radial load and axial load.No matter the main rolling motion between rolling element and the track that on them, moves how, the boundary film of oil must remain between those parts so that wearing and tearing and friction are heated minimizes.

Show when the liquid constituent of working fluid only comprises the dissolved oil of low density even claimant's publication number is International Patent Application PCT/GB2006/02148 of WO 2006/131759, also can lubricate the rolling body bearing in the screw rod expander.If this liquid constituent is fed to bearing, working fluid will evaporate because of friction heating, and will in bearing housing, stay enough oil and make the effectively required boundary film of running of bearing with supply.Yet; (this fluid for example is a steam when use is used for expansion fluid; Perhaps oil can not be dissolved in any other fluid in its liquid phase) the screw rod expander time, can not adopt the lubrication principle of patent WO2006/131759, and even not allow in working fluid, to exist the lubricant oil of trace.

The patent US 6217304 of Shaw has disclosed the helical-lobe compressor that is used for refrigeration plant, and this helical-lobe compressor can use the drop of bringing the liquid refrigerant in the vapor phase refrigerant into to seal, cool off and lubricated rotor in theory.If necessary, can the drop of liquid refrigerant be expelled in the refrigeration agent stream, it has the problem of negative consequence.Yet, the feasible program that patent US 6217304 does not provide this compressor how can be in working fluid not move under the situation of oil-containing.It only relates to the use of thermoplastic material or other suitable composite material of the convex rotor that makes that gap between the rotor is less.

Although not mentioned among the patent US 6217304, according to claimant's knowledge, in refrigeration agent, be not dissolved with or carry under a lot of oil conditions, refrigeration compressor is operation smoothly.If in open type (open-circuit) expander opposite with the closed type compressor, use steam as working fluid, this does not select so.In addition, use liquid refrigerant to come lubricate compressors to mean the refrigeration agent incomplete evaporation, thereby mean the non-constant of the coefficient of performance (being refrigerating efficiency).Therefore, the design alternative that in patent US 6217304, proposes is difficult in the machine of reality, obtain proof.

Summary of the invention

In order to overcome the problem in this background technique, the present invention has been proposed.

From one side; The present invention relates to utilize the screw rod machine of the working fluid that comprises liquid phase; Said screw rod machine comprises two rotors that perhaps more have helical structure engagement, lubricated; Wherein said rotor has " N " shape profile that this paper limits, and in use, and the lubricated only liquid phase through working fluid of the helical structure of said rotor realizes (perhaps like this at least basically).

The method of lubricated screw rod machine when the present invention also can be expressed as a kind of use and comprises the working fluid of liquid phase; Said screw rod machine comprises two rotors that perhaps more have helical structure engagement, lubricated; Said rotor has " N " shape profile that this paper limits, and wherein this method comprises that the liquid phase of only utilizing working fluid basically lubricates the helical structure of said rotor.

Mentioned " basically only " attempts to be illustrated in can carry in the working fluid in a small amount or various other fluids of trace in this specification; Even add wherein indeliberately, and said other fluid can have some very slight lubrication effects.Yet, effective lubricating still fully or mainly depend on the existence of the liquid phase of specific working fluid, it is lubricated invalid to make the shortage of this liquid phase to cause.

Basically, therefore all lubricated responsibilities are carried out by the liquid phase of specific working fluid.In addition, the lubricating fluid that carries in the working fluid preferably obtains from the working fluid that gets into expander, can not add more liquid in advance to working fluid basically.This is useful simple mechanism.Yet, if necessary, can add more liquid in advance, and this being added on broadly is not excluded in the present invention.

Use the liquid phase of working fluid to omit the lubrication system that is used for oil lubricant is transported to the costliness of those structures as the oiling agent that is used for helical structure.The present invention has also avoided the oil pollution of working fluid and has avoided the working fluid process machine needs of separating oil from working fluid afterwards.

Rotor can be processed by any suitable material.In order to make contingent minimise wear, their helical structure can be coated with low-friction coating, the Balinit C2 (trade mark) that is for example provided by Oerlikon Balzers.Balinit C2 is " WC/C " coating, its deposit through physical vaporous deposition (PVD) and comprise carbide mutually with carbon mutually.Preferably on the helical structure at least of rotor, use low-friction coating, the wear characteristic at this place is worth this coating.Yet from the reason of cost, if possible, preferably the helical structure of rotor keeps not being coated.Potential advantage of the present invention just is through using " N " shape profile rotor to allow this situation.

Gratifying lubricated in order to confirm that rotor obtains, it is safest using the rotor of " N " shape profile that applies.Yet claimant's test also shows, if be coated with low-friction coating such as (for example Balinit C2), the rotor with other profile can be used for some convincingly and use.Therefore; On the other hand; The invention still further relates to the screw rod machine that utilizes the working fluid that comprises liquid phase; The conveyor worm machine comprises two or more be coated with low-friction coating, rotor engagement, lubricated helical structure, wherein in use, the helical structure of rotor lubricated basically only the liquid phase through working fluid realize.The method of the lubricated screw rod machine when this scheme of the present invention also can be expressed as a kind of use and comprises the working fluid of liquid phase; The conveyor worm machine comprises two or more have and be coated with low-friction coating, rotor engagement, lubricated helical structure, and wherein this method comprises the helical structure that only lubricates rotor basically through the liquid phase of working fluid.

In all schemes of the present invention, rotor is preferably by bearings, and said bearing is in use also only lubricated by the liquid phase of working fluid basically.Use liquid phase to come lubricating bearings to omit the lubrication system that is used for oil lubricant is transported to the costliness of those bearings.It has also avoided the pollution of working fluid, and has avoided the working fluid process machine needs of separating oil from working fluid afterwards.

For simplicity, be preferably Hydrodynamic by the liquid phase of working fluid lubricated bearing, but they can be static pressure.Simultaneously; The big gap that hydrodynamic bearing is required and thereupon the rotation of the axle in the bearing can make the efficient of machine a little lower slightly than the efficient of the similar machine that uses rolling body bearing, screw rod steam expander can be manufactured into use liquid phase water as bearing lubricant.

Hydrodynamic bearing moves through between rotary part or slide part and their static housing, keeping lubricant film, makes except starting and shutting down, not come in contact between them.The basic principle of operation is that this film is not a homogeneous thickness.Under the situation of radial bearing, this rotating center at axle takes place when moving apart the center of radius of housing on every side.This can cause around the film of this oiling agent inhomogeneous, thereby causes that the pressure in the oiling agent significantly increases in the thinnest zone of film.Pressure difference around the film is enough to force this to be back into on every side housing to align, and therefore prevents spool and housing comes in contact.

The pressure that produces in the lubricant film depends on the viscosity of the oiling agent of realizing in the lubricant film and the minimizing of thickness.Normally, this bearing is oil lubrication.Yet, developed the hydrodynamic bearing of the fluid (like water and hydrocarbon) of the liquid that adopts low-down viscosity such as some specialized companies such as Waukesha Bearings company of Wisconsin, USA.The successful key of these bearings is to move through very small minimum film thickness, and the bearing material that uses is not easy to block or wear and tear between startup and down period.

Widely in the theory, hydrostatic bearing also is fine in the present invention, but because they need the external pump and the circulatory system to implement them, so they are not most preferred.Especially, this bearing prevents that rotor shaft from contacting with on every side housing through one group of liner in the housing of allowing pressurized gas or liquid and passing.The balance of the pressure between rotor shaft and the liner prevent to come in contact between them and rotor shaft its rotation during by fluid support.

Rolling body bearing such as those ball-types or roller bearing type also can be used in support rotor when suitably designing.

It is possible that the liquid of lubricating bearings derives from working fluid separately.Yet such as the helical structure of rotor, coming lubricating bearings through the liquid phase that from working fluid, obtains is to be preferred cleverly and therefore.

In expander was used, working fluid was water or wet vapor the most valuably, made that the liquid phase that is used for the liquid phase of lubricating screw shape structure and selectively also is used for lubricating bearings is a liquid water, for example was the liquid water that can be carried in the vapor stream.Yet the screw rod machine also can similarly be designed for any working fluid, like hydrocarbon or refrigeration agent, as long as the liquid phase of same fluid is used for the helical structure of lubricated rotor easily and selectively also is used for lubricating bearings easily.

Use viscous resistance that another advantage of low-viscosity (mobile) liquid (such as water) of the helical structure of lubricated rotor is that oiling agent causes still less than oil.Therefore, rotor can be with the speed rotation higher than the oil-filled machine that is equal to, and this helps flow.

From simple, compact and purpose cheaply, especially for fear of unwanted oil lubrication, most preferably, rotor does not connect through independent timing gear.Therefore, the same with oil-filled machine, the synchronous of rotor only depends on that the cooperation of the helical structure of engagement is useful.This means that synchronising torque only is delivered to another via their meshing spiral shape structure from a rotor basically.

In the past some constantly, steam screw rod expander is by Computer-Assisted Design, Manufacture And Test, but in them any one do not carried out the lubricated record of process-liquid, any one in them not have the record successfully operated yet.

By the present invention, if working fluid also can be used in lubricating bearings, so whole oil lubrication system and do not have oily machine or the needed optional feature of oil-filled machine can both be removed.

Test 1

Have in test in the screw rod machine of " N " shape rotor profile, the claimant utilizes the air compressor of oil-filled type to experimentize, so there is not timing gear.Therefore, the lubricating contact between the helical structure of this compressor dependence rotor is come these rotors synchronously.

Be contrary to general knowledge, the claimant is through only making an experiment by replacing oil to be injected into the helical structure that lubricates rotor in the working fluid in water.Under the sort of situation, the bearing that rotor is installed to housing be roll type and be full of oiling agent.Rotor is the steel that scribbles Balinit C2 coating.

Then, compressor moves 150 hours through the contact between the helical structure of rotor, only lubricates through the water that replaces oil to be injected in the working fluid.When this stage finished, these rotors were examined, and showed the sign that does not have wearing and tearing or damage, and slight polishing is just arranged on contact zones.

Test 2

The coating rotor of example 1 is substituted by the rotor of " N " shape profile of a pair of steel that is not coated and moves other five hours.When finish this period, check uncoated rotor, they do not demonstrate tangible wearing and tearing sign yet.

Test 3

Subsequently, do not having water to be injected under the situation in the working fluid fully, the compressor with " N " shape profile rotor that is not coated moves two hours by error.Rotor is not still kept significantly and is damaged, and certainly, if machine run surpasses quite long period under situation the about helical structure of rotor not being lubricated, can expect to produce some damages.

The claimant infers that for the screw rod machine of the rotor with " N " shape profile, the major function of lubrication system is a lubricating bearings.As long as there are some liquid (even this liquid is low viscous, such as water) on the helical structure of rotor, just need not timing gear and avoid direct rotor contact.The present invention has used this discovery and has implemented this principle.

Description of drawings

The rotor profile of some existing technologies has been described to Fig. 2 (d) to Fig. 1 (d) and Fig. 2 (a) with reference to Fig. 1 (a) of accompanying drawing.In order more easily to understand the present invention, now will be by the exemplary reference accompanying drawing, wherein:

Fig. 3 is the schematic cross sectional views of passing according to the steam expander of the first embodiment of the present invention; And

Fig. 4 is the schematic cross sectional views of passing steam expander according to a second embodiment of the present invention.

Embodiment

At first with reference to the Fig. 3 in the accompanying drawing, screw rod expander 20 comprises stationary housing 22, and it comprises the spiral

band leaf rotor

10,16 of two engagements, and these two rotors center on parallel axis counterrotating in

housing.Rotor

10,16 is processed by any suitable material (like steel), selectively is coated with low-friction coating (like aforesaid Balinit C2).They have claimant disclosed in patent WO 97/43550 " N " shape rotor profile.

Each

rotor

10,16 is installed to corresponding

axle

24,26, and the hydrodynamic bearing of

axle

24,26 and then each end through supporting each is installed to housing 22.Axle in 26 extends to the generator (not shown) that the outside of housing 22 is used to generate electricity with driving.

Treat that expanded working fluid (being wet vapor in this example) gets into housing 22 with high pressure conditions through entry port 30.Steam flows and expands through the inside of housing 22, thereby causes

rotor

10,16 with high-speed rotation, and steam leaves housing 22 through discharge port 32 with low-pressure state.

Need not timing gear so that

rotor

10,16 rotates synchronously.Alternatively,

rotor

10,16 is connected synchronously because of the engagement of its helical structure.This need be lubricated helical structure, and this is guaranteed by the liquid phase water that carries in the wet vapor supply.

In the illustrated embodiment, bearing 28 also is lubricated by the water from the wet vapor supply.Water storage portion 34 is communicated with entry port 30 and the water that will be under the pressure through supply pipeline 36 is fed to each bearing 28.

In the selectable improvement project shown in Fig. 4 of accompanying drawing; The equalizing piston (balance piston) 38 at place, the end of each

rotor shaft

24,26 utilizes the pressure of working fluid to resist the axial load of axle, thereby has reduced the load that the bearing 28 of back shaft is born.Like this, pressure piping 40 is connected to entry port 30 with equalizing piston 38.

Being used for expanded working fluid can (like the steam from geothermal source) obtain from multiple source.In this respect, can recall, the screw rod expander is can handle wet working fluid (that is the fluid that, comprises gas phase and liquid phase simultaneously) and the risk that almost do not have to damage to the key advantages of turbine expander.Aspect that handle to pollute or dirty working fluid (as comprising from the sand of geothermal source or from the wet vapor of the molecules such as iron rust of corrosion pipeline), the screw rod expander is also much better than turbine expander.Another advantage is that the screw rod expander has more cost benefit than the turbine that is used for relatively little power output potentially.

Aforementioned content illustrates, and the present invention's design and the steam expander of making need not as not having the desired timing gear of oily machine, inner shaft Sealing, lubricant reservoir portion, lubricating pump, lubricant filter or heat exchanger or need not like the desired lubricating pump of oil-filled machine, heat exchanger and oil separator.In addition, fully overcome by the present invention for no oily machine of the prior art and oil-filled machine problem all common, the lubricant pollution working fluid.

The representative of industrial steam system is according to the main potential application of screw rod expander of the present invention.A lot of industrial processs all need be supplied steam, for example prepare food, papermaking and chemical process.Usually, central boiler produces the steam that is in the high pressure of appropriateness, and this steam is distributed near factory, workshop or other industrial facility via pipe-line system.Steam is discharged in each position that needs through lateral.

Because the various process in the industrial facility possibly need different vapor pressures, so each lateral has control valve usually, said control valve arrives the needed lower pressure of in question process with steam throttling.Can use the screw rod expander to substitute throttle valve and reduce vapor pressure.This makes can reclaim power from inflation process, keep simultaneously with required lower pressure supply steam.By the present invention bring about cost, robustness, compactedness, reliability, efficient and to avoid benefit such as oil pollution be vital for accepting the steam expander is used for this application, especially replaces the intention of multiple throte valve in industrial facility.

Claims

One kind with wet vapor as the screw rod expander of working fluid; Said expander comprises two or more rotors with helical structure engagement, lubricated; Wherein said rotor has " N " shape profile that this paper limits; And in use, the lubricated of the helical structure of said rotor only is responsible for by the water that carries in the wet vapor working fluid basically.
2. expander according to claim 1, wherein said helical structure is coated with low-friction coating.
3. expander according to claim 2, wherein said coating comprise carbide mutually with carbon mutually.
4. according to aforementioned any described expander of claim, wherein said rotor is by at least one bearings, and said at least one bearing is in use also only lubricated by water basically.
5. expander according to claim 4, wherein said bearing is a hydrodynamic bearing.
6. expander according to claim 4, wherein said bearing is a rolling body bearing.
7. according to any described expander in the claim 4 to 6, wherein said bearing is lubricated by the water that from the wet vapor working fluid, obtains.
8. according to aforementioned any described expander of claim, wherein said rotor is delivered to another rotor with synchronising torque from a rotor through the helical structure of engagement via them and is synchronized.
9. expander according to claim 8 does not wherein have timing gear to act between the said rotor.
10. according to aforementioned any described expander of claim, also comprise the thrust piston that resists epitrochanterian axial load.
11. expander according to claim 10, wherein said thrust piston plays a role through the pressure of wet vapor working fluid.
12. according to aforementioned any described expander of claim, the lubricated water that wherein carries in the wet vapor working fluid obtains from the wet vapor that gets into said expander, need not basically to add more water to wet vapor in advance.
13. the method for a lubricated screw rod expander when wet vapor is used as working fluid; Said expander comprises two or more rotors with helical structure engagement, lubricated; Said rotor has " N " shape profile that this paper limits, and wherein this method comprises the helical structure that only utilizes the water that carries in the wet vapor working fluid to lubricate said rotor basically.
14., comprise making water lubricate the bearing that supports said rotor according to the method for claim 13.
15., comprise the water that from the wet vapor working fluid, obtains lubricated said bearing according to the method for claim 14.
16., comprise that through the helical structure via the engagement of said rotor synchronising torque being delivered to another rotor from a rotor makes said rotor synchronous according to method any in the claim 13 to 15.
17. according to method any in the claim 13 to 16, the lubricated water that wherein carries in the wet vapor working fluid obtains from the wet vapor that gets into said expander, need not basically to add more water to wet vapor in advance.
18. a dynamic force generating unit comprises according to any described screw rod expander in the claim 1 to 12 perhaps having the screw rod expander of operating according to any described method in the claim 12 to 17.