CN2165248Y - Free pistong type liquid pressure energy recoverer - Google Patents

Abstract

The utility model relates to a free piston type liquid pressure energy recover. The utility model uses Pascal hydrostatic pressure transfer principle as a foundation. Liquid with survival potential energy can transmit the potential energy to a piston which can freely carry out reciprocal motion in static pressure transmittal mode, and then the piston can directly transmit the energy to another liquid. The machine can maintain the actual recovery rate of available energy at more than 90%. In addition, the utility model is provided with a speed regulating power head for driving a synchronistic gearbox and then driving the forcible valve control system of a rotary ball valve and a free piston.

Description

Free pistong type liquid pressure energy recoverer

The utility model includes pressure flow hydrodynamic physical efficiency recycle device, particularly relates to the recycling mechanical device and the hydraulic engineering mechanical device of chemical liquid energy in the chemical engineering.

In chemical process, usually there is requirement under certain pressure, to use certain liquid scrubbing to purify certain process gas, washed the rich solution behind the gas, need to reduce pressure again and regenerate, make rich solution become lean solution, and the manufacturing process that lean solution is pressurizeed again and utilized; Sometimes need from system, isolate the manufacturing process of certain liquid condensate in addition with suitable pressure.

Any flowing liquid, when it is in pressure when higher, always be in to hold when pressure hangs down more potential energy is arranged than it, so the step-down process of working fluid be actually a process of eliminating working fluid potential energy, and in a single day the static pressured fluid that has flows, pressure promptly disappears, so no potential energy, this paper for the purpose of simplifying the description, below alleged liquid all be meant flowing liquid.

The power that is discharged in liquid energy dissipating process is N1=(P1-P2) * Q * 10 ⁶/ (g * 102) Kw(1)

The theoretical power (horse-power) Kw of N1-energy dissipating process in the formula

The pressure MPa of P1, the forward and backward liquid of P2-step-down

The volume flowrate M of Q-liquid ³/ S

G-gravity accleration 9.8M/S ²

102-kgM/S and Kw scale factor

At present because technology and economic two aspects, generally have only as N1 〉=200Kw and just consider to use certain hydraulic engineering machinery, the energy of this energy dissipating process is recycled.And in the occasion of N1＜200Kw, then the potential energy that often uses reduction valve that the pressure high liquid is held is converted into kinetic energy, because the rubbing action between high-speed liquid self and the wall, thereby decompression temperature rise phenomenon appears.The decompression temperature rise is harmful to Physical Absorption, therefore causes unnecessary cooling sometimes.Even N1＞200Kw sometimes, but because P1 pressure is too high,＞10.0MPa, the technical hydraulic machinery that does not still have mature and reliable can utilize at present, also often adopt reduction valve, and that this is not useful energy is reclaimed.

Along with global energy shortage and energy prices go up, the sort of in the past is that the viewpoint of recovery limits obviously no longer meets objective situation and required with N1 〉=200Kw, must expand boundary to N1 〉=20Kw, even it is also lower than this, in order to adapt to this economic requirement, technical must to design a kind of reuse efficiency higher, moves the recovery machine of the remaining potential energy of the new liquid more reliable, that cost is lower.

At present pressure recovery is relatively low (is generally 1.0～5.0MPa) and flow (is generally 1.0～5.0 * 10 greatly ^-1M ³/ s) the method for the remaining potential energy of liquid, be to adopt water turbine---water pump---motor unit, as come out to be rich in the solution of carbon dioxide from the synthetic ammonia decarburization, enter fluid turbine (water turbine), drive turbine, the shaft of water wheels directly links to each other with centrifugal lean solution compression pump (water pump), because unit efficiency and produce must consume energy, when the output power of water turbine can not satisfy the pump power needs, provided by motor.(be generally 12.0～13.0MPa), (be generally 2.0～20 * 10 for relative pressure is higher and flow is less relatively ^-3As go out the copper liquid of synthetic ammonia cuprammonium washing tower for removing CO M/s).Though theoretical here recoverable energy N1=25～250Kw, but not having ready-made water conservancy project machinery can adopt, the general recovery of remaining potential energy, (referring to volume, Chemical Industry Press publication in 1981 P174～177,185, P199～200, the P227-229 such as inorganic chemical technology (one) synthetic ammonia, Dalian Polytechnic Colleges) of all not carrying out.

Adopt water turbine---water pump---motor three machines coaxial (water pump---turbines) reclaim the remaining potential energy in the rich solution, following shortcoming is arranged:

1, the theoretical utilization ratio of available energy is low, and it is lower that reality can reach efficient.Largest on the our times, state-of-the-art water turbine and water pump, the peak efficiency that they can reach ≯ 75%.The efficient of general middle-size and small-size industry water turbine and water pump then has only about 70% water pump---and the total efficiency of water turbine series connection unit is that two component efficiencies connect take advantage of long-pending, and the highest of actual total efficiency reaches about 50%.

2, operating flexibility is too small, is prone to negative efficient phenomenon.Because the relation of the flow Q of water pump, water turbine, lift or drop H and rotation speed n is very responsive.After the series connection of three machines, the possibility that revolution changes is very little, and this variation only is because the mains frequency variation causes, and mains frequency changes general ≯ 1.0%, moreover is subjected to inside and outside many condition influence, all can be influential as weather, temperature, variation in pressure.But the permission amplitude of variation of water turbine has only 10%.This obviously is not enough.When requiring flow by water turbine to surpass design discharge, choking phenomenon will appear in water turbine, and then must open the bypass flow partially liq this moment, loses some available energy; When in a single day the water yield by water turbine is starkly lower than design discharge, the stall phenomenon of the turn up of water turbine less than specified rotating speed will appear, because in fact water turbine and water pump, the coaxial series connection of motor, thereby motor traction water turbine occurring turns round with synchronous speed, water turbine becomes a load of motor on the contrary, i.e. " the negative efficient phenomenon " of water turbine.Both at home and abroad loading onto a kind of differential clutch that is connected between petrol engine, diesel engine and the actuating motor that is similar between water turbine and the water pump in recent years, as long as water turbine reaches stalling point, when output torque drops to zero, water turbine just can be thrown off automatically with water pump, thereby has avoided occurring negative efficient phenomenon.Even so, state-of-the-art in the world at present unit, the annual mean total efficiency also has only 30-40%.

3, the water turbine of chemical plant use needs regulate very continually water turbine stator vane (nozzle).This becomes very complicated with regard to the structure that makes it, manufacture also just relatively difficult, cost is also than higher, and the blade root of each stator vane need have an end to reach the casing outside, so that rotor blade is regulated, sealing and leakage problem have so just appearred, if the liquid by water turbine is valuable chemicals, then this problem is more outstanding, if will realize the blade adjustments automation, then need the mechanical transmission of a cover more complicated, so be difficult for realizing whole factory automation.

The utility model is exactly bad at the effect of decarburization workshop section rich solution overbottom pressure utilization in the synthesis ammonia plant, the copper washing section rich solution overbottom pressure not actual conditions of good utilisation is made, purpose provides a kind ofly can fully recycle the mobile machinery that pressured fluid potential energy is arranged, free-piston hydraulic energy-recovering machine.

This liquid energy reclaims machine is increased the pump V by what a working solution inlet/outlet Forced Valve assemblying body I that four valves are arranged, free-piston fluid cylinder assemblying body (II A, II B), one had four valves by transfusion inlet/outlet self-acting valve assemblying body III, a low pressure liquid suction booster IV, an auxiliary circulating pump VI, a highly pressurised liquid, and connects the fluid pipeline that above-mentioned each assembly imports and exports by technological requirement and form.

The applied basic principle of the utility model is Pascal's hydrostatic pressure transfer principle.In its working procedure, the potential energy that working liquid body held of high pressure, be not converted into other forms of energy, only in the mode of Hydrostatic Transfer Device, by being isolated in two kinds of free-pistons between the liquid, pass to the liquid that is transferred, piston is done free to-and-fro motion in fluid cylinder, the piston form is the pure free-piston of single cylindrical type, piston is by cylindrical live body 7, a plurality of whole piston ring 6 that tightly is enclosed within the not opening on place, the big footpath of the piston body step, between the two-piston ring every the circle metal ring 31 of opening not equally.Piston body can be solid, and it also can be hollow and annotate plumbous or annotate other materials.Piston ring is to make of the teflon of the self lubricating material that contains molybdenum sulfide, graphite and so on, and the internal diameter of piston ring and the external diameter of piston body reach the external diameter of piston ring and the internal diameter of fluid cylinder and meet the requirement that is slidingly matched.

The valve of control liquid inlet and outlet cylinder working liquid is a kind of mechanical type Forced Valve assemblying body I, and it is by the speed governing unit head---synchronous gear box---, and ball valve is formed.Moving 19 driving gear 18 that drives in the synchronous gear box 15 of speed governing, driving gear 18 drives two moduluses and the identical driven gear 17 of the number of teeth and 21 again, to form two driven gear synchronization, each driven gear is protruding two semiaxis from the tooth case, respectively connect a ball valve 1A on each semiaxis top, 1B and 2A, 2B, 1A and 2B are in the same way, 1B and 2A are in the same way, and 1A and 2B and 1B and 2A 90 ° of phase differences mutually, synchromesh gear rotates a circle, twice on four each switches of Forced Valve, two groups of ball valves have closed overlapping time before unlatching and after opening, do not have the overlapping time of unlatching.

The utility model provides the pressured fluid energy-recovering machine, under the perfect condition that does not have mechanical leakage and mechanical friction and liquid friction merit to consume, the effective rate of utilization of utilizable energy is 100%, as long as it is reasonable in design, make superior, even above those losses are arranged, the effective rate of utilization of available energy also can reach 90-95% at least.And working pressure, can from zero point several MPas until tens MPas, working liquid body flow Q can be from 1～500 * 10 ^-3M ³/ S.

In order to illustrate that clearly this liquid energy reclaims the working principle of machine and the structure of critical piece, is elaborated below in conjunction with accompanying drawing.

Fig. 1 free piston type liquid energy reclaims the machine fundamental diagram

Fig. 2 mechanical type Forced Valve structure sketch

Rule diagrammatic sketch when Fig. 3 mechanical type Forced Valve valve opens and closes

Fig. 4 free-piston structure diagrammatic sketch

Smart line is represented the working liquid body track route among Fig. 1, and fine rule is that dotted line is a liquid track route behind the piston back by the transfusion track route.

What solid line was represented among Fig. 1 is: the 7A free-piston in the II A fluid cylinder is in and moves down; 7B free-piston in the II B fluid cylinder is in the stage of up moving, going out absorption system in this stage has the rich solution of pressure (following general designation working solution) the Forced Valve 1A by being opened by force, enter the last space of the piston of II A fluid cylinder, under the acting in conjunction of working fluid pressure and piston deadweight, force piston to move down, in the process that piston moves down, the lean solution that is retained in the space under the piston (following general designation is infused) is to equal or to be slightly larger than the pressure of rich solution, through being extruded unit by transfusion outlet self-acting valve 12A, remove high-pressure booster V, behind high-pressure booster supercharging 0.2-0.3MPa, enter tower absorption system, meanwhile from regenerative system by transfusion fluid, through low-pressure charging pump IV, be pressurized to behind the certain pressure by space under the piston of transfusion through entered fluid cylinder II B by transfusion import self-acting valve 11B, under by the promotion of infusion pressure, force piston up to move, in the process that piston moves down, the working solution that is retained in the space on the piston is to be slightly less than the pressure of being infused, working solution outlet Forced Valve 2B through being opened by force discharges unit and enters regenerative system.When the piston among the fluid cylinder II A moved to lower dead center, the piston among the fluid cylinder II B also arrived top dead center simultaneously.Moment before this two-piston arrives stop simultaneously, Forced Valve 1B and 2A are closed again simultaneously by force.Moment after closing, Forced Valve 1B and 2A are opened again by force, and it is mobile that this moment, quilt transfusion and working solution were pressed the dotted line trend in Fig. 1.Piston up moves in this stage fluid cylinder II A, and the piston among the fluid cylinder II B moves down.When the piston of two cylinders arrived at top dead center and lower dead center respectively, Forced Valve 1A and 2B were opened again simultaneously, and the piston among the fluid cylinder II A is moved down again, and the piston among the fluid cylinder II B up moves again, so moves in circles, and long-time running is gone down.Because the activity of piston in fluid cylinder is freely, so upper and lower stop there is no the fixed position, and the travelling speed of piston in fluid cylinder then is decided by to enter the instantaneous flow of fluid cylinder liquid fully, and this instantaneous flow is decided by a pump of minimum discharge in high-pressure booster V and the low-pressure charging pump IV two pumps, after this instantaneous flow decision, the few reciprocal time both of these case of many reciprocal times of short stroke or long stroke just may appear.Because the reciprocal time of piston per minute in fluid cylinder only is decided by that Forced Valve opens and closes conversion times, the few reciprocal time of long stroke is main points in service, and few reciprocal time just means that Forced Valve keying conversion times is few, and then Forced Valve service life just can be longer.In order to ensure can long stroke, so upwards stretched out a piston stroke indicating arm 3 outside the fluid cylinder lid 10 from piston 7, the position that can find out lower dead center on the piston according to this bar in service, judge whether piston stroke is enough, if stroke falls short of, then can reduce the Forced Valve per minute and open and close number of times, piston stroke is increased.In general, normally in service at unit, the free-piston in the fluid cylinder is to clash into fluid cylinder upper and lower cover 10,9, because the piston stroke indicating arm is arranged, can come stroke is carried out manually or control automatically by it.But when installation just, debugging or misoperation, piston slap fluid cylinder lid is possible, for this reason in the inboard outer ring of 10,9 upper and lower fluid cylinders lids, according to the size of fluid cylinder diameter, arrange several damping springs 4,8, to prevent the rigid impact of piston to lid.

In the whole service process, remaining in the fluid cylinder pressure of being infused in the space under the piston equals or is slightly larger than on the piston pressure of working solution in the space, this is the important requirement of chemical process aspect, because only in this way, just can avoid working solution to leak into by in the transfusion.Accomplish this point, if the own wt of accomplishing piston greater than the frictional force between piston ring and the fluid cylinder wall, this can increase the weight of the piston own wt and adopt frictional force very little and have from fluoroplastic piston two aspects of polishing performance and solve.The method that piston increases the weight of is made piston body solid, or fills metallic cobalt in the hollow cavity of box type piston body.

The critical piece that this liquid energy reclaims machine has the I working liquid body to import and export the Forced Valve assemblying body, II A, II B oil hydraulic cylinder assemblying body, and III is infused imports and exports self-acting valve assemblying body three parts, existing as follows with regard to its relevant structure division:

I, working solution are imported and exported the Forced Valve assemblying body, and claimed structure is simple, and is durable in use, low price.The discharge opeing of advancing of controlling each fluid cylinder with it does not allow on the opening time and anyly opens " overlapping time " in small, only require and close " overlapping time " small the time, otherwise the efficient of energy-recovering machine will descend.

The utility model adopts the mechanical forced valve.It is frequency conversion (or slippage) speed-adjustable motor-multi-stage planetary gear speed reducer-synchromesh gear-ball valve.Unit by speed-adjustable motor-multi-stage planetary gear speed reducer is formed claims the speed governing unit head again, is existing mature technology.

Accompanying drawing 2 is seen in the essential structure of mechanical type Forced Valve, and it is the driving gear 18 that drives in the synchronous gear box 15 with speed governing unit head 19, and driving gear 18 drives two moduluses and the identical driven gear 17 of the number of teeth and 21 again, and is synchronous to form two gear rotational speeds.Be the trouble of simplified apparatus manufacture view, in the synchronous gear box, preferably select the identical same gears of major parameter such as three moduluses, the number of teeth, tooth depth, the central shaft diameter of axle for use.Each driven gear, protruding two semiaxis respectively connect a specially-made ball valve, 1A, 1B and 2A, 2B on each semiaxis top from gear-box.So-called special ball valve, the angle of rotation and the relation between the valve opening and closing that require exactly to rotate in this ball valve will meet Fig. 3 " rule require during the forced opening-closing angle ", before opening, every group of Forced Valve stay 5 ° of closed overlapping times with unlatching reserve, be that real opening angle has only 80 ° requirement, as long as this suitably amplify any with the diameter that rotates in the standard ball valve just can accomplish.Guaranteeing under the constant condition of fluid passage that cone angle≤40 of rotation perforate ° just.And do like this, to the working life that prolongs ball valve also be useful.In four ball valves that link to each other with synchronous gear box, 1A and 2B in the same way, 1B and 2A homophase, and 1A and 2B and 1B and 2A 90 ° of phase differences mutually, synchromesh gear whenever revolves and turns around, twice on all four each switches of Forced Valve.If the free-piston reciprocal time is 2-10 time/minute, then the rotating speed of synchromesh gear is 1.0-5.0 time/minute.

Rule diagrammatic sketch when Fig. 3 is mechanical type Forced Valve valve opening and closing, 22,23,33 is the upper ball valve fluid passage among the figure, 24,25,34 are following ball valve fluid passage, 35 ball valve sense of rotation, solid line represents that upper ball valve is equivalent to 1A and two Forced Valve of 2B among Fig. 1; A is that 1A and 2B two valves begin the breakdown point, piston begins to move, b is 1A and 2B 2 valve Close All points, the piston arrives stop, c represents that 1B and 2A two valves begin the breakdown point, piston begins to move once more, d is that 1B and 2A two valves close close point fully, piston is to another stop, and e is 1A and 2B two a valve secondaries breakdown point again, cone angle≤40 of α, β one ball valve spiral and valve channel perforate °, opening angle≤80 of γ-1A and 2B two valves °, overlapping angle≤10 ° are closed in opening angle≤80 of δ-1B and 2A two valves °, ε-Forced Valve, stop at stop at this angle inner carrier.

II, oil hydraulic cylinder assemblying body, in Fig. 1 fluid cylinder II A, II B they all by fluid cylinder cylindrical shell 5, down fluid cylinder lid 9, on fluid cylinder lid 10, and free-piston 7 parts such as grade are formed.Fluid cylinder be bear liquid high pressure and pressure repeatedly the metal cylinder, inwall of alternate meet the requirements to guarantee its physical dimension and surface finishment through cutting, the processing of boring and grinding.The two ends of liquid cylinder are provided with flange, so that cover with the Bolt Connection fluid cylinder, the shape of fluid cylinder lid, except can make plate shaped, also can make the fluid cylinder lid hemispheric according to the size of the height and the fluid cylinder diameter of working pressure, oval-shaped, or the end socket of dish, again end socket and flange are welded together, connect with bolt and liquid cylinder sports association.

Piston form in the fluid cylinder is the pure free piston type of mono-cylindrical, and the operating conditions of piston is superior, and it is in work under the very low pressure all the time, and fluid cylinder becomes vertical layout, can not cause the eccentric wear of piston ring owing to the influence of piston deadweight.Piston ring always is under liquid cooling in the cylinder, the lubricating condition and moves.In order to make full use of these advantage, piston has adopted new design.

The essential structure of Fig. 4 free-piston is to be slightly less than on the stepped shape piston body 7 of liquid cylinder 5 internal diameters at a maximum diameter place, puts the teflon piston ring 6 that contains molybdenum disulfide, graphite and so on self lubricating material of a series of not opening integral body.Piston ring is on physical dimension, require its external diameter and the external diameter of fluid cylinder wall internal diameter and piston and piston body to meet the requirement that is slidingly matched, between two adjacent circle plastic hoops, every a circle is the metal ring 31 of not opening equally, after having adorned all plastic hoops, put an inboard again and have the sleeve 30 of 3-4 sulculus, the fluting of sleeve inboard is corresponding with the pin 27 on the piston body, pin just in time embeds fluting, make the sleeve can only be, and can not rotate diametrically along axially the moving up and down of piston body.After adding braking tinsel 29 on the sleeve, screw on piston cap 26 again.By rotating upper and lower projection 36,32, that adjusts plastic piston ring axially gives tight power after to a certain degree, piston is put into fluid cylinder 5, can measure the deadweight of piston overcome friction and under the condition of 1.5 times of working pressures piston is carried out pressure testing, if wherein one or binomial are all nonconforming, then need readjust piston shaft to giving tight power, if the piston deadweight is not enough, then can in the cavity of piston 7, inject and fill bore 28, till all qualified.After the test passes, Yi Bian the braking plate plate is become among Fig. 4 up, Yi Bian appearance down is loosening to prevent piston cap, what influence piston ring axially gives tight power.Used considerable time at piston, piston ring wearing and tearing occurred and has leaked, as long as wearing and tearing are very not serious, can screw piston cap, oversize piston ring give tight power, make piston ring produce the sealability that just can recover piston behind certain radial deformation again.

III is imported and exported the self-acting valve assemblying body by transfusion fluid, combination valve case in the utility model on institute's set of applications zoarium and the modern industry reciprocating pump and the valve body in the clack box with textural all identical, all are prior aries on principle, the utility model is just quoted these technology, so do not give unnecessary details.

High and low pressure liquid booster pump V, IV and auxiliary circulating pump VI are prior aries, just select for use on demand.

The utility model compared with prior art, its advantage is:

1, enlarged the scope of the remaining potential energy of chemical plant withdrawal liquid, its effective regenerative power can be from 10 to 1000KW;

2, greatly improved energy recovery efficiency, annual efficient can reach more than 90%.

3, greatly improved the off design performance of liquid energy recovering machine, changed even the flow of hydraulic fluid and pressure have very significantly, all very little to the impact of unit energy recovery rate;

If 4, the chemical plant be originally use the constant speed high-pressure plunger pump, as the occasion of liquid circulation pump, after adopting the utility model, as long as the flow of regulating the low-pressure charging centrifugal pump just can be realized the adjusting of solution circulation amount, actual power consumption also will increase and decrease with the variation of internal circulating load.

Claims (5)

1, a kind of free-piston hydraulic energy-recovering machine, it is characterized in that it comprise one have import and export in 4 valves (1A) are arranged, (1B), (2A), Forced Valve assemblying body (I) (2B), two free-piston fluid cylinder assemblying bodys (II A) that free-piston (7) is arranged in arranged side by side, (II B), one has import and export, in four valves (11A) are arranged, (11B), (12A), self-acting valve assemblying body (III) (12B), a low pressure pump (IV), a high-pressure service pump (V), a recycle pump (VI), and connect above-mentioned each equipment and become as a whole, and make two free-piston fluid cylinders can make to replace the into pipeline of discharge opeing campaign, fluid cylinder (II A), one end of (II B) respectively with Forced Valve assemblying body (I) in (1A), (1B) connecting back and liquid-inlet communicates, and respectively with (2A), (2B) connecting back and liquid outlet communicates, fluid cylinder assemblying body (II A), the other end of (II B) respectively with self-acting valve assemblying body (III) in (11A), (11B) outlet of connection back and low pressure pump (IV) communicates, and with (12A), (12B) import of connection back and high-pressure service pump (V) communicates, the outlet of high-pressure service pump (V) taps into liquid systems, the low pressure pump import picks out liquid systems, the import of recycle pump (VI) picks out liquid systems, and outlet taps into liquid systems.

2, hydraulic energy-recovering machine according to claim 1, it is characterized in that said Forced Valve assemblying body (I) is by speed governing unit head (19), synchronous gear box (15) and ball valve (1A), (1B), (2A), (2B) form, speed governing unit head (19) drives the driving gear (18) in the synchronous gear box (15), driving gear (18) drives two moduluses and the identical driven gear of the number of teeth (17) and (21), each driven gear is protruding two semiaxis from gear-box, respectively connect a ball valve (1A) on each semiaxis top, (1B) and (2A), (2B), (1A) and (2B) in the same way, (1B) and (2A) in the same way, (1A) and (2B) reach (2A) 90 ° of phase differences mutually with (1B), synchromesh gear whenever revolves and turns around, twice on four each switches of Forced Valve, two groups of ball valves have closed overlapping time before unlatching and after opening, do not have the overlapping time of unlatching.

3, hydraulic energy-recovering machine as claimed in claim 1, it is characterized in that free-piston fluid cylinder assemblying body, it is two fluid cylinders arranged side by side (II A), (II B), each fluid cylinder is by the cylindrical shape liquid cylinder (5) that a liquid entrance is arranged, free-piston (7), on the fluid cylinder, lower cover (10), (9), protrude upward the piston stroke indicating arm (3) and a plurality of being arranged in of cylinder cap (10) on piston, following cylinder cap (10), (9) Nei Ce damping spring (4), (8) form, the internal diameter of the external diameter of the piston ring on the piston and corresponding fluid cylinder cylindrical shell meets the requirement that is slidingly matched dimensionally.

4, hydraulic energy-recovering machine as claimed in claim 1, described free-piston, it is made up of cylindrical piston body (7), a plurality of piston ring (6) and the braking plate (29) and the piston cap (26) of fastening piston ring on piston body of locating on the step in the big footpath of piston body (7) of being enclosed within, it is characterized in that piston ring is the ring of complete non-incision, between two adjacent circle piston rings, enclose the not metal ring of opening (31) every one, piston body is solid.

5, hydraulic energy-recovering machine as claimed in claim 4 is characterized in that the piston ring (6) of described free-piston is the polytetrafluoroethylene ring that contains molybdenum sulfide, graphite and so on self lubricating material.

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