CN100557197C - A kind of mixed flow type turbine vane - Google Patents

Abstract

The invention discloses a kind of combined flow turbine semi-open type (or enclosed) impeller that turbo-expander is used in internal combustion engine turbocharger, middle-size and small-size gas turbine installation, chemical industry and refrigeration (gas liquefaction with the separate) equipment.By flow field analysis, the present invention has illustrated wheel rotation angular velocity , the interior meridional stream line slope inclination angle δ of wheel and meridional stream line is to flowing in taking turns the operating mode factor and the geometrical factor of material impact to be arranged at the semidiameter Δ r of impeller inlet/outlet.Also corrected simultaneously and spread the cacodoxy of deep and broad " work done of Coriolis power " and the impeller design misdirection principle of corresponding association in the prior art.On this basis, the present invention has set up the selection that obtains high efficiency mixed flow type turbine vane meridian profile construction shape important geometric parameter under the higher specific speed operating mode and has recommended the scope of using.

Description

A kind of mixed flow type turbine vane

Technical field

The present invention relates to internal combustion engine turbocharger, medium and small gas turbine installation, the turbine wheel that turbo-expander is used in chemical industry and refrigeration (gas liquefaction with the separate) equipment.

Background technique

Press the direction that fluid flows in turbine wheel, can be divided into three types of axial-flow turbine, radial turbine and combined flow turbines.Wherein, axial-flow turbine, fluid flows through along the approximate direction parallel with impeller shaft; Radial turbine, fluid flows into impeller by wheel rim to the rotating shaft core direction along approximate vertical with impeller shaft radial direction, transfers axial outflow at the impeller outlet place; Combined flow turbine (claiming Oblique-flow turbine again) is a kind of intermediate form between axial-flow turbine and radial turbine---fluid is along crossing impeller with the conical flow of impeller shaft inclination.Combined flow turbine obtains high efficiency a kind of improved form as radial turbine under the higher specific speed situation, be widely used in recent years and develop.In fact, the inlet/outlet limit of mixed flow type turbine vane blade tilts (increasing the flow passage component blade height) and the increase of outlet cincture edge diameter, and it all is that the blade shape of radial turbine impeller is for adapting to high speed conditions down-off to a kind ofly tending to naturally that capacity development greatly changes that the main geometric properties of these impeller shapes changes.Than the radial turbine impeller suitable increase being arranged as for mixed flow type turbine vane flow passage component axial length, then is in order to improve the wheel flow field, increase flow mild.

Compare with radial turbine, the most tangible advantage of combined flow turbine is to obtain high efficiency under higher specific speed.Because the critical role of turbine efficiency in turbine performance research, also make to obtain under higher specific speed more that high efficiency becomes topmost research direction in the combined flow turbine.

(such as the RR151 pressurized machine of ABB AB in the practice of turbocharger applications combined flow turbine, the Garrett pressurized machine of Honeywell company, the KTR150 pressurized machine of JP-6301, the RH-3 pressurized machine of Ishikawa island company etc.), the highest isentropic efficiency that has all confirmed combined flow turbine is higher than radial turbine, on average improves about 5% approximately.But it is aspect the theoretical research of radial turbine and combined flow turbine, extremely insufficient.Even to combined flow turbine specific diameter streaming turbine efficiency height why? the raising of radial turbine efficient that actually has been which effects limit? how to design combined flow turbine and could guarantee to obtain high efficiency? the basic problem that relates to mechanism more like this, prior art still is in the exploratory stage so far, wherein is no lack of the mistake that has basic conception and idea aspect, influence causes can not give correctly, instruct effectively design to correct understanding, analysis and the judgement of reason.

Be better than " the simple mechanism " of radial turbine for the efficient of combined flow turbine, the entrance edge of blade that prior art is summed up as mixed flow type turbine vane is on skewed (with turbine shaft cant angle theta angle) this geometric properties. think this moulding that is beneficial to form " forward curved vane " along the nearly hub portion of blade import hypotenuse that is configured with; Thereby reduced " corner loss " that " the incident loss " of air-flow and fluid produce when radially turning to axial flow in impeller channel, so (seeing relevant commentary and report in the 14th～18 page of " development of the Mixed Flow Turbine for Vehicle Turbochargers " diesel engines such as related content in the 19th～20 page of " adopting H145 turbocharger and the application on the Z6170 diesel engine thereof of the combined flow turbine " diesel engine such as Zhang Jindong the 6th phase in 2003 and Shi Xin the 6th phase in 2000 for details) compared and can be raised the efficiency greatly to combined flow turbine with radial-flow type. In fact, on the turbine wheel of some radial-flow turbochargers in the 60 to 70's of last century, just adopted entrance edge of blade to be skewed structure (as the ZY-120 pressurized machine of NR pressurized machine, Chongqing heavy-duty car research institute and the Chongqing Automobile Engine Factory of the 4HD pressurized machine of Schwizer company, MAN company etc.), but on these turbine stage, do not demonstrate the be significantly improved advantage of efficient of turbine stage than conventional radial turbine impeller with entrance edge of blade and rotating shaft keeping parallelism.In addition, for conventional radial turbine impeller, equally can by blade shape construction on its entrance edge of blade that does not tilt by wheel hub to wheel rim form respectively antecurvature, radially, the distribution pattern at how much angles of different blade imports such as palintrope and antecurvature sweepback.Wherein, antecurvature sweepback type impeller just has how much angle distribution patterns of (shown in Figure 3 as Chinese patent publication number CN01231703.9 " mixed flow turbine impeller ") same blade import that mixed flow type turbine vane is had along the requirement of blade lean inlet side.The moving flow field comparative analysis of quasi-three dimensional flow of the conventional radial turbine impeller of how much angle distribution patterns of different blade imports shows, has the turbine wheel that how much angles of antecurvature sweepback type blade import distribute, really has variable working condition conformability preferably, can reduce the difference angle of attack that becomes a mandarin and change the flow losses of hyperplasia, improve variable working condition turbine efficiency down, but to the highest isentropic efficiency value of turbine stage can not be significantly improved (see " radial-inward-flow turbine impeller inlet molded lines is to the influence of off design performance " dynamic power machine and Engineering Thermophysics such as Xu Jinfeng for details---national dynamic power machine and Engineering Thermophysics youth scientific paper public lecture collection of thesis Xi'an publishing house of Xi'an Communications University October in 1989 the 659th～663 page) .Therefore, the entrance edge of blade of turbine wheel tilts and distributes along how much angles of antecurvature sweepback type blade import of entrance edge of blade is not the unique geometric properties of mixed flow type turbine vane, and the radial turbine impeller can have equally.So they are not to cause the essential reason of combined flow turbine efficient apparently higher than radial turbine efficient.To this, turbosupercharger and diesel engine coupling result of experiment have also been proved this viewpoint:depend merely on two measures of change turbine blade inlet side tilt angle and the blade import on it how much angles distribution, still can not obtain tangible efficiency benefit---and the minimum fuel oil consumption decline of diesel engine is little.

Summary of the invention

The objective of the invention is to by to Study on Flow analysis contrast in axial flow, runoff and the mixed flow type turbine vane wheel, in many geometrical factors and operating mode factor that influence is flowed, the flowing of they of determining to send as an envoy to produces the different factor that has the greatest impact each other; Correct and to spread deep and broad wrong understanding and idea in the prior art; Based on this, set up the geometric parameter that obtains high efficiency mixed flow turbine impeller meridian profile construction shape and rationally recommend the scope of using.

In view of flowing in axial flow, runoff and the combined flow turbine, all can be similar to and be simplified to the combination of flowing along gang's arbitrary surface of revolution leaf grating.Here, the geometrical shape of this family's turning surface is to be rotarily formed around same rotating shaft (turbine shaft) by the meridional stream line family in the impeller.So the stream interface of axial-flow turbine is gang's turning surface close with coaxial circles cylinder shape; The stream interface of radial turbine is that gang is at approximate radial plane, the approximate turning surface that is the cylndrical surface of outlet of being of impeller inlet; The stream interface of combined flow turbine is the approximate conical surface, the approximate turning surface (accompanying drawing 1) that is the cylndrical surface of outlet of being of gang's impeller inlet.Obviously, the difference of stream interface (being meridional stream line) geometrical shape is the primary importance geometrical factor that makes the great difference of mobile generation in axial flow, runoff and the combined flow turbine level.The meridional stream line shape mainly is reflected in distribution δ (r) or the δ (z) of slope inclination angle δ=arctg (dr/dz) value along meridional stream line to the influence of turning surface cascade flow field, and meridional stream line is at the semidiameter Δ r=of impeller inlet/outlet (r ₁-r ₂) on these two geometric elements (accompanying drawing 2).

According to the arbitrary surface of revolution leaf grating flow theory in the fluid dynamics of turbomachine, inviscid fluid streams the permanent mobile of leaf grating must satisfy absolute motion irrotationality equation $\mathrm{rot}\stackrel{\→}{C}=\mathrm{rot}(\stackrel{\→}{W}+\stackrel{\→}{\mathrm{\ω}}\×\stackrel{\→}{r})=\mathrm{rot}\stackrel{\→}{W}+2\stackrel{\→}{\mathrm{\ω}}=0,$ When fluid is mobile along arbitrary surface of revolution, curl

Only at the normal of turning surface

Direction important So following formula turns to $\mathrm{rot}\stackrel{\→}{W}\·\stackrel{\→}{n}=-2\stackrel{\→}{\mathrm{\ω}}\·\stackrel{\→}{n},$ Promptly get the motion equation that fluid flows and must follow along arbitrary surface of revolution ${\mathrm{rot}}_n\stackrel{\→}{W}=-2\mathrm{\ω}\sin \mathrm{\δ},$ In the formula -fluid motion the speed (absolute velocity) measured by the absolute coordinate system that is consolidated with turbine stage static element (housing, nozzle ring); -fluid motion the speed (relative velocity) measured by the relative coordinate system that is consolidated with the turbine stage rotary blade;

-wheel rotation angular velocity (accompanying drawing 3).

Known by this motion equation: the fluid motion in the rotary blade in the turning surface leaf grating is that relative movement has flowing of revolving, and its curl value is-2 ω sin δ.When δ=0 (axial-flow turbine, stream interface are the cylndrical surface), flow through with The flowing of arbitrary cylndrical surface leaf grating in the axial-flow turbine impeller that angular velocity rotates, identical with this situation of streaming that same cylndrical surface leaf grating is static when not rotating (ω=0), promptly flowing in the axial-flow turbine impeller is not subjected to rotating speed (angular velocity ) influence.This is the mobile essential reason place that is different from radial turbine impeller and mixed flow type turbine vane fluid movement that forms in the axial-flow turbine impeller.For near the flowing radial turbine impeller inlet, because 90 ° of δ ≈, cause this part regional flow field to bear having the greatest impact of curl that angular velocity of rotation produces.Comparatively speaking, near the flowing mixed flow type turbine vane import, because 0＜δ＜90 °, the influence of the curl that angular velocity produces is between axial-flow turbine and radial turbine.As for the axial exit portion of radial turbine and mixed flow type turbine vane, because the δ ≈ 0 of this part stream interface, then as the axial-flow turbine impeller, flowing on the stream interface is not subjected to the influence of angular velocity substantially.

As for velocity distribution of flow field in the arbitrary surface of revolution leaf grating in the impeller, can illustrate with following method is clear: in fact, rotating speed is

Flow is to stream flowing of arbitrary surface of revolution leaf grating under the G operating mode, static current flow and another flow that does not rotate the same turning surface leaf grating of (ω=0) of the fluid winding flow that can be decomposed into a flow be G is zero (G=0, the import and export of leaf grating runner are respectively along circumference sealing), flow direction with

In the switched in opposite that the resolute of turning surface Normal direction is determined, vortex strength is the stack (accompanying drawing 4) that the grow degree circulation of 2 ω sin δ flows in same turning surface leaf grating runner.So flow is that G, rotating speed are

Stream under the operating mode in the flowing of arbitrary surface of revolution leaf grating, in the leaf grating arbitrarily the velocity vector of any equal the velocity vector sum of same point in above-mentioned two flow fields exactly.Since the circulation in the closed flow (going back to the whirlpool) turn to

In the switched in opposite of the component of turning surface Normal direction, through with the current flow stack after, cause near the leaf grating runner suction surface flow velocity to increase and near the pressure side flow velocity reduces.Vortex intensity 2 ω sin δ values are big more, and pressure side that it causes and the speed difference between suction surface be big more (accompanying drawing 5) just." transverse-pressure gradient " of the corresponding association of this velocity gradient is one of major impetus source from pressure side to suction surface that made " lateral transfer campaign " (secondary flow) along wheel hub surface by of the low kinetic energy fluid in the wheel hub boundary layer, and be very big to the value size influence of " damaged on end mistake ".

In sum, meridional stream line slope inclination angle δ is very deep and broad to the influence that turning surface leaf grating in taking turns flows, be far from the influence of " corner loss " difference in size that the turning emergency degree difference that just meridian plane in the impeller is flowed that prior art is familiar with causes, but with the mobile influence that applies rotational speed omega to the every bit place in the turning surface cascade flow field in whole wheel of the form of curl 2 ω sin δ.In addition, many " combined flow turbine " of the prior art design, that though inlet edge of impeller blade has been made is skewed (with the rotating shaft angle be θ), but the flow direction of dividing speed by the meridian that is divided into binary " mean velocity " by the level flow that its nozzle blade (or vaneless scroll of single, double passage) outlet is flowed out, not perpendicular with the inclination inlet side of impeller, the direction of still pressing 90 ° of the δ ≈ of radial turbine design flow into should " combined flow turbine " impeller.For this " combined flow turbine ", its essence is still radial turbine, and the wheel flow field does not have obvious change.Therefore, correct, a high efficiency combined flow turbine level design, the design of only paying close attention to impeller not enough, also must make the design and the good good coupling of its formation of nozzle ring or vaneless scroll, also promptly the structure of this nozzle ring or the vaneless scroll meridian that should have a mean velocity that makes its outlet divides fast direction to meet δ ₁≈ (the ability of 90 °-θ) inflow impeller direction.

As for second geometric element of meridional stream line shape---semidiameter Δ r=(r ₁-r ₂) to the influence of turning surface cascade flow field in taking turns, as first geometric element δ, also combining with rotational speed omega applies.Each turning surface in the wheel in the turning surface family (being rotarily formed around same rotating shaft core line) by different meridional stream line in the wheel, their semidiameter Δ r=(r ₁-r ₂Though) differ from one another, semidiameter Δ r is identical to the influence mode that flows on each turning surface.For the influence that reflects that it flows to whole impeller, now select to analyze for representative along middle turning surface (flow between wheel hub turning surface and wheel rim turning surface is divided into binary middle turning surface, and it is rotarily formed around the shaft by the center line of flow path in the impeller meridional stream line family).For middle turning surface, semidiameter Δ R is impeller inlet geometrical mean radius R ₁=[(R _1sh ²+ R _1h ²)/2] ^0.5With impeller outlet geometrical mean radius R ₂=[(R _2sh ²+ R _2h ²)/2] ^0.5Between poor, Δ R=(R ₁-R ₂) (accompanying drawing 6).

The common geometric properties that radial turbine impeller and mixed flow type turbine vane are different from the axial-flow turbine impeller is to have tangible semidiameter Δ R.Its explanation exists radial displacement or Radial Flow when flowing through runoff, mixed flow type turbine vane.Because fluid is by the bigger R of radius in the impeller of high speed rotating ₁Flow to the less R of radius ₂" entad flow ", so this flow process must overcome " centrifugal inertia force " (convected inertial force) $\stackrel{\→}{f_{\mathrm{cen}}}=\mathrm{dm}{\mathrm{\ω}}^2\·\stackrel{\→}{r}$ Acting in opposition could realize (in the formula, dm is the fluid elementary mass).Centrifugal inertia force is to the effect of this flow process.Can reflect with the merit that its fluid motion is done, also promptly for the unit mass fluid $L_{\mathrm{cen}}=\underset{R_1}{\overset{R_2}{\∫}}\stackrel{\→}{f_{\mathrm{cen}}}\·\stackrel{\→}{\mathrm{dr}}=-\underset{r_1}{\overset{R_2}{\∫}}{\mathrm{\ω}}^2\mathrm{rdr}=-{\mathrm{\ω}}^2\underset{r_1}{\overset{R_2}{\∫}}\mathrm{rdr}={\mathrm{\ω}}^2(R_1^2-R_2^2)/2=(U_1^2-U_2^2)/2.$ In the formula

---velocity of moving space (peripheral velocity), $\stackrel{\→}{U}=\stackrel{\→}{\mathrm{\ω}}\×\stackrel{\→}{r}.$ Here it is determines that fluid flows through famous Euler equation (turbomachine fundamental equation) L of impeller work done value size _u=(C ₁ ²-C ₂ ²)/2+ (W ₂ ²-W ₁ ²)/2+ (U ₁ ²-U ₂ ²Form item for the 3rd in)/2.

Up to now, at home and abroad in the monograph and textbook of the influential turbomachine principle of One's name is legion, the fluid dynamics of turbomachine and turbosupercharger, to (U ₁ ²-U ₂ ²There is wrong understanding in the mechanics-based explanation of)/2; Think that (its value is U in " Coriolis power " work done ₁ ²-U ₂ ²) a part; Think also that in entad the flowing of footpath, mixed flow type turbine vane inner fluid because of the generation of " Coriolis power " is not accompanied by turning to of air-flow or subsidiary frictional loss, its effective merits of a part of doing come down to that produce power not loses more.Set up the misdirection principle of design turbine wheel thus: the radius size difference Δ R=(R that should as far as possible strengthen impeller inlet and outlet ₁-R ₂), (see the 112nd～115 page of M.H. Wa Fula work " aerothermodynamics in the turbomachinery and flow " Beijing Machinery Industry publishing house August in 1984 for details so that the share of the value of " Coriolis power " work done proportion in the wheel work that the Euler equation is determined is big as far as possible; И. И. the 575th～582 page of another works " turbomachinery principle " Beijing Machinery Industry publishing house June nineteen eighty-two of the 157th～158 page of Kirilov work " gas turbine and gas turbine installation " first volume Beijing Machinery Industry publishing house nineteen fifty-nine and he; The 276th～278 page of Zhu Meilin chief editor " Principle of Turbosupercharger " Beijing National Defense Industry Press June nineteen eighty-two; Zhu Daxin writes the relevant argumentation in the 179th～181,224 pages of " turbosupercharging and turbosupercharger " Beijing Machinery Industry publishing house November in 1992).

To be above-mentioned document occurred mistake in the understanding of following basic mechanical notion with using to the reason that causes above-mentioned cacodoxy:

● with the Coriolis acceleration

Being considered as acting on " Coriolis power " on the unit mass fluid, is with diverse two notions---" power " obscures into identical concept with " acceleration " in the mechanics.Because every power, must possess the characteristic that directly to measure with dynamometer (see the many husbands' works of B Γ Nie Fuzige Leah (the yellow thought rather translated) " theoretical mechanics " first volume Beijing people education publishing house 1964 August the 242nd page), " Coriolis power " can not directly be measured with dynamometer, so it is not a power.Flow through in the flowing of wheel rotor runner at fluid, do not have " Coriolis power ", but have the effect of Coriolis inertial force.Act on the Coriolis inertial force on the unit mass fluid $\stackrel{\→}{f_{\mathrm{cor}}}=-2\stackrel{\→}{\mathrm{\ω}}\×\stackrel{\→}{W}.$

● Coriolis inertial force is present in impeller and is consolidated with angular velocity omega in the relative coordinate system (noninertial system) that turbine shaft rotates, and it flows through the effect that applies when impeller channel is done relative movement at fluid.All the time the displacement that produces with relative movement because of this power $\stackrel{\→}{\mathrm{ds}}=\stackrel{\→}{W}\mathrm{dt}$ (being estimated by relative coordinate system) is perpendicular, so its merit identically vanishing $(L_{\mathrm{cor}}=\stackrel{\→}{\∫f_{\mathrm{cor}}}\·\stackrel{\→}{d}s\≡0).$ In the absolute coordinate system (inertial system) that is consolidated with turbine stage static element (housing, nozzle ring), Coriolis inertial force is non-existent.Thereby this movement process of implicated displacement dl=Udt=ω * rdt (being estimated by absolute coordinate system) that its convection cell just exists in absolute motion can't work done.With adhering to value that power that different coordinates exists and displacement link together with product separately is not have the notion of Newton mechanics " merit " and meaning.

● Coriolis inertial force is not the true power that produces owing to object interaction.True power is with the different of inertial force: the existence of true power (such as pressure, frictional force, gravitation, electromagnetic force, elastic force etc.) does not change because of the selection of system of coordinates, acts on all no matter which kind of system of coordinates to describe it with; Inertial force is then different because of the selection of system of coordinates.Another important difference is that true power exists reaction force, and then there is not reaction force in inertial force.Thereby Coriolis inertial force can not be directly and is produced the relation of active force and reaction force between the blade of turbine wheel and the exchange of merit amount takes place.In fact, turbomachine is that a kind of interaction by blade and fluid realizes the machinery that the exchange of merit changes the fluid energy level.When fluid was flowed through rotary blade, it acted on the blade face with the form of pressure, the making a concerted effort of pressure turbine shaft was produced moment (moment of torsion), produced power when wheel rotation.

In fact, can derive the process of Euler equation by utilizing the theorem of kinetic energy in the fluid dynamics of turbomachine, it forms (a U strict proof ₁ ²-U ₂ ²)/2 are the work done value of centrifugal inertia force really.

Continue analysis rotational speed omega and semidiameter Δ R influence below to the turbine wheel fluid movement.According to energy equation (stagnation rothalpy is along same streamline conservation) and $W_2=\mathrm{\ψ}\sqrt{W_1^2+(i_1-i_2)-(U_1^2-U_2^2)},$ In the formula, W ₁, W ₂---be respectively the relative velocity in impeller turnover, outlet port; (i ₁-i ₂)---the constant entropy enthalpy difference of impeller inlet/outlet place fluid; Flowing velocity loss coefficient in ψ---the impeller.Its illustrates under the effect of centrifugal inertia force field (centrifugal field), impeller outlet flow velocity W ₂With difference (U ₁ ²- ₂ ²) increase and reduce.Along with (U ₁ ²-U ₂ ²) increase, W ₂Not only can be less than W ₁(the deceleration diffusion flows), even can be decreased to zero (no flow passes through in the impeller).This situation has highlighted the footpath again, combined flow turbine is different with axial-flow turbine: in axial-flow turbine, as long as have enthalpy difference (i in the wheel ₁-i ₂＞0) just W can not appear in the impeller, ₂＜W ₁Diffusion flow; For footpath, combined flow turbine, must make $(i_1-i_2)>(U_1^2-U_2^2)$ .In turbine wheel, W ₂＜W ₁Mobile should preventing, otherwise longshore current can make boundary layer growth, separation to being that diffusion flows, and causes flow losses to be increased sharply.Because $U_1^2-U_2^2={\mathrm{\ω}}^2(R_1^2-R_2^2)={\mathrm{\ω}}^2(R_1+R_2)(R_1-R_2)={\mathrm{\ω}}^2(R_1+R_2)\mathrm{\ΔR},$ Therefore, for control flow velocity in the wheel under high rotating speed operating mode retarding efffect and the pressure lift-rising degree before the turbine wheel that occurs of corresponding association, effective measures are that the poor Δ R value in control footpath is little when the geometrical shape of design impeller channel, to limit (U ₁ ²-U ₂ ²) value transfinites.

Obviously, Δ R reduces to weaken significantly the effect of centrifugal field in the wheel, thereby the hydrodynamic pressure of turbine wheel inlet is descended, and makes the also corresponding decline of hydrodynamic pressure before the nozzle ring.This is to being applied to the situation particular importance of internal combustion engine turbocharger, because the decline of turbine inlet pressure can cause the I. C. engine exhaust back pressure to reduce, and the wasted work that makes piston overcome the back-pressure effect when combustion gas reduces---and the fuel of internal combustion engine consumption descends.

For the difference that comprehensive relatively axial flow, runoff and combined flow turbine flow in wheel each other, " secondary flow " in also must taking turns them analyzed, compared." secondary flow " of turbine wheel inside comprises that mainly the low kinetic energy fluid in wheel hub turning surface (also will comprise the wheel rim turning surface to double shrouded wheel) the top interlayer flows toward the migration that suction surface " crosses runner " from the runner pressure side along wheel hub surface (and rim faces---double shrouded wheel); Along blade surface, the low kinetic energy fluid on the blade face flows toward the migration of leaf top (wheel rim position) direction from blade root (hub positions); And the gap at the wheel rim turning surface place of half-opened impeller gas leakage and blade swipe flowing of boundary layer, static turbine volute inner wall matching gap position, totally three parts.The difference of " secondary flow " mainly is reflected in the first portion in axial flow, runoff and the mixed flow type turbine vane wheel.Low kinetic energy fluid (the relative velocity W that adheres on the impeller hub of radial turbine and combined flow turbine (wheel rim) turning surface _B≈ 0), move along the component of hub (edge) face and synergy lower edge wheel hub (wheel rim) turning surface of Coriolis inertial force in difference force, centrifugal inertia force.In view of the component ω of centrifugal inertia force along hub (edge) face ²Flowpath pressure face that r sin δ generally produces than main flow motion and the pressure difference between suction surface (along the main current flow collimation method to, point to suction surface---difference force action direction by pressure side) big, along main flow flow direction pressure reduction dp=ρ d[(ω ²r ²-W ²)/2] (ρ is a fluid density in the formula) then less, and Coriolis inertial force-

Value very little (because of W _BVery little), so the General of hub (edge) face " secondary flow " is that low kinetic energy fluid is partly done move mobile by the less nearly pressure side district of radius to the direction in the bigger suction surface district of radius along hub (edge) face in hub (edge) the face boundary layer.Because the flow direction and the main flow of hub (edge) face " secondary flow " are " tiltedly contrary direction ", so import main flow at it along " washing away " of constantly being subjected to reverse main flow in the migration flow process of hub (edge) face, are not prone to separated flow and cause big flow losses.Secondly, the circumferencial direction width of the runner of hub face turning surface is very big to exporting contraction change from impeller inlet.This just causes the through-flow width convergence of cross section of fluid channel gradient very big, main flow acceleration degree increases, and the pressure reduction between flowpath pressure face and suction surface sharply reduces from impeller inlet to outlet, the hub face Flow area in the nearly quite big zone of impeller outlet is very little, and these cause very big restriction all for the existence of " secondary flow " on the hub face turning surface and development.This also is the reason place of going up generation, the development of " secondary flow " and influencing fundamental difference with axial-flow turbine impeller hub face (cylndrical surface)." secondary flow " on axial flow turbine impeller hub face is mobile along " tiltedly along the direction " of main flow migration, it thickens nearly runner suction surface (vacuum side of blade) accumulation that exports of the suitable main flow direction of the low kinetic energy fluid in hub face boundary layer and separates, and causes value quite big " damaged on end mistake ".

As everyone knows, in three types turbine stage, when the blade height long enough of flow passage component (promptly the level flow is enough big), the highest isentropic efficiency value that the axial-flow turbine level can reach is the highest, and combined flow turbine takes second place, and radial turbine is minimum.This mainly is because due to the adverse effect difference of rotating speed, and " damaged on end mistakes " have a strong impact on because of flow losses near the primitive level wheel hub and the wheel rim only, at this moment presses the on average still little cause of its zone of influence proportion of the high length of leaf.Along with flow reduces, the corresponding minimizing of blade height, " damaged on end mistake " be the also corresponding increase of proportion in flow losses, but because of the ordering of " damaged on end mistake " influence is the heaviest to axial-flow turbine, mixed-flow is taken second place, and radial-flow type is the lightest, so the three is near each other when most effective value descends synchronously.To reduce to the blade height that makes axial-flow turbine little to " secondary flow " zone of influence that makes (wheel rim) two ends, its blade root (hub face) and leaf top when accounting for the high certain proportion of whole leaf when flow, and the peak efficiency value that radial turbine can reach can surpass axial-flow turbine.And when the axial-flow turbine blade root, when the zone of influence merged together, the highest isentropic efficiency value of axial-flow turbine level just sharply descended " secondary flow " of two ends, top, and this moment, it should not be worked under this low flow rate condition, should for usefulness directly, combined flow turbine.

See from the viewpoint that increases the highest isentropic efficiency value of blade height minimizing " damaged on end mistake " raising turbine stage, increase the axial width and the tiltangle value of entrance edge of blade, it is favourable making further increase of blade height on mixed flow turbine impeller inlet limit.This measure also is applicable to the outlet limit of nozzle blade and the outlet limit of impeller (strengthening tilt angle γ).

Described before combining, wheel speed (angular velocity

) be to make axial flow, runoff and mixed flow type turbine vane flow field produce different most important operating mode factor each other.It is high that rotating speed changes, and centrifugal inertia force is big more to the adverse effect that flows in taking turns.The structure of mixed flow type turbine vane more helps weakening the effect of centrifugal inertia force than the structure of radial turbine impeller, thereby can make the obvious specific diameter streaming of the highest isentropic efficiency turbine stage height of combined flow turbine level in the appropriate design that has effectively suppressed influence of centrifugal force.

Can illustrate based on same reason: for taking turns the comparison that close radial turbine of footpath size and combined flow turbine efficient change with rotating speed (expansion ratio), why is the isentropic efficiency difference of the two big during than the slow-speed of revolution when high rotating speed? and why axial flow can be described, be runoff and combined flow turbine level in that is flow big but the highest isentropic efficiency value that the relatively low operating mode of rotating speed can reach is very approaching? this situation, in the application of large and medium-sized turbosupercharger, attract people's attention especially in recent years.Be applied to the turbine stage of the turbosupercharger of big or middle power diesel engine at these,, cause order and produce same pressure ratio (with impeller rim velocity U because of flow big (blade is long, wheel rim diameter big) ₁=ω R ₁Square be directly proportional) the angular velocity omega value low far beyond the small flow that reaches same pressure ratio (steamboat footpath) the needed angular velocity of impeller, so can make directly, the efficient of mixed flow turbine level obtains obvious lift-rising and near the efficient of axial-flow turbine.Thereby might make high mixed-flow of a part of efficient and radial turbine, because of its structure of having simplified and low manufacture cost but the advantage of the not obvious reduction of usability, clamp-on originally entirely this application that occupies by axial-flow turbine and form a kind of new development trend.

Analyze in front, contrasted on impeller geometric parameter and the wheel speed basis to the influence of flowing in taking turns, the present invention sets up the important geometric parameter that obtains high efficiency mixed flow type turbine vane meridian profile construction shape and rationally recommends with scope as follows:

R _2sh≤R _1sh；

＝R ₂/R ₁＝0.73-0.93；θ＝20°～70°；γ＝-15°～30°；

＝B/(2R ₁)＝0.45～0.60；

＝l ₁/(2R ₁)＝0.16～0.25.

Wherein,

---outlet edge of impeller blade geometrical mean radius R ₂With inlet edge of impeller blade geometrical mean radius R ₁Ratio.Its value has reflected impeller blade inlet/outlet limit geometrical mean radius difference Δ R=(R ₁-R ₂) relative inlet edge of impeller blade geometrical mean radius R ₁The value size,

=1-Δ R/R ₁

Angle between θ---inlet edge of impeller blade and rotating shaft core line.Its approximate reflection is taken turns the interior slope inclination angle δ of meridional stream line on impeller blade import hypotenuse ₁(90 °-θ) value size of ≈;

---the axial length B and the inlet edge of impeller blade geometric mean diameter of impeller blade flow passage component $D_{1_m}=2R_1$ Ratio.Increase

, can increase meridional stream line slope inclination angle δ from impeller inlet to impeller outlet change mild;

---impeller blade import inclined side length l ₁With the inlet edge of impeller blade geometric mean diameter

Ratio.Its value is the relative height value of blade.

The angle of γ---outlet edge of impeller blade and radial direction.Increase the γ angle, the blade exit edge lengths is increased, blade passage outlet throat width increases (discharge area increase).

So far, prior art as yet not to the geometric parameter of mixed flow type turbine vane select to release system, scope use in complete recommending, and has only the example of individual design, application to report.Combined flow turbine is as a kind of improvement of radial turbine under the higher specific speed situation, and it all is to get its upper limit with reference to the corresponding geometric parameter recommended range of radial turbine suitably to amplify and use instead that their parameter is selected.Recommending with scope of prior art radial turbine impeller geometric parameter is as follows: R ₁=R _1sh=R _1hR _2sh/ R ₁=0.7～0.86; R ₂/ R ₁=0.5～0.6; θ=0 °;

＝B/(2R ₁)＝0.31～0.36；

＝l ₁/(2R ₁)＝0.08～0.15；γ＝0°～10°。

Contrast the scope of using of recommending of the present invention and radial turbine impeller geometric parameter, can find out that geometric parameters number average that the present invention recommends the mixed flow type turbine vane of usefulness has significantly with value than recommending of prior art radial turbine increases, and has shown that high efficiency mixed flow type turbine vane shape is to the approaching trend of axial-flow turbine impeller shape.

In view of the mixed flow type turbine vane of the present invention's design, its wheel hub outlet radius R _2hBe worth generally all greatlyyer, reduce leaving loss, should adopt exhaust diffuser (be installed in turbine wheel and export, link together) with gas outlet hausing in order to reclaim exhaust energy.The good exhaust diffuser of design can improve turbine stage efficient 3～5% approximately.Obviously, flow to consistent (promptly approximate) in the flow direction that is aided with turbine nozzle ring blade (or single, double runner vaneless scroll) outlet average flow and impeller blade import along direction inflow impeller perpendicular to entrance edge of blade, and installed under the addition thereto that designs good exhaust diffuser at impeller outlet, the mixed flow type turbine vane that the mixed flow type turbine vane geometric parameter range of choice of recommending according to the present invention designs, compare with combined flow turbine with the runoff of prior art, because of declining to a great extent and l of Δ R value and δ value ₁Increase makes rotating speed and " secondary flow " weaken greatly the adverse effect that flows in taking turns, thereby the combined flow turbine level that has guaranteed the present invention's design obtains more high efficiency---effect of the present invention.

Description of drawings

Fig. 1 a is the meridional stream line distribution schematic diagram of mixed flow type turbine vane wheel flow field.There is shown and form wheel hub turning surface stream interface, wheel rim turning surface stream interface, and position and the shape that will take turns the meridional stream line (turning surface bus) of the interior binary centre of flow (average, center) turning surface stream interface.Wherein, wheel hub, wheel rim turning surface stream interface are rotarily formed around the impeller shaft shaft axis by the meridian plane profile of impeller hub and wheel rim respectively.The meridional stream line (bus) of middle turning surface stream interface passes their geometrical mean radius point a and b respectively on the inlet/outlet limit of impeller blade.Fig. 1 b is the schematic representation of turbine cascade on the arbitrary surface of revolution.

Fig. 2 is the slope inclination angle δ=arctg (dr/dz) of any meridian streamline (turning surface stream interface bus) last any 1 A of S in the mixed flow type turbine vane wheel flow field.δ is that meridional stream line S goes up the tangent line at A point place and the angle between the rotating shaft core line.Meridional stream line is at the semidiameter Δ r=of impeller inlet/outlet (r ₁-r ₂).

Fig. 3 is a fluid when arbitrary surface of revolution flows, any 1 A place curl

At this place's turning surface normal The resolute of direction and wheel rotation angular velocity vector

At A point normal

The relation of direction resolute (the two switched in opposite, the value of curl resolute are 2 ω sin δ).

Fig. 4 is that G, rotating speed are for arbitrary flow

Stream current flow and another flow that fluid winding flow that flowing of arbitrary surface of revolution leaf grating can be decomposed into a flow G do not rotate the same leaf grating of (ω=0) under the operating mode and be zero (G=0) but turn to and

Resolute direction in this turning surface Normal direction is opposite, and vortex strength is the stack that the grow degree circulation of 2 ω sin δ flows in same turning surface leaf grating runner.Shown in the figure is the synthetic schematic representation that flows.

Fig. 5 is two mobile speed stack schematic representation in the turning surface leaf grating runner shown in Figure 4.Among the figure 1---the runner suction surface; 2---the flowpath pressure face.

Fig. 6 is combined flow turbine level (being made up of nozzle vane ring and impeller) schematic representation and impeller meridian section member and main geometric mark figure.

Fig. 7 a is the mixed flow type turbine vane structural representation that the technology of the present invention is suitable for.Fig. 7 _bAn example for the combined flow turbine half-opened impeller meridian profile construction shape of the technology of the present invention structure.

Embodiment

Below, by embodiment with in conjunction with the accompanying drawings technology contents of the present invention is further described.

Fig. 7 _aWhat illustrate is the mixed flow type turbine vane structural representation that the technology of the present invention is suitable for.This turbine wheel is a kind of diagonal flow type centripetal turbine impeller---fluid flows into impeller inlet along oblique " entad " that become the θ angle with radial direction, and steering shaft is to flowing out impeller outlet then.This combined flow turbine level has a lot of application in turbosupercharger, turbo-expander and small size gas turbine device.Fig. 7 _aWhat illustrate is a double shrouded wheel structure, and it is the overall structure impeller that is combined into one by precision casting by wheel cap (wheel rim) 5, blade 4 and wheel disc (wheel hub) 3 three parts.If remove wheel cap 5, then this impeller just becomes a half-opened impeller.Double shrouded wheel efficient height but intensity is low; Half-opened impeller is intensity height and efficient is low slightly then, thereby half-opened impeller is used more extensive.When the design blade shape, fluid inlet angle on the turbine wheel blade import inclined side is distributed meet impeller inlet velocity triangle under the selected design conditions to the distribution requirement of fluid inlet angle on the import inclined side, in order to avoid produce big incidence loss, reduce turbine efficiency.Generally, select the inflow relative velocity at a place, entrance edge of blade geometrical mean radius position Average meridian flow velocity with entrance edge of blade

Identical, promptly ${\stackrel{\→}{W}}_1={\stackrel{\→}{W}}_{1m}.$ Like this, know according to velocity triangle,

Relative fluid inlet angle β ₁=90 °, and the relative velocity of the inflow impeller of wheel hub and wheel rim position With

Relative fluid inlet angle then because of R _1h＜R ₁＜R _1sh(promptly ${\stackrel{\&RightArrow;}{U}}_{1h}<{\stackrel{\&RightArrow;}{U}}_1<{\stackrel{\&RightArrow;}{U}}_{1\mathrm{sh}}$ ) and make β respectively _1h＜90 ° and β _1sh＞90 °---on impeller blade import inclined side, constitute the inlet angle distribution requirement of " antecurvature sweepback type ".This distribution can be in the general radial turbine impeller blade moulding of prior art---radially additionally again on the parabolic blade shape construction method of straight burr implement that inlet side is cut sth. askew and the parabola directrix shape adjusted on the reference level is realized.If change again ${\stackrel{\&RightArrow;}{W}}_1={\stackrel{\&RightArrow;}{W}}_{1m}$ Put the position on blade import inclined side, can obtain the inlet angle changes in distribution of more many types of formula.When adjusting the lopsided fluid inlet angle of blade import, only should calculate the center line of using the blade profile of dissecing out with the vertical plane of the inlet side that tilts the tangent line at inlet side place and circumference of impeller to angle as the relative fluid inlet angle of this position; Should not count the influence of vane thickness, with blade profile suction surface (or pressure side) the tangent line at inlet side place and circumference of impeller to angle as the relative fluid inlet angle β of this position ₁Because use along the tangent direction of blade profile leading edge center line and calculate relative fluid inlet angle, it had both counted the influence of suction surface side varied in thickness to blade profile import molded lines shape.Counted the influence of pressure side side varied in thickness too, like this than unilateral ground only consider the one-sided varied in thickness of suction surface side (or pressure side side) to the influence of blade profile leading edge geometrical shape, with suction surface (or pressure side) tangent line of blade profile leading edge and circumference of impeller to angle to calculate the method for relative fluid inlet angle more reasonable, more realistic.Therefore, when the impeller blade moulding, when relating to fluid inlet angle adjustment calculating, only need the shape adjustments of crestal surface in the blade is got final product, vane thickness distributes to adjust and should not get involved.

Fig. 7 _bWhat illustrate is an example by the combined flow turbine half-opened impeller meridian section shape of the technology of the present invention structure, and selected geometric parameter is as follows:

For a typical prior art radial turbine impeller design:

D _1sh＝D _1m＝D _1h，D _2sh＝0.85D _1m，D _2h＝0.4D _2sh＝0.34D _1m，

D _2m＝[(D ² _2sh+D ² _2h)/2] ^0.5＝0.64734D _1m，

＝D _2m/D _1m＝0.64734，

$(U_1^2-U_2^2)/2={\mathrm{\&omega;}}^2(1-{\stackrel{\&OverBar;}{R}}_2^2)D_{1m}^2/8=0.0726{\mathrm{\&omega;}}^2{D}_{1m}^2$

If the wheel footpath D of the mixed flow type turbine vane of the present invention's design and above-mentioned prior art radial turbine impeller _1mIdentical and in the work of same rotating speed operating mode, know that then the merit must overcome centrifugal force that entad flows in the mixed flow type turbine vane wants specific diameter streaming turbine wheel much smaller---the two ratio is 0.45: 1, promptly the structure of mixed flow type turbine vane weakened greatly centrifugal field it is taken turns in mobile adverse effect.

Analyze by this example, as can be known

Value is to the significance of wheel flow field influence.Adopt the big blade wheel structure of θ value, though mainly be for reducing the δ value of impeller inlet, the R of its association ₁Value decline causes

The favourable influence that value increases the wheel flow field can not be ignored too.

Runner geometrical shape from the impeller meridian section of present embodiment is seen, combined flow turbine is the high efficiency a kind of improved form of acquisition as radial turbine under the higher specific speed operating mode, its impeller meridian shape (turning surface is to wheel rim turning surface part especially) is very near the axial-flow turbine impeller.

Claims (2)

1, a kind of mixed flow type turbine vane, impeller is double shrouded wheel or half-opened impeller, double shrouded wheel is made of blade 4, wheel disc 3 and wheel cap 5 three parts, half-opened impeller is made of blade 4, wheel disc 3, it is characterized in that: the axial length B of impeller blade flow passage component and inlet edge of impeller blade geometric mean diameter D _1m=2R ₁Ratio

=B/D _1mSelect with scope and be

=0.45～0.60; Outlet edge of impeller blade geometrical mean radius R ₂=[(R _2sh ²+ R _2h ²)/2] ^0.5With inlet edge of impeller blade geometrical mean radius R ₁=[(R _1sh ²+ R _1h ²)/2] ^0.5Ratio

=R ₂/ R ₁Select with scope and be

=0.73～0.93.

2,, it is characterized in that by the described impeller of claim 1: the angle theta between inlet edge of impeller blade and rotating shaft core line to select with scope be θ=20 °～70 °; Impeller blade import inclined side length l ₁With inlet edge of impeller blade geometric mean diameter D _1mRatio

=l ₁/ D _1mSelect with scope and be

=0.16～0.25; Angle γ=-15 of outlet edge of impeller blade and radial direction °～30 °.

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