One, the main structure of centrifugal type compressor
1, impeller (blade annulus)
Be bring to bear on to air the part of kinetic energy, past is the means production that casts with nicety, but high speed gives in development after opportunity of 5 axes treatment, more uses the means that cutting machines. The duration of actual production worker worker of this kind of means is little, cost is low. Its material used the titanium alloy that won’t corrode or stainless steel commonly character.
Look from the principle, compress progression to be close to more more more compress at isotherm, its efficiency is taller. If consider the pressure loss of intermediate condenser and axis,enclose what buy arises to divulge, the difference that 2 class reduce the efficiency that reduces with 3 class is about 3.5% , the difference that 3 class reduce the efficiency that reduces with 4 class is about 1% .
As a result of the progress that fluid numerical value analyses, its processing software is already nonexistent buy a doorsill, because manufacturer of this old brand accumulates the dominant position of the respect in technology and data,had disappeared. The efficiency of impeller monomer also is achieved 95% , already did not improve margin how oldly.
Because do screw to the contact of the screw of compressor and screw can scorch and be damaged, because this is right the management of precision is very fundamental, but although nominal contact also will not scorch and the impeller of centrifugal type compressor produces an accident with spiral case happening. Because the impeller in movement leaves the deformation of the deformation that mental efforts causes or spiral case, the exit of the impeller when causing actual movement is not put in aperture. If junior travel fractionation ends to examine in movement, most circumstance leaves the mark that can acknowledge slight contact. That is to say its structure is very safe.
The air that quickens to impeller has slowdown, transform the device that is pressure is called diffuser.
If do not take blade (without blade type) criterion air flows along circumferential direction more, reach downstream eddy room (spiral case) the distance lengthens. Popularly, it is edge radius direction to shorten through installing stationary lamina to change air current point of view the space that pass, reduce the attrition loss of access. Type of channel of this access existence, blade type, wait without blade type.
The Xiaozhan great that the professor of benefit of peaceful of younger sister end of university of a poetic name of China announced his to develop in ASME 1983 compares blade diffuser (low density) , very practical inside efficiency and discharge limits, got be adoptioned extensively of the whole world. Professor of benefit of peaceful of younger sister end is in at that time not patent application counterpoises, because this technology is alive,use inside bound limits unlimited.
Hydromechanical in the center, wanting to airy decelerate is more difficult than quickening. Because of the improved development of this diffuser difficulty wants prep above to rotate the development of impeller, using the caustic break an appointment that go up actually to be in at present 10% the left and right sides, still put in ascensive space, remain further development is improved.
2, the characteristic of centrifugal type compressor
1, breathe heavily brace up
The asthma that centrifugal type compressor has cubage type place to be not had brace up characteristic.
When discharge reduces a certain limit, diffuser and impeller can appear stall (Stall) , downstream air begins refluent upstream. Below this discharge bounds, exhaust side air produces total volume refluent, downstream compressed8 air expands quickly in upper reaches, can produce explosive sound. Should make the pressure of exhaust side drops quickly upstream, rise again after and happen again refluent, phenomenon of this kind of oscillation is called the asthma of turbine brace up.
Because cause the stall that the reason of this phenomenon is diffuser or impeller, because this wants a consideration,prevent the method of this stall. Below the circumstance that the kinetic energy that brings to bear on in impeller is transformed to be pressure ceaselessly, the reason of stall is too big slowdown. Once happen,reduce an amount, this kind of general reducer meets diffuser most begin stall first, some designs appear likely also impeller first the circumstance of stall.
Impeller is a kind of air is quickened machine, do not think its can appear commonly stall, but if if come relative to speed from impeller and airy,considering, appear possibly also in impeller decelerate. If want to avoid stall as far as possible, the decelerate that can reduce diffuser or impeller is compared, but the length that can increase radius direction to go up so, the attrition loss inside access can increase as the addition of this length into scale. How to narrow the carapace that take energy of life (spiral case) come effectively decelerate, it is the key that improves centrifugal function technology. Also grow what do not take blade quite without distance of access of blade type diffuser, the loss can increase, but on the other hand its decelerate takes blade form than wanting to compare small, because of this not incidental stall.
Below same condition, revolution is not changed when running namely and reduce flow, raise pressure to compare, the exhaust temperature of compressor of dry screw can rise, screw can scorch injury, accordingly its contain exhaust temperature to rise to spark namely stop the safe unit of machine. Centrifugal type compressor also is contained avoid to breathe heavily brace up control equipment, but although controlled invalidation to appear to breathe heavily brace up, also won’t cause loss commonly, it can cross temperature of big or refluent air to inlet temperature rises and stop namely because of vibration machine.
2, discharge adjusting range
The characteristic of centrifugal type compressor is, take gas a powerful person through narrowing, can decrease not only into tolerance, still can move to use a site, reduce inlet pressure in order to reduce the heighten of pressure ratio. And the key that holds adjusting range, depend on how avoiding aforementioned to breathe heavily brace up.
Want to go after highest efficiency, can increase the decelerate capacity of impeller and diffuser, reduce access loss, but because of discharge decrease to be able to appear very quickly stall. In principle, pursueing highest efficiency and adjusting range of the largest flow at the same time is contradictory. The product in the market was forced to make fair compromise.
It is very mature already that refrigeration agent or supercharger of car engine turbine enlarge technology of discharge adjusting range mediumly, technology of the diffuser bypass technology that prevents diffuser stall, diffuser reduce expenditure and the technology that prevent impeller to import partial stall already had relevant product.
These technologies can enlarge the discharge adjusting range of centrifugal type compressor, make centrifugal type compressor sets stock effect ground and compressor of screw of frequency conversion type to have confrontation as a kind of capacity adjustment.
3, the actor defect of centrifugal type compressor
① did not wear away, safeguard cost to be in compressor lowest;
② and screw type compressor are compared, aperture arises divulge little, because this is odd the efficiency of class is tall;
③ and compressor of dry type screw are compared, spare parts amount and treatment industry duration are little, treatment precision demand is not high, manufacturing cost is low.
Compressor stops with expand in heat when movement or deformation can happen below stress, aperture can produce change.
Two screw of dry screw compressor with the face opposite, because its characteristic is in a way,the contact can form surface contact, cause calorific expand, scorch and get stuck dead, and on the other hand, the characteristic with centrifugal type the biggest compressor, it is impeller blades and spiral case be with the line opposite, although produce a certain number of contacts,also be line contact accordingly, if blade has delimited like bit, won’t scorch. Accordingly, its biggest advantage is an accident get lesser than doing type screw compressor to want much.
Part of ① air access (impeller and diffuser) exterior pollution can bring about function to reduce
Function can be reduced about 10% the left and right sides. But use up power to also can decrease. Because airy speed is every second hundreds meters, because the crude rate of this interface surface has tremendous effect to function, especially the contaminative impact of the diffuser part with the rapiddest velocity of flow is the biggest. Of course, except pollution, corrode same meeting makes the surface rough and reduce performance.
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Want to solve this problem, can carry what headroom enrages filter to filter precision, and fixed executive interior (impeller and diffuser) sweep. In addition, the function of inhaler of centrifugal type compressor wants prep above commonly other type, and have very large area to prolong the life of filter core, some users are used than gas turbine (gas turbine also is machinery of a kind of turbine, because this has identical drawback) the filter with higher performance will prevent function reduce, its filter core can be twined automatically also facilitate safeguard. The method that early of shipping turbine supercharger cleans impeller and diffuser with respect to water of will regular in season was thrown practical, but this method was not used in land turbine machinery it seems that, the user also does not pay close attention to this.
Investment of ② initial stage is high
Screw type and the commercial pattern that piston compresses aircraft manufacturer are support safeguard cost to receive profit back and forth, because this can give out inferior price. But centrifugal type compressor does not have too much maintenance project, accordingly although manufacturing cost is low, also must raise high price.