国外单螺杆压缩机

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Figure 1: Compression process in a single-screw compressor

Suction: During rotation of the main rotor, a typical groove in open communication with the suction chamber gradually fills with suction gas. The tooth of the gaterotor in mesh with the groove acts as an aspiring piston.

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Compression: As the main rotor turns, the groove engages a tooth on the gaterotor and is covered simultaneously by the cylindrical main rotor casing. The gas is trapped in the space formed by the three sides of the groove, the casing, and the gaterotor tooth. As rotation continues, the groove volume decreases and compression occurs.

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Discharge: At the geometrically fixed point where the leading edge of the groove and the edge of the discharge port coincide, compression ceases, and the gas discharges into the delivery line until the groove volume has been reduced to zero

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Source: Text from and illustrations adapted from 1992 ASHRAE Systems and Equipment Handbook; photo courtesy of McQuay

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SINGLE SCREW COMPRESSOR

The Vilter Single Screw Compressor is the newest concept in screw compressor technology, and it’s Vilter’s latest release in a long, respected line of compressors used for industrial cooling applications. Vilter was the first company in North America to receive a license to manufacture a Single Screw Compressor for industrial refrigeration and air conditioning applications, and the first to go to market. 1 ]# v# l& R) BVilter’s Single Screw Compressor is a rotary, oil injected, positive displacement machine that can operate with any of the commonly used industrial refrigerants. It consists of a cylindrical main screw with six helical grooves and two planar gaterotors. The gaterotors engage with the main screw to form the compressor chamber. 5 C; X5 @; Z, M$ ~. g' I) DVilter can provide Single Screw Compressor models with displacements ranging from 100 CFM to 1800 CFM.

Reciprocating Compressor

You can choose from a complete line of reciprocating compressors in 2 through 16-cylinder sizes for both direct-drive and V-belt operation. CFM displacements range from 80 to 800 with capacity reduction steps for efficient operation available with every model size. Our most popular reciprocating compressor model is the versatile 450XL?It's designed to use virtually any industrial refrigerant, operating at compression ratios of up to 8:1 with ammonia and up to 12:1 with some halocarbons. The 450XL? like all new Vilter reciprocating compressor models, is backed by Vilter's standard 2-year reciprocating compressor warranty.

The 450XL?incorporates the latest advancements in refrigeration compressor technology. It's designed to accommodate up to 300 bhp with belt-drive or up to 375 bhp with direct-drive—and it's capable of operating at pressure differentials up to 250 psi, actual discharge pressures to 350 psig and suction pressures to 150 psig. That makes the 450XL?ideal for the air conditioning and heat pump fields, as well as a wide range of refrigeration applications.

Other reciprocating compressor models include the popular 440, long recognized as the "workhorse of the industry;" the 350ES, designed specifically for industrial and commercial halocarbon applications; and the 32O, our compact open-type air conditioning compressor.

MICROPROCESSOR

The Vilter Central Computer Control system utilizes the concept of distributed control to provide a flexible and reliable refrigeration control system. The Windows based graphical user interface is the most advanced in the industry.

With the easy to use mouse-driven Vilter color graphic software, the operator can instantly view the operation of all system components, change system parameters, generate reports and do graphical analysis. The Vilter software has been kept easy to learn and understand by incorporating a minimum number of consistently named buttons.

EVAPORATIVE CONDENSERS

Vilter offers a wide variety of types and size of evaporative condenser to fill specific application requirements. Centrifugal fan models quiet operation; Vilter Power Pincher?propeller fan models offer energy-saving operation.

VGC and VGF models are completely hot-dip galvanized after fabrication with zinc deposition four times that of mill sheets. All models have a liberal coil surface with built-in gravity drain. One-piece construction reduces installation time and cost.

Evaporative condenser capacities range from 40-600 tons and can be used with refrigerants R22, ammonia and the new HFC's.

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Helical rotary (or screw) compressors are positive displacement machines. Two types are used - single-screw and twin-screw. A twin-screw compressor consists of accurately matched rotors (one male and one female) that mesh closely when rotating within a close tolerance common housing. One rotor is driven while the other turns in a counter-rotating motion.

A single-screw compressor uses a single main screw rotor meshing with two gate rotors with matching teeth. The main screw is driven by the prime mover, typically an electric motor. The gate rotors may be metal or a composite material. The screw-like grooves gather vapors from the intake port, trap them in the pockets between the grooves and compressor housing, and force them to the discharge port along the meshing point path. This action raises the trapped gas pressure to the discharge pressure. If the power input is adequate and pressure differential between outlet and inlet pressures is within the design range of the machine, the screw compressor delivers the appropriate refrigerant gas volume.

Notice that the refrigerant gas enters and exits the compressor through ports; not valves like reciprocating compressors. Compressors of this type are called ported compressors for this reason. The mating rotors are rotating at such close tolerances, they require cooling and lubrication. This may be provided by forcing oil into the compressor at strategic points. The oil also acts as a seal for rotor-to-rotor and rotor-to-housing clearances.

The oil is entrained by the flowing refrigerant gas, leaves the compressor, and is recovered by an oil separator for reuse (after cooling and filtering). Since the oil sump is on the high pressure side of the system, a mechanical pump is not required for oil circulation. The compressive action of the screw itself provide the necessary pressure differential.

In other designs, subcooled liquid refrigerant injection (instead of oil) cools and seals the compressor. The use of liquid refrigerant eliminates oil management problems as there are no oil separators or oil recovery systems. The system is sealed, cooled and lubricated with liquid refrigerant which also attenuates the noise. Capacity is controlled with two slide valves.

Since the screw compressor is most often driven by a constant speed electric motor and the screw compressor is a positive displacement machine, the natural tendency is to move a fixed volume of refrigerant gas. This would make refrigeration capacity control difficult. The design uses a slide valve that opens to vent some gas back to the suction port, reducing both the net gas flow and power input.

Several manufacturers offer packaged water chillers using helical rotary or "screw" compressors. Water-cooled units range in size from 50 tons to over 1200 tons. They normally use HCFC-22 and HFC134a as refrigerants in space cooling designs and ammonia in process refrigeration (particularly food processing). In the smaller sizes, they compete with reciprocating chillers. In larger sizes they compete with centrifugals. Screw compressors usually employ hermetic or semi-hermetic designs for higher efficiency, minimum leakage, ease of service, and volume production reasons.

Air- and evaporatively-cooled models can be used from about 60 to 350 tons, and can use open-drives. Chillers using ammonia always use open type compressors, typically with direct-coupled electric motors. The selection of open or hermetic design depends on the application, refrigerant, and the manufacturer. ; W3 `$ W6 Y/ j' e$ z N- k

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三、设计实例 # W* L" W4 N+ x$ j7 U . t7 i4 ?) F8 g" F. [ 单螺杆压缩机星轮的转角α＝57.7°，β＝31.5°。按上述步骤进行一个螺杆槽造型如图9所示。再通过布尔运算得到单槽螺杆，如图10所示。然后将此螺杆槽的特征进行6等分圆周阵列，得到整个螺杆造型。如图11所示。

图9 通过逆向反求的槽底

图10 单槽的螺杆

图11 螺杆的完整造型

四、结论 * h# O' r! k7 J ^2 Y) g3 j 借助逆向工程软件，成功实现了单螺杆压缩机螺杆的精确三维造型，为以后利用Ciamtron的五轴加工提供了精确模型，大大提高了产品设计的效率，为项目的最终顺利完成奠定了坚实的基础。

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二、解决问题的思路和方法 7 z. | H6 c( w. z1 r6 ~ 我们通过计算程序得到螺杆一个槽的许多坐标点，然后用Cimatron的逆向工程模块对螺杆的一个槽进行较精确的设计。接下来将此槽的特征进行6等分圆周阵列，即可得到整个螺杆的造型。具体步骤如下。 3 Q$ B, i- T n& _ （1）按星轮的截面尺寸和外形尺寸(外圆)对星轮进行精确三维造型（只造型一个齿），并存盘为star.pfm。 （2）按螺杆的外形尺寸进行螺杆的外形造型，并存盘为screw.pfm。 （3）用计算程序精确计算螺杆的一个槽的坐标点（3万多个点）。 （4）修改逆向工程的配置文件，在零件screw.par中用Cimatron直接读取坐标点文件，生成点云。如图7所示。

（5）用Cimatron的re_enge生成曲面。Re_enge提供了强大的点云编辑功能： 1）根据点云自动生成扫描线，即截面线； 9 y2 V! r, H+ A! y) A 2）对点云的点进行过滤、加密等编辑处理，使点更均匀； 3）对扫描线排序，将方向相反的扫描线调整过来； 4）根据扫描线，自动生产扫描面。即得到我们所需要的曲面的大致形状。如图8所示。

图8 扫描曲面

（6）通过Cimatron的曲面造型功能对曲面进行延伸、裁减等操作，得到螺杆的一个螺杆槽。再通过布尔运算得到一个螺槽的螺杆。 （7）将此螺杆槽的特征进行6等分圆周阵列，得到整个螺杆造型。 ! [* [+ C7 w1 k- P; U* O0 h

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单螺杆压缩机由两片星轮和一个螺杆组成，其中每片星轮有11齿，螺杆有6个槽。工作时，由螺杆带动星轮转动，且旋转轴相互垂直，螺杆和星轮的转速比为11∶6，如图4所示。星轮的齿截面较简单，造型也非常方便，如图5网格部分所示。 螺杆槽由星轮齿按包络原理形成，因而很难按常规方法对螺杆进行精确造型，只能通过数学模型计算出螺杆槽的坐标点后利用逆向工程反求。

图4 螺杆和星轮的装配关系

图5 星轮齿截面

图6 星轮齿顶与螺杆啮合角度

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De voordelen van de Single Screw compressor. % Y3 K7 C. v s' z- L$ p2 } 1. Een cyclus van aanzuig tot uitlaat wordt voltooid binnen een draaihoek van ca 160° van de schroefrotor. Het toerental van de rotor kan dus laag blijven terwijl de druk toch zeer snel opgebouwd wordt. Door deze snelle drukopbouw is de optredende spleetlekkage laag, resulterend in een hoog volumetrisch rendement. 2. Het opbouwen van de druk gebeurt symmetrisch aan beide zijden van de schroefrotor, de radiale belasting op de schroefrotor wordt daardoor gecompenseerd en uitgebalanceerd. Ook de axiale belasting op de schroefrotor is theoretisch nul omdat de compressiekamer gevormd wordt door één schroefrotor. 3. De kracht afkomstig van de compressiedruk staat haaks op de gate-rotoren, in de rotatierichting ondervinden ze daarom geen belasting vanuit deze druk. Hierdoor is er geen frictie tussen de gate-rotoren en de schroefrotor, de enige weerstand die de gate- rotoren ondervinden is afkomstig van de wentellagers. 4. De drukopbouw gebeurt 12 x in een omwenteling van de schroefrotor (2x6). Dit minimaliseert de luchtpulsatie, vibratie en geluid. Door de snelle drukopbouw kan het toerental laag blijven wat voordelen geeft in rendement, efficiency en levensduur. 5. Het materiaal van de gate-rotoren is een zeer speciale kunststof waardoor er geen metaal op metaal contact is. En door het in balans zijn van de compressiekrachten en het nagenoeg ontbreken van enigerlei weerstand in de gate-rotoren is er weinig vibratie en geluid. 6. Omdat de hoge efficiency van de Z-Screw® gerealiseerd wordt bij een laag toerental is het mogelijk om voor elk vermogen een apart schroefblok te ontwikkelen. Er zijn daarom geen tandwielkasten of speciale overbrengingen nodig. De schroefrotor kan dus zonder problemen direct aan de elektromotor gekoppeld worden. 0 x" O5 c$ g' W
9 r! I6 x* p' O! n. u2 LTechnische Wetenswaardigheden Sinds 1 januari 1978 zijn in Europa een aantal vertrouwde eenheden verboden, toen werd namelijk het Internationale Stelsel van Eenheden (algemeen aangeduid met SI) ingevoerd. De 7 grondeenheden van het SI stelsel zijn: Grootheid Eenheid Symbool massa kg (kilogram) m tijd s (seconde) t lengte m (meter) l elektrische stroom A (amperè) I temperatuur K (kelvin) K lichtsterkte cd (candela) I hoeveelheid stof mol n Maar ondanks het verbod op de oude eenheden zijn er een aantal die toch hardnekkig stand houden. Neem maar als voorbeeld een pond kaas of een ons ham, heel langzaam verdwijnen deze begrippen maar zelfs nu na twintig jaar worden ze nog overal dagelijks gebruikt. Een oude eenheid die onuitroeibaar schijnt is de paardekracht ofwel PK. / A, X; n4 _% W0 B- b3 u3 P0 V9 n9 jDeze eenheid kunnen we met recht ‘macho’ noemen, vraag maar eens naar het vermogen van iemands auto of motorfiets. ; O4 a z- V- R P0 k1 rOok in de persluchtwereld veranderen de eenheden langzaam. Op steeds meer manometers zien we echter toch dat de vertrouwde BAR is vervangen door PASCAL. Voor de meesten onder ons is dit niet een eenheid die je een gevoel van druk geeft. Daarom hieronder een klein rekenvoorbeeld. 1 bar = 100 kPa (is gelijk aan 100 x 1000 Pa) 1 meter waterkolom (mH2O) = 9,80665 kPa 10 mH2O = 98,0665 kPa # i# S/ u9 O4 `6 c& {$ IDus 1 bar is ongeveer gelijk aan 10 meter waterkolom Een manometer van 0 tot 10 bar die de druk in pascal aangeeft heeft dus als hoogste waarde 1 MPa (is gelijk aan 1000 kPa) " B8 G) N7 f* w1 MPa = 10 bar 8 V. @- `5 D+ J! M0 ?9 T0,9 MPa = 9 bar - }* ^3 o( y5 U- R; j+ A0,5 MPa = 5 bar ( J8 q. h* P/ D) @9 \+ Yenz. Onwillekeurig hebben we hierboven al twee voorvoegsels gebruikt zoals k voor kilo en M voor mega. ; T: s- ~9 I# @" M7 Y! bDeze voorvoegsels worden gebruikt om heel grote en zeer kleine getallen te vermijden, de volgende zijn dan ook o.a. gestandardiseerd: Voorvoegsel symbool factor Giga G 1000.000.000 Mega M 1000.000 Kilo k 1000 Hecto h 100 Deca da 10