DD289797A5

DD289797A5 - RADIAL COMPRESSOR WHEEL

Info

Publication number: DD289797A5
Application number: DD33518289A
Authority: DD
Inventors: Roland Obst
Original assignee: Kombinat Pumpen Und Verdichter,De; Stammbetrieb Pumpenwerke Halle,De
Priority date: 1989-12-04
Filing date: 1989-12-04
Publication date: 1991-05-08

Abstract

Die Erfindung betrifft ein Radialverdichterlaufrad mit Deckscheibe und verwundenen, in den axialen Einlauf vorgezogenen Schaufeln, das vorzugsweise durch Schweiszen hergestellt ist. Aufgabe der Erfindung ist es, die ueblicherweise sehr hohen Fliehkraftspannungen an den Schaufeleintrittskanten in der Naehe der Schweisznaht zur Radscheibe zu reduzieren. Geloest wird die Aufgabe dadurch, dasz die in die Schaufeln, insbesondere im Bereich der radscheibenseitigen Schweisznaht am Laufradeintritt, eine Vorspannung eingebracht ist, die entgegengesetzt zu der Spannung im Betriebszustand gerichtet und vom Betrag her kleiner als die zulaessige Spannung ist, wobei die Kontur der Deckscheibe im Vergleich zur Kontur der Schaufeln derart ist, dasz beim Aufsetzen der Deckscheibe diese zuerst im Eintrittsbereich an den Schaufeln anliegt, waehrend im Austrittsbereich ein Spalt entsteht.{Radialverdichterlaufrad; Vorspannung; Schaufeln; Spannungsreduzierung}The invention relates to a radial compressor impeller with cover disk and twisted, in the axial inlet preferred blades, which is preferably made by welding. The object of the invention is to reduce the usually very high centrifugal force stresses at the blade leading edges in the vicinity of the weld seam to the wheel disc. The object is achieved by introducing a prestress into the blades, in particular in the area of the wheel-disk-side weld seam at the impeller, which is opposite to the tension in the operating condition and smaller in magnitude than the permissible tension, the contour of the cover disk in comparison to the contour of the blades is such that when placing the cover disc, this first rests against the blades in the inlet region, while in the outlet region, a gap is formed {radial compressor impeller; Preload; blades; Voltage reduction}

Description

der Schaufeln derart ist, daß beim Aufsetzen der Deckscheibe diese zuerst im Eintrittsbereich an den Schaufeln anliegt, während im Austrittsbereich ein Spalt entsteht. Ein weiteres Erfindungsmerkmal besteht darin, daß der im Austrittsbereich entstehende Spalt vor dem Schweißen infolge axialer Kräfte zwischen Radscheibe und Deckscheibe überwunden und eine Verformung der Schaufeln im Eintrittsbereich erzwungen wird.the blades is such that when placing the cover disc, this first rests against the blades in the inlet region, while a gap is created in the outlet region. Another feature of the invention is that the gap formed in the outlet region is overcome before welding due to axial forces between the wheel disc and the cover plate and a deformation of the blades is forced in the inlet region.

Ausführungsbeispielembodiment

Die Erfindung wird an einem Ausführungsbeispiel näher erläutert. Bei der Radfortigung werden die Schaufeln unter eine definierte Vorspannung gebracht. Dabei muß diese Vorspannung von der Richtung her entgegengesetzt der Spannung im Betriebszustand und vom Betrag kleiner als die zulässige Spannung sein. Bei Rotation des Rades wird dann mit steigender Drehzahl durch die Fliehkraft zuerst diese Vorspannung abgebaut, bevor sich je nach Größe der Vorspannung ein Spannungszustand in Richtung der Fliehkraftbelastung aufbaut. Damit liegen im Betriebszustand in den Schaufeln Spannungen vor, die im Vergleich zur nicht vorgespannten Schaufel um die Größe der Vorspannung reduziert wird. Das Eindringen der Vorspannung erfolgt vorzugsweise durch eine Korrektur der Deckscheibenkontur 1, speziell im Eintrittsbereich, wodurch beim Aufsetzen der Deckscheibe 1 diese zuerst im Eintrittsbereich der Schaufeln 5 anliegt, während im Austrittsbereich ein Spalt 3 entsteht, Fig. 1.The invention will be explained in more detail using an exemplary embodiment. When Radfortigung the blades are placed under a defined bias. In this case, this bias must be opposite to the direction of the voltage in the operating state and the amount less than the allowable voltage. Upon rotation of the wheel is then reduced with increasing speed by the centrifugal force first this bias before builds up depending on the size of the bias voltage state in the direction of centrifugal force. Thus, in the operating condition, there are stresses in the blades, which are reduced by the magnitude of the preload in comparison to the non-prestressed blade. The penetration of the prestressing is preferably effected by a correction of the cover disk contour 1, especially in the entry region, whereby when the cover disk 1 is put on, it first rests in the inlet region of the blades 5, while a gap 3 is created in the outlet region, FIG.

Durch axiales Verspannen von Radscheibe 2 und Deckscheibe 1 vor dem Schweißen wird der Spalt 3 überbrückt. Dabei weichen die Schaufeln 5 im Eintrittsbereich 4 entsp rechend ihrer Verwindung seitlich aus und liegen unter Druck fest an der Deckccheibe 1 an, Fig. 2.By axial bracing of wheel disc 2 and cover plate 1 before welding the gap 3 is bridged. In this case, the blades 5 in the inlet region 4 deviate from their twist laterally and are under pressure firmly against the cover plate 1, Fig. 2.

Claims

Claim:

1. Radial compressor impeller with cover disk and twisted, in the axial inlet preferred blades, preferably produced by welding, characterized in that in the blades (5), in particular in the region of the wheel disc side weld at the impeller inlet (4), a bias is introduced, the is opposite to the voltage in the operating state and the amount is smaller than the allowable voltage, wherein the contour of the cover plate (1) compared to the contour of the blades (5) is such that when placing the cover plate (1) this first in Entry region (4) rests against the blades, while in the exit region, a gap (3) is formed.

2. Radial compressor impeller according to claim 1, characterized in that the gap formed in the outlet region (3) before welding due to axial forces between the wheel disc (2) and cover plate (1) overcome and forced deformation of the blades (5) in the inlet region (4) becomes.

For this 1 page drawings

Field of application of the invention

The invention relates to a radial compressor impeller with cover disk and twisted, in the axial inlet preferred blades, which is preferably made by welding.

Characteristic of the known state of the art

In the production of centrifugal compressor impellers with shroud two basic versions can be distinguished.

Version 1

Shovels and shroud are completely connected to each other, eg. B. by casting, welding or soldering.

Execution 2

In the entry area, the blades are not connected to the cover plate, z. B. in the case of a welded construction. Additional loads on the blades by the radial expansion of the cover plate are thereby avoided. In the hitherto customary technology for wheels according to embodiment 2, after the blades have been welded onto the wheel disk, the cover-disk-side meridian contour of the blades is rotated. Subsequently, the centric placement and welding of the cover plate, whereby in each case only a limited opposite of the flow direction is welded from the impeller outlet. Remaining gaps between the blades and the cover plate in the entry area can not be ruled out. In addition, upon rotation of the impeller, a radial expansion of the cover plate and thus an enlargement of this column. Under the influence of centrifugal force, a twisted blade, which has been pulled forward into the axial intake, is usually supported on the cover disk. This is associated with a deformation of the blades, especially at the blade entrance, to overcome the mentioned gap between the cover plate side meridian contour of the blade and shroud. These deformations lead to an increased bending stress of the blades in the region of the wheel-disk-side weld seam. In DE-PS 937120 an impeller for a centrifugal compressor is presented, which includes the voltage reduction. The stress reduction refers to the highly stressed cover disk. For this purpose, an axial gap between the blade and cover plate is provided in the impeller inlet region, which is overcome by axial forces to achieve a bias in the cover plate. This design is conceivable only for unbound, straight or cylindrical blades. The axial strain must constantly by special devices, eg. B. tie rods, are maintained. The cover plate is formed as a plate spring is relatively thin and also has no thickening in the suction, so that a significant deformation of the cover plate will occur due to the axial strain.

Aim of the invention

The invention sets itself the goal of reducing the high bending stress in the blades in the operating state.

Explanation of the essence of the invention

The invention has for its object to reduce the usually very high centrifugal force stresses at the blade entry edges in the vicinity of the weld to the wheel disc.

According to the invention the object is achieved in that in the blades, in particular in the region of the wheel disc side weld at the impeller inlet, a bias is introduced, which is opposite to the voltage in the operating state