Rotary kinetic fluid motors or pumps – With means for re-entry of working fluid to blade set – Pump priming means
Reexamination Certificate
2002-02-06
2004-04-27
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
With means for re-entry of working fluid to blade set
Pump priming means
C415S057400, C415S058300, C415S058600
Reexamination Certificate
active
06726441
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a compressor, in particular for an internal combustion engine, with a compressor wheel disposed in a compressor flow duct and a recirculation structure.
German patent publication DE 42 13 047 A1 discloses an exhaust gas turbocharger for an internal combustion engine which turbocharger comprises a compressor driven by an exhaust gas turbine. For increasing the compressor working range, the compressor is equipped with a characteristic-diagram stabilization means for displacing the surge limit and the fill limit of the compressor. The characteristic-diagram stabilization means consists of a bypass in relation to the compressor flow duct in the compressor casing, which bypass extends approximately parallel to the compressor flow duct and bridges the inlet area of the compressor wheel. The bypass has the function of a recirculation device, by means of which a part of the mass flow entering the compressor can be returned in the opposite direction to the general flow direction, with the result that the surge limit of the compressor is displaced in favor of a greater working range.
The fill limit can also be changed in order to increase the power of the compressor or of the motor. The flow cross section of the compressor flow duct is enlarged via the bypass, so that additional intake air can be supplied to the compressor. The fill limit is thereby displaced in the direction of greater mass flows.
The geometry of the bypass has a decisive influence on the formation of the re-circulation flow when the compressor is operating near the surge limit. For an improved return flow through the bypass, it was proposed, for example in U.S. Pat. No. 4,122,585, to provide an annular bypass flow structure surrounding the compressor wheel and having a multiplicity of flow passages which are distributed over the circumference and extend approximately tangentially in the swirling direction of the compressor wheel. Each flow passage extends axially over a portion of the compressor wheel and bridges the compressor-wheel inlet area, so that circulating combustion air can be returned axially, via the flow passages, into the region upstream of the compressor-wheel inlet.
One disadvantage of this device, however, is that the tangential swirl of the recirculation flow can be utilized only inadequately for forming and maintaining a circulating mass flow, because the flow ducts are closed on their radially outer sides and the mass flow flowing into the tangential flow ducts is deflected, at the end of the flow ducts, in the direction opposite to the compressor inflow direction.
It is the object of the present invention to provide a compressor, which can be operated in a wide operating range, by means of simple structural means.
SUMMARY OF THE INVENTION
In an air compressor, particularly for an internal combustion engine, which has a compressor housing with a flow duct structure and a recirculation arrangement including a bypass structure for recirculation some of the air entering the compressor wheel, a recirculating ring is arranged in the bypass flow structure around the compressor wheel and the ring has a plurality of flow passages distributed uniformly around its circumference with inflow orifices at the radial inner end in communication with the compressor flow duct and outflow orifice at the radial outer end in communication with a by-pass flow space.
It is thereby possible for the returned exhaust gas mass flow to be guided through the circulation ring radially from the inside outwards and to flow into the bypass flow space which surrounds the recirculation ring radially. The mass flow introduced into the recirculation device flows, under the influence of the centrifugal co-swirl flow, through the recirculation ring with a radial component, is subsequently collected in the annular bypass flow space and is finally returned axially into the compressor flow duct. There is no repulsion, which would detrimentally affect the co-swirl flow.
The recirculation ring may be designed as a separate component, which is to be inserted into the bypass. The recirculation ring is dimensioned such that a bypass flow space remains in the bypass which flow space surrounds the recirculation ring radially for receiving the returning mass flow.
In an expedient embodiment, the flow passages in the recirculation ring extend axially only over a portion of the axial width of the ring. The mass flow introduced into the recirculation ring is thereby prevented from flowing out axially at the axially closed side of the ring, thus necessitating an outflow with a radial component. The recirculation ring is expediently provided with flow passages, which are delimited on the opposite axial sides of the ring by wall portions, so that any axial inflow and outflow are prevented. As a result, flow turbulences can be avoided, and the co-swirl flow generated as a result of the rotation of the compressor wheel can be utilized optimally for the radial flow through the recirculation ring.
Advantageously, at least some of the flow passages extend rectilinearly, whereby manufacturing is simplified. Additionally or alternatively, however, it may also be expedient to make some or all of the flow ducts curved, wherein the curvature of the flow passages preferably follows the curvature of the compressor wheel. If both, rectilinear and curved, flow passages are provided, it may be advantageous, for the purpose of simplifying the production process, if the passages have a cross-section, which is constant over their length. It may also be expedient, however, to provide a flow cross-section, which narrows toward the radially outer end of the recirculation ring, whereby a nozzle effect is achieved for the recirculation flow.
The flow passages preferably extend in the swirling direction, the outflow orifice being arranged so as to be offset relative to the inflow orifice in the direction of the rotation of the compressor wheel. This results in the flow passages extending approximately tangentially with a radial component, so that the flow passages form an angle with the radial direction. In the case of a rectilinear design of the flow passages, the angle between the longitudinal axis of the flow passages and a tangent to the annular inside of the recirculation ring is advantageously about 20° to 60°. By contrast, with a curved flow passage, it may be expedient to provide the gradient of the flow passage in the region of its inflow orifice relative to the tangent to the annular inside of the recirculation ring with an inlet angle of 20° to 60° and the gradient in the region of the outflow orifice relative to a tangent to the annular outside of the recirculation ring with an outlet angle of between 10° and 50°. The outlet angle is smaller than the inlet angle, the outlet angle typically having a value of about 10° and the inlet angle a value of about 60°.
The invention will become more readily apparent from the following description of preferred embodiments, thereof shown, by way of example in the accompanying drawings.
REFERENCES:
patent: 4212585 (1980-07-01), Swarden et al.
patent: 4930979 (1990-06-01), Fisher et al.
patent: 6447241 (2002-09-01), Nakao
patent: 42 13 047 (1993-10-01), None
patent: 198 23 274 (1999-10-01), None
patent: 2 220 447 (1990-01-01), None
patent: 2 363 427 (2001-12-01), None
Erdmann Wolfgang
Finger Helmut
Fledersbacher Peter
Sumser Siegfried
Wirbeleit Friedrich
Bach Klaus J.
Daimler Chrysler AG
Look Edward K.
White Dwayne J.
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