GB2060074A

GB2060074A - Ejector Assembly

Info

Publication number: GB2060074A
Application number: GB8018627A
Authority: GB
Original assignee: Avco Corp
Current assignee: Avco Corp
Priority date: 1979-05-08
Filing date: 1979-05-08
Publication date: 1981-04-29
Also published as: DE2918873A1; GB2060074B; DE2918873C2

Abstract

In a gas turbine engine an auxiliary airflow is provided to power accessories. This auxiliary airflow is obtained from a bleed aperture 7 which is constructed immediately downstream of a diffuser vane 3. This high energy air from the diffuser 1 is used as the primary airflow in an ejector 10 to draw ambient air into the auxiliary airflow to lower the temperature of the bleed air. The ejector is constructed to adjust the amount of ambient air automatically according to the energy of the bleed airflow by means of a piston actuated spike 13 mounted for sliding movement in the primary nozzle 11. The spike 13 varies the volume of flow through the primary nozzle 11 according to the pressure exerted by the airflow on the piston. <IMAGE>

Description

at the trailing edge 5. A bleed aperture 7 is constructed in the wall of diffuser 1 within the cusp 6 in the trailing edge 5 of one, some or all of the diffuser vanes 3. The bleed aperture 7 connects to a bleed flow manifold 8 and is designed to allow high energy air within the cusp region of the diffuser vane 3 to flow into the bleed manifold 8.

Attention is drawn to our co-pending application No. 7915817 from which the present application has been divided.

An auxiliary airflow duct 9 communicates directly with the bleed manifold 8. An ejector nozzle assembly 10, as shown in figure 2, is constructed in the auxiliary duct 9 so that the bleed air forms the primary flow through the primary nozzle 11 of the ejector 10. Cooler ambient air is obtained from outside of the engine through the secondary nozzle 12 of the ejector 10. The primary nozzle 11 is controlled by a spike 1 3 which is axially movable within the nozzle 10.

The rearward portion 14 of the spike 13 is formed as a piston which translates within a closed chamber 1 5. The piston 14 is biased by spring 1 6 to provide maximum primary airflow. The pressure in the bleed manifold 8 forces air through an opening 17 into a well 18 of the chamber 1 5 and exerts a force on one side of the piston 14 against the biasing spring 1 6 to cause movement of the spike 13 to reduce the primary airflow, thereby controlling the ratio of the primary to the secondary air.

In operation, high energy air exits through the bleed aperture 7 at the trailing edge 5 of the diffuser vane 3 and enters the bleed manifold 8 which supplies the auxiliary duct 9. At low engine speeds the bleed air is at relatively low energy and the ejector nozzle 10 is set for maximum primary flow essentially eliminating the introduction of ambient air. As engine speeds increase the higher energy bleed air exerts a force on the spike 1 3 against its biasing spring 1 6 to translate the spike 13 in a direction which reduces the amount of primary air flowing in the primary nozzle 11. As this happens secondary airflow increases causing an auxiliary airflow of reduced temperature suitable to driving accessory devices.

The curved surface of the cusp 6 constructed in the trailing edge 5 of the diffuser vane 3 requires the bleed airflow to turn sharply in order to exit through the aperture 7. This creates a centrifugal inertial separation effect which substantially eliminates contaminants in the bleed air stream, thereby eliminating the need for further separation of filtering of the auxiliary airflow.

Claims

1. An ejector assembly having a primary and secondary nozzle comprising: an elongated spike mounted for axial sliding motion within the primary nozzle and shaped so that this motion tends to vary the amount of airflow in the primary nozzle; SPECIFICATION Ejector Assembly This invention relates to gas turbine engines and more particularly to bleed apertures to provide auxiliary air flow.

In some instances it is necessary in a gas turbine engine to have a source of airflow to perform auxiliary functions and drive accessory devices; for example to generate electricity, drive air conditioning and to pressurize passenger areas. In general, this airflow must be free from contamination and is supplied from bleed air obtained at various locations in the engine.

Depending on the stage at which the bleed air is obtained various problems occur, namely, contamination, insufficient energy, excessive energy loss within the engine itself or excessive temperature of the bleed air.

An object is to provide an ejector assembly constructed to provide a secondary airflow which varies in inverse relationship to the pressure in the primary nozzle.

According to the invention, there is provided an ejector assembly having a primary and secondary nozzle comprising: an elongated spike mounted for axial sliding motion within the primary nozzle and shaped so that this motion tends to vary the amount of airflow in the primary nozzle; a sealed chamber constructed within the primary nozzle; a piston fixed to the nozzle spike for movement therewith and extending into the sealed chamber; a biasing spring operatively associated with the piston to bias the piston and spike in a position for maximum primary airflow; and means to expose one side of the piston to a force proportional to the pressure of the air in the primary nozzle so that increased pressure will cause movement of the piston and spike to reduce the primary airflow.

The cooler ambient air forms the secondary airflow of the ejector and combines with the primary airflow to lower the temperature thereof.

In this manner, a high energy, temperature controlled, auxiliary airflow is provided.

This invention will be further described in more detail below with reference to the accompanying drawings, in which: Figure 1 is a sectional view of a gas turbine engine incorporating an ejector according to one form of the present invention; and Figure 2 is a sectional view of the ejector nozzle.

In a gas turbine engine an annular diffuser 1, as shown in figure 1, receives high energy airflow from a centrifugal compressor impeller 2. The diffuser 1 is constructed with radially extending vanes 3 constructed across the diffuser channel.

The vanes 3 gradually expand in width from their forward edge 4 to the downstream edge 5. A curved cusp 6 is machined into the trailing edge 5 of the diffuser vane 3 in order to minimze the wake caused by the vane 3 and to induce a vortex

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. at the trailing edge 5. A bleed aperture 7 is constructed in the wall of diffuser 1 within the cusp 6 in the trailing edge 5 of one, some or all of the diffuser vanes 3. The bleed aperture 7 connects to a bleed flow manifold 8 and is designed to allow high energy air within the cusp region of the diffuser vane 3 to flow into the bleed manifold 8. Attention is drawn to our co-pending application No. 7915817 from which the present application has been divided. An auxiliary airflow duct 9 communicates directly with the bleed manifold 8. An ejector nozzle assembly 10, as shown in figure 2, is constructed in the auxiliary duct 9 so that the bleed air forms the primary flow through the primary nozzle 11 of the ejector 10. Cooler ambient air is obtained from outside of the engine through the secondary nozzle 12 of the ejector 10. The primary nozzle 11 is controlled by a spike 1 3 which is axially movable within the nozzle 10. The rearward portion 14 of the spike 13 is formed as a piston which translates within a closed chamber 1 5. The piston 14 is biased by spring 1 6 to provide maximum primary airflow. The pressure in the bleed manifold 8 forces air through an opening 17 into a well 18 of the chamber 1 5 and exerts a force on one side of the piston 14 against the biasing spring 1 6 to cause movement of the spike 13 to reduce the primary airflow, thereby controlling the ratio of the primary to the secondary air. In operation, high energy air exits through the bleed aperture 7 at the trailing edge 5 of the diffuser vane 3 and enters the bleed manifold 8 which supplies the auxiliary duct 9. At low engine speeds the bleed air is at relatively low energy and the ejector nozzle 10 is set for maximum primary flow essentially eliminating the introduction of ambient air. As engine speeds increase the higher energy bleed air exerts a force on the spike 1 3 against its biasing spring 1 6 to translate the spike 13 in a direction which reduces the amount of primary air flowing in the primary nozzle 11. As this happens secondary airflow increases causing an auxiliary airflow of reduced temperature suitable to driving accessory devices. The curved surface of the cusp 6 constructed in the trailing edge 5 of the diffuser vane 3 requires the bleed airflow to turn sharply in order to exit through the aperture 7. This creates a centrifugal inertial separation effect which substantially eliminates contaminants in the bleed air stream, thereby eliminating the need for further separation of filtering of the auxiliary airflow. Claims

The vanes 3 gradually expand in width from their forward edge 4 to the downstream edge 5. A curved cusp 6 is machined into the trailing edge 5 of the diffuser vane 3 in order to minimze the wake caused by the vane 3 and to induce a vortex a sealed chamber constructed within the primary nozzle; a piston fixed to the nozzle spike for movement therewith and extending into the sealed chamber; a biasing spring operatively associated with the piston to bias the piston and spike in a position for maximum primary airflow; and means to expose one side of the piston to a force proportional to the pressure of the air in the primary nozzle so that increased pressure will cause movement of the piston and spike to reduce the primary airflow.

2. An ejector assembly substantially as hereinbefore described with reference to the accompanying drawings.