CN112377267A

CN112377267A - Self-cooling high-speed ram air turbine generator

Info

Publication number: CN112377267A
Application number: CN202011375401.7A
Authority: CN
Inventors: 绳春晨; 谢洪涛; 高维浩; 罗高乔; 赵鑫
Original assignee: China Electronics Technology Group Corp No 16 Institute
Current assignee: China Electronics Technology Group Corp No 16 Institute
Priority date: 2020-11-30
Filing date: 2020-11-30
Publication date: 2021-02-19
Anticipated expiration: 2040-11-30
Also published as: CN112377267B

Abstract

The invention discloses a self-cooling high-speed ram air turbine generator, wherein a generator stator coil is fixedly connected in a shell of the self-cooling high-speed ram air turbine generator, and a rotor mandrel is rotationally connected in the shell of the self-cooling high-speed ram air turbine generator; the rotor core shaft is fixedly connected with generator rotor magnetic steel which is positioned in a generator stator coil; the generator turbine adopts a centripetal radial-axial flow impeller form, supplies air through a radial cascade, has small axial through-flow sectional area, has the characteristics of high enthalpy drop, large output torque and the like, and has simple and compact structure, light weight, wide range of application to aircrafts and wide range of flight envelope lines.

Description

Self-cooling high-speed ram air turbine generator

Technical Field

The invention relates to the technical field of a ram turbine generator, in particular to a self-cooling high-speed ram air turbine generator.

Background

Ram-air turbine is the auxiliary power device who is applied to aviation aircraft, converts the kinetic energy of the air that comes into among the aircraft flight process into the mechanical energy of rotor to further drive generator operation output electric energy, possess simple structure, the quality is light, only need introduce advantages such as air can start.

The ram air turbine can be divided into a paddle type turbine and a duct type turbine according to the structure, wherein the paddle type turbine is an exposed turbine, the blades are directly blown to rotate by the air kinetic energy during flight in low-speed to medium subsonic speed flight so as to drive a connected shaft to rotate at a high speed, the ram air turbine is often applied to low-speed civil airliners, when the flight height and the flight speed change in a flight envelope, the windward speed, the working speed and the output power of the paddle type ram air turbine change, the blade distance is required to be adjusted to adjust the pneumatic state so as to obtain the maximum power output, the adjusting mechanism is complex, the efficiency is low, and the working capacity is small. Meanwhile, the paddle type stamping turbine can only adopt a head air inlet mode due to low rotating speed and large volume, can only be externally hung below the wings or the fuselage of an airplane as an independent structure, and cannot be installed inside a fighter plane, an unmanned plane, an electronic pod or a missile. The ducted ram air turbine consists of a turbine stator and a rotor, adopts an axial air inlet mode, adjusts air flow and changes the direction of the air flow through the turbine stator, enables the air flow to have larger momentum to impact the subsequent rotor blades after acceleration, adjusts the output power of the turbine by changing the cross section area of a flow channel or the area of a throttle valve, can be applied to military aircrafts, and can work at subsonic speed and supersonic speed.

However, the ducted ramjet turbine adopts the same axial air intake mode as the turbofan engine, has the defects of overlarge cross-sectional area of through flow, small power density, heavier rotor, complex cooling system of a heavy-duty bearing and the like, and is not suitable for small aircrafts such as unmanned planes or electronic pods and the like which have higher requirements on the volume and the weight of equipment.

Disclosure of Invention

It is an object of the present invention to provide a self-cooling high speed ram air turbine generator which addresses the problems set forth in the background above.

In order to achieve the purpose, the invention provides the following technical scheme:

a self-cooling high-speed ram air turbine generator comprises a shell, wherein a generator stator coil is fixedly connected in the shell, a rotor mandrel is rotatably connected in the shell, a generator rotor magnetic steel is fixedly connected on the rotor mandrel, and the generator rotor magnetic steel is positioned in the generator stator coil;

the two ends of the rotor mandrel are respectively sleeved with a front end turbine and a rear end turbine, and the two ends of the shell are respectively provided with a front end air flow channel communicated with the front end turbine and a rear end air flow channel communicated with the rear end turbine.

As a further scheme of the invention: the front-end air flow channel comprises a front-end volute air inlet channel, a front-end volute diffuser and a front-end radial blade cascade, wherein the front-end volute air inlet channel is perpendicular to the axis of the shell, the front-end volute diffuser is fixedly connected with the front end of the shell, and the front-end radial blade cascade is fixedly connected with the front-end volute diffuser.

As a further scheme of the invention: and a front-end turbine wheel cover is arranged in the shell and close to the front-end volute diffuser.

As a further scheme of the invention: a turbine guide cone is arranged at the outlet of the front turbine in the shell, and a pulling sealing shaft sleeve in sealing connection with the rear turbine guide cone is sleeved at the position, close to the rear turbine guide cone, of the rotor mandrel.

As a further scheme of the invention: and a rear end exhaust passage is fixedly connected to the rear end turbine guide cone, and the other end of the rear end exhaust passage penetrates through the shell and extends to the outside of the shell.

As a further scheme of the invention: the front-end volute diffuser is connected with the rotor mandrel through a front-end radial bearing and a thrust disc in a rotating mode, a thrust bearing is arranged at the front end of the front-end radial bearing, the thrust disc is provided with friction surfaces in two radial and axial directions and can simultaneously form radial and axial friction pairs with the radial bearing and the thrust bearing, a thrust bearing end cover is arranged at the front end of the thrust bearing, the thrust disc is axially fixed with the rotor mandrel through a front-end rotor nut, and the thrust bearing end cover is fixedly connected with a front-end volute diffuser shell.

As a further scheme of the invention: the rear-end air flow channel comprises a rear-end volute air inlet channel vertically arranged with the axis of the shell, a rear-end volute diffuser fixedly connected with the shell, and a rear-end radial cascade fixedly connected with the rear-end volute diffuser.

As a further scheme of the invention: and a rear-end turbine wheel cover is arranged in the shell and close to the rear-end volute diffuser.

As a further scheme of the invention: the shell is of a sandwich structure, an interlayer in the shell is a cooling airflow cavity, an air inlet end of the cooling airflow cavity is communicated with an air outlet end of the rear-end turbine, the shell is provided with a front-end exhaust passage communicated with the cooling airflow cavity, and the front-end exhaust passage is positioned at one end, far away from the rear-end turbine, of the shell.

As a further scheme of the invention: the rear end volute diffuser is connected with the rotor mandrel in a rotating mode through a rear end radial bearing and a rear end radial bearing inner layer, a rear end rotor nut is arranged at the rear end of the rear end radial bearing inner layer, and the rear end radial bearing inner layer is fixedly connected with the rotor mandrel in the axial direction through the rear end rotor nut.

Compared with the prior art, the invention has the beneficial effects that:

1. the generator turbine adopts a centripetal radial-axial flow impeller form, supplies air through the radial blade cascade, has small axial through-flow sectional area, has the characteristics of high graded enthalpy drop, large output torque and the like, and has simple and compact structure, light weight, wider applicable aircraft range and wider flight envelope range;

2. the invention adopts a self-cooling scheme design, can fully utilize low-temperature exhaust gas generated after the work of an expansion output shaft to cool a motor stator and high-speed rotor magnetic steel which is extremely difficult to cool, utilizes the redundant friction heat generated when incoming flow air in the volute diffusers at two sides takes away the bearing in time to ensure the operation reliability, does not need to add a cooling system, and can obtain stronger work capability because the flowing air has certain temperature rise after cooling the bearing, which is equivalent to the recovery of a part of self-generated friction loss energy of the bearing. The arrangement of the impellers on the two sides not only improves the power density of the generator, improves the air input and the output power under the condition of not increasing the diameter of the impeller and reducing the rotating speed, but also greatly reduces the pneumatic axial force of the impeller, lightens the working load of a thrust bearing and enables the generator to have stronger overload capacity;

3. the self-cooling high-speed stamping turbine generator provided by the invention has the advantages of high rotating speed, convenience and quickness in maintenance, high reliability, small size and the like, can be directly applied to obtain constant power from the energy of stamping air when aircrafts such as fighters, unmanned planes, electronic pods, missiles and the like fly in a flight envelope range, and can also be applied to the situation that when a power system and an electric system of the aircrafts break down, the stamping air is introduced in the gliding process of the aircrafts to drive the generator to work and generate power so as to provide emergency power for electronic equipment of the aircrafts and assist in task completion;

4. the volute diffusers of the impellers on the two sides of the generator are arranged in opposite directions at the two ends and are respectively connected with the aircraft induced path through the volute self-contained pipeline, so that in order to ensure that the internal airflows of the two volutes with opposite rotation directions meet the requirement of radial cascade air inlet, the mounting positions of the volute pipelines at the two ends are positioned on the same side of the axis of the generator, and the pipeline space utilization rate is higher when the generator is mounted in aircrafts such as fighters, unmanned planes and electronic pods.

Drawings

FIG. 1 is a sectional view of the present embodiment;

fig. 2 is a side view of the present embodiment.

In the figure: 1-front end volute air inlet channel, 2-front end volute diffuser, 3-front end radial cascade, 4-front end turbine, 5-front end turbine wheel cover, 6-front end radial bearing, 7-thrust bearing, 8-thrust bearing end cover, 9-shell, 10-generator stator coil, 11-rear end turbine guide cone, 12-rear end turbine wheel cover, 13-rear end turbine, 14-rear end radial cascade, 15-rear end volute diffuser, 16-rear end volute air inlet channel, 17-rear end radial bearing, 18-rotor mandrel, 19-rear end rotor nut, 20-rear end radial bearing inner layer, 21-tension sealing shaft sleeve, 22-generator rotor magnetic steel, 23-front end guide shaft sleeve, 24-thrust disc, 25-front end rotor nut, 26-front end exhaust passage and 27-rear end exhaust passage.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1-2, in an embodiment of the present invention, a generator stator coil 10 is fixedly connected in a casing 9, a rotor spindle 18 is rotatably connected in the casing 9, a generator rotor magnetic steel 22 is fixedly connected to the rotor spindle 18, and the generator rotor magnetic steel 22 is located in the generator stator coil 10.

The front end of the rotor mandrel 18 is sleeved with a front end turbine 4, the front end of the shell 9 is provided with a front end air flow channel for driving the front end turbine 4 to rotate, the front end air flow channel comprises a front end volute air inlet 1 which is perpendicular to the axis of the shell 9, a front end volute diffuser 2 which is fixedly connected with the front end of the shell 9 and a front end radial cascade 3 which is fixedly connected with the front end volute diffuser 2, the front end radial cascade 3 is a group of airflow channels which are circumferentially arranged and have gradually-reduced cross sections, airflow can be uniform through circumferential arrangement, airflow speed and air pressure can be increased through cross section change, a front end turbine wheel cover 5 is arranged in the shell 9 and close to the front end volute diffuser 2, a turbine diversion cone 11 is arranged in the shell 9 and located at an outlet of the front end turbine 4, a sealing shaft sleeve 21 which is hermetically connected with the rear end turbine diversion cone 11 is sleeved on the position of the rotor mandrel 18 close to the rear end turbine diversion cone 11, fixedly connected with rear end exhaust passage 27 on rear end turbine water conservancy diversion awl 11, the rear end exhaust passage 27 other end passes casing 9 and extends to the outside of casing 9, front end spiral case diffuser 2 rotates with rotor dabber 18 through front end radial bearing 6 and thrust disc 24 to be connected, front end radial bearing 6 front end is equipped with footstep bearing 7, thrust disc 24 possesses the friction surface of radial and axial two directions and can form radial and axial friction pair with radial bearing 6 and footstep bearing 7 simultaneously, footstep bearing 7 front end is equipped with footstep bearing end cover 8, thrust disc 24 passes through front end rotor nut 25 and rotor dabber 18 axial fixity, footstep bearing end cover 8 and front end spiral case diffuser 2 shell fixed connection.

A rear end turbine 13 is sleeved at the rear end of a rotor mandrel 18, a rear end air flow passage for driving the rear end turbine 13 to rotate is arranged at the rear end of a shell 9, the rear end air flow passage comprises a rear end volute air inlet passage 16 which is perpendicular to the axis of the shell 9, a rear end volute diffuser 15 which is fixedly connected with the shell 9 and a rear end radial cascade 14 which is fixedly connected with the rear end volute diffuser 15, the rear end radial cascade and the front end radial cascade have the same structure and the same function, a rear end turbine wheel cover 12 is arranged in the shell 9 and close to the rear end volute diffuser 15, the shell 9 is of a sandwich structure, a sandwich layer in the shell 9 is a cooling air flow cavity, the air inlet end of the cooling air flow cavity is communicated with the air outlet end of the rear end turbine 13, a front end exhaust passage 26 which is communicated with the cooling air flow cavity is arranged on the shell 9, the front end diffuser exhaust passage 26 is arranged at one end of the shell 9 far away from the rear end turbine 13, and the, The rear end radial bearing inner layer 20 is rotatably connected with the rotor mandrel 18, a rear end rotor nut 19 is arranged at the rear end of the rear end radial bearing inner layer 20, and the rear end radial bearing inner layer 20 is axially and fixedly connected with the rotor mandrel 18 through the rear end rotor nut 19.

When the invention is used, the front end volute air inlet channel 1 and the rear end volute air inlet channel 16 in the front end air flow channel and the rear end air flow channel are both connected with an external air guide channel of an aircraft, ram air drawn by the air guide channel is divided into two paths to be introduced into the front end volute diffuser 2 and the rear end volute diffuser 15 of the turbine of the generator, the ram air flows in the diffusers along the circumferential direction, the air flow is decelerated and pressurized during the circumferential flow, the ram air is introduced into the radial blade cascade, the functions of rectification, deceleration and diffusion are performed on the incoming ram air, meanwhile, an installation interface is provided for the radial bearing and the thrust bearing, and a constant temperature heat sink is provided for the heat dissipation of the bearing. The front end radial blade cascade 3 and the rear end radial blade cascade 14 uniformly and respectively expand and accelerate the airflow in the volute diffuser to obtain larger momentum moment and proper impeller inlet angle, so that the impeller is pushed to rotate at high speed, and the airflow enters the turbine after being accelerated and uniformly distributed by the radial blade cascades to push the turbine to rotate and is finally axially discharged from the turbine outlet. The front end turbine 4 and the rear end turbine 13 convert the high-speed gas energy output by the radial blade cascade into mechanical work and output the mechanical work to the shaft end motor, which is a main energy conversion component. The front-end turbine wheel cover 5 and the rear-end turbine wheel cover 12 are used for sealing the impeller and reducing the leakage of the expansion air quantity of the working wheel. The front end radial bearing 6 and the rear end radial bearing 17 are used for providing radial bearing for two ends of the rotor and supporting the main shaft to rotate at a high speed. And the thrust bearing 7 is used for providing axial support for the rotor and preventing the rotor from axial displacement. And the thrust bearing end cover 8 is used for mounting a thrust bearing. And the shell 9 is used for mounting main parts of the generator, providing support, and an interlayer space is arranged between the mounting surface of the coil stator and the shell, so that the stator can be radiated by exhausting air through the impeller. The generator stator coil 10 generates current under the action of magnetic induction wire cutting rotating at high speed, converts mechanical energy into electric energy, and is a main transduction component. And the rear-end turbine guide cone 11 is used for guiding airflow at the outlet of the rear-end turbine to the interlayer space in the shell so as to cool the stator. And the rotor mandrel 18 is used for fixing rotating parts such as magnetic steel, a turbine and the like. The rear rotor nut 19 and the front rotor nut 25 are used for fastening sleeve structures such as a front turbine, a rear turbine, a radial bearing inner layer, a sealing shaft sleeve, a guide cone and the like on a mandrel to form an integral rotor. The inner layer 20 of the rear radial bearing has a smooth outer circular surface, and forms a high-speed friction pair with the rear radial bearing. The sealing shaft sleeve 21 is matched with the rear-end turbine guide cone for use, a plurality of annular air gaps are formed in the annular gaps in the high-speed rotation process of the rotor, the sealing effect is achieved, and therefore exhaust of the front-end turbine 4 after the rotor magnetic steel is cooled is isolated from exhaust of the rear-end turbine 13 which does not cool the motor stator. The generator rotor magnetic steel 22 is made of rare earth permanent magnets, and provides a rotating magnetic induction line for the stator coil under the driving of the turbine. And the front end guide shaft sleeve 23 is used for introducing exhaust gas discharged from the outlet of the front end turbine 4 into an annular air gap between the magnetic steel and the coil to dissipate heat of the rotor. The thrust disk 24 has a smooth outer circumferential surface and a flat end, and can form a high-speed friction pair with a front radial bearing and a thrust bearing. And a front end exhaust passage 26 connected to the annular sandwich on the housing for exhausting the rear end turbine 13 after cooling the stator out of the generator for further discharge out of the aircraft. And the rear end exhaust passage 27 is connected with the rear end turbine guide cone 11 and is used for leading the exhaust gas of the front end turbine 4 after the rotor magnetic steel is cooled out of the generator so as to be further discharged out of the aircraft.

1) The device is installed in aircrafts such as warplanes, unmanned planes, electronic pods and missiles and is connected with an air-entraining channel on the outer surface of the aircrafts, the design of the air-entraining channel meets the aerodynamic requirements of the aircrafts, and high-speed airflow of a non-boundary layer in the flight process can be drawn to enter a generator. 2) The turbine of the generator adopts a centripetal radial-axial flow impeller form, supplies air through a radial blade grid, has small axial through-flow sectional area, and has the characteristics of high level enthalpy drop, large output torque and the like. Meanwhile, the generator adopts two impellers oppositely arranged at two ends of the shaft to provide power, the aerodynamic axial force of the impellers can be balanced, the two impellers are designed to be the same in working condition, the rotating speed and the output power are equal, but the designed rotating directions are opposite. 3) The volute diffusers of the impellers on the two sides of the generator are arranged in opposite directions at two ends, and are connected with the aircraft through the volute self-contained pipeline, so that in order to ensure that the air flow in the two volutes with opposite rotation directions meets the air inlet requirement of the radial blade grid, the mounting positions of the volute pipelines at the two ends are positioned on the same side of the axle center of the generator, and the pipeline space utilization rate is higher when the generator is mounted inside aircrafts such as fighters, unmanned planes and electronic pods. 4) The generator consists of a permanent magnet rotor positioned on a rotating shaft and a coil stator positioned on a shell, and both adopt an air cooling mode, wherein the stator is cooled by air at the outlet of a front side turbine, the temperature of the air is reduced and a certain flow velocity is achieved after the air passes through a front side turbine expansion output shaft, and the air flows through the surface of magnetic steel rotating at a high speed to take away heat and is discharged through an internal rear side air channel. The generator coil stator is cooled by the outlet gas of the rear turbine, and the air is introduced into an interlayer space between the stator mounting wall surface and the outer wall of the shell through the flow guiding conical surface of the outlet after being cooled by the rear turbine expansion output shaft, so that the heat of the stator is taken away and then is exhausted through the internal front exhaust passage. 5) The rear turbine guide cone and the rotor are sealed in a pulling and grading mode, air flow after the rotor is cooled and rear turbine outlet air flow of the stator which is not cooled are effectively isolated while the guide effect is achieved, and internal air leakage loss is reduced. 6) The generator rotor is composed of a mandrel, magnetic steel, impellers at two sides, various shaft sleeves and fastening nuts and is supported by a bearing. The bearing is arranged in the volute diffusers at two ends of the generator, and can be cooled by the high-speed airflow in the volute diffusers in the working process in an auxiliary manner, so that the bearing is prevented from being burnt at high temperature due to poor heat dissipation in an internal installation mode. Meanwhile, the bearings are arranged at the two ends of the generator, and the generator can be replaced without disassembling after abnormal burning, so that the maintenance is very convenient. 7) The front and rear internal exhaust passages of the generator can adopt a rectangular section scheme, the rectangular section can save more axial space than a circular section under the condition of ensuring the same flow cross-sectional area, and meanwhile, because the flow velocity of exhaust gas of the impeller is far less than the air inlet flow velocity of the volute diffuser, the resistance loss of the exhaust passage adopting the rectangular section can be ignored. The internal exhaust passage is connected with the external exhaust passage on the surface of the aircraft, the external exhaust passage can adopt a design scheme conforming to the aerodynamics of the aircraft, the low-pressure area of the tail vortex in the flight process can be effectively utilized to reduce the exhaust pressure, and the expansion ratio and the output power of the stamping turbine are improved. 8) The generator has higher working rotating speed, and the generated high-frequency electricity can be rectified and inverted into electric energy required by the aircraft through post-processing equipment such as a frequency converter and the like

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.

Claims

1. A self-cooling high-speed ram air turbine generator comprises a shell (9), and is characterized in that a generator stator coil (10) is fixedly connected in the shell (9), a rotor mandrel (18) is rotatably connected in the shell (9), a generator rotor magnetic steel (22) is fixedly connected on the rotor mandrel (18), and the generator rotor magnetic steel (22) is positioned in the generator stator coil (10);

the turbine rotor is characterized in that a front-end turbine (4) and a rear-end turbine (13) are respectively sleeved at two ends of the rotor mandrel (18), and a front-end air flow channel communicated with the front-end turbine (4) and a rear-end air flow channel communicated with the rear-end turbine (13) are respectively arranged at two ends of the shell (9).

2. A self-cooling high-speed ram air turbine generator according to claim 1, characterised in that said front air flow path comprises a front volute inlet (1) arranged perpendicular to the axis of said housing (9), a front volute diffuser (2) fixedly connected to the front end of said housing (9), and a front radial cascade (3) fixedly connected to said front volute diffuser (2).

3. A self-cooling high speed ram air turbine generator as claimed in claim 1, characterised in that a front turbine shroud (5) is provided in the housing (9) adjacent to the front volute diffuser (2).

4. A self-cooling high-speed ram air turbine generator according to claim 1, wherein a turbine guide cone (11) is provided in the housing (9) at the outlet of the front turbine (4), and a bracing seal bushing (21) sealingly connected to the rear turbine guide cone (11) is sleeved on the rotor spindle (18) near the rear turbine guide cone (11).

5. A self-cooling high-speed ram air turbine generator as claimed in claim 1, characterised in that a rear exhaust duct (27) is fixedly connected to said rear turbine guide cone (11), the other end of said rear exhaust duct (27) extending through said housing (9) to the outside of said housing (9).

6. A self-cooling high speed ram air turbine generator as claimed in claim 1, wherein said front volute diffuser (2) is rotatably connected to said rotor spindle (18) by a front radial bearing (6) and a thrust disc (24), said front radial bearing (6) is provided with a thrust bearing (7) at its front end, said thrust disc (24) is provided with friction surfaces in both radial and axial directions to form radial and axial friction pairs with said radial bearing (6) and said thrust bearing (7), said thrust bearing (7) is provided with a thrust bearing end cap (8) at its front end, said thrust disc (24) is axially fixed to said rotor spindle (18) by a front rotor nut (25), and said thrust bearing end cap (8) is fixedly connected to said front volute diffuser (2) housing.

7. A self-cooling high speed ram air turbine generator as claimed in claim 1, characterised in that the aft air flow path comprises an aft volute inlet (16) arranged perpendicular to the housing (9) axis, an aft volute diffuser (15) fixedly connected to the housing (9), an aft radial cascade (14) fixedly connected to the aft volute diffuser (15).

8. A self-cooling high speed ram air turbine generator as claimed in claim 1, characterised in that an aft turbine shroud (12) is provided in the housing (9) adjacent the aft volute diffuser (15).

9. A self-cooling high-speed ram air turbine generator according to claim 1, characterised in that the housing (9) is of a sandwich construction, the sandwich in the housing (9) is a cooling air flow chamber, the air inlet end of the cooling air flow chamber communicates with the air outlet end of the rear turbine (13), the housing (9) is provided with a front exhaust duct (26) communicating with the cooling air flow chamber, and the front exhaust duct (26) is located at the end of the housing (9) remote from the rear turbine (13).

10. A self-cooling high speed ram air turbine generator as claimed in claim 1, characterised in that said aft volute diffuser (15) is rotationally connected to said rotor spindle (18) by an aft radial bearing (17), an aft radial bearing inner layer (20), said aft radial bearing inner layer (20) being provided with an aft rotor nut (19) at the aft end, said aft radial bearing inner layer (20) being axially fixed to said rotor spindle (18) by an aft rotor nut (19).