GB2235018A

GB2235018A - Device for air cooling and the provision of mechanical power

Info

Publication number: GB2235018A
Application number: GB9010788A
Authority: GB
Inventors: Hans Lifka
Original assignee: Messerschmitt Bolkow Blohm AG
Current assignee: Airbus Defence and Space GmbH
Priority date: 1989-05-13
Filing date: 1990-05-14
Publication date: 1991-02-20
Anticipated expiration: 2010-05-14
Also published as: FR2646879B1; GB2235018B; FR2646879A1; GB9010788D0; DE3915697C1

Abstract

A multistage compressor assembly 4 is driven by a multistage turbine assembly 2 and a cooler 3, is arranged therebetween, in which respect a flowpath diversion 7 of approximately 180 DEG is arranged in the area of the cooler so that the turbine assembly and the compressor assembly have opposing flow directions. The upstream end of the turbine assembly 2 consists of an output-shaft driving turbine 23, and all adjacent stages of the turbine compressor assembly 2/4 stages of the compressor assembly 4 are designed for rotation alternately in opposing directions without stator-blade cascades inbetween. With the exception of the output-shaft turbine 23 every turbine stage and its corresponding compressor stage are coupled to a respective free-running rotor 10 to 16 in which respect the turbine blades may be arranged either radially outwardly or inwardly of the compressor blades. An after cooler 8 may be provided. The device may be used on hypersonic missiles and driven by pilot air (ram air). <IMAGE>

Description

1 AJW020490 DEVICE FOR AIR COOLING AND PROVISION OF MECHANICAL POWER This

invention relates to a device for cooling of gasses or gas mixtures and for provision of mechanical power as a drive source of the type comprising a multistage compressor assembly mechanically driven by a multistage turbine assembly, as well as a cooler arranged between the turbine assembly and the compressor assembly. Such a device is particularly applicable for use in air liquidisation in hypersonic, air- intaking missiles.

Hypersonic missiles moving in the atmosphere require a plurality of cooling operations due to high temperatures incurred by, for example, air friction as well as dynamic air pressure procedures. Suitable cooling media are, amongst others, onboard cryogenic propellants or suitable cooled, dammed up environmental air. Obtaining liquid oxygen from dammed up environmental air, which is cooled down to saturated steam level, and storage of same as propellant, for example for a rocket-driven upper stage, is also currently being considered.

Two methods are available for cooling such ram air, namely isentropic or at least virtually isentropic AJW020490 decrease in pressure in a turbine or isobar cooling in a heat exchanger.

With respect to the decrease in pressure in a turbine, apart from the temperature effects, the fact that the pressure also decreases, thus reducing the density and increasing the specific volume has to be considered. Mechanical power as drive source for any application is available at the turbine shaft.

By means of an in-line arrangement of turbine and cooler, mechanical power and heat can be extracted from the ram air.

By means of an in-line arrangement of a turbine, a cooler and a compressor, it is possible to extract heat and mechanical power from the ram air, whilst also reestablishing the initial pressure level. An illustration of these three thermo-dynamic processes in an h/s diagram (specific enthalpy/specific entropy) or in a T/s diagram (temperature/specific entropy) clearly shows that the enthalpy reduction in the turbine is larger due to the course of the isobars than the enthalpy increase in the compressor. Consequently, the turbine power is greater than the power intake of the compressor. Consequently, the turbine can drive the compressor and, due to its power surplus, further units.

i AJW020490 For the realisation of the latter 3-stage process, a solution offers itself from the constructional point of view, which is based on a conventional gas-turboshaft engine. The required device can be derived from the latter by substituting the combustor chamber with a heat exchanger in the form of a cooler and by changing the flow path so that first the turbines are flowed through, and lastly the compressor. With the exception of the output-shaft turbine (so-called free-running turbine), all turbine stages are coupled to the compressor by way of one or several shafts. Compressors and turbines are, for example, arranged or constructed in axial- or radial manner in which respect each stage consists of a stator-blade and a rotor-blade cascade. All rotating components are coaxially arranged whereby compressors and turbines are axially spaced apart by at least the length of the cooler. This space is bridged by one or several driveshafts of corresponding length. Such a device has several disadvantages. The axial length is great, and in consequence thereof the space requirement is large. The plurality of constructional components, particularly rotor blades, rotor wheels and shafts, causes a complex structure which is heavy, bulky, sensitive and expensive both in manufacture and maintenance.

In contrast thereto, it is an object of the AJW020490 invention to provide a device for cooling of gases or gas mixtures and provision of mechanical power which comprises a turbine assembly, a compressor assembly and a cooler driven by said turbine assembly, and which is particularly space-saving, lightweight, simple and thus good value, reliable and requiring only a minimum of maintenance.

With this object in view, the present invention provides a device of the type mentioned in the first paragraph hereto characterised in that the upstream end of the turbine assembly consists of a single- or multistage output-shaft turbine, that all further stages of the turbine assembly and all stages of the compressor assembly are arranged alternatively in opposing rotational direction from stage to stage (contrarotation) without stator-blade cascades inbetween, that the number of turbine stages, excluding the stages of the output-shaft turbine, corresponds with the number of compressor stages, that each of these turbine stages and its compressor stage are coupled to a respective freerunning rotor, and that the turbine blades are arranged radially outside or inside the compressor blades in which respect the turbine assembly and the compressor assembly are arranged to have substantially axial, opposing flow directions, and in which respect a flowchannel diversion of approximately 1800 is arranged in i 1 T AiWO20490 the area of the cooler.

- R- With the exception of the first flowed-through output shaft turbine, all turbine- and compressor stages are combined as free-running rotors. Thus dispensing with the respective driveshafts.

Due to the contra-rotation of successive stages, stator blades between the rotors can be dispensed with which is particularly favourable with respect to weight and constructional length. Both the turbine- and the compressor assembly are flowed-through substantially in the axial direction in which respect the flow direction in the cooler region is reversed. Thus, the first turbine stage (high pressure) is combined with the last compressor stage (high pressure) and reversed, i.e. there are hardly any pressure differences in any of the stages between turbine- and compressor side which extensively avoids leakage losses.

In preferred embodiments of the device according to the invention statormode cascades can be arranged in any one or more of the following positions: upstream of the output-shaft turbine, between the output-shaft turbine and the first free-running turbine stage, in the flow channel between the turbine assembly and the compressor assembly, downstream of the compressor AJW020490 Assembly.

The invention will be described in more detail with reference to the accompanying drawing in which the single figure is a schematic crosssection through a preferred practical embodiment of the device of the invention with the main-flow channel illustrated with its full length in cross-section.

The illustrated device 1 comprises tbree main elements, i.e. a turbine assembly 2, a cooler 3 and a compressor assembly 4 which are flowedthrough in this order. Energy-rich gas or gas mixture, for example pitot air at high temperature and high pressure, enters into the device 1 via inlet 5, the location and crosssectional form of which will be adapted to suit prevailing requirements. In the present case the inlet 5 is shown as having an off-centre arrangement.

In the region in front of the turbine assembly 2, the flow channel becomes circular in cross-section so as to allow flow to the first turbine assembly to be as even as possible. The first turbine stage is an outputshaft turbine 23 which - as illustrated - can be preceded by a stator-blade cascade 9. The blades of the possible multistage outputshaft turbine 23 transfer the power extracted from the gas flow, i.e. the product of ii AiWO20490 torque and angular speed (M x w) via a rotor 17 to a shaft 24 which is guided with as little friction as possible in bearings 21 and 22. At the free end of the shaft (to the right in the figure), the shaft power (M x w) can be applied for drive purposes of all types, for example to drive pumps, generators, compressors, etc.

If required, a stator-blade cascade can be arranged immediately downflow of the output-shaft turbine 23. All further turbine stages, for example the seven stages illustrated in this case, are in-line without intermediate rotor-blade cascades in which respect the rotational direction is reversed from stage to stage (contra-rotation). in this way considerable savings In weight and constructional length are achieved with the predetermined conditions of expansion.

According to the invention, each of the rotors 10 to 16 includes compressor blades so that the drive torque is transmitted in each stage direct from the turbine side to the compressor side, i.e. without shafts. By way of example, which applies to all the rotors 10 to 16, the rotor 16 is provided with turbine blades designated by reference number 18, compressor blades designated by reference number 19, and a bearing designated by reference number 20. All the rotors 10 to AiWO20490 - 8 - 16 are preferably freely rotatable on rollerbearing, i.e. independant of each other, in which respect their revolutions set themselves automatically depending on the blade geometry and the flow conditions.

The cooler 3, fluidically arranged between the turbine assembly 2 and the compressor assembly 4, is preferred to be a low-flow-drag heat exchanger in which the air (operating gas) releases heat to a further, spatially separated medium, for example cryogenic propellant. A flow-channel diversion 7 exists in the area of the cooler 3, which diversion reverses the flow direction (approximately 1800) so that the turbine outlet is connected by way of the shortest possible path to the compressor inlet. Stator-blade cascades may also be arranged in said area.

In the chosen flow duct, the left is the side of higher pressure for both the turbine assembly 2 and the compressor assembly 4, and the right is the side of lower pressure. The result of this is that in each free- running stage (rotors 10 to 16) the middle pressure on the turbine side approximately equals the middle pressure on the compressor side. This produces the advantageous effect that practically no leakage losses occur due to the necessarily present running gap between the rotors.

AiWO20490 - 9 - As indicated in the figure, the compressed air (operational gas) flows past the rotor 17 of the output shaft turbine 23 to enter into a bent flow channel leading to an aftercooler 8. This means that the rotor 17 has to have apertures which offer the air little resistance, thereby diminishing the power extracted from the output-shaft turbine 23 as little as possible.

Here again, stator-blade cascades can be arranged in the outlet area of the compressor assembly 4.

In reverse, relative to the area between the inlet 5 and the turbine assembly 2, the downflow flow-channel of the compressor assembly 4 in the illustrated example changes from a circular cross-section to an open crosssection dissposed outside the turbine housing, the shape of the latter cross-section preferably being adapted to fit the shape of the aftercooler 8. As the pressure is higher here, the density of the air is greater than in the area of the cooler 3, so the after-cooler 8 can, if devised, be smaller than the cooler 3.

The after-cooler 8 is not an essential part of the device 2. However, if the compressed air is to be cooled further, it may be useful to integrate the aftercooler 8 into the device 1. The air-flow path inside the device 1 ends at outlet 6.

1 AJW020490 - In an alternative (which is not illustrated) the compressor assembly may in contrast to the illustrated embodiment, be arranged relative to the shaft 24, radially outside the turbine assembly. The advantage of this arrangement Is that the rotor of the output-shaft turbine does not then have to be flowed-through by compressed operational gas.

21 AJW020490 - 11 -

Claims

1. A device for cooling of gases or gas mixtures and for provision of mechanical power, comprising a multistage compressor assembly mechanically driven by a multistage turbine assembly, as well as a cooler arranged between the turbine assembly and the compressor assembly, characterised in that the upstream end of the turbine assembly consists of a single- or multistage output-shaft turbine, that all further stages of the turbine assembly and all stages of the compressor assembly are arranged alternately in opposing rotational direction from stage to stage (contrarotation) without stator-blade cascades inbetween, that the number of turbine stages, excluding the stages of the output-shaft turbine, corresponds with the number of compressor stages, that each of these turbine stages and its compressor stage are coupled to a respective freerunning rotor, and that the turbine blades are arranged radially outside or inside the compressor blades in which respect the turbine assembly and the compressor assembly are arranged to have substantially axial, opposing flow directions, and in which respect a flowchannel diversion of approximately 1800 is arranged in the area of the cooler.

AJW020490 - 12 -

2. A device according to claim 1, wherein statorblade cascades are arranged in any one or more of the following positions: upstream of the output-shaft turbine, between the output-shaft turbine and the first free- running turbine stage, in the flow channel between the turbine assembly and the compressor assembly, downstream of the compressor assembly.

3. A device according to claim 1 or 2 wherein an aftercooler is arranged downstream of the compressor assembly.

4. A device for cooling of gases or gas mixtures and for provision of mechanical power substantially as hereinbefore described with reference to and as illustrated by the accompanying drawing.

Published 1991 atIbe Patent Office. State House. 66/71 High Holborn. London WCIR 47P. Further copies may be obtained from Saks Branch. Unit 6. Nin-t Mile Point. Cwmrelinfach. Cross Keys. Newport, NPI 7HZ. Printed by Multiplex techniques ltd. St Mary Cray, Kent.