US2708547A - Exhaust gas turbo-blowers for high supercharging rates and method of mounting same - Google Patents

Description

May 17, 1955 A. E. SCHUTTE 2,708,547

EXHAUST GAS TURBO-BLOWERS FOR HIGH SUPERCHARGING RATES AND METHOD OF MOUNTING SAME Filed July 5. 1951 Unite EXHAUST GAS TURBO-BLOWERS FOR HIGH SUPERCHARGING RATES AND METHOD OF MOUNTING SAME Alfred Egon Schiitte, Saint-Germain-en-Laye, France, assignor to Societe dEtudes dc Machines Thermiques, La Courneuve, France, a French body corporate This invention relates to the supercharging of compression-ignition or diesel engines.

The efficiency of a single-wheel turbo-blower is insufficient to comply with the very high compression ratio requirements of compression-ignition or diesel engines, except in the case of aircraft engines. this case the stresses are so high and the useful life so short that the same constructional principles cannot be applied to marine or fixed engines. Besides, the velocities of rotation of these turbo-blowers are so high that these could not withstand continuous operation as required in marine or land power plants.

In view of the foregoing and in the case of diesel engines having by definition a high compression ratio it is necessary on the one hand to provide multi-wheel turboblowers, more specifically twin-wheel turbo-blowers, and

on the other hand to combine constructional simplicity with low cost as much as consistent with the particular technique of this field.

First of all, it will be well to endeavour to design twobearing shafts for these turbo-blowers, a requirement very difficult to meet. Moreover, turbo-blowers should be able to operate at any R. P. M. ratings corresponding to the different loads of the engine, so that these shafts should have a critical flexure much above the normally required R. P. M. value.

As a rule, the production of turbine shafts corresponding to these requirements is not difficult, yet the main trouble lies in the position of the blower wheels which are generally of the radial type and should be placed as close as possible to the bearing on the blower side, because this shaft is formed with a portion having a smaller diameter at the point where the wheels are fixed, in the case of blowers of conventional or known type. As a consequence the blower wheel has been so disposed that the air is sucked in without any intermediate gap on the side of the turbine casing. The first stage is therefore positioned close to the turbine casing whilst the second stage is directly close beside the blower-side bearing. With this arrangement the gap separating the bearing is materially shortened but various drawbacks are observed.

Thus, as the air is sucked from the space adjacent to the turbine casing it is necessary to keep into account the pre-heating of this air before it is taken in, so that it is necessary to increase the power required for driving the blower. In order to avoid these difficulties a water-cooled chamber has been devised between the turbine casing and the intake side of the first wheel. This obviously is a complication having a detrimental influence on cost.

Moreover, with this arrangement the air is still taken from the vicinity of the turbine and fed to the blower at a higher temperature. If the air is drawn from outside instead of from the engine room, air filters are required and this is another difficulty. The fitting of air-intake ducts from the outside to the blower and of filtering means cannot be carried out in a satisfactory manner.

It is the principal scope of this invention to avoid all the inconveniences set forth hereinabove.

However, even in 4 States atent With this purpose in view, it is the object of this invention to provide a novel means for mounting turbo-blowers of this type comprising two or more compression stages and supported by a pair of external bearings. One essential feature of this means is that it consists in disposing the first compression stage on the side of the bearing adjacent to the blower and the last stage in close vicinity to the turbine.

According to another characteristic feature of this invention, the last blower stage is heat-insulated from the turbine casing or body.

Of course, the present invention has also for its object to provide any turbo-blowers assembled in accordance with the above-defined means for assembly. v

A first remark suggested by the arrangementaccording to this invention is that the air is not heated before entering the blower. Moreover, filters, silencers and even air ducts maybe fitted on this intake pipe or port.

Water-cooling can be dispensed with and the desired heat-insulating effect obtained by simply fitting between the blower casing and the turbine casing a layer of heatinsulating material such as asbestos, slag wool, etc.

Similarly, the external bearing can be readily disassembled and is constantly accessible. In spite of this arrangement the distance between bearings may be kept'within reasonable limits provided that the centre of the annular delivery chamber or the axis of the delivery casing is so disposed that it coincides with the axis of the delivery wheel of the last stage.

With the same object in view the arrangement may com prise blades bent backwards with a constant width for the air passage, and the delivery casing of spiral or annular shape may be disposed between the blower wheel and the turbine casing. One advantage of the use of wheels with backward bent blades and constant-width air passage is their reduced axial length and the fact that they are particularly suitable for turbo-blower design.

The arrangement according to this invention is still more advantageous with respect to critical flexure stress. The last stage wheel may comprise a hub bored to a greater diameter than the preceding wheel since the volume of air passing therethrough is already reduced. Thus, the rotor diameter may progressively increase towards the middle.

The af'fixed drawing forming part of this specification illustrates diagrammatically by way of example one possible embodiment of a turbo-blower according to this invention. In the drawing:

Fig. 1 is an axial longitudinal section of the turboblower,

Fig. 2 is a side view thereof, and

Fig. 3 is a detailed front elevational view of a modified form of blading for the wheels, wherein the blading of the wheels is bent backwards.

In the embodiment shown the turbo-blower is designed for two exhaust pipes or manifolds each grouping a number of cylinders of a same engine. However, whilst this arrangement is given by way of example only, it will be understood that many other arrangements may be resorted to without departing from the spirit and scope of the invention.

The shaft 1 is journaled in a bearing 2 on the turbine side and in another bearing 3 on the blower side. The bearing 2 is designed as a thrust hearing. The exhaust gases from the engine enter through inlets 4, 5 into a chamber 6. The exhaust gases are distributed by an annulus of nozzles 7 to a turbine blading 8 and pass therethrough to the atmosphere via an outlet 10. On the other hand, air is sucked in through a casing 11 formed with an inlet 12 having a cross-sectional area sufiicient to permit the fitting therein either of a filter or of an inlet manifold 3 adapted to draw in air from the outside. However, air may be taken directly from the engine room.

Any conventional or known silencer may be substituted for the intake casing 11. The air sucked by the wheel 13 is delivered through a diffuser 14, guide-vanes 15 and a wheel 16. Another dififuser 17 is mounted in a manifold 18 and a tangential outlet aperture 19 is connected to the delivery pipe connection. The hub bore of Wheel 16 has a greater diameter than wheel 13. Therefore, this shaft is thicker at 20 than 21, which is advantageous with regard to critical flexure stresses.

The bladings of wheels 13 and 16 may be bent backwards, as indicated at 16' in Fig. 3, wherein the bladings for wheel 16' are bent backwards. Such showing is illustrative of how the bladings for both wheels 13 and 16 may be bent backwards. The blading will also have air passages, as shown, that are of a designed width so as to be substantially constant in cross-sectional area.

Preferably, a heat-insulating layer or wall (not shown) may be disposed between the blower casing 18 and the turbine casing 9.

Of course, the invention is not restricted to the embodiment illustrated and described which is given merely by way of example.

What I claim is: I

l. Exhaust-gas turbo-blower assembly for high supercharging rates, including an exhaust gas turbine and a centrifugal multistage blower positioned coaxially therewith and having a blower wheel for each stage and a compressed air outlet, at single shaft for the mounting of this assembly mounting said gas turbine and blower Wheels, each wheel having a central boring permitting its mounting on said shaft, the diameter of said borings increasing progressively from the first stage to the last one, two bearings supporting the said shaft and situated externally of :3 said assembly, the said bearings being moreover independent of this latter and located in an easily accessible way, the blower having its first stage and the gas inlet adjacent to one of said external bearings and the last stage and the compressed air outlet adjacent to the turbine, the said shaft having its diameter increasing in a direction from the place where the first stage wheel is mounted towards the mounting of the subsequent stages, the greatest value of the diameter corresponding substantially to the mounting of the turbine and of the last blower stage having a wheel with a greater central boring whereas said diameter decreases beyond the mounting of said turbine.

2. Exhaust-gas turbo-blower assembly according to claim 1 wherein the blower wheels are provided with backward bent blades and parallel side walls.

3. Exhaust-gas turbo-blower assembly according to claim 1 wherein an air delivery casing is positioned between the turbine and the wheel of the last stage of the blower.

References Cited in the file of this patent UNITED STATES PATENTS 1,263,056 Graemiger Apr. 16, 1918 1,400,323 Sherbondy Dec. 13, 1921 1,751,537 Vianello Mar. 25, 1930 1,993,963 Heinze Mar. 12, 1935 2,216,731 Birrnann Oct. 8, 1940 2,475,151 Nichols July 5, 1949 2,578,785 Davis Dec. 18, 1951 FOREIGN PATENTS 65,284 Denmark Dec. 20, 1943 159,150 Great Britain Aug. 4, 1921 214,246 Switzerland July 1, 1941 636,936 Germany Oct. 17, 1936

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