GB2074244A

GB2074244A - Air intake structure for a compressor

Info

Publication number: GB2074244A
Application number: GB8110967A
Authority: GB
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1980-04-15
Filing date: 1981-04-08
Publication date: 1981-10-28
Also published as: DE3114914A1; FR2480367A1; JPS56152899U

Abstract

At least one annular guide member (54) is provided in the intake passage (28) to define at least two flow channels (56, 58) in order to provide a substantially even velocity distribution at the downstream end of the passage (28). This leads to an air intake structure which ensures an axially compact engine without impairing the performance of the compressor. The latter may be of centrifugal or axial type. <IMAGE>

Description

SPECIFICATION Air intake structure for a compressor The present invention relates generally to an air intake structure for a compressor for use with a gas turbine engine or the like. More specifically, the invention relates to an air intake structure which serves to make the engine compact without impairing the performance of the compressor.

Fig. 1 shows a conventional air intake structure.

An intake duct 2 has the two concentric internal surfaces 4 and 6 respectively of a trumpet or truncated hyperboloid-shape. The internal surfaces 4 and 6 are respectively symmetrical about the axis 8 of the compressor and define an air induction passage 10 therebetween. The indljction passage 10 comprises a part 12 extending radially and terminating upstream thereof with an opening 14 for drawing in air therethrough, followed by a bend 1 5 and a part 1 6 of sufficiently short length extending axially and facing at its downstream end a compressor rotor 1 7 to supply the air thereto.

Since there is a large demand for the reduction in size of engine structures particularly in automobiles or industrial machines, the air induction passages of the intake ducts of compressors are generally formed in such a bent shape as shown in Fig. 1 to make the axial length of the intake ducts as short as possible in view of the arrangement of the engine components. In this structure, however, an appreciably uneven velocity distribution results at the inlet of the-compressor rotor 1 7 as is indicated by the arrows A.This is because since the direction of flow sharply changes at the bend 1 5 of the induction passage 10 from the radial to the axial direction, according to the hydrodynamics of the system, the velocity at the inner curve becomes appreciably larger than the velocity at the outer curve of the bend 1 5 and a considerably longer length of the part 1 6 is necessary to return such an uneven velocity distribution to a substantially even velocity distribution.

This uneven velocity distribution at the inlet of the compressor rotor adversely affects the performance of the compressor so that a conventional air intake structure cannot provide a compact engine structure without impairing the compression efficiency of the compressor.

Therefore, it is an object of the present invention to provide an air intake structure for a compressor for use in a gas turbine engine or the like which renders the engine compact without impairing the compression performance of the compressor.

The air intake structure of the present invention includes an intake duct which is formed therein with an air induction passage of a bent shape. The induction passage has a substantially short length along the axis of the compressor in order to make the overall axial length of the intake duct as short as possible. At least one guide member is provided in the induction passage to define at least two flow channels therein for providing a substantially even velocity distribution at the downstream end of the induction passage.

In the accompanying drawings: Fig. 1 is a partial axial-sectional view of a gas turbine engine, wherein a conventional air intake structure is illustrated.

Fig. 2 is a partial axial-sectional view of a gas turbine engine, wherein an air intake structure of a first embodiment of the present invention is applied to a centrifugal compressor.

Fig. 3 is-a perspective view showing the shape of a guide vane to be used in the present structure.

Fig. 4 is a partial axial-sectional view of a gas turbine engine, wherein an air intake structure of a second embodiment of the present invention is applied to a centrifugal compressor.

Fig. 5 is a partial axial-sectional view of a gas turbine engine showing only the intake-side of the axial-flow compressor rotor, wherein the air intake structure of the first embodiment is applied to an axial-flow compressor.

Fig. 6 is a partial axial-sectional view of a gas turbine engine, wherein the air intake structure of the first embodiment is applied to an axial-flow compressor.

Referring now to Fig. 2, there is illustrated a first embodiment of the present invention. An intake duct 20 has two concentric internal surfaces 22 and 24 respectively of a trumpet or a truncated hyperboloid-shape. The internal surfaces 22 and 24 are respectively symmetrical about the axis 26 of the gas turbine engine and define an air induction passage 28 therebetween.

The induction passage 28 comprises a part 30 extending radially and terminating upstream thereof with an opening 32 for drawing in air therethrough, followed by a bend 34 and a part 36 of sufficiently short length extending axially and facing at its downstream end blades 38 of a centrifugal compressor rotor 40 to supply the air thereinto.

The air is drawn by the operation of the compressor rotor 40 into the induction passage 28 through the opening 32 and is then drawn into the rotating compressor blades 38 to be compressed. The compressed air is introduced into a combustion chamber 42 through an annular diffuser 44, where it is mixed with fuel and ignited to become a high temperature, high pressure gas.

This gas is then introduced into blades 46 of a turbine rotor 48 through a volute casing 50 and a turbine nozzle 52 and expands to drive the turbine rotor 48, which rotor 48 drives the compressor rotor 40 through a shaft 53.

A guide vane 54 of a trumpet or a truncated hyperboloid-shape as shown in Fig. 3 is provided in the induction passage 28 at the bend 34 thereof. The guide vane 54 is disposed concentrically with the internal surfaces 22 and 24 and extends substantially parallel to the internal surfaces 22 and 24 from its upstream end facing the opening 32 to its downstream end facing the compressor blades 38. The guide vane 54 is disposed substantially in the middle between the internal surfaces 22 and 24 to define two flow channels 56 and 58 therebetween and is supported at its downstream end by a plurality of supporters 60 which are secured to the internal surface 22 and are spaced at substantially regular intervals around the circumference thereof.

As described before, if no guide vane 54 is provided in the bend 34, the velocity at the inner curve (at the internal surface 24) becomes appreciably larger than the velocity at the outer curve (at the internal surface 22) of the bend 34 so that the velocity distribution at the inlet of the compressor rotor 40 becomes considerably uneven. More specifically, according to the hydrodynamics of the system, the static air pressure in the bend 34 is smaller at the inner curve than at the outer curve, thus the velocity of the air in the bend 34 is larger at the inner curve than at the outer curve since the velocity is inversely proportional to the static pressure.

By providing the guide vane 54 as in Fig. 2, the width of each of the channels 56 and 58 becomes substantially half of the entire width Wof the bend 34 and the rate of flow in each channel also becomes smaller than the entire flow rate in the- bend 34. Thus, according to the hydrodynamics of the system, the difference in static pressure between the inner and outer curves of the bend 34 becomes correspondingly smaller which results in a substantially equalized pressure distribution in the bend 34. Accordingly, the velocity distribution in the bend 34 is also substantially equalized so that the velocity distribution at the inlet of the compressor rotor 40 becomes substantially even as shown by the arrows B to assist the higher performance of the compressor.

Now referring to Fig. 4, there is shown a second embodiment of the present invention, wherein like or corresponding parts or members are designated by the same references as in Fig. 2.

In this embodiment, two guide vanes 64 and 66 respectively of a trumpet or a truncated hyperboloid-shape as shown in Fig. 3 are provided in the induction passage 28 at the bend 34 thereof. The guide vanes 64 and 66 are respectively disposed concentrically with the internal surfaces 22 and 24 and define three flow channels 68, 70 and 72 of substantially the.same width between the internal surfaces 22 and 24.

Each of the guide vanes 64 and 66 extends substantially parallel to the internal surfaces 22 and 24 from its upstream end facing the opening 32 to its downstream end facing the compressor blades 38.

The guide vane 64 is supported at its downstream end by a plurality of supporters 74which are secured to the internal surface 22 and are spaced at substantially regular intervals around circumference thereof.

The guide vane 66 is supported at its downstream end by a plurality of supporters 76 which are secured to the outer periphery of the guide vane 64 and are spaced at substantially regular intervals around the circumference thereof.

The other components are similar to those in Fig. 2.

By this construction, the flow rate in each of the channels 68,70 and 72 and the width of each channel are respectively further decreased in comparison with those of the first embodiment with the result that a much more even velocity distribution as designated by the arrows C is obtained at the inlet of the compressor rotor 40.

The number of guide vanes may be increased in the same way as in the second embodiment to attain an even more equalized velocity distribution.

It is to be noted that since the present invention is exclusively concerned with an improvement to the intake-side of compressor rotors, the present air intake structure is applicable to compressors of any construction.

For example, in Fig. 5 is shown the air intake structure of the first embodiment applied to an axial-flow compressor of the gas turbine engine, wherein like or corresponding parts or members are designated by the same references as in Fig. 2 and only the intake-side of the compressor rotor is shown to simplify the explanation.

Reference numerals 78 and 80 respectively designate moving and stationary blades of the first stage. Other components not illustrated in Fig. 5 can be any known constructions of axial-flow compressors.

As is clear from Fig. 5, since there is no factor introduced to impede or reduce the effect of the present air intake structure, the same effect as that attained in Fig. 2 is also achieved in Fig. 5 regardless as to whether the present air intake structure is applied to centrifugal compressors or axial-flow compressors.

For a better understanding, there is further provided Fig. 6 as an example, wherein like or corresponding parts or members are designated by the same reference as in Fig. 2 and the air intake structure of the first embodiment is incorporatad in one type of an axial-flow compressor.

It is to be understood that the invention is not to be limited to the embodiments described in the foregoing, and that various changes and modifications may be made without departing from the scope of the invention as defined in the appended claims. For example, the guide vanes of the first and second embodiments may have various shapes which can smoothly guide the airflow and make the velocity distribution at the downstream end of the induction passage substantially even.

Claims

1. An air intake structure for a compressor comprising: an intake duct formed therein with an air induction passage having a substantially short length along the axis of the compressor, said induction passage including a first section extending substantially straight from the upstream end of said induction passage, a second section extending substantially straight from the downstream end of said induction passage and a third section connecting said first and second sections, said third section having such a shape as to angle said first and second sections; and a guide means provided in said induction passage to render the velocity distribution at the downstream end of said induction passage substantially even.

2. An air intake structure for a compressor comprising: an intake duct formed therein with an air induction passage of a bent shape having a substantially short length along the axis of the compressor; and a guide means provided in said induction passage to render the velocity distribution at the downstream end of said induction passage substantially even.

3. An air intake structure for a compressor as set forth in claim 1 or 2, wherein the guide means is at least one guide vane which extends in the direction of flow and defines at least two flow channels in the induction passage.

4. An air intake structure for a compressor comprising: an intake duct having concentric first and second internal surfaces respectively of substantially trumpet-shape which are respectively symmetrical about the axis of the compressor, said first and second internal surfaces being placed apart from each other to define therebetween an air induction passage having a substantially short length along the axis of the compressor: and a guide means provided in said induction passage to render the velocity distribution at the downstream end of said induction passage substantially even.

5. An air intake structure for a compressor as set forth in claim 4, wherein the guide means is a guide vane of trumpet-shape disposed concentrically with the first and second internal surfaces and extending substantially parallel to said internal surfaces, said guide vane disposed substantially in the middle between said internal surfaces to define two flow channels therebetween.

6. An air intake structure for a compressor as set forth in claim 4, wherein the guide means is a plurality of guide vanes respectively of trumpetshape, each of which is disposed concentrically with the first and second internal surfaces, said guide vanes respectively extending substantially parallel to said internal surfaces and defining a plurality of flow channels of substantially the same width between said internal surfaces.

7. An air intake structure for a compressor as set forth in claim 5 or 6, wherein the, or each of the guide vanes is supported by a plurality of supporters.

8. An air intake structure for a compressor substantially as described with reference to, and as illustrated in, Fig. 2, or Fig. 4, or Figs. 5 and 6, of the accompanying drawings.