CN113431637B - Pure radial supersonic micro-turbine structure with air bearing - Google Patents

Abstract

The invention relates to a purely radial supersonic micro-turbine structure with an air bearing, in particular: the airflow enters the turbine stator flow channel (5) from the radial direction, and then the flow direction in the turbine maintains the radial direction; (2) It forms a scaling flow channel with the upper casing (1) and the lower casing (4), and its throat cross-sectional area is equal to the critical area of the designed flow rate, so that the air flow can be accelerated to supersonic speed; the inlet blade of the rotor impeller (3) is blunt. In order to block part of the flow area to adapt to the small design flow of the micro turbine; the back and edge of the rotor impeller (3) are engraved with dynamic pressure grooves, which form a dynamic pressure air bearing flow channel with the lower casing (4), and the turbine speed reaches At the design value, the gas in the dynamic pressure groove will provide support force by the viscous action and play the role of thrust and radial bearing. The invention can realize the expansion work of small flow and high pressure gas, and has the characteristics of compact structure, extremely high rotational speed, small required flow rate, cold air can be used for work, high expansion ratio and strong work ability.

Description

Pure radial supersonic micro-turbine structure with air bearing

technical field

The invention belongs to the field of rotor power mechanical structure design, and relates to a pure radial supersonic micro-turbine structure with a self-contained air bearing.

Background technique

The development of rotor-powered machinery has reached a high technical level, and large gas turbines and steam turbines have provided a steady stream of high-power power in various fields such as energy, ships, and aerospace. On the other hand, the miniaturization of turbines has always been a problem. The efficiency of turbines under low flow and low temperature conditions is much lower than that of ordinary working conditions. Therefore, in low-power application scenarios such as distributed energy, man-portable equipment, and aerospace satellite functions In the future, solar energy, batteries and even piston heat engines are often used for energy.

With the development of science and technology, the power density requirements for low-power application scenarios are gradually increasing. However, the development of solar energy and batteries requires the research progress of basic materials science, and the piston heat engine is close to the upper limit of theoretical efficiency, and it is difficult to continue to develop. It has become a feasible solution to develop a micro-turbine suitable for small flow and low power application scenarios.

Currently, the way to miniaturize turbines while reducing power drop is to increase the expansion ratio. However, when the expansion ratio exceeds a certain limit, it will bring about various problems such as supersonic airflow, ultra-high rotational speed, and complex flow field structure, and these problems are difficult to solve in traditional turbine design.

Therefore, a new turbine structure is proposed to solve or alleviate the above problems and realize the further development of the power density of small-scale energy power, which has important practical value.

The invention proposes a pure radial supersonic micro-turbine structure with its own air bearing, which can realize the expansion work of a small flow of high-pressure gas, and has the advantages of compact structure, extremely high rotation speed, small required flow rate, cold air can be used for work, and high expansion ratio , has the characteristics of strong function.

SUMMARY OF THE INVENTION

(1) Technical problems to be solved

The invention proposes a purely radial supersonic micro-turbine structure with its own air bearing, which solves the problems of supersonic airflow, ultra-high rotation speed and complicated flow field structure in the current small-flow turbomachinery under high expansion ratio design.

(2) Technical solutions

In order to solve the above technical problems, the embodiment of the present invention provides a pure radial supersonic micro-turbine structure with its own air bearing, including:

The upper casing 1 and the lower casing 4, the stator blade 2 and the rotor impeller 3 are sandwiched between the upper casing 1 and the lower casing 4, the rotor impeller 3 rotates around the rotation axis R, the stator blade 2 Each two pieces cooperate with the upper and lower casings to form a stator airflow channel 5, and the rotor impeller 3 cooperates with the lower casing 4 to form a dynamic pressure air bearing flow channel.

In one embodiment, the stator blade 2 is tightly connected with the upper casing 1 and the lower casing 4, and there is no blade tip clearance.

In one embodiment, the number of the stator blades 2 is multiple, and they are arranged at equal distances along the circumference of the casing.

In an embodiment, every two blades between the stator blades 2 are a group, and a group of stator blades cooperates with the upper casing 1 and the lower casing 4 to generate a stator airflow channel 5, and the flow channel The cross-sectional area shows a changing law of first contraction and then expansion.

In one embodiment, the cross-sectional area A _cr of the narrowest part of the stator airflow channel 5 is:

where G is the mass flow rate at the design point, ρ _cr is the critical gas density at the design point, c _cr is the critical sound velocity of the gas at the design point, and n is the number of the stator blades.

In one embodiment, the blade shape at the inlet of the rotor impeller 3 is a blunt tip, and the blade area accounts for more than 50% of the inlet area.

In one embodiment, the blades of the rotor impeller 3 are flush in the blade height direction, and do not change with the radial position.

In one embodiment, the disk of the rotor impeller 3 is engraved with dynamic pressure grooves on the edge and back of the disk, including radial dynamic pressure grooves 71 and thrust pressure grooves 72 .

In one embodiment, the rotor impeller 3 does not have any direct or indirect mechanical connection or contact with the upper casing 1 , the lower casing 4 and the stator blades 2 , and is supported by the dynamic pressure air bearing flow channel.

In one embodiment, the dynamic pressure air bearing flow channel includes a radial air bearing flow channel 61 and a thrust air bearing flow channel 62 .

(3) Beneficial effects

The pure radial supersonic micro-turbine structure with its own air bearing provided by the present invention has the following advantages: 1. The present invention uses blades to form a scaling flow channel, which can provide supersonic airflow while avoiding the traditional method. Part of the air intake problem caused by the use of the zoom type direct injection pipe; 2. The present invention forms a dynamic pressure air bearing structure by etching the dynamic pressure groove on the rotor impeller disc, and cooperates with the casing to solve the problem of high speed under high speed. There is no suitable mechanical bearing problem; 3. The present invention adopts a high-purity radial design of equal blades. Compared with the high radial rotation and axial design of variable blades of conventional radial turbines, the internal flow field changes from three-dimensional to quasi-two-dimensional. , which greatly reduces the difficulty of design and analysis.

Description of drawings

1 is a cross-sectional structural schematic diagram of a pure radial supersonic micro-turbine structure with a self-contained air bearing of the present invention;

2 is a schematic top view of a pure radial supersonic micro-turbine structure with a self-contained air bearing of the present invention (excluding the upper casing);

3 is a schematic diagram of a radial dynamic pressure groove of a rotor wheel disc of a pure radial supersonic micro-turbine structure with a self-contained air bearing of the present invention;

FIG. 4 is a schematic diagram of a thrust groove of a rotor wheel disc of a pure radial supersonic micro-turbine structure with a self-contained air bearing according to the present invention.

Detailed ways

The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and embodiments. The following examples are intended to illustrate the present invention, but not to limit the scope of the present invention.

As shown in Figure 1, the structure includes:

The upper casing 1 and the lower casing 4, the stator blade 2 and the rotor impeller 3 are sandwiched between the upper casing 1 and the lower casing 4, the rotor impeller 3 rotates around the rotation axis R, the stator blade 2 Each two pieces cooperate with the upper and lower casings to form a stator airflow channel 5, and the rotor impeller 3 cooperates with the lower casing 4 to form a dynamic pressure air bearing flow channel.

Among them, the dynamic pressure air bearing flow channel includes a radial dynamic pressure air bearing flow channel 61 and a thrust pressure air bearing flow channel 62 . Dynamic pressure grooves, including radial dynamic pressure grooves 71 and thrust pressure grooves 72 are engraved on the edge and back of the rotor impeller 3 .

When the turbine is working, the working medium gas flows into the stator airflow channel 5 uniformly from the circumferential direction, then flows into the rotor impeller 3, and finally is discharged from the air outlet of the upper casing 1. During the entire work process, the gas flows in the radial direction, and is discharged axially after the work is completed. In addition, the blade height does not change, and the flow field is quasi-two-dimensional.

Further, the purely radial design can allow the stator blades 5 to be closely connected with the upper casing 1 and the lower casing 4, and there is no leakage flow from the tip clearance.

Further, the use of vanes as supersonic stator flow channels instead of common Laval nozzles can achieve full circumferential air intake, avoiding the unsteady effect caused by partial air intake of the nozzle.

All of the above have greatly reduced the complexity of the flow field design, and laid the foundation for the subsequent use of supersonic airflow.

As shown in FIG. 2 , every two blades between every two stator blades 2 form a group, and a group of stator blades cooperates with the upper casing 1 and the lower casing 4 to form a stator airflow channel 5 , and the flow channel 5 is formed. The cross-sectional area of the channel shows a changing law of first shrinking and then expanding.

In one embodiment, the cross-sectional area A _cr of the narrowest part of the stator airflow channel 5 is:

Wherein G is the mass flow rate at the design point of this embodiment, ρ _cr is the critical gas density at the design point, c _cr is the critical sound velocity of the gas at the design point, and n is the number of the stator blades.

In one embodiment, the smallest cross-sectional area of the stator runner is located near the outlet. However, the position of the minimum cross-sectional area can be adjusted according to specific conditions, and different outlet airflow Mach numbers can be obtained by adjusting the position, which is not limited in the embodiment of the present invention.

Through the above design, supersonic airflow can be obtained without using partial air intake.

As shown in FIG. 3 , the disk of the rotor impeller 3 is engraved with radial dynamic pressure grooves 71 on the edge of the disk.

As shown in FIG. 4 , the wheel disc of the rotor impeller 3 is engraved with a thrust-reducing groove 72 on the back of the wheel disc.

In one embodiment, the radial dynamic pressure groove adopts the shape of a herringbone groove, and the thrust pressure groove adopts the shape of a spiral groove. However, the shape, number, and size of the dynamic pressure grooves can be adjusted according to specific conditions, and different adjustment can obtain different bearing capacity and stability, which is not limited in the embodiment of the present invention.

The turbine speed using dynamic pressure air bearing can reach more than one million revolutions per minute, far exceeding the upper limit of the allowable speed of existing mechanical bearings, and it is easier to achieve than mechanical bearings in miniaturization. By directly etching the dynamic pressure air bearing on the turbine, the upper limit of the turbine speed can be improved under the premise of being compact.

To sum up, the invention adopts the zoomed flow channel stator vanes to realize the supersonic airflow under the condition of full circumferential air intake, adopts the self-contained air bearing to realize the ultra-high speed under the compact condition, and adopts the pure radial design to alleviate the flow field. For the problem of complex structure, the miniaturization of the turbine is realized by solving the above three problems.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection of the present invention. within the range.

Claims (5)

1. A pure radial supersonic speed microturbine structure with an air bearing is characterized in that the structure comprises:

the rotor type engine comprises an upper casing (1) and a lower casing (4), wherein a stator blade (2) and a rotor impeller (3) are clamped between the upper casing (1) and the lower casing (4), and the rotor impeller (3) rotates around a rotating shaft (R);

the stator blades (2) are tightly connected with the upper casing (1) and the lower casing (4), no blade tip clearance exists, every two stator blades (2) are matched with the upper casing and the lower casing to form a stator airflow channel (5), and the sectional area of the channel is in a change rule of contracting and expanding firstly;

the rotor impeller (3) and the lower casing (4) are matched to form a dynamic pressure air bearing flow channel, the dynamic pressure air bearing flow channel comprises a radial air bearing flow channel (61) and a thrust air bearing flow channel (62), no direct or indirect mechanical connection or contact exists among the rotor impeller (3), the upper casing (1), the lower casing (4) and the stator blade (2), the rotor impeller is supported by the dynamic pressure air bearing flow channel, and the blade of the rotor impeller (3) is flush in the blade height direction and does not change along with the change of the radial position.

2. The pure radial supersonic microturbine structure with self-contained air bearing according to claim 1, characterized in that said stator blades (2) are plural in number and arranged equidistantly along the casing circumference.

3. The pure radial supersonic microturbine structure with self-contained aerostatic bearing according to claim 1, characterized in that the narrowest cross-sectional area A of the stator airflow channel (5) _cr Comprises the following steps:

where G is the design point mass flow, ρ _cr Critical density of gas at design point, c _cr And n is the number of the stator blades for the design point gas critical sound velocity.

4. The pure radial supersonic microturbine structure with self-contained air bearing as claimed in claim 1, wherein the shape of the blade at the inlet of the rotor wheel (3) is blunt and the blade area occupies more than 50% of the inlet area.

5. The pure radial supersonic microturbine structure with self-bearing air bearing according to claim 1, wherein the wheel disk of said rotor wheel (3) is engraved with dynamic pressure grooves at the edge and back of the wheel disk, including radial dynamic pressure groove (71) and thrust dynamic pressure groove (72).

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