Patent Application
20210285460
This application claims priority, and benefit under 35 U.S.C. § 119(e) of Chinese Patent Application No. 202010160489.4 filed Mar. 10, 2020. The disclosure of the prior application is hereby incorporated by reference as if fully set forth below.
The present disclosure relates to the technical field of aerodynamics, in particular to a method for controlling flow separation on a suction surface of a stator blade of an axial compressor/fan by means of micro air injection generated by velocity impulse.
Stators and rotors are cooperated to form stages of an axial compressors/fan. The stators are used to change flow directions and decelerate and pressurize the flow. With an increase in the stage pressure ratio of the axial compressors/fans, the inlet velocity and the flow turning angle of the stators increase. In this case, the thickness of the boundary layers on suction surfaces increases, and even flow separation occurs. As a result, flow loss increases. To increase the thrust-to-weight ratio of aero-engines, the compressors/fans have always been developed in the direction of high stage pressure ratios. Therefore, for aviation compressors/fans, it is more valuable to control boundary layers on the suction surfaces of the stators.
In November 2019, the paper “influence of slotting in blade root on performance of conventionally loaded high-velocity compressor cascade” was published by Tang Yumeng et al in the Journal of Engineering Thermophysics. In this paper, compressor blades were slotted in middle span to form jet flows of high-momentum for blowoff of boundary layers on suction surfaces, and different solutions were compared by means of numerical simulation to show the effectiveness of slotting on controlling the flow separation. Since the flow energy difference between the pressure surface and the suction surface is small, the jet formed by the slotting has weaker control over the boundary layers on the suction surfaces.
To overcome the shortcomings of the prior art, the present disclosure provides a method for controlling flow separation on a suction surface of a stator blade of an axial compressor/fan by means of micro air injection generated by velocity impulse. This can suppress the boundary layer on the suction surface of the stator blade of the axial compressor/fan, thus reducing flow loss of the stator and improving efficiency of the axial compressor/fan.
In order to achieve the above objective, the present disclosure adopts the following technical solution:
A method for controlling flow separation on a suction surface of a stator blade of an axial compressor/fan by means of micro air injection is provided, where a blade profile is slotted to form a slotted blade profile, a slot has one end (inlet) at a leading edge of the blade profile and the other end (outlet) on a suction surface of the blade profile; and when an airflow flows through a blade, a small portion of the airflow flows into the slot and then is ejected via the outlet.
Further, the inlet of the slot in the blade profile may exactly face an incoming flow.
Further, the outlet is located on the suction surface where the boundary layer needs to be blown off.
Further, the shape of the slot in the blade profile may be optimized as follows: the shape of the slot in the blade profile is initially determined artificially; the flow field of the cascade formed by the slotted blade profiles is calculated by means of numerical simulation; then the shape is modified according to analysis on the structure of the flow field; and finally, an optimized shape is obtained.
Beneficial effects: compared with the prior art, the method for controlling flow separation on a suction surface of a stator blade of an axial compressor/fan by means of micro air injection has the following advantages: higher momentum micro air injection can be achieved to effectively blow off the boundary layer on the suction surface of the blade, thus reducing flow loss and improving efficiency of the axial compressor/fan.
In the figures, 1. leading edge of a blade profile, 2. a small portion of airflow, 3. slot in the blade profile, 4. blade profile, 5. suction surface of the blade profile, 6. pressure surface of the blade profile, 7. chord of the blade profile, 8. rear edge of the blade profile.
The present disclosure is further described below with reference to the accompanying figures and embodiments.
Implementation
A method of the present disclosure for controlling a boundary layer on a suction surface of a stator of an axial compressor/fan (i.e., a fan of a compressor) by means of micro air injection generated by velocity impulse is described below with reference to
Generally, a number of blade profiles are stacked in the radial direction according to a certain stacking rule, and the profiles are used as the skeleton and spline curved surfaces are used to cover the skeleton to form an axial compressor/fan stator blade. Therefore, the blade profiles are basic elements of the blade, and aerodynamic performance of the blade is determined by the blade profiles. The stator blade in the present disclosure is hollow and is formed by slotted blade profiles. A slot (3) in each blade profile (4) has one end (inlet) at a leading edge (1) of the blade profile and the other end (outlet) at a position where a boundary layer on the suction surface (5) of the blade profile is required to be blown off. When airflows flow through the blade, a small portion of the airflows (2) flow into the slot (3) and then are ejected via the outlet. The jet flow increases momentum on the boundary layer at this position, suppresses growth of the boundary layer, and controls flow separation on the boundary layer. In this way, flow loss of the stator is reduced, and efficiency of the axial compressor/fan is improved. Because an inlet of the slot exactly faces incoming flows, the small portion of the airflows in the slot has high momentum, so that a jet flow from the outlet of the slot has a high velocity. Based on this, the boundary layer on the suction surface can be effectively suppressed.
The blade profile mainly has the following aerodynamic performance indexes: under a certain inlet Mach number and inlet angle, a given airflow turning angle is reached and the flow loss is as small as possible, and attack angle range of the low loss is as large as possible. the shape of the slot is initially determined artificially; the flow field of the cascade formed by the slotted blade profiles is calculated by means of numerical simulation; the shape of the slot in the blade profile is modified according to analysis on structure of the flow field. For example, a width δ of the slot is increased to increase the flow rate in the slot; a distance L between the outlet of the slot and the leading edge of the blade profile is reduced to control the boundary layer on the suction surface earlier. Finally, an optimized slot in the blade profile is obtained to achieve excellent aerodynamic performance of the blade profile and low flow loss in the slot.
The above descriptions are merely preferred implementations of the present disclosure. It should be noted that a person of ordinary skill in the art may further make several improvements and modifications without departing from the principle of the present disclosure, and such improvements and modifications shall also be deemed as falling within the protection scope of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202010160489.4 | Mar 2020 | CN | national |
