CN100532863C - Process case design method - Google Patents

Abstract

This invention relates to a method for processing box of a fan/compressor, which takes a flow field of rotor blade tip of a fan/compressor stage as the basis to analyze its un-steady time-space structure to get a flow frequency and starting position of a dominant flow field structure to determine groove numbers of the box to be processed, relative position of the rotor and its concrete structure.

Description

Process case design method

technical field

The invention relates to a processing method for a fan/compressor casing, which can greatly improve the stable working range of the fan/compressor under the premise that the efficiency of the fan/compressor remains basically unchanged.

Background technique

In the design and development process of aeroengine compressors, the unstable flow of the compressor, such as stall and surge, greatly limits the further improvement of the performance of the compressor. In order to make the compressor have a large stable operating margin and ensure the safe operation of the engine, the designer often sacrifices the performance of the compressor and places the operating point of the compressor far away from its best efficiency point. Therefore, widening the stable working range of the compressor has become the goal pursued by aero-engine designers.

In order to improve the stable operating range of the compressor, fan/compressor designers have proposed various forms of casing processing. Figure 1-Figure 3 shows three typical structural forms of processing casings.

As shown in Figure 1, the axial groove structure handles the casing. The casing is grooved along the axial direction of the compressor, and the groove depth direction forms a certain angle with the radial direction of the compressor. When the groove depth direction is aligned with the incoming flow direction, the stall margin is greatly improved no matter the incoming flow is a uniform flow or inlet distortion occurs.

As shown in Figure 2, the blade chord groove processing casing is grooved along the chord direction of the blade tip element on the casing, and the groove depth direction can also have different angles, and all the chord grooves can be connected through the air chamber .

As shown in Figure 3, the anti-vortex shallow groove processing casing is based on the direction and strength of the known vortex in the blade passage, and a triangular groove without air chamber is opened on the casing along the axial direction of the compressor. When the blade sweeps these processing When the groove is formed, the vorticity with the opposite sign to the known vorticity is generated through the change of the curvature of the casing wall, and it cancels with the known vortex in the blade channel, so that the stall margin is improved.

However, the design of the traditional processing casing still stays in the empirical design stage under the constant framework, and it often sacrifices efficiency while expanding the stable working margin. Moreover, due to the many geometric and aerodynamic parameters involved in the handling of the casing, it is difficult to achieve a very reliable design method based on experience. Sometimes the same type of processing casing is used successfully in the front stage but the effect is not obvious when used in the rear stage. The effect is significant for fans but not for core compressors.

Contents of the invention

The technical problem to be solved by the present invention is to provide a novel casing processing design method, so that after the fan/compressor is equipped with a processing casing, the efficiency of the fan/compressor can be guaranteed to be basically not reduced, and the fan/compressor can be greatly improved. The stable working range of the compressor.

The processing casing design method provided by the present invention utilizes the relative motion between the processing casing positioned above the fan/compressor rotor and the fan/compressor rotor blades to couple the flow inside the processing casing with the vortex flow inside the rotor channel, The internal flow field of the rotor is transformed from disorder to order, thereby suppressing or eliminating blockage of the internal flow field of the rotor, and achieving the purpose of expanding the stable working range of the fan/compressor.

The technical solution of the present invention is to select appropriate processing casing design parameters according to the unsteady space-time structure of the internal flow field of the fan/compressor, so that the flow in the processing casing slot and the internal flow of the fan/compressor generate unsteady coupling. The specific method is as follows:

(1) Accurately measure or numerically simulate the internal flow field of the fan/compressor rotor, analyze the spatio-temporal structure of the unsteady flow field at the blade tip, and determine the dominant flow field structure and its flow characteristics. This flow field structure includes end wall boundary layer separation, blade surface boundary layer separation, gap vortex and so on.

(2) Obtain the flow frequency of the flow field structure dominant in the fan/compressor rotor blade tip region.

(3) Determine the initial position of the dominant flow field structure in the fan/compressor rotor tip region. Corresponding to different dominant flow field structures, the starting position can be the separation point, the origin of the gap vortex, etc.

(4) Determine the number of slots for processing the casing. The number of slots in the processing case satisfies:

$\mathrm{<span\; class="notranslate">\; 0.7</span>}<span\; class="notranslate">\; \&le;</span>\frac{\mathrm{<span\; class="notranslate">\; Z</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; 60</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; 1.5</span>}$

Among them, Z is the number of slots in the treatment casing, n is the rotor speed (rpm), and f is the flow frequency of the flow field structure dominated by the rotor tip.

(5) Determine the position of the processing casing relative to the rotor. The treatment case inlet or outlet is located at the beginning of the flow field structure dominated by the rotor tip region. The position of the other end of the processing casing is located upstream or downstream of the starting position, on the one hand, the inlet and outlet of the processing tank have sufficient pressure difference to ensure the flow in the tank, and on the other hand, the flow caused by the reverse flow in the processing casing tank is reduced as much as possible loss. The flow in the treatment tank meets:

$\mathrm{<span\; class="notranslate">\; 0.5</span>}<span\; class="notranslate">\; \&le;</span>\frac{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; slot</span>}}}{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; mean</span>}}}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; 1.0</span>}$

Among them, m _slot is the mass flow rate in the treatment tank, and m _mean is the average mass flow rate of the main flow of the rotor.

(6) Determine the specific form of processing the casing slot. To design the specific form of the treatment casing slot, on the one hand, it is necessary to ensure that the low-energy fluid at the rotor tip can easily enter the treatment slot at the initial position, that is, the radial direction of the treatment casing slot at this position should be aligned with the velocity direction of the low-energy fluid mass , On the other hand, reduce the flow loss caused by the processing casing as much as possible, for example, choose the form of the inlet and outlet of the processing tank to reduce the mixing loss of the inlet and outlet of the processing tank, and design a reasonable internal form of the processing tank to reduce the internal flow loss of the processing tank.

Description of drawings

Fig. 1 is a schematic cross-sectional view of an axial chute processing casing of the prior art, (a), (b), and (c) are respectively a front view, a top view and a side view;

Fig. 2 is a schematic cross-sectional view of a blade chord groove processing casing in the prior art, (a), (b), and (c) are respectively a front view, a top view and a side view;

Figure 3 is a schematic cross-sectional view of the anti-vortex shallow groove treatment casing of the prior art, (a), (b), and (c) are respectively the main view, top view and side view;

Fig. 4 is a schematic diagram of the meridian surface processing casing;

Figure 5 is a schematic diagram of the structural form of the arc chute processing casing of the example, (a) is the main view, (b) is the A-A sectional view, and (c) is the B-direction view;

Fig. 6 is the flow pressure ratio characteristic curve at 65% of the design speed and 98% of the design speed of the supersonic compressor stage with or without the treatment casing;

Fig. 7 is the flow efficiency characteristic curve of the supersonic compressor stage with or without the treatment casing at 65% of the design speed and 98% of the design speed.

Detailed ways

The specific embodiment of the present invention is illustrated with examples. According to the above-mentioned treatment casing design method, a single-stage treatment casing of an axial-flow supersonic compressor is designed, and its effect is verified by experiments.

The design parameters of the supersonic compressor rotor are shown in Table 1.

Table 1 Design parameters of axial flow supersonic compressor rotor

Firstly, the structure form of the flow field dominated by the tip of the rotor is determined by means of experiments, the space-time structure of the unsteady flow field is analyzed, and the flow frequency and initial position are determined.

According to method (4), the number of slots in the processing casing is determined to be 88.

The geometrical parameters shown in Figure 4 are used to define the position of the treatment casing relative to the rotor. A part of the compressor casing 2 above the rotor 1 is subjected to casing processing, and the inlet 4 and outlet 5 of the processing casing 3 define the relative position of the processing casing above the rotor. The axial chord length of the rotor blade tip is L, the distance between the processing casing inlet 4 and the leading edge of the rotor blade tip is S1, and the distance between the processing casing outlet 5 and the leading edge of the rotor blade tip is S2.

Define the overlapping amount λ1 of the processing case as:

${\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}$

Define the forward reach λ2 of the processing casing as:

${\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}$

Determine the position of the processing casing according to method (5): λ1=35%, λ2=78%.

According to the method (6), the form of the circular-arc chute type treatment tank is selected, wherein the radial angle of the treatment tank is α=45°, as shown in Fig. 5 .

Figure 6 and Figure 7 are the characteristic curves of the stage pressure ratio efficiency of the compressor with or without the treatment casing. It can be seen from the figure that regardless of low speed or high speed, under the condition that the efficiency is basically unchanged, the stable working margin of the compressor has been greatly improved. The 65% design speed stability margin is increased from 28.54% to 96.96%, and the 98% design speed stability margin is increased from 11.38% to 39.08%.

Claims (5)

1, a kind of design method of fan/compressor processor box, it is characterized in that on the basis of analyzing the non-permanent space time structure of fan/compressor level rotor flow field, determine that the rotator tip zone accounts for the mobile frequency and the initial position of leading flow field structure form, thereby determine the design parameter of processor box.

2,, it is characterized in that the groove number of processor box satisfies according to the described method for designing box of processor of claim 1: $0.7\&le;\frac{Z\&CenterDot;n}{60\&CenterDot;f}\&le;1.5,$ Wherein, Z is a processor box groove number, and n is rotor speed (rpm), and f is the mobile frequency that rotator tip accounts for leading flow field structure form.

3, according to the described method for designing box of processor of claim 1, it is characterized in that the position of processor box is determined as follows: the processor box import or export is positioned at the initial position that rotator tip accounts for the major flow field structure; The position of the other end of processor box is positioned at this initial position upstream or downstream, makes the import and export of treatment trough have enough pressure reduction to guarantee to flow in the groove on the one hand, reduces the flow losses that flow backwards and bring in the processor box groove on the other hand as far as possible; Flow satisfies in the treatment trough: $0.5\&le;\frac{m_{\mathrm{slot}}}{m_{\mathrm{mean}}}\&le;1.0,$ M wherein _SlotBe mass flow rate in the treatment trough, m _MeanBe rotor main flow mean mass flux.

4, according to the described method for designing box of processor of claim 1, the concrete form that it is characterized in that the groove of processor box is determined as follows: will guarantee that low energy fluid is in the more or less freely treatment trough inside that enters of initial position on the one hand, promptly should aim at the velocity attitude of low energy fluid group in the radial direction of this position processor box groove, on the other hand, reduce the flow losses that processor box brings as far as possible.

5, according to the described method for designing box of processor of claim 1, the concrete form that it is characterized in that the groove of processor box is the arc slot form.

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