A method for regulating turbine flow capacity based on casing jet.

Abstract

This invention provides a method for adjusting turbine flow capacity based on casing jet injection, belonging to the field of turbine technology. A jet injection channel is provided in the casing, located near the throat. Airflow from the high-pressure compressor passes through the jet injection channel and enters the guide vane passage. When no jet injection is applied, the fluid near the endwall migrates towards the suction side due to the lateral pressure gradient, forming a channel vortex. By injecting jet injection into the casing, a flow separation zone is generated on the inner surface of the casing. Simultaneously, the aforementioned migrating flow is enhanced, and a portion of the mainstream flow downstream of the jet injection point is entrained by the high-momentum jet flow. The two flows mix, causing premature and extensive separation in the guide vane corner region. The low-energy fluid regions generated by these two separations affect the effective flow area of ​​the mainstream flow, altering the guide vane's flow capacity. This invention avoids the difficulties of applying existing geometric adjustments to high-pressure turbines and the increased complexity of the internal cooling structure of the blades caused by aerodynamic adjustments.

Description

Technical Field

[0001] This invention provides a method for adjusting turbine flow capacity based on casing jet, belonging to the field of turbine technology. Background Technology

[0002] Variable cycle engines require a wide range of adjustable turbine flow rates. The most direct effect of turbine flow regulation is to enable the engine to operate efficiently under various conditions, including subsonic cruise and supersonic flight. Traditional turbofan engines have a fundamental design flaw: they are either highly efficient but lack thrust at subsonic speeds, or have strong thrust but poor fuel economy at supersonic speeds. Turbine flow regulation technology, by altering the turbine's flow capacity, can dynamically adjust the engine's bypass ratio and thrust output.

[0003] Traditional geometric adjustment controls turbine flow by altering the guide vane installation angle and consequently the throat area. This method allows for precise flow regulation and is currently widely used in low-pressure turbines. However, future engines require adjustable flow rates in high-pressure turbine guide vanes, and the inherent limitations of geometric adjustment significantly restrict its application in next-generation engines: for example, increased mechanical complexity and weight, high-temperature reliability issues, and clearance leakage and efficiency losses. Therefore, the application of geometric adjustment in high-pressure turbine guide vanes struggles to simultaneously meet the requirements of lightweight design and efficient multi-condition adjustment.

[0004] Aerodynamic control technology alters flow capacity by injecting cool air onto the blade surface. Similar to film cooling chamber induced draft, a jet of cool air is injected into the flow channel. The interaction between the jet and the main flow creates a separation zone, changing the aerodynamic area at the throat of the flow channel and thus regulating the flow rate. This technology holds promise as one of the future flow control methods for high-pressure turbine guide vanes, but it places extremely high demands on jet flow rate. Unlike film cooling, which requires a higher blow-off ratio, aerodynamic control increases the structural complexity of the internal cool air chamber of the blade, making high-pressure turbine guide vanes more difficult to manufacture. Summary of the Invention

[0005] The purpose of this invention is to propose a turbine flow capacity adjustment method based on casing jet injection. By setting jet slots in the casing and injecting high-momentum fluid into the channel, the flow capacity is changed through the interaction between the secondary flow and the main flow. This avoids the problems of the high difficulty of applying existing geometric adjustment to high-pressure turbines and the increased complexity of the internal cooling structure of the blades caused by aerodynamic adjustment.

[0006] The specific technical solution is as follows:

[0007] A method for adjusting turbine flow capacity based on casing jetting involves setting jetting slots in the casing; calculating the throat position using a prototype blade cascade; and placing the jetting slots near the throat position.

[0008] After being drawn into the airflow by the high-pressure compressor through the jet channels, the airflow enters the guide vane passage. Without jet injection, the fluid near the endwall is driven towards the suction side by the lateral pressure gradient, forming a channel vortex. Jet injection in the casing creates a flow separation zone on the inner surface of the casing, simultaneously strengthening the aforementioned migrating flow. Near the jet position, a portion of the mainstream is entrained by the high-momentum jet flow, and the two mix, causing premature large-scale separation in the guide vane corner region. The low-energy fluid regions generated by these two separations affect the effective flow area of ​​the mainstream, altering the guide vane's flow capacity. Given the blade design, a three-dimensional flow field calculation of the prototype flow channel is first performed using numerical simulation. By solving the Reynolds-averaged Navier-Stokes equations, the Mach number distribution characteristics within the flow channel are obtained. The contour line of Mach number 1 corresponds to the critical section position AB at the throat of the flow channel. The critical section is marked A on the guide vane pressure surface and B on the suction surface; this position directly determines the maximum flow capacity of the flow channel. By arranging the jet channels near this location, the flow capacity can be adjusted. The maximum limit for jet flow rate is 7% of the mainstream inlet mass flow rate. Connect AB with a straight line, and install a jet slot on the casing near this point. The width of the jet slot should be designed with reference to the film cooling orifice diameter d = 0.6~0.8mm.

[0009] Based on the geometric throat AB, the jet slot is arranged parallel to the straight line AB and located at a distance L in front of it. For a given airfoil, L is a fixed value. The selection of the jet slot position satisfies the following condition: L = (0.2~0.4)AB.

[0010] The jet direction has an angle θ between itself and the axial direction of 90° to 150°, and an angle α between itself and the axial direction of 30° to 60°. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the structure of the present invention;

[0012] Figure 2 This is a schematic diagram of the circumferential flow development topology of the present invention;

[0013] Figure 3 This is a schematic diagram of the axial flow development topology of the present invention;

[0014] Figure 4 This is a schematic diagram defining the location of the jet groove in this invention;

[0015] Figure 5 This is a schematic diagram of the three-dimensional flow topology of the present invention;

[0016] Figure 6 To determine the throat location of the prototype turbine (ordinary casing) in the embodiment;

[0017] Figure 7A comparison diagram of the limiting streamlines of the impeller surface of the embodiment casing jet (left) and the prototype turbine (right);

[0018] Figure 8 This is a comparison diagram of the streamlines near the corner of the casing jet (left) in the embodiment and the turbine (right) in the prototype. Detailed Implementation

[0019] The specific technical solution of the present invention will be described in conjunction with the accompanying drawings.

[0020] like Figure 1 As shown, this invention proposes a method for adjusting turbine flow capacity based on casing jet injection. A jet groove 1 is provided on the casing 4 of the prototype guide vane. The throat position AB, guide vane pressure surface 3 position A, and suction surface 2 position B are calculated using the prototype blade cascade. After being guided by a high-pressure compressor through the jet groove, the airflow enters the guide vane passage. Without jet injection, the fluid near the endwall is affected by the lateral pressure gradient and migrates towards the suction surface, forming a channel vortex. By injecting air into the casing, a flow separation zone is generated on the inner surface of the casing. Simultaneously, the aforementioned migrating flow is enhanced. Near the downstream of the jet injection position, part of the mainstream is entrained by the high-momentum jet flow. The two mix, causing premature large-scale separation in the guide vane corner region. The low-energy fluid regions generated by these two separations affect the effective flow area of ​​the mainstream, thus altering the guide vane's flow capacity. Figure 3 The schematic diagram of axial flow development also shows that the secondary flow development range near the end wall is enhanced by jet injection from the casing, and the spanwise height of the aerodynamic throat is reduced.

[0021]

[0022] As can be seen from the above flow formula, under the premise that the total temperature and total pressure of the incoming flow remain constant, by changing the aerodynamic throat area A... cr This allows for the control of mainstream traffic, providing theoretical support for the present invention.

[0023] Parameter settings for this invention:

[0024] Given the blade design, a three-dimensional flow field calculation of the prototype flow channel is first performed using numerical simulation. By solving the Reynolds-averaged Navier-Stokes equations (RANS), the Mach number distribution characteristics within the flow channel can be accurately obtained. The contour line with a Mach number of 1 corresponds to the critical section position AB at the throat of the flow channel, which directly determines the maximum flow capacity of the flow channel. By arranging the jet slot 1 near this location, the flow capacity can be adjusted. Considering the cooling burden on the turbine guide vane, the maximum jet flow rate limit in this invention is 7% of the mainstream inlet mass flow rate. Connecting AB with a straight line, the jet slot 1 is installed on the casing near this location. Considering the jet flow rate limit and to prevent mainstream intrusion, the width of the jet slot 1 is designed with a reference film cooling orifice diameter d = 0.6~0.8 mm.

[0025] Since the low-energy fluid region generated by the jet is located precisely at the throat, its effect on flow capacity regulation is better. Furthermore, the forward or backward offset of the jet position significantly affects flow separation characteristics. For example, if the jet position is too far forward, the resulting separation zone is larger, and bleed air loss increases sharply. Therefore, taking the geometric throat AB as a reference, the jet slot is arranged parallel to the straight line AB and located at a distance L in front of it. For a given airfoil, L is a fixed value. The selection of the jet slot position should satisfy the following condition: L = (0.2~0.4)AB. Figure 4 As shown.

[0026] Considering the significant aerodynamic losses caused by counter-current jetting, and to ensure better flow capacity regulation under the same cooling gas parameters, taking into account manufacturing constraints and the possibility of combustion gas intrusion in practical applications, the recommended range for the jetting direction angle θ with the axial direction is 90° to 150°, and the recommended range for the jetting direction angle α with the circumferential direction is 30° to 60°. Figure 3 and Figure 5 The definitions of the included angles in the circumferential and axial directions are given respectively.

[0027] This embodiment takes a certain type of high-pressure turbine guide vane as an example, and uses the casing of the present invention to perform numerical simulation. First, the position of the geometric throat is determined, such as... Figure 6 Then, a casing with a jet angle of 90°, a slot width of 0.6mm, and a jet volume of L=0.2AB was designed, with the jet volume being 3% of the mainstream inlet mass flow rate.

[0028] Compared to the prototype casing, the casing of this invention expands the influence range of the secondary flow due to the interaction between the jet stream and the mainstream, such as... Figure 7 and Figure 8 This effectively blocked the main flow area. Calculations showed that the main flow rate decreased by 5%, thus the use of the casing of this invention effectively changed the flow capacity of the guide vanes.

[0029] This invention proposes a novel method for adjusting turbine flow capacity, which uses a casing with jet grooves to achieve flow capacity adjustment without requiring additional mechanical adjustable structures or complex internal blade cooling structures.

Claims

1. A method for adjusting turbine flow capacity based on casing jet, characterized in that, A jet chute is provided on the casing (4); the throat position is calculated using the prototype blade cascade, and the jet chute is located near the throat position; After being guided by the high-pressure compressor through the jet groove, the air enters the guide vane channel. When no jet is applied, the fluid near the end wall is affected by the lateral pressure gradient and migrates towards the suction side, forming a channel vortex. By applying jet in the casing (4), a flow separation zone is generated on the inner surface of the casing (4). At the same time, the above-mentioned migration flow is strengthened. Near the downstream of the jet position, part of the mainstream is entrained by the high-momentum jet flow. The two mix, causing the guide vane corner area to separate in advance. The low-energy fluid zone generated by the above two separations affects the effective flow area of ​​the mainstream and changes the flow capacity of the guide vane.

2. The method for adjusting turbine flow capacity based on casing jet according to claim 1, characterized in that, Given the blade shape, the three-dimensional flow field of the prototype flow channel is first calculated using numerical simulation. The Mach number distribution characteristics within the flow channel are obtained by solving the Reynolds-averaged Navier-Stokes equations. The contour line with a Mach number of 1 corresponds to the critical section position AB of the throat of the flow channel. The critical section is marked as A on the guide vane pressure surface (3) and B on the suction surface (2). This position directly determines the maximum flow capacity of the flow channel. The flow capacity can be adjusted by arranging the jet slot near this location.

3. The method for adjusting turbine flow capacity based on casing jetting according to claim 2, characterized in that, The maximum limit for jet flow rate is 7% of the mainstream inlet mass flow rate; the design reference for jet slot width is film cooling orifice diameter d=0.6~0.8mm.

4. The method for adjusting turbine flow capacity based on casing jetting according to claim 2, characterized in that, Based on the geometric throat AB, the jet slots are arranged parallel to the straight line AB and located at a distance L in front of it. For a given airfoil, L is a fixed value. The selection of the jet slot position satisfies the following condition: L = (0.2~0.4)AB. The jet direction has an angle θ between itself and the axial direction of 90° to 150°, and an angle α between itself and the axial direction of 30° to 60°.

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