A design method of asymmetric nozzle under strong geometric constraints

Abstract

The application relates to a design method of an asymmetric tail nozzle under strong geometric constraints, and belongs to the technical field of engines. Compared with the prior art, the design method of the asymmetric tail nozzle under strong geometric constraints can meet the given strong geometric constraints by simplifying the lower wall surface of the nozzle into a straight line and controlling the initial expansion circular-arc segment matching outlet position constraints, and the designed nozzle length is short due to the adoption of the circular-arc initial expansion, so that the structure is beneficial to realization and has good realizability.

Description

Technical Field

[0001] This invention belongs to the field of engine technology and relates to an asymmetric tail nozzle design method under strong geometric constraints. Background Technology

[0002] The exhaust nozzle, by accelerating and expelling expanded combustion gases, provides thrust to an aircraft and is a crucial component of various engines. The design of the exhaust nozzle profile is key to the efficient expansion of the combustion gases. Most commonly used profile design methods are developed based on the characteristic line method. Designers can obtain different exhaust nozzle profiles by using different design strategies, given boundary conditions, and solving the equations along the characteristic lines and streamlines. High Mach number engines often employ asymmetric profiles for their ventral nozzles, allowing for integrated design with the aircraft.

[0003] The book *Intake and Exhaust Systems of High-Speed ​​Aircraft Engines* presents an asymmetric nozzle design method. This method designs an asymmetric nozzle profile where the upper wall profile consists of an initial expansion section and a wave-damping section, while the lower wall profile consists of an initial expansion section, a straight section, and a wave-damping section. By giving the ratio of the upper and lower initial expansion angles of the nozzle, the complete profile of the asymmetric nozzle can be designed using the method of characteristics. However, the asymmetric nozzle design method presented in this book cannot directly provide a nozzle profile that matches strong geometric constraints. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] The technical problem to be solved by this invention is: how to design an asymmetric nozzle design method with good feasibility.

[0006] (II) Technical Solution

[0007] To address the aforementioned technical problems, this invention provides an asymmetric nozzle design method under strong geometric constraints. The method is based on the feature line method, whereby the lower wall of the nozzle is simplified to a straight line, and the nozzle profile is designed by controlling the initial expansion arc segment to match the exit position constraint.

[0008] Preferably, in this method, the upper wall profile of the tail nozzle is composed of two parts: the initial expansion arc segment TB and the change-direction segment BE. The lower wall profile of the tail nozzle is a straight line T1E1. The geometric constraints are the position of the exit point E and the expansion angle θ of the lower wall.

[0009] Preferably, the asymmetric nozzle design method includes the following steps:

[0010] Step 1: Given the position of the endpoint B of the initial expansion arc segment, use the characteristic line method to determine the position of the intersection point E1' of the rightward characteristic line passing through B and the straight line of the lower wall passing through T1, through the initial expansion arc segment TB profile and the expansion angle θ of the lower wall. Solve for the Mach number and flow deflection angle on the rightward characteristic line BE1'.

[0011] Step 2: Use the deflection zone solution method to solve for the Mach number and flow deflection angle on the left-moving characteristic line E1'E' passing through point E1' and the deflection segment profile BE' on the upper wall;

[0012] Step 3: Determine whether the position (x, y) of the exit point E in the geometric constraints is on the shape line BE' of the upper wall turning segment: If not, adjust the position of point B and return to Step 1; if it is, proceed to the next step.

[0013] Step 4: Based on the position of the outlet point E on the upper wall, interpolate to obtain the Mach number and flow deflection angle on the left-hand characteristic line E1DE passing through point E, and obtain the position of E1. At this point, the nozzle profile design is completed.

[0014] The present invention also provides an asymmetric tail nozzle designed using the method described above.

[0015] The present invention also provides a method for operating the asymmetric tail nozzle.

[0016] The present invention also provides an engine using the aforementioned asymmetric exhaust nozzle.

[0017] The present invention also provides a method for operating the engine.

[0018] The present invention also provides an aircraft using the said engine.

[0019] The present invention also provides a method for operating the aforementioned aircraft.

[0020] (III) Beneficial Effects

[0021] Compared with the prior art, the asymmetric nozzle design method under strong geometric constraints proposed in this invention simplifies the lower wall of the nozzle to a straight line and controls the initial expansion arc segment to match the exit position constraint, which can meet the given strong geometric constraints. At the same time, due to the use of arc initial expansion, the nozzle length is shorter, which is conducive to structural realization and has good feasibility. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating the profile solving principle of the asymmetric tail nozzle design method under strong constraints of the present invention.

[0023] Figure 2This is the main flowchart of the asymmetric tail nozzle design method under strong constraints of the present invention. Detailed Implementation

[0024] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0025] Based on the feature line method, this invention proposes in detail an asymmetric nozzle design method under strong geometric constraints. One of the key design points is to simplify the lower wall of the nozzle into a straight line; the other is to control the initial expansion arc segment to match the exit position constraint.

[0026] Figure 1 This is a schematic diagram illustrating the profile solving principle of an asymmetric nozzle design method under strong geometric constraints provided by this invention. The upper wall profile of the nozzle consists of two parts: the initial expansion arc segment TB and the direction-changing segment BE. The lower wall profile is a straight line T1E1. The geometric constraints are the position of the exit point E and the lower wall expansion angle θ.

[0027] based on Figure 1 Based on the principle of profile solving, this invention derives a method for designing asymmetric nozzles under strong geometric constraints, implemented using the characteristic line method. (Reference) Figure 2 The main flowchart of the present invention shows that the asymmetric nozzle design method proposed in this invention includes the following steps:

[0028] (1) Step 1: Given the position of the endpoint B of the initial expansion arc segment, use the characteristic line method to determine the position of the intersection point E1' of the rightward characteristic line passing through B and the straight line of the lower wall passing through T1, through the initial expansion arc segment TB profile and the expansion angle (deflection angle) θ of the lower wall. Solve for the Mach number and flow deflection angle on the rightward characteristic line BE1'.

[0029] (2) Step 2: Use the deflection zone solution method to solve the Mach number and flow deflection angle on the left-moving characteristic line E1'E' passing through point E1' and the deflection section profile BE' on the upper wall;

[0030] (3) Step 3: Determine whether the position (x,y) of the exit point E in the geometric constraints is on the shape line BE' of the upper wall turning segment: If not, adjust the position of point B and return to step 1; if it is, proceed to the next step.

[0031] (4) Step 4: Based on the position of the outlet point E on the upper wall, interpolate to obtain the Mach number and flow deflection angle on the leftward characteristic line E1DE passing through point E, and obtain the position of E1. At this point, the nozzle profile design is completed.

[0032] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for designing an asymmetric nozzle under strong geometric constraints, characterized in that, This method is based on the feature line method, in which the nozzle profile is designed by simplifying the lower wall of the nozzle into a straight line and controlling the initial expansion arc segment to match the exit position constraint. Assume the upper wall profile of the nozzle is composed of two parts: the initial expansion arc segment TB and the change-direction segment BE. The lower wall profile of the nozzle is a straight line T1E1. The geometric constraints are the position of the exit point E and the expansion angle θ of the lower wall. The asymmetric nozzle design method includes the following steps: Step 1: Given the position of the endpoint B of the initial expansion arc segment, use the characteristic line method to determine the position of the intersection point E1' of the rightward characteristic line passing through B and the straight line of the lower wall passing through T1, through the initial expansion arc segment TB profile and the expansion angle θ of the lower wall. Solve for the Mach number and flow deflection angle on the rightward characteristic line BE1'. Step 2: Use the deflection zone solution method to solve for the Mach number and flow deflection angle on the left-moving characteristic line E1'E' passing through point E1' and the deflection segment profile BE' on the upper wall; Step 3: Determine whether the position (x, y) of the exit point E in the geometric constraints is on the shape line BE' of the upper wall turning segment: If not, adjust the position of point B and return to Step 1; if it is, proceed to the next step. Step 4: Based on the position of the outlet point E on the upper wall, interpolate to obtain the Mach number and flow deflection angle on the left-hand characteristic line E1DE passing through point E, and obtain the position of E1. At this point, the nozzle profile design is completed.

2. An asymmetric tail nozzle designed using the method described in claim 1.

3. An engine using the asymmetric exhaust nozzle as described in claim 2.

4. The engine as described in claim 3, characterized in that, The engine is a high Mach number engine.

5. An aircraft using the engine as described in claim 4.

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