A compact ultra-wide operating condition turbine design method applied to cross-medium engines

Abstract

The application aims to provide a compact super-wide working condition turbine design method applied to a cross-medium engine, wherein a turbine disc diameter is determined according to the size requirement of the cross-medium engine, boundary conditions and physical parameters of the air flight working condition turbine are set, geometric parameters of a nozzle and a turbine rotor are calculated, fluid force simulation calculation and fluid-thermal-solid coupling simulation calculation of the air flight working condition turbine are carried out, boundary conditions and physical parameters of the underwater running working condition turbine are set, geometric parameters of the nozzle are calculated, and fluid force simulation calculation of the underwater running working condition is carried out. In the design process, the air flight working condition turbine efficiency, the underwater running working condition turbine efficiency, the rotor stress requirement and the local air intake rate are taken as the determination conditions for cyclic iteration until the design requirement is met. The application mainly designs the air flight working condition turbine and considers the underwater running working condition turbine, and the two working condition turbines use the same set of turbine rotors, so that the design purposes of super-wide working condition and compactness are achieved.

Description

Technical Field

[0001] The present invention relates to a cross-medium engine design method, specifically a turbine design method. Background Technology

[0002] A cross-medium aircraft is a novel concept aircraft that can navigate both water and air, possessing the versatility of rapid deployment and high-speed flight in the air while also being capable of underwater navigation. Compared to conventional aircraft, cross-medium aircraft present more technical challenges. Structural layout, power source, and the method of achieving cross-medium operation are the key design difficulties. The structural layout determines the compactness of the device and constrains the aircraft's maneuverability and range during operation.

[0003] As a core component of cross-medium power plants, turbines are essentially a type of fluid machinery that continuously extracts mechanical energy through the expansion of the working fluid. Power turbines applicable to cross-medium engines can meet the requirements of cross-medium power plants in terms of compactness and reliability, and can greatly reduce the overall size and weight of the engine, which has great practical significance for the production and manufacturing of cross-medium engines and even cross-medium aircraft. Summary of the Invention

[0004] The purpose of this invention is to provide a compact, ultra-wide operating condition turbine design method for cross-medium engines that can simultaneously meet the operating conditions of air flight and underwater navigation.

[0005] The objective of this invention is achieved as follows:

[0006] This invention discloses a compact, ultra-wide operating condition turbine design method for transmedium engines, characterized by:

[0007] (1) Determine the turbine disk diameter D according to the cross-medium engine's external dimensions and design requirements. m ;

[0008] (2) Set the turbine boundary conditions and physical property parameters for in-flight operation;

[0009] (3) Assuming turbine efficiency η during flight conditions ap ;

[0010] (4) Design of turbine nozzles for in-flight operation;

[0011] (5) Determine the turbine blade height H;

[0012] (6) Design the turbine rotor;

[0013] (7) Perform computational fluid dynamics simulation calculations on turbines under in-flight operating conditions;

[0014] (8) Determine whether the turbine efficiency meets the standard under the in-flight operating conditions. If it does not meet the standard, update the efficiency value and return to step (3) to iterate again. If it meets the standard, continue to the next step.

[0015] (9) Perform fluid-thermal-structure interaction simulation calculations on turbines under in-flight operating conditions;

[0016] (10) Determine whether the maximum stress of the turbine rotor under the air flight condition is less than the allowable stress. If the maximum stress of the rotor is less than the allowable stress, continue to the next step; if the stress of the rotor is greater than the allowable stress, return to step (1) and iterate again until the stress requirement is met.

[0017] (11) Assuming turbine efficiency η under underwater operating conditions wp ;

[0018] (12) Set the turbine boundary conditions and physical property parameters for underwater operation;

[0019] (13) Design of nozzles for underwater operation;

[0020] (14) Calculate the sum of the turbine local intake rates ε;

[0021] (15) Determine if the local air intake rate is less than 1. If it is less than 1, continue to the next step. If it is greater than 1, return to step (1) and iterate again.

[0022] (16) Perform computational fluid dynamics simulation on the turbine operating under underwater conditions;

[0023] (17) Determine whether the turbine efficiency under underwater operating conditions meets the standard. If it does, continue to the next step. If it does not meet the standard, return to step (11) and iterate again.

[0024] If the above steps are completed, the turbine aerodynamic and geometric parameters will be designed.

[0025] The present invention may also include:

[0026] 1. The parameters in step (2) include: total pressure at the nozzle inlet. Total temperature at nozzle inlet Turbine outlet pressure P 2,a Gas mass flow rate Specific heat capacity of gas at constant pressure C P,a Specific heat ratio of fuel gas (k) a Specific gas constant R of the fuel g,a Turbine design speed n a The subscript 'a' indicates various parameters under aerial operating conditions.

[0027] 2. Step (4) includes:

[0028] Select the nozzle exit angle θ, with a value range of 12° to 16°; select the nozzle expansion angle γ, with a value range of 6° to 10°; nozzle exit static pressure: P1 = P2; φ is the nozzle velocity coefficient, with a value range of 0.9 to 0.98.

[0029] Isentropic enthalpy drop during nozzle stagnation:

[0030]

[0031] Nozzle loss enthalpy drop:

[0032]

[0033] Isentropic temperature at nozzle exit:

[0034]

[0035] Nozzle exit static temperature:

[0036]

[0037] isentropic velocity at nozzle exit:

[0038]

[0039] Actual nozzle exit velocity:

[0040] C1 = C 1s φ Nozzle outlet total temperature:

[0041]

[0042] Nozzle exit density:

[0043]

[0044] Total pressure at nozzle exit:

[0045]

[0046] Local speed of sound at nozzle exit:

[0047]

[0048] Nozzle exit Mach number:

[0049]

[0050] Nozzle throat velocity:

[0051]

[0052] Nozzle throat temperature:

[0053]

[0054] Nozzle throat pressure:

[0055]

[0056] Nozzle throat density:

[0057]

[0058] Nozzle throat area:

[0059]

[0060] Nozzle throat diameter:

[0061]

[0062] Nozzle exit area:

[0063]

[0064] Nozzle exit diameter:

[0065]

[0066] Nozzle extension length:

[0067]

[0068] Where P represents pressure, T represents temperature, ρ represents density, and h represents enthalpy. The value represents mass flow rate. Subscript '0' indicates nozzle inlet parameters, subscript '1' indicates nozzle outlet parameters, subscript 'cr' indicates nozzle throat parameters, subscript '2' indicates turbine outlet parameters, and superscript '*' indicates stagnation parameters.

[0069] 3. Step (5) Turbine blade height H = d1 + H t H t It is the difference between the height of the turbine blade and the nozzle exit diameter d1, and its value ranges from 0.5 to 4 mm.

[0070] 4. Step (6) Design the turbine rotor specifically as follows:

[0071] After determining the blade height of the turbine blade, the two-dimensional profile of the blade is designed. The parameters that need to be determined for the two-dimensional profile include: chord length B. l , blade geometric intake angle β 1n β, the geometric outlet angle of the blades 2n and take β 1n =β 2n =β1, where β1 is the relative intake angle.

[0072] Bl =r(cosβ) 1n +cosβ 2n )

[0073] For the optimal relative pitch between the moving blades, a value of 0.57 was initially selected in the preliminary calculations.

[0074]

[0075]

[0076]

[0077] Where Z is the number of blades calculated in the trial, Z b The number of blades is the rounded-up number. After rounding, the pitch t is corrected using the above formula.

[0078] The pressure side profile is composed of circular arcs with radius r:

[0079]

[0080] The drawing method steps are as follows:

[0081] Draw the chord length B of the leaf shape. l Determine the radius r according to the formula for the radius of the arc of the pressure side profile; take any point A on the inlet edge, and draw AP along the turbine shaft axis; draw AL at an angle β to AP. 1n Angle, on line AL, intercept AO equal to radius r; with O as center and r as radius, draw the pressure side profile, intersecting the outlet edge at point B; draw tangents to the arc of the pressure side profile through points A and B, forming angles β with the inlet and outlet edges respectively. 1n and β 2n After selecting the edge thickness s'0, draw a straight line of suction side blade shape and intersect the B'C part at point C; cut BB” from point B to be equal to the pitch t, ​​draw a perpendicular line from point B” to B'C, extend this perpendicular line and intersect the angle bisector of ∠A'CB' at point O', so as to determine the curvature center O' and curvature radius r' of the arc on the back of the blade;

[0082] Wherein, s'0 and s'0' are the blade edge thicknesses in the inlet and outlet directions, respectively, and s′0 = s″0 = 0.5~1mm.

[0083] 5. The parameters for step (12) include: total pressure at the nozzle inlet. Total temperature at nozzle inlet Turbine outlet pressure P 2,w Gas mass flow rate Specific heat capacity of gas at constant pressure C P,w Specific heat ratio of fuel gas (k) w Specific gas constant R of the fuelg,w Turbine design speed n w The subscript w indicates various parameters under underwater operating conditions.

[0084] 6. The sum of the turbine local air intake rates ε in step (14) is the sum of the turbine nozzle air intake rates under air flight conditions and underwater operation conditions:

[0085]

[0086]

[0087] Where s is the nozzle exit point at the average diameter D m Location arc length, Z n ε represents the number of nozzles and ε represents the partial air intake rate.

[0088] 7. The turbine disk diameter D mentioned in step (1) m The design requirements are given under the overall design conditions of the cross-medium engine, and D is directly given when designing the turbine. m The specific value.

[0089] 8. Step (4) The turbine nozzle used in the air flight condition is a drilled nozzle, which is either a circular nozzle or a rectangular nozzle.

[0090] 9. Step (5) Turbine blade height, the value of which is selected according to the nozzle outlet diameter in the range of 1mm-30mm, and the blade height H is greater than the nozzle outlet diameter.

[0091] 10. Step (8) The turbine efficiency under in-flight operating conditions is the total static expansion efficiency, which is defined as:

[0092]

[0093] Where, η a For turbine efficiency under in-flight operating conditions, T2 * P2 is the turbine outlet total temperature, P2 is the turbine outlet static pressure, and k is the working fluid adiabatic index.

[0094] 11. Step (13) The turbine nozzle in underwater operation is a drilled nozzle.

[0095] 12. In step (17), the turbine efficiency under underwater operating conditions is the total static expansion efficiency, which is defined as:

[0096]

[0097] Where, η w For turbine efficiency under underwater operating conditions, T2 * P2 is the turbine outlet total temperature, P2 is the turbine outlet static pressure, and k is the working fluid adiabatic index.

[0098] The advantages of this invention are: it can meet the requirements of cross-medium engine use, and can drive the compressor and water pump inside the cross-medium engine to work in both air flight and underwater operation conditions. It has excellent characteristics of being compatible with both air and underwater operation conditions, being compact and highly reliable, and having a high power density. Attached Figure Description

[0099] Figure 1 This is a schematic diagram illustrating the working principle of the cross-medium engine of the present invention;

[0100] Figure 2 This is a schematic diagram of a turbine stator nozzle;

[0101] Figure 3 A schematic diagram and equation of the converging section of the turbine stator nozzle;

[0102] Figure 4 A schematic diagram illustrating the method for drawing a single turbine blade and its airfoil.

[0103] Figure 5 A schematic diagram of the turbine stator nozzle assembly and turbine disk assembly;

[0104] Figure 6 This is a schematic diagram of the internal streamlines of the turbine passage in a cross-medium engine, calculated using computational fluid dynamics software.

[0105] Figure 7 This is a graph showing the turbine efficiency-speed characteristics.

[0106] Among them, 1 represents the nozzle assembly for airborne operation; 2 represents the nozzle assembly for underwater operation; and 3 represents the turbine blades. Detailed Implementation

[0107] The invention will now be described in more detail with reference to the accompanying drawings:

[0108] Combination Figure 1-7 The present invention features a single-stage, impulse turbine structure that meets the operational requirements of cross-medium vehicles. Its most significant characteristic is its ability to simultaneously operate in both air and underwater modes. When the engine operates in air mode, the gas generated by the gas generator is discharged from the air-operation nozzle assembly. The high-speed gas impacts the turbine blades, driving the turbine disk and turbine shaft to rotate and perform work. The turbine shaft connects to the compressor, where the air drawn in by the compressor mixes and combusts with the gas from the secondary combustion chamber, and is then discharged through the engine's exhaust nozzle, serving as the air propulsion method. When the engine operates underwater mode, the gas generated by the gas generator is discharged from the underwater operation nozzle assembly. The high-speed gas impacts the turbine blades, driving the turbine disk and turbine shaft to rotate and perform work. The turbine shaft connects to the water pump, which draws in water as the working fluid and sprays it out through the water nozzle, serving as the underwater propulsion method.

[0109] The actual flow of the gaseous working medium within a turbine is extremely complex. 1. This flow process is a strongly three-dimensional flow, with the gas changing not only along the flow direction but also radially and tangentially; 2. This process is a periodic flow, with the gaseous working medium ejected from the nozzle sometimes freely passing through the flow channel formed by adjacent blades, and sometimes impacting the working blades; 3. The flow inside the turbine is unsteady, with the fluid's flow state changing over time. Therefore, the following assumptions are necessary in turbine design:

[0110] The working fluid is assumed to be a complete gas;

[0111] Assume that the working fluid flows in one dimension inside the turbine;

[0112] Assuming the working fluid flows steadily inside the turbine, all parameters of the working fluid are independent of time during the flow process;

[0113] Assume that the flow of the working fluid inside the turbine is an adiabatic process, and that there is no heat exchange between the working fluid and the outside environment during the flow.

[0114] Considering the compactness and reliability of the cross-medium engine, the turbine is designed as a single-stage impulse turbine, so the working fluid should impact the turbine blades at the highest possible speed;

[0115] The nozzle employs a slanted, tapering design, with a smooth and continuous contraction curve. The equation for the contraction curve is a Vickers curve, such as... Figure 3 As shown;

[0116] The moving blade adopts an impulse-type blade design, which is composed of straight lines and arcs, such as... Figure 4 As shown, the blade is a straight blade. The pressure surface of the blade is composed of a large circular arc, and the suction surface of the blade is composed of a small circular arc and two straight lines. The thickness direction of the blade edge is a small straight line. Taking into account the length of the minor axis of the elliptical exit of the nozzle assembly in both air flight and underwater navigation conditions, the height of the moving blade at the top and bottom should be higher than the length of the minor axis of the elliptical exit of the nozzle. The length of the upper end exceeding the length of the nozzle is called the upper cover, and the length of the lower end exceeding the length of the nozzle is called the lower cover. Both the upper and lower covers are within the range of 1 to 2 mm to avoid losses caused by radial flow.

[0117] Compared to a full-circumference inlet turbine, a partial inlet turbine incurs additional intake losses, including repulsion losses and blowout losses. Repulsion losses can be minimized by arranging the nozzle assemblies close together; blowout losses can be effectively reduced by installing an exhaust casing. The circumferential arc length of the exhaust casing is slightly longer than that of the nozzle assembly on both sides. Specifically, the arc length of the exhaust casing on the side aligned with the turbine's rotation direction should be slightly longer to collect the gaseous working fluid expelled with the turbine's rotation.

[0118] Implement according to the design methodology and steps:

[0119] Step 1: Determine the turbine disk mean diameter D according to the cross-medium engine's external dimensions and design requirements. m ;

[0120] Step 2: Set the turbine boundary conditions and physical property parameters for in-flight operation;

[0121] Including the following parameters: total pressure at the nozzle inlet Total temperature at nozzle inlet Turbine outlet pressure P 2,a Gas mass flow rate Specific heat capacity of gas at constant pressure C P,a Specific heat ratio of gas k a Specific gas constant R of the fuel g,a Turbine design speed n a (Where, the subscript 'a' represents various parameters under aerial operating conditions.)

[0122] Step 3: Assume turbine efficiency η during flight conditions ap ;

[0123] Step 4: Design the turbine nozzle for in-flight operation;

[0124] Step 5: Determine the turbine blade height H:

[0125] Step Six: Design the turbine rotor;

[0126] Step 7: Perform computational fluid dynamics simulation calculations on the turbine under in-flight operating conditions;

[0127] Step 8: Determine if the turbine efficiency meets the standard under in-flight conditions. If it does not meet the standard, update the efficiency value and return to Step 3 to iterate again. If it meets the standard, continue to the next step.

[0128] Step 9: Perform fluid-thermal-structure interaction simulation calculations on the turbine under in-flight operating conditions;

[0129] Step 10: Determine whether the maximum stress of the turbine rotor under in-flight conditions is less than the allowable stress. If the maximum stress of the rotor is less than the allowable stress, proceed to the next step. If the stress of the rotor is greater than the allowable stress, return to Step 1 and iterate again until the stress requirement is met.

[0130] Step 11: Assume turbine efficiency η under underwater operating conditions wp ;

[0131] Step 12: Set the turbine boundary conditions and physical property parameters for underwater operation;

[0132] Including the following parameters: total pressure at the nozzle inlet Total temperature at nozzle inlet Turbine outlet pressure P2,w Gas mass flow rate Specific heat capacity of gas at constant pressure C P,w Specific heat ratio of gas k w Specific gas constant R of the fuel g,w Turbine design speed n w (Where, the subscript w represents various parameters under underwater operating conditions.)

[0133] Step Thirteen: Design the nozzle for underwater operation;

[0134] Step Fourteen: Calculate the sum of the turbine local intake rates ε;

[0135] Step 15: Determine if the local air intake rate is less than 1. If it is less than 1, proceed to the next step. If it is greater than 1, return to the first step and iterate again.

[0136] Step 16: Perform computational fluid dynamics simulation calculations on the turbine under underwater operating conditions;

[0137] Step 17: Determine whether the turbine efficiency meets the standard under underwater operating conditions. If it does, proceed to the next step. If it does not, return to step 11 and iterate again.

[0138] Through the above steps and iterative processes, a turbine design for a cross-medium engine was completed.

[0139] Some parameters are shown in the table below:

[0140] Turbine Design Parameters Table 1

[0141]

[0142] Turbine Design Parameters Table 2

[0143] <![CDATA[Rotor hub diameter D hub (mm)]]> 60 <![CDATA[Rotor average diameter D m (mm)]]> 68.5 <![CDATA[Number of blades Z b > 34 Leaf height H (mm) 16.8 <![CDATA[Chord length B l (mm)]]> 20 <![CDATA[Geometric intake angle β 1n (°)]]> 21.5 <![CDATA[Geometric outlet flow angle β 1n (°)]]> 21.5

[0144] The completed turbine model is as follows: Figure 5 As shown, the computational fluid dynamics software was used to calculate the turbine fluid domain model under both air flight and underwater navigation conditions, and the calculation results met the design requirements.

Claims

1. A compact turbine design method for a transmedium engine with an ultra-wide operating range, characterized by: (1) Determine the turbine disk mean diameter D according to the external dimensions and design requirements of the cross-medium engine. m ; (2) Set the turbine boundary conditions and physical property parameters for in-flight operation; parameters include: total pressure at the nozzle inlet. Total temperature at the nozzle inlet Turbine outlet pressure Gas mass flow rate Specific heat capacity of gas at constant pressure Specific heat ratio of gas Specific gas constants of fuel gas Turbine design speed subscript This indicates various parameters under aerial operating conditions; (3) Assuming turbine efficiency during flight conditions ; (4) Design the turbine nozzle for in-flight operation; Select nozzle exit angle Its value ranges from 12° to 16°, and the nozzle expansion angle is selected. Its value ranges from 6° to 10°, and the nozzle outlet static pressure is: , This is the nozzle velocity coefficient, with a value ranging from 0.9 to 0.

98. Isentropic enthalpy drop during nozzle stagnation: Nozzle loss enthalpy drop: Isentropic temperature at nozzle exit: Nozzle exit static temperature: isentropic velocity at nozzle exit: Actual nozzle exit velocity: Total nozzle exit temperature: Nozzle exit density: Total pressure at nozzle exit: Local speed of sound at nozzle exit: Nozzle exit Mach number: Nozzle throat velocity: Nozzle throat temperature: Nozzle throat pressure: Nozzle throat density: Nozzle throat area: Nozzle throat diameter: Nozzle exit area: Nozzle exit diameter: Nozzle extension length: Where P represents pressure and T represents temperature. h represents density, and h represents enthalpy. The subscript 'cr' represents the mass flow rate. The subscript 0 indicates the nozzle inlet parameter, the subscript 1 indicates the nozzle outlet parameter, the subscript 'cr' indicates the nozzle throat parameter, the subscript '2' indicates the turbine outlet parameter, and the superscript * indicates the stagnation parameter. (5) Determine the turbine blade height H; H = d1 + H t H t It is the difference between the height of the turbine blade and the nozzle exit diameter d1, and its value ranges from 0.5 to 4 mm. (6) Design the turbine rotor; after determining the blade height of the turbine blade, design the two-dimensional profile of the blade; the parameters that need to be determined for the two-dimensional profile include: chord length , blade geometric intake angle β 1n , blade geometric outlet angle β 2n and take β 1n =β 2n =β1, where β1 is the relative intake angle. For the optimal relative pitch between the moving blades, a value of 0.57 was initially selected in the preliminary calculations. in, For the trial calculation of the number of leaves, The number of blades is the rounded-up number. After rounding, the pitch t is corrected using the above formula. The pressure side profile is composed of a radius of The arc is composed of: The drawing method steps are as follows: Draw the chord length of the leaf shape. The radius is determined according to the formula for the radius of the arc of the pressure side profile. Take any point A on the inlet side, and draw AP along the turbine shaft axis; make an angle between AL and AP. Angle, the point on line AL where AO is equal to the radius. With O as the center, Draw a pressure-side profile with radius A, intersecting the outlet edge at point B; draw tangents to the arc of the pressure-side profile through points A and B, forming angles with the inlet and outlet edges respectively. and Select edge thickness Then, draw a straight line for the suction side blade shape and Partial intersection at point C; cut off from point B equal to pitch From point right Draw a perpendicular line, extend this perpendicular line, and intersect it with... The angle bisectors intersect at Points are used to determine the center of curvature of the arc on the back of the blade. and radius of curvature ; in, and The blade edge thicknesses are taken in the inlet and outlet directions, respectively. ; (7) Perform computational fluid dynamics simulation calculations on the turbine under in-flight operating conditions; (8) Determine whether the turbine efficiency meets the standard under the in-flight operating conditions. If it does not meet the standard, update the efficiency value and return to step (3) to iterate again. If it meets the standard, continue to the next step. (9) Perform fluid-thermal-structure interaction simulation calculations on turbines under in-flight operating conditions; (10) Determine whether the maximum stress of the turbine rotor under the flight condition is less than the allowable stress. If the maximum stress of the rotor is less than the allowable stress, continue to the next step. If the stress of the rotor is greater than the allowable stress, return to step (1) and iterate again until the stress requirement is met. (11) Assume turbine efficiency under underwater operating conditions ; (12) Set the turbine boundary conditions and physical property parameters for underwater operation; parameters include: total pressure at the nozzle inlet. Total temperature at the nozzle inlet Turbine outlet pressure Gas mass flow rate Specific heat capacity of gas at constant pressure Specific heat ratio of gas Specific gas constants of fuel gas Turbine design speed The subscript w indicates various parameters under underwater operating conditions; (13) Design of nozzles for underwater operation; (14) Calculate the sum of the turbine local intake rates ε; (15) Determine if the local air intake rate is less than 1. If it is less than 1, continue to the next step. If it is greater than 1, return to step (1) and iterate again. (16) Perform computational fluid dynamics simulation calculations on the turbine operating underwater; (17) Determine whether the turbine efficiency under underwater operating conditions meets the standard. If it does, proceed to the next step. If it does not meet the standard, return to step (11) and iterate again. If the above steps are completed, the turbine aerodynamic and geometric parameters will be designed.

2. The compact ultra-wide operating condition turbine design method for a transmedium engine according to claim 1, characterized in that: Step (14) The sum of the turbine local air intake rates ε is the sum of the turbine nozzle air intake rates under air flight conditions and underwater operation conditions: Where s is the nozzle exit point at the average diameter D m The arc length occupied by the location, Z n For the number of nozzles, This represents a partial intake rate.

3. The compact ultra-wide operating condition turbine design method for a transmedium engine according to claim 1, characterized in that: The turbine disk diameter D mentioned in step (1) m The design requirements are given under the overall design conditions of the cross-medium engine, and D is directly given when designing the turbine. m The specific value.

4. The compact ultra-wide operating condition turbine design method for a transmedium engine according to claim 1, characterized in that: Step (4) The turbine nozzle used in the air flight condition is a drilled nozzle, which is either a circular nozzle or a rectangular nozzle.

5. The compact ultra-wide operating condition turbine design method for a transmedium engine according to claim 1, characterized in that: Step (5) Turbine blade height, the value of which is selected according to the nozzle exit diameter in the range of 1mm-30mm, and the blade height H is greater than the nozzle exit diameter.

6. The compact ultra-wide operating condition turbine design method for a transmedium engine according to claim 1, characterized in that: Step (8) The turbine efficiency under in-flight operating conditions is the total static expansion efficiency, which is defined as: in, For turbine efficiency under in-flight operating conditions, T2 * The total temperature at the turbine outlet. ρ is the turbine outlet static pressure, and k is the working fluid adiabatic index.

7. The compact ultra-wide operating condition turbine design method for a transmedium engine according to claim 1, characterized in that: Step (13) The turbine nozzle in underwater operation is specifically a drilled nozzle.

8. The compact ultra-wide operating condition turbine design method for a transmedium engine according to claim 1, characterized in that: In step (17), the turbine efficiency under underwater operating conditions is the total static expansion efficiency, which is defined as: in, For turbine efficiency under underwater operating conditions, T2 * The total temperature at the turbine outlet. ρ is the turbine outlet static pressure, and k is the working fluid adiabatic index.

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