Turbo fan cycle for reducing back pressure and raising peak temperature without reducing thrust

Abstract

To realize, while fixing an exhaust nozzle WN of a core, a new concept that a trust can be kept regardless of reduction of a turbine inlet temperature (TIT) by increasing a turbine expansion ratio, increasing a fan rotation speed and increasing a flow rate when an engine back pressure is reduced by widening the exhaust nozzle of the core and the TIT is decreased at the same time.SOLUTION: A value of a cycle parameter or a turbine choke point which determines a reduction range of a TIT and an increase range of a fan rotation speed is determined while taking not only takeoff rating but also a partial load into account so as not to make a turbine expansion ratio excessive, and a cycle is designed so as to perform operation in an exhaust nozzle fixed manner over all operation ranges.EFFECT: 1) A fuel consumption amount per thrust is reduced and an SFC can be improved. 2) The TIT can be decreased without reducing the thrust, thereby reducing a cooling air amount. A turbine lifetime can be prolonged. Cost of manufacture can be reduced. 3) The above 1) and 2) can be achieved while fixing the exhaust nozzle of the core.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] This invention is the creation of a new cycle for turbofan engines. This turbofan is an improvement on the one proposed in Patent Document 1, which recovers part of the energy that would otherwise be wasted in the exhaust, achieving both environmental protection and economic efficiency. [Background technology]

[0002] Aircraft engines, which are required to be lightweight, compact and have high thrust, have been continuously pursued to increase temperature and pressure in order to improve performance. The thrust of a jet engine is governed by the turbine inlet temperature (TIT), which is limited by the melting point of the material. For this reason, advanced turbine air-cooling technology and innovative technology for heat-resistant materials have been developed. However, higher temperatures shorten the turbine's lifespan. Furthermore, if the amount of cooling air used to prevent this is too large, the cycle loss caused by the excess cooling air will exceed the performance improvement due to the higher temperature. Furthermore, the emission of NOx (nitrogen oxides) increases exponentially with the rise in flame temperature in the combustor. NOx is a greenhouse gas. As such, it is difficult to achieve high performance while also conserving resources and taking environmental measures. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent application 2022-117559 [Non-patent literature]

[0004] [Non-Patent Document 1] Mitsuo Morita and Shizuo Sekine, "Off-design Performance of a Multi-spool Turbofan Engine," National Aerospace Laboratory Report No. 347

[0005] [Non-Patent Document 2] "Gas Turbines and Jet Engines" by Keizo Hatta, Kyoritsu Publishing Co., Ltd. Summary of the Invention [Problem to be solved by the invention]

[0006] The trend in turbofan technology development has been to increase the bypass ratio in order to improve propulsion efficiency. However, in order to increase the bypass ratio, the TIT must be increased. Increasing the TIT causes many problems as mentioned above, and does not necessarily lead to environmental measures. In view of the above, Patent Document 1 has created an original technical idea that increases the work of the low-pressure turbine fan system within a realistic temperature range without increasing the TIT, increases the engine air flow rate, and maintains thrust.

[0007] However, in Patent Document 1, the low pressure turbine (LPT) expansion ratio exceeds the design point value at partial load, that is, the exhaust nozzle area at the design point (here, takeoff rating) is smaller than at partial load. Therefore, in order to obtain maximum thrust at takeoff rating, the exhaust nozzle of the core engine had to have a variable mechanism. The variable mechanism is complicated and increases weight. The objective of this invention is to realize a cycle that can maintain thrust even when the TIT is lowered by eliminating the variable mechanism and using a fixed nozzle. [Means for solving the problem]

[0008] In order to maintain thrust even when the TIT is lowered, it is necessary to increase the low pressure shaft speed without increasing the high pressure shaft speed and increase the engine flow rate. As a solution, it was discovered that the turbine expansion ratio increases when the core exhaust nozzle area is set large and the TIT is lowered. By using this phenomenon, it was found that it is possible to increase the low pressure shaft speed without excessively increasing the high pressure shaft speed while keeping the core exhaust nozzle fixed. This idea and the analysis by calculation will be described in detail in the examples.

[0009] In this invention, the exhaust nozzle is fixed by improving the matching technology such as the TIT reduction range, the fan speed increase range, and the setting of the choke points of the high-pressure turbine (HPT) and LPT so that the turbine expansion ratio at partial load does not exceed the choke value while keeping the exhaust nozzle fixed, thereby improving the weaknesses of Patent Document 1 and realizing a cycle that reduces fuel consumption per thrust.

[0010] The mechanism for realizing this cycle is as follows: 1) In this engine, compared to conventional turbofans with the same fan front area, the settings of how much to lower the TIT and how much to increase the fan speed are not determined only by the aerodynamic design point (takeoff rating), but are selected taking into consideration operation at partial load in the air. In other words, it is an essential condition that the engine can be operated with the exhaust nozzle fixed even at partial load. 2) The same applies to setting the choke points of the HPT and LPT; the expansion ratio of either turbine must not exceed the choke point at altitude. Effect of the Invention

[0011] 1) Fuel consumption per thrust can be reduced, i.e., SFC can be improved (see Table 1). 2) The amount of cooling air can be reduced because the TIT can be lowered without reducing thrust. The turbine life can be extended. Manufacturing costs can be reduced. 3) The exhaust nozzle of the core can be fixed to achieve the above 1) and 2) (a difference from Patent Document 1). [Brief description of the drawings]

[0012] [Figure 1] 1 is a conceptual diagram of a turbofan engine according to the present invention. [Diagram 2] This is the FAN operation map. [Diagram 3] This is the LPC operation map. [Figure 4] This is the HPC operation map. [Diagram 5] Turbine flow characteristic curve diagram. Example 1 is HPT, Example 2 is LPT (solid line is the present invention, dotted line is a conventional engine). [Figure 6] FIG. 4 is a diagram showing the difference in turbine expansion ratio between a conventional type and the present invention. [Figure 7] 1 is a turbine coupling characteristic curve diagram showing the aerodynamic connection between the HPT and LPT (Example 3 is a conventional type, Example 4 is an example of Patent Document 1, and Example 5 is an example of the present invention). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] A conceptual diagram of the turbofan engine of the present invention is shown in FIG. 1. In the figure, FAN is a fan, LPC is a low pressure compressor, HPC is a high pressure compressor, COMB is a combustor, HPT is a high pressure turbine, LPT is a low pressure turbine, and WN (Wide Nozzle) is the core exhaust nozzle (solid line) of the present invention, which has a larger exit area than the conventional nozzle NN (Normal Nozzle) shown by the dotted line. The difference from Patent Document 1 is that the core exhaust nozzle is fixed, and the aerodynamic design points and choke point setting methods and matching technologies to produce the above-mentioned effects are different. These are shown in examples based on maps. In the figure, the numbers represent the engine position numbers. The core exhaust nozzle controls the operating line of the HPC, and the expansion ratios of both the HPT and LPT must not exceed the choke value so that the operating conditions of the exhaust nozzle WN located downstream are transmitted to the HPC located upstream. From FIG. 1, the present invention appears to be no different in terms of mechanism from the conventional turbofan, but the technical idea of ​​the present invention to lower the TIT without reducing the thrust is completely different. Lowering the TIT always results in a decrease in thrust (output). This was the common knowledge with gas turbines.

[0014] In order to explain the cycle characteristics and effects of the turbofan of the present invention, which has a low TIT at takeoff rating, it is easy to understand how to show the difference by comparing the present invention with a conventional turbofan with the same engine front area. Therefore, in this operation explanation, the performance at takeoff rating of two engines with the same fan front area and the same geometric shapes of FAN, LPC, and HPC, that is, a normal conventional turbofan and the present invention, is calculated, and the difference in operation is compared.

[0015] Figures 2, 3, and 4 show the operation maps of the FAN, LPC, and HPC. These maps were created by reproducing the flow rate characteristics for the rotation speed from the map published in Non-Patent Document 1 using a parabolic approximation method for the flow rate, and plotting each calculated operating point on the operation line. Figure 5 is a diagram of the turbine flow rate characteristic curve using the formula 1 described later. Example 1 of Figure 5 is a characteristic curve diagram for the high-pressure turbine HPT, and Example 2 is a characteristic curve diagram for the low-pressure turbine LPT. In the figures, the solid line is the flow rate characteristic curve of the present invention, and the dotted line is the conventional type. The black dots at the ends of the characteristic curves are the turbine choke points. As is clear from the figures, the conventional type and this engine compared here have the same hardware for the FAN, LPC, and HPC, but the turbines are different hardware. In Patent Document 1, the LPT expansion ratio is larger than the choke point at partial load, but in the present invention, the LPT expansion ratio must not be larger than the choke point because the exhaust nozzle is fixed. Note that the Aerospace Engineering Research Institute Report No. 347 is written in the engineering unit system, and this specification follows that. EXAMPLES

[0016] First, the set values ​​of the basic engine specifications are shown, and the calculation method is explained. Also, the difference in operation between the present invention and the conventional type is shown based on the calculation. In Figures 2 to 4, point A is the aerodynamic design point (ADP; Aerodynamic Design Point) of the conventional engine and this engine, and the fan relative corrected rotation speed Nfc = 1. The operating point for the conventional takeoff rating is point A, and the TIT of the conventional type at point A is 1820K (1547℃), the fan flow rate is 9kg / s, the core flow rate is 1kg / s, and the BPR is 8. In this calculation, 1820K is set as the upper limit temperature of the TIT for small and medium-sized aircraft.

[0017] Point TS (top speed) is the operating point where the relative corrected fan speed is increased to Nfc = 1.03 on the same operating line as the conventional type, and is the operating point at the takeoff rating of this engine. The TIT at TS of this proposal is 1690K (1417℃), which is 130 degrees lower than the conventional type at point A. The thrust at point A of the conventional engine and the thrust at point TS of this engine are almost the same, as shown in Table 1. The nozzle area ratio in this calculation between the conventional type and this engine is approximately 1:1.235.

[0018] In this engine, the nozzle area A7 is set wider than in a normal conventional engine, so if the HPT and LPT are not choked, the resistance downstream of the HPC will decrease, and as shown in Figure 4, the HPC operating line will move to the choked side, increasing the flow rate at the operating point TS and lowering the pressure ratio HPR. Here, the HPT, LPT and nozzle are all choked. In other words, in examples 1 and 2 in Figure 5, which show the turbine flow characteristics, the choke point for the conventional engine is A, and the choke point for this engine is TS. The turbine nozzle area for both the HPT and LPT is set to the minimum area that allows the movement of the HPC operating line.

[0019] In contrast, in Patent Document 1, the aerodynamic design points of the FAN, LPC, and HPC are all TS, and the area of ​​the variable nozzle is enlarged to raise the relative corrected fan speed at TS to 1.05. This difference is due to the two new constraints: "fixing the exhaust nozzle (eliminating the variable mechanism)" and "preventing the LPT expansion ratio from becoming excessive at partial load."

[0020] Next, we will explain the calculation method for takeoff rating. If the fan relative corrected speed is increased from 1 to 1.03, the LPC is coaxial with the fan, so the mechanical speed is the same but the inlet temperature is higher than the fan, so the relative corrected speed will decrease to 97.8%. A constant speed curve of 97.8% is drawn on the LPC map, and the intersection of this curve and the operating line is the LPC operating point TS of this proposal. The relative corrected flow rate of 1.02 at the HPC inlet obtained from the LPC outlet conditions is shown by the vertical dotted line on the HPC map in Figure 4.

[0021] The intersection of this dotted line and the HPC operating line is the HPC operating point when the fan relative corrected speed is increased from Nfc = 1 to 1.03 for a conventional turbofan, at which the HPC pressure ratio becomes HPR = 8.94 and TIT = 1983.5 K, and the TIT exceeds the allowable temperature and exceeds the limit, making operation impossible.

[0022] In National Aerospace Laboratory Report No. 347 (Non-Patent Document 1), the turbine gas flow rate is approximated as a function of the expansion ratio by an elliptical formula in Equation 1. In Equation 1, i is the inlet and e is the outlet. If i=4 and e=5, the left side of Equation 1 represents the HPT inlet corrected flow rate. Next, Equation 2 shows the combustor outlet corrected flow rate with TIT set to 1690K.

[0023]

number

[0024]

number

[0025] Here, ε is the combustor total pressure loss coefficient. In order to avoid choking of the HPT in the initial stage of calculation, the corrected flow rate in equation 1 and the choke value of the expansion ratio are assumed to be large, and then calculations are carried out by changing HPR=P03 / P02 in the denominator of the second term on the right-hand side of equation 2 in various ways, and by matching the corrected flow rate at the combustor outlet on the left-hand side with the corrected flow rate at the HPT inlet on the left-hand side of equation 1, the value of HPR at point TS shown in Figure 4 can be found. This HPR value is the state in which the operating conditions of the exhaust nozzle are transmitted to the upstream HPC.

[0026] In other words, the throttle downstream of the HPC is opened to move the HPC operating line to the high flow rate side, and the intersection of that operating line and the HPC relative corrected flow rate (vertical dotted line) derived from the LPC outlet conditions becomes the HPR. Therefore, the core flow rate Ghc increases, and a matching point can be found where the HPC outlet pressure P03 does not increase excessively. If the choke values ​​of the corrected flow rate and expansion ratio in equation 1 are set to the calculated values ​​at the point when the left sides of equation 1 and equation 2 become equal, the HPT of this invention will choke at point TS in Example 1 of Figure 5.

[0027] Next, replace the engine position number in equation 1 with the LPT inlet and outlet position numbers 5 and 6, perform calculations, and match the HPT outlet corrected flow rate with the LPT inlet corrected flow rate to find out the characteristics of the LPT. Here too, the LPT inlet corrected flow rate and the choke value of the expansion ratio are set to values ​​that do not prevent the exhaust nozzle's operating conditions from being transmitted upstream, and after calculations the choke value is made to match the calculated value. In other words, the LPT is also choked at point TS. Therefore, the choke values ​​for both the HPT and LPT are the minimum area that allows the operation of the HPC mentioned above. The method for calculating the balance between flow rate and work is known, so it is omitted here.

[0028] Next, I will explain how the turbine expansion ratio shown in Figure 5 is obtained. In order to reduce the core exhaust jet velocity while maintaining the thrust, it is necessary to increase the engine flow rate. To increase the engine flow rate, the turbine expansion ratio should be increased to increase the work of the low pressure turbine fan system.

[0029] In the present invention, increased turbine expansion ratio is achieved in two ways. 1) The exhaust nozzle area of ​​the core engine is widened to reduce the engine back pressure. However, this alone does not provide a sufficient expansion ratio. 2) Another method is to reduce the turbine inlet temperature. Let me explain 1) and 2) in detail. If the exhaust nozzle area of ​​the core engine is set large, the LPT expansion ratio increases. Since the exhaust nozzle of the core engine is choked, the flow at the exit is calculated as follows from the flow function using static pressure:

[0030]

number

[0031] Here, the subscript 7 represents the nozzle outlet of the core engine. The right hand side of equation 3 is constant. If the nozzle area A7 is made wider at the design point, the nozzle flow rate m7 (G7 / g) will increase, but the core flow rate is restricted by the upstream LPC. Therefore, from equation 3, Sqrt(T07) / P7 also increases, but since T07=T06 and the total temperature T07 does not change in the nozzle, P7 becomes smaller and the engine exhaust pressure decreases. The nozzle inlet total pressure P06 (total pressure at the LPT outlet) is expressed by equation 4.

[0032]

number

[0033] Since the nozzle is choked, the right hand side of equation 4 is constant, so if P7 decreases, the nozzle inlet total pressure P06 (LPT outlet total pressure) also decreases. Since this cycle is rated for takeoff and the total pressure ratio on the compressor side hardly decreases, if P06 decreases, the LPT expansion ratio increases, the fan speed increases, and the engine flow rate Ga increases. Another powerful method for increasing the turbine expansion ratio is to lower the TIT. Turbine work W T is expressed by the number 5.

[0034]

number

[0035] Here, the subscript i is the inlet and e is the outlet. From equation 5, if the LPT inlet temperature T05 is lowered, the LPT work W T This is the common sense T05 and W T Here, when exhaust nozzle A7 is opened and P0e (P06) is lowered from equations 3 and 4, let us consider what difference will occur if the LPT inlet temperature T0i (T05) is lowered at the same time or not.

[0036] In equation 5, if the LPT inlet temperature T05 is high, the required turbine work W T To obtain this, the LPT expansion ratio does not need to be very large, and the A7 area only increases slightly. On the other hand, if the LPT inlet temperature T05 is lowered, the required W that meets the fan's requirements can be obtained from equation 5.T To obtain this ratio, a large P05 / P06 is required, and the area of ​​A7 becomes large. Therefore, if T05 is lowered, that is, TIT is lowered, and A7 is made wider at the same time, a phenomenon different from the common sense of turbine work mentioned earlier occurs, and a large turbine expansion ratio can be obtained.

[0037] Figure 6 shows the change in the expansion ratio of the HPT and LPT and the approach of the exhaust pressure P7 to atmospheric pressure when the core engine exhaust nozzle area A7 and TIT are changed. Here, axis A is a normal turbofan that is the basis for this cycle calculation, with relative corrected speed Nfc = 1 and TIT = 1820K, plan B is the plan where Nfc is increased from 1 to 1.03 and TIT is lowered to 1650K, and axis C is the plan where Nfc is increased to 1.04 and TIT is lowered to 1650K. The nozzle area ratios of B and C divided by the nozzle area of ​​conventional type A are 1.235 for B and 1.333 for C. Figure 6 shows that in order to increase the turbine expansion ratio without reducing thrust, it is necessary to both widen A7 and lower TIT.

[0038] This is the focus of this invention and its inventive step. Until now, no one had realized that lowering the TIT and widening the core exhaust nozzle area at the same time would produce a large LPT expansion ratio as shown in Figure 6. Furthermore, no one had ever thought of lowering the TIT while keeping the core engine exhaust nozzle area A7 constant, increasing the air flow rate per frontal area, and reducing fuel consumption per thrust. In other words, the technical concept of this proposal is not something that even an expert could easily come up with.

[0039] The difference between the conventional common sense approach to methods for improving engine performance and the approach (point of view) of this invention has created the inventive step of this invention. Performance indicators for gas turbines include specific power (specific impulse) and thermal efficiency. To increase specific impulse, the maximum temperature is raised, and to improve thermal efficiency, the pressure ratio is increased. However, in this invention, the TIT is lowered while keeping the pressure ratio roughly constant.

[0040] In addition, in turbofans, the BPR is increased to improve propulsive efficiency, but in the present invention, the BPR is actually lowered and there is no improvement in propulsive efficiency. So why can the fuel consumption per thrust be reduced? This is because when the TIT is lowered and the engine back pressure is lowered at the same time, the turbine expansion ratio becomes very large as shown in Figure 6, and the work of the low-pressure shaft system increases despite the lowering of the TIT, allowing the flow rate per frontal area to be increased.

[0041] In that case, it seems that the performance could be improved by increasing the fan speed to Nfc=1.03 by widening the exhaust nozzle area while keeping T04=1820K even for the conventional type, but with the TIT constant, the turbine expansion ratio becomes P04 / P06=6.734, which is smaller than the proposed P04 / P06=7.922, and a large expansion ratio cannot be obtained. Then, the ratio of the exhaust speed on the bypass side to the core exhaust speed becomes VF / VT=0.372, which is smaller than the proposed VF / VT=0.393. Therefore, the SFC becomes higher. The inventive step of this invention is that a new cycle was created by focusing on this point. From the matching calculations described above, this invention can increase the fan flow rate without increasing the fuel flow rate by widening the core exhaust nozzle and lowering the back pressure, and by lowering the TIT, the LPT expansion ratio can be further increased, and the flow rate per frontal area can be increased.

[0042] Next, the coupling characteristics of the HPT and LPT with such a large expansion ratio will be explained with reference to Figure 7. Example 3 of Figure 7 shows the coupling characteristics of a normal two-shaft in-line free turbine, Example 4 shows the coupling characteristics during cruising in Patent Document 1, and Example 5 shows the characteristics of the present application. In the conventional turbofan with a fixed core nozzle in Example 3 of Figure 7, the relationship between the two turbines is connected as shown by the solid line at the design point, but when the total expansion ratio decreases at partial load, it becomes like the dotted line, and the expansion ratio decrease is small in the HPT and large in the LPT. In other words, when the TIT is lowered, the ratio of the work of the HPT to the work of the LPT increases, and the output of the LPT decreases sharply (from Non-Patent Document 2, page 26).

[0043] Example 4 shows the turbine aerodynamic coupling characteristics at cruise (altitude 10 km, Mach = 0.9) of Patent Document 1, in which the core exhaust nozzle area is made variable and greatly expanded, and the TIT is lowered by 227 degrees from 2000K to 1773K at takeoff rating. As shown in the figure, in Patent Document 1, the LPT expansion ratio exceeds the choke value at partial load, and the fuel consumption at partial load is calculated to be very good. However, as is clear from the figure of Example 4, this cycle has a partial load LPT outlet corrected flow rate that is much larger than the takeoff rating. Therefore, if the core exhaust nozzle is a fixed nozzle, the takeoff rating thrust cannot be maximized. The present invention changes the cycle to fix the nozzle of Example 4 and improves feasibility, and as shown in Example 5, the coupling characteristics of the two turbines are determined and the cycle is designed so that the LPT expansion ratio does not exceed the design point value at partial load. The results of the takeoff rating cycle calculation are shown in Table 1.

[0044] In Table 1, Ga is the fan inlet air flow rate, Ghc is the HPC flow rate, Gf is the fuel flow rate, the total pressure ratio is the total pressure ratio, and Fn is the net thrust. A7 is the ratio of the core exhaust nozzle area divided by that of the conventional type. In Table 1, A is the conventional turbofan, B is the calculated value of the present invention with the fan relative corrected speed Nfc = 1.03 and TIT = 1690K, and C is the present invention with Nfc increased to 1.04 and TIT reduced to 1650K. Of the two present inventions, C has a lower SFC than B, but the limit is the increase in the LPT expansion ratio at altitude. From Table 1, the present invention has a lower fuel consumption per thrust (Gf / Fn) than the conventional type, but this effect is obtained by increasing the turbine expansion ratio by widening A7 and lowering TIT.

[0045] [Table 1]

[0046] [Industrial Applicability]

[0047] As an environmental measure, this invention reduces CO2 emissions by reducing SFC, and reduces NOx emissions by lowering the combustion gas temperature. Furthermore, as an economic improvement measure, it can lower the turbine inlet temperature without reducing thrust, extend the turbine lifespan, and reduce life cycle costs, achieving both environmental and economic benefits. In the future, it can also suppress the generation of NOx, a weakness of hydrogen combustion, and contribute to the realization of hydrogen-fueled turbofan engines. For turbofans, where high temperature and pressure have always been the ultimate goal, this cycle will bring about a new world of improved performance at low temperatures. [Explanation of symbols]

[0048] A Nfc=1 activation point or area ADP Aerodynamic design point BPR Bypass ratio COMB Combustor Cpt Turbine section constant pressure specific heat FAN fan f fuel air mixture ratio G Actual flow rate HPC High pressure compressor HPT High Pressure Turbine LPC Low Pressure Compressor LPT Low pressure turbine M Mach number N RPM Nfc Fan relative corrected RPM Nhc HPC relative corrected rotation number Nlc LPC relative corrected rotation number Sqrt() Square root TS Maximum speed range (top speed) (G√θi / δi) / (G√θi / δi)des Relative correction flow rate δ P / Ps ε Total pressure loss coefficient θ T / Ts numbers Atmosphere 1. Fan inlet 22. Fan outlet 2. LPC outlet 3. HPC outlet (combustor inlet) 4. Combustor outlet (HPT inlet) 5.LPT inlet 6.LPT outlet 7. Core nozzle outlet 8. Bypass nozzle outlet

Claims

[Claim 1] The following method of the present invention reduces the turbine inlet temperature (TIT) without reducing thrust. 1) The choke points of the high pressure turbine (HPT), low pressure turbine (LPT), and core exhaust nozzle (WN) are set to takeoff ratings; 2) The area of ​​the core engine exhaust nozzle is set larger than that of a conventional turbofan nozzle, 3) By reducing the engine back pressure using 2), the operating line of the high pressure compressor (HPC) is moved to the choke side to increase the core flow rate, and the fuel-air mixture ratio is reduced to reduce the TIT, preventing the HPC pressure ratio from increasing excessively. 4) A method of using 2) and 3) to create the phenomenon whereby lowering the TIT with a wide exhaust nozzle area results in an increased turbine expansion ratio. 5) A fixed cycle that uses method 4) to increase the low-pressure shaft rotation speed without over-rotating the high-pressure shaft, thereby reducing fuel consumption per thrust. 6) As a condition for establishing the cycle in 5), the maximum temperature, fan speed, and exhaust nozzle area are set to values ​​that allow operation with the exhaust nozzle fixed not only at takeoff rated speed but also at cruise speed, i.e., partial load, so that the turbine expansion ratio does not exceed the choke value during cruising. The cycle design and engine configuration are such that the maximum temperature, fan speed, and exhaust nozzle area are set to values ​​that allow operation with the exhaust nozzle fixed not only at takeoff rated speed but also at cruise speed, i.e., at partial load.

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