Task-Level Energy Efficiency Evaluation Method Based on Aero-Engine Thrust-Specific Fuel Consumption with Application to Environment Control System
Round 1
Reviewer 1 Report
The presented work must be supplemented with a review of the literature, the citation has been arranged, the analysis of the results has been performed, and the obtained conclusions have been made more concrete. I provide a detailed list of my comments.
Line 72. The literature review lacks examples of the analysis of the ECS system and the implementation of surrogate models that would allow to substantiate the relevance of the topic is also not described.
Line 79. There is no explanation for abbreviations that make reading difficult.
Line 81. If typical parameters are provided, it is necessary to indicate the literature source that will allow to assess the reliability of these data.
Line 95. At what temperature will the air density be taken? This value is highly temperature dependent, large fluctuations in values directly lead to large errors and the reliability of the results obtained.
Line 97. On what basis is such a fighter mass accepted? Do you value the weight of fuel and combat ammunition? Literature source?
Line 113. Is permission to publish Figure 3 from [24] obtained?
Line 114. Where did the Table 2 data come from? Literature sources?
Line 135. Is this version of the software licensed (Gasturb 10)?
Lines 144-153. The establishment of a fact, in addition to a broader analysis of the causal link, greatly diminishes the work of the authors, so it is necessary to supplement the analysis of the obtained results by indicating possible reasons or hypothesizing why this could have happened.
Line 157. The rectangles in Figure 4 are misleading, it seems that the authors do not want to show the dependence of the axes on each graph, but to define the area of the rectangle>
Line 179. Where did the Table 3 data come from? Literature sources?
Line 195. Same remark as Lines 144-153. The results in the graphs are not properly explained.
Line 219. Data are validated not by a field experiment but by the results of the Gasturb 10 software. Can this be called validation? What, then, is reliability?
Line 230. Figure 9 Gasturb is provided without 10. Is there a different version of Gasturb available here?
Line 240. Why take a temperature of -5 C? After all, according to the plan, different heights will be shaded, so the temperature will also differ.
Line 262. The members of formula 14 are not explained.
Line 296. And what if there is no validation but only a comparison of the results of the programs, it is not clear where and how much reliability data would be obtained.
Author Response
Response to Reviewer 1 Comments
Thanks very much for taking your time to review this manuscript. I really appreciate all your comments and suggestions! Please find my itemized responses in below and my revisions/corrections in the re-submitted files.
Point 1: Line 72. The literature review lacks examples of the analysis of the ECS system and the implementation of surrogate models that would allow to substantiate the relevance of the topic is also not described.
Response 1:
Thanks for your advice. We have added some literature on the analysis of the ECS system and the implementation of surrogate models that allow to substantiate in the Introduction.
After modification:
- E. Lents [8] defined normalized energy consumption rate and fuel mass consump-tion rate to evaluate the influence of system weight, drag, and power demand on aircraft energy consumption. The fuel consumption of the hybrid aircraft is evaluated and the re-sults show that 1.5% of total mission fuel burn for the thermal management system in a flight mission profile of 2 hours. R. Slingerland and S. Zandstra [16] evaluated the influ-ence of bleed air and electric power extraction on the performance of the aero-engines of a commercial passenger aircraft and compared the fuel penalty of electrically driven and bleed air driven air cycle ECS. Their result shows that 2% TSFC can be saved, by using electrically driven instead of bleed air driven for air cycle ECS.
The method of surrogate model provides a new way to simplify the aero-engine model. It is used to replace the original complex model or test process with a simplified model. Researchers have carried out research on surrogate model construction for aero-engine inlet, compressor, combustion chamber and other components, which greatly reduces the difficulty of aero-engine modeling and optimization [24-26]. Research on the surrogate model of aero-engine performance is also carried out. By analyzing the charac-teristics of turboshaft engine performance curves, Zhou and Qiu [27] used the least square method to obtain accurate engine performance curves and establish engine power surro-gate model. The test flight shows that the surrogate model can reflect the real performance of the engine.
[8] Lents, C. E., Impact of Weight, Drag and Power Demand on Aircraft Energy Consumption. In AIAA Propulsion and Energy 2021 Forum, American Institute of Aeronautics and Astronautics: 2021. DOI: 10.2514/6.2021-3322.
[16] Slingerland, R.; Zandstra, S. In Bleed Air versus Electric Power Off-takes from a Turbofan Gas Turbine over the Flight Cycle, 7th AIAA ATIO Conf, 2nd CEIAT Int'l Conf on Innov and Integr in Aero Sciences,17th LTA Systems Tech Conf; followed by 2nd TEOS Forum, Belfast, 2007-09-18; American Institute of Aeronautics and Astronautics: Belfast, 2007. DOI: 10.2514/6.2007-7848.
[24] Mack, Y.; Goel, T.; Shyy, W.; Haftka, R., Surrogate model-based optimization framework: a case study in aerospace design. In Evolutionary computation in dynamic and uncertain environments, Springer: 2007; pp 323-342.
[25] Liu, W.; Sivaramakrishnan, R.; Davis, M. J.; Som, S.; Longman, D.; Lu, T., Development of a reduced biodiesel surrogate model for compression ignition engine modeling. Proceedings of the Combustion Institute 2013, 34 (1), 401-409. DOI: https://doi.org/10.1016/j.proci.2012.05.090.
[26] Drężek, P. S.; Kubacki, S.; Żółtak, J., Multi-objective surrogate model-based optimization of a small aircraft engine air-intake duct. Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 2022, 09544100211070868.
[27] Zhou, L.; Qiu, L., A New Method to Deal with Engine Test Data and to Build Agent Model of Engine. HELICOPTER TECHNIQUE 2019, (4), 32-35.
Point 2: Line 79. There is no explanation for abbreviations that make reading difficult.
Response 2:
The explanation for abbreviations has been supplemented in the appropriate place and all of the abbreviations are included in the Nomenclature table section.
After modification:
Figure 1. Flight mission profile of a fighter jet[18].
Point 3: Line 81. If typical parameters are provided, it is necessary to indicate the literature source that will allow to assess the reliability of these data.
Response 3:
We have added a reference for these datas. The fighter jet’s typical flight mission profile evolved from the same things in the reference [17] (Roberts, R.; Eastbourn, S., Vehicle level tip-to-tail modeling of an aircraft. International Journal of Thermodynamics 2014, 17 (2), 107-115. DOI: 10.5541/ijot.523.) .
After modification:
This paper takes F22 Raptor fighter jet as the research object, and the fighter jet’s flight mission profile is shown in Figure 1 and Table 1, including climb, cruise, ground attack, descent, and land.
Point 4: Line 95. At what temperature will the air density be taken? This value is highly temperature dependent, large fluctuations in values directly lead to large errors and the reliability of the results obtained.
Response 4:
We add a qualifiers about the air density. In this study, the temperature of the ambient air depends on the flight altitude of the aircraft. The temperatures at different flight altitudes are obtained by querying international standard atmospheric parameters, so the results have high reliability.
After modification:
ratm is the ambient air density at the flight altitude, kg/m3;
Point 5: Line 97. On what basis is such a fighter mass accepted? Do you value the weight of fuel and combat ammunition? Literature source?
Response 5:
We have provided the following supplementary notes. In this study, the research object is the American F22 Raptor fighter as the prototype, and it is 19700kg empty weight, 8200kg maximum fuel capacity and 38,000kg maximum take-off weight. Therefore, as a simple estimate, it is feasible to assume the total weight of the aircraft is 30,000kg. The datas are from reference [29].
After modification:
The F22 Raptor fighter jet is 19700kg empty weight, 8200kg maximum fuel capacity and 38000kg maximum take-off weight. In order to simplify calculation, the mass of the fighter jet is assumed to be 30000 kg [29].
[29] Riccardo, L. LOCKHEED MARTIN F/A-22 RAPTOR; Istituto Tecnico Industriale: 2012.
Point 6: Line 113. Is permission to publish Figure 3 from [24] obtained?
Response 6:
Thank you for reminding us of this question. The original drawing came from Gasturb 12. In order to avoid all possible copyright disputes, we replaced Figure 3.
Figure 3. Schematic diagram of two spool mixed flow turbofan engine.
Point 7: Line 114. Where did the Table 2 data come from? Literature sources?
Response 7:
The design point data of the F119-PW-100 engine in Table 2 comes from the reference [31], and the parameter matching results are calculated by Gasturb 12.
[31] Chen, J., Development trend of military aero engine. Aeronautical Science and Technology 1994, (5), 9-12. DOI: CNKI:SUN:HKKX.0.1994-05-002.
Point 8: Line 135. Is this version of the software licensed (Gasturb 10)?
Response 8:
After confirmation, the license of Gasturb 10 used in our calculation has expired, but our university has re-purchased the license of Gasturb 12. The data of this manuscript was recalculated using Gasturb 12 and updated.
Point 9: Lines 144-153. The establishment of a fact, in addition to a broader analysis of the causal link, greatly diminishes the work of the authors, so it is necessary to supplement the analysis of the obtained results by indicating possible reasons or hypothesizing why this could have happened.
Response 9:
The necessary analysis of the results has been supplemented in the revised manuscript. Figure 4 shows the curves of engine thrust and TSFC when 0-500kW exergy is extracted. As can be seen from the figure, there is an obvious linear relationship between thrust, TSFC and exergy extraction within the research range, so we use the linear relationship to represent their correlation.
After modification:
Figure 4 shows the change of thrust and TSFC due to exergy extraction with different control mode. For the TSFC, we can see that the correlation between TSFC and exergy ex-traction is linear no matter what exergy extraction methods are selected. Therefore, the TSFC can be expressed as Eq(10). Besides, the TSFC increases about 52.94% per 100kW for bleed air compared with electrical power extraction under constant engine speed control mode. Similarly, the TSFC increases about 55.56% per 100kW for bleed air compared with electrical power extraction under constant turbine front temperature control mode. This is because that bleed air results in less burner efficiency due to the reduced fuel-air ratio in the burner when extracting the same amount of exergy. The thrust change is similar to that of TSFC.
Point 10: Line 157. The rectangles in Figure 4 are misleading, it seems that the authors do not want to show the dependence of the axes on each graph, but to define the area of the rectangle
Response 10:
We remove the rectangle in Figure 4. At the same time, the two Y-axes adopt different colors, and the data curves are distinguished by linetype, color and symbol. The black lines suggest this is a thrust changes while the red dashed lines mean this is a TSFC changes.
After modification:
Figure 4. Influence of exergy extraction on engine performance parameters (EP-Electric power extraction; BL–Bleed air; CS-constant engine speed; CT-constant turbine front temperature).
Point 11: Line 179. Where did the Table 3 data come from? Literature sources?
Response 11:
The datas in Table 3 are determined by the H, Ma and FN range in the flight mission profile and thrust profile shown in Figure. 1 and Figure. 2. The manuscript also made a corresponding supplement.
After modification:
Based on the H, Ma and FN range in the flight mission profile and thrust profile shown in Figure. 1 and Figure. 2, the sample levels of each factor are shown in Table 3.
Point 12: Line 195. Same remark as Lines 144-153. The results in the graphs are not properly explained.
Response 12:
Thanks for your advice. According to Figure 5-7, the result analysis is supplemented.
After modification:
It can be seen from Figure 5 and Figure 6 that the slope of the fitted line is negatively correlated with FN, that is, the smaller the FN, the greater the slope of the fitted line. It also shows that when FN is small, the influence of bleed air and electric power extraction on TSFC is more significant. However, the slope of the fitting line changes relatively little with the parameters of flight conditions.
The Figure 7 shows the intercept of the fitting line varies with flight conditions. The intercept of the fitting line increases with the increase of Ma and decreases with FN. This is because the increase of Ma will bring to larger flight drag, it needs more fuel flow to pro-duce more thrust to maintain a stable flight, which leads to a larger TSFC. When FN is small, the intercept gradually decreases with the increase of H; when FN is large, the inter-cept gradually increases with the increase of H. Under the same flight condition, the inter-cept of the fitted line decreases rapidly and then increases slowly with the increase of FN. The inflection point roughly appears between 30kN and 50kN. At the left of the inflection point, the intercept decreases rapidly; to the right of the inflection point, the intercept slow-ly increases.
Point 13: Line 219. Data are validated not by a field experiment but by the results of the Gasturb 10 software. Can this be called validation? What, then, is reliability?
Response 13:
The comparison data is very important to verify our work. Unfortunately, there are few opening experimental data for the similar structure of aircraft engine, and the cost of the engine performance experiment is beyond our affordability.
However, the main innovation of this paper is to put forward a simplified calculation method of engine performance. This method is based on the change characteristics of engine performance parameters with energy extraction. Gasturb 12 is a professional software for gas turbine performance calculations based on the thermodynamic process of the engine. It has highly accurate in engine performance simulation and is broadly recognized in the industry and scientific research. The change characteristics of engine performance parameters with energy extraction reflected by Gasturb 12 calculation results are worthy of belief. Therefore, although the model has not been verified by experimental data, the simplified calculation method of engine performance is still feasible.
Point 14: Line 230. Figure 9 Gasturb is provided without 10. Is there a different version of Gasturb available here?
Response 14:
It also uses Gasturb 12 and we have added the version of Gasturb 12.
Point 15: Line 240. Why take a temperature of -5 C? After all, according to the plan, different heights will be shaded, so the temperature will also differ.
Response 15:
-5℃ is the design temperature of the outlet of the air cycle refrigeration system. The main purpose of this section is to show how the TSFC model can be applied to energy efficiency assessment. So, as a simple estimate, it is feasible to use the design value of the outlet temperature of the air cycle refrigeration system as the cabin air supply temperature.
Point 16: Line 262. The members of formula 14 are not explained.
Response 16:
We have added the explanation of Eq 14 in the appropriate place.
After modification:
Table 4 shows the total fuel consumption M of the flight mission profile, which is calculated by Eq:
Where, ts is the start of mission time, s; te is the end of mission time, s; e(t) and FN(t) are the TSFC and thrust at time t, respectively.
Point 17: Line 296. And what if there is no validation but only a comparison of the results of the programs, it is not clear where and how much reliability data would be obtained.
Response 17:
The same response as Point 13. The comparison data is very important to verify our work. Unfortunately, there are few opening experimental data for the similar structure of aircraft engine, and the cost of the engine performance experiment is beyond our affordability.
However, the main innovation of this paper is to put forward a simplified calculation method of engine performance. This method is based on the change characteristics of engine performance parameters with energy extraction. Gasturb 12 is a professional software for gas turbine performance calculations based on the thermodynamic process of the engine. It has highly accurate in engine performance simulation and is broadly recognized in the industry and scientific research. The change characteristics of engine performance parameters with energy extraction reflected by Gasturb 12 calculation results are worthy of belief. Therefore, although the model has not been verified by experimental data, the simplified calculation method of engine performance is still feasible.
Thank you very much for your attention and time.
Yours sincerely,
Liu Haodong
Author Response File: 
Author Response.pdf
Reviewer 2 Report
See attached.
Comments for author File: Comments.pdf
Author Response
Thanks very much for taking your time to review this manuscript. I really appreciate all your comments and suggestions! Please find my itemized responses in below and my revisions/corrections in the re-submitted files.
Point 1: General Comment: Grammar needs to be improved by someone who has a good grasp of writing and understanding English.
Response 1:
Thanks very much for your comments. We have asked Dr. Zhou Yuanye, who has overseas study experience and a well established expert, to polish our paper. Please see if the revised version met the English presentation standard.
Point 2: Abstract: It is important that the authors indicate explicitly in the abstract that the work is related to military engines and a military sortie profile.
Response 2:
This is a very good suggestion that we have made these clear in the abstract.
After modification:
This paper takes the F22 Raptor fighter jet as the research object, and analyzes the influence of bleed air and electric power on the thrust and thrust specific fuel consumption (TSFC) based on the exergy analysis method.
Point 3: All references to ‘fighter’ should be changed to ‘fighter jet’
Response 3:
We have replaced ‘fighter’ with ‘fighter jet’.
Point 4: All abbreviations need to be defined in the abstract as well as the main body when first used.
Response 4:
We have reviewed the entire manuscripts to ensure that each abbreviation is defined when it first appeared no matter the main body or abstract.
Point 5: All abbreviations need to be included in the Nomenclature table section.
Response 5:
We have reviewed the entire manuscripts to ensure that each abbreviation is included in the Nomenclature table section.
Point 6: The slope and intercept as variables to define a surrogate model is not well defined. These have been non-dimensionalised but without actual mathematical definitions for the reader to follow. These need to be improved.
Response 6:
In order to more easily to understand for the readers, we define a dimension for the slope and intercept.
After modification:
In this study, k is the slope of the linear relationship between TSFC and the exergy extraction, g/(kN·W·s). is the intercept of the linear relationship between TSFC and the exergy extraction, which also means the TSFC under the given flight conditions without exergy extraction, g/(kN·s).
Point 7: The computational time and latency are reasons to develop surrogate model to reduce the lengthy requirements, whilst still having good agreement in terms of accuracy. However, Gasturb as a means for validation is not convincing due to the novelty of determining the effects/penalties of bleed air and electric power combined. Such an approach is not based on a known methodology, rather it is based on individually developed approaches, underpinned by the thermodynamic conditions. A truly successful validation of the surrogate model needs to combine several known published studies that use a comprehensive thermodynamic process developed or facilitated by an application like Gasturb to compare the results of the surrogate model at numerous conditions. If a thermodynamic process or Gasturb is used, then the authors need to define the process in this manuscript. Either this approach is adopted OR the results from the surrogate models are compared with results from actual engine test or engine running data. Without this the its is difficult to justify the surrogate model has actually undergone validation.
Response 7:
The comparison data is very important to verify our work. Unfortunately, there are few opening experimental data for the similar structure of aircraft engine, and the cost of the engine performance experiment is beyond our affordability.
However, the main innovation of this paper is to put forward a simplified calculation method of engine performance. This method is based on the change characteristics of engine performance parameters with energy extraction. Gasturb 12 is a professional software for gas turbine performance calculations based on the thermodynamic process of the engine. It has a highly accurate in engine performance simulation and broad recognized in the industry and scientific research. The change characteristics of engine performance parameters with energy extraction reflected by Gasturb 12 calculation results is worthy of belief. Therefore, although the model has not been verified by experimental data, the simplified calculation method of engine performance is still feasible.
Point 8: The design/schematic of the refrigeration cycle needs to be shown and the parameters for that unique aircraft platform defined. The refrigeration cycle efficiency will be down to the type of refrigerants considered, the effectiveness of the heat exchange and the pipe/system losses. This adds a significant system variable to the overall efficiency, TSFC and demand.
Response 8:
We have added the schematic of the refrigeration cycle (Figure 10 air cycle; Figure 11 vapor cycle).
After modification:
A generic air cycle refrigeration system is shown schematically with its pres-sure-enthalpy diagram in Figure. 10. From stations 0 to 8, we see that bleed air, which comes from engine, is cooled down in the primary heat exchanger, after that it is sucked into the compressor. Then it is compressed to a higher pressure and temperature and cooled down again in the secondary heat exchanger. Subsequently, the air is expanded in a turbine, which results in a low temperature. Next, the air enters the mixing chamber and mixes with the air coming from station 7 to obtain the required cabin temperature and pressure, while doing useful work.
The bleed air mass flow qm required by the air cycle can be determined by the heat load and the temperature difference between the supply and exhaust air:
(12)
Where, Q is the heat load of the electronic equipment, W; Tc is the air temperature of the cabin, which is 20°C; Tacs is the temperature of supply air, which is generally -5°C.
(a) Schematic diagram (b) Pressure-enthalpy diagram
Figure. 10 Schematic diagram and pressure-enthalpy diagram of air cycle refrigeration system
Figure. 11 shows the schematic diagram and pressure-enthalpy diagram of the vapor cycle refrigeration system. In the vapor cycle, the refrigerant enters the electric compressor at a slightly superheated vapor state and is compressed to a higher pressure. The temperature of the refrigerant also increases after the compression step. Then, the refrigerant enters the condenser and is condensed into a saturated liquid state. Next, the refrigerant passes through the expansion valve where it undergoes an abrupt reduction in pressure. That pressure reduction results in a lower boiling point of the liquid refrigerant. Following, the liquid refrigerant absorbs thermal load in the evaporator and turns into a slightly superheated vapor state [34].
In this study, R134a is considered as refrigerant. The pressure of the refrigerant when it enters the compressor is referred to as the evaporate temperature and the pressure of the refrigerant when it leaves the compressor is referred to the condense temperature. As the refrigerant is generally condensed by fuel in the aircraft ECS, the condense temperature is set to be 50℃. The evaporate temperature is set to be -5℃ and 5℃ superheat of compressor suction is considered. The isentropic efficiency of the compressor is 0.75 and the equivalent efficiency of aircraft power generation and transmission is 0.8.
(a) Schematic diagram (b) Pressure-enthalpy diagram
Figure. 11 Schematic diagram and pressure-enthalpy diagram of vapor cycle refrigeration system
The electric power W consumed by the vapor cycle can be calculated according to the refrigeration coefficient COP:
Where, the COP of the vapor cycle can generally be taken as 2.5, and h is the equivalent efficiency of aircraft power generation and transmission.
Point 9: Lines 20-21 It is unclear to me how the engineering needs provided by the bleed air and electric power can met by the error value of the TSFC surrogate model. The authors should change this sentence to avoid confusion.
Response 9:
Thanks very much for your suggestion. We have substitute the confusing sentence for “The error of the TSFC surrogate model is less than 5%, which means the accuracy is sufficient to meet the needs of engineering.”.
Point 10: Line 70-71 The authors should explicitly state why a 2-step TSFC surrogate model is proposed. Why is it dependent on vibration characteristics and what specific vibration characteristics are the authors referring to?
Response 10:
It is a misuse of word ‘vibration’. In fact, what we want to express is to propose a two-step TSFC surrogate model according to the change law of TSFC with bleed air and electric power extraction.
After modification:
In this study, an exergy analysis method is used to compare the effects of bleed air and electric power extraction on thrust and TSFC under different flight conditions of the aeroengine. The results show that there is a linear relationship between TSFC and exergy extraction in a certain range. According to the linear relationship, a two-step TSFC surrogate model is proposed to simplify the calculation of aeroengine performance parameters. When the flight mission profile and thrust profile of the aircraft are known, the slope and intercept of the linear relationship at any given moment can be obtained using this surrogate model, so that the TSFC of the aeroengine can be quickly obtained by knowing only the bleed air and electrical power extractions during flight.
Point 11: Figures 1 & 2 Captions should remove the word ‘typical’. The profile and thrusts ratings are what are considered for this study and will be related to a specific sortie.
Response 11:
Thanks for your kindly advice, and we have removed the word ‘typical’.
Point 12: Lines 103-105 Gasturb 10 manual should be referenced.
Response 12:
Thanks for your advice. Since the license of Gasturb 10 used in our calculation has expired, our university has repurchased the license of Gasturb 12. The data of this manuscript was recalculated using Gasturb 12 and updated. Therefore, the Gasturb 12 manual has been referenced.
After modification:
Gasturb 12 is a gas turbine performance calculation and optimization program which has a complete engine type library and reliable calculation accuracy, so it is used worldwide in several industries as well as in science and education [30].
[30] Kurzke, J., GasTurb 12-Design and Off-Design Performance of Gas Turbines-Manual. 2014.
Point 13: Lines 108 Are the ‘full’ thrust requirements with afterburner being considered? It would appear not for Design Point purposes, but this is required at points in the sortie where afterburners will be used to understand the complete merit of the tasklevel energy efficiency evaluation method, more specifically for the thermal management.
Response 13:
Owing to afterburner occurs at supersonic cruise, aerodynamic performance can change dramatically due to the sonic boom in this station. The current study does not involve the afterburn state, which will be considered in future in-depth exploration.
Point 14: Table 2 does not provide the results in terms of error% of the matching. For known design point operating parameters, I would expect the error of actual vs. simulated to be declared.
Response 14:
The comparison data is very important to verify our work. Unfortunately, there are few opening experimental data for the similar structure of aircraft engine, and the cost of the engine performance experiment is beyond our affordability.
However, the main innovation of this paper is to put forward a simplified calculation method of engine performance. This method is based on the change characteristics of engine performance parameters with energy extraction. Gasturb 12 is a professional software for gas turbine performance calculations based on the thermodynamic process of the engine. It has highly accurate in engine performance simulation and is broadly recognized in the industry and scientific research. The change characteristics of engine performance parameters with energy extraction reflected by Gasturb 12 calculation results are worthy of belief. Therefore, although the model has not been verified by experimental data, the simplified calculation method of engine performance is still feasible.
Point 15: Line 131 Cp hot will be different to Cp Cold (or ambient temperature.
Response 15:
In fact, we determine CP based on air temperature and pressure, so CP is not a constant value. Here is the negligence in collating the manuscript. We have compared the air physical property parameters in the manuscript with Refprop, the physical property calculation software of the American Institute of Standard Technology, and the results are always.
Point 16: 145-148 There are no actual comparisons being made based on the statement. Do the authors mean that the TSFC is increase by 53 and 56% more, when compared to electrical power extraction?
Response 16:
We compare the increment of TSFC with different methods of exergy extraction and different control mode.
Point 17: Figure 4 CS and CT???
Response 17:
CS is the abbreviation of constant engine speed; CT is the abbreviation of constant turbine front temperature. We have added an annotation in the caption.
After modification:
Figure 4. Influence of exergy extraction on engine performance parameters (EP-Electric power extraction; BL–Bleed air; CS-constant engine speed; CT-constant turbine front temperature).
Point 18: Figures 5 and 6 need to be bigger.
Response 18:
Figures 5 and 6 have enlarged in the revised manuscript.
Point 19: Line 247 These are the power requirements, not the thermal load (Q).
Response 19:
In this section, the Q is the heat load of the electronic equipment. According to the reference [13], the thermal load of the fighter jet can reach 60kW. Since the power of the electronic equipment wouldn’t convert to thermal load, the thermal load is more suitable.
[13] Shou, R.; He, H., Aircraft environmental control. Beijing University of Aeronautics and Astronautics Press: Beijing, 2003.
Point 20: Figure 10 Difficult to tell apart the plot lines for some of the EP and BL plots. Perhaps a table with TSFCs for each individual condition, at the flight/sorties stages, will be better to compliment Figure 10. Furthermore, Figure 10 should be annotated with the various sortie stages.
Response 20:
Your suggestions are very useful for us to improve the paper. We use solid lines for EP and dashed lines for BL, different dot shapes to distinguish different extracted energy required, and increased the height of the figure to make it easier to readers to tell the TSFC for each individual condition and the figure has been annotated with the various sortie stages.
Figure 12. TSFC for each phase of the flight mission (EP-electric power extraction; BL-bleed air).
Point 21: Line 265 – “According to Table”….What table???
Response 21:
It is “According to Table 5”, and we have supplement it.
Thank you very much for your attention and time.
Yours sincerely,
Liu Haodong
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Dear Authors, the revised version of the article covers all my doubts and the qualitty of the paper increases.
