| 1. |
- Thulin, Oskar, 1987, et al.
(författare)
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First and Second Law Analysis of Radical Intercooling Concepts
- 2018
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Ingår i: Journal of Engineering for Gas Turbines and Power. - : ASME International. - 1528-8919 .- 0742-4795. ; 140:8, s. 081201-081201-10
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Tidskriftsartikel (refereegranskat)abstract
- An exergy framework was developed taking into consideration a detailed analysis of the heat exchanger (HEX) (intercooler (IC)) component irreversibilities. Moreover, it was further extended to include an adequate formulation for closed systems, e.g., a secondary cycle (SC), moving with the aircraft. Afterward, the proposed framework was employed to study two radical intercooling concepts. The first proposed concept uses already available wetted surfaces, i.e., nacelle surfaces, to reject the core heat and contributes to an overall drag reduction. The second concept uses the rejected core heat to power a secondary organic Rankine cycle and produces useful power to the aircraft-engine system. Both radical concepts are integrated into a high bypass ratio (BPR) turbofan engine, with technology levels assumed to be available by year 2025. A reference intercooled cycle incorporating a HEX in the bypass (BP) duct is established for comparison. Results indicate that the radical intercooling concepts studied in this paper show similar performance levels to the reference cycle. This is mainly due to higher irreversibility rates created during the heat exchange process. A detailed assessment of the irreversibility contributors, including the considered HEXs and SC, is made. A striking strength of the present analysis is the assessment of the component-level irreversibility rate and its contribution to the overall aero-engine losses.
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| 2. |
- Thoma, Evangelia Maria, 1996, et al.
(författare)
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Quantifying the Environmental Design Trades for a State-of-the-Art Turbofan Engine
- 2020
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Ingår i: Aerospace. - : MDPI AG. - 2226-4310. ; 7:10, s. 1-16
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Tidskriftsartikel (refereegranskat)abstract
- Aircraft and engine technology have continuously evolved since their introduction and significant improvement has been made in fuel efficiency, emissions, and noise reduction. One of the major issues that the aviation industry is facing today is pollution around the airports, which has an effect both on human health and on the climate. Although noise emissions do not have a direct impact on climate, variations in departure and arrival procedures influence both CO2 and non-CO2 emissions. In addition, design choices made to curb noise might increase CO2 and vice versa. Thus, multidisciplinary modeling is required for the assessment of these interdependencies for new aircraft and flight procedures. A particular aspect that has received little attention is the quantification of the extent to which early design choices influence the trades of CO2, NOx, and noise. In this study, a single aisle thrust class turbofan engine is optimized for minimum installed SFC (Specific Fuel Consumption). The installed SFC metric includes the effect of engine nacelle drag and engine weight. Close to optimal cycles are then studied to establish how variation in engine cycle parameters trade with noise certification and LTO (Landing and Take-Off) emissions. It is demonstrated that around the optimum a relatively large variation in cycle parameters is allowed with only a modest effect on the installed SFC metric. This freedom in choosing cycle parameters allows the designer to trade noise and emissions. Around the optimal point of a state-of-the-art single aisle thrust class propulsion system, a 1.7 dB reduction in cumulative noise and a 12% reduction in EINOx could be accomplished with a 0.5% penalty in installed SFC.
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| 3. |
- Sielemann, M., et al.
(författare)
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Multi-point design of parallel hybrid aero engines
- 2020
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Ingår i: AIAA Propulsion and Energy 2020 Forum. - Västerås : Institute of Electrical and Electronics Engineers Inc.. - 9781624106026 ; , s. 1-18
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Konferensbidrag (refereegranskat)abstract
- A parallel hybrid configuration is a feasible means to reduce fuel consumption of gas turbines propelling aircraft. It introduces an electric drive on one of the spools of the gas turbine, typically the low pressure spool. The electric drive is supplied by a battery, which can also be charged when excess power is available (for instance during conditions requiring handling bleed in conventional designs). It also requires a thermal management system to dissipate heat away from electric components. While the scientific literature describes parallel hybrid studies and anticipated benefits assuming various future entry into service dates, there is limited information on the design of the gas turbine component of such a system. For conventional gas turbines, multi-point design schemes are used. This paper describes, in a consistent fashion and based on a formalized notation, how such multi-point design schemes are applied to parallel hybrid aero engines. It interprets published approaches, fills gaps in methodology descriptions with meaningful assumptions and summarizes design intent. It also discusses cycle designs generated by different methodologies based on the same cycle model. Results show that closure equations prescribing boost power can be preferable over closure equations prescribing temperature ratios for uniqueness and engineering intuitiveness while the latter can be beneficial in a second step for design space exploration.
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| 4. |
- Zhao, Xin, 1986, et al.
(författare)
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Conceptual design of a two-pass cross-flow aeroengine intercooler
- 2015
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Ingår i: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering. - : SAGE Publications. - 2041-3025 .- 0954-4100. ; 229:11, s. 2006-2023
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Tidskriftsartikel (refereegranskat)abstract
- Establishing an optimal intercooled aeroengine constitutes a coupled problem where the conceptual design of the intercooler and the engine has to be considered simultaneously. The heat transfer and pressure loss characteristics will depend on the choice of the intercooler architecture. Hence, to be able to optimize the performance of an intercooled aeroengine, the performance characteristics of a given intercooler architecture has to be known in the parameter range anticipated for the aeroengine optimization. Here, the conceptual design of a tubular two-pass cross-flow intercooler architecture intended for a turbofan aeroengine application is presented. The internal flow is simulated applying a porous media model for the intercooler tubes, whereas the connecting ducts are analyzed with three-dimensional simulations allowing the assessment of a number of design solutions. The external flow is treated with two-dimensional simulations investigating the external pressure loss and heat transfer characteristics of the two elliptical tube stacks. The intercooler performance is then generalized by developing a reduced order correlation covering a parameter range anticipated for a turbofan conceptual design optimization. The paper constitutes a first effort to establish an open literature complete set of correlations for the prediction of aeroengine intercooler performance.
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| 5. |
- Zhao, Xin, 1986, et al.
(författare)
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Experimental Validation of the Aerodynamic Characteristics of an Aero-engine Intercooler
- 2017
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Ingår i: Journal of Engineering for Gas Turbines and Power. - : ASME International. - 1528-8919 .- 0742-4795. ; 139:5
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Tidskriftsartikel (refereegranskat)abstract
- Porous media model computational fluid dynamics (CFD) is a valuable approach allowing an entire heat exchanger system, including the interactions with its associated installation ducts, to be studied at an affordable computational effort. Previous work of this kind has concentrated on developing the heat transfer and pressure loss characteristics of the porous medium model. Experimental validation has mainly been based on the measurements at the far field from the porous media exit. Detailed near field data are rare. In this paper, the fluid dynamics characteristics of a tubular heat exchanger concept developed for aero-engine intercooling by the authors are presented. Based on a rapid prototype manufactured design, the detailed flow field in the intercooler system is recorded by particle image velocimetry (PIV) and pressure measurements. First, the computational capability of the porous media to predict the flow distribution within the tubular heat transfer units was confirmed. Second, the measurements confirm that the flow topology within the associated ducts can be described well by porous media CFD modeling. More importantly, the aerodynamic characteristics of a number of critical intercooler design choices have been confirmed, namely, an attached flow in the high velocity regions of the in-flow, particularly in the critical region close to the intersection and the in-flow guide vane, a well-distributed flow in the two tube stacks, and an attached flow in the cross-over duct.
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| 6. |
- Grönstedt, Tomas, 1970, et al.
(författare)
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Multidisciplinary assessment of a year 2035 turbofan propulsion system
- 2022
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Ingår i: 33rd Congress of the International Council of the Aeronautical Sciences, ICAS 2022. - : International Council of the Aeronautical Sciences. - 9781713871163 ; 7, s. 4981-4990
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Konferensbidrag (refereegranskat)abstract
- A conceptual design of a year 2035 turbofan is developed and integrated onto a year 2035 aircraft model. The mission performance is evaluated for CO2, noise and NOx and is compared with a notional XWB/A350-model. An OGV heat exchanger is then studied rejecting heat from an electric generator, and its top-level performance is evaluated. The fan, the booster and the low-pressure turbine of the propulsion system are subject to more detailed aero design based on using commercial design tools and CFD-optimization. Booster aerodynamic modelling output is introduced back into the performance model to study the integrated performance of the component. The top-level performance aircraft improvements are compared to top-level-trends and ICAO estimates of technology progress potential, attempting to evaluate whether there is some additional margin for efficiency improvement beyond the ICAO technology predictions for the same time frame.
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| 7. |
- Zhao, Xin, 1986, et al.
(författare)
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Development of an aerodynamic analysis tool for boundary layer ingestion concept design
- 2022
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Ingår i: 33rd Congress of the International Council of the Aeronautical Sciences, ICAS 2022. ; 2, s. 974-985
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Konferensbidrag (refereegranskat)abstract
- The methods incorporated in an aerodynamic analysis tool are introduced to support aircraft conceptual designs, where a boundary layer ingestion (BLI) propulsion system is deployed. In order to integrate the BLI model to a generic tool for aircraft designs, two methods of approximating boundary layer profiles along the airframe/fuselage have been examined. For an airfoil-shaped wing/body configuration, the airfoil analysis program XFOIL is used and, alternatively, the flat plate boundary layer theory may be adopted. With the boundary layer characteristics approximated from these methods, the fan performance in terms of pressure ratio and efficiency is corrected considering the inflow distortion incurred by the boundary layer ingested, based on a simplified parallel compressor method. Given the corrected fan pressure ratio and efficiency, an equivalent velocity bookkeeping method is used for predicting the BLI fan performance in terms of power requirement and thrust generation. A validation against the boundary layer approximation is also presented in comparison with the RANS-based CFD simulations for a blended wing body (BWB) aircraft.
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| 8. |
- Hecken, Tobias, et al.
(författare)
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Conceptual Design Studies of “Boosted Turbofan” Configuration for short range
- 2020
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Ingår i: AIAA 2020-0506 Session: Hybrid Electric Aircraft Design Under Clean Sky 2 (LPA WP1.6.1.4). - Reston, Virginia : American Institute of Aeronautics and Astronautics.
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Konferensbidrag (refereegranskat)abstract
- This paper describes the current activities at the German Aerospace Center (DLR) and an associated consortium related to conceptual design studies of an aircraft configuration with hybrid electric propulsion for a typical short range commercial transport mission. The work is implemented in the scope of the European Clean Sky 2 program in the project “Advanced Engine and Aircraft Configurations” (ADEC) and “Turbo electric Aircraft Design Environment” (TRADE). The configuration analyzed incorporates parallel hybrid architecture consisting of gas turbines, electric machines, and batteries that adds electric power to the fans of the engines. A conceptual aircraft sizing workflow built in the DLR’s “Remote Component Environment” (RCE) incorporating tools of DLR that are based on semi-empirical and low level physics based methods. The TRADE consortium developed a simulation and optimization design platform with analysis models of higher fidelity for an aircraft with hybrid electric propulsion architecture. An implementation of the TRADE simulation and optimization design platform into the DLR’s RCE workflow by replacing the DLR models was carried out. The focus of this paper is on the quantitative evaluation of the “Boosted Turbofan” configuration utilizing the resulting workflow. In order to understand the cooperation between the DLR and TRADE consortium, a brief overview of the activities is given. Then the multi-disciplinary overall aircraft sizing workflow for hybrid electric aircraft built in RCE is shown. Hereafter, the simulation and optimization models of the TRADE design platform are described. Subsequently, an overview of the aircraft configuration considered in the scope of this work is given. The design space studies of the “Boosted Turbofan” configuration are presented. Finally, the deviations of the results between the workflows with and without the TRADE modules are discussed.
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| 9. |
- Zhao, Xin, 1986
(författare)
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Aero Engine Intercooling
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Intercooling has the potential to provide a shortcut to the next generation aero engines with higher bypass ratio (BPR), higher overall pressure ratio (OPR) and higher turbine inlet temperature (TIT) by lowering the high pressure compressor (HPC) delivery temperature. To be able to establish a systematic understanding of aero engine intercooling, the heat transfer and pressure loss characteristics of a given intercooler architecture need to be known in the parameter range anticipated for the engine optimization. A two-pass cross flow tubular heat exchanger for aero engine intercooling applications was hence developed by the means of computational fluid dynamics (CFD). Optimizations with this intercooler installed were performed by considering the intercooler design parameters and the engine design simutaneously. A geared variant was adopted to complement the use of intercooling as it could support high OPR engines better by allowing a lower position installtion of the HPC. For a flight mission, further optimization of the intercooled engines was acheived by controlling the amount of intercooling for different engine operating points in two ways. One is intercooler external flow control by a separate variable nozzle and another one is intercooler internal flow variable flow path. As the flight altitude strongly influences the working condition for an aero engine, considerable SFC benefit can be obtained by limiting intercooling at high altitude operation. Nevertheless, the precondition is to enable a higher OPR at the take-off operation by intercooling. Compared to a reference non-intercooled geared engine, an optimal intercooled geared engine with intercooling control shows a 4.9\% better mission fuel burn under the same engine technology level assumptions. However, the optimum is still constrained by the last stage compressor blade height. To further explore the potentialof intercooling the constraint limiting the axial compressor last stage blade height isrelaxed by introducing an axial-radial combined HPC. The axial–radialhigh pressure ratio configuration allows for an ultrahigh OPR. With anoptimal top-of-climb (TOC) OPR of 140, the configuration provides a 5.3\% fuel burn benefitover the geared reference engine.Experimental validation of the intercooler design and the CFD design tool is also presented in this thesis. With the help of particle image velocimetry (PIV) and pressure measurements, flow topology inside the intercooler was visualized. Generally, by comparing the CFD results and the experimental data, the computational capability of porous media modeling predicting the flow distribution within the tubular heat transfer units was confirmed. The flow topology within the associated ducts was considered well-described by CFD.
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| 10. |
- Zhao, Xin, 1986, et al.
(författare)
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First and second law analysis of intercooled turbofan engine
- 2016
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Ingår i: Journal of Engineering for Gas Turbines and Power. - : ASME International. - 1528-8919 .- 0742-4795. ; 138:2
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Tidskriftsartikel (refereegranskat)abstract
- Although the benefits of intercooling for aero-engine applications have been realized and discussed in many publications, quantitative details are still relatively limited. In order to strengthen the understanding of aero-engine intercooling, detailed performance data on optimized intercooled (IC) turbofan engines are provided. Analysis is conducted using an exergy breakdown, i.e., quantifying the losses into a common currency by applying a combined use of the first and second law of thermodynamics. Optimal IC geared turbofan engines for a long range mission are established with computational fluid dynamics (CFD) based two-pass cross flow tubular intercooler correlations. By means of a separate variable nozzle, the amount of intercooler coolant air can be optimized to different flight conditions. Exergy analysis is used to assess how irreversibility is varying over the flight mission, allowing for a more clear explanation and interpretation of the benefits. The optimal IC geared turbofan engine provides a 4.5% fuel burn benefit over a non-IC geared reference engine. The optimum is constrained by the last stage compressor blade height. To further explore the potential of intercooling the constraint limiting the axial compressor last stage blade height is relaxed by introducing an axial radial high pressure compressor (HPC). The axial–radial high pressure ratio (PR) configuration allows for an ultrahigh overall PR (OPR). With an optimal top-of-climb (TOC) OPR of 140, the configuration provides a 5.3% fuel burn benefit over the geared reference engine. The irreversibilities of the intercooler are broken down into its components to analyze the difference between the ultrahigh OPR axial–radial configuration and the purely axial configuration. An intercooler conceptual design method is used to predict pressure loss heat transfer and weight for the different OPRs. Exergy analysis combined with results from the intercooler and engine conceptual design are used to support the conclusion that the optimal PR split exponent stays relatively independent of the overall engine PR.
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