| 1. |
- Thulin, Oskar, 1987, et al.
(författare)
-
First and Second Law Analysis of Radical Intercooling Concepts
- 2018
-
Ingår i: Journal of Engineering for Gas Turbines and Power. - : ASME International. - 1528-8919 .- 0742-4795. ; 140:8, s. 081201-081201-10
-
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.
|
|
| 2. |
- Thulin, Oskar, 1987
(författare)
-
On the Analysis of Energy Efficient Aircraft Engines
- 2017
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Aero engine performance analysis is highly multidimensional using various measures of component performance such as turbomachinery and mechanical efficiencies, and pressure loss coefficients. Using conventional performance analysis, relying on only the laws of thermodynamics, it is possible to understand how the performance parameters affect the component performance, but it is difficult to directly compare the magnitude of various loss sources. A comprehensive framework has been detailed to analyze aero engine loss sources in one common currency. As the common currency yields a measure of the lost work potential in every component, it is used to relate the component performance to the system performance. The theory includes a more detailed layout of all the terms that apply to a propulsion unit than presented before. The framework is here adopted to real gases to be used in state of the art performance codes. Additionally, the framework is further developed to enable detailed studies of two radical intercooling concepts that either rejects the core heat in the outer nacelle surfaces or uses the core heat for powering of a secondary cycle. The theory is also extended upon by presenting the installed rational efficiency, a true measure of the propulsion subsystem performance, including the installation effects of the propulsion subsystem as it adds weight and drag that needs to be compensated for in the performance assessment.
|
|
| 3. |
- Grönstedt, Tomas, 1970, et al.
(författare)
-
First and Second Law Analysis of Future Aircraft Engines
- 2014
-
Ingår i: Journal of Engineering for Gas Turbines and Power. - : ASME International. - 1528-8919 .- 0742-4795. ; 136:3
-
Tidskriftsartikel (refereegranskat)abstract
- An optimal baseline turbofan cycle designed for a performance level expected to be available around year 2050 is established. Detailed performance data are given in take-off, top of climb, and cruise to support the analysis. The losses are analyzed, based on a combined use of the first and second law of thermodynamics, in order to establish a basis for a discussion on future radical engine concepts and to quantify loss levels of very high performance engines. In light of the performance of the future baseline engine, three radical cycles designed to reduce the observed major loss sources are introduced. The combined use of a first and second law analysis of an open rotor engine, an intercooled recuperated engine, and an engine working with a pulse detonation combustion core is presented. In the past, virtually no attention has been paid to the systematic quantification of the irreversibility rates of such radical concepts. Previous research on this topic has concentrated on the analysis of the turbojet and the turbofan engine. In the developed framework, the irreversibility rates are quantified through the calculation of the exergy destruction per unit time. A striking strength of the analysis is that it establishes a common currency for comparing losses originating from very different physical sources of irreversibility. This substantially reduces the complexity of analyzing and comparing losses in aero engines. In particular, the analysis sheds new light on how the intercooled recuperated engine establishes its performance benefits.
|
|
| 4. |
- Thulin, Oskar, 1987, et al.
(författare)
-
A Mission Assessment of Aero Engine Losses
- 2015
-
Ingår i: ISABE-2015-20121.
-
Konferensbidrag (refereegranskat)abstract
- A detailed and systematic loss breakdown of a direct drive two-spool turbofan aero engine integrated to an aircraft corresponding to a technology level of year 2020is produced from engine mission point performance simulations. The analysis includes the fundamental mission points throughout a commercial aircraft mission. The breakdown also incorporates the inherent effects of the propulsion system such as engine weight and nacelle drag. A new term, installed rational efficiency, is proposed to fully assess the performance of the propulsion subsystem. Combining the detailed component loss analysis with the assessment of the installation effects provides a systematic as well as effective way of analyzing the full impact of an aircraft component, likethe engine subsystem, on the aircraft. This can be used to truly assess the performance of one propulsion unitcompared to another.
|
|
| 5. |
- Grönstedt, Tomas, 1970, et al.
(författare)
-
First and Second Law Analysis of Future Aircraft Engines
- 2013
-
Ingår i: ASME Turbo Expo, 2013. - 9780791855133 ; 2:GT2013-95516
-
Konferensbidrag (refereegranskat)abstract
- An optimal baseline turbofan cycle designed for a performance level expected to be available around year 2050 is established. Detailed performance data are given in take-off, top of climb and cruise to support the analysis. Losses are analyzed based on a combined use of the first and second law of thermodynamics, to establish a basis for discussion on future radical engine concepts and to quantify loss levels of very high performance engines. In the light of the performance of the future baseline engine, three radical cycles designed to reduce the observed major loss sources are introduced. The combined use of a first and second law analysis of an open rotor engine, an intercooled recuperated engine and an engine working with a pulse detonation combustion core is presented. In the past, virtually no attention has been paid to the systematic quantification of the irreversibility rates of such radical concepts. Previous research on this topichas concentrated on the analysis of the turbojet and the turbofan engine. In the framework developed, the irreversibility rates are quantified through the calculation of the exergy destruction per unit time. A striking strength of the analysis is that it establishes a common currency for comparing losses originating from very different physical sources of irreversibility. This substantially reduces the complexity of analyzing and comparing losses in aero engines. In particular, the analysis sheds new light on how the intercooled recuperated engine establishes its performance benefits.
|
|
| 6. |
- Thulin, Oskar, 1987
(författare)
-
On Exergy and Aero Engine Applications
- 2016
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Aero engine performance analysis is highly multidimensional using various measures of component performance such as turbomachinery and mechanical efficiencies, and pressure loss coefficients. Using conventional performance analysis, relying on only the first law of thermodynamics, it is possible to understand how the performance parameters affect the component performance, but not how the component performance relates to the system performance. A comprehensive framework has been detailed to analyze an aero engine in one common currency by complementing the analysis with the second law of thermodynamics. As it yields a measure of the lost work potential in every component it is used to relate the component performance to the system performance. The theory includes a more detailed layout of all the terms that apply to a propulsion unit than presented before and is here adopted to real gases to be used in state of the art performance codes. The theory is also extended upon by presenting the installed rational efficiency, a true measure of the propulsion subsystem performance, including the installation effects of the propulsion subsystem as it adds weight and drag that needs to be compensated for in the performance assessment.The exergy methodology is applied to a modern direct-drive two-spool turbofan, chosen for its dominating market share in modern commercial aviation. The loss sources during an aircraft mission are then assessed and yield the major contributors in the entropy generated during combustion, the thermal energy leaving the nozzle and the exhaust nozzle kinetic energy that is not contributing to the thrust. Radical technology that can be utilized to address each specific loss are thereafter detailed. This includes intercooled and recuperated cycles, reheated cycles, bottoming Rankine cycles, pulse detonation combustion, piston topped composite cycles, nutating disc combustion, and open rotor and other ultra high bypass architectures.
|
|
| 7. |
- Jonsson, Isak, 1990, et al.
(författare)
-
Experimental and Numerical Study of Laminar-Turbulent Transition on a Low-Pressure Turbine Outlet Guide Vane
- 2020
-
Ingår i: Proceedings of the ASME Turbo Expo. ; 2B
-
Konferensbidrag (refereegranskat)abstract
- In modern commercial aviation engines, the low-pressure turbine (LPT) has a high outlet swirl to maximize turbine power to weight ratio. Downstream of the last LPT rotor is the turbine rear structure (TRS) that with relatively few low-aspect-ratio outlet guide vanes (OGV) de-swirls the flow to maximize the thrust. The performance of the TRS is strongly connected to secondary flow structures, which in turn are strongly influenced by the laminar-turbulent transition. Transition can be challenging to predict in turbomachinery due to the highly complex flow present. At the design point the TRS can have both by-pass transition and laminar separation with transition and a following turbulent reattachment. In addition, a TRS needs to perform well in a large off-design envelope, with large variations of the inlet swirl angle. Accurately predicting transition, both at the design point and in important off-design points, is critical for the development of future TRS modules. In modern geared and ultra-high by-pass engines the TRS swirl angle off-design requirements are also increasing. There are several available transition models in RANS simulations and most of them need parameter tuning when introduced to new conditions. Evaluation of these models for different turbomachinery components is relatively well covered in the literature even though the model specifics often is a classified property of engine manufacturers. However, there are no cases in the literature of transition prediction with experimental verification in the TRS at engine-realistic conditions. This work presents the first experimental verification of laminar-turbulent transition in a TRS module tested in the LPT-OGV experimental facility at Chalmers Laboratory of Thermal and Fluid Science. The facility is a semi-closed rig using a rotating 1.5 stage shrouded low-pressure turbine stage to create engine representative inlet conditions for the TRS downstream of the LPT stage. Transition was measured using differential IR-thermography (DIT) which is a non-intrusive two-dimensional measurement technique. The technique was specially developed at Chalmers for this particular purpose and validated by boundary layer hot-wire measurements. The numerical analysis was done using commercially available transition models in Fluent and Ansys CFX. Gamma-theta transition model was used with the k-omega SST turbulence model. Experiments and numerical simulations were performed at a chord Reynold number of 235000 and with LPT outlet swirl angles covering both the design point (ADP) and relevant off-design points. Numerical and experimental results show that agreement between transition models and experiments can be achieved at these conditions. Boundary layers on the pressure side and suction side undergo laminar-turbulent transition for the selected test range. At decreased OGV aerodynamic load, the boundary layer on the pressure side near the leading edge is laminar along most of the span. At higher OGV loads the secondary flow is influencing the region near the shroud on the pressure side as well as near the hub on the suction side. The transition on the suction side midspan is significantly influenced by the vane load. The numerical analysis was used to better understand the involved flow mechanisms.
|
|
| 8. |
- Zhao, Xin, 1986, et al.
(författare)
-
First and second law analysis of intercooled turbofan engine
- 2016
-
Ingår i: Journal of Engineering for Gas Turbines and Power. - : ASME International. - 1528-8919 .- 0742-4795. ; 138:2
-
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.
|
|
| 9. |
- Thulin, Oskar, 1987, et al.
(författare)
-
First and second law analysis of radical intercooling concepts
- 2017
-
Ingår i: Proceedings of the ASME Turbo Expo. - 9780791850770 ; 1
-
Konferensbidrag (refereegranskat)abstract
- An exergy framework was developed taking into consideration a detailed analysis of the heat exchanger (intercooler) component irreversibilities. Moreover, it was further extended to include an adequate formulation for closed systems, e.g. a secondary cycle, moving with the aircraft. Afterwards 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 contribute 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 turbofan engine, with technology levels assumed to be available by year 2025. A reference intercooled cycle incorporating a heat exchanger in the bypass 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 heat exchangers and the secondary cycle major components is made. A striking strength of the present analysis is the assessment of the component irreversibility rate and its contribution to the overall aero-engine losses.
|
|
| 10. |
- Zhao, Xin, 1986, et al.
(författare)
-
First and second law analysis of intercooled turbofan engine
- 2015
-
Ingår i: ASME Turbo Expo 2015, Montreal Canada, GT2015-43187.
-
Konferensbidrag (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 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 intercooled geared turbofan engines for a long range mission are established with 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 intercooled geared turbofan engine provides a 4.5% fuel burn benefit over a non-intercooled 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. The axial-radial high pressure ratio configuration allows for an ultra-high overall pressure ratio. With an optimal top-of-climb overall pressure ratio 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 ultra-high overall pressure ratio 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 overall pressure ratios. Exergy analysis combined with results from the intercooler and engine conceptual design are used to support the conclusion that the optimal pressure ratio split exponent stays relatively independent of the overall engine pressure ratio.
|
|
