First and Second Law Analysis of Intercooled Turbofan Engine

2015 ◽  
Author(s):  
Xin Zhao ◽  
Oskar Thulin ◽  
Tomas Grönstedt
Keyword(s):  
High Pressure ◽  
Exergy Analysis ◽  
Pressure Ratio ◽  
Second Law ◽  
Turbofan Engine ◽  
Blade Height ◽  
Turbofan Engines ◽  
Fuel Burn ◽  
Aero Engine ◽  
Last Stage

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.

First and Second Law Analysis of Intercooled Turbofan Engine

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Xin Zhao ◽  
Oskar Thulin ◽  
Tomas Grönstedt
Keyword(s):  
High Pressure ◽  
Conceptual Design ◽  
Exergy Analysis ◽  
Second Law ◽  
Turbofan Engine ◽  
Blade Height ◽  
Turbofan Engines ◽  
Fuel Burn ◽  
Aero Engine ◽  
Last Stage

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.

On the Optimization of a Geared Fan Intercooled Core Engine Design

2014 ◽  
Vol 137 (4) ◽  
Author(s):  
Konstantinos G. Kyprianidis ◽  
Andrew M. Rolt
Keyword(s):  
Fuel Consumption ◽  
Design Space ◽  
Pressure Ratio ◽  
System Level ◽  
Design Parameters ◽  
Customer Requirements ◽  
Blade Height ◽  
Fuel Burn ◽  
Engine Design ◽  
Last Stage

Reduction of CO2 emissions is strongly linked with the improvement of engine specific fuel consumption (SFC), as well as the reduction of engine nacelle drag and weight. One alternative design approach to improving SFC is to consider a geared fan combined with an increased overall pressure ratio (OPR) intercooled core performance cycle. Thermal benefits from intercooling have been well documented in the literature. Nevertheless, there is little information available in the public domain with respect to design space exploration of such an engine concept when combined with a geared fan. The present work uses a multidisciplinary conceptual design tool to further analyze the option of an intercooled core geared fan aero engine for long haul applications with a 2020 entry into service technology level assumption. The proposed design methodology is capable, with the utilized tool, of exploring the interaction of design criteria and providing critical design insight at engine–aircraft system level. Previous work by the authors focused on understanding the design space for this particular configuration with minimum SFC, engine weight, and mission fuel in mind. This was achieved by means of a parametric analysis, varying several engine design parameters—but only one at a time. The present work attempts to identify “globally” fuel burn optimal values for a set of engine design parameters by varying them all simultaneously. This permits the nonlinear interactions between the parameters to be accounted for. Special attention has been given to the fuel burn impact of the reduced high pressure compressor (HPC) efficiency levels associated with low last stage blade heights. Three fuel optimal designs are considered, based on different assumptions. The results indicate that it is preferable to trade OPR and pressure ratio split exponent, rather than specific thrust, as means of increasing blade height and hence reducing the associated fuel consumption penalties. It is interesting to note that even when considering the effect of HPC last stage blade height on efficiency there is still an equivalently good design at a reduced OPR. This provides evidence that the overall economic optimum could be for a lower OPR cycle. Customer requirements such as take-off distance and time to height play a very important role in determining a fuel optimal engine design. Tougher customer requirements result in bigger and heavier engines that burn more fuel. Higher OPR intercooled engine cycles clearly become more attractive in aircraft applications that require larger engine sizes.

On the Optimisation of a Geared Fan Intercooled Core Engine Design

2014 ◽  
Author(s):  
Konstantinos G. Kyprianidis ◽  
Andrew M. Rolt
Keyword(s):  
Fuel Consumption ◽  
Design Space ◽  
Pressure Ratio ◽  
Specific Fuel Consumption ◽  
Design Parameters ◽  
Customer Requirements ◽  
Blade Height ◽  
Fuel Burn ◽  
Engine Design ◽  
Last Stage

Reduction of CO2 emissions is strongly linked with the improvement of engine specific fuel consumption, as well as the reduction of engine nacelle drag and weight. One alternative design approach to improving specific fuel consumption is to consider a geared fan combined with an increased overall pressure ratio intercooled core performance cycle. Thermal benefits from intercooling have been well documented in the literature. Nevertheless, there is little information available in the public domain with respect to design space exploration of such an engine concept when combined with a geared fan. The present work uses a multidisciplinary conceptual design tool to further analyse the option of an intercooled core geared fan aero engine for long haul applications with a 2020 entry into service technology level assumption. The proposed design methodology is capable, with the utilised tool, of exploring the interaction of design criteria and providing critical design insight at engine-aircraft system level. Previous work by the authors focused on understanding the design space for this particular configuration with minimum specific fuel consumption, engine weight and mission fuel in mind. This was achieved by means of a parametric analysis, varying several engine design parameters — but only one at a time. The present work attempts to identify “globally” fuel burn optimal values for a set of engine design parameters by varying them all simultaneously. This permits the non-linear interactions between the parameters to be accounted. Special attention has been given to the fuel burn impact of the reduced HPC efficiency levels associated with low last stage blade heights. Three fuel optimal designs are considered, based on different assumptions. The results indicate that it is preferable to trade overall pressure ratio and pressure ratio split exponent, rather than specific thrust, as means of increasing blade height and hence reducing the associated fuel consumption penalties. It is interesting to note that even when considering the effect of HPC last stage blade height on efficiency there is still an equivalently good design at a reduced overall pressure ratio. This provides evidence that the overall economic optimum could be for a lower overall pressure ratio cycle. Customer requirements such as take-off distance and time to height play a very important role in determining a fuel optimal engine design. Tougher customer requirements result in bigger and heavier engines that burn more fuel. Higher overall pressure ratio intercooled engine cycles clearly become more attractive in aircraft applications that require larger engine sizes.

Design and Analysis of an Intercooled Turbofan Engine

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
Lei Xu ◽  
Tomas Grönstedt
Keyword(s):  
Mechanical Design ◽  
Pressure Ratio ◽  
Engine Performance ◽  
Turbine Rotor ◽  
Performance Model ◽  
Multidisciplinary Optimization ◽  
Turbofan Engine ◽  
Blade Height ◽  
Turbine Rotor Blade ◽  
Fuel Burn

The performance of an intercooled turbofan engine is analyzed by multidisciplinary optimization. A model for making preliminary simplified analysis of the mechanical design of the engine is coupled to an aircraft model and an engine performance model. A conventional turbofan engine with technology representative for a year 2013 entry of service is compared with a corresponding intercooled engine. A mission fuel burn reduction of 3.4% is observed. The results are analyzed in terms of the relevant constraints such as compressor exit temperature, turbine entry temperature, turbine rotor blade temperature, and compressor exit blade height. It is shown that the gas path of an intercooled engine for medium range commercial transport applications, having an overall pressure ratio greater than 70 in top of climb, may still be optimized to fulfill a compressor exit blade height constraint. This indicates that a state of the art high pressure compressor efficiency can be achieved. Empirical data and a parametric computational fluid dynamics (CFD) study are used to verify the intercooler heat transfer and pressure loss characteristics.

Heat-Exchanged Propulsion Gas Turbines: A Candidate for Future Lower SFC and Reduced-Emission Military and Civil Aeroengines

2009 ◽  
Author(s):  
Colin F. McDonald ◽  
Colin Rodgers
Keyword(s):  
Gas Turbines ◽  
High Efficiency ◽  
Pressure Ratio ◽  
Thermodynamic Cycle ◽  
Simple Cycle ◽  
Specific Power ◽  
Operational Experience ◽  
Fuel Cost ◽  
Turbofan Engines ◽  
Fuel Burn

After seven decades of service the evolution of simple cycle propulsion gas turbines continues with emphasis now being placed on reduced fuel burn, lower emissions, and less noise. With compressor and turbine efficiencies near plateauing, and turbine inlet temperatures paced by materials and blade cooling technologies, improvements in SFC, specific power and weight for conventional engines (including small turboprop, and turboshaft engines and larger turbofans) will likely be incremental compared with the past. With retention of the simple cycle both evolutionary and revolutionary approaches are being taken by the aeroengine industry to improve performance, particularly reduced fuel burn in an era of high fuel cost. In this paper a further step is suggested, that is in concert with meeting performance, economic, and environmental goals of future aeroengines, namely the use of a more complex thermodynamic cycle involving recuperation for turboprop and turboshaft engines, and intercooling together with recuperation for higher pressure ratio turbofan engines. The idea of heat exchanged propulsion gas turbines is not new, but the many concepts identified from studies done periodically over the last 65 years, including the few engines that were static tested and one test flown, didn’t find acceptance in an era of low fuel cost and concerns about recuperator integrity and reliability. With today’s very high fuel cost there is current interest in this type of engine because of its potential for low SFC and reduced emissions. In this paper potential applications are summarized and the features of various heat exchanged aeroengine design concepts together with projected performance are presented. Included is a discussion on the various issues that must be resolved before they enter service. A postulated deployment scenario is suggested with engines initially developed to meet military aviation needs, such as recuperated turboprop and turbofan engines for extended range UAV’s, followed by a recuperated turboshaft engine for a helicopter. Operational experience and demonstrated reliability from these would pave the way for high efficiency ICR turbofan engines for military and civil aircraft service sometime after the year 2020.

scholarly journals Variable Flow Turbofan Engine for an HSCT Application

1997 ◽  
Author(s):  
George L. Converse ◽  
Donald K. Dunbar ◽  
Marlen L. Miller ◽  
Paul D. Hoskins ◽  
Scott M. Jones
Keyword(s):  
Mach Number ◽  
Pressure Ratio ◽  
High Flow ◽  
Turbofan Engine ◽  
Variable Flow ◽  
Guide Vanes ◽  
Turbofan Engines ◽  
Inlet Guide Vanes ◽  
Specific Thrust ◽  
Aircraft Propulsion System

A variable flow fan aircraft propulsion system offers the potential for achieving a low specific thrust with high flow and low jet velocity requirement as specified for takeoff, side-line noise, initial climb, and a high specific thrust requirement for climb and acceleration to supersonic cruise. These requirements are conflicting. To achieve this, the operating envelope of a variable flow fan has to be expanded over existing turbofan engines. The variable flow fan concept (i.e., the Variable Fan Exit or “VFX”) can efficiently operate beyond the usual fan (or compressor) stall operating line using novel methods of designing and scheduling the fan geometry as a function of flight Mach Number, fan pressure ratio and corrected speed. Fan geometry is altered by using variable inlet guide vanes (IGV’s), variable stators, and variable outlet guide vanes (OGV’s).

scholarly journals Design Considerations of Low Bypass Ratio Mixed Flow Turbofan Engines with Large Power Extraction

Fluids ◽  
2022 ◽  
Vol 7 (1) ◽  
pp. 21
Author(s):  
Daniel Rosell ◽  
Tomas Grönstedt
Keyword(s):  
High Pressure ◽  
Inlet Temperature ◽  
Mixed Flow ◽  
Turbine Inlet Temperature ◽  
Fighter Aircraft ◽  
Turbofan Engine ◽  
Large Power ◽  
Power Extraction ◽  
Turbofan Engines ◽  
Bypass Ratio

The possibility of extracting large amounts of electrical power from turbofan engines is becoming increasingly desirable from an aircraft perspective. The power consumption of a future fighter aircraft is expected to be much higher than today’s fighter aircraft. Previous work in this area has concentrated on the study of power extraction for high bypass ratio engines. This motivates a thorough investigation of the potential and limitations with regards to performance of a low bypass ratio mixed flow turbofan engine. A low bypass ratio mixed flow turbofan engine was modeled, and key parts of a fighter mission were simulated. The investigation shows how power extraction from the high-pressure turbine affects performance of a military engine in different parts of a mission within the flight envelope. An important conclusion from the analysis is that large amounts of power can be extracted from the turbofan engine at high power settings without causing too much penalty on thrust and specific fuel consumption, if specific operating conditions are fulfilled. If the engine is operating (i) at, or near its maximum overall pressure ratio but (ii) further away from its maximum turbine inlet temperature limit, the detrimental effect of power extraction on engine thrust and thrust specific fuel consumption will be limited. On the other hand, if the engine is already operating at its maximum turbine inlet temperature, power extraction from the high-pressure shaft will result in a considerable thrust reduction. The results presented will support the analysis and interpretation of fighter mission optimization and cycle design for future fighter engines aimed for large power extraction. The results are also important with regards to aircraft design, or more specifically, in deciding on the best energy source for power consumers of the aircraft.

scholarly journals Assessment of CO2 and NOx Emissions in Intercooled Pulsed Detonation Turbofan Engines

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Carlos Xisto ◽  
Olivier Petit ◽  
Tomas Grönstedt ◽  
Anders Lundbladh
Keyword(s):  
Gas Turbine ◽  
Equivalence Ratio ◽  
Nox Emissions ◽  
Simulation Tool ◽  
Turbofan Engines ◽  
Fuel Burn ◽  
Pulsed Detonation ◽  
Detonation Combustion ◽  
Aero Engine ◽  
Computational Fluid Dynamics Cfd

In the present paper, the synergistic combination of intercooling with pulsed detonation combustion is analyzed concerning its contribution to NOx and CO2 emissions. CO2 is directly proportional to fuel burn and can, therefore, be reduced by improving specific fuel consumption (SFC) and reducing engine weight and nacelle drag. A model predicting NOx generation per unit of fuel for pulsed detonation combustors (PDCs), operating with jet-A fuel, is developed and integrated within Chalmers University's gas turbine simulation tool GESTPAN. The model is constructed using computational fluid dynamics (CFD) data obtained for different combustor inlet pressure, temperature, and equivalence ratio levels. The NOx model supports the quantification of the trade-off between CO2 and NOx emissions in a 2050 geared turbofan architecture incorporating intercooling and pulsed detonation combustion and operating at pressures and temperatures of interest in gas turbine technology for aero-engine civil applications.

Advanced Exergy Analysis of a Turbofan Engine (TFE): Splitting Exergy Destruction into Unavoidable/Avoidable and Endogenous/Exogenous

2017 ◽  
Vol 0 (0) ◽  
Author(s):  
Ozgur Balli
Keyword(s):  
High Pressure ◽  
Exergy Analysis ◽  
Low Pressure ◽  
Operating Conditions ◽  
Actual Condition ◽  
Exergy Destruction ◽  
Turbofan Engine ◽  
High Pressure Compressor ◽  
Engine Components ◽  
Pressure Compressor

AbstractA conventional and advanced exergy analysis of a turbofan engine is presented in this paper. In this framework, the main exergy parameters of the engine components are introduced while the exergy destruction rates within the engine components are split into endogenous/exogenous and avoidable/unavoidable parts. Also, the mutual interdependencies among the components of the engine and realistic improvement potentials depending on operating conditions are acquired through the analysis. As a result of the study, the exergy efficiency values of the engine are determined to be 25.7 % for actual condition, 27.55 % for unavoidable condition and 30.54 % for theoretical contion, repectively. The system has low improvement potential because the unavoidable exergy destruction rate is 90 %. The relationships between the components are relatively weak since the endogenous exergy destruction is 73 %. Finally, it may be concluded that the low pressure compressor, the high pressure compressor, the fan, the low pressure compressor, the high pressure compressor and the combustion chamber of the engine should be focused on according to the results obtained.

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