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.

An Evaluation of the Geometry and Weight of a Mixed Flow Low Bypass Ratio Turbofan Engine With an Intermediate Turbine Burner

2005 ◽  
Author(s):  
Chorng-Yow Chen ◽  
Mark H. Waters ◽  
Dimitri Mavris
Keyword(s):  
Mechanical Design ◽  
Pressure Ratio ◽  
Flow Path ◽  
Mixed Flow ◽  
Turbofan Engine ◽  
Turbofan Engines ◽  
Low Pressure Turbine ◽  
The Subject ◽  
Specific Thrust ◽  
Bypass Ratio

Turbofan engines are designed with two or even three spools of fan- compressor and turbine combinations. This arrangement allows the possibility of increased power output by placing a second combustor between turbine spools. Such a combustor is called an “Intermediate Turbine Burner, ITB,” and in a twin spool turbofan engine the combustor would be placed between the discharge of the high pressure turbine and the entrance of the low pressure turbine. An evaluation of the mechanical design of an ITB integrated into a low bypass ratio mixed flow turbofan is the subject of this paper. It is well known that an engine with an ITB has increased specific thrust but at the expense of increased specific fuel consumption. To take advantage of the ITB potential, the choice of cycle parameters — fan pressure ratio, overall pressure ratio and bypass ratio must be evaluated, and recent studies have demonstrated that the turbofan cycle with an ITB should have increased fan and overall pressure ratios to maximize performance. However, little has been done to estimate the weight and dimensions of an ITB integrated engine including the weight, flow path area and length of the ITB. Of particular concern are the volume and resulting flow path area and length required for the ITB.

scholarly journals The impact of thermodynamics parameters of turbofan engine with ITB on its performance

2020 ◽  
Vol 182 (3) ◽  
pp. 16-22
Author(s):  
Natalia Marszałek
Keyword(s):  
Combustion Chamber ◽  
Pressure Ratio ◽  
Alternative Fuel ◽  
Inlet Temperature ◽  
Hydrogen Fuel ◽  
Turbine Inlet Temperature ◽  
Turbofan Engine ◽  
Specific Thrust ◽  
The Impact ◽  
Bypass Ratio

Presented paper is focused on the influence of additional combustor chamber named inter turbine burner on turbofan engine unit parameters. Investigation has been made how changing selected engine parameters affect its performance. A comparison has been made between the baseline turbofan engine and the engine with ITB. Engine thermodynamics model was prepared in MATLAB software. Main combustion chamber was fueled by kerosene, commmonly used in aviation transport, while inter turbine burner by alternative fuel. As an alternative fuel were choose liquid hydrogen and methane. Numerical researches were carried out for take-off conditions. Engine specific thrust and specific fuel consumption were obtained as a function of bypass ratio, turbine inlet temperature, fan pressure ratio, HPC and LPC pressure ratio. The results of the study indicate that hybrid engine with additional combustion chamber fueled by hydrogen fuel is more efficient than other studied cases.

Design and Analysis of an Aircraft Thermal Management System Linked to a Low Bypass Ratio Turbofan Engine

2021 ◽  
Author(s):  
Robert Clark ◽  
Mingxuan Shi ◽  
Jonathan Gladin ◽  
Dimitri N. Mavris
Keyword(s):  
Thermal Management ◽  
Management System ◽  
Cooling System ◽  
Maximum Load ◽  
Fighter Aircraft ◽  
Turbofan Engine ◽  
Cycle System ◽  
Thermal Management System ◽  
Air Stream ◽  
Bypass Ratio

Abstract The design of an aircraft thermal management system (TMS) that is capable of rejecting heat loads into the bypass stream of a typical low-bypass ratio turbofan engine, or a ram-air stream, is investigated. The TMS consists of an air cycle system, similar to the typical air cycle machines used on current aircraft, both military and commercial. This system turbocharges compressor bleed air and uses heat exchangers in a ram air stream, or the engine bypass stream, to cool the engine bleed air prior to expanding it to low temperatures suitable for heat rejection. In this study, a simple low-bypass ratio afterburning turbofan engine was modeled in NPSS to provide boundary conditions to the TMS system throughout the flight envelope of a typical military fighter aircraft. Two variations of the TMS system, a ram air cooled and a bypass air cooled, were sized to handle a given demanded aircraft heat load. The ability of the sized TMS to reject the demanded aircraft load throughout several key off-design points was analyzed. It was observed that the maximum load dissipation capability of the TMS is tied to the amount of engine bleed flow, while the level of bleed flow required is set by the temperature conditions imposed by the aircraft cooling system. Notably, engine bypass stream temperatures significantly limit the thermodynamic viability of a TMS designed with bypass air as the heat sink. The results demonstrate the advantage that variable cycle engines may have for future aircraft designs.

THE INFLUENCE OF PURGE FLOW PARAMETERS ON HEAT TRANSFER AND FILM COOLING IN TURBINE CENTER FRAMES

2021 ◽  
pp. 1-26
Author(s):  
Patrick René Jagerhofer ◽  
Marios Patinios ◽  
Tobias Glasenapp ◽  
Emil Goettlich ◽  
Federica Farisco
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Film Cooling ◽  
Density Ratio ◽  
Constant Heat Flux ◽  
Inlet Temperature ◽  
High Pressure Turbine ◽  
Turbofan Engines ◽  
Blowing Ratio ◽  
Purge Flow

Abstract The imperative improvement in the efficiency of turbofan engines is commonly facilitated by increasing the turbine inlet temperature. This development has reached a point where also components downstream of the high-pressure turbine have to be adequately cooled. Such a component is the turbine center frame (TCF), known for a complex aerodynamic flow highly influenced by purge-mainstream interactions. The purge air, being injected through the wheelspace cavities of the upstream high-pressure turbine, bears a significant cooling potential for the TCF. Despite this, fundamental knowledge of the influencing parameters on heat transfer and film cooling in the TCF is still missing. This paper examines the influence of purge-to-mainstream blowing ratio, density ratio and purge swirl angle on heat transfer and film cooling in the TCF. The experiments are conducted in a sector-cascade test rig specifically designed for such heat transfer studies using infrared thermography and tailor-made flexible heating foils with constant heat flux. Three purge-to-mainstream blowing ratios and an additional no purge case are investigated. The purge flow is injected without swirl and also with engine-similar swirl angles. The purge swirl and blowing ratio significantly impact the magnitude and the spread of film cooling in the TCF. Increasing blowing ratios lead to an intensification of heat transfer. By cooling the purge flow, a moderate variation in purge-to-mainstream density ratio is investigated, and the influence is found to be negligible.

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.

Analyses and Optimization of a Propulsion Cycle for Unmixed High Bypass Turbofan

2008 ◽  
Author(s):  
Adel Ghenaiet
Keyword(s):  
Fuel Consumption ◽  
Pressure Ratio ◽  
Specific Fuel Consumption ◽  
Design Parameters ◽  
Inlet Temperature ◽  
Turbine Inlet Temperature ◽  
High Pressure Ratio ◽  
Turbine Inlet ◽  
Design Variables ◽  
Bypass Ratio

This paper deals with a parametric study and an optimization for the design variables of a high bypass unmixed turbofan equipping commercial aircrafts. The objective of the first part of this study is to highlight the effects of the principal design parameters (bypass ratio, compression ratios, turbine inlet temperature etc..) on the uninstalled performance, in terms of specific thrust and specific fuel consumption. The second part concerns the optimization, aiming at finding the optimum design parameters concurrently minimizing the specific fuel consumption at cruise, and meeting the thrust requirement at takeoff. The cycle analyzer (on-design and off-design) as coupled to the optimization algorithm MMFD by adopting a random multi-starts search strategy is shown to be stable and converging. The predefined requirements and constraints have dictated utilizing an engine with a high-bypass ratio, high-pressure ratio and a moderate turbine inlet temperature. In general, the obtained results compare fairly well with typical data available for an equivalent ‘reference’ engine. This elaborated methodology is shown to be consistent with the conceptual design requirements and accuracy, because, it does not use components’ characteristics, and operates on simplifying assumptions. This present methodology can be readily adapted for other configurations of aero-engines as well, and easily integrated in a multi-disciplinary design approach.

Optimum Cycle Parameters for Turbofan Engines

1970 ◽  
Author(s):  
W. C. Moffatt
Keyword(s):  
Simple Procedure ◽  
Pressure Ratio ◽  
Inlet Temperature ◽  
Closed Form Solutions ◽  
Turbofan Engines ◽  
Compressor Pressure Ratio ◽  
Temperature Component ◽  
Flow Through ◽  
Specific Thrust ◽  
Bypass Ratio

This paper presents closed-form solutions for optimum compressor pressure ratio, bypass ratio and fan pressure ratio, given the turbine inlet temperature, component efficiencies and flight Mach number for a turbofan engine. In addition a simple procedure is outlined for obtaining the optimum combination of these quantities and a sample calculation is included. The optimum condition is defined as that which maximizes the specific thrust (thrust per pound per second of air flow through the gasifier) of the engine. The effects of differing gas properties in different portions of the engine are included in the analysis.

Results From High Temperature Turbine Test on the HPT of the AGTJ-100A

1984 ◽  
Author(s):  
Masashi Arai ◽  
Kiyomi Teshima ◽  
Sunao Aoki ◽  
Hiroyuki Yamao
Keyword(s):  
Experimental Investigation ◽  
High Pressure ◽  
High Temperature ◽  
Aerodynamic Performance ◽  
Inlet Temperature ◽  
Test Results ◽  
Mechanical Reliability ◽  
High Pressure Turbine ◽  
Turbine Inlet Temperature ◽  
Turbine Efficiency

An experimental investigation was conducted through the use of a High Temperature Turbine Developing Unit (HTDU) having the same two stage turbine as the high pressure turbine (HPT) of the AGTJ-100A, to ascertain the aerodynamic performance, cooling characteristics and mechanical reliability. The test was performed in three phases, and the maximum turbine inlet temperature was about 1,573 K. The test results showed that turbine efficiency was 90.2 %, the level of metal temperature for nozzles and blades was as expected, and there was little trouble with the hot parts. This paper will present these test results.

Performance of a Novel Combined Cooling and Power Gas Turbine With Water Harvesting

2004 ◽  
Author(s):  
J. R. Khan ◽  
W. E. Lear ◽  
S. A. Sherif
Keyword(s):  
High Pressure ◽  
Gas Turbine ◽  
Inlet Temperature ◽  
Absorption Refrigeration ◽  
Ambient Conditions ◽  
Turbine Inlet Temperature ◽  
Refrigeration Unit ◽  
Vapor Absorption ◽  
Vapor Absorption Refrigeration ◽  
Pressure Compressor

A thermodynamic performance analysis is performed on a novel cooling and power cycle that combines a semi-closed cycle gas turbine called the High Pressure Regenerative Turbine Engine (HPRTE) with an absorption refrigeration unit. Waste heat from the recirculated combustion gas of the HPRTE is used to power the absorption refrigeration unit, which cools the high-pressure compressor inlet of the HPRTE to below ambient conditions and also produces excess refrigeration, in an amount which depends on ambient conditions. The cycle is modeled using traditional one-dimensional steady-state thermodynamics, with state-of-the-art polytropic efficiencies and pressure drops for the turbo-machinery and heat exchangers, and accurate y correlations for the properties of the LiBr-water mixture and the combustion products. Water produced as a product of combustion is intentionally condensed in the evaporator of the vapor absorption refrigeration system. The mixture properties of air account for the water removal rate. The vapor absorption refrigeration unit is designed to provide sufficient cooling for water extraction. The cycle is shown to operate with a thermal efficiency approaching 58% for a turbine inlet temperature of 1400 °C in addition to producing about 0.45 liters of water per liter of fuel consumed. Also at the above operating condition the ratio of the refrigeration effect to the net work output from the system is equal to 0.8. The ratio of mass of water extracted to the mass of fresh air inlet into the combined cycle is obtained for different values of cycle parameters, namely turbine inlet temperature, recuperator inlet temperature and the low pressure compressor ratio. The maximum value of this ratio is found to be around 0.11. It is found that it is a strong function of the recirculation ratio and it decreased by 22% as the recirculation ratio is decreased by 70%. The thermodynamic impacts of water extraction on the system performance are also discussed. Based on these results, and prior results, which showed that the HPRTE is very compact, it appears that this cycle would be ideally suited for distributed power and vehicle applications, especially ones with associated air conditioning loads.

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