scholarly journals Study of Bypass Ratio Increasing Possibility for Turbofan Engine and Turbofan with Inter Turbine Burner

2019 ◽  
Vol 26 (2) ◽  
pp. 61-68
Author(s):  
Robert Jakubowski
Keyword(s):  
Fuel Consumption ◽  
Energy Input ◽  
Pressure Ratio ◽  
Specific Fuel Consumption ◽  
Additional Energy ◽  
Fast Analysis ◽  
Turbofan Engine ◽  
Turbofan Engines ◽  
Specific Thrust ◽  
Bypass Ratio

Abstract Current trends in the high bypass ratio turbofan engines development are discussed in the beginning of the paper. Based on this, the state of the art in the contemporary turbofan engines is presented and their change in the last decade is briefly summarized. The main scope of the work is the bypass ratio growth analysis. It is discussed for classical turbofan engine scheme. The next step is presentation of reach this goal by application of an additional combustor located between high and low pressure turbines. The numerical model for fast analysis of bypass ratio grows for both engine kinds are presented. Based on it, the numerical simulation of bypass engine increasing is studied. The assumption to carry out this study is a common core engine. For classical turbofan engine bypass ratio grow is compensated by fan pressure ratio reduction. For inter turbine burner turbofan, bypass grown is compensated by additional energy input into the additional combustor. Presented results are plotted and discussed. The main conclusion is drawing that energy input in to the turbofan aero engine should grow when bypass ratio is growing otherwise the energy should be saved by other engine elements (here fan pressure ratio is decreasing). Presented solution of additional energy input in inter turbine burner allow to eliminate this problem. In studied aspect, this solution not allows to improve engine performance. Specific thrust of such engine grows with bypass ratio rise – this is positive, but specific fuel consumption rise too. Classical turbofan reaches lower specific thrust for higher bypass ratio but its specific fuel consumption is lower too. Specific fuel consumption decreasing is one of the goal set for future aero-engines improvements.

scholarly journals Parameterization of a Conventional and Regenerated UHB Turbofan

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Fábio Oliveira ◽  
Francisco Brójo
Keyword(s):  
Fuel Consumption ◽  
First Generation ◽  
Specific Fuel Consumption ◽  
Aircraft Engines ◽  
Turbofan Engine ◽  
Commercial Aviation ◽  
Technological Developments ◽  
Specific Thrust ◽  
Aero Engines ◽  
Bypass Ratio

AbstractThe attempt to improve aircraft engines efficiency resulted in the evolution from turbojets to the first generation low bypass ratio turbofans. Today, high bypass ratio turbofans are the most traditional type of engine in commercial aviation. Following many years of technological developments and improvements, this type of engine has proved to be the most reliable facing the commercial aviation requirements. In search of more efficiency, the engine manufacturers tend to increase the bypass ratio leading to ultra-high bypass ratio (UHB) engines. Increased bypass ratio has clear benefits in terms of propulsion system like reducing the specific fuel consumption. This study is aimed at a parametric analysis of a UHB turbofan engine focused on short haul flights. Two cycle configurations (conventional and regenerated) were studied, and estimated values of their specific fuel consumption (TSFC) and specific thrust (Fs) were determined. Results demonstrate that the regenerated cycle may contribute towards a more economic and friendly aero engines in a higher range of bypass ratio.

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.

Optimizing Separate Exhaust Turbofans for Cruise Specific Fuel Consumption

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
Syed J. Khalid
Keyword(s):  
Fuel Consumption ◽  
Control Algorithm ◽  
Velocity Ratio ◽  
Transmission Efficiency ◽  
Specific Fuel Consumption ◽  
Variable Geometry ◽  
Nozzle Throat ◽  
Propulsive Efficiency ◽  
Turbofan Engines ◽  
Bypass Ratio

Cruise specific fuel consumption (SFC) of turbofan engines is a key metric for increasing airline profitability and for reducing CO2 emissions. Although increasing design bypass ratio (BPR) of separate exhaust turbofan configurations improves cruise SFC, further improvements can be obtained with online control actuated variable geometry modulations of bypass nozzle throat area, core nozzle throat area, and compressor variable vanes (CVV/CVG). The scope of this paper is to show only the benefits possible, and the process used in determining those benefits, and not to suggest any particular control algorithm for searching the best combination of the control effectors. A parametric cycle study indicated that the effector modulations could increase the cruise BPR, core efficiency, transmission efficiency, propulsive efficiency, and ideal velocity ratio resulting in a cruise SFC improvement of as much as 2.6% depending upon the engine configuration. The changes in these metrics with control effector variations will be presented. Scheduling of CVV is already possible in legacy digital controls; perturbation to this schedule and modulation of nozzle areas should be explored in light of the low bandwidth requirements at steady-state cruise conditions.

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.

Fundamental Differences Between Conventional and Geared Turbofans

2009 ◽  
Author(s):  
Joachim Kurzke
Keyword(s):  
Fuel Consumption ◽  
Real Option ◽  
Pressure Ratio ◽  
Thermodynamic Cycle ◽  
Specific Fuel Consumption ◽  
Thermodynamic Efficiency ◽  
Aircraft Engines ◽  
Direct Drive ◽  
Significant Difference ◽  
Bypass Ratio

The potential for improving the thermodynamic efficiency of aircraft engines is limited because the aerodynamic quality of the turbomachines has already achieved a very high level. While in the past increasing burner exit temperature did contribute to better cycle efficiency, this is no longer the case with today’s temperatures in the range of 1900...2000K. Increasing the cycle pressure ratio above 40 will yield only a small fuel consumption benefit. Therefore the only way to improve the fuel efficiency of aircraft engines significantly is to increase bypass ratio — which yields higher propulsive efficiency. A purely thermodynamic cycle study shows that specific fuel consumption decreases continuously with increasing bypass ratio. However, thermodynamics alone is a too simplistic view of the problem. A conventional direct drive turbofan of bypass ratio 6 looks very different to an engine with bypass ratio 10. Increasing bypass ratio above 10 makes it attractive to design an engine with a gearbox to separate the fan speed from the other low pressure components. Different rules apply for optimizing turbofans of conventional designs and those with a gearbox. This paper describes various criteria to be considered for optimizing the respective engines and their components. For illustrating the main differences between conventional and geared turbofans it is assumed that an existing core of medium pressure ratio with a two stage high pressure turbine is to be used. The design of the engines is done for takeoff rating because this is the mechanically most challenging condition. For each engine the flow annulus is examined and stress calculations for the disks are performed. The result of the integrated aero-thermodynamic and mechanical study allows a comparison of the fundamental differences between conventional and geared turbofans. At the same bypass ratio there will be no significant difference in specific fuel consumption between the alternative designs. The main difference is in the parts count which is much lower for the geared turbofan than for the conventional engine. However, these parts will be mechanically much more challenging than those of a conventional turbofan. If the bypass ratio is increased significantly above 10, then the geared turbofan becomes more and more attractive and the conventional turbofan design is no longer a real option. The maximum practical bypass ratio for ducted fans depends on the nacelle drag and how the installation problems can be solved.

scholarly journals ОСОБЕННОСТИ РАСЧЕТА И РЕГУЛИРОВАНИЯ ДВУХКОНТУРНОГО ТУРБОРЕАКТИВНОГО ДВИГАТЕЛЯ С ФОРСАЖНОЙ КАМЕРОЙ СГОРАНИЯ В НАРУЖНОМ КОНТУРЕ НА ПРЯМОТОЧНЫХ РЕЖИМАХ РАБОТЫ

2020 ◽  
pp. 15-23
Author(s):  
Олег Владимирович Кислов ◽  
Михаил Анатольевич Шевченко
Keyword(s):  
Mathematical Model ◽  
Fuel Consumption ◽  
Control Program ◽  
Critical Section ◽  
Specific Fuel Consumption ◽  
Outlet Section ◽  
Nozzle Outlet ◽  
Turbofan Engine ◽  
Turbofan Engines ◽  
Ramjet Engines

A promising direction in aviation is the creation of anaircraft for supersonic cruise speeds (Mach 3...4). It is known that ramjet engines are more preferable for Mach numbers larger 3. However, they do not have starting thrust and uneconomical at subsonic flight speeds. At the same time, at subsonic flight speeds, turbofan engines are the most expedient. The combination of the positive properties of turbofan engines at subsonic speeds and a ramjet engines at supersonic speeds is possible by using duct-burning turbofan engine, which can operate at the ramjet mode with the blocked gas turbine duct at supersonic flight conditions. At this mode, duct-burning turbofan engine turns into ramjet engine, which, however, has special features due to the presence of fan in front of the combustion chamber, which operates in turbine mode or in zero power mode and also because of the outlet jet, which has annular shape, flows out from the duct causes the appearance of bottom drag. The presence of bottom drag requires both the development of a mathematical model for its calculation and taking into account its influence on the choice of the control law for the nozzle outlet area. The article presents a mathematical model of the working process of duct-burning turbofan engine at ramjet mode, taking into account the presence of fan in the flow path and bottom drug. Using the developed mathematical model, the regularities of changes in the internal and effective thrust, as well as the specific fuel consumption, depending on the relative fuel consumption and the critical section of the nozzle at a given altitude and flight speed are established. The critical section of the nozzle is the main regulating factor, and the relative fuel consumption is related to the main regulating factor - the fuel consumption. These patterns are useful for choosing a control program.There is such a combination of regulating factors whichprovides two extremes in the regularities of trust and specific fuel consumption changes: the mode of minimum specific fuel consumption and the mode of maximum thrust. In addition, the influence of gas underexpansion in the nozzle on the thrust-economic parameters of the engine and the required area of the nozzle outlet section were estimated. The obtained regularities are advisable to use when engine control program is chosen.

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.

Feasibility Study of Some Novel Concepts for High Bypass Ratio Turbofan Engines

2009 ◽  
Author(s):  
Dipanjay Dewanji ◽  
G. Arvind Rao ◽  
Jos van Buijtenen
Keyword(s):  
Fuel Consumption ◽  
Substantial Reduction ◽  
Substantial Improvement ◽  
Fuel Price ◽  
Turbofan Engine ◽  
Turbofan Engines ◽  
Fuel Flow ◽  
Blade Tip ◽  
Fan Blade ◽  
Bypass Ratio

The soaring fuel price and the burgeoning environmental concerns have compelled global research towards cleaner engines, aimed at substantial reduction in emission, noise and fuel consumption. In this context, the present research investigates the feasibility of some novel engine concepts, namely Geared Turbofan and Intercooled Recuperated Turbofan concepts, by hypothetically applying them into an existing state-of-the-art high bypass ratio engine. This paper made an effort to estimate the effects on the baseline engine performances due to the introduction of these two concepts into it. By performing steady state simulations, it was found that the incorporation of the Geared Turbofan concept into the existing Turbofan engine caused a significant reduction in thrust specific fuel consumption, engine weight, and fan blade tip speed. However, when simulations were also carried out by incorporating the Intercooler and Recuperator concept in the baseline turbofan engine, it did not demonstrate any substantial improvement in fuel consumption. It was observed that the fuel flow rate was influenced to a large extent by heat exchanger’s effectiveness and the pressure drop within it. The overall engine weight was also found to get increased due to the inclusion of massive heat exchangers necessary for the system.

Optimizing Separate Exhaust Turbofans for Cruise Specific Fuel Consumption

2016 ◽  
Author(s):  
Syed Khalid
Keyword(s):  
Fuel Consumption ◽  
Control Algorithm ◽  
Velocity Ratio ◽  
Transmission Efficiency ◽  
Specific Fuel Consumption ◽  
Variable Geometry ◽  
Nozzle Throat ◽  
Propulsive Efficiency ◽  
Turbofan Engines ◽  
Bypass Ratio

Cruise specific fuel consumption (SFC) of turbofan engines is a key metric for increasing airline profitability and for reducing CO2 emissions. Although increasing design bypass ratio (BPR) of separate exhaust turbofan configurations improves cruise SFC, further improvements can be obtained with control actuated variable geometry modulations of core nozzle throat area, bypass nozzle throat area, and compressor variable vanes (CVV). The scope of this paper is to show only the benefits possible, and the process used in determining those benefits, and not to suggest any particular control algorithm for searching the best combination of the control effectors. A parametric cycle study indicated that the effector modulations could increase the cruise BPR, core efficiency, transmission efficiency, propulsive efficiency, and ideal velocity ratio resulting in a cruise SFC improvement of as much as 2.6% depending upon the engine configuration. The changes in these metrics with control effector variations will be presented. Modulation of CVV is already possible in legacy digital controls, and modulation of nozzle areas should be explored in light of the low bandwidth requirements at steady-state cruise conditions.

Altitude Engine Test of a Turbofan Exhaust Gas Mixer to Conserve Fuel

1977 ◽  
Vol 99 (4) ◽  
pp. 645-649 ◽  
Author(s):  
R. R. Cullom ◽  
R. L. Johnsen
Keyword(s):  
Fuel Consumption ◽  
Specific Fuel Consumption ◽  
Exhaust Gas ◽  
Engine Test ◽  
Turbofan Engine ◽  
Test Conditions ◽  
Total Temperature ◽  
Internal Mixer ◽  
Bypass Ratio ◽  
Fuel Consumption Improvement

A comparison of the specific fuel consumption was made with and without an internal mixer installed in a low bypass ratio, confluent flow turbofan engine. Tests were conducted at several Mach numbers and altitudes for core to fan stream total temperature ratios of 2.0 and 2.5 and mixing lengths of L/D = 0.95 and 1.74. For these test conditions, the specific fuel consumption improvement varied from 2.5 to 4.0 percent.

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