Showing papers on "Turbofan published in 2016"

Gas turbine engine with axial movable fan variable area nozzle

Abstract: A turbofan engine includes a fan variable area nozzle includes having a first fan nacelle section and a second fan nacelle section movably mounted relative the first fan nacelle section. The second fan nacelle section axially slides aftward relative to the fixed first fan nacelle section to change the effective area of the fan nozzle exit area.

Parallel Hybrid Gas-Electric Geared Turbofan Engine Conceptual Design and Benefits Analysis

Abstract: The conceptual design of a parallel gas-electric hybrid propulsion system for a conventional single aisle twin engine tube and wing vehicle has been developed. The study baseline vehicle and engine technology are discussed, followed by results of the hybrid propulsion system sizing and performance analysis. The weights analysis for the electric energy storage & conversion system and thermal management system is described. Finally, the potential system benefits are assessed.

Fundamentals of Aircraft and Rocket Propulsion

Abstract: This book provides a comprehensive basics-to-advanced course in an aero-thermal science vital to the design of engines for either type of craft. The text classifies engines powering aircraft and single/multi-stage rockets, and derives performance parameters for both from basic aerodynamics and thermodynamics laws. Each type of engine is analyzed for optimum performance goals, and mission-appropriate engines selection is explained. Fundamentals of Aircraft and Rocket Propulsion provides information about and analyses of: thermodynamic cycles of shaft engines (piston, turboprop, turboshaft and propfan); jet engines (pulsejet, pulse detonation engine, ramjet, scramjet, turbojet and turbofan); chemical and non-chemical rocket engines; conceptual design of modular rocket engines (combustor, nozzle and turbopumps); and conceptual design of different modules of aero-engines in their design and off-design state. Aimed at graduate and final-year undergraduate students, this textbook provides a thorough grounding in the history and classification of both aircraft and rocket engines, important design features of all the engines detailed, and particular consideration of special aircraft such as unmanned aerial and short/vertical takeoff and landing aircraft. End-of-chapter exercises make this a valuable student resource, and the provision of a downloadable solutions manual will be of further benefit for course instructors

Demonstration of a Regulatory Method for Aircraft Engine Nonvolatile PM Emissions Measurements with Conventional and Isoparaffinic Kerosene Fuels

Abstract: The aviation industry is exploring the economic viability and environmental sustainability of the use of alternative fuels to power aircraft main engines and auxiliary power units. The International Civil Aviation Organization is also developing a regulatory standard for aircraft engine nonvolatile particulate matter (nvPM) emissions to meet the growing public demand for improvement in air quality. This study compared the nvPM emissions in the exhaust stream of a small (<26.7 kN thrust) mixed turbofan aircraft engine burning a conventional Jet A fuel as well as a Sasol isoparaffinic kerosene (IPK) fuel derived from coal, using a standardized sampling and measurement system. The goal of the study was to demonstrate the regulatory system on a small mixed turbofan engine and to assess the suitability and limitations of using such systems for turbofan engines burning fuels with different fuel properties. Significant reductions in both nvPM number- and mass-based emission indices were observed with the IPK fue...

Perceived Noise Analysis for Offset Jets Applied to Commercial Supersonic Aircraft

Abstract: A systems analysis was performed with experimental jet noise data, engine/aircraft performance codes and aircraft noise prediction codes to assess takeoff noise levels and mission range for conceptual supersonic commercial aircraft. A parametric study was done to identify viable engine cycles that meet NASA's N+2 goals for noise and performance. Model scale data from offset jets were used as input to the aircraft noise prediction code to determine the expected sound levels for the lateral certification point where jet noise dominates over all other noise sources. The noise predictions were used to determine the optimal orientation of the offset nozzles to minimize the noise at the lateral microphone location. An alternative takeoff procedure called "programmed lapse rate" was evaluated for noise reduction benefits. Results show there are two types of engines that provide acceptable mission range performance; one is a conventional mixed-flow turbofan and the other is a three-stream variable-cycle engine. Separate flow offset nozzles reduce the noise directed toward the thicker side of the outer flow stream, but have less benefit as the core nozzle pressure ratio is reduced. At the systems level for a three-engine N+2 aircraft with full throttle takeoff, there is a 1.4 EPNdB margin to Chapter 3 noise regulations predicted for the lateral certification point (assuming jet noise dominates). With a 10% reduction in thrust just after clearing the runway, the margin increases to 5.5 EPNdB. Margins to Chapter 4 and Chapter 14 levels will depend on the cumulative split between the three certification points, but it appears that low specific thrust engines with a 10% reduction in thrust (programmed lapse rate) can come close to meeting Chapter 14 noise levels. Further noise reduction is possible with engine oversizing and derated takeoff, but more detailed mission studies are needed to investigate the range impacts as well as the practical limits for safety and takeoff regulations.

Advanced Control Considerations for Turbofan Engine Design

Abstract: This paper covers the application of a model-based engine control (MBEC) methodology featuring a self tuning on-board model for an aircraft turbofan engine simulation. The nonlinear engine model is capable of modeling realistic engine performance, allowing for a verification of the advanced control methodology over a wide range of operating points and life cycle conditions. The on-board model is a piece-wise linear model derived from the nonlinear engine model and updated using an optimal tuner Kalman Filter estimation routine, which enables the on-board model to self-tune to account for engine performance variations. MBEC is used here to show how advanced control architectures can improve efficiency during the design phase of a turbofan engine by reducing conservative operability margins. The operability margins that can be reduced, such as stall margin, can expand the engine design space and offer potential for efficiency improvements. Application of MBEC architecture to a nonlinear engine simulation is shown to reduce the thrust specific fuel consumption by approximately 1% over the baseline design, while maintaining safe operation of the engine across the flight envelope.

Geared turbofan with independent flexible ring gears and oil collectors

Abstract: A geared turbofan engine includes a fan rotatable about an engine axis. A compressor section compresses air and delivers the compressed air to a combustor where the compressed air is mixed with fuel and ignited to drive a turbine section that in turn drives the fan and the compressor section. A gear system is driven by the turbine section for driving the fan at a speed different than the turbine section. The gear system includes a carrier attached to a fan shaft. A plurality of planet gears are supported within the carrier. Each of the plurality of planet gears includes a first row of gear teeth and a second row of gear teeth supported within the carrier. A sun gear is driven by a turbine section. The sun gear is in driving engagement with the plurality of planet gears. At least two separate ring gears circumscribe the plurality of planet gears. Each of the at least two ring gears are supported by a respective flexible ring gear mount that enables movement relative to an engine static structure. A fan drive gear system for a gas turbine engine is also disclosed.

System Noise Prediction of the DGEN 380 Turbofan Engine

Abstract: The DGEN 380 is a small, separate-flow, geared turbofan. Its manufacturer, Price Induction, is promoting it for a small twinjet application in the emerging personal light jet market. Smaller, and producing less thrust than other entries in the industry, Price Induction is seeking to apply the engine to a 4- to 5-place twinjet designed to compete in an area currently dominated by propeller-driven airplanes. NASA is considering purchasing a DGEN 380 turbofan to test new propulsion noise reduction technologies in a relevant engine environment. To explore this possibility, NASA and Price Induction have signed a Space Act Agreement and have agreed to cooperate on engine acoustic testing. Static acoustic measurements of the engine were made by NASA researchers during July, 2014 at the Glenn Research Center. In the event that a DGEN turbofan becomes a NASA noise technology research testbed, it is in the interest of NASA to develop procedures to evaluate engine system noise metrics. This report documents the procedures used to project the DGEN static noise measurements to flight conditions and the prediction of system noise of a notional airplane powered by twin DGEN engines.

Turbofan Broadband Noise Prediction using the Lattice Boltzmann Method

Abstract: The present work describes a numerical reproduction of the 22-in source diagnostic test fan rig of the NASA Glenn Research Center. Numerical flow simulations are performed for three different rotor...

Loss and Deviation in Windmilling Fans

Abstract: For an unpowered turbofan in flight, the airflow through the engine causes the fan to freewheel This paper considers the flow field through a fan operating in this mode, with emphasis on the effects of blade row losses and deviation A control volume analysis is used to show that windmilling fans operate at a fixed flow coefficient which depends on the blade metal and deviation angles, while the blade row losses are shown to determine the fan mass flow rate Experimental and numerical results are used to understand how the loss and deviation differ from the design condition due to the flow physics encountered at windmill Results are presented from an experimental study of a windmilling low-speed rig fan, including detailed area traverses downstream of the rotor and stator Three-dimensional computational fluid dynamics (CFD) calculations of the fan rig and a representative transonic fan windmilling at a cruise flight condition have also been completed The rig test results confirm that in the windmilling condition, the flow through the fan stator separates from the pressure surface over most of the span This generates high loss, and the resulting blockage changes the rotor work profile leading to modified rotational speed In the engine fan rotor, a vortex forms at the pressure surface near the tip and further loss results from a hub separation caused by blockage from the downstream core and splitter

Ultra Low Emission Technology Innovations for Mid-century Aircraft Turbine Engines

Abstract: Commercial transport fuel efficiency has improved dramatically since the early 1950s. In the coming decades the ubiquitous turbofan powered tube and wing aircraft configuration will be challenged by diminishing returns on investment with regards to fuel efficiency. From the engine perspective two routes to radically improved fuel efficiency are being explored; ultra-efficient low pressure systems and ultra-efficient core concepts. The first route is characterized by the development of geared and open rotor engine architectures but also configurations where potential synergies between engine and aircraft installations are exploited. For the second route, disruptive technologies such as intercooling, intercooling and recuperation, constant volume combustion as well as novel high temperature materials for ultra-high pressure ratio engines are being considered. This paper describes a recently launched European research effort to explore and develop synergistic combinations of radical technologies to TRL 2. The combinations are integrated into optimized engine concepts promising to deliver ultra-low emission engines. The paper discusses a structured technique to combine disruptive technologies and proposes a simple means to quantitatively screen engine concepts at an early stage of analysis. An evaluation platform for multidisciplinary optimization and scenario evaluation of radical engine concepts is outlined.

Effect of heat leakage on the performance of a twin-spool turbofan engine

Abstract: The effect of heat leakage from a twin-spool turbofan engine to the ambient air on the performance of the engine for a commercial aircraft is investigated. Effects of heat leakage on the variation of the performance indicators of coefficient of ecological performance, overall efficiency, exergy destruction factor, thrust specific fuel consumption and entropy generation rate with respect to the design parameters of compressor and fan pressure ratios, by-pass ratio and turbine inlet temperature are investigated numerically. The main findings are as follows: (i) Effect of heat leakage from the combustion chamber to the by-pass air on the coefficient of ecological performance, exergy destruction factor and entropy generation rate is considerably large when compared to that on the other performance indicators especially for small values of design parameters except for turbine inlet temperature. (ii) Effect of heat leakage on the performance indicators is significant for small values of turbine inlet temperature and large values of the other design parameters.

Modeling of Highly Instrumented Honeywell Turbofan Engine Tested with Ice Crystal Ingestion in the NASA Propulsion System Laboratory

Abstract: The Propulsion Systems Laboratory (PSL), an altitude test facility at NASA Glenn Research Center, has been used to test a highly instrumented turbine engine at simulated altitude operating conditions. This is a continuation of the PSL testing that successfully duplicated the icing events that were experienced in a previous engine (serial LF01) during flight through ice crystal clouds, which was the first turbofan engine tested in PSL. This second model of the ALF502R-5A serial number LF11 is a highly instrumented version of the previous engine. The PSL facility provides a continuous cloud of ice crystals with controlled characteristics of size and concentration, which are ingested by the engine during operation at simulated altitudes. Several of the previous operating points tested in the LF01 engine were duplicated to confirm repeatability in LF11. The instrumentation included video cameras to visually illustrate the accretion of ice in the low pressure compressor (LPC) exit guide vane region in order to confirm the ice accretion, which was suspected during the testing of the LF01. Traditional instrumentation included static pressure taps in the low pressure compressor inner and outer flow path walls, as well as total pressure and temperature rakes in the low pressure compressor region. The test data was utilized to determine the losses and blockages due to accretion in the exit guide vane region of the LPC. Multiple data points were analyzed with the Honeywell Customer Deck. A full engine roll back point was modeled with the Numerical Propulsion System Simulation (NPSS) code. The mean line compressor flow analysis code with ice crystal modeling was utilized to estimate the parameters that indicate the risk of accretion, as well as to estimate the degree of blockage and losses caused by accretion during a full engine roll back point. The analysis provided additional validation of the icing risk parameters within the LPC, as well as the creation of models for estimating the rates of blockage growth and losses.

On-Board Real-Time Optimization Control for Turbo-Fan Engine Life Extending

Abstract: Abstract A real-time optimization control method is proposed to extend turbo-fan engine service life. This real-time optimization control is based on an on-board engine mode, which is devised by a MRR-LSSVR (multi-input multi-output recursive reduced least squares support vector regression method). To solve the optimization problem, a FSQP (feasible sequential quadratic programming) algorithm is utilized. The thermal mechanical fatigue is taken into account during the optimization process. Furthermore, to describe the engine life decaying, a thermal mechanical fatigue model of engine acceleration process is established. The optimization objective function not only contains the sub-item which can get fast response of the engine, but also concludes the sub-item of the total mechanical strain range which has positive relationship to engine fatigue life. Finally, the simulations of the conventional optimization control which just consider engine acceleration performance or the proposed optimization method have been conducted. The simulations demonstrate that the time of the two control methods from idle to 99.5 % of the maximum power are equal. However, the engine life using the proposed optimization method could be surprisingly increased by 36.17 % compared with that using conventional optimization control.

Aircraft Performance for Open Air Traffic Simulations

Abstract: The BlueSky Open Air Traffic Simulator developed by the Control \& Simulation section of TU Delft aims at supporting research for analysing Air Traffic Management concepts by providing an open source simulation platform. The goal of this study was to complement BlueSky with aircraft performance models in order to enable performance-related Air Traffic Management studies. The aircraft performance model developed within this work consists of a kinetic Flight Dynamics Model, which stores the required performance characteristics in a database with type-specific aircraft and engine coefficients. Currently, sixteen commercial turbofan and turboprop aircraft from different range and weight categories are represented. To evaluate the quality of the aircraft performance model, its outputs were compared to results from literature as well as from real flights. It was found that the applied methodologies for the determination of aircraft performance accurately model high-speed drag polars as well as fuel consumption for cruising and taxiing aircraft. The fuel consumption model of climbing and descending aircraft, however, leaves room for improvement. Possible strategies for obtaining a more precise estimation of fuel burn over the entire flight are recommended based on the results of this study. With this work, the BlueSky Open Air Traffic Simulator considers individual aircraft performance. This is an important step in the creation of an open simulation platform for Air Traffic Management research.

Assessment of Engine and Vehicle Performance Using Integrated Hybrid-Electric Propulsion Models

Abstract: NASA is actively funding research into advanced, unconventional aircraft and engine architectures to achieve drastic reductions in vehicle fuel burn, noise, and emissions. One such concept is being explored by The Boeing Company, the General Electric Company, Virginia Polytechnic Institute and State University, and the Georgia Institute of Technology under the Subsonic Ultra Green Aircraft Research Project. A major cornerstone of this research is evaluating the potential performance benefits that can be attributed to using hybrid-electric propulsion. Hybrid-electric propulsion in this context involves a non-Brayton power generation or storage source, such as a battery or a fuel cell that can be used to provide additional propulsive energy to a conventional Brayton-cycle-powered turbofan engine. This research constructs an integrated Numerical Propulsion System Simulation hybrid-electric propulsion model capable of predicting hybrid-electric engine performance throughout the operational envelope. The syste...

Optimal design and installation of ultra high bypass ratio turbofan nacelle

Abstract: The paper is devoted to the problem of designing and optimizing the nacelle of turbojet bypass engine with high bypass ratio and high thrust. An optimization algorithm EGO based on development of surrogate models and the method for maximizing the probability of improving the objective function has been used. The designing methodology has been based on the numerical solution of the Reynolds equations system. Spalart-Allmaras turbulence model has been chosen for RANS closure. The effective thrust losses has been uses as an objective function in optimizing the engine nacelle. As a result of optimization, effective thrust has been increased by 1.5 %. The Blended wing body aircraft configuration has been studied as a possible application. Two variants of the engine layout arrangement have been considered. It has been shown that the power plant changes the pressure distribution on the aircraft surface. It results in essential diminishing the configuration lift-drag ratio.

Estimation of Performance Airspeeds for High-Bypass Turbofans Equipped Transport-Category Airplanes

Abstract: Conventional Mach-independent subsonic drag polar does not replicate the real airplane drag characteristics exactly and especially not in the drag-divergence region due to shock-induced transonic wave drag. High-bypass turbofan thrust is a complicated function of many parameters that eludes accurate predictions for the entire operating envelope and must be experimentally verified. Fuel laws are also complicated functions of many parameters which make optimization and economic analysis difficult and uncertain in the conceptual design phase. Nevertheless, mathematical models and predictions have its important place in aircraft development, design, and optimization. In this work, airspeed-dependent turbofan thrust and the new fuel-law model were used in combination with an airplane polynomial drag model to estimate important performance speeds. Except for the airframe-only dependent control airspeeds, all performance speeds are airframepowerplant dependent. In all analytical considerations one ends up with polynomials of the 4 order that have no closed-form solutions. A real positive-root seeking numerical procedure based on the family of Newton-Raphson methods was used to extract performance airspeeds for variable in-flight weights and altitudes in the ISA troposphere. Extensive testing of the accuracy and convergence of the Newton-Raphson nonlinear equation solvers was conducted before performance speed calculations. A fictitious long-range wide-body transport-category airplane was modeled in combination with a pair of high-bypass and ultra-high bypass ratio flat-rated turbofans. Procedure employed here can be easily extended to cases when fitted, measured drag and thrust data is given in arbitrary polynomial forms. Sensitivity analysis is performed on minimum-drag airspeed and maximum aerodynamic efficiency. Transonic wave drag considerations are introduced.

Micro-Turbojet to Turbofan Conversion Via Continuously Variable Transmission: Thermodynamic Performance Study

Abstract: In this study, the viability, performance, and characteristics of a turbojet-to-turbofan conversion through the use of a continuously variable transmission (CVT) are investigated. By an in-house thermodynamic simulation code, the performance of the simple cycle turbojet, a direct shaft joined turbofan, and a CVT coupled turbofan with variable bypass are contrasted. The baseline turbojet and turbofan findings are validated against a commercial software. The comparison indicates high quantitative agreement.Analyzing the results of the turbofan engine equipped with a variable bypass and CVT, it is observed that both the thrust and the efficiency are increased. The augmented thrust is observed to be an artifact of enhanced component matching and wider operational range introduced by variable bypass capability. On the other hand, the introduction of CVT contributes to the reduction in fuel consumption. Therefore, the current research suggests that adaptation of a micro-turbojet into a variable cycle micro turbofan will greatly improve the performance and efficiency of existing engines, in addition to providing a pathway towards extended use in various applications.Copyright © 2016 by ASME

Design point analysis of the turbofan-driven turboelectric distributed propulsion system with boundary layer ingestion

Abstract: The performance benefits of boundary layer ingestion in the case of air vehicles powered by distributed propulsors have been documented and explored extensively by previous study. However, the incr...

Thrust force generation device and aircraft

Abstract: This thrust force generation device (1) is provided with: a turbo fan engine unit (2) that is provided with a generator (7) for generating power using a rotation force of a drive shaft, and drives a fan (5) provided on the drive shaft using gas produced by burning fuel; a motor driving fan unit (3) that is provided with a motor (9) driven by power supplied from the generator (7), that is provided in parallel with the turbo fan engine unit (2), and that drives a fan (8) by using the motor (9); and a conducting unit (20) that connects the generator (7) to the motor (9), and supplies the power generated by the generator (7) to the motor (9). The turbo fan engine unit (2) and the motor driving fan unit (3) are integrated with each other, and the conducting unit (20) is disposed between the turbo fan engine unit (2) and the motor driving fan unit (3).

Geared turbofan with low spool power extraction

Abstract: A geared turbofan engine includes a first spool including a first compressor and a first turbine. The first compressor is immediately before a combustor and the first turbine is immediately after the combustor. A second spool includes at least a second turbine disposed axially aft of the first turbine. A first tower shaft is engaged to drive the high speed spool. A second tower shaft engaged to be driven by the second spool. A starter is engaged to drive the first tower shaft. An accessory gear box is driven by the second tower shaft. A first clutch is disposed between the first tower shaft and the starter. The first clutch is configured to enable the starter to drive the high speed spool. A second clutch is disposed between the second tower shaft and the accessory gear box, the second clutch configured to enable the second spool to drive the accessory gear box. A gas turbine engine and a method of operating a gas turbine engine are also disclosed.

NASA Electric Aircraft Test Bed (NEAT) Development Plan - Design, Fabrication, Installation

Abstract: As large airline companies compete to reduce emissions, fuel, noise, and maintenance costs, it is expected that more of their aircraft systems will shift from using turbofan propulsion, pneumatic bleed power, and hydraulic actuation, to instead using electrical motor propulsion, generator power, and electrical actuation. This requires new flight-weight and flight-efficient powertrain components, fault tolerant power management, and electromagnetic interference mitigation technologies. Moreover, initial studies indicate some combination of ambient and cryogenic thermal management and relatively high bus voltages when compared to state of practice will be required to achieve a net system benefit. Developing all these powertrain technologies within a realistic aircraft architectural geometry and under realistic operational conditions requires a unique electric aircraft testbed. This report will summarize existing testbed capabilities located in the U.S. and details the development of a unique complementary testbed that industry and government can utilize to further mature electric aircraft technologies.

Off-set geared turbofan engine

Abstract: A turbofan gas turbine engine includes a first shaft for mounting and rotation of a fan, the first shaft including a single stage internal gear mounted on the first shaft aft of the fan. The turbofan engine further includes a second shaft for mounting and rotation of a low pressure compressor and a low pressure turbine, the second shaft including a pinion gear mounted thereon forward of the low pressure compressor. The pinion gear meshes with the single stage internal gear to drive the first shaft and fan. The second shaft is parallel and off-set from the first shaft.