Conventional Turbofan Research Articles

Multi-variable anti-disturbance controller with state-dependent switching law for adaptive cycle engine

Compared with the conventional turbofan engine, the adaptive cycle engine (ACE) has more extensive flight envelope and the more types and number of adjustable components. While the performance of each mission profile is improved adaptively, the controller design of profile switching process will face strong flight condition disturbance and internal uncertainty. The traditional control system's single loop controller and discrete switching method of control parameters are to some extent difficult to meet the adaptive and robustness requirements of ACE. Thus, this paper proposed a multi-variable decoupling anti-disturbance controller for ACE based on the results of flight envelope partitioning with similar distances, embedded a state-dependent switching law. By analyzing the impact of inlet disturbances, internal actuator actuation, and random degradation of component performance on different switching laws, the adjust time and overshoot of the controller with state-dependent switching law proposed in this paper are reduced by an average of about 11.91 % and about 9.98 %, and the average thrust linearity and robustness has increased by about 0.096 % and 20.02 %. Finally, the reliability and feasibility of the control system were verified based on a hydraulic driven semi-physical experimental platform, providing reference for more complex and dynamic engine operation control in the future.

Holistic performance evaluation of a turbofan featuring pressure gain combustion for a short-range mission

Aviation is at the center of public interest because of its environmental impact, such as noise and pollutant emissions. Evolutionary technologies are not expected to be sufficient to contribute significantly to the 2050 CO2 emissions reduction targets. This could change if the constant pressure combustion of the Joule cycle could be replaced with a constant volume combustion (pressure gain combustion, PGC). However, PGC comes with a major drawback of a periodic, highly unsteady process that potentially reduces the stability and efficiency of the adjacent compressor and turbine. Furthermore, changes to the secondary air system (SAS) are required since the driving force of SAS stems from the pressure loss in the conventional combustor. Despite the lasting prevalence of pressure gain combustion, there is no whole system analysis taking into account not only the beneficial aspects of PGC, but also the detrimental effects on the SAS and turbo components. To close that gap, a zero-dimensional whole engine model is created. That model accounts for the individual effects of PGC. A comprehensive design methodology identifies optimum engine specifications for a short-range mission. By comparing the results of the PGC turbofan to a conventional turbofan, an SFC improvement of 3.3% was identified.

A Comparative Performance Analysis of the Novel TurboAux Engine with a Turbojet Engine, and a Low-Bypass Ratio Turbofan Engine with an Afterburner

Presented herein is a comparative performance analysis of a novel turbofan engine with an auxiliary combustion chamber, nicknamed the TurboAux engine, against a turbojet engine, and a low bypass ratio turbofan engine with an afterburner is presented. The TurboAux engine is an adaption of the low-bypass ratio turbofan engine, but with secondary combustion in an auxiliary bypass annular combustion chamber for thrust augmentation. The TurboAux engine is envisioned with the desire to facilitate clean secondary burning of fuel at temperatures higher than in the main combustion chamber with air exiting the low-pressure compressor. The comparative study starts by analyzing the turbojet engine and its performance with and without an afterburner segment attached. In parallel, the conventional turbofan and its mixing counterpart are analyzed, also with and without an afterburner segment. A simple optimization analysis of a conventional turbofan is performed to identify optimal ‘fan’ pressure ratios for a series of low-bypass ratios (0.1 to 1.5). The optimal fan pressure ratios and their corresponding bypass ratios are adapted to demonstrate the comparative performance of the varying configurations of the TurboAux engine. The formulation and results are an attempt to make a case for charter aircrafts and efficient close-air-support aircrafts. The results yielded increased performance in thrust augmentation, but at the cost of a spike in fuel consumption. This trade-off requires more in-depth investigation to further ascertain the TurboAux’s utility.

Investigation of the requirements for the selection of materials for high pressure Turbine blades of conventional turbojet engines

The material selection method is critically evaluated to enable high pressure (HP) turbine blades to deal with in-service damaging phenomena such as creep, low cycle fatigue and high cycle fatigue, oxidation and corrosion. The material selection method is analyzed in order to improve the service life of the aero engine. To increase the turbine inlet temperature, HP turbine blades need improved creep and fatigue resistance. more quality. By the typical working condition of HP turbine blade, using CES Edu Pack (CES) material selection software was used to select suitable materials for HP turbine blade material. Nickel based alloys are selected for HP turbine blades, such as Nickel-Cr-Co-Mo superalloy.

Towards predicting noise-power-distance curves for propeller and rotor powered aircraft

Propeller and rotor based propulsion systems are the dominating choice of power delivery system in the upcoming Urban Air Mobility market. Fully electric air-taxis (car sized vehicles with Vertical Take-off and Landing, VTOL, capabilities) concepts are using the benefits of the scalable properties of electric motors to distribute propulsor units all over the airframe. The large variety of concepts and configurations of these vehicles poses a serious issue in predicting noise generated on the ground. The need for a high-level model to aid in acoustic decision making is evident. Through the demonstrated methodology of computationally deriving Noise - Power - Distance curves for conventional turbo fan aircraft, this paper delivers the capability of dealing with propeller propulsion systems and the associated propeller tonal noise sources to generate the NPDs and therefore noise exposure maps. The aims can be broken down into two objectives: a) demonstrate the capabilities of the proposed propeller harmonics noise scaling laws to calculate noise variation from a baseline scenario and b) incorporate the scaling components into the larger capability of producing noise exposure contours, by the means of computationally deriving NPD curves for propeller powered aircraft. Preliminary NPD curves for General Aviation sized propeller power aircraft are generated and discussed.

Numerical modeling on installed performance of turbofan engine with inlet ejector

In order to consider the capacity of aircraft infrared stealth, a turbofan engine with inlet ejector nozzle is derived for flight mission analysis. The turbofan engine is equipped with an auxiliary inlet door that utilizes the inlet bypass flow to ejector the nozzle and increase the engine installed thrust. Firstly, on the basis of the quasi one-dimensional flow theory, the ejector nozzle model is established to analyze its performance effect on the engine. Secondly, a backward infrared radiation intensity prediction method for exhaust system is proposed. Finally, during the analysis of engine installed performance, the supersonic inlet drag is considered. The numerical simulations results indicated that, compared with the conventional turbofan engine, the turbofan engine with inlet ejector not only reduces the infrared radiation and specific fuel consumption, but also increases the engine installed thrust, which improves the engine performance significantly.

Bioinspired Propulsion Design Concepts for Unmanned Aerial Vehicles (Drones)

This study aimed to develop a propulsion design concept for smart drones (UAVs - Unmanned Aerial Vehicles) mimicking a bacterial flagellar motor that can be found in many bacterial cells. A preliminary propulsion design concept was developed based on using the conventional turbojet without the turbine to run the compressor following the flagellar motor organization. Design analysis through analytical and computations was carried out in terms of power/thrust generated as part of various design variables for the design concept considered.

Effect of a fuselage boundary layer ingesting propulsor on airframe forces and moments

The aim of this research project was to investigate the benefits of hybrid-distributed propulsion and boundary layer ingestion applied to an airliner similar in size, range and cruise velocity to an Airbus A320. The power system selected consisted of two under-wing mounted conventional turbofans and an electrically driven boundary layer ingesting fan, located at the rear fuselage. The power required to drive the fan is extracted from both turbofans. The worked carried out and presented in this paper offers a new approach to modelling boundary layer ingestion configurations, consisting of using the sliding mesh method to simulate the rotation of the blades within an airflow. The simulations were performed in two phases. The first stage corresponded to the analysis of an isolated configuration, where fuselage and electric fan were considered to be far away from each other such that there is no aerodynamic interference between the fuselage and the electric fan. During the second phase, the simulations were conducted with the electric fan integrated with the airframe, ingesting the boundary layer around the fuselage. The simulations indicate that ingesting the boundary layer results in remarkable improvements reducing drag and increasing propulsive force, reaffirming the potential of this technology to reduce fuel consumption. However, the results also registered a substantial increment in the pitching, rolling and yawing moments in the integrated configuration with respect to the isolated arrangement. This gain needs to be accounted for during early stages of the design process to maintain the stability and control of the aircraft within acceptable margins.

Preliminary engine design and inlet optimization of the MULDICON concept

In this study, aspects of the propulsion design for a highly swept wing configuration with military application are presented. These include the design of the thermodynamic cycle and the automated optimization of the inlet geometry. First, the thermodynamic design process of a conventional turbofan engine is described, which is intended to meet the requirements of a generic UCAV configuration. In addition to the thrust requirements derived from the mission profile, other constraints such as maximum fuel consumption, available installation space and aerodynamic and structural limits dimension the model in preliminary design. The resulting engine data are used as boundary conditions for the CFD simulation of the associated engine intake. This CFD calculation is part of an optimization process chain for determining the inlet duct geometry with low total pressure loss and low engine visibility. In order to estimate the effects of the different total pressure losses on the mission fuel consumption, the results obtained using CFD calculations are fed back into the performance simulation. This allows quantifying the influence of the inlet geometry on the global engine parameter. Based on the investigations and obtained results, the final configurations for the engine and intake are selected.

System Noise Assessment of a Tube-and-Wing Aircraft with Geared Turbofan Engines

A geared turbofan with an increased bypass ratio promises reduced engine noise generation if compared to conventional turbofan engines with lower bypass ratios. As a result, the dominance of other noise sources on an aircraft with geared turbofan engines is emphasized and will become more relevant. Consequently, to get an understanding of the modified noise source ranking due to the new engine concept, a noise assessment of the overall aircraft noise as received on the ground is essential: that is, a so-called system noise assessment. For this study a German Aerospace Center (DLR) and Technical University of Brunswick aircraft design synthesis process with integrated noise prediction capabilities is applied. The noise assessment is not limited to the overall vehicle noise as received on the ground but, moreover, the dominance and ranking of all individual noise sources are discussed. A direct comparison and evaluation of the flight performance and the system noise of the different vehicle variants under consideration are presented. Finally, the geared turbofan engine is also installed on an earlier low-noise aircraft concept featuring engine noise shielding. The influence of low-noise airframe measures in combination with a geared turbofan concept are promising, especially on an airframe architecture dedicated to engine noise shielding.

Performance Optimization of Adaptive Cycle Engine during Subsonic Climb

Adaptive Cycle Engine is a candidate propulsion system for next generation fighters which can meet the multi-mission requirements of future air combat. Considering the performance requirements of fighter’s climb mission, the engine performance is optimized in constraints by Genetic Algorithm. The climb results of the fighter, which are calculated with different engine performances, are also compared. The results show that the Adaptive Cycle Engine has better subsonic-climb performance than the conventional turbofan, and the optimization of variable geometric mechanisms can further improve its advantages.

Mission Analysis and Emissions for Conventional and Hybrid-Electric Commercial Transport Aircraft

A feasibility study of a hybrid-electric commercial transport aircraft was conducted by analyzing the simulated performance and lifecycle carbon dioxide () emissions of a conventional single-aisle aircraft and an aircraft with a modified parallel hybrid-electric propulsion system. A flight performance simulation was developed in a MATLAB/Simulink environment using publicly available aircraft data for the Boeing 737-700 commercial transport aircraft and the CFM56-7B26 turbofan engine. A parallel hybrid drivetrain was integrated into the aircraft performance model. Various missions with different degrees of hybridization and battery specific energy densities were simulated and compared to the conventional turbofan case. emissions associated with fuel burn and electricity generation for charging battery systems were modeled for each hybrid aircraft configuration. The results indicated that reductions in emissions per passenger mile were achievable using a parallel hybrid propulsion system as compared to conventional systems of equivalent range. A candidate propulsion system configuration was defined, which used a 50% electrical-power drivetrain and a battery specific energy density of . This configuration was estimated to produce 49.6% less lifecycle emissions than a modern conventional aircraft, with a maximum range equivalent to that of the average of all global flights, making it a viable option for environmentally responsible aviation.

Design of Next Generation Civil and Military Aircraft with Ultra-High Bypass Engine using Composites, Advanced Materials and Technology

Indirect combustion noise had not been attracting research in the past, but recent indication seems to prove that it could be a threat in the future if not addressed. Means of reducing this type of noise to a low decibel value was also included. Noise is due to the ingestion of distorted atmospheric turbulence, as the two set of blades rotate in different direction. Open rotor noise is higher since the rotors are fully exposed to oncoming turbulence and lack ducting or a nacelle to attenuate the radiated sound. A thorough review on the technology that can replace conventional turbofan was carried out. It was found that none of this technology can meet up with the ACARE and NASA 2020 vision but left a gap to be filled. Because open rotor is the most proven engine that is able to satisfy this requirements, different methods are adopted and integrated to reduce open rotor noise. Attention was paid to the geometry of the blade, hub and blade length, the vorticity and interaction noise are simulated until an optimized blade was achieved. The integration problem of open rotor was addressed where the engine was located to minimize perceive noise to the payload.

Dual Drive Booster for a Two-Spool Turbofan: High Shaft Power Offtake Capability for More Electric Aircraft and Hybrid Aircraft Concepts

The effects of high shaft power offtake (POT) in a direct drive, a geared drive, and a novel turbofan configuration are investigated. A design and off-design performance analysis shows the configuration specific limitations and advantages. The more electric aircraft (MEA) concept promises to offer advantages with respect to aircraft performance, maintenance, and operating costs. The engines for the MEA concept are based on conventional turbofan architectures. These engines are designed for significantly increased shaft POT that is required by the airframe, and the shaft power is usually taken off the high-pressure (HP) spool. This can impair the off-design performance of the engine and lead to compromises during engine design and to operability limitations. Taking the power off the low-pressure (LP) spool mitigates some of the problems but has other limitations. In this work, an alternative novel turbofan architecture is investigated for its potential to avoid the problems related to high shaft POTs. This architecture is called the dual drive booster because it uses a summation gearbox to drive the booster from both the LP and HP spool. The shaft power, if taken off the booster spool, is effectively provided by both the LP and HP spools, which allows the provision of very high power levels. This new concept is benchmarked against a two-spool direct drive and a geared drive turbofan (GTF). Furthermore, it is described, how the new architecture can incorporate an embedded motor generator. The presented concept mitigates some of the problems, which are encountered during high POT in conventional configurations. In particular, the core compressors are less affected by a change in shaft POT. This allows higher POTs and gives more flexibility during engine design and operation. Additionally, the potential to use the new configuration as a gas turbine-electric hybrid engine is assessed, where electrical power boost is applied during critical flight phases. The ability to convert additional shaft power is compared with conventional configurations. Here, the new configuration also shows superior behavior because the core compressors are significantly less affected by power input than in conventional configurations. The spool speed and its variation are more suitable for electrical machines than in conventional configuration with LP spool power transfer. The dual drive booster concept is particularly suited for applications with high shaft POTs and inputs, and should be considered for propulsion of MEAs.

Research on Influence of Geometric Adjustment on Performance of Variable Cycle Engine

Based on conventional turbofan engine, this paper adding mode selection valve, the front variable area bypass injectors and the rear variable area bypass injectors to build a mathematical model of the variable cycle engine. Then the influence of adjustable components on engine performance is simulated by computation program. The simulation results show that in the same work mode, the front variable area bypass injectors and the rear variable area bypass injectors have the same effect on engine performance, but different from the mode selection valve; Both front variable area bypass injectors and rear variable area bypass injectors have different effects on engine performance in different modes.

Experimental Quantification of Fan Rotor Effects on Inlet Swirl Using Swirl Distortion Descriptors

The prominence of highly integrated engine/airframe architectures in modern commercial aircraft design concepts has led to significant research efforts investigating the use of conventional turbofan engines in unconventional installations where severe inlet distortions can arise. In order to determine fan rotor capabilities for reducing or eliminating a complex inlet swirl distortion, an experimental investigation using a StreamVaneTM swirl distortion generator was conducted in a turbofan engine research platform. Three-dimensional (3D) flow data collected at two discrete planes surrounding the fan rotor indicated that the intensity of the swirl distortion was decreased by the fan rotor; however, substantial swirl distortion effects remained in the fan exit flow. Flow angle magnitudes and swirl intensity (SI) decreased by approximately 30–40% across the fan rotor, while the presence of large-scale features within the distortion profile was nearly eliminated. Secondary flow streamlines indicated that small-scale features of the distortion were less affected by the rotating component and remained coherent at the fan rotor outlet plane. These results led to the conclusion that swirl distortion survived interactions with the fan rotor, leading to off-design conditions cascading through downstream engine components.

Performance analysis of an electrically assisted propulsion system for a short-range civil aircraft

With civil aviation growing at around 4.7% per annum, the environmental footprint of aviation is increasing. Moreover, the use of kerosene as a fuel accelerates the depletion of non-renewable fossil fuels and increases global warming. Hence, the aviation industry has to come up with new technologies to reduce its environmental impact and make aviation more sustainable. An electrically assisted propulsion system can combine the benefits of an electrical power source with a conventional turbofan engine. However, the additional electrical system increases the weight of the aircraft and complexity of the power management system. The objective of this research is to analyze the effect of an assistive electrical system on the performance of a turbofan engine for an A320 class aircraft on a short-range mission. The developed simulation model consists of an aircraft performance model combined with a propulsion model. The power management strategy is integrated within the simulation model. With the proposed propulsion system and power management strategy, the electrically assisted propulsion system would be able to reduce fuel burn, total energy consumption, and emissions for short-range missions of around 1000 km.

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

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 system consists of a battery-powered motor partially driving the low-pressure shaft of a conventional turbofan engine. The applied motor power adds an additional degree of freedom, along with power setting, available to the aircraft designer during mission analysis. Modeling features and issues unique to hybrid-electric propulsion systems are described, and a vehicle trade study is carried out to determine the optimum engine cycle for both a cryogenic and conventionally driven motor system.

Dual Drive Booster for a Two-Spool Turbofan: Performance Effects and Mechanical Feasibility

A novel two-spool turbofan engine configuration is described which uses a booster powered by both the low an high pressure spools. Design and off-design performance analysis shows the operating characteristics of the configuration, and a mechanical feasibility study of the gearbox is presented. The trends toward ever higher engine overall pressure ratio and bypass ratio have resulted in a combination of higher pressure ratio and lower blade speed in the booster compressor of conventional two-spool turbofans. This combination gives rise to many stages in the booster and/or lower booster efficiency and also a higher degree of off-design mismatch between the core compressors. The current paper describes an engine architecture which aims to alleviate both these issues by powering the booster compressor from both low and high pressure spools through an epicyclic gear system. We have called this engine architecture the dual drive booster. The concept gives the engine designer greater flexibility to optimize component performance and work split, resulting in the potential for lower cruise specific fuel consumption and higher hot-day takeoff thrust capability than current engine configurations. The gear system is described along with the mathematical derivation of the booster rotational speed in terms of LP- and HP-spool speeds. Both the design point and off-design performance modeling have been conducted and comparison is made between a conventional turbofan and a turbofan fitted with the dual drive booster. The results show a significant enhancement in takeoff thrust due to the better speed match of the booster. The paper also describes the results of a preliminary study into the design and mechanical feasibility of the engine architecture and gear system. The presented concept is an alternative to the conventional turbofan and should be considered during the conceptual design of future aircraft engines.

Анализ экологических аспектов применения перспективных схем силовых установок ближне- и среднемагистральных самолетов

The influence of the circuitry of the hybrid power plant short and medium haul aircraft on their fuel efficiency and
 environmental characteristics have been investigated. Directions of improvement of traditional patterns of power plants of
 aircraft on the example of PD-14 engine were analyzed. It has been shown that the use of turbojet engines and traditional
 schemes operating on aviation kerosene, will not allow to fulfill the demands made by the International Civil Aviation
 Organization (ICAO) to perspective plane 2025–2035. The analysis of the three schemes hybrid propulsion systems has
 been performed. It has been shown that using the presented hybrid propulsion systems of alternative fuels can reduce CO2
 emissions by 19% to 20% compared with conventional turbojet engines, which run on kerosene TS-1. It has been shown
 that this fuel efficiency is increased by 2–3%, and the total mass of the power plant increases of 6 to 16%.