Aircraft Power Plants Research Articles

Modern Refractory Alloys Based on Titanium Gamma-Aluminide: Prospects of Development and Application

The recent scientific and engineering level of refractory intermetallic alloys based on equiatomic titanium gamma-aluminide (TiAl) for aircraft engines and power plants is reviewed. The main tendencies and prospects of development of such alloys, processes of their production and treatment are described.

Resource recycling of superalloys and hydrometallurgical challenges

Superalloys are high melting temperature, excellent creep resistance, anti-corrosive, and oxidation resistant alloys; they are predominantly used in gas turbines of aircraft engines and power plants. Today, a series of superalloys is available according to their composition and applications. The tough nature of superalloys makes it difficult to recycle them after they are formed; this increases the demand and shortage of the energy-critical elements that are their raw materials and makes their processing one of the most demanding form of recycling today. A few processes are available, and some of these unique recycling systems are in use; however, a lack of data and/or information exists for two reasons: (i) scrap recycling is most frequently performed by superalloy manufacturers themselves (not always by the same unit) by recharging them into molten charges, and (ii) the recycler does not want to produce business for their rivals. This article presents an overview of the processes investigated to recycle superalloys, including the advantages and disadvantages of each. The available processes are not very technologically or economically feasible; therefore, further efforts are necessary to explore these processes and to make a value-added product by recycling superalloys rather than just re-melting them. Considering the continuously increasing number of alloyed elements in advanced superalloys, this paper also notes to the challenges associated with hydrometallurgical recycling of superalloys and the need for future studies on this topic.

Model-based System Safety Assessment of Aircraft Power Plant

The aircraft power plant becomes even harder since the complexity and integrity of system function, and the traditional system safety analysis, influenced by the personal skills and experience of analysis, may cause error and system failure condition and effects. The paper presents a new approach called Model-based Safety Analysis (MBSA) for complex system, and the process of MBSA is studied by linking function modeling using formal language and fault propagation based on Altarica, and the given method can be introduced to aircraft power plant system in order to unify the process the system development and system safety assessment, and versatility and feasibility of the approach are demonstrated with the case study of aircraft power plant.

Compressor Instability: Stall, Surge and their Control

Every compressor has a stall line. In the vicinity of the stall line, the flow field is inherently unsteady due to the interactions between adjacent rows of blades, formation of small stall cells, flow separation and the viscous effects including shock-boundary layer interactions. These factors may aggravate to a state of local breakdown of flow or a total breakdown of flow or with a disastrous flow reversal. This paper starts with an overview on the previous researches about compressor stall and surge. Subsequently, it describes the effects of these instabilities in overall engine performance and design with/ without any control. The main objectives of this paper are to review the phenomenon of instability and methodology to suppress the rotating stall and surge by enlarging the stable operating range of compressor with the application of various control systems. This paper surveys research developments in this field and also tries to find an improved solution to increase the engine performance by applying various surge control strategies. Finally, the paper focuses on some recommendations towards a better design of compressor especially for aircraft power plant.

Numerical Simulation of Distribution of Discharged Gas Fire Extinguishing Agent in High Velocity Flow Field

This paper studied the concentration distribution of gas extinguishing agent numerically in high velocity flow field. Civil aircraft power plant compartment has been a difficult area for its high velocity flow field formed after fire happens. Focusing on this issue, certain results, such as mass flow rate of agent gas, total mass of agent and extinguishing efficiency were presented. A typical apparatus of fire extinguishing system was set up, and its fire-fighting efficiency was evaluated. Critical ratio of mass flow rate and flow velocity, gas discharge time and locations of gas sample tubes were recommended. The results and data can provide a practical way in fire extinguishing system evaluation in civil aircraft power plant compartment.

Bi-objective optimization of pylon-engine-nacelle assembly: weight vs. tip clearance criterion

A realistic application of advanced structural and multi-objective optimization for the design of a fully assembled aircraft powerplant installation is presented. As opposed to the classical design process of powerplant installation that does not consider the influence of pylon sizing over engine efficiency, we develop in the present a fully integrated approach where both pylon and compressor intercase are designed at once. The main objective is to consider the impact of weight over tip clearance performance criterion and see how these two objectives are antagonistic. In this work, we perform in the same design session tasks traditionally devoted to the airframe manufacturer and aero-engine manufacturer. The overall weight of the assembly is minimized with respect to Specific Fuel Consumption (SFC) criterion. One interesting aspect of the process is that SFC criterion is based on highly proprietary models and its simulation and call within an optimization process is made available through the development of a webservice. One major phenomenon to consider in both pylon and engine design is Fan Blade Off (FBO) event, i.e. the sudden release of a blade. This event causes high impact loads and must be considered carefully in the design. Such a simulation is not an easy task and several nonlinear phenomena must be addressed (e.g. rotordynamics), not to mention the integration of this nonlinear dynamic response in a static structural optimization process. This article describes how the design of the full assembly is performed taking into account both objectives. Such a problem lies in multi-objective optimization field and then we describe the method we use to solve such a problem. The simulation of an FBO post-impact rotor dynamics is also described and we end up with the final results that show the influence of pylon-engine weight sizing over SFC.

Model identificaton for temperature extrapolation in aircraft powerplant systems

In the aerospace industry, the manufacturer Airbus must ensure that for all flight conditions, the temperature of each aircraft powerplant system must be less than its corresponding maximum declared temperature. In our days, based on flight test data, Airbus needs to develop temperature extrapolation methods in order to predict equipments' thermal behavior at the worst conditions. The proposed techniques are based on the system identification theory which consists on heuristically determining an analytical model using physical insights and measurements. More precisely, this paper validates ARX models as a tool for the identification of the system's temperature. This is done through the understanding of the physical insights of this type of structures and based on numerical simulations and laboratory representative tests.

Gas-Adsorption Indicator Method for NDT and Surface-Defect Characterization

The gas-adsorption indicator method (GAIM) is a relatively unknown yet reliable technique for nondestructive testing (NDT) of engineering materials, and component parts. Invented in Russia, GAIM is a spin-off from the BURAN space program in the former Soviet Union. GAIM is inspired on a highly effective method to detect defects on the tiles of the thermal protection system (TPS) of BURAN and leakages through seals in compartment hatches of the spacecraft. This method involved the capture of gas molecules by a chemically treated sheet. Based on this technique, GAIM was derived and developed into an innovative penetrant technique (PT) for NDT and NDE of surfaces. GAIM offers clear advantages over more conventional PT methods and other techniques for surface NDT and NDE. GAIM proves to be more versatile, adaptable, considerably less expensive, safer, and more reliable. It allows fast inspections, detections, and characterization of surface anomalies, such as cracks, corrosion, and micro-porosity. The technique can be used in a wide variety of materials, including metals, ceramics, specialized coatings, and composites. The applicability of GAIM for NDE and NDT is ample, ranging from simple lab tests to field inspections of spacecraft, aircraft, and nuclear and conventional power plants. The underlying physical phenomena and researched theory behind the technique are presented and explained. The technique is also illustrated with graphical documentation, and application examples.

Development of a transonic wind tunnel to investigate engine bypass flow heat exchangers

The design of a new transonic wind tunnel to reproduce bypass aero-engine flow conditions is described. This study has been driven by the interest to investigate and optimize the aero-thermal effects of an air/oil integrated surface heat exchanger placed at the inner wall of the secondary duct of a turbofan. The test section of the intermittent wind tunnel consists of a complex three-dimensional (3D) geometry. The flow evolves over the splitter, duplicated at real scale, as it does in the engine, guided by helicoidally shaped lateral walls. Numerical flow analyses have been used to guide the design of the complete wind tunnel. Zero-dimensional models have been developed to recreate the wind tunnel behaviour. Two- and three-dimensional computations have been performed to optimize the test section and the inlet guide vanes that duplicate the flow downstream of the engine fan. The reproduction of the bypass flow structure has been numerically analysed. Flow computations with and without the presence of instrumentation in the test section have been contrasted. Additionally, the influence of an aerodynamic probe on the flow has been studied numerically. This study should lead to improvements in the thermal management of future aircraft power plants, particularly by taking benefit of the cold bypass air to refrigerate the lubrication oil, without penalizing the propulsive efficiency.

Nonlinear combustion instability analysis based on the flame describing function applied to turbulent premixed swirling flames

Instability analysis of swirling flames is of importance in the design of advanced combustor concepts for aircraft propulsion and powerplant for electricity production. Thermoacoustic instabilities are analyzed here by making use of a nonlinear representation of flame dynamics based on a describing function. In this framework, the flame response is determined as a function of frequency and amplitude of perturbations impinging on the combustion region. This model is adapted to the case of confined swirling flames comprising an upstream manifold, an injection unit equipped with a swirler and a cylindrical flame tube. The flame describing function is experimentally determined and is combined with an acoustic transfer matrix representation of the system to provide growth rates and oscillation frequencies as a function of perturbation amplitude. These data can be used to determine regions of instability, frequency shifts with respect to the acoustic eigenfrequencies and they also yield amplitude levels when self-sustained oscillations of the system have reached a limit cycle. This equilibrium is obtained when the amplitude dependent growth rate equals the damping rate in the system. This requires an independent determination of this last quantity which is here based on measurements of the combustor resonance response curve, together with numerical estimates of the flame contribution to the system response. The geometrical parameters of the upstream manifold and flame tube are varied and the corresponding operating regimes are compared with those predicted with the FDF framework. The present demonstration of the FDF framework in a generic configuration indicates that this can be used in more general situations of technological interest.

A discrete model for compressible flows in heterogeneous media

This work deals with the building of a discrete model able to describe and to predict the evolution of complex gas flows in heterogeneous media. In many physical applications, large scales numerical simulation is no longer possible because of a lack of computing resources. Indeed the medium topology may be complex due to the presence of many obstacles (walls, pipes, equipments, geometric singularities etc.). Aircraft powerplant compartments are examples where topology is complex due to the presence of pipes, ducts, coolers and other equipment. Other important examples are gas explosions and large scale dispersion of hazardous materials in urban places, cities or underground involving obstacles such as buildings and various infrastructures. In all cases efficient safety responses are required. Then a new discrete model is built and solved in reasonable execution times for large cells volumes including such obstacles. Quantitative comparisons between experimental and numerical results are shown for different significant test cases, showing excellent agreement.

Comparison of Design Methods for Fuel-Cell-PoweredUnmanned Aerial Vehicles

This paper presents two comparisons of design methods for fuel-cell-powered unmanned aerial vehicles. Previous design studies of fuel-cell-powered aircraft have used design methods that contain intrinsic assumptions regarding the design of a fuel cell powerplant and regarding the interactions between the powerplant and aircraft application. This study seeks to understand the effects of these design assumptions on the fuel cell powerplant structure and the aircraft performance. A design methods comparison is constructed by first developing a multidisciplinary modeling and design environment that is more general than the design processes proposed in literature. The design processes from previous studies can then be imposed on the more complete design environment to determine the performance costs and morphological changes caused by the design assumptions. In the first design study, results show that designing fuel-cell-powered aircraft using automotive-type fuel cell design rules leads to a low-efficiency powerplant and a low-performance aircraft in long-endurance and long-range unmanned aerial vehicle applications. The second design study shows that designing the aircraft powerplant using powerplant design criteria (such as specific energy) rather than aircraft design criteria (such as range) leads to suboptimal aircraft performance, especially for long-endurance unmanned aerial vehicle applications. The results of these studies show that the application-integrated design of aviation-specific fuel cell powerplants can significantly improve the performance of fuel-cell-powered aircraft for a variety of scales and missions.

철도사고 인적오류 분석을 위한 지원시스템 프레임웍 설계

Human errors are now considered as the most significant source of accidents or incidents in large-scale systems such as aircraft, vessels, railway, and nuclear power plants. As 61% of the train accidents in Korea railway involving collisions, derailments and fires were caused by human errors, there is a strong need for a systematic research that can help to prevent human errors. Although domestic railway operating companies use a variety of methods for analyzing human errors, there is much room for improvement. Especially, because most of them are based on written papers, there is a definite need for a well-developed computerized system supporting human error analyzing tasks. The purpose of this study is to propose a framework for a computerized human error analysis system focused on the railway industry on the basis of human error analysis mechanism. The proposed framework consists of human error analysis (HEA) module, similar accident tracking (SAT) module, cause factor recommendation (CFR) module, cause factor management (CFM) module, and statistics (ST) module.

Development and experimental characterization of a fuel cell powered aircraft

This paper describes the characteristics and performance of a fuel cell powered unmanned aircraft. The aircraft is novel as it is the largest compressed hydrogen fuel cell powered airplane built to date and is currently the only fuel cell aircraft whose design and test results are in the public domain. The aircraft features a 500 W polymer electrolyte membrane fuel cell with full balance of plant and compressed hydrogen storage incorporated into a custom airframe. Details regarding the design requirements, implementation and control of the aircraft are presented for each major aircraft system. The performances of the aircraft and powerplant are analyzed using data from flights and laboratory tests. The efficiency and component power consumption of the fuel cell propulsion system are measured at a variety of flight conditions. The performance of the aircraft powerplant is compared to other 0.5–1 kW-scale fuel cell powerplants in the literature and means of performance improvement for this aircraft are proposed. This work represents one of the first studies of fuel cell powered aircraft to result in a demonstration aircraft. As such, the results of this study are of practical interest to fuel cell powerplant and aircraft designers.

Software in safety critical systems?achievement and prediction

Software is the primary determinant of function in many modern engineered systems, from domestic goods such as washing machines through mass-market products such as cars to civil aircraft and nuclear power plant. In a growing number of cases the software is safety critical or safety related, i.e. failure or malfunction could give rise to, or contribute to, a fatal accident. In general, where software is a key element of a safety critical system it is developed in accordance with a set of guidelines or standards produced by the industry, or imposed by a regulator.

Calibration and estimation of redundant signals for real-time monitoring and control

This paper presents a filtering algorithm for calibration and estimation of redundant signals for real-time condition monitoring and control of continuous plants. The redundancy may consist of sensor signals and/or analytical measurements that are derived from other sensor signals and physical characteristics of the plant. The redundant measurements are simultaneously calibrated by additive corrections that are recursively estimated based on the principle of linear least-squares filtering. A weighted least-square estimate of the measured variable is generated in real time from the calibrated signals. The weighting matrix is adaptively adjusted as a function of the a posteriori probability of failure of the calibrated measurements. The effects of intra-sample failure and probability of false alarms are taken into account in the formulation of the recursive filter that has been tested for on-line calibration of four redundant sensors of the throttle steam temperature in a commercial-scale fossil power plant. The calibration and estimation filter is potentially applicable to the Instrumentation & Control System Software in tactical and transport aircraft, and nuclear and fossil power plants.

The Future and Potential of Non-Steady Flow Devices in Advanced Propulsion Designs

Conventional aircraft powerplants generate a propulsive force through the application of a relatively constant fluidic flow. In non-steady flow propulsion, an unevenness of fluidic pressure is developed and purposefully controlled with the objective of producing thrust. This paper reviews basic non-steady flow concepts and presents potential applications for emerging technologies.

Calibration and estimation of redundant signals

This paper presents formulation and validation of an adaptive filter for real-time calibration of redundant signals consisting of sensor data and/or analytically derived measurements. The measurement noise covariance matrix is adjusted as a function of the a posteriori probabilities of failure of the individual signals. An estimate of the measured variable is obtained as a weighted average of the calibrated signals. The weighting matrix is recursively updated in real time instead of being fixed a priori. The calibration and estimation filter has been tested by injecting faults into the data set collected from an operating power plant. The filter software is presently hosted in a Pentium platform and is portable to other commercial platforms. The filter can be used to enhance the Instrumentation & Control System Software in tactical and transport aircraft, and nuclear and fossil power plants.

Fluid flow control devices for an aircraft powerplant

Fluid flow control devices for an aircraft powerplant

Damage-Mitigating Control of Power Systems for Structural Durability and High Performance

A major goal in the control of complex power systems such as advanced aircraft, spacecraft, and electric power plants is to achieve high performance with increased reliability, availability, component durability, and maintainability. The state of the art in the synthesis of control systems for complex mechanical processes focuses on improving performance and diagnostic capabilities under constraints that do not often adequately represent the dynamic properties of the materials. The reason is that the traditional design is based upon the assumption of conventional materials with invariant characteristics. In view of high performance requirements and availability of improved materials, the lack of appropriate knowledge about the properties of these materials will lead to either less than achievable performance due to overly conservative design, or overstraining of the structure leading to unexpected failures and drastic reduction of the service life. The key idea of the research work reported in this paper is that a significant improvement in service life can be achieved by a small reduction in the system dynamic performance. The concept of damage mitigation is introduced and, to this effect, a continuous-time model of fatigue damage dynamics is formulated. Finally, the results of simulation experiments are presented for transient operations of a reusable rocket engine.