Search

Aircraft Health Management Technology for jet engines represents a very important problem, since it develops a large impact on reducing the engine life cycle costs, improving the fuel efficiency, increasing the engines durability and life cycle. This technology is high-end and, in order to enable an improved level of performance that far exceeds the current one, propulsion systems must comply with terms of reducing harmful emissions, maximizing fuel efficiency and minimizing noise, while improving system’s affordability and safety. Aircraft Health Management Technology includes multiple goals of aircraft propulsion control, diagnostics problems, prognostics realized, and their proper integration in control systems. Modern control for Aircraft Health Management Technology is based on improved control techniques and therefore provides improved aircraft propulsion system performances. The study presented in this paper approaches a new concept, of attractive interest currently, that is the intelligent control; in this context, the Health Management of jet engines is crucial, being focused on engine controllers which are designed to match certain operability and performance constraints. Automated Engine Health Management has the capacity to significantly reduce the maintenance effort and propulsion systems’ logistical footprint. In order to prioritize and resolve problems in the field of support engineering there are required more detailed data on equipment reliability and failures detection and management; the equipment design, operations and maintenance procedures and tooling are also very important.

The chemical properties of the fuels are crucial for obtaining the numerical accuracy during the design and performance analysis in case of liquid fuel propelled rocket engines, as well as the trajectory optimization. In this paper, the research was primarly focused on optimizing the numerical accuracy for non-linear two-dimensional approximation the Fuel Combustion Charts; secondarily, the investigation was carried on the design of the bell-nozzle of a liquid propelled rocket engine, taking into account the variation of the coefficients which are significant for expressing the fuels chemical properties. From the Fuel Combustion Charts, the authors selected a the LOX - Kerosene combination for propelling the rocket engine, due to the most convenient matching with the technology and material specifications, safety and environmental friendly requirements; from the LOX-Kerosene Charts, the authors have originally developed a method to obtain the expression of a non-linear approximation function of two variables. The design of the bell shaped nozzle and combustion chamber for a liquid propelled rocket engine was included, in purpose to illustrate the link between the LPRE design and the fuels types and chemical properties.

The Fuel Management Systems for civil aircrafts have a direct impact on the airlines profitability, competitiveness and sustainability, because the fuel represents the highest cost for airlines, on average 32% of overall operating costs; extra costs can frequently be taken into account, due to the increase in time of approach and straight-in landing versus circle to land maneuver. The core philosophy of the Fuel Management Systems, targeted to aircraft safety, must be focused on the most important aspects regarding the efficient operation of an airline and its proper management expressed in terms of efficacy, efficiency and effectiveness; an actual concern of great interest is the adequate fuel management. In this paper, a thorough study was carried on based on the state of art detailed investigation, with numerical simulations for significant case studies which are relevant for the implementation of robust fuel management processes in order to increase the internal efficiency and reduce the overall costs. In this paper, fuel management solutions and specific mode of their implementation are presented. The benefits of Fuel Aircraft Management Systems are multiple related and refer to: minimizing the costs, reducing the workload, improving internal and external data sharing, reducing unnecessary communications, controlling fuel costs, making better decisions, improving cash flow and creating a more cohesive approach to the Fuel Aircraft Management System. The applications of Fuel Aircraft Management System are beneficial to the aviation industry, and particularly, this study brings a significant contribution to the topic, i.e. advances in Fuel Aircraft Management System.

This study provides significant contributions to solve a problem of worldwide utmost interest: Collision Detection and Resolution CDR, due to the constant increase in air traffic. Based on the geometry equations exposed in this paper, numerical simulations for UAV’s within 3D space have been carried on and a detailed analysis of TCAS operating around another UAV. On this basis, a specific algorithm for collision avoidance in case of multiple aircraft has been developed. An important contribution to the study is the collision detection in random velocity multiple objects environment. The simulations have been conducted for two significant UAV group configurations subjected to potential risk of collision.

The purpose of this paper is to expose a more complex mathematical model for performance prediction in case of the mixed flows turbofan engine. The numerical simulations followed two streams for the investigating the performances of the mixed flows turbofan engine, at the design point and variate off-design conditions. Following the determination of the performances, then the Maps of the Mixed flows turbofan Engine (Altitude Map, Velocity Map, Speed Map and Universal Map) will be concluded. This investigation can be also carried on or analyzing the influence of perturbations in the main parameters of the engine, such as the turbine inlet temperature, pressure ratio and air mass flow rate. The numerical results are summarized graphically. The importance of this study is shown by the author's contribution to the development of a more complex model and an in-house code, which can be further integrated into mixed flow turbofan engine control studies.

The purpose of this paper is to expose a more complex mathematical model for performance prediction in case of the turbojet engine. The numerical simulations followed two streams for the investigating the performances of the turbojet engine, at the design point and variate off-design conditions. Following the determination of the performances, then the Maps of the Turbojet Engine (Altitude Map, Velocity Map, Speed Map and Universal Map) will be concluded. This investigation can be also carried on or analyzing the influence of perturbations in the main parameters of the engine, such as the turbine inlet temperature, pressure ratio and air mass flow rate. In addition to the main objective dedicated to determining the Engine Maps, it was also completed the objective centered on the effect of +/- 50 [K] perturbation in turbine inlet temperature on predicted performances of the turbojet engine. The numerical results are summarized graphically. The importance of this study is shown by the author's contribution to the development of a more complex model and an in-house code, which can be further integrated into jet engines control studies.

The design and performance prediction of rocket engines require appropriate mathematical modeling for complex intricate phenomena; the main goals are optimized geometry and obtaining the best numerical accuracy. The algorithms and input data can be validated with numerical simulations, in experiment and comparison with available data from state of art survey. Relevant to this topic, can be approached investigations for complex and intricate phenomena, such as: propellant atomization, mixing, evaporation, chemical reaction, gas expansion, as well as effects (e.g. chemical reaction rates, and boundary-layer and streamline and velocity-vector divergence in the converging and diverging nozzles) intended to a more accurate description of real phenomena. This paper presents an exhaustive study, based on iterative calculations for a liquid propelled rocket engine, with optimized performances and improved geometry. The results of our research (optimized LPRE) is driven environment friendly due to the selection of fuels: Kerosene (RP-1) and Liquid Oxygene (LOX).

The use of jet engines as propulsion systems for Unmanned Aerial Vehicles UAV's represents a actual challenge. For a large class of UAV's, providing more advantages with respect to the turboprop and turboshaft engines, as well as super-charged V12 piston engines, the small to medium size turbojet engines represent a more effective option. The research presented in this paper is focused on the thermo-dynamical analysis of a small sized turbojet. The single- spool turbojet engine model was used for the performance analysis; the one-dimensional engine cycle design was used to calculate the turbojet performances for a specified range of flight altitude and Mach number, as well as various engine operational regimes. From the numerical simulations have been expressed new parameter correlations, e.g. thrust - fuel flow, which will contribute to the deduction of a control law for the fuel flow. The objectives of the thermo- dynamical analysis have been fulfilled, with the calculated engine operating maps (i.e. variation of performances with altitude, flight Mach number and engine rotational speed), universal map of the engine; in addition, this analysis provides the values for significant engine parameters which are required by the engine's dynamic study.

This paper is dedicated to the study and analysis of a successfully designed control system, whose capability should always maintain the stability and performance level in spite of the uncertainties in system dynamics and within the working environment to a certain degree. Design requirements such as gain margin and phase margin in using classical frequency-domain techniques are solely for the purpose of robustness. A constrained optimization is then performed to maximize the robust stability of the closed-loop system to the type of uncertainty chosen, the constraint being the internal stability of the feedback system. In most cases, it would be sufficient to search a feasible controller such that the closed-loop system should achieve certain robust stability. Performance objectives can also be included in the optimization cost function. Elegant solution formulae have been developed, which are based on the solutions of certain Algebraic Riccati Equations.

This paper presents an approach for the interaction prediction and convergence analysis and the optimal control problem of the dynamic systems, which eventually improves the numerical accuracy of the results. The convergence behavior of the proposed algorithms for analyzing the study case presented in this paper, can be solved in hierarchical structures by introducing a set of coordination variables. The lower level solves the local optimization problems while keeping the coordination variables fixed, and the upper level uses the optimal trajectories received from the lower level to update the coordination vectors, which afterwards are sent back to the lower level. In accordance with the coordination parameters, there will be two approaches considered in this paper: first, the interaction prediction where the coordination vector is an input and second, the cost prediction approach with the coordination vector. A mathematical study of the convergence behavior of the proposed algorithms is presented. It is shown that the new algorithm is convergent under given sufficient conditions which are strongly related to the interaction between the subsystems and the integration period.

The aeroservoelastic model consists of a constant-chord wing model mounted on a moving platform and elastically suspended both in plunge and pitch motion in order to thus reproduce the conditions of a typical deformable aircraft wing. The model represents basically a coupled two-degree of freedom dynamical system. The system parameters were chosen such that the model would be capable of exhibiting sustained self-inducted oscillations - flutter, at relatively moderate air speed and reduced frequencies.In purpose to control this model, a simple electrically driven trailing-edge flap was added over the entire wing span. For the specific problem of the active flutter suppression, the flap should be included in a command line through a feedback connection. For the flutter as well as for the much more complex problem of flutter suppression, the representation of the aerodynamic forces is a very important aspect. The active control of nonlinear aeroelastic instability, such as active flutter suppression, is becoming a promising and attractive technology, because it can simultaneously reduce the weight and increase the performances of the modern aircrafts. Flutter is one of the most representative topics of aeroelasticity. Active suppression of aeroelastic instabilities, such as flutter, divergence, and control reversal, will lead to improved performances.

The purpose of this paper is to set up a method to determine the missing engine design parameters (turbine inlet temperature T3T, airflow rate) which significantly influence the jet engines thrust. The authors have introduced a new non-linear equation connecting the fan specific work with the temperature T3T, customized for turbofan. The method of chords, since it converges unconditionally, has been used for solving the non-linear equation of variable temperature T3T. An alternate method, based for the same relation between fan specific work and T3T, has been presented in purpose to determine airflow rate and fan pressure ratio. Two mixed flows turbofans have been considered as study cases. For case #1 it was determined a value comparable to the Turbomeca Larzac turbofan series 04-C6 and 04-C20 which power the AlphaJet machines (series A - Luftwaffe, series E - Dassault Dornier). For the F100-PW229 turbofan, as case #2, being given T3T, then have been determined the airflow rate, fan pressure ratio and fan specific work. After completing the mathematical model with the missing parameters, the performances of the engines at off-design regimes and the operational envelopes revealing i.e. the variations of thrust, specific thrust and fuel specific consumption with altitude and Mach number have been calculated.

Aeroelastic flutter involves the adverse interaction of aerodynamics with structural dynamics and produces an unstable oscillation that often results in structural failure. Such oscillations must strictly be avoided, because these can lead to catastrophic failures. Important issues such as the reduction of the flutter speed and structural stiffness are analyzed and concluded that can be obtained by weight reduction and aerodynamically efficient high aspect ratio wing design. Future flight control systems will be designed to use active control systems to counter these adverse aeroservoelastic effects, such that this feature will become of increasingly importance for the ensuring the safety of flight. The study presented in this paper is dedicated to linear and nonlinear aeroelastic response, which is modeled on account of experimental data basis, being focused on analyzing and controlling the prescribed plunge and pitch motion of a wing. The addition of either a control surface, combined active control system, extends the stable flight domain. The aerodynamic model of the plunge and pitch motion of the wing is developed from an approximation of the classical unsteady theory. Complete details about a full-state feedback control law, as well as a calculated optimal observer which are incorporated in purpose to stabilizing the system above the open loop flutter velocity, are presented in this paper. Following the use of the linear theory, an original nonlinear model is introduced and tested for the considered control laws. The paper concludes with an excellent correlation between theory and experiment that is achieved for the exposed models.Aeroelastic flutter involves the adverse interaction of aerodynamics with structural dynamics and produces an unstable oscillation that often results in structural failure. Such oscillations must strictly be avoided, because these can lead to catastrophic failures. Important issues such as the reduction of the flutter speed and structural stiffness are analyzed and concluded that can be obtained by weight reduction and aerodynamically efficient high aspect ratio wing design. Future flight control systems will be designed to use active control systems to counter these adverse aeroservoelastic effects, such that this feature will become of increasingly importance for the ensuring the safety of flight. The study presented in this paper is dedicated to linear and nonlinear aeroelastic response, which is modeled on account of experimental data basis, being focused on analyzing and controlling the prescribed plunge and pitch motion of a wing. The addition of either a control surface, combined active control sys...

This paper presents the algorithms for the solution of the optimal control problem of wide scale linear dynamic systems. These algorithms are based on the prediction concept. For the beginning, is considered the interaction prediction approach and afterwards, the cost prediction approach is used. The convergence behavior of the proposed algorithms is thoroughly investigated. In this paper is designed a multi-input, multi-output controller by shaping the gain of an open-loop response across frequency. This technique is applied to controlling the pitch axis of an aircraft. Eventually, the paper successfully investigates and demonstrates how to choose a suitable target loop shape and to compute a multivariable controller that optimally matches the target loop shape.

The purpose of this paper is to present a 2D study regarding the numerical simulation of flow within a transonic highly-loaded rotating cascade from an axial compressor. In order to describe an intricate flow pattern of a complex geometry and given specific conditions of cascade’s loading and operation, an appropriate accurate flow model is a must. For such purpose, the Navier-Stokes equations system was used as flow model; from the computational point of view, the mathematical support is completed by a turbulence model. A numerical comparison has been performed for different turbulence models (e.g. KE, KO, Reynolds Stress and Spallart-Allmaras models). The convergence history was monitored in order to focus on the numerical accuracy. The force vector has been reported in order to express the aerodynamics of flow within the rotating cascade at the running regime, in terms of Lift and Drag. The numerical results, expressed by plots of the most relevant flow parameters, have been compared. It comes out that the selecting of complex flow models and appropriate turbulence models, in conjunction with CFD techniques, allows to obtain the best computational accuracy of the numerical results. This paper aims to carry on a 2D study and a prospective 3D will be intended for the same architecture.

This paper presents an implementation of the modified Newton method for the aerodynamic analysis of Planetary Reentry Capsules. A straightforward method is employed, such that a CATIA model and its hybrid surface mesh are used as input. Reference capsules are analyzed and results are compared to other similar codes. Future improvements of the code consider the Busemann correction of the wall pressure, heat flux evaluation and unsteadiness in order to enable the analysis of the hypersonic portion of trajectory and to assess the vehicle's stability.

The purpose of this paper is to present the development of an original optimization method, designed in order to obtain improved performances due to the fact that all the operating regimes of the axial compressor AC cascades are found within the stability domain. The optimization method is based on new correlations between the cascade's geometric and aerodynamic parameters and the universal map of cascades. A new criterion was introduced in purpose to assess the stability range of the running regimes in case of the AC cascades, by using the Zweifel number and the universal map of cascades. The optimization method elaborated by the author finds its practical validation in the wide- chord fan and compressor blades constructions that are already being built for modern turbofans, by constructors, as the General Electric, Pratt & Whitney and Rolls-Royce. The motivation of the constructors is to achieve the dynamic stability, but from the author's point of view, the static stability was also included.

The objectives of this paper are the study and the implementation of both aerodynamic and propulsion models, as linear interpolations using look-up tables in a database. The aerodynamic and propulsion dependencies on state and control variable have been described by analytic polynomial models. Some simplifying hypotheses were made in the development of the nonlinear aircraft simulations. The choice of a certain technique to use depends on the desired accuracy of the solution and the computational effort to be expended. Each nonlinear simulation includes the full nonlinear dynamics of the bare airframe, with a scaled direct connection from pilot inputs to control surface deflections to provide adequate pilot control. The engine power dynamic response was modeled with an additional state equation as first order lag in the actual power level response to commanded power level was computed as a function of throttle position. The number of control inputs and engine power states varied depending on the number of...

The purposes of modeling and simulation of a turbojet engine are the steady state analysis and transient analysis. From the steady state analysis, which consists in the investigation of the operating, equilibrium regimes and it is based on appropriate modeling describing the operation of a turbojet engine at design and off-design regimes, results the performance analysis, concluded by the engine’s operational maps (i.e. the altitude map, velocity map and speed map) and the engine’s universal map. The mathematical model that allows the calculation of the design and off-design performances, in case of a single spool turbojet is detailed. An in house code was developed, its calibration was done for the J85 turbojet engine as the test case. The dynamic modeling of the turbojet engine is obtained from the energy balance equations for compressor, combustor and turbine, as the engine’s main parts. The transient analysis, which is based on appropriate modeling of engine and its main parts, expresses the dynamic behavior of the turbojet engine, and further, provides details regarding the engine’s control. The aim of the dynamic analysis is to determine a control program for the turbojet, based on the results provided by performance analysis. In case of the single-spool turbojet engine, with fixed nozzle geometry, the thrust is controlled by one parameter, which is the fuel flow rate. The design and management of the aircraft engine controls are based on the results of the transient analysis. The construction of the design model is complex, since it is based on both steady-state and transient analysis, further allowing the flight path cycle analysis and optimizations. This paper presents numerical simulations for a single-spool turbojet engine (J85 as test case), with appropriate modeling for steady-state and dynamic analysis.