Soheil Jafari

Application of particle swarm optimization in gas turbine engine fuel controller gain tuning

This article presents the application of particle swarm optimization (PSO) for gain tuning of the gas turbine engine (GTE) fuel controller. For this purpose, the structure of a fuel controller is firstly designed based on the GTE control requirements and constraints. The controller gains are then tuned by PSO where the tuning process is formulated as an engineering optimization problem. In this study, the response time during engine acceleration and deceleration as well as the engine fuel consumption are considered as the objective functions. A computer simulation is also developed to evaluate the objective values for a single spool GTE. The GTE model employed for the simulation is a Wiener model, the parameters of which are extracted from experimental tests. In addition, the effect of neighbour acceleration on PSO results is studied. The results show that the neighbour acceleration factor has a considerable effect on the convergence rate of the PSO process. The PSO results are also compared with the results obtained through a genetic algorithm (GA) to show the relative merits of PSO. Moreover, the PSO results are compared with the results obtained from the dynamic programming (DP) method in order to illustrate the ability of proposed method in finding the global optimal solution. Furthermore, the objective function is also defined in multi-objective manner and the multi-objective particle swarm optimization (MOPSO) is applied to find the Pareto-front for the problem. Finally, the results obtained from the simulation of the optimized controller confirm the effectiveness of the proposed approach to design an optimal fuel controller resulting in an improved GTE performance as well as protection against the physical limitations.

Real-time multi-rate HIL simulation platform for evaluation of a jet engine fuel controller

Abstract A new Hardware-In-the-Loop (HIL) platform is developed for testing of a turbojet engine fuel control system using a multi-rate simulation platform. The HIL equipment consists of an industrial PC and a commercial I/O board for jet engine simulation as the controlled process and an Electronic Control Unit (ECU) as the fuel controller. The controlled process consisting of actuator, physical process and sensors is fully simulated in HIL simulation. However, the high resolution signals of some components in the HIL simulation cause the real-time simulation to become difficult due to the need of small time-steps. As a result, the disparity between the jet engine model sampling rate and these high resolution signals requires a multi-rate simulation. In this study, a multi step size simulation is developed using multiple processors. These processors are designed to synchronize the status of the engine model with the control system as well as to convert the raw data of the I/O boards to actual input and output signals in real-time. These features make the HIL equipment more effective and flexible. The HIL environment is proved to be an efficient tool to develop various control functions and to validate the software and hardware of the engine fuel control system.

Evolutionary Optimization for Gain Tuning of Jet Engine Min-Max Fuel Controller

AS turbine aero engines (GTEs) have played a significant role in the expansion of the flight capabilities of modern aircraft. For a GTE, stable and safe operation of the engine components must be ensured in order to operate at the operability and performance level for which it is designed. The thrust response is also of great importance for an aircraft, both in terms of the speed of response and accomplishment of the adequate thrust [1]. Hence, an appropriate control system has always been an essential part of the GTEs to provide both regulation and management. The main task of a GTE control system is to provide the required performance while maintaining safe and stable operation [2]. The safetyconsiderationsincludethe flowinstability,highheatloads,and high cyclic stresses. In other words, the GTE control requirements include amainfuel controlforsetting andholdingsteady-state thrust (steady-state control mode) and fuel acceleration and deceleration schedules to provide limit protection (physical limitation control mode) and rapid time response for gas turbine engine (transient control mode) [3]. AsurveyonGTEcontrolstrategiesshowsthatvariousfuelcontrol methods have been used for GTE fuel control in the last two decades [4–16]. These studies show that the complexity of the engine control comes from the need to operate the engine as close as possible to its limits. In other words, the design of the control system for a gas turbine aero engine results in a series of single input single output controllers. Many methods such as PID, LQ, LQG, and H1 are used as one of the single feedback control loops of the GTE control system. In this case, the design method is based on a selection approach between various control loops. This strategy is named “min-max selection strategy,” as the selection of the control loops is based on a min-max approach between transient control loops. Minmax approach is an industrial method for the design of the GTE fuel control system. However, in order to provide an improved engine performance as well as the engine protection against the physical limitations, one of the most common complexities of the min-max selection strategy is controller gain tuning. Taking the nonlinearity and switching nature of this control strategy into account, gradient-based optimization methods have weak performance for gain tuning. As a result, this problem requires a non gradient optimization technique on the basis of the evolutionary algorithms. In this paper, application of an evolutionary algorithm for optimization of the min-max fuel controller parameters is presented. For this purpose, the control requirements and constraints for a gas turbine aero engine are first explained. The min-max fuel control strategy is then described and an initial min-max fuel controller is designed. Subsequently, using the genetic algorithm (GA), the parameters of the initial min-max fuel controller is tuned so that the engine requirements and constraints are satisfied. In optimization process, the fitness function is defined to minimize the settling time andfuelconsumption,wheretheweightfactorsaresetwithrespectto the importance of each function. In addition, a computer simulation programisdevelopedtoinvestigatetheeffectivenessoftheapproach for a single-spool jet engine. The results of simulation are validated by experimental data in both steady-state and transient modes to support the simulation model. Finally, the results are provided to investigate the performance of the optimized controller and to evaluate the effectiveness of the approach.

Fuzzy logic computing for design of gas turbine engine fuel control system

This paper presents the fuzzy logic computing for the design and implementation of fuel controller for gas turbine engines. For this purpose, a fuzz controller is designed in order to be implemented on an electronic control unit where it is used to drive a servo operated fuel control valve. The fuzzy logic computing approach for different parts of the controller including fuzzification, rule base, inference engine and defuzzification are then described. Finally, computer simulation of the fuzzy controllers integrated with the engine model is performed to investigate the effectiveness of the proposed fuzzy controller on the performance of a turbojet engine. The results are provided to show that an acceptable engine performance is achieved where the engine limitations is fulfilled.

A Comparative Analysis of Nature-Inspired Optimization Approaches to 2D Geometric Modelling for Turbomachinery Applications

A vast variety of population-based optimization techniques have been formulated in recent years for use in different engineering applications, most of which are inspired by natural processes taking place in our environment. However, the mathematical and statistical analysis of these algorithms is still lacking. This paper addresses a comparative performance analysis on some of the most important nature-inspired optimization algorithms with a different basis for the complex high-dimensional curve/surface fitting problems. As a case study, the point cloud of an in-hand gas turbine compressor blade measured by touch trigger probes is optimally fitted using B-spline curves. In order to determine the optimum number/location of a set of Bezier/NURBS control points for all segments of the airfoil profiles, five dissimilar population-based evolutionary and swarm optimization techniques are employed. To comprehensively peruse and to fairly compare the obtained results, parametric and nonparametric statistical evaluations as the mathematical study are presented before designing an experiment. Results illuminate a number of advantages/disadvantages of each optimization method for such complex geometries’ parameterization from several different points of view. In terms of application, the final appropriate parametric representation of geometries is an essential, significant component of aerodynamic profile optimization processes as well as reverse engineering purposes.

Fuzzy-Based Gas Turbine Engine Fuel Controller Design Using Particle Swarm Optimization

This paper presents the application of Particle Swarm Optimization (PSO) algorithm for optimization of the Gas Turbine Engine (GTE) fuel control system. In this study, the Wiener model for GTE as a block structure model is firstly developed. This representation is an appropriate model for controller tuning. Subsequently, based on the nonlinear GTE nature, a Fuzzy Logic Controller (FLC) with an initial rule base is designed for the engine fuel system. Then, the initial FLC is tuned by PSO with emphasis on the engine safety and time response. In this study, the optimization process is performed in two stages during which the Data Base (DB) and the Rule Base (RB) of the initial FLC are tuned sequentially. The results obtained from the simulation show the ability of the approach to achieve an acceptable time response and to attain a safe operation by limiting the turbine rotor acceleration.

A review of evaporative cooling system concepts for engine thermal management in motor vehicles

The evaporative cooling system concepts proposed over the past century for engine thermal management in automotive applications are examined and critically reviewed. The purposes of this review are to establish the evident system shortcomings and to identify the remaining research questions that need to be addressed to enable this important technology to be adopted by vehicle manufacturers. Initially, the benefits of the evaporative cooling systems are restated in terms of the improved engine efficiency, the reduced carbon dioxide emissions and the improved fuel economy. This is followed by a historical coverage of the proposed concepts dating back to 1918. Possible evaporative cooling concepts are then classified into four distinct classes and critically reviewed. This culminates in an assessment of the available evidence to establish the reasons why no system has yet been approved for serial production commercially. Then, by systematic examination of the critical areas in evaporative cooling systems for application to automotive engine cooling, the remaining research challenges are identified.

CONTROL OF SPRAY EVAPORATIVE COOLING IN AUTOMOTIVE IC ENGINES

A novel approach is proposed for precise control of two-phase spray evaporative cooling for thermal management of road vehicle internal combustion engines. A reduced-order plant model is first constructed by combining published spray evaporative cooling correlations with approximate governing heat transfer equations appropriate for IC engine thermal management. Control requirements are specified to allow several objectives to be met simultaneously under different load conditions. A control system is proposed and modelled in abstract form to achieve spray evaporative cooling of a gasoline engine, with simplifying assumptions made about the characteristics of the coolant pump, spray nozzle, and condenser. The system effectiveness is tested by simulation to establish its ability to meet key requirements, particularly concerned with precision control during transients resulting from rapid engine load variation. The results confirm the robustness of the proposed control strategy in accurately tracking a specified temperature profile at various constant load conditions, and also in the presence of realistic transient load variation.

Role of Gas-Fuelled Solutions in Support of Future Sustainable Energy World; Part I: Stimuluses, Enablers, and Barriers

Tackling the challenges of energy poverty and changing living conditions in line with the growing population, and doing so in a sustainable manner, is recognised as being of utmost importance for the world today. The main goal of this study is to illuminate the fact that providing energy to an ever-growing population of the globe during a period of transition, and so doing in a responsible manner, requires a sustainable energy mix of fossils and renewables. Given the fact that the energy solution of tomorrow has to combine various fuels and technologies, different solutions will be needed for different regions, as determined in line with various factors, including the availability of resources and specific needs. Consequently, the role of gas-fuelled solutions as part of the transition towards future sustainable energy world needs to be illuminated from a technical, economic, social, political and geographical point of view. The discussions and conclusions presented in the chapter support the expectation of the increased use of natural gas as a part of the global transition towards a low-carbon energy society. From a carbon-neutral energy perspective, however, the use of biogas and renewable-based hydrogen as replacement for natural gas, in the long-term perspective, could be expected. In this way, natural gas will be an important complement to renewable energy during the transition period. Infrastructure and energy conversion technologies developed for natural gas need to be designed in such a way so as to be able to cope with the transition towards biogas and renewable supported hydrogen. Moreover, small-scale combined heat- and electricity-production and distributed generation could be a potential gas-fuelled solution, providing an improved fuel utilisation factor and, as a result, reduced emissions of greenhouse gases. Taking into account the challenges of the increasing demand for reliable and affordable energy, as well as global climate change, it is concluded that common understanding needs to be established amongst all the players, including society, industries, strategists, decision-makers, politicians and environmentalists, so as to reach a new level of commitment and partnership.

Theoretical and experimental study of a micro jet engine start-up behaviour

Proper functioning of the start-up process in a micro jet engine is of great importance. This is due to the fact that the combustion chamber of such engine is so small and therefore, there is little time for fuel and air mixture to be present in the chamber. Hence, failed starts or repetitive attempts by the electric starter are very likely due to non-formation of the initial combustion. Also, the performance of the turbine start-up, impressively affects the limited life time of the micro jet engine. In this paper, an experimental study on the injection of compressed air during the start-up of a micro jet engine to improve its performance has been conducted. For this purpose, test components’ layout and a monitoring system are designed. The allowable pressure of the air injection has been calculated using both the engine dynamic model and experimental tests. The simulation results have also been compared and validated with the experimental test results. Finally, several tests were conducted to study the injection process of the compressed air form which, several results have been deduced including the reduction of maximum exhaust gas temperature (EGT) during the start-up, reduction of the start-up time interval and service lifetime enhancement. The method proposed in this paper is applicable on any micro jet engine with the similar structural form and starting process.