Modeling and control of a small turbo jet engine

Low performance gas turbine engines are widely used in; radio controlled planes, unmanned aerial vehicles, and various air platforms. Gas turbines have high performance variations like; turbo prop, turbo jet and ramjet. Turbo jet engines have advantages considering their small size and high performance. However, they are not so efficient due to the high fuel consumption rate. The turbo jet engine that was used in this thesis work whad been chosen as JetCentral Cheetah kero start version. Cheetah has a single stage compressor and single stage turbine. Thesis includes; modeling, analysis, working sequence, control procedure and test bench running of turbo jet engine with single stage compressor and turbine. Context of this thesis involves derivation and analysis of a mathematical model for JetCentral Cheetah turbo jet engines and fuel supply systems. Matlab Simulink and SimPowerSystems toolboxes are used to represent a turbo jet engine model with asingle stage compressor and turbine. Turbo jet engines consist of certain elements like inlet, compressor, burner, turbine and nozzle. Mathematical modeling of every single component and rotor dynamics are connected to each other with dynamic equations. Derived models are implemented and controlled in a computer simulation software. In order to get full coverage modeling; conservation of contiunity, conservation of momentum, conservation of energy and state equations were derived. Addition to that, non-dimensional parameters were used to get behavioral imitation of compressor and türbine. Using the model and the controller, a test bench is installed and carried on to improve the model and perform the system procedure. At the first chapter of this thesis, general indications and definitions about workare explained. Motivation and reason behind this work, previous works about modeling and control of turbo jet engines from literature, commonly faced problems and recent acknowledgements are briefly mentioned. Second chapter includes; types of jet engines and their principles of work. Components of the engine like inlet, compressor, burner, turbine and nozzle are described. Chapter Two also explains working procedure of JetCentral Cheetah and its technical specifications. Controller design of such engine can lead to a couple of certain problems. Design decisions and control requirements in order to minimize real time performance of the engine and fuel supply system arereported. Next chapter includes modeling of turbo jet engine and fuel supply system. Two modeling techniques were used for each system and better simulation results were acquired by component wise modeling. Experimantally obtained compressor and turbine maps are examined in order to analyze pressure ratios, mass flows and efficiency contours. Beta line methods are used to get the data where minimum value of the beta lines is zero and maximum value of the lines are one. Interpolation algorithms are developed and beta line numbers were set to 10 to 12. Beta lines generally are parallel to each other. However; in this thesis context, parabolic beta lines were preferred. Lines can be considered as imaginary axis which helps the interpolation algorithm to calculate pressure ratio, mass flow and efficiency values without having uncertain functions. This mathematical trick, force functions to take singular solutions. Component wise mathematical model of the engine and the fuel supply system are controlled and analyzed in next chapter. By using Model-in-the-Loop simulation type, it is possible to manipulate the simulated system to get accurate results in the real system. Analyzing the transient behavior of the system helped to limit the engine to get it to work at certain working envelopes. In this chapter, modeling techniques were discussed and performance of the controller was confirmed. Test runs were started as a test bench was designed and installed. Microcontroller is synchronouslycontrolling; fuel pump, glow plug, main fuel line valve, ignition line valve and windmilling BLDC motor. At the last chapter of the thesis, model and acquired data are analyzed. Component wise system model plots were presented such as; compressor output pressure, corrected pressure ratio of the compressor, corrected flow rate of the compressor, compressor efficiency, fuel mass flow, burner mass flow, burner input temperature, burner output temperature, nozzle input pressure, nozzle output pressure and net thrust. Using xPC Target, a component wise model is implemented into aSimulink real-time Hardware-in-the-Loop simulator, and tested with fuel supply system in order to tune parameters in simulation model. Thesis work could be turned into fully functional compact electronic control unit for JetCentral Cheetah turbo jet engine. Considering the dynamic behavior of the turbo jet engine, instead of limit controller and PI controller one can develop a fuzzy logic or adaptive controller.Comments about achievements and future work are discussed in the last chapter. At the appendix section, compressor and turbine characteristics are demonstrated and prominent graphs are presented. Selnder's stage compressor model is also can be found at this section. As a continuation of compressor and turbine characteristics section, components in the test bench of the JetCentral turbo jet engine are visually shown.