Università del Salento - FACOLTA’ DI INGEGNERIA INDUSTRIALE – Brindisi Dipartimento di Ingegneria dell’Innovazione - Lecce CORSO DI LAUREA SPECIALISTICA IN Ingegneria Aerospaziale PROPULSIONEPROPULSIONE AEROSPAZIALEAEROSPAZIALE II ENGINEENGINE CONTROLS CONTROLS App. O AIAA AIRCRAFT ENGINE DESIGN www.amazon.com LA DISPENSA E’ DISPONIBILE SU http://www.ingindustriale.unisalento.it/didattica/ Prof. Ing. A. Ficarella [email protected] 1 Università del Salento - FACOLTA’ DI INGEGNERIA INDUSTRIALE – Brindisi Dipartimento di Ingegneria dell’Innovazione - Lecce potential of unstable behavior fan or compressor surge/stall primary functions of the engine control maintain stable thrust smooth repeatable performance during transient stable airflow, pressure, temperature and rotor speed avoid stall/surge and significant T, p or speed variations secondary functions startup and shutdown bleed and power extraction inlet anti-icing hot-gas protection tip clearance control 2 Università del Salento - FACOLTA’ DI INGEGNERIA INDUSTRIALE – Brindisi Dipartimento di Ingegneria dell’Innovazione - Lecce difficulty in direct measuring mass flow thrust must be inferred to relate engine thrust to the engine operating line on a fan map mechanical rotor speeds are easily measured the fan rotor speed N1, corrected for inlet T and p, correlates very well to engine mass flow a differential pressure measurement correlates very well with fluid velocities 3 Università del Salento - FACOLTA’ DI INGEGNERIA INDUSTRIALE – Brindisi Dipartimento di Ingegneria dell’Innovazione - Lecce fan rotor speed N1 and engine pressure ratio EPR correlate to the two most significant variables in the equation of the uninstalled thrust lines of EPR are roughly parallel to the fan stall line - stability lines of Tt4 relate to fan inlet corrected airflow and fan pressure ratio – overtemperature protection 4 Università del Salento - FACOLTA’ DI INGEGNERIA INDUSTRIALE – Brindisi Dipartimento di Ingegneria dell’Innovazione - Lecce periodically, the engine controls would have to be trimmed for loss of performance trimless control modes with trimless control modes thrust regulation will be maintained as the engine degrades, but at the expense of increase turbine inlet temperature 5 Università del Salento - FACOLTA’ DI INGEGNERIA INDUSTRIALE – Brindisi Dipartimento di Ingegneria dell’Innovazione - Lecce min fan pressure ratio, below which combustion cannot occur min inlet airflow to sustain continuous operation 6 Università del Salento - FACOLTA’ DI INGEGNERIA INDUSTRIALE – Brindisi Dipartimento di Ingegneria dell’Innovazione - Lecce CONTROL LOGIC AND PROCESSING output command are sent on to the actuators DIGITAL ELECTRONIC CONTROLLER PLA – power level position – throttle position coupled with inlet T and p (altitude and Mach n.) other inputs OUTPUT – thrust requested – required fan rotor speed and engine pressure ratio 7 Università del Salento - FACOLTA’ DI INGEGNERIA INDUSTRIALE – Brindisi Dipartimento di Ingegneria dell’Innovazione - Lecce open-loop and closed-loop control elements OPEN-LOOP variable geometry stator vanes compressor bleed flow CLOSED LOOP fuel flow 8 Università del Salento - FACOLTA’ DI INGEGNERIA INDUSTRIALE – Brindisi Dipartimento di Ingegneria dell’Innovazione - Lecce BASIC DYNAMIC polar moment of inertia of each rotor – dominant effect volume of the afterburner tailpipe there is a weak coupling between the tailpipe pressure and fan rotor speed the two closed-loop control functions can be viewed as independent the main engine fuel flow will control fan rotor speed the exhaust nozzle area will control engine pressure ratio 9 Università del Salento - FACOLTA’ DI INGEGNERIA INDUSTRIALE – Brindisi Dipartimento di Ingegneria dell’Innovazione - Lecce 10 Università del Salento - FACOLTA’ DI INGEGNERIA INDUSTRIALE – Brindisi Dipartimento di Ingegneria dell’Innovazione - Lecce 11 Università del Salento - FACOLTA’ DI INGEGNERIA INDUSTRIALE – Brindisi Dipartimento di Ingegneria dell’Innovazione - Lecce In control theory, the root locus is the locus of the poles and zeros of a transfer function as the system gain K is varied on some interval. The root locus is a useful tool for analyzing single input single output (SISO) linear dynamic systems. A system is stable if all of its poles are in the left-hand side of the s-plane (for continuous systems) or inside the unit circle of the z-plane (for discrete systems). In complex analysis, a pole of a meromorphic function is a certain type of singularity that behaves like the singularity 1/zn at z = 0. This means that, in particular, a pole of the function f(z) is a point z = a such that f(z) approaches infinity uniformly as z approaches a. 12 Università del Salento - FACOLTA’ DI INGEGNERIA INDUSTRIALE – Brindisi Dipartimento di Ingegneria dell’Innovazione - Lecce rotor inertia determines the dynamic response for a large diameter engine acceleration may take 10 s for a turbojet 1-2 s to accelerate the engine quickly, the fuel flow should be raised quickly raising fuel flow too rapidly could cause an engine overtemperature or stall 13 Università del Salento - FACOLTA’ DI INGEGNERIA INDUSTRIALE – Brindisi Dipartimento di Ingegneria dell’Innovazione - Lecce rapid acceleration require the engine to operate transiently very closed to stall line the variable geometry vanes will be positioned to follow a prescribed schedule high frequency aerodynamic instabilities – blade flutter 14 Università del Salento - FACOLTA’ DI INGEGNERIA INDUSTRIALE – Brindisi Dipartimento di Ingegneria dell’Innovazione - Lecce ADVANCED CONTROL LOGIC to recapture the loss performance by actively controlling the stall margin MODEL-BASED CONTROL 15 Università del Salento - FACOLTA’ DI INGEGNERIA INDUSTRIALE – Brindisi Dipartimento di Ingegneria dell’Innovazione - Lecce detailed non-linear simulation of the engine tracking filter to take comparison between model outputs and sensor reading to adjust the model parameters 16 Università del Salento - FACOLTA’ DI INGEGNERIA INDUSTRIALE – Brindisi Dipartimento di Ingegneria dell’Innovazione - Lecce CONTROL SYSTEM COMPONENTS ELECTRICAL SUBSYSTEMS FADEC – full authority digital electronic control redundancy requiements FUEL DELIVERY SUBSISTEM 17 Università del Salento - FACOLTA’ DI INGEGNERIA INDUSTRIALE – Brindisi Dipartimento di Ingegneria dell’Innovazione - Lecce ACTUATION SUBSISTEM 18 Università del Salento - FACOLTA’ DI INGEGNERIA INDUSTRIALE – Brindisi Dipartimento di Ingegneria dell’Innovazione - Lecce A FADEC is a system consisting of a digital computer, called an Electronic Engine Control (EEC) or Electronic Control Unit (ECU), and its related accessories that control all aspects of aircraft engine performance. The term FADEC is an acronym for either Full Authority Digital Engine Control or Full Authority Digital Electronics Control. FADECs have been produced for both piston engines and jet engines, their primary difference due to the different ways of controlling the engines. 19 Università del Salento - FACOLTA’ DI INGEGNERIA INDUSTRIALE – Brindisi Dipartimento di Ingegneria dell’Innovazione - Lecce Function To be a true, 100%, Full Authority Digital Engine Control, there must not be any form of manual override available. This literally places full authority to the operating parameters of the engine in the hands of the computer. If a total FADEC failure occurs, the engine fails. If the engine is controlled digitally and electronically but allows for manual override, it is considered solely an Electronic Engine Control or Electronic Control Unit. An EEC, though a component of a FADEC, is not by itself FADEC. When standing alone, the EEC makes all of the decisions until the pilot wishes to intervene. FADEC works by receiving multiple input variables of the current flight condition including air density, throttle lever position, engine temperatures, engine pressures, and many others. The inputs are received by the EEC and analyzed up to 70 times per second. Engine operating parameters such as fuel flow, stator vane position, bleed valve position, and others are computed from this data and applied as appropriate. FADEC also controls engine starting and restarting. The FADEC's basic purpose is to provide optimum engine efficiency for a given flight condition. FADEC not only provides for efficient engine operation, it also allows the manufacturer to program engine limitations and receive engine health and maintenance reports. For example, to avoid exceeding a certain engine temperature, the FADEC can be programmed to automatically take the necessary measures without pilot intervention. 20 Università del Salento - FACOLTA’ DI INGEGNERIA INDUSTRIALE – Brindisi Dipartimento di Ingegneria dell’Innovazione - Lecce Safety With the operation of the engines so heavily relying on automation, safety is a great concern. Redundancy is provided in the form of two or more, separate identical digital channels. Each channel may provide all engine functions without restriction. FADEC also monitors a variety of analog, digital and discrete data coming from the engine subsystems and related aircraft systems, providing for fault tolerant engine control. 21 Università del Salento - FACOLTA’ DI INGEGNERIA INDUSTRIALE – Brindisi Dipartimento di Ingegneria dell’Innovazione - Lecce Application To perhaps more clearly illustrate the function of a FADEC, explore a typical civilian transport aircraft flight. The flight crew first enters the data appropriate to the