Differences

This shows you the differences between two versions of the page.

--- aircraft:tmd:turbo_engines [2021/02/12 12:48] – jh
+++ aircraft:tmd:turbo_engines [2022/08/02 10:00] (current) – jh
@@ Line 27: / Line 27: @@
 <code>            <[input_lever][Throttle1Input][]
-                <[string8][Input][Controls.Throttle1]>
+                <[string8][Message][Controls.Throttle1]>
             >
             <[turbofan][Engine1][]
@@ Line 73: / Line 73: @@
 <code>            // engine controls
             <[input_lever][Throttle1Input][]
-                <[string8][Input][Controls.Throttle1]>
+                <[string8][Message][Controls.Throttle1]>
             >
             <[constant][Reverser1Flaps][]
@@ Line 447: / Line 447: @@
 | **Fuel flow** | Reduce efficiencies of the turbines, consider increasing friction, decrease thermal efficiency by making the core larger and less hot. |
 | **Thrust** | Check engine, fan and compressor pressure ratio. When EPR or fan PR below 1.5 decrease nozzle area of affected section. When OPR less than design value (and N2 at target) decrease LP turbine area and IP/LP turbine and increase compressor design compression areas (to keep N2 the same). When all is well but ITT/EGT is cold then consider making engine more efficient by making it run hotter. |
-==== Step 6 - Profit ====
+==== Step 6 - Engine control (FADEC) ====
+Turbo-engines in real life are often controlled by full authority digital engine controllers (FADECs). These take sensor readings from the engine, air data computers, thrust lever angle and other inputs to compute the required engine fuel flow.
+For a very basic fuel controller you can implement a fuel flow proportional to the compressor output pressure and add a governor proportional to the speed deviation. Do something similar like this in the tmd:
+<code>Governor = C_Gov * ( TargetN1 - N1 )
+Enrichment = Engine1Station3.OutputTotalPressure / ( PitotTube.StaticPressure * DesignCompressionRatio ).
+Gain = PitotTube.StaticPressure / 101325.0
+FuelFlowRaw = Gain * C_FF * ( Governor + Enrichment )
+FuelFlow = clamp( FuelFlowRaw, MinFuelFlow, MaxFuelFlow )</code>
+where C_Gov is your governor gain (about 0.2 is ok), and C_FF is your fuel flow constant, use your maximum takeoff fuel flow at the beginning. MinFuelFlow is your idle fuel flow at high altitude (high enough to prevent flame out) and MaxFuelFlow is your takeoff fuel flow plus a small amount. DesignCompressionRatio is the compression ratio that you see at takeoff power (depending on the engine data, ranges between like 11 to 42).