refactoring (broken right now)
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@@ -1,249 +0,0 @@
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using System;
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using FluidSim.Components;
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namespace FluidSim.Core
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{
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public class EngineCylinder
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{
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public Volume0D Cylinder { get; private set; }
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private Crankshaft crankshaft;
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private double bore, stroke, conRodLength, compressionRatio;
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private double pistonArea;
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public double V_disp { get; private set; }
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public double V_clear { get; private set; }
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public bool ignition = false;
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// ---- Exhaust valve ----
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private double exhMaxOrificeArea;
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private double exhValveOpenStart = 130.0 * Math.PI / 180.0;
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private double exhValveOpenEnd = 390.0 * Math.PI / 180.0;
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private double exhValveRampWidth = 30.0 * Math.PI / 180.0;
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public double ExhaustOrificeArea => ExhaustValveLift() * exhMaxOrificeArea;
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public double ExhaustValveLiftCurrent => ExhaustValveLift();
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// ---- Intake valve ----
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private double intMaxOrificeArea;
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private double intValveOpenStart = 340.0 * Math.PI / 180.0;
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private double intValveOpenEnd = 600.0 * Math.PI / 180.0;
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private double intValveRampWidth = 30.0 * Math.PI / 180.0;
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public double IntakeOrificeArea => IntakeValveLift() * intMaxOrificeArea;
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public double IntakeValveLiftCurrent => IntakeValveLift();
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// ---- Combustion ----
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public double TargetPeakPressure { get; set; } = 50.0 * 101325.0;
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private const double PeakTemperature = 2500.0;
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private bool burnInProgress = false;
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private double burnStartAngle; // cycle angle (0–4π)
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private double burnDuration = 40.0 * Math.PI / 180.0;
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private double targetBurnEnergy;
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private double preIgnitionMass, preIgnitionInternalEnergy;
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private Random rand = new Random();
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public double MisfireProbability { get; set; } = 0.02;
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private bool misfireCurrent = false;
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public int CombustionCount { get; private set; }
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public int MisfireCount { get; private set; }
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// Cycle‑aware angle (0 – 4π)
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public double CycleAngle => crankshaft.CrankAngle % (4.0 * Math.PI);
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private double prevCycleAngle;
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// Piston position fraction (0 = TDC, 1 = BDC)
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public double PistonPositionFraction
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{
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get
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{
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double currentVol = Cylinder.Volume;
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if (currentVol <= V_clear) return 0.0;
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if (currentVol >= V_clear + V_disp) return 1.0;
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return (currentVol - V_clear) / V_disp;
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}
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}
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public EngineCylinder(Crankshaft crankshaft,
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double bore, double stroke, double compressionRatio,
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double exhPipeArea, double intPipeArea, int sampleRate)
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{
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this.crankshaft = crankshaft;
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this.bore = bore;
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this.stroke = stroke;
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conRodLength = 2.0 * stroke;
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this.compressionRatio = compressionRatio;
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exhMaxOrificeArea = exhPipeArea * 0.5;
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intMaxOrificeArea = intPipeArea * 0.5;
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pistonArea = Math.PI / 4.0 * bore * bore;
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V_disp = pistonArea * stroke;
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V_clear = V_disp / (compressionRatio - 1.0);
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// Start at BDC with fresh ambient charge
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double V_bdc = V_clear + V_disp;
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double p_amb = 101325.0;
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double T_amb = 300.0;
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double rho0 = p_amb / (287.0 * T_amb);
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double mass0 = rho0 * V_bdc;
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double energy0 = p_amb * V_bdc / (1.4 - 1.0);
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Cylinder = new Volume0D(V_bdc, p_amb, T_amb, sampleRate)
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{
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Gamma = 1.4,
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GasConstant = 287.0
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};
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Cylinder.Volume = V_bdc;
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Cylinder.Mass = mass0;
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Cylinder.InternalEnergy = energy0;
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prevCycleAngle = CycleAngle;
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preIgnitionMass = Cylinder.Mass;
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preIgnitionInternalEnergy = Cylinder.InternalEnergy;
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}
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// ---- Piston kinematics ----
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private (double volume, double dvdt) PistonKinematics(double cycleAngle)
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{
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double theta = cycleAngle % (2.0 * Math.PI);
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double R = stroke / 2.0;
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double cosT = Math.Cos(theta);
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double sinT = Math.Sin(theta);
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double L = conRodLength;
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double s = R * (1 - cosT) + L - Math.Sqrt(L * L - R * R * sinT * sinT);
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double V = V_clear + pistonArea * s;
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double sqrtTerm = Math.Sqrt(L * L - R * R * sinT * sinT);
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double dVdθ = pistonArea * (R * sinT + (R * R * sinT * cosT) / sqrtTerm);
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double dvdt = dVdθ * crankshaft.AngularVelocity;
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return (V, dvdt);
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}
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// ---- Valve lifts (cycle‑aware) ----
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private double ExhaustValveLift()
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{
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double a = CycleAngle;
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if (a < exhValveOpenStart || a > exhValveOpenEnd) return 0.0;
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double duration = exhValveOpenEnd - exhValveOpenStart;
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double ramp = exhValveRampWidth;
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double t = (a - exhValveOpenStart) / duration;
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double rampFrac = ramp / duration;
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if (t < rampFrac) return t / rampFrac;
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if (t > 1.0 - rampFrac) return (1.0 - t) / rampFrac;
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return 1.0;
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}
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private double IntakeValveLift()
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{
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double a = CycleAngle;
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if (a < intValveOpenStart || a > intValveOpenEnd) return 0.0;
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double duration = intValveOpenEnd - intValveOpenStart;
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double ramp = intValveRampWidth;
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double t = (a - intValveOpenStart) / duration;
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double rampFrac = ramp / duration;
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if (t < rampFrac) return t / rampFrac;
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if (t > 1.0 - rampFrac) return (1.0 - t) / rampFrac;
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return 1.0;
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}
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// ---- Wiebe burn fraction ----
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private double WiebeFraction(double angleFromIgnition)
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{
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if (angleFromIgnition >= burnDuration) return 1.0;
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double a = 5.0, m = 2.0;
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double x = angleFromIgnition / burnDuration;
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return 1.0 - Math.Exp(-a * Math.Pow(x, m + 1));
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}
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// ---- Torque from pressure ----
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private double ComputeTorque()
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{
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double p = Cylinder.Pressure;
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double ambient = 101325.0;
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double force = (p - ambient) * pistonArea;
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if (force <= 0) return 0.0;
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double theta = crankshaft.CrankAngle % (2.0 * Math.PI);
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double R = stroke / 2.0;
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double L = conRodLength;
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double sinT = Math.Sin(theta);
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double cosT = Math.Cos(theta);
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double sqrtTerm = Math.Sqrt(L * L - R * R * sinT * sinT);
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double lever = R * sinT * (1.0 + (R * cosT) / sqrtTerm);
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return force * lever;
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}
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// ---- TDC detection (power stroke, at angle 0 mod 4π) ----
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private bool DetectTDCPowerStroke()
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{
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double current = CycleAngle;
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double previous = prevCycleAngle;
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prevCycleAngle = current;
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return (previous > 3.8 * Math.PI && current < 0.2 * Math.PI);
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}
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public void Step(double dt)
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{
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bool crossingTDC = DetectTDCPowerStroke();
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if (crossingTDC)
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{
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misfireCurrent = rand.NextDouble() < MisfireProbability;
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// *** Always capture the state at TDC, whether we burn or not ***
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preIgnitionMass = Cylinder.Mass;
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preIgnitionInternalEnergy = Cylinder.InternalEnergy;
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if (misfireCurrent)
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{
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MisfireCount++;
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}
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else if (ignition)
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{
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double V = Cylinder.Volume;
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targetBurnEnergy = TargetPeakPressure * V / (Cylinder.Gamma - 1.0);
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if (double.IsNaN(targetBurnEnergy))
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targetBurnEnergy = 101325.0 * V / (Cylinder.Gamma - 1.0);
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burnInProgress = true;
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burnStartAngle = CycleAngle;
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CombustionCount++;
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}
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}
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if (burnInProgress)
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{
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double angleFromIgnition = CycleAngle - burnStartAngle;
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if (angleFromIgnition < 0) angleFromIgnition += 4.0 * Math.PI;
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if (angleFromIgnition >= burnDuration)
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{
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Cylinder.InternalEnergy = targetBurnEnergy;
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burnInProgress = false;
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}
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else
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{
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double fraction = WiebeFraction(angleFromIgnition);
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Cylinder.InternalEnergy = preIgnitionInternalEnergy * (1.0 - fraction)
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+ targetBurnEnergy * fraction;
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Cylinder.Mass = preIgnitionMass;
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}
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}
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var (vol, dvdt) = PistonKinematics(CycleAngle);
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Cylinder.Volume = vol;
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Cylinder.Dvdt = dvdt;
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if (double.IsNaN(Cylinder.Pressure) || double.IsNaN(Cylinder.Temperature) || Cylinder.Mass < 1e-9)
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{
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double V = Math.Max(vol, V_clear);
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Cylinder.Mass = 1.225 * V;
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Cylinder.InternalEnergy = 101325.0 * V / (1.4 - 1.0);
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}
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double torque = ComputeTorque();
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crankshaft.AddTorque(torque);
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}
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}
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}
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