350 lines
17 KiB
C#
350 lines
17 KiB
C#
using FluidSim.Components;
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using FluidSim.Core;
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using FluidSim.Interfaces;
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using FluidSim.Utils;
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using SFML.Graphics;
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using SFML.System;
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using System;
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namespace FluidSim.Tests
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{
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public class TwoStrokeScenario : Scenario
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{
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private Crankshaft crankshaft;
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private TwoStrokeCylinder cylinder;
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private PipeSystem pipeSystem;
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private BoundarySystem boundaries;
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private Solver solver;
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private Volume0D intakePlenum;
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private Port plenumInlet, plenumOutlet;
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private Volume0D exhaustMuffler;
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private Port mufflerIn, mufflerOut;
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private Vehicle vehicle;
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private int throttleAreaIdx, plenumRunnerIdx, intakeValveIdx, exhaustValveIdx;
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private float[] orificeAreas;
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private int intakeOpenIdx, exhaustOpenIdx;
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private SoundProcessor exhaustSound, intakeSound;
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private OutdoorExhaustReverb reverb;
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private double dt;
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private int stepCount;
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private float _maxThrottleArea;
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private float intakePipeArea, exhaustHeaderArea;
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public override void ShiftUp() => vehicle.ShiftUp();
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public override void ShiftDown() => vehicle.ShiftDown();
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public override void Initialize(int sampleRate)
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{
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dt = 1.0 / sampleRate;
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// ── Vehicle ──────────────────────────────────────────────────────────
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vehicle = new Vehicle();
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// ── Throttle body: 42 mm – wider to reduce high-RPM intake restriction ──
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_maxThrottleArea = (float)Units.AreaFromDiameter(42 * Units.mm);
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// ── Crankshaft ───────────────────────────────────────────────────────
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// Lighter flywheel for quicker revving; friction tuned to ~0.5 kW loss at idle
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crankshaft = new Crankshaft(2000);
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crankshaft.CycleLength = 2f * MathF.PI; // two-stroke: fire every rev
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crankshaft.Inertia = 0.06f; // lighter flywheel
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crankshaft.FrictionConstant = 0.4f; // ~0.4 Nm constant drag
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crankshaft.FrictionViscous = 0.0004f; // ~2.5 Nm at 10 000 RPM
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// ── Cylinder: 125 cc, motocross-style two-stroke ─────────────────────
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// Bore × stroke = 54 × 54.5 mm → 124.9 cc
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float bore = 0.054f;
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float stroke = 0.0545f;
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float conRod = 0.110f; // ~2× stroke
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float compRatio = 7.2f; // geometric CR; effective CR after port closure is ~12:1
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// Port timings: exhaust 195°, transfer 155° – competitive MX 125
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float transferDuration = 155f;
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float exhaustDuration = 195f;
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cylinder = new TwoStrokeCylinder(bore, stroke, conRod, compRatio,
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transferDuration, exhaustDuration,
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crankshaft)
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{
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IntakeValveDiameter = 0.042f, // matched to intake pipe
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IntakeValveLift = 0.015f,
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ExhaustValveDiameter = 0.040f,
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ExhaustValveLift = 0.013f
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};
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// ── Pipe geometry ────────────────────────────────────────────────────
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//
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// Layout (all lengths in mm):
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// Intake path: airbox stub 100 mm | runner 180 mm
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// Exhaust path: expansion chamber tuned to ~9 000 RPM power peak
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// header 170 mm Ø 40 mm
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// diffuser 280 mm Ø 40 → 72 mm
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// belly 200 mm Ø 72 mm
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// convergent 130 mm Ø 72 → 28 mm
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// stinger 70 mm Ø 28 mm
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// total 850 mm
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//
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// Cell sizing: ~14 mm/cell.
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// CFL: c_sound ≈ 550 m/s, dx=0.014 m → dt_max ≈ 25 µs
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// at 44100 Hz dt = 22.7 µs → SubStepCount=4 keeps CFL safely ≤ 1
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// --- Cell counts ---
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int intakeCells = 7; // 100 mm stub → ~14 mm/cell
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int runnerCells = 13; // 180 mm runner → ~14 mm/cell
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int exhaustCells = 60; // 850 mm total → ~14 mm/cell
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int totalCells = intakeCells + runnerCells + exhaustCells;
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int[] pipeStart = { 0, intakeCells, intakeCells + runnerCells };
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int[] pipeEnd = { intakeCells, intakeCells + runnerCells, totalCells };
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float[] area = new float[totalCells];
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float[] dx = new float[totalCells];
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// --- Intake ---
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float intakeDia = 0.042f; // matches throttle body
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float intakeStubLen = 0.100f;
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float intakeRunnerLen= 0.160f; // shorter runner → less pumping loss
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intakePipeArea = MathF.PI * 0.25f * intakeDia * intakeDia;
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for (int i = 0; i < intakeCells; i++)
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{ area[i] = intakePipeArea; dx[i] = intakeStubLen / intakeCells; }
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for (int i = intakeCells; i < intakeCells + runnerCells; i++)
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{ area[i] = intakePipeArea; dx[i] = intakeRunnerLen / runnerCells; }
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// Expansion chamber tuned for ~8 500 RPM power peak.
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// Return-pulse travel distance = 0.5 × c_avg × (60 / RPM_target)
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// c_avg ≈ 480 m/s → distance = 0.5 × 480 × (60/8500) ≈ 1.69 m round-trip
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// → one-way pipe length ≈ 0.84 m (matches total below)
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float headerDia = 0.040f; float headerLen = 0.130f; // shorter header → earlier pulse
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float diffEndDia = 0.070f; float diffuserLen = 0.250f; // slightly narrower belly
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float bellyDia = 0.070f; float bellyLen = 0.220f;
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float convEndDia = 0.028f; float convergentLen= 0.160f; // longer convergent → stronger return pulse
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float stingerDia = 0.028f; float stingerLen = 0.080f;
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// total = 0.13+0.25+0.22+0.16+0.08 = 0.84 m
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exhaustHeaderArea = MathF.PI * 0.25f * headerDia * headerDia;
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float bellyArea = MathF.PI * 0.25f * bellyDia * bellyDia;
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float stingerArea = MathF.PI * 0.25f * stingerDia * stingerDia;
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// Distribute cells proportionally by section length
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int headerCells = Math.Max(1, (int)MathF.Round(exhaustCells * headerLen / 0.84f));
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int diffuserCells = Math.Max(1, (int)MathF.Round(exhaustCells * diffuserLen / 0.84f));
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int bellyCells = Math.Max(1, (int)MathF.Round(exhaustCells * bellyLen / 0.84f));
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int convergentCells = Math.Max(1, (int)MathF.Round(exhaustCells * convergentLen/ 0.84f));
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int stingerCells = exhaustCells - headerCells - diffuserCells
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- bellyCells - convergentCells;
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if (stingerCells < 1) stingerCells = 1;
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int exhBase = intakeCells + runnerCells;
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int idx = 0;
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for (int i = exhBase; i < totalCells; i++, idx++)
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{
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if (idx < headerCells)
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{
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area[i] = exhaustHeaderArea;
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dx[i] = headerLen / headerCells;
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}
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else if (idx < headerCells + diffuserCells)
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{
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float t = (idx - headerCells) / (float)(diffuserCells - 1);
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// Smooth cosine taper instead of linear for better wave reflection
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float ct = 0.5f * (1f - MathF.Cos(MathF.PI * t));
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float dia = headerDia + (diffEndDia - headerDia) * ct;
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area[i] = MathF.PI * 0.25f * dia * dia;
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dx[i] = diffuserLen / diffuserCells;
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}
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else if (idx < headerCells + diffuserCells + bellyCells)
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{
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area[i] = bellyArea;
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dx[i] = bellyLen / bellyCells;
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}
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else if (idx < headerCells + diffuserCells + bellyCells + convergentCells)
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{
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float t = (idx - headerCells - diffuserCells - bellyCells)
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/ (float)(convergentCells - 1);
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// Steeper cosine convergent for a sharper return pulse
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float ct = 0.5f * (1f - MathF.Cos(MathF.PI * t));
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float dia = bellyDia + (convEndDia - bellyDia) * ct;
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area[i] = MathF.PI * 0.25f * dia * dia;
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dx[i] = convergentLen / convergentCells;
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}
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else
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{
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area[i] = stingerArea;
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dx[i] = stingerLen / stingerCells;
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}
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}
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pipeSystem = new PipeSystem(totalCells, pipeStart, pipeEnd, area, dx,
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1.225f, 0f, 101325f);
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pipeSystem.DampingMultiplier = 0.8f; // slightly less damping → stronger pulses
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pipeSystem.EnergyRelaxationRate = 0.4f;
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pipeSystem.AmbientPressure = 101325f;
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// ── 0-D Volumes ──────────────────────────────────────────────────────
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// Intake plenum: acts as a small airbox resonator (8 cc)
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intakePlenum = new Volume0D(8e-3f, 101325f, 300f);
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plenumInlet = intakePlenum.CreatePort();
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plenumOutlet = intakePlenum.CreatePort();
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// Exhaust silencer volume: 600 cc is realistic for a small-bore muffler
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exhaustMuffler = new Volume0D(600e-6f, 101325f, 650f);
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mufflerIn = exhaustMuffler.CreatePort();
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mufflerOut = exhaustMuffler.CreatePort();
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// ── Boundary system ───────────────────────────────────────────────────
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boundaries = new BoundarySystem(pipeSystem, maxOrifices: 4, maxOpenEnds: 2);
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throttleAreaIdx = 0;
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plenumRunnerIdx = 1;
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intakeValveIdx = 2;
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exhaustValveIdx = 3;
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// Open ends: atmosphere at both extremes
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boundaries.AddOpenEnd(pipeIndex: 0, isLeftEnd: true, 101325f, intakePipeArea);
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intakeOpenIdx = 0;
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boundaries.AddOpenEnd(pipeIndex: 2, isLeftEnd: false, 101325f, stingerArea);
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exhaustOpenIdx = 1;
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// Orifices: throttle → plenum → runner → cylinder → exhaust pipe
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boundaries.AddOrifice(plenumInlet, 0, false, throttleAreaIdx, 0.72f);
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boundaries.AddOrifice(plenumOutlet, 1, true, plenumRunnerIdx, 1.00f);
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boundaries.AddOrifice(cylinder.IntakePort, 1, false, intakeValveIdx, 0.68f);
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boundaries.AddOrifice(cylinder.ExhaustPort, 2, true, exhaustValveIdx, 0.70f);
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orificeAreas = new float[4];
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orificeAreas[plenumRunnerIdx] = intakePipeArea; // runner always fully open
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// ── Solver ────────────────────────────────────────────────────────────
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// SubStepCount = 4 keeps CFL ≤ 1 for 5 mm cells at 44 100 Hz
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solver = new Solver { SubStepCount = 4, EnableProfiling = false };
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solver.SetTimeStep(dt);
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solver.SetPipeSystem(pipeSystem);
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solver.SetBoundarySystem(boundaries);
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solver.AddComponent(cylinder);
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solver.AddComponent(intakePlenum);
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solver.AddComponent(exhaustMuffler);
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// ── Sound ─────────────────────────────────────────────────────────────
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exhaustSound = new SoundProcessor(sampleRate, 1f) { Gain = 4.5f };
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intakeSound = new SoundProcessor(sampleRate, 1f) { Gain = 4.5f };
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reverb = new OutdoorExhaustReverb(sampleRate);
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stepCount = 0;
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Console.WriteLine("125cc Two-Stroke – expansion chamber tuned for ~8 500 RPM power peak");
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Console.WriteLine($" Exhaust cells: {exhaustCells} | header {headerCells} diffuser {diffuserCells}" +
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$" belly {bellyCells} convergent {convergentCells} stinger {stingerCells}");
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}
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public override float Process()
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{
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float engineRpm = crankshaft.AngularVelocity * 60f / (2f * MathF.PI);
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vehicle.ClutchInput = Clutch;
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var (clutchTorque, effectiveInertia) = vehicle.Update(engineRpm, crankshaft.Inertia, (float)dt);
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crankshaft.SetEffectiveInertia(effectiveInertia);
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crankshaft.SetLoadTorque(clutchTorque);
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crankshaft.Step((float)dt);
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cylinder.PreStep((float)dt);
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float throttledArea = _maxThrottleArea * Math.Clamp(Throttle, 0.001f, 1f);
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orificeAreas[throttleAreaIdx] = throttledArea;
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orificeAreas[intakeValveIdx] = cylinder.IntakeValveArea;
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orificeAreas[exhaustValveIdx] = cylinder.ExhaustValveArea;
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boundaries.SetOrificeAreas(orificeAreas);
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solver.Step();
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stepCount++;
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float exhaustFlow = boundaries.GetOpenEndMassFlow(exhaustOpenIdx);
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float intakeFlow = boundaries.GetOpenEndMassFlow(intakeOpenIdx);
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float exhaustDry = exhaustSound.Process(exhaustFlow);
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float intakeDry = intakeSound.Process(intakeFlow);
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if (stepCount % 2000 == 0)
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{
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float rpm = crankshaft.AngularVelocity * 60f / (2f * MathF.PI);
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float powerKw = crankshaft.AveragePower * 1e-3f;
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float torqueNm = crankshaft.AverageTorque;
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Console.WriteLine($"Step {stepCount,7} | RPM={rpm,6:F0} | Power={powerKw,5:F2} kW" +
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$" | Torque={torqueNm,5:F1} Nm | Gear={vehicle.CurrentGear}" +
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$" | Speed={vehicle.SpeedKmh,4:F0} km/h");
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}
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return reverb.Process((intakeDry + exhaustDry) * 0.5f);
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}
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// ── Drawing ───────────────────────────────────────────────────────────────
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public override void Draw(RenderWindow target)
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{
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float winW = target.GetView().Size.X;
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float winH = target.GetView().Size.Y;
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float intakeY = winH / 2f - 40f;
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float exhaustY = winH / 2f + 80f;
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float openEndX = 40f;
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// Intake stub
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float x = openEndX;
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float w = 120f;
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DrawPipe(target, pipeSystem, 0, intakeY, x, x + w);
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// Throttle body
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float throttleX = x + w + 5f;
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var throttleRect = new RectangleShape(new Vector2f(8f, 30f))
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{
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FillColor = Color.Yellow,
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Position = new Vector2f(throttleX, intakeY - 15f)
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};
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target.Draw(throttleRect);
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// Plenum
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float plenW = 40f, plenH = 60f;
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float plenX = throttleX + 10f;
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DrawVolume(target, intakePlenum, plenX + plenW / 2f, intakeY - plenH / 2f, plenW, plenH);
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// Runner
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float runnerStartX = plenX + plenW + 5f;
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DrawPipe(target, pipeSystem, 1, intakeY, runnerStartX, runnerStartX + 100f);
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// Cylinder
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float cylCX = runnerStartX + 150f;
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float cylTopY = intakeY - 120f;
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DrawCylinder(target, cylinder, cylCX, cylTopY, 80f, 240f);
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// Exhaust pipe (expansion chamber)
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float exhStartX = cylCX + 40f + 20f;
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DrawPipe(target, pipeSystem, 2, exhaustY, exhStartX, winW - 60f, areaScale: 800f);
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// HUD labels
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float rpm = crankshaft.AngularVelocity * 60f / (2f * MathF.PI);
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float powerKw = crankshaft.AveragePower * 1e-3f;
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float torqueNm = crankshaft.AverageTorque;
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DrawLabel(target, $"RPM: {rpm:F0}", new Vector2f(20, 90), Color.White, 24);
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DrawLabel(target, $"Power: {powerKw:F2} kW", new Vector2f(20, 115), Color.White, 24);
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DrawLabel(target, $"Torque: {torqueNm:F1} Nm",new Vector2f(20, 140), Color.White, 20);
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string gearText = vehicle.CurrentGear == 0 ? "N" : vehicle.CurrentGear.ToString();
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DrawLabel(target, $"Gear: {gearText}", new Vector2f(20, 162), Color.Cyan, 20);
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DrawLabel(target, $"Speed: {vehicle.SpeedKmh:F0} km/h",
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new Vector2f(20, 184), Color.Cyan, 20);
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DrawLabel(target, vehicle.Engagement > 0.99f ? "Clutch: Locked" : "Clutch: Slipping",
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new Vector2f(20, 204), Color.Cyan, 14);
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// Dyno curve
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UpdateDynoCurve(rpm, powerKw, torqueNm);
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DrawDynoCurve(target, winW - 410f, winH - 260f, 400f, 250f, rpm, powerKw);
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}
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}
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} |