4세대 LFR 납-비스무트(LBE) 액체금속 부식 & 1,000Hz 0-Alloc C# 산소농도 열역학 평형 서보 엔진

using System;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

namespace ZeliDesk.Stem.LiquidMetalControl
{
    /// <summary>
    /// LBE 냉각재 계측 센서 데이터 (스택 할당 0-Alloc)
    /// </summary>
    [StructLayout(LayoutKind.Sequential, Pack = 8)]
    public readonly struct LbeCoolantSensorData
    {
        public readonly double CoolantTemperatureC; // LBE 온도 (도C)
        public readonly double YszSensorEmfMilliVolts; // 센서 기전력 (mV)
        public readonly double FlowRateKgS;           // LBE 질량 유량 (kg/s)

        public LbeCoolantSensorData(double tempC, double emfMv, double flow)
        {
            CoolantTemperatureC = tempC;
            YszSensorEmfMilliVolts = emfMv;
            FlowRateKgS = flow;
        }
    }

    /// <summary>
    /// 산소 조절 가스 주입 명령
    /// </summary>
    public ref struct OxygenGasInjectionCommand
    {
        public double ReducingGasFlowSccm; // Ar-H2 환원 가스 유량 (sccm)
        public double OxidizingGasFlowSccm;// Ar-O2 산소 가스 유량 (sccm)
        public double CurrentOxygenConcentrationWtPercent;
        public int CorrosionZoneStatus; // -1: 용해 부식(산소부족), 0: 안정 산화막, +1: PbO 석출(산소과다)

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public OxygenGasInjectionCommand(double h2Flow, double o2Flow, double cO, int status)
        {
            ReducingGasFlowSccm = h2Flow;
            OxidizingGasFlowSccm = o2Flow;
            CurrentOxygenConcentrationWtPercent = cO;
            CorrosionZoneStatus = status;
        }
    }

    /// <summary>
    /// 1,000Hz 무할당 LBE 산소 농도 제어 서보 엔진
    /// </summary>
    public ref struct LbeOxygenControlEngine
    {
        private const double GasConstantR = 8.314462618;
        private const double FaradayConstantF = 96485.33212;

        private double _logOxygenIntegral;

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public void ExecuteControlCycle(
            in LbeCoolantSensorData sensor,
            out OxygenGasInjectionCommand command)
        {
            double tempK = sensor.CoolantTemperatureC + 273.15;

            // 1. YSZ 센서 전압으로부터 LBE 내 산소 활량 및 농도(wt%) 역산
            // E = (R*T / 2*F) * ln(a_ref / a_LBE) -> Bi/Bi2O3 기준전극 상수 적용
            double emfVolts = sensor.YszSensorEmfMilliVolts * 1.0e-3;
            double logActivity = - (2.0 * FaradayConstantF * emfVolts) / (GasConstantR * tempK);
            double activityO = Math.Exp(Math.Clamp(logActivity, -25.0, 5.0));

            // 용해도 법칙 (wt% = S_0 * exp(-H/RT) * a_O)
            double logSolubility = 1.2 - 9111.0 / tempK;
            double oxygenConcentration = Math.Pow(10.0, logSolubility) * activityO;
            oxygenConcentration = Math.Clamp(oxygenConcentration, 1.0e-10, 1.0e-2);

            // 2. 최적 산소 윈도우 계산 (Fe3O4 안정 형성 하한 ~ PbO 석출 상한)
            double lowerLimitLog = -14.2 + 2500.0 / tempK;
            double upperLimitLog = -7.8 + 1200.0 / tempK;
            double targetLog = 0.5 * (lowerLimitLog + upperLimitLog);

            double currentLog = Math.Log10(oxygenConcentration);
            double logError = targetLog - currentLog;
            _logOxygenIntegral += logError * 0.001;

            // 3. 상태 판별 및 PI 제어 출력 산출
            int status = 0;
            double flowH2 = 0.0;
            double flowO2 = 0.0;

            if (currentLog < lowerLimitLog)
            {
                status = -1; // 위험: 산소 부족으로 모재 Fe/Cr 용출 부식
                flowO2 = Math.Clamp(50.0 + (lowerLimitLog - currentLog) * 80.0, 0.0, 250.0);
                flowH2 = 0.0;
            }
            else if (currentLog > upperLimitLog)
            {
                status = 1; // 위험: 산소 과다로 냉각재 내 PbO 슬래그 침전
                flowH2 = Math.Clamp(50.0 + (currentLog - upperLimitLog) * 80.0, 0.0, 250.0);
                flowO2 = 0.0;
            }
            else
            {
                status = 0; // 정상: 안정적인 FeCr2O4 스피넬 산화막 유지
                double correction = 25.0 * logError + 5.0 * _logOxygenIntegral;
                if (correction > 0) flowO2 = Math.Clamp(correction, 0.0, 40.0);
                else flowH2 = Math.Clamp(-correction, 0.0, 40.0);
            }

            command = new OxygenGasInjectionCommand(flowH2, flowO2, oxygenConcentration, status);
        }
    }
}