git.gag.com Git - sw/motorsim/blob - src/com/billkuker/rocketry/motorsim/Burn.java

   1 package com.billkuker.rocketry.motorsim;\r
   2 \r
   3 \r
   4 \r
   5 import java.util.Date;\r
   6 import java.util.SortedMap;\r
   7 import java.util.TreeMap;\r
   8 \r
   9 import javax.measure.quantity.Area;\r
  10 import javax.measure.quantity.Dimensionless;\r
  11 import javax.measure.quantity.Duration;\r
  12 import javax.measure.quantity.Force;\r
  13 import javax.measure.quantity.Length;\r
  14 import javax.measure.quantity.Mass;\r
  15 import javax.measure.quantity.MassFlowRate;\r
  16 import javax.measure.quantity.Pressure;\r
  17 import javax.measure.quantity.Quantity;\r
  18 import javax.measure.quantity.Temperature;\r
  19 import javax.measure.quantity.Velocity;\r
  20 import javax.measure.quantity.Volume;\r
  21 import javax.measure.quantity.VolumetricDensity;\r
  22 import javax.measure.unit.SI;\r
  23 \r
  24 import org.apache.log4j.Logger;\r
  25 import org.jscience.physics.amount.Amount;\r
  26 import org.jscience.physics.amount.Constants;\r
  27 \r
  28 public class Burn {\r
  29         //Some constants to tune adaptive regression step\r
  30         private static final double regStepIncreaseFactor = 1.01;\r
  31         private static final double regStepDecreaseFactor = .5;\r
  32         private static final Amount<Pressure> chamberPressureMaxDelta = Amount.valueOf(.5, SI.MEGA(SI.PASCAL));\r
  33         \r
  34         private static Logger log = Logger.getLogger(Burn.class);\r
  35         protected final Motor motor;\r
  36         \r
  37         public interface BurnProgressListener{\r
  38                 public void setProgress(float p);\r
  39         }\r
  40         \r
  41         private BurnProgressListener bpl = null;\r
  42         \r
  43         private static final Amount<Pressure> atmosphereicPressure = Amount.valueOf(101000, SI.PASCAL);\r
  44         \r
  45         public class Interval{\r
  46                 public Amount<Duration> time;\r
  47                 public Amount<Duration> dt;\r
  48                 public Amount<Length> regression;\r
  49                 public Amount<Pressure> chamberPressure;\r
  50                 Amount<Mass> chamberProduct;\r
  51                 public Amount<Force> thrust;\r
  52 \r
  53                 public String toString(){\r
  54                         return time + " " + dt + " " + regression + " " + chamberPressure + " " + chamberProduct;\r
  55                 }\r
  56         }\r
  57         \r
  58         protected SortedMap<Amount<Duration>,Interval> data = new TreeMap<Amount<Duration>, Interval>();\r
  59         \r
  60         public SortedMap<Amount<Duration>,Interval> getData(){\r
  61                 return data;\r
  62         }\r
  63         \r
  64         public Motor getMotor(){\r
  65                 return motor;\r
  66         }\r
  67 \r
  68         public Amount<Duration> burnTime(){\r
  69                 return data.lastKey();\r
  70         }\r
  71         \r
  72         public Burn(Motor m){\r
  73                 motor = m;\r
  74                 burn();\r
  75         }\r
  76         \r
  77         public Burn(Motor m, BurnProgressListener bpl){\r
  78                 motor = m;\r
  79                 this.bpl = bpl;\r
  80                 burn();\r
  81         }\r
  82         \r
  83         private void burn(){\r
  84                 log.info("Starting burn...");\r
  85                 long start = new Date().getTime();\r
  86                 \r
  87                 Amount<Length> regStep = Amount.valueOf(0.01, SI.MILLIMETER);\r
  88 \r
  89                 Interval initial = new Interval();\r
  90                 initial.time = Amount.valueOf(0, SI.SECOND);\r
  91                 initial.dt = Amount.valueOf(0, SI.SECOND);\r
  92                 initial.regression = Amount.valueOf(0, SI.MILLIMETER);\r
  93                 initial.chamberPressure = atmosphereicPressure;\r
  94                 initial.chamberProduct = Amount.valueOf(0, SI.KILOGRAM);\r
  95                 initial.thrust = Amount.valueOf(0, SI.NEWTON);\r
  96                 \r
  97                 data.put(Amount.valueOf(0, SI.SECOND), initial);\r
  98                 \r
  99                 step:\r
 100                 for ( int i = 0; i < 5000; i++ ) {\r
 101                         assert(positive(regStep));\r
 102                         regStep = regStep.times(regStepIncreaseFactor);\r
 103                         \r
 104                         Interval prev = data.get(data.lastKey());\r
 105                         log.debug(prev);\r
 106                         log.debug("Step " + i + " ==============================");\r
 107                         Interval next = new Interval();\r
 108                         \r
 109                         Amount<Velocity> burnRate = motor.getFuel().burnRate(prev.chamberPressure);\r
 110                         assert(positive(burnRate));\r
 111                         \r
 112                         log.debug("Burn Rate: " + burnRate);\r
 113                         \r
 114                         Amount<Duration> dt = regStep.divide(burnRate).to(Duration.UNIT);\r
 115                         assert(positive(dt));\r
 116                         next.dt = dt;\r
 117                         \r
 118 \r
 119                         \r
 120                         log.debug("Dt: " + dt);\r
 121                         \r
 122                         next.regression = prev.regression.plus(regStep);\r
 123                         assert(positive(next.regression));\r
 124                         \r
 125                         log.debug("Regression: " + next.regression);\r
 126                         \r
 127                         if ( bpl != null ){\r
 128                                 Amount<Dimensionless> a = next.regression.divide(motor.getGrain().webThickness()).to(Dimensionless.UNIT);\r
 129                                 bpl.setProgress((float)a.doubleValue(Dimensionless.UNIT));\r
 130                         }\r
 131                         \r
 132                         next.time = prev.time.plus(dt);\r
 133                         \r
 134                         //log.debug("Vold: " + motor.getGrain().volume(prev.regression).to(SI.MILLIMETER.pow(3)));\r
 135                         \r
 136                         //log.debug("Vnew: " + motor.getGrain().volume(next.regression).to(SI.MILLIMETER.pow(3)));\r
 137                         \r
 138                         //TODO Amount<Volume> volumeBurnt = motor.getGrain().volume(prev.regression).minus(motor.getGrain().volume(next.regression));\r
 139                         Amount<Volume> volumeBurnt = motor.getGrain().surfaceArea(prev.regression).times(regStep).to(Volume.UNIT);\r
 140                         assert(positive(volumeBurnt));\r
 141                         //log.info("Volume Burnt: " + volumeBurnt.to(SI.MILLIMETER.pow(3)));\r
 142                         \r
 143                         Amount<MassFlowRate> mGenRate = volumeBurnt.times(motor.getFuel().getIdealDensity().times(motor.getFuel().getDensityRatio())).divide(dt).to(MassFlowRate.UNIT);\r
 144                         assert(positive(mGenRate));\r
 145                         \r
 146                         //log.debug("Mass Gen Rate: " + mGenRate);\r
 147                         \r
 148                         //Calculate specific gas constant\r
 149                         Amount<?> specificGasConstant = Constants.R.divide(motor.getFuel().getCombustionProduct().getEffectiveMolarWeight());\r
 150                         //This unit conversion helps JScience to convert nozzle flow rate to\r
 151                         //kg/s a little later on I verified the conversion by hand and\r
 152                         //JScience checks it too.\r
 153                         specificGasConstant = convertSpecificGasConstantUnits(specificGasConstant);\r
 154                         \r
 155                         //Calculate chamber temperature\r
 156                         Amount<Temperature> chamberTemp = motor.getFuel().getCombustionProduct().getIdealCombustionTemperature().times(motor.getFuel().getCombustionEfficiency());\r
 157                         \r
 158                         Amount<MassFlowRate> mNozzle;\r
 159                         {\r
 160                                 Amount<Pressure> pDiff = prev.chamberPressure.minus(atmosphereicPressure);\r
 161                                 //log.debug("Pdiff: " + pDiff);\r
 162                                 Amount<Area> aStar = motor.getNozzle().throatArea();\r
 163                                 double k = motor.getFuel().getCombustionProduct().getRatioOfSpecificHeats();\r
 164                                 double kSide = Math.sqrt(k) * Math.pow((2/(k+1)) , (((k+1)/2)/(k-1)));\r
 165                                 Amount<?> sqrtPart = specificGasConstant.times(chamberTemp).sqrt();\r
 166                                 mNozzle = pDiff.times(aStar).times(kSide).divide(sqrtPart).to(MassFlowRate.UNIT);\r
 167                                 //log.debug("Mass Exit Rate: " + mNozzle.to(MassFlowRate.UNIT));                \r
 168                         }\r
 169                         assert(positive(mNozzle));\r
 170                         \r
 171                         Amount<MassFlowRate> massStorageRate = mGenRate.minus(mNozzle);\r
 172                         \r
 173                         //log.debug("Mass Storage Rate: " + massStorageRate);\r
 174 \r
 175                         next.chamberProduct = prev.chamberProduct.plus(massStorageRate.times(dt));\r
 176                         \r
 177                         //Product can not go negative!\r
 178                         if ( !positive(next.chamberProduct) ){\r
 179                                 log.warn("ChamberProduct Negative on step " + i + "!, Adjusting regstep down and repeating step!");\r
 180                                 regStep = regStep.times(regStepDecreaseFactor);\r
 181                                 continue step;\r
 182                         }\r
 183                         assert(positive(next.chamberProduct));\r
 184                         if ( next.chamberProduct.isLessThan(Amount.valueOf(0, SI.KILOGRAM)) )\r
 185                                 next.chamberProduct = Amount.valueOf(0, SI.KILOGRAM);\r
 186                         \r
 187                         //log.debug("Chamber Product: " + next.chamberProduct);\r
 188                         \r
 189                         Amount<VolumetricDensity> combustionProductDensity = next.chamberProduct.divide(motor.getChamber().chamberVolume().minus(motor.getGrain().volume(next.regression))).to(VolumetricDensity.UNIT);\r
 190                         \r
 191                         log.debug("Product Density: " + combustionProductDensity);\r
 192                         \r
 193                         next.chamberPressure = combustionProductDensity.times(specificGasConstant).times(chamberTemp).plus(atmosphereicPressure).to(Pressure.UNIT);\r
 194                         assert(positive(next.chamberPressure));\r
 195                         \r
 196                         next.chamberPressure = Amount.valueOf(\r
 197                                         next.chamberPressure.doubleValue(SI.PASCAL),\r
 198                                         SI.PASCAL);\r
 199                         \r
 200                         Amount<Pressure> dp = next.chamberPressure.minus(prev.chamberPressure);\r
 201                         if ( dp.abs().isGreaterThan(chamberPressureMaxDelta)){\r
 202                                 log.warn("DP " + dp + " too big!, Adjusting regstep down and repeating step!");\r
 203                                 regStep = regStep.times(regStepDecreaseFactor);\r
 204                                 continue step;\r
 205                         }\r
 206                         \r
 207                         next.thrust = motor.getNozzle().thrust(next.chamberPressure, atmosphereicPressure, atmosphereicPressure, motor.getFuel().getCombustionProduct().getRatioOfSpecificHeats2Phase());\r
 208                         assert(positive(next.thrust));\r
 209                         \r
 210                         if ( i > 100 && next.chamberPressure.approximates(atmosphereicPressure)){\r
 211                                 log.info("Pressure at Patm on step " + i);\r
 212                                 break;\r
 213                         }\r
 214                         \r
 215                         data.put(data.lastKey().plus(dt), next);\r
 216                 }\r
 217 \r
 218                 long time = new Date().getTime() - start;\r
 219                 log.info("Burn took " + time + " millis.");\r
 220         }\r
 221         \r
 222         @SuppressWarnings("unchecked")\r
 223         /*\r
 224          * This converts the units of this constant to something JScience is able\r
 225          * to work from. This conversion is unchecked at compile time, but\r
 226          * JScience keeps me honest at runtime.\r
 227          */\r
 228         private Amount convertSpecificGasConstantUnits(Amount a){\r
 229                 return a.to(\r
 230                                 SI.METER.pow(2).divide(SI.SECOND.pow(2).times(SI.KELVIN)));\r
 231         }\r
 232         \r
 233         public Amount<Pressure> pressure(Amount<Duration> time){\r
 234                 return data.get(time).chamberPressure;\r
 235         }\r
 236         \r
 237         public Amount<Force> thrust(Amount<Duration> time){\r
 238                 return data.get(time).thrust;\r
 239         }\r
 240         \r
 241         public Amount<Dimensionless> kn(Amount<Length> regression){\r
 242                 return motor.getGrain().surfaceArea(regression).divide(motor.getNozzle().throatArea()).to(Dimensionless.UNIT);\r
 243         }\r
 244         \r
 245         \r
 246         private <Q extends Quantity> boolean positive(Amount<Q> a){\r
 247                 return ( a.isGreaterThan(a.minus(a)) || a.equals(a.minus(a)));\r
 248         }\r
 249 \r
 250 }\r