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