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