changed code when low molecular weights of plus fraction (#1214)

src/main/java/neqsim/thermo/characterization/Characterise.java

@@ -159,8 +159,10 @@ public void characterisePlusFraction() {
         plusFractionModel = plusFractionModelSelector.getModel("Pedersen Heavy Oil");
         logger.info("changing to " + plusFractionModel.getName());
       }
-      plusFractionModel.characterizePlusFraction(TBPfractionModel);
-      lumpingModel.generateLumpedComposition(this);
+      boolean couldCharacerize = plusFractionModel.characterizePlusFraction(TBPfractionModel);
+      if (couldCharacerize) {
+        lumpingModel.generateLumpedComposition(this);
+      }
     }
   }
 

src/main/java/neqsim/thermo/characterization/PlusFractionModel.java

@@ -1,5 +1,7 @@
 package neqsim.thermo.characterization;
 
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
 import neqsim.thermo.system.SystemInterface;
 
 /**
@@ -11,6 +13,7 @@
  * @version $Id: $Id
  */
 public class PlusFractionModel implements java.io.Serializable {
+  static Logger logger = LogManager.getLogger(PlusFractionModel.class);
   private static final long serialVersionUID = 1000;
   private String name = "";
   private SystemInterface system = null;
@@ -193,7 +196,7 @@ public boolean hasPlusFraction() {
     }
 
     @Override
-    public void characterizePlusFraction(TBPModelInterface TBPModel) {
+    public boolean characterizePlusFraction(TBPModelInterface TBPModel) {
       system.init(0);
       Integer firstPlusNumber = Integer.valueOf(0);
       if (system.getPhase(0).getComponent(plusComponentNumber).getComponentName().substring(3, 4)
@@ -210,6 +213,10 @@ public void characterizePlusFraction(TBPModelInterface TBPModel) {
 
       numberOfPlusPseudocomponents = lastPlusFractionNumber - firstPlusFractionNumber + 1;
 
+      if (PVTsimMolarMass[firstPlusFractionNumber - 6] > MPlus * 1000) {
+        logger.error("Plus fraction molar mass too light ");
+        return false;
+      }
       // System.out.println("first plus fraction number " + firstPlusFractionNumber);
       coefs[0] = 0.1;
       coefs[1] = Math.log(zPlus) / getFirstPlusFractionNumber();
@@ -229,6 +236,7 @@ public void characterizePlusFraction(TBPModelInterface TBPModel) {
         dens[i] = getCoef(2) + getCoef(3) * Math.log(i);
       }
       // System.out.println("z,m,dens " + z[i] + " " + M[i] + " " + dens[i]);
+      return true;
     }
 
     @Override
@@ -381,7 +389,7 @@ public void densityUOP() {
     }
 
     @Override
-    public void characterizePlusFraction(TBPModelInterface TBPModel) {
+    public boolean characterizePlusFraction(TBPModelInterface TBPModel) {
       system.init(0);
       double MWBU = Double.NaN;
       double MWBL = Double.NaN;
@@ -427,6 +435,7 @@ public void characterizePlusFraction(TBPModelInterface TBPModel) {
       for (int i = firstPlusFractionNumber; i < lastPlusFractionNumber; i++) {
         zValues[i] *= zPlus / sumZ;
       }
+      return true;
     }
 
     public void setGammaParameters(double shape, double minMW) {

src/main/java/neqsim/thermo/characterization/PlusFractionModelInterface.java

@@ -25,7 +25,7 @@ public interface PlusFractionModelInterface extends java.io.Serializable {
    *
    * @param model a {@link neqsim.thermo.characterization.TBPModelInterface} object
    */
-  public void characterizePlusFraction(TBPModelInterface model);
+  public boolean characterizePlusFraction(TBPModelInterface model);
 
   /**
    * <p>
@@ -73,7 +73,9 @@ public interface PlusFractionModelInterface extends java.io.Serializable {
   public int getLastPlusFractionNumber();
 
   /**
-   * <p>setLastPlusFractionNumber.</p>
+   * <p>
+   * setLastPlusFractionNumber.
+   * </p>
    *
    * @param fract a int
    */

src/test/java/neqsim/thermo/characterization/PlusFractionModelTest.java

@@ -144,4 +144,52 @@ void testGammaModelCharacterization() {
         .getGammaParameters()[1];
     assertEquals(90.0, minMW, 1e-4);
   }
+
+  @Test
+  void testC6C7PlusModel() {
+    SystemInterface thermoSystem = null;
+    thermoSystem = new SystemSrkEos(298.0, 10.0);
+
+    thermoSystem.addComponent("CO2", 1.0);
+    thermoSystem.addComponent("methane", 51.0);
+    thermoSystem.addComponent("ethane", 1.0);
+    thermoSystem.addComponent("propane", 1.0);
+
+    thermoSystem.getCharacterization().setTBPModel("PedersenSRK"); // this need to be set before
+                                                                   // adding oil components
+
+    String[] componentNames = {"C7"};
+    double[] molarComposition = {0.15};
+    double[] molarMasses = {0.092};
+    double[] reldens = {0.82};
+
+    thermoSystem.getCharacterization().setTBPModel("PedersenSRK"); // this need to be set before
+
+    thermoSystem.addOilFractions(componentNames, molarComposition, molarMasses, reldens, true);
+
+    // In this case the molar mass of the plus fraction is set to 0.092 kg/mol an is too low to
+    // distribute the component into heavier components
+    assertEquals(5, thermoSystem.getNumberOfComponents());
+
+    thermoSystem = new SystemSrkEos(298.0, 10.0);
+
+    thermoSystem.addComponent("CO2", 1.0);
+    thermoSystem.addComponent("methane", 51.0);
+    thermoSystem.addComponent("ethane", 1.0);
+    thermoSystem.addComponent("propane", 1.0);
+
+    thermoSystem.getCharacterization().setTBPModel("PedersenSRK"); // this need to be set before
+                                                                   // adding oil components
+
+    molarMasses = new double[] {0.120};
+
+    thermoSystem.getCharacterization().setTBPModel("PedersenSRK"); // this need to be set before
+
+    thermoSystem.addOilFractions(componentNames, molarComposition, molarMasses, reldens, true);
+    // In this case the molar mass of the plus fraction is high enogh and can be characterized into
+    // heavier components
+
+    assertEquals(16, thermoSystem.getNumberOfComponents());
+
+  }
 }