add GCV and WI for streams (#997)

Author: EvenSol

src/main/java/neqsim/processSimulation/processEquipment/stream/Stream.java

@@ -606,6 +606,26 @@ public double GCV() {
     return standard.getValue("GCV") * 1.0e3;
   }
 
+  /** {@inheritDoc} */
+  @Override
+  public double getGCV(String unit, double refTVolume, double refTCombustion) {
+    Standard_ISO6976 standard =
+        new Standard_ISO6976(getFluid().clone(), refTVolume, refTCombustion, unit);
+    standard.setReferenceState("real");
+    standard.calculate();
+    return standard.getValue("GCV") * 1.0e3;
+  }
+
+  /** {@inheritDoc} */
+  @Override
+  public double getWI(String unit, double refTVolume, double refTCombustion) {
+    Standard_ISO6976 standard =
+        new Standard_ISO6976(getFluid().clone(), refTVolume, refTCombustion, unit);
+    standard.setReferenceState("real");
+    standard.calculate();
+    return standard.getValue("WI") * 1.0e3;
+  }
+
   /** {@inheritDoc} */
   @Override
   public double LCV() {

src/main/java/neqsim/processSimulation/processEquipment/stream/StreamInterface.java

@@ -244,6 +244,30 @@ public default double getFlowRate(String unit) {
    */
   public double GCV();
 
+  /**
+   * <p>
+   * getGCV.
+   * </p>
+   * 
+   * @param unit a String
+   * @param refTVolume a double in Celcius
+   * @param refTCombustion a double in Celcius
+   * @return a double
+   */
+  public double getGCV(String unit, double refTVolume, double refTCombustion);
+
+  /**
+   * <p>
+   * getWI.
+   * </p>
+   * 
+   * @param unit a String
+   * @param refTVolume a double in Celcius
+   * @param refTCombustion a double in Celcius
+   * @return a double
+   */
+  public double getWI(String unit, double refTVolume, double refTCombustion);
+
   /**
    * <p>
    * LCV.