chore: warn user about full recirculation of fluids in a compressor s…

…tage in a multiple streams and pressures compressor train (#196)

chore: add NO_FLOW ChartAreaFlag

chore: add chart area flag to test of full recirculation

docs/docs/changelog/next.md

@@ -12,6 +12,9 @@ sidebar_position: 1
 
 ## New Features
 
+- Added chart area flag NO_FLOW_RATE to the possible statuses for an operational point in a variable speed compressor chart. The chart area flags can currently only be found in the json result file, but we will also try to find a way of displaying this information in the WebApp as well.
+- Whenever there is a variable speed compressor only recirculation fluid (can happen in a multiple streams and pressures compressor train) a warning will be logged.
+
 
 ## Fixes
 

src/libecalc/core/models/compressor/results.py

@@ -290,15 +290,22 @@ def set_failure_status(cls, v, values):
 
     @property
     def chart_area_status(self) -> ChartAreaFlag:
-        chart_area_failure = [
-            stage.chart_area_flag
-            for stage in self.stage_results
-            if stage.chart_area_flag != ChartAreaFlag.INTERNAL_POINT
-        ]
+        """Checks where the operational points are placed in relation to the compressor charts in a compressor train.
+
+        Returns:
+            A chart area flag describing the placement of the operational points in the compressor train.
+            If several of the compressors in the compressor train is out of capacity, only the first failure will
+            be returned.
+        """
+        chart_area_failure = [stage.chart_area_flag for stage in self.stage_results if not stage.point_is_valid]
         if len(chart_area_failure) > 0:
             return chart_area_failure[0]
         else:
-            return [stage.chart_area_flag for stage in self.stage_results][0]
+            chart_area_flag = [stage.chart_area_flag for stage in self.stage_results if stage.point_is_valid]
+            if ChartAreaFlag.NO_FLOW_RATE in chart_area_flag:
+                return ChartAreaFlag.NO_FLOW_RATE
+            else:
+                return chart_area_flag[0]
 
     @property
     def is_valid(self) -> bool:

src/libecalc/core/models/compressor/train/chart/variable_speed_compressor_chart.py

@@ -292,10 +292,18 @@ def _evaluate_point_validity_chart_area_flag_and_adjusted_speed_and_rate(
             further out in iterations to meet pressure targets, and one need to get information about if the point
             is valid (within capacity) or not.
 
-        :param speed: [rpm]
-        :param increase_speed_below_assuming_choke: True or False
-        :param rate: [Am3/h]
-        :param increase_rate_left_of_minimum_flow_assuming_asv: True or False
+        Args:
+            speed: the speed related to the operation point [rpm]
+            increase_speed_below_assuming_choke: boolean telling whether the speed related to an operation point should
+              be changed to the minimum speed if the speed is below the minimum speed (assumes up/down-stream choking)
+            rate: the actual inlet flow rate of the operation point [Am3/h]
+            recirculated_rate: potential additional flow rate introduced by the anti-surge valve for pressure control
+            increase_rate_left_of_minimum_flow_assuming_asv: boolean telling whether the actual flow rate should be
+              automatically changed to the minimum flow rate for the compressor chart when below the minimum flow rate
+
+        Returns:
+            A tuple of values describing if the operation point is valid, information about where the operation
+            point is placed relative to the compressor chart, and the (potentially updated) values for speed and rate
         """
         point_is_valid = True
         chart_area_flag = ChartAreaFlag.INTERNAL_POINT
@@ -317,16 +325,21 @@ def _evaluate_point_validity_chart_area_flag_and_adjusted_speed_and_rate(
             # Todo: Need to QA this logic. Below minimum speed requires speed < minimum_speed, but this is not enforced?
             minimum_flow_rate_for_speed = self.minimum_rate_as_function_of_speed(speed_to_use)
             maximum_flow_rate_for_speed = self.maximum_rate_as_function_of_speed(speed_to_use)
-            if rate < minimum_flow_rate_for_speed:
+            # first update rate_to_use when below minimum flow if increase_rate_left_of_minimum_flow_assuming_asv
+            if rate_to_use < minimum_flow_rate_for_speed:
+                if increase_rate_left_of_minimum_flow_assuming_asv:
+                    rate_to_use = minimum_flow_rate_for_speed
+                else:
+                    point_is_valid = False
+            # second, decide ChartAreaFlag based on the original rate input
+            if rate == 0:
+                chart_area_flag = ChartAreaFlag.NO_FLOW_RATE
+            elif rate < minimum_flow_rate_for_speed:
                 chart_area_flag = (
                     ChartAreaFlag.BELOW_MINIMUM_SPEED_AND_BELOW_MINIMUM_FLOW_RATE
                     if speed_is_increased
                     else ChartAreaFlag.BELOW_MINIMUM_FLOW_RATE
                 )
-                if increase_rate_left_of_minimum_flow_assuming_asv:
-                    rate_to_use = max(minimum_flow_rate_for_speed, rate_to_use)
-                else:
-                    point_is_valid = False
             elif rate > maximum_flow_rate_for_speed:
                 chart_area_flag = (
                     ChartAreaFlag.BELOW_MINIMUM_SPEED_AND_ABOVE_MAXIMUM_FLOW_RATE

src/libecalc/core/models/compressor/train/variable_speed_compressor_train_common_shaft_multiple_streams_and_pressures.py

@@ -872,6 +872,11 @@ def calculate_compressor_train_given_rate_ps_speed(
                     stage_number=stage_number
                 )
                 if fluid_to_recirculate:
+                    logger.warning(
+                        f"For stage number {stage_number}, there is no fluid entering the stage at at this time step. "
+                        f"The compressor is only recirculating fluid. Standard rates are "
+                        f"{std_rates_std_m3_per_day_per_stream}."
+                    )
                     inlet_stream = fluid_to_recirculate
                 else:
                     raise ValueError(

src/libecalc/dto/types.py

@@ -159,3 +159,4 @@ class ChartAreaFlag(str, Enum):
     BELOW_MINIMUM_SPEED_AND_BELOW_MINIMUM_FLOW_RATE = "BELOW_MINIMUM_SPEED_AND_BELOW_MINIMUM_FLOW_RATE"
     BELOW_MINIMUM_SPEED_AND_ABOVE_MAXIMUM_FLOW_RATE = "BELOW_MINIMUM_SPEED_AND_ABOVE_MAXIMUM_FLOW_RATE"
     NOT_CALCULATED = "NOT_CALCULATED"
+    NO_FLOW_RATE = "NO_FLOW_RATE"

src/tests/libecalc/core/models/compressor_modelling/test_variable_speed_compressor_train_multiple_streams.py

@@ -707,3 +707,11 @@ def test_recirculate_mixing_streams_with_zero_mass_rate(
     assert result.recirculation_loss[2] < result.recirculation_loss[3]
     assert result.recirculation_loss[4] < result.recirculation_loss[5]
     assert result.power[0] < result.power[2] < result.power[4]  # more and more of the heavy fluid
+    assert result.stage_results[1].chart_area_flags == [
+        ChartAreaFlag.BELOW_MINIMUM_FLOW_RATE.value,
+        ChartAreaFlag.NO_FLOW_RATE.value,
+        ChartAreaFlag.BELOW_MINIMUM_FLOW_RATE.value,
+        ChartAreaFlag.NO_FLOW_RATE.value,
+        ChartAreaFlag.BELOW_MINIMUM_FLOW_RATE.value,
+        ChartAreaFlag.NO_FLOW_RATE.value,
+    ]