`field_purge_field()` is described as follows:

> This function assumes all data for the field has already been purged and should only be called by [`field_purge_batch()`][1].

On Drupal, fields are effectively removed during cron tasks; in fact, `field_purge_batch()` is called from [`field_cron()`][2], the implementation of `hook_cron()` done from the Field module. There is no need for you to call neither `field_purge_field()` nor `field_purge_batch()`.

If you want to write code to purge fields for a node bundle, that code would be similar to the following one. (See the notes after the code, thought.)

      $properties = array(
        'entity_type' => 'node',
        'bundle' => 'Your bundle (a.k.a. content type)',
        'include_deleted' => TRUE,
      );
    
      \Drupal::entityManager()->getStorage('field_config')->loadByProperties($properties);
    
      $info = \Drupal::entityManager()->getDefinitions();
      foreach ($fields as $field) {
        $entity_type = $field->getTargetEntityTypeId();
    
        // Proceed only if the module implementing the entity has not been uninstalled already.
        if (isset($info[$entity_type])) {
          Drupal::entityManager()->getStorage($entity_type)->purgeFieldData($field, 100);
          field_purge_field($field);
        }
      }

### Notes

- Purging the fields is thought to be ran during cron tasks; that is why `Drupal::entityManager()->getStorage()->purgeFieldData()` requires the batch size as argument. I used a value of 100, which would possibly allows the code to purge all the fields for that content type, but it is not warranted that 100 would not cause any PHP timeout error. It would be better to run the code from PHP CLI, in order to avoid any execution time out.
- You should not need to use this code; in most of the cases, you should execute the cron tasks (which is when Drupal purges the fields of a deleted bundle), or use Drush to purge the fields, either running `hook_cron()` with it, or executing a specific Drush command (if it exists).


  [1]: https://api.drupal.org/api/drupal/core%21modules%21field%21field.purge.inc/function/field_purge_batch/8
  [2]: https://api.drupal.org/api/drupal/core%21modules%21field%21field.module/function/field_cron/8