Abstract
Earlier equations used to calculate the positions of the release ports of gear pumps were derived without considering changes in running conditions which are apt to occur in field applications. Therefore, gear pumps designed using these equations gave lower efficiencies in some, or most, running conditions. With the support of the theory, the authors found new release ports suitable for the gear pumps to be operated under various running conditions. Experiments were conducted using two helical gear pumps with conventional and new release ports. The pump with the new release ports brought about larger deliveries and also higher efficiencies. The reason for this is explained by the theoretical characteristics of the gear pumps.
