الفهرس 
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Abstract
The efficiency of the external gear pump depends on its frontal and circumferential clearances. Circumferential clearance should be amounts to 0.01-0.03 mm. The clearance usually is not constant along the whole circumference since the gear wheels often shift within bearing slackness towards the suction space. The circumferential clearance is an example of a gap with one wall fixed and the other wall moving in a direction opposite to that of pressure drop. The current development of gear pumps is aimed to increase the working pressure, improve the overall efficiency, reduce pressure fluctuations, minimize weight and noise emission and reduce dynamic loads.... A new modification technique to control the liquid leakage due to internal wearing of the gear pump is investigated in this work. The basis of amendment depends on loss compensation by applying a pressure force on the gear bearings towards the wear location. The volumetric efficiency, mechanical efficiency and overall efficiency are calculated versus the flow rate, inlet pressure, out let pressure and shaft rotational speed is measured. The rotational speed is ranging from the minimum value to 1500 rpm, the output pressure is between 5-60 bar and the corresponding flow rate is ranging between 4-12 Llmin. The results showed a very good improvement of the volumetric efficiency. Volumetric efficiency is increased from 54% to 80% at 1500 rpm by using the new technique.