External gear pumps are widely used in many different applications because of their relatively low costs and high performances, especially in terms of volumetric and mechanical efficiency. The main weaknesses of external gear pumps can be summarized as follows:
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1
Sudden increase or decrease of pressure inside volumes between teeth, which could lead respectively to noise emissions and to cavitation onset;
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2
Necessity of limiting power losses and increasing volumetric efficiency, obtainable by reducing leakage flows between components;
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3
Need of maintaining an ad-hoc minimum lubrication film thickness.
In recent years many efforts, in terms of mathematical models and experimental tests, were done in order to limit energy losses and noise emissions. With the aim of deeply studying dynamic behaviour of external gear pumps and addressing their design, a 1D model was developed by means AMESim® code. In particular, a parametric model capable of simulating hydraulically balanced external gear pumps with unitary transmission ratio has been implemented. Geometrical parameters needed by the code were derived directly by ProE® code. The idea at the basis of the model was to use AMESim® icons as much as possible in order to fasten simulations: thus only some icons were developed by the authors in C++ code.
In the current modeling approach the following items were taken into account:
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1
Recovery of the clearance between bearing block and casing;
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2
The actual position of the gears computing the displacement of the bearing center;
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3
The actual wear profile.
The model was then experimentally validated comparing simulated and experimental results for various delivering pressures, engine shaft speeds and gear teeth number (in particular pumps with ten and twelve teeth, characterized by single and double contact were considered). Moreover all models developed by the authors were customized in order to simplify the computational environment for users.