Experimental Measurement and Numerical Validation of the Flow Ripple in Internal Gear Pumps

Abstract

The flow ripple in an internal gear pump was measured by means of a new instantaneous high-pressure flowmeter. The flowmeter consists of two pressure sensors mounted on a piece of the straight steel pump delivery line, and a variable-diameter orifice was installed along such a line, downstream of the flowmeter, to generate a variable load. Three distinct configurations of the high-pressure flowmeter, characterized by a different distance between the pressure transducers, were analyzed. Furthermore, a comprehensive fluid dynamic 3D model of the pump and of its high-pressure delivery line was developed and validated in terms of both the delivery pressure and the flow ripple for different pump working conditions. For the three examined configurations of the flowmeter, the measured flowrate time histories matched the corresponding numerical distributions at the various operating points. Finally, the validated 3D model was applied to predict the incomplete filling working of the interteeth chambers, and the obtained numerical pressure time histories along the delivery line were used, as input data, to assess the reliability of the flowmeter algorithm even in these severe operating conditions.

Investigation of a GDI injector with an innovative flowmeter for high-pressure transient flows

“…Furthermore, the accuracy of the unidimensional approach has been proved in previous researches where 3D model results have been compared for some Flotec applications. 20,21 It is assumed, through the hypothesis of a local incompressible fluid for the piece of pipeline between the two pressure transducers, that dr dt '0. Hence, the liquid density variations due to the change in the mean pressure level are considered, while the density fluctuations due to the pressure oscillations around the timeaveraged pressure level are neglected.…”

“…Furthermore, the accuracy of the unidimensional approach has been proved in previous researches where 3D model results have been compared for some Flotec applications. 20,21…”

“…A first-order nonlinear ordinary differential equation has been obtained by combining Euler’s mass conservation and momentum balance equations, where both the steady-state and the unsteady friction terms have been considered. The presented flowmeter, which has already been satisfactorily applied to Common Rail systems 19 (with pressures of up to 1800 bar) and to volumetric pumps 20,21 (with pressures in the 4–140 bar range), has here been applied to a GDI system, with the support of the 1D diagnostic tool, to investigate its internal fluid dynamics . Furthermore, a possible closed-loop control strategy of the injected mass, which is based on the application of the presented flowmeter to the fuel injection hydraulic circuit, is presented.…”

Instantaneous flowrate measurements in high-pressure liquid flows

“…The presented flowmeter has been applied to measure the flow ripples of an external gear pump [22], of an internal gear pump [23], and the flow entering a Common Rail injector during an injection event [24,25].…”

“…The 3D numerical models pertaining to the gear pumps, together with their delivery lines, have been built with the commercial software SimericsMP+, where the governing equations are discretized by means of finite volume method. Further details about the models of the external gear pump and the internal one can be found in [22] and [23], respectively. After a grid independence analysis, simulations have been performed and the models have been validated by comparing the numerical pressure traces detected along the pump delivery lines, in correspondence of the pressure sensors locations, with the corresponding experimental time histories.…”