The Determination of the Theoretical Stroke Volume of Hydrostatic Positive Displacement Pumps and Motors from Volumetric Measurements

Toet, Gijsbert; Johnson, J.; Montague, John; Torres, Ken; Garcia-Bravo, José

doi:10.3390/en12030415

Cited by 20 publications

(40 citation statements)

References 7 publications

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“…The contribution of the torque loss due to meshing has been evaluated here according to ISO/TR 14179-1 [32], which describes the losses in gear boxes made of gear wheels. In order to consider the case of an external gear pump, the formulation has been modified considering the two equal gears Several studies have researched this aspect [2,4], showing that the main tilt direction of the bushing with respect to the gears is around a line that crosses the centres of the bushings, as assumed in Figure 6.…”

Section: Meshing Lossmentioning

confidence: 99%

“…As a general comment, when comparing the measured data with the calculated ones, the uncertainty in the measurement reaches ±6% in the smaller measured torque values, due to the torque meter accuracy and full-scale range of the instrument. Moreover, a small error, very difficult to be evaluated, also affects the value of the pump displacement used for the calculation of efficiency [22], since the pump displacement was derived by the measurement of the flow rate and rotational speed, using the method suggested by Toet et al ( [32]).…”

Section: Sensitivity Of the Model With Respect To The Lateral Clearanmentioning

confidence: 99%

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Evaluation of the Hydro—Mechanical Efficiency of External Gear Pumps

2019

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This paper proposes and describes a model for evaluating the hydro-mechanical efficiency of external gear machines. The model is built considering and evaluating the main friction losses in the machines, including the viscous friction losses at the tooth tip gap, at the bearing blocks-gears gaps, at the journal bearings, and the meshing loss. To calculate the shear stress at each gap interface, the geometry of the gap has to be known. For this reason, the actual position of the gears inside the pump casing and consequent radial pressure distribution are numerically calculated to evaluate the gap height at the tooth tips. Moreover, the variation of the tilt and reference height of the lateral gaps between the gears and the pump bushings are considered. The shear stresses within the lateral gaps are estimated, for different lateral heights and tilt values. At the journal bearings gaps, the half Sommerfeld solution has been applied. The meshing loss has been calculated according to the suggestion of the International Standards. The hydro-mechanical efficiency results are then discussed with reference to commercial pumps experimentally characterized by the authors in a previous work. The average percentage deviation from experimental data was around 2%, without considering the most critical operating conditions (high delivery pressure, low rotational speed). The limits of this approach are also explained. Finally, the role of each source of loss is discussed, considering different operating conditions and two values of fluid viscosity. Lateral gap losses and meshing loss are much more relevant in determining the hydro-mechanical efficiency variation in the pump’s operating range, especially at a low delivery pressure. Moreover, while lateral gap losses increase with the rotational speed, the meshing loss shows the opposite behavior. The tooth tip gap losses are never as relevant, but they increase at high pressure. The journal bearings losses become comparable with the lateral and meshing ones at high delivery pressure values. Considering the pumps analyzed and the operating range of delivery pressure values and rotational speed values, the meshing loss made the mechanical efficiency vary in a percentage range of ±7%, with lateral losses in the range of about the ±15%, when also considering the extreme operating points (low speed, high pressure; high speed, low pressure). The weight of the lateral losses slightly reduced when we analyzed the higher temperature results, while the meshing losses slightly increased.

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Section: Meshing Lossmentioning

confidence: 99%

Section: Sensitivity Of the Model With Respect To The Lateral Clearanmentioning

confidence: 99%

Evaluation of the Hydro—Mechanical Efficiency of External Gear Pumps

2019

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“…The occurrence of volumetric efficiencies greater than 100% is quite common, as a consequence of an incorrect procedure for determining the derived capacity. This scenario has been analyzed by Toet et al [21] in a revised translation of a work developed more than 40 years ago by the author, which has been the basis of successive editions of the ISO 8426 standard.…”

Section: Parameterization Of the Pumpmentioning

confidence: 99%

Parameterization, Modeling, and Validation in Real Conditions of an External Gear Pump

2021

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This article presents a methodology for predicting the fluid dynamic behavior of a gear pump over its operating range. Complete pump parameterization was carried out through standard tests, and these parameters were used to create a bond graph model to simulate the behavior of the unit. This model was experimentally validated under working conditions in field tests. To carry this out, the pump was used to drive the auxiliary movements of a drilling machine, and the experimental data were compared with a simulation of the volumetric behavior under the same conditions. This paper aims to describe a method for characterizing any hydrostatic pump as a “black box” model predicting its behavior in any operating condition. The novelty of this method is based on the correspondence between the variation of the parameters and the internal changes of the unit when working in real conditions, that is, outside a test bench.

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“…Conditions (12) and (13), with the assumption that σ m = σ a = σ max /2, may serve to define the maximum stresses possible in the lip restraint cross-section:…”

Section: Calculations Of Minimum Beam Thickness Using the Fatigue Strmentioning

confidence: 99%

“…The flow velocity of the working fluid significantly influences the losses observed in the ducts, as well as in the hydraulic and fastening elements. The energy-consumption of a system is also significantly influenced by the total efficiency of a displacement unit [9][10][11][12][13]. Total pump efficiency describes the relationship between the output (hydraulic) power N h and the input (mechanical) power N m or is defined by the product of the volumetric efficiency η v and the hydromechanical efficiency η hm .…”

Section: Introductionmentioning

confidence: 99%

Theoretical and Experimental Fatigue Strength Calculations of Lips Compensating Circumferential Backlash in Gear Pumps

2021

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This article presents theoretical and experimental calculations of the minimum thickness of a compensation lip used in external gear pumps. Pumps of this type are innovative technical solutions in which circumferential backlash (clearance) compensation is used to improve their volumetric and overall efficiency. However, constructing a prototype of such a pump requires long-lasting research, and the compensation lip is its key object, due to the fact that it is an element influenced by a notch and that it operates in unfavorable conditions of strong fatigue stresses. The theoretical calculations presented in this article are based on identifying maximum stress values in a fatigue cycle and on implementing the stress failure condition and the conditions related to the required value of the fatigue safety factor. The experimental research focuses on static bending tests of the lips as well as on the fatigue loading of the lips in series of tests at increasing stress values until lip failure due to fatigue. The tests allowed the minimum lip thickness to be found for the assumed number of fatigue cycles, which is 2.5 times the number of cycles used in wear margin tests.

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The Determination of the Theoretical Stroke Volume of Hydrostatic Positive Displacement Pumps and Motors from Volumetric Measurements

Cited by 20 publications

References 7 publications

Evaluation of the Hydro—Mechanical Efficiency of External Gear Pumps

Evaluation of the Hydro—Mechanical Efficiency of External Gear Pumps

Parameterization, Modeling, and Validation in Real Conditions of an External Gear Pump

Theoretical and Experimental Fatigue Strength Calculations of Lips Compensating Circumferential Backlash in Gear Pumps

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