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EN
Powers of energy losses in a variable capacity displacement pump are compared with or without taking into account the power of hydraulic oil compression. Evaluation of power of liquid compression in the pump was made possible by the use of method, proposed by the Author, of determining the degree of liquid aeration in the pump . In the method of determining the liquid aeration in the pump and of powers of volumetric losses of liquid compression a simplified formula (qPvc . ΔpPi)/2 was used describing the field of indicated work of volumetric losses qPvc of liquid compression during one shaft revolution at indicated increase ΔpPi of pressure in the chambers. Three methods were used for comparing the sum of powers of volumetric losses ΔPPvl due to leakage and ΔPPvc of compression and also of mechanical losses resulting from increase ΔpPi of indicated pressure in the working chambers.
EN
The objective of the work is to develop the capability of evaluating the volumetric losses of hydraulic oil compression in the working chambers of high pressure variable capacity displacement pump. Volumetric losses of oil compression must be determined as functions of the same parameters, which the volumetric losses due to leakage, resulting from the quality of design solution of the pump, are evaluated as dependent on and also as function of the oil aeration coefficient ε. A mathematical model has been developed describing the hydraulic oil compressibility coefficient as a relation to the ratio ΔpPi/pn of indicated increase ΔpPi of pressure in the working chambers and the nominal pressure pn, to the pump capacity coefficient bP, to the oil aeration coefficient ε and to the ratio ν/νn of oil viscosity ν and reference viscosity νn. A mathematical model is presented of volumetric losses of hydraulic oil compression in the pump working chambers in the form allowing to use it in the model of power of losses and energy efficiency.
PL
Porównano moce strat energetycznych w pompie wyporowej o zmiennej wydajności, określone bez uwzględnienia bądź z uwzględnieniem mocy ściskania oleju hydraulicznego. Ocena mocy ściskania cieczy w pompie stała się możliwa dzięki zastosowaniu, zaproponowanej przez autora, metody określenia stopnia zapowietrzenia cieczy w pompie. W metodzie określenia stopnia zapowietrzenia cieczy w pompie oraz w ocenie mocy strat objętościowych ściskania cieczy zastosowano uproszczony wzór (qPvc × pn)/2 opisujący pole pracy indykowanej strat objętościowych qPvc ściskania cieczy w trakcie jednego obrotu wału przy indykowanym przyroście ∆pPi ciśnienia w komorach. Porównano trzema metodami sumę mocy strat objętościowych ∆PPvl przecieków i ∆PPvc ściskania oraz strat mechanicznych wynikających z przyrostu ∆pPi ciśnienia indykowanego w komorach roboczych.
EN
Powers of energy losses in a variable capacity displacement pump are compared with or without taking into account the power of hydraulic oil compression. Evaluation of power of liquid compression in the pump was made possible by the use of, proposed by the Author, method of determining the degree of liquid aeration in the pump. In the method of determining the liquid aeration in the pump and of power of volumetric losses of liquid compression a simplified formula (qPvc × pn)/2 was used describing the field of indicated work of volumetric losses qPvc of liquid compression during one shaft revolution at indicated increase ∆pPi of pressure in the chambers. Three methods were used for comparing the sum of power of volumetric losses ∆PPvl due to leakage and ∆PPvc of compression and also of mechanical losses resulting from increase ∆pPi of indicated pressure in the working chambers.
EN
The Author concludes, that there is a possibility of determining a concrete value of the liquid aeration coefficient ε during the pump operation by finding such value of ε with which the increase ΔMPm|ΔpPi = pn, qPgv of torque of mechanical losses is proportional to the indicated torque MPi|ΔpPi = pn, qPgv determined with a fixed value ΔpPi = cte of increase of pressure in the pump working chambers. The fixed value ΔpPi assumed in searching the liquid aeration coefficient ε equals to the nominal pump operation pressure pn (ΔpPi = cte = pn ). The increase ΔMPm|ΔpPi = pn, qPgv of torque of mechanical losses with a fixed value of ΔpPi (ΔpPi = cte) is proportional to the pump geometrical working capacity qPgv , therefore: only with taking into account the aeration coefficient ε of liquid displaced by the pump the relation ΔMPm|ΔpPi = pn, qPgv ~ qPgv can be obtained from tests. The method, proposed by the Author, of determining the working liquid aeration coefficient ε, is presented in this paper and has been practically applied for the first time by Jan Koralewski in his investigations of the influence of viscosity and compressibility of aerated hydraulic oil on volumetric and mechanical losses in a pump of HYDROMATIK A7V.58.1.R.P.F.00 type [8, 9].
EN
Modulus B of the liquid volume elasticity of non-aerated and aerated oil is defined in the paper as relation to the indicated increase of pressure in the pump working chambers, with the change of oil temperature and degree of aeration. In evaluation of the losses due to oil compressibility in a variable capacity displacement pump, the volume of compressed liquid at each pump setting is taken into account. Volumetric losses have been divided into leakage losses in the pump chambers and losses due to liquid compressibility. The need of accounting for only the leakage losses for pump evaluation is pointed out.
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