Wyniki wyszukiwania - BazTech

1

The analysis of working liquid flow in a hydrostatic line with the use of frequency characteristics

Ułanowicz L., Jastrzębski G.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2020

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Vol. 68, nr 4

949--956

EN

One of the little described problems in hydrostatic drives is the fast changing runs in the hydraulic line of this drive affecting the nature of the formation and intensity of pressure pulsation and flow rate occurring in the drive. Pressure pulsation and flow rate are the cause ofthe unstable operation of servos, delays in the control system and other harmful phenomena. The article presents a flow model in a hydrostatic drive line based on fluid continuity equations (mass conservation), maintaining the amount of Navier-Stokes motion in the direction of flow (x axis), energy conservation (liquid state). The movement of liquids in a hydrostatic line is described by partial differential equations of the hyperbolic type, so modeling takes into account the wave phenomena occurring in the line. The in hydrostatic line was treated as a cross with two inputs and two outputs, characterized by a specific transmittance matrix. The product approximation was used to solve the wave equations. An example of the use of general equations is presented for the analysis of a miniaturized hydrostatic drive line fed from a constant pressure source and terminated by a servo mechanism.

2

Methods for determining the take-off speed of launchers for unmanned aerial vehicles

Jastrzębski G., Ułanowicz L.

Journal of KONES

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2018

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Vol. 25, No. 1

170--176

EN

Unmanned aerial vehicles (UAV) are currently a very rapidly developing type of aviation. The problem of support during the take-off with the use of, i.e. take-off launchers arose along with their development, especially for UAVs with weights and dimensions preventing manual take-off. One of the major issues associated with UAV take-off launchers is for its UAV accelerating element to obtain its initial speed. The article presents three methods of determining launcher take-off speeds for unmanned aerial vehicles, i.e. the concentrated very oblique projection method, the high-speed camera methods, and the acceleration recorder method. The take-off launcher carriage speed in the oblique projection method is determined from a formula. This method involves “ejections” of concentrated masses from the UAV mass range and measuring the component values resulting from the used formula, which contains the range of the oblique projection, the elevation of the projection and its angle. The method using the high-speed camera involves recording the course of ejections of the concentrated mass from the launcher. The average take-off speed is determined on the basis of a take-off run length (section of the launcher race, where the unit accelerates) and defining the start and end frame of the carriage movement. The third method for the determination of the take-off speed utilizes an acceleration recorder. The method with the recorder involves registering a change in the accelerations when the take-off carriage is being accelerated by a system fixed on the carriage or the accelerated object. The article presents the methodology of dynamic tests of object acceleration on a launcher, necessary for the determination of speed with the mentioned methods. Selected results from actual tests with the use of the 01/WS/2015 launcher, which is an element of the ZOCP JET2 set, were presented. The test results are presented in a tabular form. The methods for the determination of the take-off speed were compared on the basis of performed tests. Based on the obtained results, the factors impacting the accuracy of each of the methods were identified.

3

Method for estimating the static friction degree in the slide pair of the miniaturised electrohydraulic servomechanism

Ułanowicz L., Żyluk A.

Journal of KONES

|

2018

|

Vol. 25, No. 2

399--407

EN

One of the most important parameters specifying the usability of the miniaturised electrohydraulic servomechanism includes a static friction degree in its slide pairs, i.e. resistance of the slider’s movement from rest after some time of its staying at rest under pressure. Therefore, at the stage of designing and construction of the electrohydraulic servomechanism, it is important to determine the greatest static friction degree, which may arise in the slider hydraulic pair of this device during its operation. The objective of this article is to present a method for estimating the maximum static friction values in the slide pair based on the extreme value theory. The operation and loading conditions of the slide pair of the electrohydraulic servomechanism for the unmanned aircraft control system were described. The procedure for estimating the maximum static friction degree in the slide pair with the use of the extreme and probabilistic grid was presented. The extreme and probabilistic grid structure was based on the Gumbel probability graph. The graphic presentation of results of the static friction experimental studies in the slide pair on the extreme and probabilistic grid was discussed. By using the graphics method, the empirical dependence of the static friction force in the slide pair on the working fluid pressure in the hydraulic drive (loading conditions) was determined. A practical example of estimating the maximum values of the static friction force that may occur in the slider hydraulic pair of the miniaturized electrohydraulic servomechanism is shown.

4

Pneumatic propellant system model of an emergency parachute system for a vertical take-off and landing UAV

Jastrzębski G., Szczepaniak P., Nowakowski M., Ułanowicz L., Jóźko M., Włodarczyk J.

Journal of KONBiN

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2018

|

No. 48

385--398

EN

The subject of this publication is a mathematical model of a pneumatic supply system for an emergency parachute system. This system is intended for a vertical take-off and landing UAV. An overview of emergency parachute landing system designs is presented in the introduction. Based on a schematic diagram and a 3D computer model, the construction and operation principles of an emergency parachute system, currently being developed at AFIT, was presented. A mathematical model, which enables the determination of the energy of gas (compressed CO2) stored in the accumulator tank was described. The conducted tests, which involved weighing the accumulator after filling with liquefied CO2 from a special cartridge and equivalent mass ejections were discussed. These tests involved recording the track of the equivalent mass movement and time necessary to determine velocity. The results of calculations regarding the equivalent mass energy imitating an emergency parachute, CO2 volume and mass in the accumulator in liquefied and gaseous state were presented. Based on the conducted calculations and the obtained characteristics, the developed mathematical model was assessed, and the final conclusions formulated.

5

Hydraulic plunger pump contamination sensitivity evaluation

Ułanowicz L., Jastrzębski G., Jóźko M., Sabak R., Szczepaniak P.

Journal of KONBiN

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2018

|

No. 48

371--383

EN

The correct operation of the hydraulic pump and achieving the assumed durability depends on the purity of the used working fluid. The research paper discusses a method for evaluating the contamination sensitivity of a hydraulic plunger pump. The theoretical grounds for evaluating the contamination sensitivity of hydraulic plunger pumps of a hydraulic drive based on the contamination sensitivity factor were presented. An example of evaluating contamination sensitivity of an NP-34M hydraulic plunger pump was discussed.

PL

Poprawne działanie pompy hydraulicznej i jej trwałość zależy od czystości użytkowanej cieczy roboczej. W artykule przedstawiono metodę szacowanie wrażliwości zanieczyszczeniowej nurnikowej pompy hydraulicznej. Zaprezentowano podstawy teoretyczne szacowania wrażliwości zanieczyszczeniowej nurnikowych par hydraulicznych napędu hydraulicznego oparte o współczynnik wrażliwości zanieczyszczeniowej. Przedstawiono przykład szacowania wrażliwości zanieczyszczeniowej nurnikowej pompy hydraulicznej typu NP-34M.

6

Use of remotely piloted aircraft systems to evaluate the effects of transport collision

Romańska H., Ułanowicz L.

Zeszyty Naukowe. Transport / Politechnika Śląska

|

2017

|

z. 94

199--210

EN

The evaluation of the effects of transport collision often takes the form of ground reconnaissance. Undoubtedly, remotely piloted aircraft systems (RPAS) can support and help the police, firefighters, security agents and paramedics in the event of a transport collision. Although there is a scarce amount of literature concerning the use of RPAS in crisis management, it is important to pay more attention to the benefits of this technology. The article describes the danger of collisions, as well as discusses the possibility of using RPAS, their functionality and potential utility. Sensors installed on RPAS can rapidly identify the place of the accident, the number of casualties, the type of damaged vehicles or the type of contamination.

7

Controlling the operation process of the unmanned aerial system

Ułanowicz L., Jóźko M., Szczepaniak P.

Journal of KONBiN

|

2017

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No. 44

5--36

EN

The development of unmanned aerial systems (UAS) encountered the problem of controlling the process of technical operation. The literature that is available to the authors lacks credible information concerning the principles of specifying the strategy and control of the process of UAS operation. Hence, it is necessary to recognise and interpret the basic UAS operation features. The purpose of the publication is to present the properties of the UAS as an object of operation and the mutual relation of the technical operation process with the UAS’ technical condition alteration process. We present the results of analyses in terms of functionality and the UAS’ utility potential. The publication pays special attention to the properties of the UAS as an object of operation. The paper includes the analysis of the UAS operation principles and the specification of the advantage and disadvantage of those principles, i.e. using a non-repairable UAS until damaged, using a repairable UAS until damaged, periodical technical servicing, continuous diagnostic operation. The proposals for the control models in the UAS operation system have also been included.

PL

Wraz z rozwojem bezzałogowych systemów powietrznych (BSyP) pojawił się problem sterowania procesem ich eksploatacji technicznej. W dostępnej autorom literaturze brakuje wiarygodnych informacji dotyczących zasad określania strategii i sterowania procesem eksploatacji BSyP. W związku z tym istnieje potrzeba rozpoznania oraz interpretacji podstawowych charakterystyk eksploatacyjnych BSyP. Celem publikacji jest przedstawienie własności BSyP, jako obiektu eksploatacji i wzajemnego związku procesu eksploatacji technicznej z procesem zmiany stanu technicznego BSyP. Przedstawiono wyniki analizy w zakresie funkcjonalności i potencjału użytkowego BSyP. W publikacji szczególną uwagę zwrócono na własności BSyP jako obiektu eksploatacji. Dokonano analizy możliwych zasad eksploatacji BSyP oraz omówiono zalety i wady tych zasad tj.: użytkowania nienaprawialnego BSyP do uszkodzenia, użytkowania naprawialnego BSyP do uszkodzenia, obsługiwania technicznego okresowego, obsługiwania diagnostycznego ciągłego. Przedstawiono propozycję modeli sterowania w systemie eksploatacji BSyP.

8

Wear processes in precise pairs of hydraulic control devices

Ułanowicz L.

Journal of KONES

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2016

|

Vol. 23, No. 1

405--412

EN

One of the most important tasks in a complex of activities aimed at increasing the use quality of a hydraulic drive are studies concerning the impact of operating conditions of hydraulic precise pairs on their durability. With supercritical values of the slide velocity, there is a stepwise and rapid quantitative characteristics of the wear process on the surface of a hydraulic precise pair’s elements. The phenomenon of wear by oxidation and the occurrence of adhesive seizing (tacking), created in the course of the process of mutual impact of surfaces of hydraulic precise pairs in control devices, under load resulting from a hydraulic drive’s pressure pulsation requires thorough consideration. The paper discusses operating conditions of slider pairs of hydraulic control devices associated with the kinetics of their movement and their load conditions. They were supported by results of empirical studies. General characteristics and mechanism of the wear by oxidation in a slider control pair was presented. The impact of loss of stability of a control spring in a slider control pair and the relative displacement of pair’s elements during the operating process, on the character and intensity of the adhesive seizing event were discussed. The conditions of occurrence of adhesive seizing in hydraulic slider pairs, under load resulting from pressure pulsation in a hydraulic drive were discussed.

9

Modelling of a process, which causes adhesive seizing (tacking) in precise pairs of hydraulic control devices

Ułanowicz L.

Eksploatacja i Niezawodność

|

2016

|

Vol. 18, no. 4

492--500

EN

Lack of complete knowledge in the scope of the impact of operating conditions of precise pairs of hydraulic units on the character of the destructive processes arising in them, results in not taking these conditions into account at the early stages of design and manufacturing. One of such little described issues are factors causing adhesive seizing (tacking), created during the process of interaction between slider surfaces of pairs of hydraulic control devices under contact-vibration load. The articles presents general characteristics and mechanisms causing adhesive seizing (tacking) in precise pairs of hydraulic control devices under contactvibration load. It also presents a model describing the process, which causes adhesive seizing (tacking) in a slider hydraulic pair under contact-vibration load. The model allows to carry out both, qualitative, as well as quantitative analysis of the impact of vibration and load parameters on the occurrence of adhesive seizing (tacking) in slider pairs of hydraulic control devices. Practical application of the model requires the determination of the values of coefficients, which characterise the intensity of restoration and seizing resistance of metal oxides on cooperating surfaces of a hydraulic pair. An empirical method for estimating coefficients of the model and an example of estimating model coefficients for a pressure increase limiter were presented.

PL

Brak pełnej wiedzy w zakresie wpływu warunków pracy par precyzyjnych zespołów hydraulicznych na charakter powstawania w nich procesów destrukcyjnych powoduje, że na etapach projektowania i wytwarzania nie uwzględnia się tych warunków. Jednym z takich mało opisanych zagadnień są czynniki wywołujące zacieranie adhezyjne (sczepianie), powstające w procesie wzajemnego oddziaływania powierzchni suwakowych par hydraulicznych urządzeń regulacyjnych przy obciążeniu kontaktowo-wibracyjnym. W artykule przedstawiono ogólną charakterystykę i mechanizmy wywołujące zacieranie adhezyjne (sczepianie) w hydraulicznych parach precyzyjnych urządzeń regulacyjnych przy obciążeniu kontaktowo-wibracyjnym. Zaprezentowano model opisujący proces wywołujący zacieranie adhezyjne w suwakowej parze hydraulicznej przy jej obciążeniu kontaktowo – wibracyjnym. Model pozwala przeprowadzić zarówno jakościową, jak i ilościową analizę wpływu parametrów wibracji i obciążenia na wystąpienie zacierania adhezyjnego (sczepiania) w suwakowych parach hydraulicznych urządzeń regulacyjnych. Praktyczne wykorzystanie modelu wymaga określenia wartości współczynników charakteryzujących intensywność odtwarzania i opór ścierania tlenków metalu ze współpracujących powierzchni pary hydraulicznej. Przedstawiono empiryczną metodę szacowania współczynników modelu i przykład szacowania współczynników modelu dla ogranicznika narastania ciśnienia.

10

Wear processes of hydraulic plunger and barrel assemblies connected with the time of their work

Ułanowicz L.

Journal of KONES

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2014

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Vol. 21, No. 4

515--524

EN

The article discusses the wear processes of hydraulic plunger assemblies connected with the time of their work and the impact exerted by these processes on the value of parameters of a hydraulic plunger pump. It describes working conditions and loading of a hydraulic plunger assembly. The paper presents also the results of empirical analyses of the wear process of the connection of the plunger base with the working surface of the swivel disk, which is related to time and conditions of its work. It discusses the impact of the loading value and sliding speed on the character and intensity of the wear of the connection between the plunger base and the working surface of a swivel disk. Furthermore, it presents a general characteristic and mechanism responsible for the wear of the hydraulic plunger assembly through oxidation. The article also analyses the impact of the hardness of materials used for producing the hydraulic plunger assembly on the intensity of its wear. Another issue is the dependence of the coefficient of friction in the hydraulic plunger assembly on the contact pressure at different sliding speeds. Finally, the paper discusses the impact of wearing of the cooperating plunger base and the working surface of the swivel disk on the initial parameters of the hydraulic pump at a given working pressure and its volumetric efficiency.

11

Theoretical issues associated with the evaluation of the technical condition of avionic hydraulic drives on the basis of information received from means for unbiased flight control of aircrafts

Ułanowicz L.

Journal of KONBiN

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2014

|

No. 3 (31)

41--52

EN

The paper explains how to benefit from information acquired from means for unbiased flight control and to use it for technical condition assessment demonstrated by the aircraft. There are two control parameters that are provided by the means of unbiased flight control and convey the highest trustworthiness and troubleshooting content. The first one is the duration of pressure drop across the avionic hydraulic drive after switching the driving unit off with the span from the upper measured limit to the lower limit. The second one is the total time of the cycle when the pressure drops below the specific threshold and then is restored to that threshold during a hydraulic motor movement (an on-board aircraft actuator). The suggested method enables real time evaluation of technical condition attributable to avionic hydraulic drives, is quick and entails no additional expenses.

PL

Celem pracy jest przedstawienie możliwości wykorzystania do oceny stanu technicznego lotniczego napędu hydraulicznego metody polegającej na wykorzystaniu informacji ze środków obiektywnej kontroli lotu. Największą wiarygodność oraz wartość diagnostyczną mają dwa parametry kontrolne uzyskane ze środków obiektywnej kontroli lotu. Pierwszy to czas spadku ciśnienia w lotniczym napędzie hydraulicznym od górnej wartości pomiarowej do dolnej wartości pomiarowej po wyłączeniu zespołu napędowego. Drugi to czas spadku ciśnienia poniżej określonej wartości i jego powrotu do tej wartości w czasie ruchu silnika hydraulicznego. Proponowana metoda daje możliwość bieżącej oceny stanu technicznego lotniczego napędu hydraulicznego, jest szybka i bezkosztowa.

12

Experimental method of determining characteristics of power and torque engine for low-power unmanned aerial vehicles

Jastrzębski G., Ułanowicz L.

Journal of KONES

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2011

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Vol. 18, No. 3

135-142

EN

The article presents an analytical determination of power and torque of internal combustion engines of small power. It measured actual power and torque characteristics of internal combustion engines of small power. Three types (methods), braking (receiving power via a hydraulic pump, generator and a package of propellers with variable angle of attack. For each method of receiving power (braking) determined the characteristics of torque and power. There is the summary of results for one engine with different ways of braking. There have been evaluation of the presented methods inhibit combustion piston engines of small power as methods for determining power internal combustion engines. The analysis methods presented in the perspective of the braking engine selection for light unmanned aircraft, and the use of parameters derived from research into engine control. Subject to the evaluation method of adjustment (increase) charged, increasing the load on a liquid or ankle. The criterion for comparing methods for inhibition of internal combustion engines of small power load assumed dependence on the rotational speed n, and obtain maximum power on the motor shaft when the throttle, a reflection of the actual engine operating parameters in its target applications.

13

Effect of dynamic properties attributable to hydraulic lines onto operation of avionic

Ułanowicz L.

Journal of KONES

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2011

|

Vol. 18, No. 4

535-542

EN

The present paper is dedicated to discuss how dynamic parameters of a hydraulic line intended to transfer hydraulic power from a source of hydraulic power (a hydraulic pump) to an actuating device (a hydraulic motor) can affect operation of an avionic hydraulic drive. Avionic hydraulic drives are operated with fast-varying waveforms of flow intensities and pressures. It is why analysis of most hydraulic drive systems must take account of compressibility of working fluid and elasticity of hydraulic lines. It leads to a wave model for propagation of energy variation down a hydraulic line (a pipe). The paper deals with flow of a compressible liquid via a hydraulic line with flexible walls. Theoretical deliberations were successfully verified by experimental research studies that were carried out on a dedicated test bench, therefore the presented amplitude vs. frequency characteristic curves of the hydraulic line could be obtained from both theoretical considerations and experimental research studied. The experimental research studies were carried out for hydraulic line terminated with a fixed flow restrictor alone and a flow restrictor combined with a hydraulic accumulator as well as for a hydraulic line supplied from a source of constant pressure and terminated with a valve with adjustable flow together with a hydraulic accumulator. The theoretical calculations for the amplitude vs. frequency characteristic curve are based on a model for a hydraulic line with its resistance depending on frequency.

14

Properties of homogeneous flow of hydraulic fluid retaining gap

Ułanowicz L.

Journal of KONBiN

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2011

|

No. 1 (17)

283--296

EN

This paper presents the laminar flow of homogeneous liquids in crevices of smooth hydraulic resistance. The paper presents a theoretical model for the distribution of pressure in the gap and the flow rate through the slot hydraulic. The presented theoretical models for the distribution of pressure and flow in the gap on conventional hydraulic resistance of hydraulic joints, whose shape is related to the errors of their execution. In deriving the theoretical models, by introducing a variable height of the gap in the initial episode, was founded stream velocity profile variability in the hydraulic fluid retaining gap and zero values of local losses at the entrance to the slot. An analysis of the validity of the simplifications adopted in the given formulas for the distribution of pressure and flow in the hydraulic gap and on the basis provides guidelines for estimating the energy losses that occur cracks in the hydraulic resistance.

PL

W artykule przedstawiono zagadnienia przepływu laminarnych cieczy jednorodnych w gładkich hydraulicznych szczelinach oporowych. Przedstawiono wzory teoretyczne na rozkład ciśnień w obszarze szczeliny oraz natężenia przepływu przez szczelinę hydrauliczną. Przedstawione wzory teoretyczne na rozkład ciśnień i natężenia przepływu w szczelinie hydraulicznej dotyczą typowych hydraulicznych szczelin oporowych, których kształt związany jest z błędami ich wykonania. Przy wyprowadzaniu wzorów teoretycznych, przez wprowadzenie zmiennej wysokości szczeliny we wstępnym jej odcinku, założono zmienność profilu prędkości strugi cieczy w hydraulicznej szczelinie oporowej oraz zerowe wartości strat lokalnych na wejściu do szczeliny. Dokonano analizy zasadności przyjętych uproszczeń w podanych wzorach na rozkład ciśnień i natężenia przepływu w szczelinie hydraulicznej i na jej podstawie przedstawiono wytyczne dotyczące szacowania strat energetycznych jakie mają miejsce w hydraulicznych szczelinach oporowych.

15

Analiza oddziaływania na suwak hydraulicznej pary precyzyjnej promieniowych sił hydrostatycznych

Ułanowicz L.

Prace Naukowe Instytutu Technicznego Wojsk Lotniczych

|

2010

|

nr 27

5-20

PL

W artykule przedstawiono zagadnienie dotyczące oddziaływania na suwak hydraulicznej pary precyzyjnej promieniowych sił hydrostatycznych. Omówiono pochodzenie hydrostatycznych sił promieniowych w parze suwakowej i efekt ich niezrównoważenia. Przedstawiono zarys obliczeń ilustrujących działanie na cylindryczny suwak promieniowych sił hydrostatycznych oraz omówiono przyczyny występowania zjawiska klinowania się suwaka cylindrycznego w tulei. Dokonano jakościowej oceny sił promieniowych występujących na cylindrycznym suwaku oraz przedstawiono wielkości ich niezrównoważenia. Jakościowa ocena sił promieniowych w hydraulicznej parze precyzyjnej dotyczyła kilku charakterystycznych wariantów nierównomiernego rozkładu ciśnienia cieczy roboczej w szczelinie pierścieniowej utworzonej przez suwak i tuleję. Omówiono również sposoby zmniejszenia niezrównoważenia sił promieniowych ciśnienia cieczy działających na cylindryczny suwak pary hydraulicznej.

16

Analisys of influence a radial hydrostatic forces on precise hydraulic pair

Ułanowicz L.

Prace Naukowe Instytutu Technicznego Wojsk Lotniczych

|

2010

|

nr 27

21-36

EN

What has been presented in the paper is a question of influence a radial hydrostatic to precise hydraulic pair. The origins of hydrostatic radial forces in a sliding pair and the effect of this imbalance have been discussed. Computations have been outlined to illustrate how radial hydrostatic forces affect the cylindrical slide. Reasons for the cylindrical slide getting wedged in the sleeve have also been shown. Qualitative assessment of radial forces on the cylindrical slide located in the sleeve has been carried out, and the amounts of imbalance - shown. The qualitative assessment of radial forces in the precise hydraulic pair included a few characteristic variants of a non-uniform distribution of pressure of the working liquid in the annular clearance between the slide and the sleeve. The ways of reducing the imbalance of radial forces from liquid's pressure that affect the cylindrical slide of the hydraulic pair.

17

Examination of hydraulic amplifiers in the aspect of lifetime prediction

Jastrzębski G., Ułanowicz L.

Journal of KONES

|

2010

|

Vol. 17, No. 3

165-172

EN

The paper presents the lifetime analysis for a hydraulic amplifier and considers two types of the flow distributing devices, i.e. a linear distributings lider and a rotarys lider. Description of essential properties associated with operation of distributing devices in hydraulic amplifiers is included with particular attention to analysis of processes that affect wear and tear of hydraulic amplifiers and influence quality of their operation. In that context a set of parameters that determine operation quality of hydraulic amplifiers was found out where mutual independence of the parameters, their unambiguousness and measurability served as the criteria for selection there of two methods of analysis were used that took account for the foregoing assumption, i.e. the method of maximum informative capacity of the parameter and the method that assumes maximum alteration of the technical condition due to execution of the test. The completed examinations made it possible to find out characteristic curves for hydraulic amplifiers with a linear distributing slider as well as with a rotary slider with regard to their accumulated operation time. Further predictions of the hydraulic amplifier lifetime take advantage of the assumption that the deterioration effect of functional parameters attributable to hydraulic amplifiers is represented by a series of time-related values (y1,y2.....yn)i.e. a set of discrete observations {y1=ksi(teta)} associated with an unsteady stochastic process ksi(teta). The relationships how functional parameters o f a hydraulic amplifier vary in pace with its operation time t are described by means of the Gaussian distribution with the assumption that the course of a functional parameter deterioration corresponds to its aggregated characteristic curve that represents resistance of a distributing device embedded into a hydraulic amplifier to wear and tear processes. Wear of crucial parts within a hydraulic amplifier is measured in terms how functional parameters of that part associated with its accuracy, sensitivity and switching speed are getting worse and worse as time goes by.

18

Analysis of dynamic properties of hydraulic lines for fluid power transmission

Ułanowicz L.

Journal of KONES

|

2010

|

Vol. 17, No. 3

467-475

EN

This paper presents the results of a hydraulic line dynamic properties analysis taking into account inertia of the fluid flowing in rigid and flexible lines, the compressibility effect for this fluid and the viscous friction effect. The following are described and analyzed: solution of the wave equation in the form binding four variables: pressure and flow rate at the line input, and pressure and flow rate and the line output; two of the above-mentioned variables should be regarded as independent (input) and the other two as dependent (output), the accuracy comparison of distributed parameters model to lumped parameters model with regard to applicability range in hydraulic systems analysis, pressure value at given installation points as a response to rapid valve closing (transient response) or to valve opening (waterhammer effect). In these considerations the hydraulic line is regarded as a two-port with two inputs and two outputs with a definite transmittance matrix. Main considerations concern the variable resistance model. A general solution is given as a function of the Laplace operator. Introducing appropriate simplifications into the variable resistance model, the constant resistance model and lossless line model is obtained. Also, general solutions for three different lump parameter models are presented. For the lumped parameters lin presents three equivalent models possible, i.e. as: a symmetrical two-port, a two-port with shared resistance and a two-port with capacitance at the output.

19

Violation of the steady-state friction behaviour of a precise hydraulic pair due to imbalanced radial hydrostatic force

Ułanowicz L.

Journal of KONBiN

|

2010

|

No. 2-3 (14-15)

333-350

EN

W hat has been presented in the paper is a question of violation of the steady-state friction behaviour of a sliding hydraulic pair due to imbalanced radial hydrostatic force that affects the pair. The origins of hydrostatic radial forces in a sliding pair and the effect of this imbalance have been discussed. Computations have been outlined to illustrate how radial hydrostatic forces affect the cylindrical slide. Reasons for the cylindrical slide getting wedged in the sleeve have also been shown. Qualitative assessment of radial forces on the cylindrical slide located in the sleeve has been carried out, and the amounts of imbalance - shown. The qualitative assessment of radial forces in the precise hydraulic pair included a few characteristic variants of a non-uniform distribution of pressure of the working liquid in the annular clearance between the slide and the sleeve. The ways of reducing the imbalance of radial forces from liquid's pressure that affect the cylindrical slide of the hydraulic pair.

PL

W artykule przedstawiono zagadnienie dotyczące naruszenia stabilności tarcia w suwakowej parze hydraulicznej w wyniku oddziaływania na nią niezrównoważonej promieniowej siły hydrostatycznej. Omówiono pochodzenie hydrostatycznych sił promieniowych w parze suwakowej i efekt ich niezrównoważenia. Przedstawiono zarys obliczeń ilustrujących działanie na cylindryczny suwak promieniowych sił hydrostatycznych oraz omówiono przyczyny występowania zjawiska klinowania się suwaka cylindrycznego w tulei. Dokonano jakościowej oceny sił promieniowych występujących na cylindrycznym suwaku oraz przedstawiono wielkości ich niezrównoważenia. Jakościowa ocena sił promieniowych w hydraulicznej parze precyzyjnej dotyczyła kilku charakterystycznych wariantów nierównomiernego rozkładu ciśnienia cieczy roboczej w szczelinie pierścieniowej utworzonej przez suwak i tuleję. Omówiono również sposoby zmniejszenia niezrównoważenia sił promieniowych ciśnienia cieczy działających na cylindryczny suwak pary hydraulicznej.

20

Właściwości dynamiczne układu hydraulicznego jako linii obciążonej impedancją

Ułanowicz L.

Pneumatyka

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2009

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nr 4

30-33

PL

Znajomość właściwości dynamicznych linii hydraulicznej jest niezbędna ze względu na możliwość analitycznej oceny intensywności pulsacji ciśnienia występującej w uktadzie hydraulicznym, a tym samym możliwość takiego projektowania uktadów, aby nie występowały w nich te szkodliwe pulsacje.