Wyniki wyszukiwania - BazTech

1

Lubricating Properties of Polyester Oils and R404A Refrigerant Mixtures under Starved Lubrication Conditions

Górny Kasper, Stachowiak Arkadiusz, Tyczewski Przemysław, Zwierzycki Wiesław

Tribologia

|

2022

|

nr 3

9--15

EN

There has been a dynamic shift towards the use of ecological refrigerants in the refrigeration industry. Currently, they must not contain fluorine and chlorine. The substances that deplete the ozone layer have already been withdrawn, and the refrigerants that increase the greenhouse effect are getting restricted. Until recently, R404A was a quite commonly used HFC refrigerant for commercial refrigeration equipment in both small and large systems. Although R404A refrigerant has considerable greenhouse effect potential, it has not been banned from use in existing refrigeration systems. The widespread use of R404A refrigerant requires appropriate compressor lubricants.In refrigeration compressors, the amount of oil in friction pairs in certain situations may be insufficient. In that event, poor lubrication conditions may occur. There may also be a situation in which the areas of friction lack lubricant and friction pairs are lubricated only by the refrigerant.The article contains a methodical selection of test parameters for polyester oils, allowing one to assess the lubricating properties of the mixtures of oils for refrigeration compressors and refrigerants under poor lubrication conditions. The article also includes the results of wear tests which allow one to evaluate the lubricating properties of oil-refrigerant mixtures under starved lubrication conditions for R404A refrigerant and polyester oils.

PL

Obecnie w chłodnictwie następuje dynamiczny zwrot w kierunku stosowania ekologicznych czynników chłodniczych. Dość powszechnie stosowanym czynnikiem chłodniczym z grupy HFC dla komercyjnych urządzeń chłodniczych zarówno w małych jak i dużych instalacjach był do niedawna R404A, co wiąże się z potrzebą doboru odpowiednich sprężarkowych środków smarnych. W sprężarkach chłodniczych może wystąpić sytuacja, w której ilość oleju w węzłach tarcia jest niewystarczająca. Wówczas mogą wystąpić skąpe warunki smarowania lub smarowanie tylko przez czynnik chłodniczy. W artykule przedstawiono metodyczny dobór parametrów badań pozwalających na ocenę właściwości smarnych olejów do sprężarek chłodniczych w mieszaninie z czynnikiem chłodniczym w warunkach skąpego smarowania dla olejów poliestrowych. Umieszczono również wyniki badań zużyciowych pozwalających na ocenę właściwości smarnych mieszanin olej – czynnik chłodniczy w warunkach skąpego smarowania uzyskanych dla czynnika chłodniczego R404A z olejami poliestrowymi.

2

Influence of surface texture parameters on friction characteristics under starved lubrication

Wu Shen, Zhang Pan, Wei Haijun, Chen Lei

Polish Maritime Research

|

2020

|

nr 2

96--106

EN

A cylinder liner and piston ring running under starved lubrication near the top dead centre (TDC) and bottom dead centre (BDC) cause abnormal friction and wear during operation of a marine diesel engine. The method of laser texturing is proposed to improve the surface friction property under this condition. Spherical crown pits with different parameters were formed on the surface of samples by femtosecond laser processing. The BDC and TDC conditions of oil starvation were simulated in a reciprocating friction and wear experiment, and a numerical model of Surface texture lubrication based on the Reynolds equation was established. The influence of the distribution density, diameter, and depth parameters of the texture on the surface properties was studied. In the BDC condition, compared with the untextured surface, the average coefficient of friction (COF) can be reduced by up to 24% and the average friction force can be reduced by up to 18%. In the TDC condition, the COF can be reduced by up to 19%, and the average friction force can be reduced by up to 18%. Therefore, the textures with various parameters should be arranged in different positions on the cylinder liner; more attention should be paid to the optimisation of diameter in the texture of the cylinder liner near the BDC, whereas more attention should be paid to the optimisation of distribution density in the texture of the cylinder liner near the TDC

3

Advances in Fundamental Studies on Partially Filled Tribological Gaps

Mueller M., Ostermeyer G. P.

Machine Dynamics Research

|

2018

|

Vol. 42, No. 3

5--15

EN

Tribological scenarios with partially ﬁlled gaps can occur when either a lubricated system runs under starved lubrication or a system that usually operates under dry conditions is wetted by a ﬂuid. In order to get a detailed insight into the tribological character of partially ﬁlled gaps, it is necessary to investigate the dynamics of the ﬂuid ﬂow and its interaction with the pressure, velocity, nominal gap height and deformations. Within this problem, the total amount of ﬂuid in the gap plays a crucial role. Recent studies with novel models have shown that particularly near the fully ﬁlled regime the built up pressure is highly dependent on the ﬁlling ratio. Further studies proved that the ﬂuid forms characteristic bow waves in front of asperities thus leading to larger mean pressure values in the contact. This paper extends these ﬁndings by experimental investigations on different length scales. Special focus is on the correlation between the friction coefﬁcient and the supplied ﬂuid volume.

4

Wpływ geometrii mikrowgłębień w powierzchni na właściwości tribologiczne elementów ślizgowych

Gałda L., Sęp J., Tomczewski L.

Tribologia

|

2014

|

nr 5

59--68

PL

W artykule przedstawiono wyniki badań tribologicznych węzłów ślizgowych w skojarzeniu materiałowym stal–stal. Badania realizowano z wykorzystaniem testera T-11 ze zmodyfikowanym węzłem ślizgowym typu kulka–tarcza w styku rozłożonym. Tarcza została poddana obróbce nagniataniem w celu ukształtowania w niej wgłębień. W pracy porównano wartości współczynnika tarcia w odniesieniu do współpracujących ślizgowo elementów z wgłębieniami o zróżnicowanej geometrii oraz bez wgłębień. Wykazano, że obecność oraz geometria wgłębień w powierzchni w sposób istotny wpływa na charakterystyki tribologiczne pracy badanych węzłów ślizgowych.

EN

The results of investigations of sliding pairs in material matching (e.g. steel-steel) are presented in the article. The examinations were realized with the utilization of a T-11 tester with the modified sliding pair of the type ball-disc in uniform contact. To facilitate pit formations, the disc surface was subjected to burnishing. The friction coefficient values were compared in reference to co-operating elements with pits of differential geometry and without depressions. It was demonstrated that presence and the geometry of depressions in the surface influenced the tribological characteristics of the operating sliding assemblies.