Browsing by Subject "oscillations"

Now showing 1 - 3 of 3

Access status: Open Access ,
Methods for adjusting the braking force of winders with a traction sheave to prevent the risk of wire rope slippage
(Wydawnictwa AGH, 2021) Celebański, Władysław; Piechota, Piotr
In Koeppe winders, the emergency braking deceleration values must be higher than the values required by mining regulations and lower than the critical deceleration values due to the risk of hoisting rope slippage. Slippage of suspension ropes can lead to damage to the traction sheave lining and, in extreme conditions, serious damage to the shaft hoist. In order to limit the braking force to a safe value, the air or hydraulic oil pressure in the braking systems of winders is regulated during braking. This paper presents methods for adjusting pressure in braking systems during braking and their influence on: the risk of slippage of the suspension ropes, the dynamics of the driving system and the dynamics of the skips themselves. Particular attention was paid to the solution in which the braking force varies during the braking process which can cause large changes in the value of the force acting on the winder.
Access status: Open Access ,
Modelling of PDC drill bit whirling
(2007) Prigorovska, Tania O.
At this work it was made the attempt to explain the process of PDC drill bit whirling as an integral part of drilling in real conditions. It was shown that the causes of PDC whirling are not only the rock mass heterogeneity, but drill bit mass misbalance too and it is impossible to obtain absolutely stable drilling system. PDC drill bit previous models were based on the assumption all cutting forces are stable and that PDC drill bit oscillation is self appearable or stochastic. Based on the theory of probability it was defined the value of cutting forces on every PDC cutter and generalized drill face reaction and it was drill bit oscillation and whirling were analyzed.
Access status: Open Access ,
Storage of hydrogenous gas in geological formations - self-organisation methane gas
(2013) Toleuhanov, Amankeldy; Kaltaev, Ajdarhan; Panfilov, Mihail Borisovič
In the case of producing large amounts of hydrogenous gas, currently there are no problems related to basic techniques of hydrogen production and distribution, but the main technological problem will consists of storing it in order to regulate the difference between permanent or increasing gas production and seasonally modulated gas consumption. The most efficient and most inexpensive method of storing large amounts of hydrogen is to inject them in geological formations like aquifers, depleted gas reservoirs, or salt caverns (Zittel and Wurster 1996). The cost is of order $ 3.5 per 1 GJ (Taylor et al. 1986). Several underground storages of hydrogen (USH) or town gas exist in the word, as for instance, Teeside in the UK, in Texas, in Russia, Kiel in Germany, Lobodice in Czechoslovakia, Beynes - an ex-storage in France. During several tens of years the storage of hydrogen was considered as something deja-vu, to be similar to that of natural gas, which is amplified by the chemical inactivity of hydrogen and its very low solvability in groundwater [Bulatov 1979; Carden and Paterson 1979; Lindblom 1985; Paterson 1983]. Nevertheless, quite unusual behaviour of UHS was discovered by in situ monitoring of the gas composition extracted during the cycle »production« which followed the cycle »injection«. These observations (Smigai et al. 1990; Buzek et al. 1994) revealed high variations of gas composition in time and space. In particular, a significant reduction in the $H_2$ and $CO_2$ contents and a simultaneous increase in $CH_4$ contents were observed in the Lobodice town gas storage facility (Smigai et al. 1990). Similar phenomena were recorded in Beynes. After several months of injection and storage, at the beginning of the cycle »production« the twofold increase of the methane contents in the reservoir gas and the twofold reduction of the $CO_2$ $CO$ contents was observed. The contents of hydrogen decreased by 1.4. The explanation to these observations has been done in (Buzek et al. 1994) in terms of the in situ methane generators by methanogenic bacteria which catalyse the reaction between hydrogen and $CO_2$/$CO$, by producing methane and water. Further observations have revealed even more unusual effects within the storage facility, such as creating a spatial alternation of the areas saturated preferably by hydrogen or methane. This proved an in situ natural separation of chemical components in space. Thus, we are dealing with a natural reactor which partially destroys $CO_2$ and $H_2$ and doubles the mass of methane. It is clear that the problem is important for industry as it concerns both the energy sector and ecology. The resulting economical efficiency of such a process can be estimated only after the physical and mathematical modeling of all possible scenarios of the reservoir behaviour. The development of such a model represents the main objective of this paper.