Problem Statement of Air-Feed Research on Frictional Surfaces of the Brake Assembly Taking into Account Effect of the Laval Nozzle

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629.33: 593.3

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Abstract

For cooling of drum type brake assemblies of the timber-hauling machines, carryover of wear debris from a friction zone it was recommended to fan the compressed air on device’s  frictional surfaces. It has been established that for increase of efficiency factor and stability coefficient of the brake assembly, the compressed air is required to be fan to a friction zone before braking process i.e. before brake shoes to adjoin to a brake drum. In this case, braking process will be with more "pure" frictional surfaces. It is experimentally established that air feed before braking process led to increase of braking force on an experimental wheel for 14 %. It was required to prove theoretically this result and to make mathematical model of process of the expiration of the compressed air on frictional surfaces. Authors paid attention that the gas expiration on frictional surfaces of the brake assembly behaves as the gas expiring from the Laval nozzle. Therefore in article process of air effluxion on surfaces of the brake assembly as process the gas expiration through the Laval nozzle is considered. The nozzle consists of frustum of cone couple interfaced by the narrow ends. Thus it is known that: at a subsonic speed of gas movement – the nozzle is narrowed; at a supersonic speed of gas movement – the nozzle extends; at gas movement of equal acoustic speed – the area of a nozzle cross section reaches an extremum that is it has the narrowest section called the critical. According to this, the following conclusions were drawn: the compressed air which arrives on frictional surfaces of the brake assembly in the course of their operation from bringing unions, hypothetically behaves as gas which proceeds through the Laval nozzle; frictional surfaces cooling of the brake assembly in the course of braking, carryover of wear debris from a zone of friction, moisture and dirt, and also the balance of forces normal to frictional surfaces, probably, to consider according to the physical phenomen which are characteristic for the gas passing through the Laval nozzle and washing, in our case, frictional surfaces; for the analysis of course of this physical process it is required to execute its qualitative mathematical description and to carry out a number of the exact, difficult experiments proving its existence.

Authors

D.G. Myasishchev, Doctor of Engineering, Professor, A.S. Vashutkin, Candidate of Engineering, Senior Lecturer, A.M. Shvetsov, Postgraduate Student Northern (Arctic) Federal University named after M.V. Lomonosov Naberezhnaya Severnoy Dviny, 17, Arkhangelsk, 163002, Russia; е-mail: d.myasishchev@narfu.ru

Affiliation

Northern (Arctic) Federal University named after M.V. Lomonosov

Keywords

the Laval nozzle, local gas density, local gas pressure, local gas speed, local acoustic speed of gas, brake assembly, gap.

References

1.Vashutkin A.S., Myasishchev D.G. Analiz funktsionirovaniya barabannykh tormoznykh mekhanizmov avtolesovozov i puti uluchsheniya ikh pokazateley [Analysis of Drum Brakes Functioning of Log Trucks and Ways of Improving their Performance]. Lesnoy zhurnal, 2010, no. 3, pp. 61–68. 2. Vashutkin A.S. Uluchshenie ekspluatatsionnykh svoystv tormoznoy sistemy lesotransportnykh mashin: dis. … kand. tekhn. nauk [Running Ability Improvement of Brake System of Timber-Hauling Machines: Cand. Tech. Sci. Diss.]. Arkhangelsk, 2012. 139 p. 3. Landau L.D., Lifshits E.M. Teoreticheskaya fizika. T.6: Gidrodinamika [Theoretical Physics. Vol.6: Hydrodynamics]. Moscow, 1973. 733 p.