CC BY
19
SRSTI 55.03.14; 68.85.39
A. K. Kurmanov1, N. A. Kamysheva2
'd.t.s., professor, department of «Mechanical engineering», Kostanai State University named after A. Baytursynov, Kostanay, 110000, Republic of Kazakhstan;
2senior lecturer, department of «Mechanical engineering», Kostanai State University named after A. Baytursynov, Kostanay, 110000, Republic of Kazakhstan e-mail: '[email protected]; [email protected]
TO THE QUESTION OF THE OPTIMAL CONFIGURATION OF THE IMPACT-CENTRIFUGAL CRUSHER 'S VANE
The works of leading scientists in the field of material crushing are analyzed. Conclusions are made about the expediency ofusing shock-centrifugal machines in thefield of feed production. The analysis of scientific publications on the determination of the parameters of grinders affecting the work process is carried out. Theoretically, the influence of the blade configuration in the form of brachistochrone of the accelerating disk on productivity and specific energy intensity is proved. The results of experiments are presented. Essential factors and optimal parameters of the experimental crusher are established.
The authors come to the conclusion that the optimal parameters of the impact-centrifugal crusher for grinding the peas are: the number of revolutions per minute—2000, the feeding of peas into the receiving chamber is 400 kg/h, the number of blades-6, the installation of the blades-12 deg. The clearance between the disc and the crusher body is 3-4 mm
Keywords: crushing, rotor, scapula, ugod, brahistochrone, productivity, specific energy intensity.
INTRODUCTION
Today, it is necessary to choose rational ways of grinding, allowing to achieve the desired quality of grinding and reduce specific energy consumption.
Shredding by the impact method is the most expedient, since it allows to achieve an improvement in the quality of grinding and a reduction in the specific energy intensity.
Nowadays, impact crushers are widely used for commination operations because of their high size-reduction ratio, easy modification of the product and a relatively simple design.
The earlier analysis of the physical and mechanical properties of peas and the main types of shredders has shown that at the present time classical theory of crushing is not allowed in full, for example, because they can be applied for comparative evaluation and justification of grinding methods
One of the working part of the crusher involved in grinding is a disk with mounted on it an accelerating vane. The question of the configuration of the vanes is still unclear.
According to G. Oskalenko [1], if the circumferential velocity does not change, the velocity of the particle depends on the design of the rotor, the configuration and orientation of the vanes on the acceleration disk, and the friction coefficient of the material.
V. Sadov and V. Sadovaya, in their works proved that the configuration of the vanes leads to a large increase in the absolute velocity, and this directly affects the number of impacts that must be applied to destroy the material [2].
G. Zuev, A. A. Kukibny. [3, 4] provide data on the location of the vanes relative to the axis of rotation on the disk, indicating the bending of the ends of the vanes in the direction opposite to the direction of rotation in order to earlier relieve the weight of the cargo at a smaller angle of rotation.
S. Zolotarev [5], in turn, has been proposed and studied the percussion-centrifugal crusher feed grains from the counter-rotating rotors which fixing the flat operating parts.
N. Sergeev noted the advantages of the radial arrangement of the vanes on the acceleration disk, such as a reduction in power consumption, as compared to inclined vanes [6].
M. Dusenov, N. Japarov [7] proposed a design that contains an accelerating disk with a blade in the form of a logarithmic spiral in order to increase productivity.
The property of a logarithmic spiral consists in the constancy of the angle formed by the tangent with the radius of the current point.
O. Semkiv and V. Shatokhin [8] in their studies compared the speed of the particle and its time on the rectilinear and curved vanes of the priming thrower.
The design has the same goal as the impact - centrifugal crusher - to develop the maximum speed of the particle in the minimum time.
MAIN PART
The curvilinear vane shape was found as a solution to the problem of brachistochrone in the field of centrifugal inertia forces. The choice of curvilinear surface of the vane in the form of brachistochrone is due to the fact that one of the most important characteristic features of the optimal curve is that the polar radius passing through its initial point is a tangent to the curve at this point.
This means (physically) that at the beginning of the movement the centrifugal force of inertia is close to the direction of motion, i.e. provides the maximum acceleration, which is not possible with the use of a rectilinear vane (the case where the rectilinear vane is located along the radius is not satisfactory from a technological point of view). Considering the conservation of linear momentum of the system particle-crushing bar before and after impact, Attou et al. derived [9] the following expression for the impact energy per unit mass
E = 0.5-(R + 0.5-Hh)2-a)2 (1)
where R(m) is the rotor radius, Hb(m) is the height of the impact surface of the crushing bars and ©(s-1) is the rotor angular velocity.
In vertical-axis crushers, the particles are fed to ahorizontal turning table (rotor) with radially oriented guides and are projected towards the crushers walls by the centrifugal forces. Unlike in hammer crushers, here most of the fragmentation takes place at the crushers walls rather than at the rotors periphery. With the assumption that the particle energy does not change during its flight from the rotor periphery to the crushing walls, i.e., the particle-particle interactions are neglected in a first approximation, Nikolov and Lucion derived [10] the following expression for the impact energy per unit mass
where Rv(m) and ®(s-1) are the rotor radius and angular velocity respectively. The notation Rvis used to distinguish between the impact energy for hammer and vertical-axis crushers given with eqs. (3) and (4) respectively.
It is interesting to note that for the same rotor radius, the impact energy per unit mass provided by hammer crushers is lower than that provided by vertical-axis crushers. This could explain the fact that vertical-axis crushers produce more fines and perform better when finer granulate must be reduced in size, which is most probably due to the higher level of impact energy reached in these machines [11].
The quantity of material passing per unit time may be determined by the following equation [12]
where q is the vane capacity, kg/s;
d3 - is the equivalent particle diameter, m; u - is the velocity of the particle moving along the vane, m/s; p - density of the crushed material, kg/m3;
Then the productivity of the impact - centrifugal crusher will depend on how much material is captured by all the vanes.
Q = k3^-pz (4)
here Q - is the productivity of the shredder, kg/s; k is the filling factor of the interscapacity space; z - number of vanes., units.
Also, the performance depends on the diameter of the grinder receiving chamber. V. Lyapin [13] in his work focuses on what is necessary to take into account the specific structural thickness of the vane, in this case the formula takes the form of performance
Q = (nD0 - zS)d3dp (5)
where S is the thickness of the vane, mm.
Considering that with increasing the number of vanes the distance between them will decrease and can reach a critical value, i.e. it may become smaller than the particle size and the crusher will not work.
Therefore, the number of vanes will be limited
z <---(6)
nD 0
d3 + ô
With this formula, the expression for determining the performance takes the following form:
(nrfj2p0
Q = T{STm)^
The coefficient of the interscapular space Kz for peas of the variety «Altai mustached» = 0.89 [12]. Taking this coefficient into account, the formula takes the form
(it d3)2D0 ,
c = '■ÏÛÏS)'" <7)
The particle velocity is calculated by the formula:
в = ш R (8)
so,
(nd3)*D0 (9)
V z 4(d3 + 5)
It can be seen from the equation, that the productivity of the impact - centrifugal crusher depends on the diameter of the receiving chamber (the feed of grinding), the rotational speed of the disk, the radius of the vanes , their number and thickness, and also on the properties of the material to be crushed.
In the theoretical part of the study we obtained an equation that allows us to construct the trajectory of the motion of the particle along the vane, all the components of the total velocity of the particle were determined. Its direction and magnitude.
The analytical dependence of the crusher performance is determined, taking into account its design and operating parameters.
To verify the results of theoretical studies in the training workshop of the engineering and technical faculty of A. Baytursynov Kostanay state university we developed a prototype of a crusher.
During the experiment, we changed the factors: feeding feed, shaft rotation frequency, vane deflection angle from the normal (Figure 1). The criterion of optimization was the specific energy intensity.
Based on search experiments, literature data and expert opinions were chosen levels and ranges of variation factors, and the factors themselves are presented in Table 1.
Table 1 - Factor encoding
Code The amount of the feed material, Q, kg / h Shaft rotational speed, n, r / min Angle of deviation shoulder vanes from the normal axis, 9, deg
Х1 Х2 X3
+ 400 2600 30
0 300 1750 20
- 200 900 10
The influence of structural, kinematic and technological parameters of the crusher on the specific productivity and the degree of grain refinement was revealed in the study using the methods of active experiment planning (symmetric noncompositional quasi D-optimal Pesochinsky plan and coding factors) [14].
Figure 1 - Accelerate disks with installed vanes CONCLUSION
Based on theoretical and experimental studies, we established significant factors and optimal design-regime parameters of the experimental crusher.
A new design of a pea impact - centrifugal crusher was proposed (Innovative Patent No. 77987. Innovative Patent No. (11) 27012 Published on 11/04/2012, Bul, 2012, No. 4), which provides high quality grinding performance, low energy consumption of the process, achieved due to a reasonable choice of rational, regime and design parameters, namely: 2000 rpm, the number of vanes-6, the angle from the axis normal of the vane-12 degrees, feeding the material into the crusher 400 kg/h.
The clearance between the accelerate disc and the crusher body is 3-4 mm.
REFERENCES
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Material received on 14.02.18.
А. К. Курманов1, Н. А. Камышева2
Ортадан тепюш соккы усаткыш ^рекшенщ оцтайлы конфигурациясы мэселес1 женшде
1,2А. Байтурсынов атындь^ы Крстанай мемлекеттiк университетi, Костанай к., 110000, Казахстан Республикасы.
Материал баспаFа 14.02.18 тYстi.
А. К. Курманов1, Н. А. Камышева2
К вопросу об оптимальной конфигурации лопатки ударно-центробежной дробилки
1,2Костанайский государственный университет им. А. Байтурсынова,
г. Костанай, 110000, Республика Казахстан. Материал поступил в редакцию 14.02.18.
Материалды усацтау саласындагы жетекшi галымдардъщ e^eKmepi талданады. Азыц-тулж вшмдерш вндipу саласындагы ортадан тепюш соццы машиналарды цолданудыц орындылыгы туралы цорытынды жасалды. Жумыс процесте эсер ететт тегютеуШтердщ параметрлерш аныцтау бойынша гылыми жарияланымдарга талдау жypгiзiлeдi. Теориялыц тургыдан, жылдамдыцты дискiдeгi брахистохрон туршде пышац
конфигурациясыныц ешмдшкке жэне нацты энергия сыйымдылыгына эсерi дэлелденЫ. ■Эксперименттердщ нэтижелерi усынылды. Эксперименталды усацтагыштыц негiзгi факторлары мен оцтайлы параметрлерi белгiлендi.
Авторлар буршац тегютеушке арналган ортадан тепкш соццы усацтагыштыц оцтайлы параметрлерi: минутына айналымдар саны — 2000, цабылдау камерасына буршацты беруi — 400 кг/саг, курекшелердщ саны — 6, цалацшаны орнату бурышы — 12 градус болып табылады деген тужырымга келдi. Дисктщ аралыгында сацылау жэне усатцыштыц турцысы — 3*4 мм.
Проанализированы труды ведущих ученых в области дробления материалов. Сделаны выводы о целесообразности применения ударно-центробежных машин в области кормопроизводства. Проведен анализ научных публикаций по определению параметров измельчителей, влияющих на рабочий процесс. Теоретически доказано влияние конфигурации лопатки в виде брахистохроны разгонного диска на производительность и удельную энергоемкость. Приведены результаты экспериментов. Установлены существенные факторы и оптимальные параметры экспериментальной дробилки.
Авторы приходят к выводу, что оптимальными параметрами ударно-центробежной дробилки для измельчения гороха являются: число оборотов в минуту-2000, подача гороха в приемную камеру — 400 кг/ч, число лопаток-6, угод установки лопатки — 12 град. Зазор между диском и корпусом дробилки — 3—4 мм.
