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separately. The purpose of this work was to demonstrate the
feasibility of a new impeller design and not to bring out
correlations that would help estimate different hydrodynamic
properties. Since the FI geometry that we have reported here is
just one such design/configuration of blades and energy dis-
tribution, a detailed analysis on the quantitative dependence of
the hydrodynamic properties on the fractal structure (design of
impeller, blade configuration, nature of fractal structure, etc.) is
under progress.
4. CONCLUSIONS
A new type of impeller with self-similar features is proposed
and demonstrated. The performance of the FI was compared
with the conventional impellers (DT and PBTD) on the basis of
measured power consumption, mixing characteristics, and the
efficacy in suspending the particles. The power number of FI was
relatively lower than the other standard impellers. The self-
similar structure leading to reduced drag in the absence of any
possibility of wake formation behind the impeller blades helps to
generate a uniform randomness throughout the stirred tank.
Importantly, at identical N, although the Re for FI would be
higher than that of a PBTD or DT, in reality the flow is laminar.
For suspensions, while the low density particles were seen to get
completely suspended even at very low impeller rotation speed,
the suspension of high density particles required only twice the
amount of power for identical solid loading and impeller Re. The
FI when used for gasliquid dispersion showed that relative
power demand continues to decrease with increasing impeller
rotation speed as well as the superficial gas velocity. The bubble
size distribution was very much narrow throughout the reactor
supporting the hypothesis of possible uniformity in spatial energydissipation. Different design alternatives with varied blade angles,
etc. may yield better flow but at relatively higher power con-
sumption. More details on the effect of design of FI on the
performance for different applications are under investigation.
’APPENDIX 1
Fractals: Since their discovery by Mandelbrot,
12
fractals have
experienced considerable success in quantifying the complex structure
exhibitedbymanyscientific and engineering problems. Fractals are
disordered systems described in terms of noninteger dimensions, and
the disorder is their intrinsic property. The fractals are characterized
by the property of geometrical self-similarity and independency at any
scale. The fractal character of an object/region/domain can be
quantified by a parameter called the fractal dimension, D,which
quantifies the fractal scaling relationship between the patterns,
observed at different magnifications. Fractal dimension can be best
calculated by the box counting method, which means drawing a box
of size R and counting the mass inside (M). On plotting ln(M)vs
ln(R),we get a value ofDmwhich is the fractal dimension. A vast body
of literature on fractals, their features, mathematical analysis, the
methods of characterization, and finally their applications in various
fields may be referred for details.
1418
A detailed account of the
fractals in flow and turbulence can be seen in Sreenivasan.文克•哈利托诺夫
各种类型的密封件、泵和压缩机，在莫斯科 “泵和压缩机 — 75” 国际展览展出。Pacific (Federal German Republic, FGR), Burgmann (FGR), Crane Packing (UK), Bestobell Seals (UK)等展出了特殊的机械密封搅拌器轴（由顶部和底部进入），这些公司专门生产密封装置。双平衡和不平衡的机械密封件的使用，以提供
高度可靠的操作。
顶端插入混合搅拌设备由于简单的构造和运行而被广泛应用各类反应容器。不过,这种结构也存在一定的缺点，该轴的转速是有限的，如果没有限制该轴的下端的径向和下部轴承的间隙，容许减少径向的振动与较大直径或多个刚性轴及更高的驱动程序的场合，轴的更换和修理密封和需要完成拆解搅拌器容器的上半部分，这是这种结构的另一个缺点。这种设计有利的一面在于没有液体从此容器中排出的情况下，容器内介质由于密封故障而流出的这种密封失效可能性很低。