- TITLE:
INFLUENCE OF THE INITIAL STEAM PARAMETERS ON THE OPERATION EFFICIENCY OF THE SHIP UTILIZATION TURBINE
- AUTHOR(S):
V. Aftaniuk* , B. Garagula, S. Aboleshkin, Y. Korovaichenko
- ABSTRACT:
The search for technical solutions aimed at improving the reliability of marine steam turbines
(including exhaust-driven turbines), which have a part of the expansion process in the two-phase
zone (wet steam), is an important issue in the operation of marine power plants. To date, not all
practically important tasks of two-phase mechanical environments are fully resolved. Questions of
optimization of lattices and shapes of flowing parts of the turbines working on water charged steam
remain open. No less important in this regard is the correct choice of parameters and the distribution
of heat differences by stages of the turbine. Research work in the field of water charged steam
turbines shows the need to develop specific recommendations for the most efficient (in terms of
energy loss and erosion wear of the blades) their operation. The purpose of this study is to develop
recommendations for the optimal choice of parameters of the stages of steam turbines running on wet
steam. The results of the analysis of the influence of the initial steam pressure in the last stages of
wet-steam ship turbines allows to avoid unfavorable (in terms of final humidity) operating modes and
thus increase their efficiency and erosion reliability. The most economical mode of operation for
recycling steam turbines that use low-potential heat of exhaust gases and operate in the field of wet
steam with a significant level of humidity is the mode in which the steam pressure at the inlet of the
turbine is about 0.7 MPa. An increase of this pressure leads to a significant increase of humidity
and, consequently, a decrease in efficiency. Reducing the pressure by less than 0.6 MPa significantly
affects the efficiency of the turbine due to the reduction of the available heat transfer, which makes
the use of exhaust-driven turbines impractical.
- PAGES:
7-
- TITLE:
EXPERIMENTAL INVESTIGATION ON THE HEAT TRANSFER ENHANCEMENT IN SINGLE FLOW BY WIRE-COIL INSERTS
- AUTHOR(S):
P. Bonev, V. Petkov, H.Hristov
- ABSTRACT:
This paper presents heat transfer enhancement in single-phase transitional flow by wire-coil
insert with geometrical parameters rib height-to-diameter ratio e/D=0.063, and rib pitch-to-height
ratio p/e =5.6 ÷12.2. The paper presents variation of friction factor and heat transfer coefficient in
the ranges of Reynolds and Prandtl numbers as 1100
- PAGES:
6-
- TITLE:
EFFECT OF SLIDING VELOCITY ON MICROSTRUCTURE OF DIAMOND BURNISHED 41Cr4 STEEL COMPONENTS
- AUTHOR(S):
V. P. Dunchev
- ABSTRACT:
In this article, the effect of the sliding velocity on the microstructures of diamond burnished
41Cr4 steel components was studied. The object of a comparative analysis of the microstructures of
the surface and subsurface layers are three specimens. The specimens were diamond burnished with
the same process parameters, but with different sliding velocity magnitudes: 50, 200, 300 m/min. The
analyses of the microstructures were conducted using an NEOPHOT 2 metallographic microscope at
X100, X400, and X800 magnifications. It was found that the generated heat increasing in the contact
zone between the diamond tip and the surface been treated due to the increase of the sliding velocity
is not sufficient for phase transformations in the surface layers of the studied steel. On the other
hand, the higher sliding velocity increases the plasticity in the surface layers, which effect is reflected
in changes in the microstructure - there is a tendency to modify the granular perlite to a fibrous
structure.
- PAGES:
5-
- TITLE:
MODELING AND OPTIMIZATION OF THE ROUGHNESS AND MICROHARDNESS IN DIAMOND BURNISHING OF CuAl8Fe3 BRONZE
- AUTHOR(S):
V. P. Dunchev, D. K. Drumeva
- ABSTRACT:
In this article, the object of the experimental study is diamond burnishing of cylindrical
specimens made of bronze CuAl8Fe3 in terms of the roughness obtained and microhardness. For this
purpose, planned experiment, analysis of variance and regression analysis were performed
sequentially. The governing factors were the spherical surface radius of the diamond tip, burnishing
force and feed rate. Based on the regression models obtained of the roughness and surface
microhardness, one-objective optimizations under the minimum roughness criterion and maximum
surface microhardness, and two-objective optimization of the studied process were conducted. As a
result, the respective optimal values of the governing factors were established. Using the governing
factor optimal values obtained from the two-objective optimization, the impact of the number of
passes and working scheme (one-way or two-way) on the roughness obtained and surface
microhardness was additionally studied. It was established that the implementation of the diamond
burnishing process with four passes in the conditions of one-way operating scheme provides
roughness of m075.0R a and surface microhardness of .305HV050
- PAGES:
4-
- TITLE:
SURFACE LAYER TEMPERATURE-DEPENDENT CONSTITUTIVE MODEL OF BRONZE CuAl8Fe3, SUBJECTED TO DIAMOND BURNISHING
- AUTHOR(S):
V. P. Dunchev, D. K. Drumeva
- ABSTRACT:
In this article, the temperature-dependent constitutive model of CuAl8Fe3 bronze is developed,
using the "flow stress"concept. The model defines the dependence between the stress and strain
tensors for a point on the surface layer subjected to diamond burnishing. The adequacy of the chosen
constitutive model was achieved by comparing the deformed state of the surface layer obtained via
an experimental test (indentation test) and inverse finite element analysis of the experimental test.
The developed constitutive model takes into account the temperature influence on the surface and
sub-surface layers of CuAl8Fe3 bronze in the range of (20 ÷ 250) ° C . The model serves the fully
coupled thermal-stress finite element analysis in order to study the stressed and strained state in
rotational components made of bronze CuAl8Fe3, subjected to diamond burnishing.
- PAGES:
3-
