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THEORETICAL FOUNDATIONS FOR IMPROVING THE COOLING SYSTEM OF AN
INTERNAL COMBUSTION ENGINE
Giyasidinov Abdumannob Sharokhidinovich
Senior Lecturer of the Department of "Transport Logistics"
of the Andijan State Technical Institute
Annotation:
In this article, the theoretical foundations of cooling power supply for internal
combustion engines (ICE) from motor vehicles are studied. First of all, the design structure,
operating principles, and efficiency levels of existing cooling systems were analyzed. The
processes of supplying the engine's thermal system through physical and mathematical modeling
of heat exchange processes in the cooling system are highlighted. A comparison of the
operational benefits and air-based cooling systems revealed the advantages and disadvantages of
the file. High-performance heat exchange equipment has been proposed for the commissioning
of a new generation of cooling systems. Based on computer modeling and experimental tests,
energy efficiency control is aimed at ensuring power reliability. This study has practical
applications in the automotive industry, agricultural machinery, and other agricultural machinery,
highlighting the effectiveness of internal combustion engines.
Keywords:
cooling, car, environment, transport, engine, transport, effect, radiator, water pump,
pump, mathematical model, (ICE), modeling, differential.
Introduction. For different refrigerators (in this case, air and coolant), heat transfer is different
and specific. For each of them, physical characteristics are a function of temperature, and some
are a function of pressure. The mathematical description of the heat transfer process is as follows:
-
heat conduction equations;
-
equations of motion;
-
equations of complexity;
-
heat transfer equations;
-
unique equations.
To date, analytical solutions of the system of differential equations of convective heat transfer
are obtained only for a limited number of simple problems when introducing certain simplified
assumptions. This is explained by the high complexity of the equations, as well as the
complexity and versatility of the described processes.
Due to the limited possibilities of the analytical solution of the above differential equations, the
experiment is of great importance in the study of heat transfer processes. Experimental study of
complex heat engineering processes, depending on many factors, has high costs, duration, and
labor intensity.
Re=idem; Pr=
For a certain class of experimental problems arising under the conditions of
forced movement of heat exchangers, similarity theory is applied. Similar heat exchange
processes can fulfill the following conditions: idem.
In this case, the Reynolds number (Re) determines the hydromechanical behavior of the cooling
water flows:
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Re=
ω
0
l
v
, ' ( 2 . 1 )
ō
0
where is the average velocity of movement of a liquid or gas, usually at the beginning of the
system;
l
-characteristic geometric dimension of the system;
v
-kinematic viscosity coefficient of
cooling water.
The Prandtl number (Pr) is the thermophysical characteristic of the refrigerator. Contains only
physical parameters:
Pr=
μc
p
λ
=
v
a
( 2 . 2 )
y=m/ ra=l/c
p
r
Here: and - the numerical value of the temperature conductivity coefficient given
in the tables.
The equality of the numbers Re and the identity of the numbers rg ensures thermal similarity, i.e.,
the similarity of the fields of temperature pressures and heat flows throughout the entire volume
of the systems under consideration[1].
According to similarity theory, such processes must be identical and have a definite number of
similarities. In convective heat exchange processes, the determined Nusselt number is Nu, which
characterizes the intensity of the convective heat exchange process:
Nu=
αl
λ
( 2 . 3 )
Thus, the state of identification of similarity numbers (Pr, Re = idemidem) is a condition for the
variability of the numbers that determine similarity. This ensures the similarity of the processes.
The similarity equation for convective heat transfer processes with forced refrigerant movement,
characteristic of the operating process of a cooling radiator, has the following form:
Nu=f R e , P r
( 2 . 4 )
However, most experts emphasize that the use of similarity criteria can be achieved only with
strict adherence to the rigidity of the physical parameters of the environment and thermal
engineering constants. With a significant change in properties, the analysis shows that strict
analogy between different processes is completely impossible. These cases do not allow the use
of analytical dependencies on the working flow of the radiator when constant and stochastic
changes in cooling water flows occur.
The threshold values of the radiator's performance criterion are determined by. The amount of
heat released by the engine in the coolant:
Q
D
=632
AN
e
( 2 . 5 )
Here:
a=
q
D
632
N
e
=
f(N
e
,
n
D
,
t
l
'
,
T
w
"
,
G
V
)
( 2 . 6 )
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193
N
e
n
D
t
l
'
,
t
W
"
G
W
Here:
a
-experimental coefficient; -engine power, W; -crane shaft rotation speed,
rpm; -radiator outlet and inlet temperature and air temperature in the liquid, °C; -mass airflow,
kg/s.
In real operating conditions, the radiator cannot serve as a convenient criterion due to its
complexity, reflecting the heat ratio of one useful cycle of cooling water supply to many factors.
The values of this coefficient vary widely. For the maximum load mode, a = 0.8...1.4 (for
carburetor engines) and a = 0.45...0.9 (for diesel engines). For radiator-guaranteed drainage, the
maximum coefficient values are taken: a = 1.4 (for a carburetor engine) and a = 0.9 (for a diesel
engine). Thus, the radiator's heat transfer values are:
Q
p
karb
carb≥885n
e max
va Q
p
diz
≥569
n
e max
( 2 . 7 )
At the same time, the critical values of the radiator's thermal conductivity according to the
formula can be used only for the operation of the radiator as part of the cooling system. When
removing the radiator from the vehicle, the aerodynamic and hydraulic flow regime of the cooler
for measuring heat transfer on the stand changes significantly. It is known that the potential
characteristics of a radiator in a car depend on many factors.
∆
Q
ppo
=
Q q
P
0
−∆
q
ICE
0≤
τ≤Т
At the design stage, reserves were installed to eliminate the effects
of operational pollutants - two heat releases of at least 10% of the maximum calculated heat
value emitted. The heat transfer reserve for the new radiator (corresponding inscriptions) is a
guarantee of its service life with t in the range 0≤τ≤t:
Q
D
≤
q
D
+
Q
PPR
≤
Q
P
0
(2.16)
When outputting a constant value, conversion gives:
0 ≤≤Q
Q
p p τ ≤ Q
pp0
( 2 . 1 7 )
Q
rr0
, the operating conditions of the radiator Q
rr0
are expressed in relative, dimensionless units:
0 ≤
qrτ
≤ l , ( 2 . 1 8 )
Here q
RTS
-parameter reflecting changes in the radiator's heat transfer reserve during operation.
The rate of the heat transfer depletion process can be described by the following differential
equation:
dq
pτ
d
τ
=
d
(
k
τ
F
∆
t
)
d
τ
,
0≤τ≤T ( 2 . 1 9 )
and
k
r
=
l
R
τ
,
( 2 . 2 0 )
r
τ
here: t-total thermal resistance, operational pollutants (m°C) /W; t-treatment of the boundary
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state. Qpt>0 is considered a decreasing function from the experiment.
A solution of a differential equation can yield a very approximate result when applying various
iteration methods or mathematical modeling of real operating conditions [4].
When the radiator's performance under operating conditions is steadily disrupted, it is dismantled
to restore its functionality by cleaning. In this case, it is possible to clean the outer surface of the
radiator and restore the shape of the ribbed plates of the air ducts. As a result, with a constant
front radiator area (
F=
:
const
), there is no effect of aerodynamic resistance on the average
temperature pressure ∆t, the differential equation can be simplified:
dq
pτ
d
τ
=
dk
τ
d
τ
=
d
(
l
Rτ
)
d
τ
( 2 . 2 1 )
Statistical studies have shown that after operation under certain operating conditions of the
radiator t, the total thermal resistance will be:
R
r
=
R
r max
∙(1−
e
−
Bτ
)
( 2 . 2 2 )
R
r r max
Here: - maximum total thermal resistance, which tends to approach the pollution curves
asymptotically over time (with the maximum possible layer thickness); v - experimentally
determined through the values of thermal resistance in the permanent, temporary working
segment.
In practice, along with the process of stochastic contamination of cooling surfaces, periodic
cleaning is carried out to a degree determined by the methods of their cleaning and the nature of
the accumulated contamination. This process is also stochastic, which creates additional
difficulties in determining the radiator's heat transfer reserve. Figure 2 uses a graphical
interpretation of the radiator's pollution and cleaning process.
CONCLUSION
In conclusion, theoretical research has been conducted on improving the cooling system of
internal combustion engines. Information on the operating principle and analytical characteristics
of the heat exchange process of the radiator, which is one of the most important parts of the
cooling system, is presented. In addition, the amount of heat released by the engine of the
coolant in the pradiator was calculated, and recommendations were developed.
References:
1.
Omonov FA, Jorayev VI PROBLEMS AND CAUSING FACTORS IN THE
DEVELOPMENT OF FERGANA CITY PUBLIC TRANSPORT //European Journal of
Emerging Technology and Discoveries. - 2021. - Vol. 1. - No. 2. - pp. 72-75.
2.
Islamjon og JV et al. CONVENIENCES CREATED FOR PASSENGERS WHEN USING
PUBLIC TRANSPORT SERVICES //Education news: research in the 21st century. - 2021.
- Vol. 2. - No. 14. - pp. 138-146.
3.
Islamjon og' QK and others. METHODOLOGY FOR RATING THE CONSUMPTION OF
MATERIAL RESOURCES IN THE OPERATION OF THE BUS FLEET // Mechatronics
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and Robotics: Problems and Development Prospects. - 2021. - Vol. 1. "No." 1. - Pp. 266-267.
4.
Ikramov N. et al. Analysis of transport and its cargo processes // E3S Web of Conferences.
EDP Sciences, 2024. - Vol. 548. - Б. 105-110.
