IJSRD - International Journal for Scientific Research & Development| Vol. 1, Issue 3, 2013 | ISSN (online): 2321-0613
CFD Analysis of C. I. Engine Cooling Water Pump of car
Bhavik M.Patel1 Ashish J. Modi2 Prof. (Dr.) Pravin P. Rathod3
1
PG Student, Mechanical Engineering Department
2
Assistant Professor, Mechanical Engineering Department
3
Associate Professor, Mechanical Engineering Department
1, 2, 3
Government Engineering College, Bhuj
Keywords: Water pump, Engine cooling system, simulation,
CFD, ANSYS, Cooling water pump Geometry, cavitation,
coolant flow, flow characteristics
I. INTRODUCTION
Automobile Cooling pump is the key part of the Automobile
cooling system that keep circulate the coolant throughout it
and takes away excess heat from engine at different Engine
rpm and torque conditions. Also its surrounding atmospheric
conditions can vary coolant characteristics. This research
involves the investigations on the existing coolant pump of
car (Maruti SUZUKI Alto), to understand the flow
characteristics. The research is carried out in three
approaches to understand the behavior of fluid. The first one
is "Theoretical approach" in which Empirical relations are
used. It describes how the desired pump operating
parameters such as flow rate, specific speed of pump etc.
can be derived. It also describes the coolant characteristics
& understanding of flow characteristics in the closed,
pressurized automobile cooling system. The another one is
"Practical approach" in which flow rate and fluid pressure of
pump flow are measured on existing coolant pump of Maruti
SUZUKI Alto at different engine rpm. The third approach
involves the “Computational Fluid Dynamics" of pump
flow, which itself provides graphical representation of the
relations between flow characteristics and pump geometry.
The "Result discussion" section provides brief discussion on
the results which are derived after these three approaches.
II. THEORITICAL APPROACH
Below steps has been carried out to obtain desired coolant
flow rate.
 Obtained heat rejection data for specific engine model
and rating. This information is available from the
engine technical data sheet. Maximum heat rejection
(nominal + tolerance) values are used.
 Obtained density and specific heat values for coolant.
Table 1 provides these values for the specific coolant.
 Using these values in Empirical equations we can
calculate coolant flow rate as below.
A. Heat Rejection by Engine Calculation:
Before a coolant flow rate can be calculated, we must
calculate how much heat is being rejected through the
engine. The heat input to the engine equals the sum of the
Pump Flow Rate(Kg/s)
Abstract-To study behaviour of flow in cooling water
pumps, we done extensive search and gone through
numerous research paper and blogs.We found that many
researchers carried out their analysis on other cooling
system components like radiator, cooling water jacket and
fans. But it is very difficult to find researchers worked on
cooling water pumps. However cooling system consists of
centrifugal pump which is widely used in other industry.
After reviewing all research paper on centrifugal pumps we
found that most of the problems are related to cavitation and
low efficiency. Some researchers give importance to
improvement of blade angle and blade design to reduce
cavitation effect while some researches concentrates on
efficiency of the pump irrespective of cavitation effect
mostly in the industry where cavitation effect is negligible.
After analyzing some old water pumps of various vehicles
we found that major problem that pump is facing is due to
cavitation effect on blades at High RPM. This research is
aimed to analyze the role of centrifugal water pump in
automobile engine cooling system and to obtain relation
between pump geometry and pump flow characteristics.
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
2000
4000
Pump RPM
Fig. 1: Power - Engine RPM - Torque Curve Required Pump
RPM - Pump Flow Rate Curve
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CFD Analysis of C. I. Engine Cooling Water Pump of car
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B. Coolant Flow Calculation:
The coolant flow required for different heat load from the
engine components to the radiators can be calculated using
the following equation:
SAE 2001 paper states that conventional coolant flow rate
on smaller engines with mechanically driven water pumps
vary between 2.0 to 2.6 L/min/Kw. The flow rate derived
from the above equation falls under this criteria. Graph 1
represents Pump rpm v/s flow rate curve based on above
equations.
C. Specific Speed:
Specific speed is a number characterizing the type of
impeller in a unique and coherent manner. Specific speed
are determined independent of pump size and can be useful
comparing different pump designs. The specific speed
identifies the geometrically similarity of pumps.
√
(
)
Typical values for specific speed - Ns - for different designs
in US units (US gpm, ft)
 Radial flow - 500 < Ns< 4000 - typical for centrifugal
impeller pumps with radial vanes - double and single
suction. Francis vane impellers in the upper range
 mixed flow - 2000 < Ns< 8000 - more typical for mixed
impeller single suction pumps
 axial flow - 7000 < Ns< 20000 - typical for propellers
and axial fans
By calculation, the specific speed value falls between 10002000 under different operating condition. So it suggests
using radial vane impeller pump and the actual pump used
in existing cars also proves true that the car coolant pumps
are centrifugal pumps with radial vanes.
D. Typical Coolant Characteristics
The engine’s cooling system is designed to meet specific
guidelines. The proper coolant/antifreeze will provide the
following functions:






Adequate heat transfer
Compatibility with the cooling system’s
components such as hoses, seals, and piping
Protection from water pump cavitation
Protection from other cavitation erosion
Protection from freezing and from boiling
Protection from the build-up of corrosion, sludge,
and scale
Following graph represents the Engine coolant saturation
pressure at different fluid temperature. Though cavitation is
the phenomenon of "constant temperature boiling due to low
pressure" that is due to sudden increase in the fluid velocity
at pump inlet when impeller suck the fluid so there is sudden
pressure drop of fluid. Table 1 show the coolant properties
when the fluid temperature is 80 deg. C.
15
Saturation Pressure (psi)
Heat and work outputs. From following equation, heat input
values are derived with the use of Power - Torque - Speed
curve. As per SAE papers, the total heat output of engine is
the sum of total exhaust heat, heat loss to the surroundings,
total heat dissipated by engine coolant and total heat
dissipated by engine oil. It is also assumed that
approximately one third of total heat output is equal to the
total heat dissipated by the engine coolant. The total heat
input can be calculated as follows:
10
5
0
0
20
40
60
80
Temp in deg. C
100
120
Fig. 2: Engine coolant saturation pressure at different fluid
temperature
Coolant Property
Molar Mass
Density
Specific Heat
Thermal Conductivity
Dynamic Viscosity
Value with UNIT
0.07343 Kg/mol
1.03 Kg/m^3
3579.71 J/Kg*K
0.4153 W/m*K
2.8 Centipoise
Table. 1: Engine Coolant Saturation Pressure in psi
E. Pump Flow Characteristics
Pump inlet pressure is higher compare to saturation pressure
at different temperature to reduce cavitation effect at inlet
side.
The cooling system and its components must meet both
criteria.
A) Maximum pressure design limits. At any point in the
cooling system that exceed the maximum pressure for the
local components such as radiators etc. and
B) The minimum pressure at any location in the cooling
system shall not fall below the vapor pressure of the coolant
to prevent low pressure boiling. A minimum pressure/head
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CFD Analysis of C. I. Engine Cooling Water Pump of car
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is also required at the pump inlet to avoid cavitation,
minimize metal erosion and noise.
III. PRACTICAL APPROACH
After determining the required coolant flow rate, pump
performance establishes the maximum allowable external
resistance. Piping and heat transfer equipment resist water
flow, causing an external pressure head which opposes the
engine driven pump. The water flow is reduced as the
external pressure is increases. The total system resistance
must be minimized in order to ensure adequate flow. A
cooling system with excessive external pressure heads will
require pumps with additional pressure capacity. With
Practical approach, the pressure drop in the fluid flow can be
measured by totaling the pressure drop in each of the
system's components.
Fig. 4: Pump Geometry 1
Fig. 5: Mesh - Stationary and Rotating domain of pump flow
Fig. 3: Pressure Measurement under practical approach
IV. CFD ANALYSIS OF ENGINE COOLING WATER
PUMP
A. Define Goals
From theoretical and practical approach, pump design
parameter are obtained which affects the pump flow
characteristic. To study pump flow characteristic, Ansys
CFX is used which will provide results with graphical
representation of flow characteristic like pressure, velocity,
mass flow rate etc. at different location of pump.
B. Flow Geometry and Mesh Creation
The pump model geometry is complex and asymmetric due
to the blade and volute shape. The 3D CAD software was
used to extract pump fluid profile geometry from pump
model. The pump model specification is given bellow in
table 3. An Optimized mesh is used for analysis. The model
is divided into two domains i.e. rotating and stationary.
Hub Dia
Impeller Outside Dia
Suction Dia
Flow Type
Blade Type
No of Blade
Total Height
19.35 mm
56 mm
Impeller OD
Radial Flow
Circular 2D
7 (CCW)
23.47 mm
Table. 2: Impeller Specification
Fig. 6: Mesh - Stationary and Rotating domain of pump flow
C. Identify Domain And Boundary Condition:
In steady state type analysis, Non Buoyant, two fluid
domains are defined - Rotating & Stationary. The rotating
domain includes the fluid profile which is in contact with
the impeller while the rest of the fluid region is defined as
Stationary domain. Interfaces are defined for the fluid flow
at impeller inlet, impeller outlet, Inlet and outlet of pump
with General connection and conservative interface flux in
fluid flow. Engine coolant, a 50/50 % mixture of Ethylene
Glycol & water is defined with required properties for the
solver equation in material library. The mass transfer model
is set to cavitation and the results are investigated for
cavitation effect in pump at different pump rpm.
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CFD Analysis of C. I. Engine Cooling Water Pump of car
(IJSRD/Vol. 1/Issue 3/2013/0069)
V. RESULT
can be concluded that at very low RPM, flow is turbulent.
Also best pump efficiency with less cavitation is achieved at
medium engine speed.
VI. SIGNIFICANCE OF PUMP GEOMETRY
A common misconception about cooling systems is that if
the coolant flows too quickly through the system, it will not
have time to cool properly. Because automotive cooling
systems are a closed loop, coolant allowed to stay in the
radiator longer will also stay in the engine block longer
producing increased coolant temperatures. This can easily
lead to ‘hot spots’ and ultimately, engine failure. To avoid
these centrifugal pump increases velocity by reducing
pressure with providing sudden reduction in cross section
area at outlet of pump. Sudden reduction also result into
turbulent flow at the outlet which contradictory helps in
maintaining engine block temperatures which we can see
through above results also.
However turbulent flow at inlet leads to less pump
efficiency and also if pressure falls below vapor pressure of
coolant then it leads to pump cavitation. From above results
we can conclude that venturi effect at the inlet of the pump
helps in avoiding cavitation by increasing inlet fluid
pressure above vapor pressure at normal speed and
decreasing velocity of fluid.
Fig. 7(a)
CONCLUSION
Fig. 7(b)
The summary of the present research paper as follows:
1) By studying different design points carefully it can be
concluded that the existing pump of Alto car is
designed for best performance at normal car speed.
Pump geometry at inlet (venturi effect) avoids
cavitation phenomenon and increase pump efficiency
significantly.
2) However at low and high speed of car, pump is subject
to more cavitation. So there is scope to improve that.
3) Sudden reduction at pump outlet is observed in existing
pump, which is generally to be avoided while designing
the pump. But it helps in avoiding hot zones by
increasing velocity and making flow turbulent.
Fig. 7(c)
REFERANCES
Fig. 7(a), (b), (c): Results of Simulation
3000 RPM
2625 RPM
HEAD (ft)
2250 RPM
10
5
0
0
20
40
60
FLOW RATE (GPM)
Fig. 8: Result Comparison
Above results shows contour plots of velocity and pressure
on different planes. Below graph shows flow rate vs. head at
different engine RPM. By carefully studying each case, it
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