An implantable ventricular assist rotordynamic blood pump is being developed by the Cleveland Clinic Foundation in cooperation with the NASA Lewis Research Center. At the nominal design condition, the pump provides blood flow at the rate of 5 liters per minute at a pressure rise of 100 mm of mercury and a rotative speed of 3000 RPM. Bench testing of the centrifugal pump in a water/glycerin mixture has provided flow and pressure data at several rotative speeds. A one-dimensional empirical based pump flow analysis computer code developed at NASA Lewis Research Center has been used in the design process to simulate the flow in the primary centrifugal pump stage. The computer model was used to size key impeller and volute geometric parameters that influence pressure rise and flow. Input requirements to the computer model include a simple representation of the pump geometry. The model estimates the flow conditions at the design and at off-design operating conditions at the impeller leading and trailing edges and the volute inlet and exit. The output from the computer model is compared to flow and pressure data obtained from bench testing

Golding, Leonard A. R.

Horvath, David

Medvedev, Alexander

Smith, William A.

Veres, Joseph P.

English

NASA Technical Reports Server

NASA Technical Memorandum 107463
Flow Analysis of the
Centrifugal Pump
Cleveland Clinic
Joseph E Veres
Lewis Research Center
Cleveland, Ohio
Leonard A.R. Golding, William A. Smith,
David Horvath, and Alexander Medvedev
The Cleveland Clinic Foundation
Cleveland, Ohio
Prepared for the
43rd Annual Conference
sponsored by the American Society for Artificial Internal Organs
Atlanta, Georgia, May 1-3, 1997
National Aeronautics and
Space Administration
https://ntrs.nasa.gov/search.jsp?R=19970017001 2020-06-16T02:08:54+00:00Z

Flow Analysis of the Cleveland Cfinic Centrifugal Pump
Joseph P. Veres
Computing and Interdisciplinary Systems Office
NASA Lewis Research Center
Cleveland, Ohio
Leonard A. R. Golding, William A. Smith,
David Horvath, Alexander Medvedev
Department of Biomedical Engineering,
The Cleveland Clinic Foundation, Cleveland, Ohio
Abstract:
An implantable ventricular assist blood pump
is being developed by the Cleveland Clinic
Foundation in cooperation with the NASA
Lewis Research Center. At the nominal design
condition, the pump provides blood flow at
the rate of 5 liters per minute at a pressure rise
of 100 mm of mercury and a rotation speed of
3000 RPM. Bench testing of the centrifugal
pump in a water/glycerin mixture has provided
flow and pressure data at several rotative
speeds. A one-dimensional empirical based
pump flow analysis computer code developed
at NASA Lewis Research Center has been
used in the design process to simulate the flow
in the primary radial pump stage. The
computer model was used to size key impeller
and volute geometric parameters that influence
pressure rise and flow. Input requirements to
the computer model include a simple
representation of the pump geometry. The
model estimates the flow conditions at the
design and at off-design operating conditions
at the impeller leading and trailing edges and
the volute inlet and exit. The output from the
computer model is compared to flow and
pressure data obtained from bench testing.
Introduction:
The Cleveland Clinic Foundation (CCF) has
had a long involvement with non-pulsatile
ventricular assist blood pumps (Reference 1)
and is currently developing an Innovative
Ventricular Assist System (WAS), which has
been previously reported in Reference 2.
Continued development of the IVAS has
resulted in a pump with improved
performance over earlier prototypes. The cross
section of the current WAS configuration is
shown in Figure 1. The new IVAS pump
configuration contains a new primary impeller
featuring a reduced axial height blades. The
axial height of the impeller blade has been
reduced from previous builds in order to
increase the average velocity, and to reduce
the spanwise velocity profile at the impeller
exit (Figure 2). The flowpath at the impeller
shroud has been modified to increase the local
radius of curvature near the leading edge. The
new shroud contour provides a gradual
Figure 1. IVAS pump assembly featuring new primary
impeller, shroud towpath and volute.
transition from axial flow near the impeller
inlet, to radial flow within the blades. The
blade number has been increased from six to
NASA TM- 107463 1
seven blades in order to increase the work
performed by the centrifugal impeller. The
blade number increase reduced the flow
deviation from the exit bladeangle.The new
impeller also featuresblades with reduced
normal thickness.
IVAS PriMary ImpelLer
Builds 216, 220
Figure 2. Centrifugal pump impeller with reduced axial
height and blade thickness.
A new volute housing has also been designed
to match the new impeller exit geometry. The
new volute tongue, or cutwater, has been
designed to have reduced levels of incidence
with the flow exiting the impeller. Figure 3
shows the new volute housing with additional
pressure taps located near the impeller shroud
region of the housing for data taking purposes.
Pressure taps number 1 to 6 are on the primary
impeller inlet end of the pump at three radial
locations located 180 degrees apart. Pressure
taps number 7 to 10 are on the secondary
impeller end of the pump at two radial
locations.
Methods:
Bench testing of the current IVAS pump
configuration in the water/glycerin mixture
has provided flow and pressure data at several
speeds.
Data from the pressure taps located within the
pump housing show the radial pressure
gradient in the primary and the secondary
impellers at off-design flows (Figure 4). The
pressure rise in the volute is greatest near the
--!!
Figure 3. Pump housing with volute scroll and exit
diffuser. Also shown are the pressure tap locations in
the housing.
nominal design condition of 3000 RPM and 5
LPM, as can be seen in Figure 4. The highest
pressure rise from the impeller exit to the
volute discharge indicates that the cutwater
angle and the area distribution within the
volute are matched at the design operating
condition.
IVAS RADIAL PRESSURE DISTRIBUTION
BUILD # 220 3000 RPM
TESTED FEB lO, 1997
-..... ii;
............ ....
1_0' J0' 20 ' 2° i j0 , , , , , t I I , I20 40 GO BO
LOCAL PRESSURE - PUMP INLET PRESSURE (nMHg)
Figure 4. Test data taken at the primary and secondary
impeller shrouds showing the radial pressure gradients.
NASA TM- 107463 2
To assist in the design and development
process, a one-dimensional computer model
was created of the pump primary impeller
using the PUMPA flow code (References 3, 4,
5). The PUMPA code was developed at the
NASA Lewis Research Center to provide a
rapid analytical capability of pump
configurations for a variety of aerospace
applications. The pump code is based on the
Euler equation with empirically derived values
of rotor slip factor and efficiency. The code
can be used to estimate the relative and
absolute velocities, flow angles and static and
total pressures at the rotor leading and trailing
edges. It models head, flow, speed and power
and creates performance maps. The map
generation capabilities of the PUMPA code
provides the information needed for inter-
facing with a concurrently developed system
model.
The Innovative Ventricular Assist System
(IVAS) pump is analyzed using the flow
modeling code. To enable modeling the IVAS
pump, the fluid properties of a mixture of
glycerin and water were added to the pump
code. The application of the pump code to the
IVAS required a validation phase. IVAS pump
test data was obtained at the Cleveland Clinic,
using a water/glycerin mixture as a surrogate
fluid in place of blood. Key parameters within
the pump code were validated and post-test
analysis of the data yielded the key parameters
of slip factor (normalized value of flow
deviation angle), impeller efficiency and
volute loss coefficient. The pump flow model
with the modified parameters matched the
head-flow-speed and power maps that were
obtained from laboratory testing.
The overall pump performance in Figure 5
shows the pressure rise versus flow that was
achieved at 3500, 3000 and 2500 RPM for a
range of flow conditions. Figure 5 also
150
E
E
_r
50
i i i i I i 1 i i 1 i i i i I
5 1o 15
Flow, LI_I
Figure 5. IVAS pump test data at 3500, 3000 and 2500
RPM, compared to values obtained from the computer
flow model.
illustrates the sensitivity of the pump
performance to the shroud clearance at the
primary impeller face. The difference in axial
running clearance between builds 216 and 220
was 0.004 inches. Varying the value of shroud
clearance did not significantly affect high
system efficiency.
Figure 5 also shows the comparison between
the one-dimensional flow model and the test
data, for a range of flow conditions at three
speeds. The pump pressure rise is influenced
mainly by the primary impeller, the volute and
exit diffuser. The secondary impeller does not
contribute significantly to the overall pressure
rise, since the flow through it is relatively low,
compared to the primary impeller. The flow
model compares closely to the test data for
most flows, except near the regions of low
flow, where there is some difference between
the model and the data.
The pump overall efficiency of the IVAS is
shown in Figure 6. The efficiency is defined as
the output hydraulic power divided by the
electric power required to drive the pump. The
overall efficiency includes the hydraulic losses
NASA TM- 107463 3
through the primary and the secondary
impellers, as well as the volute, bearing and
the annular duct formed by the rotor outer
diameter and the casing. Electrical losses
within the motor and motor driver are also
included in the overall efficiency parameter.
O25
090
:_ 0.15
0
W
¢.10
CCF IVAS Pump
f
m • x
/ I
ID
_ ///41 i
.z i_•
,/,//
0.05 /;aY
//
//
0.00 T _ r t
¢
--O-- '2eaO0 RPU Oata
5 J 10 15
_, LPM
_J
/++_Figure- 6.IVAS pump overall efficiency of pump,
bearing and motor.
The input electric power required to drive the
pump is shown in Figure 7.
IVAS Pump Power
_" 10
!
_ a
O-
ILl
q
g. 4
-I S _
.::::: ._+- .... ..
_
--_-- _o00 RP_d Data
I I I r I _ t I = I _ r t t I
5 10 15
Row, LPM
Figure 7. Electric power required to drive the IVAS
pump.
Results:
The calculated values of velocity and flow
angles near the impeller leading edge, during
C_z = 2.39
I"t" Uz = 6.11
Figure 8. Absolute and mlalive velocities at the
primary impeller leading edge, from the pump
flow model.
pump operation at the nominal design point
(3000 RPM and 5LPM) are shown in
Figure 8. The flow calculations are performed
at the root-mean-square radius. The pump
flow model is based on the prewhirl at the
inlet to the impeller of zero degrees, resulting
in the inlet absolute flow angle (a) of
90degrees and a relative flow angle of
21.3 degrees from the tangential direction. On
tests of early prototype configurations, there
was evidence of prewhirl at the pump inlet.
Planned large scale tests with visualization
techniques will determine the impeller inlet
prewhirl at a range of flow and speed
conditions to confirm a reduced level of
prewhirl.
The flow conditions at the impeller trailing
edge were likewise calculated by the computer
model. Figure 9 shows the velocities and
angles as calculated by the pump flow code.
CM2 =2.06
..... -W2 =4.94
c_= +z99J"_...--l_'-,?'-.
+;;; . =
,f,"
4 U2 =1Z32 ]
C v2 = 1Z83 .l_
Figure 9. Absolute andrelative velocities at the primary
impeller trailing edge, from the pump flow model.
Discussion:
The impeller exit velocity vector triangles
illustrate the difference between the ideal and
the actual velocity vectors. This difference at
the impeller exit results in the deviation of the
NASA TM- 107463 4
flow angle (78 degrees) from the blade angle
(24 degrees). There is flow deviation at the
exit of all centrifugal pumps and its magnitude
is influenced by key parameters such as the
number of impeller blades and the exit blade
angle. A reduced level of deviation has the
effect of increasing the pressure rise in the
pump. Future research will focus on further
design improvements to the impellers,
including quantifying the inlet prewhirl and
reducing the levels of impeller incidence and
deviation. To realize further improvements in
pump performance, analysis with higher
fidelity flow codes will be done at the Ohio
State University College of Engineering, as
well as at NASA Lewis Research Center.
Conclusion:
The hydraulic performance of the IVAS pump
(build #220) has been characterized by bench
testing with a water/glycerin mixture in a
laboratory environment. The present pump
configuration has met the performance design
goals established by the Cleveland Clinic
Foundation and the data has confirmed the
computer flow model of the primary impeller,
as well as the match between the impeller and
volute.
Acknowledgments:
Funding for the IVAS program has been
provided by the National Institute of Health,
and the National Heart, Lung and Blood
Institute under NIH contract NHLBI-HV-94-
25. Support for the work at NASA Lewis
Research Center has also been provided by
the High Performance Computing and
Communication Program (HPCCP). The
success of the IVAS program can be attributed
to the efforts of all the members of the WAS
design team which also includes the Ohio
State University College of Engineering,
Mechanical Technologies Incorporated, Smith
& Nephew Richards and the Ohio Aerospace
Institute (References 6, 7).
Symbols:
a = Flow angle in absolute frame of reference, degrees
B = Flow angle in relative frame of reference, degrees
C = Fluid velocity in absolute frame of reference, ft/sec
U = Blade tangential velocity, ft/sec
W = Fluid velocity relative to the blade, ft/sec
Deviation = Blade angle (B O2) - flow angle (B/=2)
RPM = rotations per minute
LPM = liters per minute
Subscripts:
1 = Impeller leading edge (inlet)
2 = Impeller trailing edge, (exit)
3 = Vaneless diffuser exit
4 = Volute exit diffuser exit
U = Tangential component of velocity
M = Meridional component of velocity
References:
1. Golding L.R., Harasaki H., Loop F.D., Use of a
Centrifugal Pump for Temporary Left Ventricular
Assist Systems", Transactions of the American Society
for Artificial Internal Organs, 1978; 24: 93-7.
2. Golding L.A.R., Smith W.A., D.R. Bodman, "The
Cleveland Clinic Rotodynamic Pump Program",
International Society for Artificial Organs 1996; 20(6):
pp. 481-484.
3. Veres, J.P., "Centrifugal and Axial Pump Design
and Off-Design Performance Prediction", JANNAF
Joint Subcommittee and Users Group Meetings,
Sunnyvale,CA., Oct 17-21, 1994, NASA TM-106745.
4. Veres, J.P. "Centrifugal and Axial Pump Design and
Off-Design Performance Prediction", 1996, COSMIC
Inventory, LEW-16173, The University of Georgia,
Athens, Georgia, 1996.
5. Veres, J.P. "Centrifugal and Axial Pump 1-D Flow
Code and User's Guide", 1997, NASA TM-4740.
6. Xu, L. "Development of a High Power Density and
High Efficiency Motor for Artificial Hearts",
Transactions of the American Society of Artificial
Internal Organs", 1997.
7. Malanoski, S. "The Analysis, Design and Testing of
a Blood Lubricated, Hydrodynamic Journal Bearing",
Transactions of the American Society of Artificial
Internal Organs, 1997.
NASA TM- 107463 5
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REPORT DOCUMENTATION PAGE OMBNo. 0704-0188
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1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED
May 1997 Technical Memorandum
4. TITLE AND SUBTITLE 5. FUNDING NUMBERS
Flow Analysis of the Cleveland Clinic Centrifugul Pump
6. AUTHOR(S)
Joseph P. Veres, Leonard A.R. Golding, William A. Smith, David Horvath,
and Alexander Medvedev
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)
National Aeronautics and Space Administration
Lewis Research Center
Cleveland, Ohio 44135-3191
9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)
National Aeronautics and Space Administration
Washington, DC 20546-0001
WU-509-10-1A
8. PERFORMING ORGANIZATION
REPORT NUMBER
E-10749
10. SPONSORING/MONITORING
AGENCY REPORT NUMBER
NASATM-107463
11. SUPPLEMENTARY NOTES
Prepared for the 43rd Annual Conference sponsored by the American Society for Artificial Internal Organs, Atlanta,
Georgia, May 1-3, 1997. Joseph P. Veres, NASA Lewis Research Center; Leonard A.R. Golding, William A. Smith,
David Horvath, and Alexander Medvedev, The Cleveland Clinic Foundation, Department of Biomedical Engineering,
Cleveland, Ohio (work funded under IAA YI-HV-7016-02). Responsible person, Joseph P. Veres, organization code
2900, (216) 433-2436.
12a. DISTRIBUTION/AVAILABILITY STATEMENT
Unclassified- Unlimited
Subject Category 34
This publication is available from the NASA Center for AeroSpace Information, (301) 621-0390.
12b. DISTRIBUTION CODE
13. ABSTRACT (Maximum 200 words)
An implantable ventricular assist rotordynamic blood pump is being developed by the Cleveland Clinic Foundation in coop-
eration with the NASA Lewis Research Center. At the nominal design condition, the pump provides blood flow at the rate of
5 liters per minute at a pressure rise of 100 mm of mercury and a rotative speed of 3000 RPM. Bench testing of the centrifugal
pump in a water/glycerin mixture has provided flow and pressure data at several rotative speeds. A one-dimensional empirical
based pump flow analysis computer code developed at NASA Lewis Research Center has been used in the design process to
simulate the flow in the primary centrifugal pump stage. The computer model was used to size key impeller and volute geo-
metric parameters that influence pressure rise and flow. Input requirements to the computer model include a simple represen-
tation of the pump geometry. The model estimates the flow conditions at the design and at off-design operating conditions at
the impeller leading and trailing edges and the volute inlet and exit. The output from the computer model is compared to flow
and pressure data obtained from bench testing.
14. SUBJECT TERMS
Centrifugal; Pump; Flow; Analysis; Blood; Ventricular assist; Model; Volute;
Water; Meanline
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