The Results of Gas Dynamic and Strength Improvement of

Turbocharger TK-32 Axial Turbine

Valery N. Matveev, Oleg V. Baturin, Grigorii M. Popov and Daria A. Kolmakova

Department of Theory of Engine for Flying Vehicles, Samara State Aerospace University (SSAU), 34,

Moskovskoye shosse,Samara, Russia

Keywords: Axial Turbine, Turbocharger, Gas Dynamic, Plastic Deformation, Efficiency, Blade, Strain-Stress State

Analysis.

Abstract: The results of strength and gas dynamic improvement of turbocharger TK-32 axial turbine are presented.

Turbocharger was manufactured by LLC “Penzadieselmash” (Penza, Russian) and is used as unit boost for

diesel locomotive. The goal of this work was to ensure turbine work capacity when rotor speed is increased

by 10% without efficiency reduction. The strain-stress state analysis indicated the region of high stresses on

rotor blade body at the level of 2/3 of root. These stresses exceed allowable values when rotor speed is

increased. The variant of peripheral rotor blade section tangential displacement, allowing to reduce the level

of stresses by 20%, was found. Gas dynamic calculation showed that variant of rotor blade modernization

results in an increase of efficiency by 0.4%. Also it was shown that the increase in turbine efficiency by 1%

can be reached if the number of rotor blades is reduced by 13%. This recommendation was implemented

and confirmed experimentally on a mass turbocharger TK-32.

1 INTRODUCTION

Turbocharger TK-32 (Figure 1) was developed at

LLC “Penzadieselmash” (Penza, Russian

Federation) for use on diesel generator 1А-9DG

manufactured by LLC “Kolomensky Zavod”.

During turbocharger’s operation there was a

necessity of engine forcing. As a result the

turbocharger operating condition was modified. In

particular, the rotor speed of the turbocharger

increased from 25500 to 28000 revolutions per

minute (rpm). In this regard LLC "Penzadieselmash"

applied for SSAU to assess the forcing effect on the

stress strain state of the turbine TK-32 and its gas-

dynamic efficiency, and make recommendations for

their improvement (Tikhonov, Matveev, 1982).

2 GAS DYNAMIC

CALCULATION OF TURBINE

BASIC DESIGN

Three-dimensional computational model of the flow

in the turbine stage, which includes zone of flow

around the nozzle guide vane (NGV), zone of flow

around the rotor wheel (RW) and free flow area at

the outlet of the turbine, was developed in Ansys

CFX program (ANSYS - Simulation Driven Product

Development, 2014). This model was used for

investigation of gas dynamic performances of the

existing turbocharger’s axial turbine. The flow

models of NGV and RW contain only one blade

passage for reducing required computer resources

and calculation time (Bonh, Heuer, Kusterer, 2005).

Therefore, the periodic boundary conditions were

implemented on lateral boundaries of the

computational domain (Figure 2).

Finite element mesh was created such as to

provide a value of y + no more than three. The total

number of elements was 250000 in the NGV mesh,

and 500000 elements in RW mesh. Tip clearance

was simulated when the RW mesh were created. The

value of tip clearance was taken as 1 mm in

accordance with the engineering drawing.

The following boundary conditions were set

during calculation:

mass flow rate (G = 5,34 kg/s), total

temperature (T* = 773 K) and flow direction

(perpendicular to the face) were set at the

computational domain’s inlet (NGV inlet);

595

Matveev V., Baturin O., Popov G. and Kolmakova D..

The Results of Gas Dynamic and Strength Improvement of Turbocharger TK-32 Axial Turbine.

DOI: 10.5220/0005042105950600

In Proceedings of the 4th International Conference on Simulation and Modeling Methodologies, Technologies and Applications (SIMULTECH-2014),

pages 595-600

ISBN: 978-989-758-038-3

Copyright

c

2014 SCITEPRESS (Science and Technology Publications, Lda.)

outflow boundary was set constant adjustment

of the flow static pressure (p = 105000 Pa)

constant at all channel height was set at the

computational domain’s inlet (RW outlet);

to account for the RW rotation, this area was

calculated in the rotating reference frame with

rotor speed n = 25500 rpm (nominal

conditions), n = 28000 rpm (forced mode);

The model of turbulence was SST k-

. The

calculation was performed in a stationary

formulation (Bochkarev, Dmitriev, Kulagin,

Makeenko, Mosoulin, Mossoulin, 1993). Flow

parameters at RW inlet and outlet were averaged in

the circumferential direction (Mixing Plane

approach).

The flow pattern, as well as flow parameters in

all points of considered flow region at nominal mode

(n=25500 rpm) and forced conditions (n=28000

rpm) were obtained. Analysis of the flow structure in

the turbine blade passage found no areas with

unfavorable flow pattern. Some flow parameters

distribution fields at turbine nominal mode

(n=25500 rpm) are given at Figure 3 and 4.

Predicted value of turbine efficiency at this mode

was

т

=83,6%.

Figure 1: Turbocharger TK-32.

Figure 2: Computational model of the flow in turbocharger TK-32 turbine.

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Figure 3: The field of Mach number’s value distribution in absolute reference frame at turbine middle diameter.

Figure 4: The field of static pressure distribution at turbine middle diameter.

3 THE STRENGTH ANALYSIS

OF TURBINE

The pressure and temperature fields at blades

surfaces obtained from gas dynamic calculation

were used as boundary conditions in turbine rotor

wheel’s static strength calculation by means of

Ansys Mechanical program. The modal for strength

calculation contained a whole rotor wheel,

consisting of a disc, blade attachment and blade

aerofoil. Since the computational model had cyclic

symmetry, then only the sector containing one blade

was modelled during the research. The periodic

boundary condition was implemented on its lateral

surfaces (Figure 5).

The computational model was loaded with gas

(obtained earlier in the Ansys CFX program) and

centrifugal forces. Disk temperature was adopted by

the thermometry data provided by LLC

"Penzadieselmash". Since the turbine disk is welded

to the shaft, the RW calculation model was fixed by

the front and rear flanges.

The computational model was divided by mesh

of Solid 185 and Solid 186 finite elements. Special

contact elements, limiting the movement of parts,

were used in areas of fir-tree root teeth contact with

disk slot.

Stress-strain state was evaluated at two modes:

nominal mode (n = 25500 rpm) and forced

conditions (n = 28000 rpm).

TheResultsofGasDynamicandStrengthImprovementofTurbochargerTK-32AxialTurbine

597

Figure 5: Computational model for turbocharger TK-32

turbine rotor wheel’s strength analysis.

The results obtained in the computation indicated

that turbocharger’s basic turbine satisfies the

strength conditions at the nominal mode (n = 25500

rpm) as a whole. However it should be noted that the

derived load factors are dangerously close to the

minimum value. Equivalent stress maximum value

was 600 MPa at forced mode (n=28000 rpm), which

corresponds to a load factor of 1.25. This value is

below the allowable value (permissible value of 1.3).

It was also revealed that there is plastic deformation

in footing parts of disc and blade.

Noteworthy is the fact that the maximum value

of stresses can be evidenced in the upper part of the

blade body at the level of two thirds from the root

(Figure 6), which indicates that stresses are caused

by the blade bending. This conclusion is supported

by the fact that compression stresses acts on the

suction side area, located beyond the region of

maximum stress. This conclusion is indirectly

confirmed by the cases of the upper third turbine

blades shedding of the turbocharger available in use.

4 THE MODERNIZATION OF

TURBINE

Elevated bending stresses are the result of a specific

form of the rotor blade body. Its top sections are

greatly expanded relatively bottom ones, violating

the sections centring on height. As a result,

centrifugal forces acting on the periphery part, cause

the increased torque, that bends the blade body.

To reduce bending stresses peripheral sections of

the blade have to be “shifted”. Hereinafter the term

"shift" means the displacement of blade body

sections of the pen in the circumferential direction.

To reduce the bending stresses in turbocharger

TK-32 turbine rotor blade body peripheral sections

have to be shifted in the circumferential direction

toward the suction side.

The effect of shift of three peripheral sections in

circumferential direction on the rotor wheel blades’

stress strain state was investigated. The variant

allowing to reduce the maximum value of stress up

to 506.8 MPa (18%) (peripheral section shifted by

the value of 0.05h towards the suction side) (Figure

7) at forced mode, which corresponds to the factor

load 1.49 (Figure 8), was found. It should be noted

that derived value of the load factor at the forced

mode (n = 28000 rpm) does not exceed the value of

the basic turbine version load factor at nominal

conditions (n = 25500 rpm). The flow in the

modernized turbine was investigated using Ansys

CFX.

Figure 6: Normal stress distribution on the basic blade body at n=28000 rpm (pressure side – on the left; suction side – on

the right).

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Figure 7: The appearance of modernized blade version.

Figure 8: Normal stress distribution on the modernized blade body at n=28000 rpm (pressure side – on the left; suction side

– on the right).

It was found that recommended variant of the

peripheral sections slope at the mode with n = 25500

rpm increases the turbine efficiency by 0.4%

(absolute).Modernization of Blade Attachment and

Blade Number Selection.

Alternative larger typical size of fir-tree root for the

elimination of plastic deformation in blade

attachment’s was selected. This in turn required

reduction the number of blades from 49 to 43 by

allocation on disk conditions.

The effect of rotor blades number on the

efficiency value was carried out in Ansys CFX in

order to evaluate the impact of this decision on the

turbine efficiency. The resulting dependence is

shown in Figure 9. The number of nozzle guide

vanes was not changed.

From the Figure it can be seen that the reduction

of RW blade number increases the turbine efficiency

by more than 1% for all versions of blade body. It is

related to the reduction of skin friction, number of

edged wakes decreasing and relative size of the

secondary vortices reduction. The value of

efficiency begins to drop again if the number of

blades more than 40 due to the reduction of torque

on RW blades.

Noteworthy the fact that blade version with

peripheral sections shift exceeds the base variant in

the gas-dynamic efficiency.

Analysing the diagram in Figure 9 it can be

concluded that the decrease of RW blades number

from initial 49 to 43...41 does not worsens the gas

dynamic turbine efficiency, but also improves it to

0.8...1.0%.

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599

Figure 9: The turbine efficiency from number of RW blades dependence with constant number of NGV blades (dashed line

– basic blade version; solid line – blade with sections removal).

5 CONCLUSIONS

As the result of calculation research it was found

that turbine rotor blade of turbocharger TK-32,

manufactured by LLC "Penzadieselmash", will not

meet the strength conditions in case of engine

forcing up to n = 28000 rpm. The trouble spots of

the design are the blade bode and blade attachment.

In the course of the research it was found that

stress in the blade can be significantly reduced

through shifting of the three upper sections on 0,05h

in the circumferential direction towards the suction

side, replacing the blade attachment to another from

industry-specific standard (OST 1.10975-81) with an

opening angle

= 30 °, tooth pitch S = 3.2 mm, as

well as reducing the number of RW blades to 43

units, while maintaining the number of NGV.

The recommended variant of the basic blade

body modernization allows to satisfy the strength

conditions at all modes and to increase turbine

efficiency by 1%.

Turbocharger with number of rotor blades 43

was made and tested. The blade attachment and

blade body form was basic. The experiment showed

an increase in turbine efficiency by 1%, which fully

confirms the conclusions drawn by the authors.

ACKNOWLEDGEMENTS

The authors gratefully acknowledge the

comprehensive support of LLC “Penzadivelmash”

development design office staff, as well as staff of

SSAU department of Structure and Designing of

Engine for Flying Vehicles.

This work was financially supported by the

Ministry of education and science based on the

Government of the Russian Federation Decree of

09.04.2010 № 218 (code theme 2013-218-04-4777)

and in the framework of the implementation of the

Program of increasing the competitiveness of SSAU

among the world’s leading scientific and educational

centers for 2013-2020 years.

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ANSYS - Simulation Driven Product Development

[Online], Available: http://www.ansys.com/ [10 Aug

2011].

Bohn, D., Heuer, T., Kusterer, K. 2005. Conjugate flow

and heat transfer investigation of a turbo charger. In

Journal of Engineering for Gas Turbines and Power,

vol. 127(3), pp. 663-669

Bochkarev, S.K., Dmitriev, A.Ya., Kulagin, V.V.,

Makeenko, S.V., Mosoulin, V.V., Mossoulin, A.A.

1993. Experience and problems of computer aided

thermogasdynamic analysis of testing results for gas-

turbine engines with complex schemes. In Izvestiya

Vysshikh Uchebnykh Zavedenij. Aviatsionnaya

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