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Design and Prototyping of Micro Centrifugal Compressor for Ultra Micro Gas Turbine

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Title: Design and Prototyping of Micro Centrifugal Compressor for Ultra Micro Gas Turbine


1
Design and Prototyping of Micro Centrifugal
Compressor for Ultra Micro Gas Turbine
  • Shimpei MIZUKI, Gaku MINORIKAWA, Hoshio TSUJITA
  • Toshiyuki HIRANO, Ronglei GU
  • Department of Mechanical Engineering, Hosei
    University
  • Yutaka OHTA and Eisuke OUTA
  • Department of Mechanical Engineering, Waseda
    University

2
INTRODUCTION
- Objective
Centrifugal Compressor
Vehicle
Industry
Aviation
Other field
Methodology of design and production
Period of maturity
Developing actively
Unclear
Small compressor used for turbocharger of
automobile engines
Conventional ultra-micro gas turbine for mobile
electrical power source, ultra-micro jet engine
and so on
Ultra-micro gas turbine (UMGT)
gt
gt
Objective
Establishment of the design method of an ultra
micro centrifugal compressor, which is the most
important component of an UMGT system.
  • A 10 times size of the final target compressor
    was designed, prototyped and tested.
  • 5 and 2.5 times models were prototyped by a
    micro stereolithography method.

3
INTRODUCTION
- Content of presentation
4
DESIGN OF UMCC
- Configuration
Design of Ultra-Micro Centrifugal Compressor
(UMCC)
Taking the productivity of the target size into
account, the 2-dimensional shape was chosen.
5
DESIGN OF UMCC
- Reynolds number
6
DESIGN OF UMCC
- Friction loss, Incidence loss
and Leakage loss
7
DESIGN OF UMCC
- Performance prediction and CFD
  • The performance characteristics of the impeller
    are not yet clarified including unsteady
    phenomena such as the surge and the rotating
    stall.
  • Though CFD is the useful tool for the design of
    such impellers, the performance characteristics
    will not be able to be predicted by the present
    methodology.
  • The study on an ultra micro compressor must be
    started from the establishment of the design
    methodology.
  • CFD remains many problems to be solved especially
    in the transition and the unsteady flow region.

8
10TIMES MODEL
- Design
Impeller and Diffuser
Estimation of relation between blockage and
pressure recovery coefficient
9
10TIMES MODEL
- Design of MIT GT
Micro turbine (MIT)
10
10TIMES MODEL
- Prediction by CFD
Computational grids
Rotating speed N200,000
11
10TIMES MODEL
- Prediction by CFD
Velocity vectors on meridional plane at middle of
blade-to-blade channel within impeller
(with Vaneless diffuser)
Inlet
Large separation region
Shroud
Outlet
Hub
12
10TIMES MODEL
- Prediction by CFD
Velocity vectors and Mach number contours on
meridional plane within impeller
( with Vaned diffuser)
Pressure side
Large separation region
Inlet
Shroud
Outlet
Hub
c) Suction side
a) Pressure side
b) Middle
13
10TIMES MODEL
- Prediction by CFD
Mach number contours on blade-to-blade surface
within impeller
( with Vaneless diffuser)
The low efficiency could be estimated by the
complicated flows.
14
10TIMES MODEL
- Prediction by CFD
Velocity vectors and Mach number contours on
blade-to-blade surface within impeller
( with Vaned diffuser)
Inlet
Outlet
b) Hub
a) Shroud
The similar behaviors to those with vaneless
diffuser were seen.
15
10TIMES MODEL
- Prediction by CFD
Velocity vectors and static pressure contours on
blade-to-blade surface within diffuser
Outlet
Inlet
a) Shroud
b) Hub
The flow at the impeller exit showed the strong
influence of the vaned diffuser especially for
the configuration of the leading edge.
16
10TIMES MODEL
- Inverse design
Example of centrifugal impeller designed by
inverse method
Optimization of blade shape of impeller by using
TURBO design-1
It is clear that 3-D shape will be better for the
shape of the blades.
17
10TIMES MODEL
- Performance prediction
Performance characteristics predicted by method
of M.R.Galvas
(Designed parameters at
N220,000rpm) Mass flow rate G0.033kgf/s
Pressure ratio p3 Relative velocity ratio
0.68
  • The results strongly depend on the value of
    assumed Cf.
  • The values for 3-D compressor with the bigger
    diameter than that of the present one was used.

It would be difficult to expect the accurate
prediction of the performance characteristics for
the UMCC with the 2-D shape.
18
10TIMES MODEL
- Prototype of compressor
10 Times Model of Ultra-Micro Compressor
(Vaned Diffuser)
(Impeller)
Material aluminum alloy(A7050) Clearance size
0.3mm
(Cross sectional view)
(Casing)
  • The flow rate was measured by an orifice in the
    delivery duct.
  • The rotating speed was measured by a
    photo-electric revolution counter.

19
10TIMES MODEL
- Experimental results
Performance characteristics
The vaned diffuser had narrower operating range
and attained the higher total pressure ratio than
the vaneless diffuser.
The difference was small due to the less pressure
recovery at the diffuser.
It was estimated that the matching between the
impeller and the vaned diffuser was not enough.
The 10 times model had many difficulties to
improve the performance characteristics due to
its 2-D shape.
A 5 times and a 2.5 times model having fully
3-dimensional shape were designed.
20
5 and 2.5 TIMES MODEL
- Configuration
Stress contour and deformation mode due to
centrifugal force (N50,000rpm)
Configuration of 5 times model
5 and 2.5 times models prototyped by
stereolithography
The surface roughness seems to be good for these
small impellers.
21
Conclusions
  • In order to establish the design methodology of
    an ultra-micro compressor, a 10 times size model
    was designed and tested.
  • Only the preliminary results were reported in
    this report.
  • As the combustion test rig will be prepared
    soon, the experiments aimed higher efficiency and
    wider operation range for a 3-dimensional
    impeller will be made at 220,000rpm.
  • Parallel to this 10 times impeller, the
    manufacturing of 5 and 2.5 times aluminum
    impellers with 3-dimentional configurations will
    be tried.
  • However, the rotational speed of these impellers
    will become 2 and 4 times of that of 10 times
    impeller, the air bearing will become the key
    technology for these ultra micro impellers.

22
DESIGN OF UMCC
- Configuration
Proceedings of the International Gas Turbine
Congress 2003 Tokyo November 2-7,2003 (IGTC2003To
kyo OS-103)
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