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Radial Inflow/Mixed Flow Turbine Impeller Design
TURBOdesign Applications
by Industrial Field
- Aerospace
- Automotive
- Refrigeration & Air Conditioning
- Industrial Turbomachinery
- Industrial Fans & Blowers
- Industrial Pumps
- Power Generation
- Marine
by Machine Type
- Axial Turbines
- Axial Compressors
- Centrifugal Compressors
- Radial-Inflow Turbines
- Torque Converters
- Pumps
- Fans & Blowers
- Hydraulic Turbines
- Marine Propellers
Fig.1 Specified loading
Fig.2 Resulting blade shape of Radial inflow turbine
Fig.3 Mixed flow turbines
TURBOdesign-1 can been applied to improve the design of radial and mixed flow turbines. Some examples of improvements achieved with TURBOdesign-1 include:
- Improvement in the total-static efficiency of the impeller
- Control of the secondary flows on the suction surface of the impeller
- Control of the incidence angles at the leading edge
The loading distribution shown in Fig.1 was used for the design of a radial-inflow turbine for Micro gas-turbine applications. The resulting blade geometry is shown in Fig.2. Detailed CFD computations showed that this impeller has less meridional secondary flows on the suction surface and a more uniform exit flow.
The test results indicated a 5 point improvement in efficiency as compared to the conventional design.
TURBOdesign-1 can be applied with ease to the design of all types of mixed flow turbines impellers as well. An example of one such impeller is shown in Fig.3.
References:
Zangeneh, M, 1990 " Three
dimensional design of a high
speed radial-inflow turbine by a novel
design method". Presented
at the 35th ASME/IGTI International Gas Turbine conference, Brussels.
ASME Paper 90-GT-235, pp. 1-8.
» Request a copy of this reference
Watanabe. et.al., 2004, "Optimization of Microturbine Aerodynamics using CFD, Inverse Design and FEM Structural analysis (2nd report: Turbine Aerodynamics)", ASME Paper GT2003-53583.
Radial Inflow Turbines
Barber-Nichols Inc. (BNI) specializes in the engineering, manufacturing, and testing of Radial Inflow Turbines. The radial flow turbine when applied in the proper expansion conditions can achieve extremely high efficiencies, equaling or exceeding that of axial flow turbines. The radial inflow turbine is a robust design that is economical to engineer and produce and can provide years of service.
A
Radial Inflow Turbine infers
that the working fluid passes from the outer diameter of the turbine assembly inward and exits the
turbine rotor at a smaller diameter. The incoming fluid usually passes through a set of nozzles that cause the fluid to swirl and thereby entering the turbine
rotor at the proper
relative velocity. The flow then
continues through the rotor where
it continues to expand and impart energy to the rotor. The fluid then leaves
the rotor near the rotational
centerline. The blade
angles at the rotor exit are designed
to remove exit swirl as the
fluid leaves the machine.
This minimizes the energy
in the exhaust flow thereby
increasing the turbine efficiency.
In some designs the inlet nozzles are replaced with an inlet scroll sized to provide the swirl to the rotor.
The most common application for the radial inflow turbine is the exhaust driven turbocharger used on internal combustion engines. Thousands of these units are used in automobiles, aircraft, and industrial engines, both diesel and gasoline fueled. Other applications include power generation by gas turbines or by expanding organic fluids in a Rankine cycle. Finally, Radial Inflow Turbines are also used in process plants to recover heavy hydrocarbons from gas streams.
Radial Inflow Turbines have very
high efficiencies when applied in the proper operating conditions. Specific
Speed (Ns), a dimensionless parameter,
can be used
to determine whether or not
a Radial Inflow Turbine will fit your application. If the
Ns is between 30 and
N S = RPM (Q) 1/2 / H 3/4
( Where Q = ft 3 /sec & H = Feet of Head Across the Turbine )
The implementation of impulse blades cantilevered on the side of the rotor disk is an alternate Radial Inflow Turbine configuration that is useful at slower specific speeds. This configuration will have a small amount of reaction resulting from the radius change between the inlet and the outlet of the blade row. BNI has utilized this turbine configuration and achieved extremely high performance levels. Thank you for your interest in Barber-Nichols and we hope that we can put our expertise and experience to work for you.
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