Transcript Design and Fabrication of a Miniature Turbine for Power

Design and Fabrication of a Miniature
Turbine for Power Generation on
Micro Air Vehicles
Team 02008
Arman Altincatal
Carl Crawford
Rob Latour
Srujan Behuria
Dan Holt
Overview
• Project Motivation and Goals
• Concept Development / Feasibility
Assessment
• Project Objectives and Specifications
• Analysis
• Future Plans
Current Problem
• The weight of batteries is prohibitive
for Micro Air Vehicles (MAVs)
• Current Batteries
Black Widow by Aerovironment
– More than 50% of the weight of vehicle
– Less instrumentation can be attached to
MAV
MicroTurbines: a Possible Alternative
• Much greater power to weight ratio
• Microturbines are being developed at
a number of schools
MIT’s Micro Turbine Impeller
Project Scope
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Proof of Concept
10 mm impeller
Spins at 50,000 rpm
Powered by compressed nitrogen (air)
Produces 5-15 watts of electrical power
Can be scaled down to MEMS size
Distribution of Work
Concept Development and
Feasibility
• Used Brainstorming Methods to Generate Ideas
• After voting, 4 concepts remained:
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Multiple Jets
Control Scheme
Air to Cool Generator
Light Weight Materials
• Rated the concept feasibility based on technical,
economic, market, schedule, and performance
factors
Multiple-Jet Concept
• Multiple inlets to increase the
torque
• Total mass-flow must increase
• Rotational balance must be
achieved
• The feasibility of the design is
above baseline model (single
jet)
• The concept is approved by the
design team and will be
implemented
Control System Concept Development
• Terminal Characteristics of a DC
Generator
• Loading the Generator
• Effect of Reduced Shaft Speed
• Constant Generated Voltage
Desired
• Achieving Generator Shaft Speed
Control
– Variable Solenoid
– Variable Nozzle
• Control Scheme Feasibility
– Above Baseline Aspects
– Below Baseline Aspects
• Feasibility Assessment Results
T1
3
P4
T2
2
P3
E1
1
P2
0
E2
P1
M1
S2
M2
S1
Exhaust Air Used to Cool Generator
• Cooling Generator
– Higher Speeds
– More Power
• Heat Sink
• Friction in Turbine
– Reduces Cooling
Efficiency
• Concept compares well
with baseline in most
aspects of feasibility
• Deferred Decision
Light Weight Materials
• Use of light materials
– MAV’s
• Strength, Cost,
Manufacturability
• Many options available
– Steel, Silicon Carbide,
Plastics
– Aluminum (Best option)
• Team will pursue light
weight materials based on
feasibility assessment
Design Objectives and Specifications
Objectives
Specifications
• Electrical Power
• Production of torque
• Generator should run for at
least 15 minutes
• Generator should be reusable
• Design for MAV’S
• 5 watts
• Minimum torque should be
.021 oz-in
• Blades should spin at
minimum of 50,000 rpm
• Generator Temp. should be
less than 125°C
Performance Specifications
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Produce at least 5 watts of electrical power
Blades should spin at minimum of 50,000 rpm
Generator Temp. should be less than 125°C
Minimum torque should be .021 oz-in
Flow Passages
• Two jet design
• Air fitting mounted axially to
turbine
• Identical Passages
– Length, Turns
– Inlet Conditions
• Head loss calculations
– Major, Minor
– 7.89% pressure loss (Pinlet =100psi)
• Assumptions
– Air is an ideal gas
– Fully developed, turbulent flow
Nozzle Analysis
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Uncontoured converging nozzle design
Nozzle machined into the casing plate
Inlet - 1.58 mm X 1.25 mm
Outlet - 0.7 mm X 1.25 mm
Control volume analysis done for various inlet temperatures and
pressures
• For Pinlet = 100 psi and Tinlet = 275 K
– Mass flow = 0.0048 kg/s
– Reaction force = 0.258 lbf
• Assumptions
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Steady State
Ideal Gas
Isentropic
Choked Flow
Computational Fluid Dynamics
• Pre-Processing
- Geometry
- Mesh
• Post-Processing
- 2D and 3D Flow Solver
- Model Solution
• Equations used to solve the model:
- Conservation of Mass
- Conservation of Energy
- Transport Equations (Navier Stokes)
Iterative Steps to Optimize Geometry
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CFD Analysis of Miniature Air Turbine
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Flow performance
- Moving Reference Frame (MRF)
- Geometry modifications
Torque due to forces on the blades
Validate CFD with experimental results
Dynamic Pressure Contours (Pa)
- Limited references available in this area
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Designing a tool to optimize future
models
Static Pressure Contours (Pa)
Generation
• Electrical Scope of Miniature Turbine Project
• Generator Selection
• Synchronous Generator
• Separately Excited DC Generator
• Shunt Generator
• Series Generator
• Permanent Magnet DC Motor (PMDC)
Brushed PMDC Motor
• Voltage Regulation
Faulhaber Miniature Drive Systems
Brushless PMDC Motor
Structural Design
Posts
Inlet
Face Plate
Turbine
Casing
Generator
Casing
Bolts
Coupling
Future Plans
• Fabrication
• Dental Turbine
• Experimentation to Validate Objectives and
Specifications
– Torque, RPM, Exit Temp., Power
– Efficiency