design and fabrication of a miniature turbine for power generation on micro air vehicles team 02008...
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Design and Fabrication of a Miniature Turbine for Power Generation on
Micro Air Vehicles
Team 02008
Arman Altincatal Srujan Behuria
Carl Crawford Dan Holt
Rob Latour
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
– 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
Black Widow by Aerovironment
MIT’s Micro Turbine Impeller
Project Scope
• 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:
– 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
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• Electrical Power
• Production of torque
• Generator should run for at least 15 minutes
• Generator should be reusable
• Design for MAV’S
Specifications• 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
• 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
• 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– 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
1 2
3 4
CFD Analysis of Miniature Air Turbine
• Flow performance
- Moving Reference Frame (MRF)
- Geometry modifications
• Torque due to forces on the blades
• Validate CFD with experimental results - Limited references available in this area
• Designing a tool to optimize future models
Static Pressure Contours (Pa)
Dynamic 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)
• Voltage Regulation
Faulhaber Miniature Drive Systems
Brushed PMDC Motor Brushless PMDC Motor
Structural Design
Generator
Face Plate
Inlet
Turbine Casing
Posts
CouplingCasing Bolts
Future Plans
• Fabrication
• Dental Turbine
• Experimentation to Validate Objectives and Specifications– Torque, RPM, Exit Temp., Power– Efficiency