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