Design and Fabrication of a Miniature Turbine for Power Generation on Micro Air Vehicles Team 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 (P inlet =100psi) Assumptions –Air is an ideal gas –Fully developed, turbulent flow

Nozzle Analysis Uncontoured converging nozzle design Nozzle machined into the casing plate Inlet mm X 1.25 mm Outlet mm X 1.25 mm Control volume analysis done for various inlet temperatures and pressures For P inlet = 100 psi and T inlet = 275 K –Mass flow = kg/s –Reaction force = 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 12 34

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 MotorBrushless PMDC Motor

Structural Design Generator Face Plate Inlet Turbine Casing Posts Coupling Casing Bolts

Future Plans Fabrication Dental Turbine Experimentation to Validate Objectives and Specifications –Torque, RPM, Exit Temp., Power –Efficiency