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Advanced Energy Vehicle Lab 07: System Analysis 3 (Wind Tunnel Testing) AEV Project Objective (Problem Definition) INITIAL CONCEPTS (Brainstorming) EXPERIMENTAL RESEARCH (Programming) (System Analysis) ANALYZE COMPARE PT 1 PT 2 PT 3 PT 4 RESEARCH FINAL DESIGN Present AEV Design DESIGN DECISION Lab Objectives/Goals The objectives of this lab are: • Become familiar with propulsion system efficiency ( sys ) • Become familiar with wind tunnel testing equipment How to relate AEV to real-life objects How to link wind tunnel testing to the AEV Piaggio Avanti! Fun Fact: The P.180 Piaggio Avanti’s wings, canard and propeller were designed and tested at The Ohio State University helping make this plane one of the world’s most efficiency propeller driven planes in the world! These tests were similar to the ones that will be conducted in today’s lab! Recap – System Analysis 1 & 2 System Analysis 1: • Time • Current • Voltage • Input Power • Incremental Energy • Total Energy System Analysis 2: • Distance & Position • Velocity • Kinetic Energy • Propeller RPM • The Advance Ratio • Propulsion Efficiency System Analysis 3 The propulsion characteristics can vary from vehicle to vehicle from the difference between the motors and the type of propellers used: This lab will demonstrate how to measure propulsion efficiency from taking a closer look at: • How to measure propeller RPM • Computing the advance ratio (𝐽) • How to measure the propulsion system efficiency ( sys ) Propulsion Efficiency In system analysis 2 the propulsion efficiency was defined as a function (𝑓) of the AEVs velocity (𝑣) and the propeller speed (𝑅𝑃𝑀) which we simplified into one input, the advance ratio: sys f (v, RPM ) f ( J ) Let’s take a step back and redefine the propulsion efficiency as the ratio of the power output and the power input. sys Pout *100 (%) Pin Propulsion Efficiency Input power (𝑷𝒊𝒏 ) Power supplied to the vehicle’s propulsion system. (𝑃𝑖𝑛 = 𝑉 ∗ 𝐼) Input Power is an Electrical System (units are Watts). Output (available) power (𝑷𝒐𝒖𝒕 ) Power generated by the electric motors and propellers. Output Power is a Mechanical System. An example of a typical unit for power in a mechanical system is horsepower. Propulsion Efficiency For a propeller driven vehicle, the output power is the thrust (𝑇, force created by the propeller & motor combination) multiplied by the vehicle velocity (𝑣). Pout T * v Wind tunnel testing can be used to measure these two parameters. • This is a common testing procedure used in mechanical & aerospace engineering for testing the propulsion power & efficiency of aircraft engines. Wind Tunnel Testing Air drawn through Duct Simulating Thrust Direction Configuration Selection Thrust Line Puller (Tractor) Configuration Thrust Line Pusher Configuration Proper Propeller Orientation Visual confirmation of propeller orientation Counter-clockwise rotation Propeller number designation For either Puller or Pusher Configuration - When looking at the propeller (i.e. AEV) from the front: • The propeller number designation should be visible • The propeller should be rotating counter-clockwise System Analysis 3 Summary 1). Perform wind tunnel testing: • We’ll vary the motor speed from 60% power to 0% in 5% increments and record the following parameters: Voltage supplied to the motor controller Current supplied to the motor controller RPM measured by RPM sensor Thrust (in grams) measured by the wind tunnel scale. Remember, thrust is a force (i.e., Force = mass*acceleration). We’ll need to keep this in mind when analyzing the wind tunnel data. System Analysis 3 Summary 2). Analyze wind tunnel results by calculating the following: • Input Power (𝑃𝑖𝑛 = 𝑉 ∗ 𝐼) • Output Power (𝑃𝑜𝑢𝑡 = 𝑇 ∗ 𝑣) • Propulsion System Efficiency • The Advance Ratio 𝐽 = 𝜂𝑠𝑦𝑠 = 𝑣 𝑅𝑃𝑀 ∗𝐷 60 𝑃𝑜𝑢𝑡 𝑃𝑖𝑛 ∗100 System Analysis 3 Summary 3). How does this relate to the AEV? How does voltage affect the propulsion efficiency? 𝐽= 𝑉 𝑅𝑃𝑀 ∗𝐷 60 RPM is directly proportional to voltage Increasing Voltage How does this relate to AEV? Looking at a plot of Propulsion Efficiency vs Advance Ratio Where is the 2 volts A or B? • 2 volts divided by a 7.4 volt battery is approximately equivalent to 27% MotorSpeed B A Questions to consider . . . Things to think about during the Lab: • What is the advance ratio needed to obtain the highest efficiency and how does that relate to power needed? • Do all propellers have the same performance for all voltages/configurations? Questions?