Airfoil Testing Facility

The goal of the project is to design a new test apparatus for airfoil analysis. We will create a program that will automate the zero angle of attack (AOA) and provide real time feed back of the lift, drag and moment forces on the airfoil.

=Problem Definition=

Value Proposition
Currently, using the wind tunnel for airfoil testing at the University of Idaho is a tedious process when it comes to set up and testing. The stand that airfoils are mounted on is antiquated, angle of the foil must be adjusted manually, and the accuracy is not as precise as it could be. The HotWings team is creating an airfoil testing apparatus to fix these issues through automation. Using computer software to adjust the angle of attack as well as calculate lift, drag, and moment forces through data collection. Additionally, it will be easy to set up, break down, and store away for later use by one individual.

Background
Prior to our capstone project, the wind tunnel had an antiquated system. The airfoil stand was manually operated and the data acquisition was bulky with low resolution output. The user had to manually change the pitch of the airfoil on the airfoil stand. The setup did not allow for any fractional degree of pitch. This was due to the data acquisition only rounding to whole integers. Below are pictures of the wind tunnel we will be using and the old stand design.

Wind Tunnel



Test Section



The inside area of the plexiglass test section is 18 inches by 18 inches.

Old Testing Equipment



Photo of the whole original airfoil stand.



This knob is used to change the AOA of the airfoil.



Near zero AOA.



Changed AOA.

Old Data Acquisition Display





Deliverables

 * Operate stepper motor at 1/10 degree precision at low to high speeds.
 * Modular stand design. (i.e. stand can have load cells and stepper motor attached, or just stepper motor attached, or nothing attached.)
 * One person should be able to build and install components of stand and attachments.
 * Design and build airfoil with interfacing adapter for stepper motor and airfoil either build into airfoil or separate device.
 * Need to be able to level the airfoil from a program.

Specifications

 * Build an airfoil to NACA airfoil standards ranging from a 9%-21% thickness.
 * Vibrations cannot contaminate load cell readings, walking past load cell/s will impact readings.
 * We need to design a stand that can possibly support multiple load cells. It absolutely has to have a spot for one load cell.
 * The motor must have smooth rotations.
 * The airfoil must fit inside an 18"X18" plexiglas box.
 * The airfoil must be made out of a robust material.

=Design Considerations=

Stand Designs


This is a stand design for a vertically mounted airfoil.



This is a stand design for a horizontally mounted airfoil.

Load Cell Configuration


The load cell is located above the motor and will rotate when the motor rotates. This design desigion weas made in order to obtain load cell reading more directly. During operation, the motor gennerates an abundance of heat and that can disturb the reading of the load cell. One way to design out the heat affecting the data from the load cell was to position the load cell with some distance above the motor.

Airfoil Designs




This is the first prototype of our airfoil using a Markforged 3D printer. There are some errors we need to solve.

1) The break line in the middle of the two parts needs to be resolved. We are learning about different epoxies and gathering data to find which ones are the best for 3D printed onyx.

2) Add info about the lines on the side of the AF

3) When connecting the airfoil pieces, the leading and trailing edges are not offset from the other and need to be perfectly linear.

4) The raw surface finish of the 3D print does not have a smooth finish that is traditional to test airfoils.



The exploded line indicate how the airfoil pieces will be assembled.

GUI Designs


The graphical user interface (GUI) is to be user friendly. We have started with this simple concept to illustrate our vision for the final concept. This GUI allows us to continue to keep in sight of our goals for the project. The GUI will be programmed with all features working and will be able to receive information provided by the load cell. This is important to the 0° Angle of Attack function. We will be working towards having the background code receiving data from the load cell and then translate the information to tell the motor to turn clockwise(CW) or counterclockwise(CCW). Our goal is to have the "Start" button accomplish that entire task.

=Project Learning= When our team was assembled and we knew what our project was, it was very exciting. Air flow is all around us and it is studied all over the globe. From commercial airlines to automobile companies to universities having airflow test facilities. Every application will have different needs and will use different size wind tunnels. We have been charged to create a modular stand for an airfoil inside a relatively small wind tunnel. Our working area section of the wind tunnel is 18" by 18".

One of the initial problems we began to tackle was 3D Modeling of the stand types we were considering and the type of airfoil we should place on it. There are many many ways to mount an airfoil but mainly two ways in which it should be, vertically or horizontally. We went spent time investigating how other universities oriented their airfoils. This allowed us to develop stands that could fit our needs. Literature from the Nation Advisory Committee for Aeronautics (NACA) was used to ensure we were staying within the standards of testing an airfoil. This literature held equations in which we used for the dimensions of the airfoil we made a 3D model of.

Without knowing much about load cells, we knew the Load Cell would be another key component of learning in our project.Most load cells work by using a strain gauge which translates physical movement to a change in resistance. This is a known relationship that can be manipulated by the user to get a force measurement from the load cell through a calibration process. Load cells not only use strain gauges but can also use hydraulic and pneumatic relationships to achieve the same results. Additionally, there are different type of physical layouts such as button, s-beam, single point, and other types for different uses. They can also vary on how many different axis they measure and how accurate these measurements are. Load cells are primarily used where force measurements are required to find the final result. There applications can vary from being used in scales, finding physical properties of materials, and other use cases where a force measurement is needed. For our project, the combination of a bi-axial through hole load cell with a single axis button or pancake load cell seems to be the most fitting at this time. Some obstacles we may run into is space limitations, unnecessary noise from things such as the motor moving the AOA or other vibrations, among other unforeseen issues that may arise as we begin turning this into a real product.

A GUI (Graphical User Interface) is not necessarily a key part of the project, however it can make the user of our final deliverables life easier as a specifically designed GUI can be made to be user friendly. Our team did not know anything about creating a GUI before beginning the project. 2 team members were taking a concurrent class to get started in GUI development and spend hours outside of that class searching through Python's extensive documentation looking for what they thought we needed to create a GUI for our application. The automation of our motor would be the background programming made user friendly by the GUI. In the beginning stages of our project we foresee getting the GUI interface to work with our Data Acquisition system through code will be a major road block to overcome.

=Final Design=



The figure above is the full assembly of the airfoil stand and indicating the direction of the air flow through the test section.



This is a top angled view of the stand to show more details.

=Validation=

This is a link to all the tests that the Airfoil Test Facility Team completed to ensure our structure will perform the way it is intended.



=Team Members=

=Additional Documentation=

Project Schedule




 * Schedule will be updated periodically throughout the project.

Meeting Minutes



Instructor-Client Meeting Minutes



Presentations



Client Interview