Blog for newenergydirection.com

I created Stirling engine software (a design program) that will help designers and enthusiasts build high-power Stirling engines. The design program helps you design the various components of a Stirling engine for maximum power and efficiency. It’s practical and straightforward to use, and laid out in a format understandable to a layperson; meaning you don’t have to be an expert to use it. In addition, there’s a manual included that gives an in-depth description of Stirling engines. Every effort has been made to make the information as clear and accessible as possible. There is no confusing jargon or obscuring of detail. I created this program and manual with clarity in mind because I wanted to help bridge the knowledge gap between those who understand Stirling engines and those who don’t. There’s a lot of quality information out there, which unfortunately is scattered and hard to understand by the average person. So over the last year and a half I addressed this. I read all the information I could get my hands on. I also went through some serious design efforts of my own in order to gain a practical understanding of these engines. The end result is a practical information manual and design program.

What was my motivation for creating Stirling engine design software? It’s simple. I wanted to create something affordable and of value to someone who wants to design and build a high-power Stirling engine. Never mind all those cute little models you see on YouTube, which anyone can build. I wanted to put together a guide for building an engine that will put out serious power! That said, I did not create a fabrication manual that tells you how to machine the different parts, or how to join different metals together. Furthermore, I did not create a guide that tells you how big to make the linkages and crankshaft so that they can support the piston forces. However, what the program will do is give you the information you need to figure these things out, based on the dimensions and type of materials you are using in your design. For instance, the program will give you information such as pressure, temperature and speed, which you can use to calculate how strong to make the components. The program might also tell you why that engine you once built isn’t running. For example, the (DIY Stirling engine) I made last summer would not run, and I wasn’t really sure why at the time. So I entered the dimensions and other parameters of the engine into the program and found that it was capable of only 5-10 Watts of power, with a top speed of maybe 60 rpm. No wonder it wouldn’t run! It couldn’t overcome the frictional losses in the system. To get it to run I needed a much higher engine pressure and many more tubes for the heater and cooler.

Needless to say I am passionate about Stirling engines and want them to succeed. They are impressive machines deserving of serious attention. And this is especially true now given that demand for alternative energy sources is growing faster than ever.

This is what the Stirling engine design software does:

• Allows you to optimize the number of heater and cooler tubes, and regenerator volume for maximum power, given fixed swept volume

• Predicts engine power, torque and approximate pumping (flow) loss at different engine speeds. You can determine the speed at which maximum power occurs

• Gives you performance data at different engine speeds, such as temperature and pressure

• Gives you information to easily calculate the necessary size and mass of the flywheel

• Allows you to determine the necessary engine pressure to reach your desired power level

The manual gives information such as:

• How long to make the heater and cooler tubes relative to their diameter, to ensure sufficient heat transfer

• The size and range of porosity of the regenerator for optimal performance, based on a review of the literature

• The type of matrix material to use for the regenerator

• The type of seals to use for the pistons and displacers

• How pumping (flow) losses relate to the regenerator and number of tubes in the heater and cooler

• The importance of a pressurized buffer space for reducing the bulk and size of the linkages, crankshaft, and mass of flywheel

• How to design different mechanical drives for Stirling engines including the Ross Yoke and crank drive

• How to minimize thermal losses in the various engine components

• In-depth discussion of the heater, regenerator, and cooler

• Detailed information on the various functions of the program

• Detailed description of the mathematics and physics of the Stirling engine

• Pictures of the MOD II automotive Stirling engine produced in the 1980’s

• Pictures of the current SES engine (a Stirling dish that produces power using concentrated solar energy)

In addition:

• This Stirling engine software program is only for kinematic engines (with prescribed piston/displacer motion). It does not model Free-piston engines

• The program only models alpha engines with two pistons, and beta/gamma engines with a single piston and displacer. The program does not accommodate engine designs with multiple pistons/displacers operating in multiple cylinders (such as the Rinia configuration). This can be done with some extra programming effort, but as of right now this feature is not included.

Below are graphs taken from a sample simulation using the program. Note that the program does not directly create these graphs. The program creates an output file containing all the raw data calculated by the program. You can then copy and paste this data into a spreadsheet like Excel and graph it.

Click on the figures for a larger view.

The program is a simplified third-order model, based on the report by R. D. Banduric and N. C. J. Chen: Nonlinear Analysis of Stirling Engine Thermodynamics, Oak Ridge National Laboratory, June 1984.

Comments made by others (as quoted):

“For comparing Your program’s output with Urieli’s QSFM i made a spreadsheet, which shows for the basic values almost same results” — Bernhard, from Germany

Note: QSFM stands for Quasi Steady Flow Model

“after much of questions and working days, I verified with your model-simulator the data shown by Mr. Dochat about a 5 kWe free piston Stirling engine (the report is: “design study of a 15 kW free piston stirling engine – linear alternator for dispersed solar electric power systems”; you can find it searching with Google!).

I can ensure your program permits to obtain the results wrote in the report with absolute precision! That’s right! I hope this can be useful to you and for future improvements of your stirling engine simulator!” — Simone, from Italy

The software program is written in Fortran. It captures all the essential physics in Stirling engines. It is easy to use and usually takes less than a minute to run. The input data is easy to enter. Every input parameter is clearly explained, with diagrams where necessary.

You don’t have to go through an installation procedure or change any settings on your computer, to use the program. You just download it and run it directly on your computer.

The cost of the Stirling engine design software plus manual is $44.95 CAD. It’s available as an instant download via PayPal and PayLoadz. To purchase go to the main page of http://newenergydirection.com. Click on the menu button “Stirling Engine”, and follow the instructions.

This entry was posted on Monday, March 23rd, 2009 at 5:33 pm and is filed under Stirling Engine. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.