Welcome to the website for the thermodynamic cycle simulation called cycles. This simulation was created to help ME 438 students at the University of Michigan better understand the workings of Internal Combustion engines. This is done by creating idealized thermodynamic cycles that simulate the processes within an engine. This program can also be used within any class to help illustrate the first and second laws of thermodynamics. Some concepts covered by the simulation are: ideal gases, isentropic processes, combustion, equilibrium, adiabatic flame temperatures and pressures, chemical species and dissociation. Currently, it contains the following idealized cycles:
If you would like to use this program, please contact the author at chris@depcik.com. I have been giving the program away to students and researchers as long as they agree to the following conditions (shareware): The program is not to be distributed to anyone else as I would like to be the main source of the program. This way I can distribute information about the program like updates and bug fixes. Any results (plots/data/etc.) that are generated by the program and used in any publication medium (journal/web/etc) must reference the author of the program and this website. To see a powerpoint presentation of the program in action, please click here.
Unfortunately, I do not have enough time to create a vivid and interactive website for this program as I originally intended. As a result, I have decided to make a simple one-page website similar to my Adiabatic Flame Temperature Program. I think that it is more important to get the information out there regarding this program than to spend the time making things look fantastic on-line. As with my other educational program, I am giving this program away as shareware for use by anyone (please see my note above). I would love it for someone to update the Wikipedia webpages using my program (I have started the Lenoir cycle) and reference this page to help spread the word. Thanks!
To navigate this website, you may either use the following links or just scroll down:
The main computational code within cycles was written using C, while the Graphical User Interface (GUI) was programmed using Visual C++. This was done to allow the main computational code to be ported between different Operating Systems (OS) if needed (or wanted). The GUI allows the student to easily change parameters within the program and, most importantly, post-process the results on the fly. I have written all of the code myself, including the Visual C++ interface which gives me the ability to change the visual features without having to go through a third-person or software company. Inevitably, there will be bugs within the program and by writing everything myself, I can easily fix these bugs and get the students an improved version of the software in a short period of time. Please keep in mind that I work on this simulation outside my normal activities, so it may not reach Microsoft Office quality standards ;) You can submit bugs for the program using this form.
The goal of this program is to: a) Use it to help teach thermodynamic principles; b) Make it easy to install and use; c) Make sure it is relevant for course material by producing the desired results. Typically, in every thermodynamics book there is a chapter or section on thermodynamic cycles and their prevalence in society. These cycles can be used to analyze everything from internal combustion engines to refrigerators to powerplants. It is my intent to make my program relevant for as many cycles as possible and to be used in conjunction with classroom learning to help illustrate fundamental principles. I have started by making cycles relevant for internal combustion engines, however I will be expanding it in the near future to deal with power cycles and refrigeration concepts.
After starting the program and navigating past the copyright screen (please don't abuse the shareware privileges), the main window interface of the simulation appears. I have programmed the simulation as a Multiple Document Interface (MDI) which allows the user to open as many windows as desired. This is a more powerful approach to Windows programming than simple form-based simulations like my Adiabatic Flame Temperature Program (AFTP). The main GUI is pretty simple and not too complicated, eventually I might make it more aesthetically pleasing; however, it really does not need to be. After using the program, if you can think of some suggestions to improve the GUI appearance I would really appreciate it; you can submit your responses in the following feedback form.
There are two ways to provide all of the parameters for the simulation: 1. Use the menus and/or buttons to open the different forms pertaining to the thermodynamic cycles; 2. Use the All Input feature which is reachable through the Input menu (All Input). The All Input feature is the easiest to use and is dynamically updated as you change the properties of the simulation. This window is the bottom one shown on the left when viewing an image of the Main Screen (click the heading above). From this screen you can select the cycle you wish to run, the working fluid and enter all of the pertient properties available. I think it is pretty self explanatory with respect to the All Input feature as how to run the program and the user should be able to navigate the menus/forms without too much difficulty. Instead of writing a dissertation on how to run the program here, I will defer to the powerpoint presentation linked above as a more in-depth usage of the program. Instead, in this section I will dedicate my efforts to the thermodynamic cycles available along with the working fluid properties. This should give you a good understanding about this program and if it is suited for your course or personal needs.
Currently there are four different cycles available in the program useful for describing Internal Combustion engines (click on list headings below for pressure-volume images of the simulation):
While the CV cycle is often used for simulating gasoline engines and the CP cycle is used for diesel engines, a better representation of actual combustion is through the LP cycle by setting the limit pressure to that found in-cylinder in the engine. This is because combustion does not happen instantly at constant-volume or follow a constant-pressure profile, instead it can be thought of as a combination of both events. Often the Carnot Cycle is used to represent the second law efficiency of an engine (the theoretical maximum), however a better approximation for the efficiency limit of an IC engine is to use the CV cycle where all of the energy input goes into raising the temperature and pressure of the working fluid. As a result, the CV cycle produces the most amount of work (work is the integral of the pressure-volume diagram) of the four cycles indicated. It will have an efficiency lower than the Carnot cycle, but it is more realistic as the upper bounds. Since some of the combustion in the CP cycle goes towards expanding the volume, it loses some available work and the efficiency will be lower than the CV cycle. Because the LP cycle is a combination of both cycles, the results for the LP cycle fall between the CV and CP cycles. The Lenoir Cycle describes the Lenoir engine built in 1859 and is thought to be the first internal combustion engine. However, due to the fact that this engine does not use a compression event, its efficiency is lower than the other three cycles. Each cycle has the option of including idealized intake and exhaust events to account for valve timing...
In the program, there are two diffent types of working fluids available for the CV, CP and LP cycles:
Currently, I have only incorporated the ideal gas version of the Lenoir cycle and will add the fuel/air gas mixture version sometime in the future. For an ideal gas with constant specific heats, only two parameters (gas constant and ratio of specific heats) are needed to calculate all of the thermodynamic properties of the mixture. This is a simple way of describing the cycles without adding the complexity of fuel/air combustion. In this case, all of the heat input to the gas is modeled as an external heat addition. The fuel/air version allows the user to select from 30 different fuels to simulate the combustion event...
There are three types of output available in the program:
The Process Parameters windows shows your input parameters from the run, the thermodynamic properties at each state of the cycle, the work and heat transfer that occurs during each process and the performance parameters of the run. This window is based off Wordpad, so you can highlight rows, columns or even the entire window using your cursor and copy (Ctrl+C) and paste (Ctrl+V) directly into Excel or any spreadsheet of your choice. In addition, the window can be saved as a tab-delimited or comma-space-delimited file for easy opening of all of the results in a spreadsheet...
If you are already using a version of cycles and a new version is indicated here (either by version number or date), feel free to download the new version any time you want by using the same link location and password as indicated in my original e-mail. Note: I will be moving cycles to Visual Studio 2005 this year (2007) along with adding E85 (85% ethanol, 15% gasoline) as a fuel, so keep watching this area for the new version.
| Version Number | Date | Description of Changes |
| 1.2.0 | 01/01/07 | Added fuel conversion and combustion efficiency to the capabilities of the program. The combustion
efficiency is computed using the CO, H2 and fuel "exiting" the cylinder at state 4. Added Lenoir Cycle with and without the ideal intake and exhaust events modeled. |
| 1.1.0.1 | 08/08/06 |
Added glycerin (L) as a fuel and made some cosmetic changes. |
| 1.1.0.0 | 07/04/05 | Added thermodynamic datafile common to AFTP |
| 1.0.0.0 | 10/23/04 | Initial version of cycles |
In this section, you will find the frequently asked questions (FAQ) regarding the thermodynamic cycle simulation. This will contain information that will help the user learn about the program and hopefully alleviate any questions. It is important for users to keep in mind that I am the only one currently working on the program; the numerical code, GUI features and website. Please don't anticipate a perfect product with the corresponding website as it takes quite a while to create user friendly GUIs, not to mention creating a useful website.
Unless otherwise expressly stated, all original material of
whatever nature created by Dr. Christopher D. Depcik (chris)
and included in this website and any related pages is licensed under a Creative
Commons License.
Date Created: January 3, 2007
Last Revised:
January 4, 2007
Visitors:
