ICE Version 1.7
ICE is a tool developed by Gordon Cornell to assist designers and developers of model two-stroke engines by allowing them see the predicted effect of changes to the many various aspects of engine. To quote from the manual:
The genesis of ICE (Internal Combustion Engine) dates back to 1998 when Gordon saw a program intended to predict engine performance and decided to create his own tool to assist him with his ongoing model engine developments. The underlying mathematical models were developed from first principles to avoid the errors associated with empirical methods and the program was oriented towards the configurations most frequently encountered in our model size engines. Over time, the program has been enhanced and expanded to increase the properties that can be modelled, and to take advantage of the increased computing power and user-friendliness this makes possible.
It is worth mentioning that the subject of two-stroke simulation has been investigated by several engineers and academics, most notably by Dr Gordon P Blair, of Queens University of Belfast, whose book, Design and Simulation of Two-Stroke Engines, while definitive, is perhaps beyond the reach of the amateur both technically and financially! To give some indication of the size and complexity of a program like ICE, the first edition of Blair's book concluded with 270 pages of source code listings! The second edition is longer without the source code than the first was with it. Blair's books, while of value to engineers, are targeted at larger size two-strokes such as those found in motor cycles, outboard motors and chainsaws, so model engine builders will find much of them inapplicable.
InstallationICE requires a computer running Microsoft Windows™. The manual states that all versions from 95 through Vista are supported and that while it will work adequately on older hardware, for best results, you should have a fast processor and good graphics capability. My tests were conducted on a 3.4GHz Pentium machine running XP Pro, SP3, fitted with 3.5GB of RAM and a screen with 1280x1024 resolution.
The current 1.7 release was developed in Microsoft Visual Basic version 6. The program is delivered on CD ROM and does not include an "autorun" setup, so you will need to either open the disc and doubleclick the setup.exe file, or run this program through the Start|Run dialog. The installer will copy all the required files to your hard drive, but be warned: although the installer appears to give you the option to install to a location other than the preset default of
"C:\Program Files\Ice Version 1.7", you must use the specified location. Otherwise, as I found out, it will be unable to locate its database file. No uninstall file is generated during set-up, but a log file of all the components copied to your hard drive is placed in the target install directory and the installer is smart enough not to overwrite any shared components that may already be on your computer that are more recent than those on the distribution disc.
Once installation is complete, you can launch the program from the group entry created in your Start|Programs list during the install. If all is well, a splash screen will appear briefly, followed by the default, four panel, tiled user interface display. These panels display Engines database, Fuels database, Exhaust parameters, and Test Setup parameters. All four must be open during operation. The View menu contains an option to restore to the default "four open" setup at any time. Other panels that may be opened are:
- Engine Function Tables
- Engine Performance Table
- Engine Timing
- Curve Selector
- Document File Display
- Print Selection
- Curve Fitting Anaylsis
The distribution CD contains a 111 page user manual in Portable Data Format (pdf) that can be opened in your favourite pdf reader for browsing, or printing. The same document in a more interactive format can be viewed as a Windows Help file through the ICE Help menu. This allows topic browsing and is the best format for using the manual. In fact, the first page suggests that if you feel the need to print the manual, it be done a topic at a time from the Help window. Unfortunately, the help window is set to be "always on top" of the ICE window whenever you switch to ICE, so you can't Alt+Tab to toggle between the user interface and the Help. You can however iconize the Help window to get it out of the way without closing it and thus losing your place.
The Help system is divided into five sections, with a complete hyperlinked subsection index. The sections are:
- ICE Program
- Program Theory
- Reference and Lookup Tables
All are well illustrated with screen shots and other diagrams. The ICE Program section explains menu options and the Toolbar buttons. It also explains the all important engine database and the meaning of the values it contains. Version 1.7 contains data on 29 different engines and will contain any additional engine data sets you create. The Tools section describes the use of the Curve Fitter and Exhaust Editor. The Tutorials section explains the use of most of the ICE program functions. While it makes no assumptions about your knowledge of two-stroke engines, it does assume that you have at least some experience with driving a MS Windows program. Today, this is not an unreasonable assumption.
The Program Theory section gives an excellent explanation of the factors that influence engine performance, concluding with a comprehensive summary of the factors that control various engine aspects such as torque, Break Horsepower, thermal and mechanical efficiency, etc. The last section contains numerous reference tables, including the Break Specific Consumption (BSC) and Break Horsepower (BHP) figures derived for 29 popular model engines by Ron Warring, as published over the years in the Aeromodeller.
OperationICE is a complex, sophisticated software system. Just like a CAD package, an ICE user must invest time and effort in learning the interface; you should not expect to get meaningful results just by sitting down and randomly playing with it. Basically, ICE will use the engine settings and test parameters you specify to rotate your engine through a complete 360° two-stroke cycle, calculating pressure and volume at one degree intervals. Some of the test values will have a major effect if changed; others will be rather minor, but you will need to understand them and know where a change in one may produce an observable effect. This is where the provided documentation is not just handy, but absolutely vital! And like triming a model, it's best to change only one thing at a time and observe the result.
Naturally, ICE is going to plot a timing diagram, similar to the Model Engine News on-line timing calculators, but this is only a very small part of the ICE story. The real value comes from being able to view the predicted values of the many pressure and volume related values for various engine speeds throughout a specified range, and plot graphs of performance related properties for the engine configuration, atmospheric conditions and fuel properties.
Once the properties and parameters have been set and values for a "cycle" calculated (a virtually instantaneous process), the graphic display panels allow you to select one of ten categories (the top list in the accompanying screen shot). For each category, the related X and Y axis parameters will appear in the other list boxes. The values for the Y (vertical) axis are actually duplicated so that two curves can be plotted simultaneously, superimposed on each other for the same, common X axis. In most cases, the X axis will be RPM, but depending on the chosen category, it may be crankshaft angle, or cylinder volume. The set of curves most of us would be familiar with are those that show BHP and Torque against RPM. In the screen shot, "Performance" has been chosen as the category, with BHP selected for the left (black) Y axis plot, and Torque (red) for the other. For the color challenged (and statistics say that over 60% of the male population suffers a degree of color blindness), the color assigned to the plot may be changed, as may the X and Y scaling factors.
ImprovementsAs mentioned in the December 2005 issue of MEN, ICE version 1.5 was reviewed in issue 109 of Model Engineers' Workshop" by Malcolm Stride. I recalled that while overall favourable, that review noted some problems. Luckily time and age had allowed me to completely forget what they were, so I could approach ICE v1.7 "fresh" and without prejudice. That done, I revisited the review to see what progress had been made.
The most annoying problems Malcolm encountered in v1.5 centered around the lack of indexing in the on-line help system and the difficulty of locating information in it. I can say without reservation that this is is no longer valid. The new help service is extremely well indexed and navigation is easy. As well as the Table of Contents mentioned earlier, the use of a standard Windows type Help service means you have a index and a search facility. To test this, I entered "BMEP" as the search term. The Help service immediately identified two sections as containing the string: Thermal Efficiency, and Exhaust Pipe Design. Double clicking on a section name in the results panel opens the page with the search term highlighted. I think we can say this problem has been fully addressed.
The second problem outlined in the earlier review was less specific, just saying the "quirks" were observed during operation, but that these were to be expected in a complex and inexpensive product. This is a fair statement. The screen shot here shows Torque and BHP vs RPM graph generated from the standard reed valve ED Fury data, with the test RPM parameter set to a maximum of 15000 in the Test Setup panel. Compare this with the earlier screen shot for the same engine data with a setting of 14000 for maximum RPM. The plot for Torque extends out to 15000, but the X axis does not and neither does the plot for BHP. This appears to be associated with the axis scaling and a simple change to the scaling factor using the spinner buttons beside the X axis properties cured the problem, extending the axis and the BHP curve. If this is the worst we can expect, the program is not in bad shape.
ConclusionsJust as simply buying a CNC mill will not make you an instant machinist, just buying ICE won't make you an engine designer. What it will do is allow you to forecast the most likely effect a modification will have on performance before you cut metal. Despite their apparent simplicity, there is a lot of complex interactions taking place within a two-stroke model engine. Modelling all these realistically is a non-trivial problem. How well Gordon has succeeded is indicated by the results he has achieved with the Super Fury. ICE was used during development, showing that Gordon has, as we say in the software development business, been prepared to eat his own dog food. I encourage you to read that series and learn how an expert uses ICE to assist development and decide if this is something that will help you too.