12-12-2012, 12:09 PM
Computer Simulated Engine Performance
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Abstract
This model is a computer simulation which determines the performance of a four stroke internal combustion (IC) engine. The modeling of this process begins with the simulation of one cylinder of the four stroke IC engine which is assumed to have an ideal pressure-volume (p-V) relationship allowing for computation of peak performance. Once the ideal cylinder is modeled, factors which compensate for less than ideal p-V relationships are injected into the simulation to allow for computation of the performance figures across the entire operating range. The single cylinder model is then expanded to simulate the interaction of multiple cylinders at once and compute their combined effect giving total output numbers for the engine as a whole.
Performance figures computed include torque and horsepower curves for an engine’s entire operating range. Additionally, statistics are also available regarding the pressure and torque within a single cylinder as a function of the crank angle at a particular RPM. Finally, the combined efforts of cylinders functioning together and their effect on torque at a particular RPM are presented. This model has been used to simulate the performance of the Audi 1.8 liter I-4, the Subaru 3.0 liter H-6/Boxer, the Ford 347 Stroker, and a theoretical Chevy 350 buildup.
Related Work
Engine Dynamometer
An engine dynamometer is a machine which hooks up directly to an internal combustion engine and can determine the performance figures for that engine, including torque and horsepower. This machine is hooked up to a computer with specialized software designed to extract information from the dynamometer. This machine allows users to determine what the performance of an internal combustion engine is over its full RPM range.
Virtual Engine Dyno
Virtual Engine Dyno is software developed by Challenger Engine Software, LLC for the purpose of allowing its users to virtually build up an engine on their own computer. This allows users to test out different engine setups before they go out and perform the labor of putting new parts on their engine. The software calculates many different engine specifications and performance figures. Basic versions focus on common engine setups while advanced versions allow users to build an engine from the ground up.
Dynamic Analysis of the Internal Combustion Engine
This was a project given to students in MEAM 211, taught by Professor Vijay Kumar, right here at SEAS during the spring of 2005. The goal of the assignment was to have students model a dynamic system of equations, explain what was going in the model and then propose ways of improving the engines they were modeling based on their findings.
Technical Approach
We began by trying to break the four stroke internal combustion (IC) engine down into sub-sections on which we would base our simulation. We ended up breaking the engine down into 3 main sections: the single cylinder, the intake and fuel delivery system and the crankshaft.
Our starting point for modeling the single cylinder and the crankshaft was Dr. Kumar's Dynamic Analysis of the Internal Combustion Engine. Dr. Kumar’s MEAM 211 assignment provided the derivation of the equations necessary to model the single cylinder and crankshaft at a constant RPM.
Conclusion
When we started this project, we had only a very basic idea of how a four stroke internal combustion engine works. By the end, we had created a model which gave us great insight into how and why engines perform the way they do.
We started with a model that was only suitable for engines operating under ideal conditions. This meant we could only model the engine as it worked at peak RPMs. This led us in to an even more careful study of our original model and how real engines.