Internal Combustion Engine (ICE) Valve Train Modeling using Virtual Test Bed (VTB)
Virtual Test Bed (VTB) is a real-time simulation
environment that runs mathematical models. A new camless engine is being
designed by the Advanced Actuators Research Group. To understand how the engine
currently responds while the engine is running a mathematical model was written
and then executed in VTB that showed valve train component position, velocity,
and acceleration. Figure 1 shows a schematic of the valve train that was
Figure 1. Overhead-Valve Valve Train
The basis of the mathematical model is a set of equations written in the User Defined Device (UDD) that relates each of the valve train componentsí mass, acceleration, velocity, position, stiffness, and damping constants. UDD is a program related to VTB which generates C++ code so that VTB can understand it. Once the model was written and the model was created the model was ran in VTB using different input parameters. Initially a sine wave was used to simulate the cam profile. However, a cam profile program was also written and created in VTB. Figure 2 is a schematic of the valve train and cam models in VTB.
Figure 2. Valve Train Model Schematic
Simulation tests were run on the model. Visual Extension Engine, a graphical program that accompanies VTB, shows the results of the model. Figure 3 shows the graphical results of the model.
Figure 3. Model Output, Position, Velocity, and Acceleration of Model
The valve train was based on an actual Honda GX31 engine. To get accurate parameters for testing the model, the parts were modeled in ProEngineer. Using ProE allows the user to get the moment of inertia which is then used to compute the stiffness and damping coefficients. Having the correct constants will allow the model to be accurate. Future work includes testing and verifying of the model.