Valve Train Analysis
In this dynamic analysis of the entire valve train, its geometry is analysed at a selected cam rotation speed and predictions made of the dynamic values of lift, velocity, and acceleration of the valve. These values, along with the dynamic values of spring coil lift, compression and stress are graphically displayed on the screen. Depending on the valve train under investigation, further component motions, forces and stresses are also graphically displayed on the screen
The software now models the complete valve train systems (direct acting, finger follower, rocker or pushrod) to accurately simulate all possible occurrences of component separation and bounce.
It is possible to model the valvetrain as being motored, i.e., with no gas pressure forces on the valve as if it were running on a Spintron machine. It is also possible to consider the valvetrain dynamics where the valve can be an exhaust valve or an intake valve under firing conditions - i.e. with the respective gas forces applied.
The coil spring model (which includes parallel, progressive and tapered springs with either round or ovate wire) is very sophisticated in that each coil of each spring is treated as a unique spring/mass/damper system. In addition, coil clash and binding are included in the simulation.
A more complete model of a hydraulic tappet was introduced in January 2008 requiring only the physical dimensions of the tappet and the material properties of the oil supplied to the tappet.
The gas spring model is probably the most advanced simulation yet devised of a pneumatic valve spring. The model incorporates unsteady gas dynamic and thermodynamic theory including heat transfer.
The dynamic valve lift file can be exported to the VALVE DESIGN program for analysis and/or direct export to an engine simulation code such as VIRTUAL ENGINES™ (Optimum Power Technology, Pittsburgh).
Typical examples of the models and their input and output graphics are shown in the following links.
Example
of the theoretical models used in the analyses
Coil
Spring Input Data Screens
Input
graphics for the Direct Acting Follower
Input graphics for the hydraulic tappet in a Pushrod System
Dynamic and Static
animation graphics of the coil springs
Output
graphics of the dynamic analysis of a Direct Acting Follower
Output graphics
of the dynamic analysis of a Pushrod System
Output graphics from
gas spring model
General Output
graphics of the dynamic valve lift, coil lift, compression and stresses
Graph of Dynamic
Lift - with gas forces applied at valve
Downloading
the movie files below may take several minutes due to their size
Animation
of two spring model (3405kb)
Animation
of gas spring model (2178kb)
Animation of a progressive
spring model (1501kb)
Animation of a tapered/conical
spring model (1395kb)
Animations of enhanced
spring design model from SAE 2010 Detroit presentation (11767kb)
©Prof Blair & Associates