Linear Modeling, Simulation and Experimental Verification of a Pressure Regulator for CNG Injection Systems
Dirk Hübner, Harald Ortwig
The number of motor vehicles powered by internal combustion
engines keeps growing despite shrinking oil reserves. As a result,
compressed natural gas (CNG) is gaining currency as an emerging
combustion engine fuel.
To this day, CNG systems – e.g., in passenger cars – are not fully
integrated into the development process as conducted by vehicle or
engine manufacturers. Instead, they are usually "adapted in" at a
downstream stage by small, specialized companies.
The present paper initially outlines the state of the art in advanced
gas injection technologies. Especially the development towards
sequential injection systems is described.
A pressure regulator for CNG driven combustion engines is examined
in detail, given its role as a highly sensitive and critical system
component. Based on a precise theoretical analysis, a linear
model of this pressure regulator is derived and subjected to dynamic
The analytical approach is accompanied by an experimental investigation
of the device. On a test rig developed at the Trier University
of Applied Sciences, the static and dynamic features of the
pressure regulator can be measured with the requisite precision.
The comparison of measured and simulated data yields a validation
of the dynamic simulation model. With the approaches developed
it is now possible for the first time to model, simulate and optimize
single- or multi-stage pressure regulators for CNG driven engines
with less effort and higher accuracy.