Chassis DynamometerCopyright: © RWTH Aachen | TME
With the construction of the new chassis dynamometer exhaust gas test bench for combustion engines, the VKA has a resource at its disposal since July 2003 which represents a noticeable extension in comparison with the previous testing possibilities.
This is necessary, since constantly decreasing vehicle emissions as a reaction to lowest possible threshold values do not only require a lowering of detection limits with respect to the limited contaminants, but also appropriate consideration with respect to construction. In view of certain groups of contaminants, as e.g. hydrocarbons, this not only calls for correspondingly expensive measuring equipment with continuous recording of background emissions, but also for due diligence and planning with respect to the building structure and choice of materials.
Therefore, the building was designed for these requirements from the very beginning in order to keep the drag-in of sources of contaminants as low as possible. The measuring and conditioning rooms have their own supply systems, guaranteeing the appropriate consistency of temperature and humidity. The measuring room itself is designed so there is no air exchange with the ambient air.
Only that quantity of air which is carried off directly via the vehicle exhaust gas system or indirectly via the exhaust gas measuring system must be resupplied subsequently to the room via the air conditioning system. Consistency of temperature is achieved by the fact that the heat exchanger is located directly in the measuring room.
The advantage of this unconventional solution without an inserted air system is that by not using air as an intermediate carrier, a unique temperature control method within the test cell becomes possible which is far below the certification provisions (e. g. +/- 2.8°C in the FTP cold test). These are the performance features of the overall system (figure above) in key words:
- Conditioning range of the roller room: -30….+50°C
- Separate conditioning halls for -7°C (3 veh. conditioning room 1) and normal range (6 veh. conditioning room 2)
- 48” single roller for max. 250 km/h and highest measuring accuracy
- SULEV exhaust gas measurement equipment with 4-line exhaust gas measuring system, CVS system with 4-way Venturi system and particle collector for measurements in conformity with certification requirements
- Detection limits 6…8 ppb for the analysers, shortest response time due to appropriate arrangement
- Fulfilment of all world-wide common test procedures, with freely programmable test cycles
- Constant quality control by cross-comparisons with other sites
In addition, the special exhaust gas measuring equipment and secondary exhaust gas treatment methods which are available in-house extend the operational area.
In summary, with this new chassis dynamometer exhaust gas test stand, a resource has become available which contains an extraordinary and forward-looking combination of properties, for both development and certification purposes.