Abstract
Procedures, which are for long time standardized and certified, exist in the field of the exhaust gas measuring. The examinations have to be carried out due to the expensive equipment on stationary test beds. The possibility of the continuous measuring of the exhaust gas mass emissions of a vehicle during the real drive on the road opens therefore many new possible applications. Since there are hardly measurements about the emissions of harmful substances and the real fuel consumption with different vehicles, traffic situation and drivers, such a system can contribute to the acquirement of base data. Important trial technical information can just be won in the context of the development of vehicles and exhaust emission control system by the combination of different readings like exhaust gas emissions, values of the engine and speed. It was the aim of the work to develop measuring facilities which analyses an undiluted partial flow of the exhaust gas and calculates, stores and represents, charged mass related emissions in real time with a satisfying timing resolution. This method of the exhaust gas emission measuring represents therefore an important addition to the conventional stationary test bed measuring technique. The choice of the measurement procedure and the system components was carried out under the conditions minimal costs, minimal measurements and weight renunciation of operation gasses, good measuring precision and timing resolution as well as application in arbitrary vehicle categories. On the basis of a compact infrared analysis device for the exhaust components CO2, CO, NO and (HC)6, an high-speed on-board measuring system has been developed. The device determines the mass quantity of regulated exhaust emissions from gasoline, LPG and diesel vehicles. By measuring the concentration in the exhaust tail pipe, the air mass flow and the velocity of the car, the mass emissions in [g/km] or [g/h] will be calculated. The whole equipment including a laptop and the DC/AC-converter weights approx. 15 kg and can be easily installed in most vehicles. The results of the mass emissions are displayed in real time on the notebook screen and logged in usual data formats.
The measurement principles as well as the development of the equipment are described. Special regard was put on a short response time and comparable transfer functions of all measurement channels. Additionally a calculation model was developed, to calculate the mass-emissions in real time. The results of comprehensive crosschecks with CVSequipments at chassis dynamometers for cars and heavy-duty vehicles will be presented. The influence of car body accelerations and vibrations on the measurement results was determined.
The examinations and measurings carried out, showed that the target, to develop an as simple as possible and nevertheless correct measuring system showed themselves, has turned out well. The mounting into the test vehicles of different size was feasible with acceptable effort. Engines, which didnt have any air mass sensor, must be equipped with a suitable one. The necessary information for the speed measuring was delivered from on-board electronics. With this development the size and the costs for a mass related on-board exhaust gas measuring system with high time resolution could be reduced considerably. Both in use at the roll test bed and in mobile use the system proved itself within its scope of work. The results on the chassis dynamometer with CVS-system showed a good agreement and it became obvious that direct measuring of the exhaust gas volume flow is not essential.
The on-board exhaust gas measuring offers an interesting perspective for the development and application work as well as for exact exhaust measurings under real-life conditions.