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Fuel cells are probably the most efficient way to achieve the difficult purpose of the so-called zero emission vehicles. In comparison to today's automotive emission monitoring applications, fuel cell emission monitoring meets the greatest challenge. In particular, the formation of hydrogen from liquid fuels produces the most dramatic changes in bulk gas compositions. During startup and in stationary conditions, gas concentrations of H2O, O2, N2, CO2, CO and methanol in the fuel cell may vary from 0 to 60 Vol%, C1 to C4 hydrocarbons from 0 to 5 Vol% [1]. Whichever physical principles and technologies are applied in the gas analyzing equipment, they are subject to more or less interference caused by the bulk gas. A new dilution device consisting of pressure reduction stages and four compression stages with regulated dilution inputs is presented in this paper.

Today's concepts of dynamic emission control in lean operating engines demand rapid monitoring of all relevant molecular components and their concentrations in pre- and post-catalyst exhaust gas. Storage capacities and breakthrough characteristics of catalysts, reaction rates, response times and interference levels in NO sensors are no longer studied in stationary gas distributions; they must be evaluated under transient conditions [1]. A twin chemical ionization mass spectrometer (CIMS) system, enables simultaneous and synchronous monitoring of relevant gaseous components with dynamic capabilities from 0.1 ppm to 5000 ppm and a high time resolution.

Real time individual hydrocarbon tailpipe emission monitoring on a ‘lambda one’ (stoichiometric air/fuel ratio, i.e. λ = 1) controlled vehicle, driven in the ‘Neuer Europäischer Fahrzyklus’ (NEFZ) driving cycle on the chassis dynamometer, showed dramatic variations in the concentrations of butadiene and benzene when operated with gasoline having different octane ratings. Butadiene and benzene emissions were higher in 91 octane (RON) fuels compared to 95 and 98 octane fuels. The aromatics content of RON 91 fuel was significantly lower and the concentration of benzene was equal to the RON 95 fuel. The measured emissions of total hydrocarbons (THC) cannot reflect these differences, whereas cold start behaviors as well as highway driving emissions are derived from the test program.

In the compression and combustion strokes different individual hydrocarbons are generated through a complex reaction chemistry and can be monitored by a rapid V&F multicomponent gas analyzer system. They give detailed information on the physical properties of an engine. Through all different reaction sequences of the combustion, surface quenching reactions leave a characteristic pattern of hydrocarbons in the exhaust gas. Toluene and xylene, for example, represent direct monitors for unburnt fuel, alkenes and alkines show thorough fuel decomposition, allowing a rapid combustion when the spark is ignited, whereas aldehydes indicate autoignition processes. Ratios of hydrocarbon concentrations describe engine parameters like fuel/air mixing properties, EGR characteristics, autoignition processes, and engine oil combustion. So an optimized engine performance can be set by the hydrocarbon pattern measured in the direct exhaust gas.

A new multichannel gas analyzer based on ion - neutral interaction principles is introduced. This gas phase secondary ion mass spectrometer using several well defined energy levels for the ionization process quantitatively analyzes gas mixtures without the use of presetection techniques. A high sensitivity for many compounds together with high cycle rates allows dynamic studies of gaseous emission in the low and sub ppm range. Transient studies of inorganic compounds like NO, NH3, H2S, COS and SO2 in catalytic converter systems and differentiated Hydrocarbon analyses of C1 to C8 prove the versatility of the instrument.