Engine Exhaust Test Equipment

At Altamira Instruments we are constantly encountering requests for reaction units and characterization equipment that are useful for testing real or simulated exhausts of various types of motor vehicle engines, from car gasoline engines to large diesel trucks. Although each is a special case, through many years of experience we have learned how to make units useful for specific tests and thus provide reliable test equipment to our customers.

The type of equipment needed to characterize and evaluate catalytic converters requires the utilization of an actual catalyst sample (i.e., not a crushed sample) and the simulation of actual conditions occurring in the exhaust gases. Some of these conditions are:

•    Very high flow rates.
•    Rapid temperature changes in the orders of hundreds of degrees during operation.
•    Complex mixtures of varying compositions, including hydrocarbon fuel, unspent hydrocarbons, NOx, carbon oxides, etc.
•    Rapidly varying changes in gas composition, from a very “rich” fuel mixture to a very “lean” fuel mixture in only fractions of a second.

In addition, testing for diesel exhaust may also include:

•    Particulate (soot) production and burn-off.
•    Simulation of Selective Catalytic Reduction (SCR).

Altamira Instruments has extensive experience in the design, construction, and commissioning of both characterization units and BenchCAT reactor units that meet all these requirements.

Very high flow rates are typically encountered in engine exhaust. In designing a test unit to model such reactions it is important to achieve the high flow rates while maintaining temperature control of the catalyst. For a two-inch monolith, flow rates in the order of 200 SLPM (7 ft³/min) are typical.

Figure 1 shows a simplified diagram for a test unit handling high flow rates and rapid temperature changes. Inert gases, such as nitrogen, argon or CO, and vaporized water flow from a common line at high flow rates. They first encounter a preheater where the temperature is brought up to 100-200°C, followed by two in-line process heaters in series which allow the flow to be heated up to 800-900°C.  The reactive gases are
added at lower flow rates just upstream of the reactor. The reactor is housed within a multi- zoned furnace to prevent heat losses. Using this arrangement it is possible to not only achieve high temperatures at high flow rates but also to simulate the large changes in temperature that can be experienced in a catalytic converter. Table 1 shows some typical controlled temperature changes we can achieve in our test units.
 

Analysis of products in real time is critical in evaluating emissions catalysts. Altamira Instruments can integrate virtually any kind of analytical instrumentation to our BenchCAT systems. Some examples of our experience include integrating the following:
•    Mass spectrometers from various manufacturers
•    Gas chromatograph-mass spectrometer (GC-MS)
•    Oxygen sensors
•    Lambda sensors for air:fuel ratio
•    Fuji Instrumentation ZRE NDIR-type infrared analyzer capable of measuring the concentration of NOx, SO鈧? CO, CO鈧? CH鈧?and O鈧?components in           sample gas
•    California Analytical Instruments (CAI) 600 Chemiluminescence analyzer for NO/NOx
•    CAI 301 FID analyzer for total hydrocarbons
•    Fourier Transform Infrared Spectrometers (FTIR)
•    CAI 602P oxygen analyzer with Pump-Pak for sampling