Exhaust Gas Flow Metering on the Engine Test Bed

deltaflowB - our exhaust gas flow meter

Precise reference flow measurement by a precise exhaust gas flow meter is one of the most important variables for exhaust gas and efficiency optimisation in modern engines. It plays a central role in exhaust gas flow and volume measurement on the engine test bed. Modern environmental regulations such as Euro 6, Euro 7, Tier II, Tier III, CN4 and CN5 need complex engine optimizations to be fulfilled.

The requirements for gas flow measurement on the engine dynamometer beds are particularly high. As a calibration standard, the measurement must not only be accurate, but also have a high dynamic response (measurement rate) and, depending on the application, withstand massive pulsation, contamination, soot and fowling and temperature. Their importance in modern test environments is immense. Gas mass flow measurement of fresh air, blow-by and exhaust gas is one of the most demanding measurement tasks, as it has to meet a large number of specific requirements:

  • Fast measurement dynamics
  • Large measurement ranges
  • Pressure and flow pulsations resistance
  • Lowest possible pressure drop
  • High accuracy
  • CAN bus integration
Abgasmengenmessung am Motorprüfstand / exhaust gas flow meter
exhaust gas flow meter deltaflowB
deltaflowB for EGR and Blow-by

deltaflowB, our exhaust gas flow meter, is based on the principle of differential pressure measurement, which offers significant advantages over other measurement methods:

  • Insensitive to fouling and contamination, easy cleaning if necessary
  • Wide temperature and pressure range
  • High accuracy
  • Low long term drift
  • Easy to recalibrate

We have developed the deltaflowB as an exhaust gas flow meter specifically for various gas volume flow measurement on the engine test bed and as a master for the flow meter test bed, where it has become an integral part of the engine test bed equipment. It offers many advantages over standard differential pressure measurement:

Primary element:

The deltaflowB does not use classical primary elements (such as orifice, venturi, nozzle), but a newly developed combination of a low pressure loss venturi and an airfoil probe. This combination reduces the permanent pressure drop to well below 10% of the measured differential pressure, which means that even at maximum flow rates the pressure drop remains <20 mbar.

Sensorics:

Commercially available pressure, differential pressure and temperature sensors are too slow for the dynamic requirements of exhaust gas volume measurement on the engine dynamometer and flow measurement on the test bench. One of the main problems, in addition to the slow transmission of measured values to the test bench, is that engine pulsations cannot be detected by standard sensors. This leads to measurement errors that depend on the strength and frequency of the pulsation (square root error).

The CAN-based sensors from systec Automotive measure up to 2kHz and use sophisticated filter strategies to separate pressure and flow pulsations and calculate precise air mass flows.

Redundant digital analysing electronics:

The exhaust gas flow meter deltaflowB is equipped with triple sensor recording, which gives you several advantages:

  • Plausibility check of the 3 x 3 readings (p, dp, T)
  • Automatic maintenance and recalibration recommendations
  • High accuracy thanks to averaging

As the sensor readings are taken at different points in the venturi, the user also receives information about the flow conditions at the meter. For example, highly disturbed inlet conditions will result in deviations between the three sensors.

Measurement calculator:

The sensors are analysed and displayed on the PC measuring computer via CAN. The user-friendly software displays both: Individual measured values and filtered averages. The measurement PC and operator terminal are designed as a 19″ rack version. Connection to the test bench is via the PC’s second CAN interface as standard, with additional analogue outputs available via optional I/O cards.exhaust 

Our Exhaust Gas Flow Meter on the Engine Test Bed:

Benefits at a Glance

Thanks to its Venturi design, the deltaflowB has low inlet requirements. It is supplied with an inlet section of approximately 10D, which can be connected upstream as required.

Its high measurement dynamics enable accurate readings even with pulsations, without the need for dampers, known as volumes, between the engine and the measurement. It is therefore an advanced solution for both exhaust gas volume measurement on the engine dynamometer and flow measurement on the test bench, and offers a robust, efficient alternative to thermal flow meters.

Finally, thermal flowmeters need to be recalibrated up to four times a year, depending on accuracy requirements. This is not necessary with deltaflowB. The intelligent evaluation of the deltaflowB compares the redundant sensors and automatically recommends recalibration, usually every two years.

Specification
Fluids Air, Exhaust, Blow-By
Process 0..4,5bar abs
-40..200°C
Dimensions Starts from DN25 (0..160kg/h) up to DN200 (0..12.800kg/h)
(others on request)
FlowSpan Up to 1:28 (qmin/qmax)
Accuracy Standard: 1%
Pro: 0,5%
Flow Computer CAN-based, Mess-PC 19″, 3HE Display/Keypad: 19″, Slider,1HE

Rather interested in a portable emission measurement system (PEMS)? See the case story about our mini PEMS used by the KBA.

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