Why is flow measurement on engines so complex?
Dynamic and thermal influences on flow measurement in engines
Flow measurement in engines is one of the most challenging tasks in measurement technology. Hardly any other measuring point is influenced as much by changing operating conditions, vibrations, temperature and pressure fluctuations as the engine compartment of a commercial vehicle, be it a lorry or a construction machine. Those who require precise and stable measurements in this environment depend on robust sensor technology and stable solutions for signal evaluation.
1. Uneven gas flow
Flows in the intake or exhaust tract are rarely uniform. Pulsations caused by engine operation, valve openings or turbochargers lead to highly fluctuating volume flows. This dynamic makes it difficult to calculate an exact average value, requiring sensors for gas flow measurement that deliver stable results even under dynamic conditions.
2. Vibrations and mechanical stress
Engine vibrations directly affect the measuring elements. Without suitable damping and signal processing, this can result in noise or inaccurate readings. A solid mechanical design and intelligent signal analysis are therefore crucial.
3. Dirt, condensate and particles
Exhaust gas measurements are often impaired by soot, oil mist or condensate. These deposits can alter flow conditions or block measuring openings. Low-maintenance systems with a self-cleaning effect or an adapted probe shape minimise this influence.
4. Limited installation space and short inlet sections
Space is at a premium in the engine compartment. Flow measurement sensors on the engine often have to be mounted directly after bends, valves or turbochargers, where the flow profile is severely disturbed. In these cases, the correct inflow angle and optimal positioning of the probe are crucial.
Influence of temperature and pressure fluctuations on measurement results
Compensation and density correction of gas flow measurement under variable engine conditions
Hardly any other measurement task is so strongly influenced by thermodynamic changes. When measuring flow at the engine, pressure and temperature fluctuate constantly depending on the load. These changes directly affect the density of the medium and therefore the calculated mass flow.
Systems developed specifically for this purpose compensate for these influences through integrated pressure and temperature measurements, delivering accurate, density-compensated values even under highly fluctuating conditions.
Signal stabilisation and data processing in differential pressure measurement on the engine
A key issue in engine flow measurement is processing the differential pressure signal.
Differential pressure measurement (DP measurement) has proven to be particularly robust and reliable. It enables precise measurements even at high temperatures and with pulsating gas flows, and is also low-maintenance.
To stabilise the signal, modern dp systems use digital filters, moving averages and adaptive algorithms. This ensures that the signal remains evaluable even in the presence of high noise levels and delivers reproducible results.
Conclusion: Precise flow measurement on the engine requires an understanding of the system.
Flow measurement on the engine requires more than just installing a sensor. The influence of pressure and temperature on flow measurement is particularly relevant here. The following factors are crucial for precise measurement results:
- correct positioning in the flow path
- physical compensation for pressure and temperature
- robust signal processing
- a sensor architecture that can withstand vibrations and contamination.
It is only through the interaction of these factors that reliable, dynamically correct measured values can be achieved, both on the test bench and in real driving conditions.