Control behavior of the water cooling of an exhaust gas recirculation system

Miniature flow turbines under extreme operating conditions

Even though the internal combustion engine is on the decline in view of the major changes in the automotive industry towards electromobility, research and development is continuing in the area of exhaust gas purification and efficiency (tightening of emission limits as part of the planned future Euro 7 exhaust gas standard).

Exhaust gas recirculation (EGR), is an important process in the reduction of pollutants in diesel and gasoline engines.

Today’s and future exhaust gas limits require cooled exhaust gas recirculation, which in brief works as follows:

Immediately downstream of the cylinders, i.e. the combustion chamber, the exhaust gases are diverted via the so-called EGR valve and fed back to the intake air. This allows less oxygen to enter the cylinder, which in turn lowers the combustion temperature in the cylinder.

This temperature reduction can reduce the amount of nitrogen oxides NOx by up to 70%, because the higher the temperature, the more nitrogen oxides are produced during fuel combustion.

In addition, for gasoline engines, this can also reduce fuel consumption and carbon dioxide emissions. To lower exhaust gas temperatures even further, EGR coolers are used nowadays, which again significantly reduce nitrogen oxides.

The complex control behavior of the EGR control valves, intake air control flaps and bypass flaps of the exhaust gas flow requires a high degree of accuracy in the control of the cooling water.

The miniature flow turbine from TrigasDM, which was developed specifically for this application and is just 30 mm long, is used here.

The measurement of the coolant mass flow and the coolant temperature takes place directly between the engine block and the EGR cooler.

The signal is digitized immediately after the sensor and sent directly via CAN bus, 0-10 volt, 4-20 mA to the subsequent acquisition software or data logger.

As can be seen in the exploded view, a standard injection-molded plastic part is replaced by the measuring turbine and the EGR cooler is remounted in its original position. This makes it possible to carry out a flow measurement on the EGR cooler despite the small installation space. The data obtained from the measurements is used directly in the further development of EGR control behavior and provides the test engineers with valuable information.

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