Abstract. Different sensor concepts for time-resolved cylinder pressure monitoring of
combustion engines are realized and evaluated in this paper. We distinguish a non-intrusive
form of measurement outside the cylinder, performed by means of a force
compression rod from intrusive, real in-cylinder measurement by means of
pressure membrane sensors being exposed to the hot combustion process. The
force compression rod has the shape of a sine wave with thinner zones
equipped with highly sensitive foil strain gauges that experience a
relatively moderate temperature level of 120 ∘C. The sensor rod
delivers a relative pressure value that may be influenced by neighbour
cylinders due to mechanical coupling. For the intrusive sensor type, two
different materials for the membrane-type sensor element were simulated and
tested, one based on the ceramic zirconia and the other based on stainless
steel. Due to the higher thermal conductivity of steel, the element
experiences only 200 ∘C while the zirconia element reaches
300 ∘C. Metallic chromium thin films with high strain sensitivity
(gauge factor of 15) and high-temperature capability were deposited on the
membranes and subsequently structured to a Wheatstone bridge. The pressure
evolution can be measured with both types in full detail, comparable to the
signals of test bench cylinder pressure sensors. For the preferential steel-based sensor type, a reliable laser-welded electrical connection between the
thin films on the membrane and a copper wire was developed. The in-cylinder
pressure sensors were tested both on a diesel test bench and on a gas-fired
engine. On the latter, an endurance test with 20 million cycles was passed.
Reliable cylinder pressure sensors with a minimum of internal components are
thus provided. The signals will be processed inside the sensor housing to
provide analysis and aggregated data, i.e. mass fraction burned (MFB50) and
other parameters as an output to allow for smart combustion control.
Cylinder pressure sensors for smart combustion control
