Engine Combustion Analysis – Engine Pressure Measurement for Research and Development - KISTLER - #29

Text version of the page

www.kistler.com 29 Measuring Thermal shock, which is also called short-term drift, is a measuring error arising periodically within each combustion cycle. It is caused by time-dependent thermal stresses in the sensor diaphragm induced by the heat flux of hot combustion gases, which can reach temperatures of over 2 000 °C for a few milliseconds. The deformation of the diaphragm creates the illusion of a change in pressure. The degree of falsification of the measurement result depends on the sensor, its mounting arrangement and the operating point of the engine. Thus, in a given engine the error depends on the injection/ignition point, speed, load, etc. The magnitude of thermal shock is measured relative to a water-cooled reference pressure sensor whose low temperature error makes it ideal for precision thermodynamic measurements. The thermal shock corresponds to the maximum deviation between the unit under test and the reference sensor. The values relate to measurements in a test engine at 1 500 1/min and at an IMEP of 9 bar. Thermal Shock FEM simulation shows on a highly magnified scale deformation of the diaphragm (left) under the influence of heat flux Short-term drift of miniature sensor measured on Kistler test engine ø15 ø6,35 ø6,35 ø13 Type 6125 M10 x 1 Type 6125 Type 6125 M10 x 1 O-ring O-ring with mounting sleeve with mounting nut direct mounting Mounting Examples Type 6081A... Mounting Examples Type 6125C... Type 6081A30 30 min. 8 4 M5x0,5 ø4,1 ø2