Understanding precisely what's happening in the combustion chamber

Winterthur, June 2019 – How can combustion engines be optimized to cut fuel consumption and emissions even further? The new measuring spark plug from Kistler combines cylinder pressure measurement and visualization of the combustion process in one compact, rugged product – an efficient tool for developers to carry out in-depth analyses.

Kistler is offering its customers a product that is truly unique: the new series of measuring spark plugs. The new devices integrate a high-temperature miniature pressure sensor with a fiber-optic system for up to eight probes: this allows comprehensive characterization and visualization of the entire combustion process, starting with ignition. Investigations of knocking behavior and recording of other undesirable effects such as soot formation and pre-ignition are now possible with even greater accuracy and efficiency.

The aperture angles and viewing directions of the eight optical probes can be freely adjusted according to customers' requirements.
The aperture angles and viewing directions of the eight optical probes can be freely adjusted according to customers' requirements.

Accurate measurements of processes in the combustion chamber

The optical probes capture the radiation given off by combustion in the combustion chamber as light intensity, which an amplifier then converts into a voltage signal. Thanks to the high sensitivity of the fiber-optic system, processes can be mapped during idling and cold starting, or also directly after ignition. Clear visualization of the defined parameters gives users a deeper understanding of the processes in the combustion chamber – the basis for optimizing many settings, e.g. for injection systems and ignition timing.

The world's smallest piezoelectric cylinder pressure sensor

Because the ultra-compact high-temperature pressure sensor is integrated in the spark plug, there is no need for additional bore holes in the cylinder head. The transducer is mounted almost flush with the combustion chamber, and its natural acoustic frequency of about 65 kHz also makes it suitable for indication at high speeds and for investigations of knocking. It features a pressure range from 0 to 200 bar and an operating temperature range from –20 to 350°C.

An integrated solution that delivers efficiency gains in development

The combination of pressure and light measurement technology in one integrated product cuts costs and saves time in engine development – and it also supplies a holistic picture of processes in the combustion chamber. Key features and benefits at a glance:

  • Combination of cylinder pressure measurement and optical combustion analysis
  • Integrated, compact and rugged design with no extra measuring bore hole
  • Eight optical windows onto the combustion chamber (radial and/or axial observation directions)
  • Integrated miniature cylinder pressure sensor (3 mm)
  • Various thread sizes, heat values, spark positions and electrode spacings are possible

The solution is completed by an amplifier for the fiber optics, a piezoelectric amplifier for the cylinder pressure measurement, and a combined data acquisition and evaluation system. Kistler offers its customers the entire measuring chain from one single source.

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