Mechanical Engineering

Technology FOCUS

INSTRUMENTATION AND CONTROL

Quick Octane Measurement

TO MEASURE THE OCTANE of gasoline at the pump, depot, and blender, Zeltex Inc. in Hagerstown, Md., designed the ZX101C portable octane analyzer. Octane numbers represent the antiknock properties of the fuel, which are specified to meet engine-performance requirements and environmental regulations.

Zeltex's analyzer, which matches the standards of reproducibility and repeatability established by ASTM, is equipped with diodes that emit infrared light into a gasoline sample held in a clear 8-ounce glass jar. A special dark label ensures that the light is diffracted from the gasoline, not the jar. The analyzer's built in microprocessor controls the rapid switching on and off of the diodes and processes the data.

A source-array, solid state optical system consisting of fixed narrow-band-pass filters is mounted in front of the diodes. This system detects a spectrum of near-infrared energy from 900 to 1,050 nanometers, which the microprocessor uses to determine the octane number of the fuel in seconds instead of minutes or even hours other ASTM analytical methods require. Another benefit of the optical system's design is that it eliminates the use of failure-prone moving optical parts and light bulbs.

The analyzer provides the research, motor, and pump octane numbers simultaneously to determine whether the pump being tested is dispensing gasoline with the correct octane rating. The instrument also has additional memory-storage capacity for nine calibrations such as ethanol-blended fuel and acrylates. The instrument can also be used to screen diesel fuel to ascertain if further testing needs to be performed.

Government inspectors in 14 states use the Zeltex portable octane analyzer, as do their counterparts in Argentina, Brazil, China, Japan, and Russia. Although typically used in the field, the analyzer can be adapted to laboratory service by means of its RS232 port and calibration software.

Michael Valenti