เทคนิคการวัดออกเทนที่ถูกต้อง Proper way to read Octane

การวัดค่าออกเทน (Evaluation of an Octane Analyzer)

zeltex 101xl_1

Evaluation of an Octane Analyzer

THE OCTANE NUMBER associated with a motor fuel is a measure of the performance of that fuel. The number does not correspond to the concentration of any one constituent in the fuel, but rather to the preignition properties of the fuels as compared with standard fuel mixtures. The term "octane number" is derived from the fact that the standard fuels contain isooctane.

The ASTM Standard Procedures for determination of octane numbers require the use of two Waukesha co-operative Fuel Research (CFR) engines (Waukesha Engine Div., Dressier Industries, Inc., Waukesha,WI). The Research Engine runs at 600 rpm, with a controlled air mixture and temperature as defined in ASTM D 2699. The Motor Engine runs at 900 rpm, with a controlled air mixture and temperature and controlled fuel temperature as defined in ASTM D 2700. These engines, or "knock engines," necessarily consume the fuel sample and a series of standard fuels during the test procedure.

The octane number of a fuel is defined by the compression at which the knock intensity of that fuel is 50% of the maximum knock intensity for the engine. Pure isooctane is defined as having an octane number of 100, while heptane is defined as having an octane number of 0. A series of standards containing heptane, isooctane, and toluene are used to define a scale between these two bounds. The research octane number (RON) of a fuel is the octane number measured on the Research Engine. Similarly, the motor octane number (MON) is the number determined by the Motor Engine. The octane number typically posted on the pump at a service station is the average of the RON and MON (called antiknock index [AKI], or [R +M]/2).

In a traditional test, gasoline samples are collected from various filling stations and brought back to the laboratory for testing on CFR engines. The testing is necessarily time consuming and expensive. For this reason, many states have begun using the ZX 101C to perform on-site octane screening. The analyzer makes octane determinations in seconds and eliminates the tremendous expense of CFR testing.

An octane analyzer
The ZX 101C (Zeltex, Inc., Hagerstown, MD) is a portable, battery-powered octane analyzer for use with gasoline. It consists of three primary components: the analyzer, a sample container, and a light shield. The entire package in a carrying case weighs less than 5 kg. The instrument performs an octane number determination in less than I min and does not require the use of standard samples. The measurement is completely nondestructive. The analyzer measures octane number via near-infrared (NIR) transmission spectroscopy. The instrument contains a patented solid-state optical system comprising 14 near-infrared emitting diodes (IREDS) with narrow bandpass filters, a silicon detector system, and a fully integrated microprocessor. Figure 1 shows a schematic representation of the analyzer. The sample holder is a scaled, flat-sided, reusable glass