Span gases

Exhaust gas temperature measurements are made with a fine-wire R-type thermocouple connected to an Omega model 660 digital readout. Gas samples are extracted using a 6.4-millimeter (0.25-inch) O.D. water-cooled stainless-steel suction probe and then filtered, dried, and analyzed for CO, CO2, O2, UHC, and NOj . Instrumentation includes a Beckman model 864 NDIR CO2 analyzer, Beckman model 867 NDIR CO analyzer, Siemens OXYMAT 5E paramagnetic O2 analyzer, Siemens FIDAMAT 5E-E FID total hydrocarbon analyzer, and a Beckman model 955 Chemiluminescent NO/NOj, analyzer. Certified span gases are used for instrument calibration. PC-based data acquisition is available during experimentation. All of the emissions data reported here were obtained approximately 24 pipe diameters downstream of the fuel injector and represent average exhaust concentrations. 

Span gases, which usually contain a minor component of interest at a known concentration level, permit the analytical device to be calibrated at a value corresponding to that concentration. Fuel gases are used in instruments such as those with flame ionization detectors that require the supply of fuel to be enhanced by certain physical properties of the diluent. A mixture of 40 percent hydrogen in nitrogen or helium is common. 

Series 8 in combination with earlier series was intended to provide data on the effects of total anion concentration. The results are internally consistant with the correlation, having a standard deviation of about 15% around the mean error. However the measured values of PSO2 were about 40% lower than the general correlation. An SO2 analyzer, rather than iodine titration, was used to determine SO2 gas concentration from the saturator. The analyzer was calibrated with dry SO2/N2 span gas. In later experiments it was shown that humid gas gives a lower analyzer response. With constant fraction neutralization increased anionic concentration increases PSO2 because pH decreases faster than effective bisulfite activity. 

Another fairly obvious method that should be used to minimize experimental error is frequent calibration. For example, if an analyzer is used to measure the exhaust gas composition, the analyzer should be calibrated at least daily with a suitable span gas cylinder. It would even be better to calibrate the analyzer more than once a day. For example, it could be calibrated at the beginning of the day, in the middle of the day, and at the end of the day. If these multiple calibrations consistently show negligible drift, then one calibration per day may be justified. 

O2. One reason to specify slightly less than the full scale is that the span gas supplier may be slightly off in their gas blending and normally has some allowable tolerance in the gas composition they supply. For example, if the supplier has a 5% tolerance in the actual blend they supply and the experimenter requests a blend with 5% O2, the actual span gas supplied could be as high as 5.25% O2, which is above the range of the 0-5% scale and therefore could not be used to span that scale. 

The reduction converter efficiency was determined using NO2 span gas with 16.5 ppm. With this span gas, the analyzer read a value of 14.6 ppm, for a conversion efficiency of 88%. This compared very favorably with the 87% conversion efficiency reported in Bussman, Baukal, and Waibel [52] for Mn02. 

Prior to each teshng all of the instruments are calibrated using pure nitrogen to establish the "zero" and an appropriate span gas to set the "gain." Upon testing completion the calibration check is performed to make any appropriate corrections, if necessary. 

In fact the Heath Sharp series is identical in form and origin to the classical progression in ionisation energies for the p-block elements (B to Ne and A1 to Ar). This arises through the strict isomorphism of pn and t2n configurations. It is a remarkable relationship it spans light element atoms vs molecular metal complexes and it spans gas phase spectroscopic data vs equilibrium (electrochemical) measurements in solution. 

Our monitor does not require replacement sensors, calibration span gas, or extra maintenance. 

Spanning, accompHshed using a sample gas containing a known volume concentration of impurity, is performed at levels that are the same order of magnitude as the required detection. The actual span concentration is selected so that the majority of expected measurements fall at or within its value. 

A gas turbine used in aircraft must be capable of handling a wide span of fuel and air flows because the thmst output, or pressure, covers the range from idle to full-powered takeoff. To accommodate this degree of flexibiUty in the combustor, fuel nozzles are usually designed with two streams (primary and secondary flow) or with alternate tows of nozzles that turn on only when secondary flow (or full thmst power) is needed. It is more difficult to vary the air streams to match the different fuel flows and, as a consequence, a combustor optimized for cmise conditions (most of the aircraft s operation) operates less efficiently at idle and full thmst. 

The analytical range is determined by the instrumental design. For this method, a portion of the analytical range is selected by choosing the span of the monitoring system. The span of the monitoring system is selected such that the pollutant gas concentration equivalent to the emission standard is not less than 30 percent of the span. If at any time during a rim the measured gas concentration exceeds the span, the rim is considered invahd. 

The upper hmit of a gas concentration measurement range is usually 1.5 to 2.5 times the applicable emission limit. If no span value is provided, a span value equivalent to 1.5 to 2.5 times the expected concentration is used. For convenience, the span value should correspond to 100 percent of the recorder scale. 

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