• The KSFM Journal of Fluid Machinery
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• v.14 no.1
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• pp.42-47
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• 2011

Measurement uncertainty analysis of fuel flow using turbine flowmeter was performed for the case of altitude engine test. SAE ARP4990 was used as the fuel flow calculation procedure, as well as the mathematical model for the measurement uncertainty assessment. The assessment was performed using Sensitivity Coefficient Method. 11 parameters involved in the calculation of the flow rate were considered. For the given equipment setup, the measurement uncertainty of fuel flow was assessed in the range of 1.19~1.86 % for high flow rate case, and 1.47~3.31 % for low flow rate case. Fluctuation in frequency signal from the flowmeter had the largest influence on the fuel flow measurement uncertainty for most cases. Fuel temperature measurement had the largest for the case of low temperature and low flow rate. Calibration of K-factor and the interpolation of the calibration data also had large influence, especially for the case of very low temperature. Reference temperature, at which the reference viscosity of the sample fuel was measured, had relatively small contribution, but it became larger when the operating fuel temperature was far from reference temperature. Measurement of reference density had small contribution on the flow rate uncertainty. Fuel pressure and atmospheric pressure measurement had virtually no contribution on the flow rate uncertainty.

• The KSFM Journal of Fluid Machinery
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• v.12 no.6
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• pp.18-25
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• 2009

Venturi has long been an attractive method of measuring flow rate in a variety of engineering applications since pressure loss is relatively small compared with other measuring methods. The current study focuses on making detailed uncertainty estimations as the upstream flow disturbance affects uncertainty levels of the flow rate measurement. Upstream flow disturbance can be determined by 9 different swirl generators. Measurement uncertainty of flow rate has been estimated by a quantitative uncertainty analysis which is based on the ANSI/ASME PTC 19.1-2005 standard. The results of flow rate uncertainty analysis show that the case with systematic error has higher than that without systematic error. Especially the result with systematic error exhibits that the uncertainty of flow rate was gradually increased by swirl flow disturbance. The uncertainty of flow rate measurement can be mainly affected by differential pressure and discharge coefficient. Flow disturbance can be also reduced by increasing of the upstream straight length of Venturi.

• Corrosion Science and Technology
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• v.8 no.5
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• pp.193-196
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• 2009

For the estimation of uncertainty in potentiodynamic polarization resistance measurement, the type A uncertainty was measured using type 316 stainless steel in an acidified NaCl solution. Sensitivity coefficients were determined for measurand such as scan rate of potential, temperature of solution, concentration of NaCl, concentration of HCl, surface roughness of specimen and flow rate of purging gas. Sensitivity coefficients were large for the measurand such as the scan rate of potential, temperature of solution and roughness of specimen. However, the sensitivity coefficients were not the major factors influencing the combined standard uncertainty of polarization resistance due to the low values of uncertainty in measurements of the measurands. A major influencing factor was the concentration of NaCl. The value of type A uncertainty was 1.1 times the value of type B uncertainty, and the combined standard uncertainty was 10.5 % of the average value of polarization resistance.

• The KSFM Journal of Fluid Machinery
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• v.19 no.2
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• pp.5-10
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• 2016

Gas flow measurement in a closed duct was performed using multi-point Pitot tubes. Measurement uncertainty was assessed for this measurement method. The method was applied for the measurement of air flow into a gas turbine engine in an altitude engine test facility. 46 Pitot tubes, 15 total temperature Kiel probes and 9 static pressure tabs were installed in the engine inlet duct of inner diameter of 264 mm. Five tests were done in an airflow range of 2~10 kg/s. The flow was compressible and the Reynolds numbers were between 450,000 and 2,220,000. The measurement uncertainty was the highest as 6.1% for the lowest flow rate, and lowest as 0.8% for the highest flow rate. This is because the difference between the total and static pressures, which is also related to the flow velocity, becomes almost zero for low flow rate cases. It was found that this measurement method can be used only when the flow velocity is relatively high, e.g., 50 m/s. Static pressure was the most influencing parameter on the flow rate measurement uncertainty. Temperature measurement uncertainty was not very important. Measurement of boundary layer was found to be important for this type of flow rate measurement method. But measurement of flow non-uniformity was not very important provided that the non-uniformity has random behavior in the duct.

• Corrosion Science and Technology
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• v.12 no.5
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• pp.220-226
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• 2013

The uncertainty in statistical noise resistance measurement was evaluated for a type 316 stainless steel in NaCl solutions at room temperature. Sensitivity coefficients were determined for measurands or variables such as NaCl concentration, pH, solution temperature, surface roughness, inert gas flow rate and bias potential amplitude. The coefficients were larger for the variables such as NaCl concentration, pH, inert gas flow rate and solution temperature, and they were the major factors increasing the combined standard uncertainty of noise resistance. However, the contribution to the uncertainty in noise resistance measurement from the above variables was remarkably low compared to that from repeated measurements of noise resistance, and thus, it is difficult to lower the uncertainty in noise resistance measurement significantly by lowering the uncertainties related with NaCl concentration, pH, inert gas flow rate and solution temperature. In addition, the uncertainty in noise resistance measurement was high amounting to 17.3 % of the mean, indicating that the reliability in measurement of noise resistance is low.

• International Journal of Aeronautical and Space Sciences
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• v.5 no.1
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• pp.46-56
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• 2004

The verification and improvement of the measurement uncertainty have beenperformed in the altitude test facility for small gas turbine engines, which was built atthe Korea Aerospace Research Institute (KARI) in October 1999. This test is performedwith a single spool turbojet engine at several flight conditions. This paper discussesthe evaluation and validation process for the measurement uncertainty improvements usedin the altitude test facility. The evaluation process, defined as tests before the facilitymodification, shows that the major contnbutors to the measurement uncertainty are theflow meter discharge coefficient, the inlet static and total pressures, the cell pressureand the fuel flow rate. The measurement uncertainty is focused on the primary parametersof the engine performance such as airflow rate, thrust and specific fuel consumption (SFC).The validation process, defined as tests after the facility modification, shows that themeasurement uncertainty, in seal level condition, is tmproved to the acceptable level throughthe facility modification. In altitude test conditions, the measurement uncertainties arenot improved as much as the uncertainty in sea level condition.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1721-1726
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• 2004

Heat rate is a representative index to estimate the performance of turbine cycle in nuclear power plant. Accuracy of heat rate calculation is dependent on the accuracy of measurement for plant status variables. Uncertainty of heat rate can be modeled using uncertainty propagation model. We developed practical estimation model of heat rate uncertainty using the propagation and regression model. The uncertainty model is used in the performance analysis system developed for the operating nuclear power plant.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.19 no.1
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• pp.7-14
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• 2011

In this study, the measurement uncertainty of combustion experimental system and experimental parameters for hybrid rocket were evaluated by B type evaluation method. The measurement uncertainty of all experimental parameters was lower than 3%. The highest value of expanded uncertainty was characteristic velocity efficiency with 2.83% and the expanded uncertainty of regression rate which is the design and performance parameter was indicated to 0.03%. These results shown that the reliability of hybrid combustion system was located within allowed limits.

• The KSFM Journal of Fluid Machinery
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• v.13 no.4
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• pp.18-24
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• 2010

For testing large-capacity pumps, the accurate flow rate measurement is needed in the test loop. As a measuring method of flow rate, venturi tube is recommended due to its low pressure loss. However, upstream disturbance of loop component such as a valve has an effect upon the accuracy of flow rate measurement. For controlling flow rate in case of high flow rate and large-scale piping system, a butterfly-type valve is generally used due to its compactness. However, a butterfly valve disturbs downstream flow by generating turbulence, cavities, or abrupt pressure change. In this study, the effect of downstream disturbance of butterfly valve on the flow rate measurement using a venturi tube is investigated. Test loop consists of circulation pump, reservoir, butterfly valve, venturi tube, and reference flow meter. The test is conducted with regard to a different valve opening angle of butterfly valve. According to the valve opening angle, the uncertainty of flow rate measurement is investigated.

• Journal of Radiation Protection and Research
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• v.43 no.1
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• pp.29-38
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• 2018

Background: Radon contributing about 42% of annual average dose, mainly comes from soil. In this paper, standard measurement procedures for soil radon exhalation rate are suggested and their measurement uncertainties are analyzed. Materials and Methods: We used accumulation method for estimating surface exhalation rate. The closed-loop measurement system was made up with a RAD7 detector and a surface chamber. Radon activity concentrations in the system were observed as a function of time, with data collection of 5 and 15-minute and the measurement time of 4 hours. Linear and exponential fittings were used to obtain radon exhalation rates from observed data. Standard deviations of measurement uncertainties for two approaches were estimated using usual propagation rules. Results and Discussion: The exhalation rates (E) from linear approach, with 30 minutes measurement time were $44.8-48.6mBq{\cdot}m^{-2} {\cdot}s^{-1}$ or $2.14-2.32atom{\cdot}cm^{-2}{\cdot}s^{-1}$ with relative measurement uncertainty of about 10%. The contributions of fitting parameter A, volume (V) and surface (S) to the estimated measurement uncertainty of E were 59.8%, 30.1% and 10.1%, in average respectively. In exponential fitting, at 3-hour measurement we had E ranged of $51.6-69.2mBq{\cdot}m^{-2} {\cdot}s^{-1}$ or $2.46-3.30atom{\cdot}cm^{-2}{\cdot}s^{-1}$ with about 15% relative uncertainty. Fitting with 4-hour measurement resulted E about $51.3-68.2mBq{\cdot}m^{-2} {\cdot}s^{-1}$ or $2.45-3.25atom{\cdot}cm^{-2}{\cdot}s^{-1}$ with 10% relative uncertainty. The uncertainty contributions in exponential approach were 75.1%, 13.4%, 8.7%, and 2.9% for total decay constant k, fitting parameter B, V, and S, respectively. Conclusion: In obtaining exhalation rates, the linear approach is easy to apply, but by saturation feature of radon concentrations, the slope tends to decrease away from the expected slope for extended measurement time. For linear approach, measurement time of 1-hour or less was suggested. For exponential approach, the obtained exhalation rates showed similar values for any measurement time, but measurement time of 3-hour or more was suggested for about 10% relative uncertainty.