NO_x船上モニタリングに関する簡易評価手法及び運航中実船計測に関する研究(<特集>エンジン)

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The NO_x Technical Code under the MARPOL 73/78 Convention ANNEX 6 specifies the NO_x emission limits and has determined the direct measurement and monitoring method for the on-board NO_x verification procedure. But the monitoring method might not have been established yet, since it is reported that some results of NO_x emission values measured on board exceed the 15% allowance even in the case of engines with certification. Since there are several constraints in the measurements on board, the uncertainty is enhanced comparing to the measurements at a shop-test. In this report an alternative index is proposed to reduce the uncertainty and simplify the on-board measurement. The index is named as NO_x13 that is normalized with oxygen concentrations and contains the correction factor for humidity and temperature. The NOx emission value, NO_x [g/kWh], is theoretically correlated to the NO_x13 as in the following expression and the correlation is experimentally confirmed. NO_x [g/kWh] = α_1×α_2×be [g/kWh]×NO_x13 [ppm] α_1, α_2; constant, be [g/kWh]; specific fuel consumption Furthermore, in this study, the NO_x emission measurement, made on the same two-stroke engine, and with the same gas analyzer, was carried out on three occasions. That is a shop test, an at sea trial and during in-service. The effects on the NO_x emission value are discussed with regard to the derivation methods of the exhaust gas flow rate. They are gas concentrations in UOB (universal oxygen balance) and UCB (universal carbon balance) method, compositions of the sampled fuel, stability of engine output power in operation, and the temperature & humidity correction factor K_<Hdies>. The coefficient of humidity term, for the factor KHdieS, should be larger than that of KHdies as specified in the NOx technical code. This correlates the NO_x emission values measured at sea trial and during in-service. The temperature and humidity should be measured in the engine room rather than in the steering house. The stability of the engine power can be evaluated alternatively by using the C.O.V. of the oxygen concentrations. The NOx emission values on an actual vessel do not agree to those at a test-bed due to the effect of the derived exhaust gas flow rate and the temperature of the intercooler outlet air.
独立行政法人海上技術安全研究所の論文
2008-10-10

NO_x船上モニタリングに関する簡易評価手法及び運航中実船計測に関する研究(<特集>エンジン)

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