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Fig.6.1.4 NOx vs. Engine Load (IKOMASAN Voyage No.8)
Fig.6.1.5 NOx vs. Engine Load (IKOMASAN Voyage No.9)
Fig.6.1.6 NOx vs. Engine Load (IKOMASAN Voyage No.1〜9)
6.2 Test progress of the second test ship (M/V NYK ANTARES)
6.2.1 Status of data sampling
In this section, continuous NOx monitoring test result of mainly from the 4th voyage to 8th voyage of the second test ship are reported.
The line of this ship is shuttle service between Japan and Europe via the Mediterranean Sea, about 50 days per one voyage. The schedules were;
.1 4th voyage: Jan. to Mar. 2002 (bunkered at Rotterdam and Singapore)
.2 5th voyage: Mar. to Apr. 2002 (bunkered at Singapore and Rotterdam)
.3 6th voyage: Apr. to Jun. 2002 (bunkered at Rotterdam)
.4 7th voyage: Jun. to Aug. 2002 (bunkered at Singapore and Rotterdam)
.5 8th voyage: Aug. to Oct. 2002 (bunkered at Singapore and Rotterdam)
On every voyage, engine performance data were sampled by the crews and the data were reported to the engine manufacturer by e-mail from the ship, in principle one time every one week. And in addition, Pmax, Pcomp and fuel oil samples were gathered one time in every one way of the voyages. Totally so far, 45 weekly data and 19 fuel oil samples were gathered.
On the other hand, exhaust gas emission data (NOx and O2 concentration) were continuously and automatically recorded on recorder all through each voyage. The recorded data were retrieved from memory system of the recorder by analyzer manufacturer when the ship returns to Japan.
Calibration of the analyzer was automatically carried out with interval of one time every two weeks for 4th and 5th voyage, and one time every three weeks for 6th to 8th voyage by using program function of the analyzer. And also purge of sensor part were automatically carried out everyday through the all voyages.
6.2.2 Continuous monitoring data
.1 Long term monitoring data
Fig. 6.2.2.1 - Fig. 6.2.2.5 respectively show the whole NOx and O2 monitoring data of each voyage. Except the 6th voyage, as the indications of NOx and O2 concentration periodically show 0 ppm and about 21%, they are the timing of air purge every one day. At the 6th voyage, as mentioned later (see section 6.4), purge air could not flow out by clogging of sampling probe by soot, so the periodical purge line are not recorded.
Same as the above, automatic calibration indications one time per two weeks or three weeks are also recorded. However, blackouts sometimes occur on board causes reset of timer of the analyzer, in such case, the programmed calibration or purge is not always carried out by intended period. (also see section 6.4).
.2 1 Hr data
Fig. 6.2.2.6 - Fig. 6.2.2.14 show 1Hr interval sampling data, which picked up and enlarged from Fig. 6.2.2.1 - Fig. 6.2.2.5. They are corresponding to the time of weekly engine performance data measurement. It could be seen the data are very stable.
As the emission value of monitoring result, the 1 Hr data are digitally averaged and are used for calculation of NOx emission (g/kWh) mentioned in the next section.
6.2.3 Result of data analysis
.1 Engine performance data and calculation of NOx emission
Engine performance data, analysis of fuel oil property, averaged NOx and O2 concentration and result of calculation of NOx emission are tabulated in Table 6.2.3.1 - Table 6.2.3.5. A shaft power meter is installed on the ship, so the power meter readings are used for the calculation as the engine brake output power.
.2 Relation between engine load and NOx emission
Fig. 6.2.3.1 - Fig. 6.2.3.5 show relation between engine load and ISO converted NOx emission in comparison with the data at shop trial for each voyage. And Fig. 6.2.3.6 shows all data gathered together.
The data have big dispersion and many of the data exceed the value at shop test. Some of them exceed more than 15% of shop data, which allowed in the NOx Technical Code for simplified measurement on-board. (According to the provision of NOx Technical Code, the allowance 15% is accepted for E3 test cycle limitation, however, in this paper, "shop test result + 15%" line is drawn as a reference.)
The range of dispersion is about -10% to +20% of shop test value. The cause of the difference between shop and on-board and the dispersion should be investigated and resolved further including effect of fuel property and/or operating condition of the engine.
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