Fig 6 Effect of Fuel Injection Timing on Particulate ISFC and NOx Tradeoff for Hot Ceramic Engine at 2000 RPM

The curves in Fig. 6 show that retarding the fuel injection timing significantly increased the particulate emissions and ISFC while reducing the NOx emissions. Advancing the fuel injection timing slightly reduced the particulate emissions and ISFC while significantly increasing theNOx emissions. The curves in Fig. 6 are significant because they show that the baseline metal engine particulate and NOx emission levels of 0.12 and 6.6 (g/ihp-hr), respectively, could not be reached in the hot ceramic engine by advancing or retarding the fuel injection timing.

The effect of reducing heat transfer to the engine coolant on engine performance is shown in Fig. '7." Fig. 7 is a plot of indicated thermal efficiency, NOx emis-r sions, and particulate emissions versus measured firedeck temperature for the LIIR engine at' 2000'rpm full load. THe firedeck, temperatures, of approximately 450 and 900°F corresponded to thé Baseline: Ceramic and, Hot Ceramic enginè tests, respectively. , The curves in Fig. 7 show that, as the. heat .¡rejection to the coolant was reduced1 and. as the firedéck temperature increased, the ITE was reduced, NOx émissions increased, and the particulate emissions rèmained about the same: " ' "' \ ' ; ' ' '

Temperàtwes - ;The ' measured fire-deck, top ' ring reversal, and exhaust gas temperatures versus indicated power are shown in Fig. 8 for the 2000 rpm test condition. Increasing the baseline metal

ioo 450 500 550 600 650 700 750 800 850 900 9501000 FIRE DECK TEMPERATURE DEG.F

Fig. 7. Effect of Reducing Heat Transfer to the Coolant on ITE, NOx, and Particulates for the LHR Engine at 2000 RPM, 25:1 Air-Fuel Ratio ioo 450 500 550 600 650 700 750 800 850 900 9501000 FIRE DECK TEMPERATURE DEG.F

Fig. 7. Effect of Reducing Heat Transfer to the Coolant on ITE, NOx, and Particulates for the LHR Engine at 2000 RPM, 25:1 Air-Fuel Ratio engine coolant temperature from 180 to 220°F increased the top ring reversal temperature by approximately 30°F and had little effect on the firedeck and exhaust gas temperatures. Insulating the engine with ceramic coatings reduced the firedeck and top ring reversal temperature while significantly increasing exhaust gas temperature., All 'three: temperatures increased for thé "céramic hot test" as shown in Fig. 8. The firedéck temperature increased by approximately, 300°F for the "hot ceramic" engine compared to the baseline metal engine. . Ch&nging the fuel injection' timing had little effect on these three temperatures except ât the full load condition where the exhaust gas temperature increased for the retarded fuel injection timing. "

■' The ITÏ IRIS engine model was. used to predict average engine component surface temperatures based on thermocouple, engine performance, and combustion data.

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