300

Fig. 10. Fuel Injection Pressure Versus Crank Angle for the Hot Ceramic and Baseline Metal Test Conditions

The cracking pressure for the fuel injector was approximately 2100 psi; therefore, the start of fuel injection was the same for both engine configurations. The fuel injection pressure curve was shifted to the right and peak pressure was reduced slightly. This result was not surprising because the intake air temperature was held constant at 180°F for all engine tests. Further analysis using the IRIS engine model showed that the unburned gas temperature during the ignition delay period was only 50° F higher for the hot ceramic engine compared to the baseline metal engine. The premixed burning, was reduced and the combustion duration increased as the engine was insulated and the coolant temperature increased.. The longer combustion duration resulted in lower peak cylinder pressures and lower indicated thermal efficiencies as shown in Table 3.

was good agreement between measured and predicted results. The IRIS model predicted a decrease in indicated thermal efficiency of 3.6 percentage points

Table 3. Combustion Analysis 2200 RPM, Full Load

Engine Test Condition Baseline Metal

Baseline Ceramic Hot Ceramic

Table 3. Combustion Analysis 2200 RPM, Full Load

Ignition Delay (Deg.)

Pre mix/Total Heat Release

Combustion Duration (Deg.)

Peak Cylinder Pressure (psi)

Indicated Thermal Efficiency

0 0

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