, ,A single-cylinder, direct-injected diesel engine was fully instrumented and baseline tested. The firedeck, intake and exhaust valves, piston crown, and top portion ,of the cylinder liner were then insulated with ceramic coatings. The insulated engine was tested at baseline conditions and increased coolant temperatures to determine the effect of LHR engine operation on engine performance, emissions, and combustion. Conclusions

The following conclusions were drawn from this investigations that used a single-cylinder, direct-injected diesel engine:

1. Adding ceramic coatings to the combustion chamber significantly reduced heat transfer to the engine coolant. The -IRIS engine model predicted a 30 percent reduction in heat transfer to the coolant for the hot ceramic engine compared to the baseline metal engine at 2000 rpm, full-load conditions (25:1. air-fuel ratio).

2. Insulating the combustion chamber reduced the engine's ITE. An ITE decrease of 3.4 percentage points was measured at 2000 rpm, full-load for the hot ceramic engine compared to the baseline metal engine. ,

3. , The smoke and particulate emissions were higher for the LHR engine compared to the baseline metal engine.

4. The LHR engine hydrocarbon emissions were lower across the load range, and CO and NOx emissions were reduced slightly at the full-load condition compared to the baseline metal engine.

5. The NOx and particulate emissions were very sensitive to fuel injection timing. The baseline particulates and NOx emission levels could not be reached in the hot ceramic engine at 2000 rpm, full-load by advancing or retarding the fuel injection timing.

6. The hot ceramic engine had significantly higher engine component and exhaust gas temperatures compared to the baseline metal engine. The, increase in exhaust gas temperature was partially due to the insulation and combustion occurring later in the cycle.

7. The LHR engine combustion was characterized by less premixed burning, lower peak heat release rates, and longer combustion duration compared to the baseline metal engine. A small portion (3 to 4 degrees crank angle) of the increased combustion duration in the hot ceramic engine

8. The LHR engine's reduced thermal efficiency and increased exhaust emissions were attributed to degraded combustion.

9. The hot ceramic engine fuel injection duration increased and the peak fuel injection pressure was reduced compared to the baseline metal engine. The change in fuel injection pressure characteristics was attributed to changes in fuel viscosity with temperature.


1. Yoshimitsu, T., K. Toyama, F. Sata and H. Yamaguchi, "Capabilities of Heat Insulated Diesel Engine," ASME Paper 80-DGP-14.

Nishiyama, T. Shimauchi and T. Nakagaki, "Heat Insulated Turbocompound Engine," SAE Paper 831345.

M. Mori, "Thermal Barrier Coating for Diesel Engine Piston," ASME Paper 80-DGP-14.

4. Alkidas, A. C., "Experiments with an

Uncooled Single-Cylinder Open-Chamber Diesel," SAE Paper 870020.

5. Cole, R. M. and A. C. Alkidas, "Eva luation of an Air-Gap-Insulated Piston in a Divided-Chamber Diesel Engine," SAE Paper 850359.

"TACOM/Cummins Adiabatic Engine Program," SAE Paper 830314.

Engines," SAE Paper 860314.

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