Test Apparatus

A single-cylinder, direct-injected diesel engine was used for this investigation. The engine was installed in a test cell and connected to an eddy-current motoring dynamometer as shown in Fig. 1. The engine specifications are given in Table 1. Two Roots blowers mounted in series were connected to the intake air system to maintain baseline air flow rates during LHR engine tests. An exhaust back pressure valve was used to maintain a constant pressure ratio across, the cylinder head during boosted conditions. An electric heater was mounted in the intake air surge tank to maintain constant intake air temperature. The engine .coolant system was modified to incorporate separate, cylinder head and cylinder block cooling circuits. The cylinder head, cooling circuit was connected to a compressed air supply. Thermocouples were mounted in the tip of the fuel injector holder and just below the cylinder liner surface to measure firedeck and cylinder liner surface temperatures,, respectively. Gaseous emissions measurements were made using a 13-Mode emissions cart. Gaseous emissions included HC, CO, and NOx. The particulate emissions were measured using an exhaust gas dilution tunnel.

The insulated engine was assembled using a ceramic-coated firedeck, intake and exhaust valves, piston crown, and top portion of the cylinder liner.

Fig. 1. Single-Cylinder, Direct-Injected Diesel Engine Installed in Test Cell

Fig. 2. Ceramic-Coated Firedeck

was first applied to these engine components. The firedeck, intake and exhaust valves, and piston crown were then coated with a 0.030-inch thick coating of yttria stabilized zirconia (which is 7 percent Y2O3 and 93 percent Zr02>. The top 0.85-inch of the cylinder liner was coated with 0.025-inch of the yttria stabilized zirconia and then 0.010-inch of chrome oxide coating to resist piston liner scuffing.

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