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Figure 4 - Gas Bearing Piston with Scotch Yoke Mechanism (Courtesy FICHT Gmbh)

Wade and Havstad, at Ford Motor Co., disagree with the necessity for translational piston-connecting rod movement and they have shown that a conventional connecting rod and crankshaft can be used with a gas bearing piston.

Commercial adaption of the HTLL will allow diesel engines to operate at much higher temperatures than was previously possible. Some of the components such as the martensitic cast iron rings will lose hardness and hoop tension around 900°F (482°C) and will have to be replaced with higher temperature capable rings. Oil sump temperatures may be operated in the 300 to 400 F (149 to 204 C) range compared with 180°F (82°C) with current mineral oils. This could mean that the current sleeve bearings, which typically contain lead, may not be adequate for the high performance diesel engines. Recent development of high performance sleeve type bearings in both Austria and Germany showed a significant improvement in wear life by using sputtering to deposit a nickel diffusion barrier layer and an A1 Sm outerlayer with a fine grain structure and a homogeneous second phase (8).

Turbomachinery

There is an inherent mismatch problem involved in matching a turbocharger to a diesel engine. The reciprocator requires air as a linear function with increasing power output. However, the turbocharger output is an exponential function. Thus, many of the advanced turbocharger concepts involve schemes to enhance turbocharger matching for better fuel economy. The increasingly sophisticated capability of computer assisted engine diagnostics and controls can extend the range of efficient use of turbocharging. Also, precise control of turbocharger operation as well as fuel injection parameters can contribute very significantly to emissions control.

In the case of the automotive diesel, the turbocharger is matched to provide a more rapid response to acceleration demand. Since there is only a one point perfect match of a turbocharger to a diesel engine, the trade-off for the automobile is to have a close match at the low power end

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