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EGR is a proven technology used to reduce NOx formation in both compression and spark ignition engines by reducing the combustion temperature. In order to further increase its efficiency the recirculated gases are subjected to cooling. However, this leads to a higher load on the cooling system of the engine, thus requiring a larger radiator. In the case of turbocharged engines the large variations of the pressures, especially in the exhaust manifold, produce a highly pulsating EGR flow leading to non-steady-state heat transfer in the cooler. The current research presents a method of determining the pulsating flow field and the instantaneous heat transfer in the EGR heat exchanger. The processes are simulated using the CFD code FIRE (AVL) and the results are subjected to validation by comparison with the experimental data obtained on a 2.5 liter, four cylinder, common rail and turbocharged diesel engine.

This paper discusses the goals, progress, and future plans of the TACOM/Cummins Adiabatic Engine Program. The Adiabatic Engine concept insulates the diesel combustion chamber with high temperature materials to allow hot operation near an adiabatic operation condition. Additional power and improved efficiency derived from this concept occur because thermal energy, normally lost to the cooling and exhaust systems, is converted to useful power through the use of turbomachinery and high-temperature materials. Engine testing has repeatedly demonstrated the Adiabatic Engine to be the most fuel efficient engine in the world with multi-cylinder engine performance levels of 0.285 LB/BHP-HR (48% thermal efficiency) at 450 HP representative. Installation of an early version of the Adiabatic Engine within a military 5 ton truck has been completed, with initial vehicle evaluation successfully accomplished.

The instantaneous frictional torque (IFT) of many components of a single cylinder diesel engine was determined by considering the forces acting on each component and the resulting change in the angular velocity. The IFT for the basic system, consisting of the crankshaft with the flywheel and oil pump, was first determined. The effect of adding each of the following to the basic system was determined: balancer shaft, cam shaft, piston with different ring combinations, inlet valve, exhaust valve and fuel injection pump. All the tests were conducted without gas pressure in the cylinder in a coast down mode. The results indicated the contribution of each component in the total frictional torque and its mode of lubrication. The energy absorbed by the valve springs and released back to the system was clearly Identified. The effect of speed on IFT and energy lost in friction was determined.