Georgios C. Mavropoulos

Experimental instantaneous heat fluxes in the cylinder head and exhaust manifold of an air-cooled diesel engine

Abstract An experimental analysis is performed to study the instantaneous heat fluxes, during the engine cycle, in the combustion chamber walls of a direct injection (DI), air cooled, four stroke, Diesel engine located at the authors laboratory. For this purpose, a novel experimental installation has been developed, which separates the engine transient temperature signals into two parts, namely the ‘long’ and the ‘short’ term response ones, followed by their discrete processing in two independent data acquisition systems. Furthermore, a new pre-amplification unit for fast response thermocouples, appropriate heat flux sensors and an innovative, object oriented, control code for fast data acquisition have been designed and developed for the needs of the study. One dimensional heat conduction with Fourier analysis of the raw temperature data are implemented in order to calculate the instantaneous engine cylinder and exhaust pipe heat fluxes. Analysis of the experimental results reveal many interesting aspects of transient engine heat transfer. The effect of engine speed on cylinder head and exhaust manifold heat losses is presented. The simultaneous presentation of heat fluxes on the cylinder head and exhaust manifold, together with the engine indicator diagram, sheds light into the mechanisms governing the transient heat transfer. This is very important, since especially for air cooled Diesel engines, limited information seems to exist in the relevant literature.

Potential for Improving HD Diesel Truck Engine Fuel Consumption Using Exhaust Heat Recovery Techniques

D.T. Hountalas1 and G.C. Mavropoulos2 1Professor of Internal Combustion Engines, Dipl.Ing., Dr.Ing. (NTUA) 2Research Associate, Internal Combustion Engines Dipl.Ing., Dr.Ing. (NTUA), M. SAE, M. ACS Internal Combustion Engines Laboratory Thermal Engineering Department School of Mechanical Engineering National Technical University of Athens (NTUA) 9 Iroon Polytechniou St., Zografou Campus, 15780 Athens, Greece

Potential for efficiency improvement of four-stroke marine diesel gensets by utilisation of exhaust gas energy

In the present paper, it is examined the potential application of a Rankine cycle exhaust gas heat recovery system which recovers and utilises energy from the exhaust gas of four-stroke marine diesel auxiliary unit before it is released to the atmosphere, increasing thus its total efficiency. For this purpose, a thermodynamic simulation model of the Rankine bottoming cycle is used. Heat utilisation is initially considered only from the main exhaust gas stream after the T/C turbine. As reference for the investigation are used the values from the official shop tests at various loads ranging from 25% up to 100%. From these using the Rankine cycle simulation model, it is investigated the potential for increase of generated cycle power output and optimisation of its efficiency. In addition, it is examined the effect of working media by considering steam and an organic. The results derived reveal that there exists a significant potential for fuel saving by utilisation of exhaust gas energy of auxiliary engines installed on commercial vessels.