On the question of secondary use of exhaust exergy in power units of vehicles and tractors

Abstract

BACKGROUND: Efficiency of modern internal combustion engines is no more than 40%, while the significant part of exergy, released during fuel combustion, dissipates in the environment through exhaust, coolant liquid and heated details. Meanwhile, the urgent problem of operating a tractor in low ambient temperature conditions is sustaining of optimal thermal condition for the sake of decreasing of losses, increasing of combustion efficiency and, as a consequence, increasing of operating efficiency.
 AIMS: Efficiency assessment of use of the complex system of utilization of thermomechanical exergy of diesel engine exhaust. Justification of type and number of stages of exhaust exergy utilization for diesel engines of vehicles and tractors for a wide range of ambient temperatures and loading conditions.
 METHODS: To accomplish given aims, theoretical and experimental studies were carried out in order to assess exhaust exergy potential in dependence on engine loading conditions and ambient temperature. Comparative studies of the D-440 and the SMD-62 engines were carried out, making it possible to assess the influence of exhaust system design features on amount of exergy losses.
 RESULTS: Exhaust performance losses of the SMD-62 engine with the TKR-11N-1 turbocharger at nominal mode were 0.8. Meanwhile, maximal exhaust performance losses at idle mode are 0.92. Authors suggested the special method of analysis of certain exhaust exergy components, which allows analyzing possible ways of its secondary use. The obtained equations determine quantitative and qualitative ratios between exhaust exergy components in comparison to maximal exhaust exergy potential to be utilized.
 CONCLUSIONS: Based on experimental data analysis and its statistical processing, it follows that middle powered engines have limited resources of waste heat. Theoretically, it should be enough for ensuring the turbocharger operation and sustaining of thermal condition in a gearbox and a cooling system in winter.