Effect of thermal inertia on diesel engines transient performance

Abstract

Transient operation of turbocharged diesel engines is affected by the thermal inertia of the cylinder parts, intake and exhaust manifolds. Because of thermal inertia the temperature of engine parts at steady operation fluctuates during the operating cycle near their average values in a relatively small range, but during transient operation it takes some time to warm or cool the engine parts. Thermal inertia is expressed in changes in fuel combustion, in-cylinder heat transfer and indicated efficiency of the cycle, and increase of general inertia of gas-turbine supercharging system, which determines the necessity to take into account this phenomenon when modeling unsteady engine operation. The conductance-capacitance model was proposed for online internal combustion engines operating cycle simulation tool Blitz-PRO to consider thermal inertia during engine’s transient process. The idea is to consider the heat capacity of engine parts during the heat transfer process, so they accumulate energy at warming and release it at cooling. Combined with equations of heat transfer and thermal conductivity it enables to calculate the change in the average temperatures during engine transient and consider the changes in the overall heat transfer process