Transient State Power Analysis of Heavy-Duty Diesel Engine*

Vehicles with internal combustion engines, almost exclusively operate in transient state, which occurs when the torque or speed of the engine varies. Those variations occur when conditions like speed, load, or incline of the road change. This research analyzes the energy gains and losses through different pathways – fueling, shaft work, radiator, and exhaust - during transient operation. This test was conducted using a twenty-minute Heavy-Duty Engine drive cycle. The results show a general trend, that when the engine begins producing more shaft power, the proportion of energy lost to the radiator drops and then, increases as the engine decreases in power. At high loads, the energy lost through exhaust decreases, leaving shaft work to be the largest percent of energy output. However, the data tends to show that at low loads or idle, both the energy loss at the radiator and exhaust become larger than the shaft work, which indicates lower operating efficiency. This preliminary work developing the capability to analyze the engine performance under transient conditions will serve as a starting point for future work to investigate how to improve the transient performance.