TY - JOUR
TI - Optimal paths of piston motion of irreversible diesel cycle for minimum entropy generation
AU - Ge Yanlin
AU - Chen Lingen
AU - Sun Fengrui
JN - Thermal Science
PY - 2011
VL - 15
IS - 4
SP - 975
EP - 993
PT - Article
AB - A Diesel cycle heat engine with internal and external irreversibility’s of  heat transfer and friction, in which the finite rate of combustion is  considered and the heat transfer between the working fluid and the  environment obeys Newton’s heat transfer law [q≈ Δ(T)], is studied in this  paper. Optimal piston motion trajectories for minimizing entropy generation  per cycle are derived for the fixed total cycle time and fuel consumed per  cycle. Optimal control theory is applied to determine the optimal piston  motion trajectories for the cases of with piston acceleration constraint on  each stroke and the optimal distribution of the total cycle time among the  strokes. The optimal piston motion with acceleration constraint for each  stroke consists of three segments, including initial maximum acceleration and  final maximum deceleration boundary segments, respectively. Numerical  examples for optimal configurations are provided, and the results obtained  are compared with those obtained when maximizing the work output with  Newton’s heat transfer law. The results also show that optimizing the piston  motion trajectories could reduce engine entropy generation by more than 20%.  This is primarily due to the decrease in entropy generation caused by heat  transfer loss on the initial portion of the power stroke.