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Heat loss through wall boundaries play a dominant role in the overall performance and efficiency of internal combustion engines. Typical engine simulations use constant temperature wall boundary conditions [1, 2, 3]. These boundary conditions cannot be estimated accurately from experiments due to the complexities involved with engine combustion. As a result, they introduce a large uncertainty in engine simulations and serve as a tuning parameter. Modeling the process of heat transfer through the solid walls in an unsteady engine computational fluid dynamics (CFD) simulation can lead to the development of higher fidelity engine models. These models can be used to study the impact of heat loss on engine efficiency and explore new design methodologies that can reduce heat losses. In this work, a single cylinder diesel engine is modeled along with the solid piston coupled to the fluid domain.

Durability assessments of modern engines often require accurate modeling of thermal stresses in critical regions such as cylinder head firedecks under severe cyclic thermal loading conditions. A new methodology has been developed and experimentally validated in which transient temperature distributions on cylinder head, crankcase and other components are determined using a Conjugate Heat Transfer (CHT) CFD model and a thermal finite element analysis solution. In the first stage, cycle-averaged gas side boundary conditions are calculated from heat transfer modeling in a transient in-cylinder simulation. In the second stage, a steady-state CHT-CFD analysis of the full engine block is performed. Volume temperatures and surface heat transfer data are subsequently transferred to a thermal finite element model and steady state solutions are obtained which are validated against CFD and experimental results.

Fuel injector performance is critical for fuel efficiency, combustion process, emissions, start ability, acceleration and combustion noise. The injector design is a complicated process. Simulation tools are playing an important role in virtual design, which could evaluate performance and optimize the design. This paper describes how analysis is used to identify and resolve the cause of low kidney pressure when oil pressure in rail is high in a diesel injector. 1D system performance analysis tool and 3D CFD analysis tool are utilized together to identify the potential causes of the problem. The test results are compared with the simulation results to determine the root cause. 1D and CFD tools are used again to setup the design target and optimize the design. The test shows that the optimum design provided by 1D analysis and 3D analysis effectively solves the low kidney pressure problem in the fuel injector.