Crank Angle Based Exergy Analysis of Syngas Fuelled Homogeneous Charge Compression Ignition Engine

Homogeneous charged compression ignition (HCCI) engine is a low-temperature combustion (LTC) strategy with higher thermal efficiency and ultra-low NOx and particulate matter emission. Syngas is a renewable and clean alternative fuel that has gained researchers' interest, and it is one of the alternatives to fossil fuels. Syngas can be a suitable fuel for HCCI Engines due to their characteristics of high flame speed, lower flammability limits, and low auto-ignition temperatures. This paper presents the crank angle-based exergy analysis of syngas fuelled HCCI engines. Energy and exergy analysis is essential for the better performance and utilization of the HCCI engine. The syngas HCCI engine is numerically simulated in this study using a stochastic reactor model (SRM). In SRM models, physical parameters are described by a probability density function (PDF), and these parameters do not vary within the combustion chamber. Thus, the spatial distribution (due to local inhomogeneity) of the charge is represented by PDF. The SRM-based approach simplifies many aspects of CFD processes while retaining the predictive capability similar to 3-D CFD codes. A detailed syngas combustion reaction mechanism (having 32 species and 173 reactions) is used to simulate the HCCI Engine. Numerically simulated combustion pressure is validated with experimental results published in the previous study at different inlet valve closing temperature (T_ivc) and equivalence ratio (ϕ). The simulation is performed for different T_ivc, engine speed (N), ϕ, and syngas composition. The effect of engine operating parameters on the conversion of fuel energy into work exergy output, exergy transfers due to heat transfer, exergy lost to the exhaust in the form of thermo-mechanical exergy and unburned fuel; and exergy destruction due to combustion has been discussed in this study. Results indicate that exergy destruction due to combustion and the heat transfer to the cylinder walls increases with an increase in T_ivc and decreases with a decrease in ϕ and increase in N. The Physical exergy lost to the exhaust gases increases at higher engine speed.