Study of Cylinder-Exhaust-Gas-Temperature Variations Over Inlet Air Parameters of Compression-Ignition Engines

Cylinder-exhaust-gas temperature (Texh) of a turbocharged compression-ignition engine indicates the levels of engine thermal loading on cylinder and exhaust components, thermal efficiency performance, and engine exhaust emissions. In consideration that Texh is affected by engine air inlet condition that primarily includes inlet air temperature (Ti) and pressure (pi), this paper studies the variation (ΔTexh) of Texh over varying the engine inlet air parameters of compression-ignition engines. The study is to understand ΔTexh with appropriate relations between the inlet parameters and Texh identified and simply modeled. The regarded effects on Texh and ΔTexh for turbocharged engines of this type are analyzed and predicted. The results indicate that Texh generally increases as Ti increases or pi decreases. For example, Texh would increase by ∼2 °C as Ti increases by 1 °C or increase by ∼35 °C as pi decreases by 10−2 MPa, as predicted for a typical high-power turbocharged diesel engine. The design and operating parameters significant in influencing ΔTexh along with varying Ti or pi are also studied. These include the degree of engine cylinder compression, the level of intake manifold air temperature, the magnitude of intake air boost, and the quantity of cycle combustion thermal input. As those change, the rate of variation in Texh varies. For instance, the results indicate that the rate of ΔTexh versus the inlet air parameters would increase as the quantity of cycle combustion thermal input becomes higher. With the understanding of ΔTexh, the engine output performances of thermal loading, efficiency, and exhaust emissions, concerning engine operation at variable ambient temperature or pressure, can be understood and evaluated for the purpose of engine analysis, design and optimization.