Characterization of Variations in Cylinder Peak Pressure and its Position of High-Power Turbo-Charged Compression-Ignition Engines

Cylinder peak pressure (p_max) over operating cycle of a high-power turbo-charged compression-ignition engine indicates its in-cylinder combustion behavior and also the level of mechanical load acting on its power assembly components. It is significantly important to understand how p_max with cylinder pressure (p) varies due to possible changes in engine design and operation input condition parameters. The input parameters considered in this paper include piston crank-angle position (θ), compression ratio (CR), amount of cycle burning heat (Q), injection/combustion duration (Δθ), and fuel injection/combustion-start timing (θ_s). Effects of the input parameters to p_max and θ_pmax which is the crank-angle position of p_max in engines of this type are analyzed, predicted and characterized. Results with the approaches to achieving those are presented. It is indicated from the results that the crank-angle position of combustion duration (Δθ) has a significant effect on θ_pmax for a given engine power density. As the position of Δθ varies, θ_pmax varies accordingly and can be determined. It is also indicated that as θ_s is sufficiently retarded from a position before the top dead center (TDC) to a point close to TDC, either before or after, in a large-bore high-power turbocharged engine, the trend of p_max variation would be reversed. This establishes the minimum value of p_max over the range of engine combustion-start timing variation. The results and indications are beneficial and usefully needed in adjusting the design and operation input condition parameters for achieving optimized balances between power-output capacity, fuel efficiency, exhaust emissions and mechanical/thermal loading of engines in this type.