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The ability to modulate the effective compression ratio (ECR) of an engine is a key enabler of advanced combustion strategies. ECR is a measure of the effective in-cylinder compression of gases above intake manifold conditions. An engine's ECR is usually computed from in-cylinder pressure data, requiring reliable in-cylinder pressure sensors that are not typically found on production engines. As such, a method is needed for determining the effective compression ratio using only information available from stock engine sensors, including manifold pressures and temperatures and air flows. The work outlined here presents a strategy for estimating the ECR without need for in-cylinder pressure data. The estimation scheme was transiently tested and compared to experimental engine data from a unique diesel engine test bed with flexible intake valve actuation, and was able to converge within 3 engine cycles after a transient event with less than 6% average steady-state error compared to experimental engine data. [ABSTRACT FROM PUBLISHER]

This paper describes a simple, analytical, control-oriented and physically-based model for prediction of combustion timing during PCCI combustion. The model includes direct dependence on in-cylinder temperature, in-cylinder pressure, and the total in-cylinder O2 mass fraction. It is extensively validated with experimental PCCI data from a multi-cylinder engine with almost exclusively stock hardware (stock pistons, injectors/nozzles, turbocharger, etc.) and variable valve actuation. The results show that across a wide range of input conditions the model predicts the start of combustion (SOC) within ±2°CA of the experimental values for all but one of the 119 data points. The experimental SOC ranges from as early as 19.3°CA to as late as +0.6°CA by heavily exercising the control authority over SOC provided by SOIecm, IVC/ECR modulation (ECR ranges from 12:1 to 18:1), and the engine's air-handling system. This PCCI combustion timing model can be coupled with a gas exchange model for control algorithm design. [ABSTRACT FROM PUBLISHER]