Modeling of Compression Ignition Engines for Advanced Engine Operation and Alternative Fuels by the Second Law of Thermodynamics

Abstract

With the advent of modern engine control strategies, and particularly electronic common-rail injection, the scope and scale of what is achievable and controllable in compression-ignition engines has exploded quite rapidly in recent years. The potential marriage of electronically-controlled and multi-point fuel injection, dual fuel combustion, variable exhaust gas recirculation, exhaust waste heat recovery, low-temperature combustion, and the immense variety of potential liquid and gaseous fuels available means that the older understanding of compression ignition engine combustion is incomplete and inadequate to explain, predict, control, and optimize more novel engine combustion and operational regimes. This mandates that new models, both diagnostic and theoretical, be developed to explore engine combustion and pick apart the various phenomena that result, and includes revisiting models that previously have been sidelined for a lack of usefulness. To that end, this work details the construction, validation, and usage of a diagnostic heat release model focused on the application of the 2nd Law of Thermodynamics and the phenomena associated with entropy generation and availability destruction from the accumulated test data of numerous fuels and engine operational modes. A critical aspect of this research includes the marriage of this model with a suite of emissions analysis technologies, allowing for a complete characterization of engine-out regulated and unregulated emissions species, as well as a thoroughly instrumented and highly modified single-cylinder compression-ignition engine. This combined test apparatus for novel fuels and engine operational modes, in combination with the models described herein, serve as a means to collect and dissect engine performance, in-cylinder pressure, engine knock and noise, emissions, heat release, and availability release and consumption, and the interrelationships between these characteristics The experimental results of this work showcase both the direct usage of the 2nd Law Analysis (both alongside and separate from the more traditional 1st Law Heat Release Analysis), and also the potential usage of this model for the exploration of engine operational modes. In particular, the 2nd Law analysis appears to be of immense importance to the exploration of low temperature combustion regimes, as well as the usage of exhaust waste heat recovery systems.