Compression Ratio Influence on Maximum Load of a Natural Gas Fueled HCCI Engine

This paper discusses the compression ratio influence on maximum load of a Natural Gas HCCI engine. A modified Volvo TD100 truck engine is controlled in a closed-loop fashion by enriching the Natural Gas mixture with Hydrogen. The first section of the paper illustrates and discusses the potential of using hydrogen enrichment of natural gas to control combustion timing. Cylinder pressure is used as the feedback and the 50 percent burn angle is the controlled parameter. Full-cycle simulation is compared to some of the experimental data and then used to enhance some of the experimental observations dealing with ignition timing, thermal boundary conditions, emissions and how they affect engine stability and performance. High load issues common to HCCI are discussed in light of the inherent performance and emissions tradeoff and the disappearance of feasible operating space at high engine loads. The problems of tighter limits for combustion timing, unstable operational points and physical constraints at high loads are discussed and illustrated by experimental results. Finally, the influence on operational limits, i.e., emissions peak pressure rise and peak cylinder pressure, from compression ratio at high load are discussed

Understanding the dynamic evolution of cyclic variability at the operating limits of HCCI engines with negative valve overlap.

ABSTRACT An experimental study is performed for homogeneous charge compression ignition (HCCI) combustion focusing on late phasing conditions with high cyclic variability (CV) approaching misfire. High CV limits the feasible operating range and the objective is to understand and quantify the dominating effects of the CV in order to enable controls for widening the operating range of HCCI. A combustion analysis method is developed for explaining the dynamic coupling in sequences of combustion cycles where important variables are residual gas temperature, combustion efficiency, heat release during re-compression, and unburned fuel mass. The results show that the unburned fuel mass carries over to the re-compression and to the next cycle creating a coupling between cycles, in addition to the well known temperature coupling, that is essential for understanding and predicting the HCCI behavior at lean conditions with high CV

A strategic analysis of the advanced ceramics industry for heat engine applications

Thesis: M.S., Massachusetts Institute of Technology, Sloan School of Management, 1986Bibliography: leaves 81-85.by Dionissios Nilolaou Assanis.M.S.M.S. Massachusetts Institute of Technology, Sloan School of Managemen

A computer simulation of the turbocharged turocompounded diesel engine system for studies of low heat rejection engine performance

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1986.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.Bibliography: leaves 135-140.by Dionissios Nikolaou Assanis.Ph.D

Mixture Preparation and Nitric Oxide Formation in a GDI Engine studied by Combined Laser Diagnostics and Numerical Modeling

Through the combination of advanced imaging laser diagnostics with multi-dimensional computer models, a new understanding of the performance of direct-injection gasoline engines is pursuit. The work focuses on the fuel injection process, the breakup of the liquid into a fine spray and the mixing of the fuel with the in-cylinder gases. Non-intrusive laser diagnostics will be used to measure the spatial distribution of droplets and vaporized fuel with very high temporal resolution. These data along with temperature measurements will be used to validate a new spray breakup model for gasoline direct-injection. Experimental data on near wall fuel distributions will be used for comparison with a model that predicts the spray-wall interaction and the dynamics of the liquid film on the surface. Quantitative measurements of local nitric oxide concentrations inside the combustion chamber will provide a critical test for a numerical simulation of the nitric oxide formation process. This model is based on a modified flamelet approach and will be used to study the effects of exhaust gas recirculation