Formation of polycyclic aromatic hydrocarbons and their growth to soot—a review of chemical reaction pathways

Formation mechanisms of aromatic compounds in aliphatic flames

While the Carnot cycle is the basic idealized thermodynamic cycle for energy transfer, it is generally impractical and uneconomical to implement. Although less thermodynamically efficient than the Carnot cycle, the Rankine cycle (and heat engines based upon it) is practical and adaptable. Typically, water is used as the working fluid in this cycle. A difficulty that arises with the use of water is the need to superheat the water to prevent turbine blade erosion. Organic working fluids, on the other hand, can be used at lower temperatures and do not require superheating. This results in a practical increase in efficiency over the use of the cycle with water as the working fluid. In these organic Rankine cycle (ORC) applications, the choice of working fluid is critical since the fluid must have not only thermophysical properties that match the application but also adequate chemical stability at the desired working temperature. In this paper, we present the application of simple and relatively rapid ampule t...

Rapid Screening of Fluids for Chemical Stability in Organic Rankine Cycle Applications

Diesel soot, one of the major environmental pollutants, is the finer particle produced during the high temperature pyrolysis or combustion of diesel fuel. Advances in the understanding of soot formation in diesel combustion systems during the recent decades are surveyed in this paper. It is universally accepted that soot formation steps can be summarized as (1) formation of molecular precursors of soot, (2) nucleation or inception of particles from heavy polycyclic aromatic hydrocarbon molecules, (3) mass growth of particles by addition of gas phase molecules, (4) coagulation via reactive particle-particle collisions, (5) carbonization of particulate material, and, finally, (6) oxidation of polycyclic aromatic hydrocarbons and soot particles. Several mathematical models of diesel soot formation available in the related literature are offered in this review, which are Hiroyasu's model, Moss' model, Tesner's model, Lindstedt's model, and detailed soot formation models. Experimental and numerical studies currently play an important role in exploring the diesel soot formation mechanism. The success of such studies relies on the development of both diagnostic techniques to increase the quality of experiments and mathematical models for numerical simulations.

Ernest Noel Hague

Papers

LVI.—The mechanism of thermal decomposition of the normal paraffins