Investigation of Combustion-Chamber Deposit Thermal Behavior Utilizing Optical RadiationMeasurements in a Fired Engine

Abstract

An infrared radiometer, which incorporated three optical paths and operated between 3.5-4.0 I'm, was used to obtain transient surface temperatures in a fired engine. An integrated form of the equation of radiative transfer was applied to each optical path allowing gas emission, gas absorption and deposit surface radiation within the combustion-chamber to be characterized during a single cycle. Measurements of a simulated deposit were made at various temperatures and spark advance with the engine fired on methane and again on gasoline. Radiative characteristics of the combustion gases such as absorption and emission were investigated at several different operating conditions. A maximum error of 6% was found for temperature measurements between 660 and 900 Kelvins.Using a fast surface thermocouple with its junction located at the inner surface of the combustionchamber wall, two combustion-chamber deposits were accumulated for different lengths of time. Deposit surface and interface temperatures were investigated at several different operating conditions for each deposit. Utilizing the experimentally obtained deposit surface and interface temperatures, deposit thermal conductivity (k) and heat capacity (Qc) were determined via a computational model which treated k as a function of temperature. Values obtained for k and oc were well within the range of those reported for various forms of graphite.

Analytical and Experimental Investigation of Temperature-Swing Insulation on Engine Performance

“…This consideration is necessary especially in materials that contain low volumetric heat capacity which would allow fast changes in temperature, and low thermal conductivity which would enable a reduction in overall heat transfer and an increase in surface temperature during combustion and expansion. In both analytical (Wallace, Way, & Vollmert, 1979) (Morel, Fort, & Blumberg, 1985) (Anderson & Prakash, 1985) (Kosaka, et al, 2013) and experimental (Furuhama & Enomoto, 1987) (Harder & Anderson, 1988) (Aoki, et al, 2015) studies, a non-negligible swing in surface temperature throughout the engine cycle was observed with increasing insulation. This poses unique possibilities and challenges over the concept of a steady, elevated temperature and was fundamentally different from the net-zero heat transfer model with respect to the processes occurring in-cylinder.…”