In-Cylinder Measurement of Particulate Radiant Heat Transfer in a Direct Injection Diesel Engine

A method of determining the total hemispherical in-cylinder radiant heat transfer of a direct injection diesel engine was developed using the Two Color theory. A radiant probe was installed in the head of a single cylinder test engine version of a Cummins N14 diesel engine to facilitate the optical measurement. Two probes, installed one at a time, were used to provide the data to calculate the hemispherical radiant heat flux. Each of the probes had a different field of view but both had a near-hemispherical field of view and used a window material that exhibits a cosine-normalized response. The radiant probes were designed to be self-cleaning and remained free of soot deposits during engine operation at high load.

The test engine was operated at 1200 and 1500 RPM and at 50, 75, and 100% load for each engine speed. At each operating combination of engine speed and load, measurements were made at several injection timings.

Peak radiant heat flux values of 2.0 MW/m² were measured at high load. The radiant heat flux curves exhibited a characteristic shape with subtle variations at different operating conditions. A general trend was found for the time integrated radiant heat flux across all operation conditions. The value of time integrated heat flux was proportional the product of engine load, equivalence ratio, fuel flow and the percentage of energy release in the diffusion burn phase.