Infrared high-speed thermography of combustion chamber wall impinged by diesel spray flame

Abstract

As a demonstration of a new method to examine the extremely unsteady and spatially varying wall heat transfer phenomena on diesel engine combustion chamber wall, high-speed imaging of infrared thermal radiation from the wall surface impinged by a diesel spray flame was attempted using a high-speed infrared camera. A 35 mm-diameter chromium-coated quartz window surface was impinged by a diesel spray flame with an impinging distance of 27 mm from the nozzle orifice in a constant volume combustion chamber. The infrared thermal radiation from the back surface of the 0.6 µm thick chromium layer was successfully visualized at 10 kHz frame rate and 128 × 128 pixel resolution through the quartz window. The infrared radiation exhibited coherent and streaky structure with radial stripes extending and waving from the stagnation point. The width of the radial stripes, spatial amplitude and the period of the waving movement were comparable to the ones for turbulent heat transfer on the engine cylinder wall previously measured with a heat flux sensor, suggesting that they are resulting from the turbulent structure in the wall-impinging diesel flame. The radiation intensity was calibrated to temperature and converted to heat flux via 3-D numerical analysis of transient thermal conduction in the quartz window. The peak-to-peak variation amplitudes of temperature and heat flux among the radial stripes during the diesel spray flame impingement were about 20 K and 2.3 MW/m2, corresponding to 13% of 150 K maximum temperature swing amplitude and 18 MW/m2 maximum heat flux, respectively.

Influence of spray and combustion processes on piston temperatures and engine heat transfer in a high-output diesel engine

“…These mechanisms are not fully understood, and several recent papers have employed advanced diagnostic techniques to resolve the relationship between heat transfer and the local turbulence in the flow. 10–12 A recent study by Srna parallels the current work in that several different injection schedules were investigated in a diesel engine to understand the effect on local heat flux. 13 The experimental data set included fast-response surface temperature measurements of the cylinder liner with simultaneous optical diagnostics of the jet.…”

Diesel Spray: Development of Spray in Diesel Engine

“…The interaction of wall and spray, mainly taking place in the small-bore high-speed diesel engine, not only has significant effects on mixture formation, but also on the combustion, as well as the emission process in the cylinder. In order to clarify the effect of spray impingement, an analysis of the two-dimensional piston cavity, along with flat wall impinging spray flame, is usually performed in a high pressure and temperature constant-volume engine-like combustion chamber [54][55][56][57][58]. As a basis for evaluation, free spray flame is normally also conducted.…”

“…formed in a high pressure and temperature constant-volume engine-like combustion chamber [54][55][56][57][58]. As a basis for evaluation, free spray flame is normally also conducted.…”

A numerical study of piston bowl geometry and diesel injection timing in a heavy-duty diesel/syngas RCCI engine

“…Combustion chamber characteristics such as bore-to-stroke ratio, compression ratio, and piston bowl geometry are the most important parameters of diesel compression ignition engines because they are directly determining the overall quality of the combustion process and subsequently, the formation and propagation of the flame front. 18 Therefore, optimization of these parameters has attracted the attention of many researchers and design engineers. Choosing an optimal operating point for combustion chamber parameters can reduce harmful engine-out emissions like HC , CO , and PM , and improve fuel economy.The outcomes of vast studies devoted to combustion chamber modifications have shown great potential to achieve low emissions and high performance at the same time.…”