In-cylinder soot radiation heat transfer in direct-injection diesel engines

Abstract

HIGHLIGHTSOptoelectronic pyrometer provides similar results compared with a conventional method Lower injection pressure results in higher radiation Higher ambient temperature and higher in-cylinder gas density produce higher radiation Larger lift-off length reduces the soot volume fraction and the spectral intensity An increase on swirl number, load and CA50 provide a lower total radiation Lower values of EGR implies a decreased on radiation intensity KEYWORDSSoot; in-cylinder heat transfer; radiation; Optical pyrometer; ABSTRACTThe efficiency and CO 2 are one of the main concerns of automotive manufacturers.There are several strategies under investigation to solve this problem. In the present work, the research effort has been focused on improving knowledge of in-cylinder heat transfer and its impact on engine efficiency. In particular, soot radiation was studied since it can be considered a significant source of the efficiency losses in modern diesel engines. Considering previous studies, the portion of total chemical energy released during combustion lost due to radiation heat transfer varies widely from 0.5 up to 10%, depending on engine parameters and combustion process. Thus, the main objective of this work was to evaluate the amount of energy lost to soot radiation relative to the input fuel chemical energy during the combustion event under different operating conditions in a completely controlled environment provided by an optical engine. Under these simplified conditions, two-color method was applied by using high speed imaging pyrometer with cameras (two dimensional results) and optoelectronic pyrometer (zero dimensional results). Once a detailed comparison between both diagnostics was performed, optoelectronic pyrometer was used to characterize radiant energy losses in a fully instrumented 4-cylinder direct-injection light-duty diesel engine. In particular swirl ratio, EGR and combustion phasing effects on radiation heat transfer were evaluated.

Ion-Induced Soot Nucleation Using a New Potential for Curved Aromatics

“…Incomplete combustion produces carbonaceous particulate matter, known as soot, that negatively impacts combustion devices, human health and the environment (Benajes et al, 2015;Highwood and Kinnersley, 2006). The formation of soot particles is a complex chemical and physical process that involves gas phase chemistry of reactive precursor species and subsequent particle processes.…”

Understanding the ignition mechanism of high-pressure spray flames

“…Because soot radiates strongly at high temperatures, its formation is often desirable under conditions, e.g., in furnaces and boilers, in which high radiative-heat transfer is necessary [1,2]. Conversely, its formation is undesirable when high radiative-heat transfer is a problem, such as in the control and extinction of medium-to largescale pool, urban, and forest fires [3,4] and in efforts to increase efficiency and reduce heat loss in engines [5]. Soot formation also poses threats to human health [6][7][8][9], air quality [10], and global and regional climate [10][11][12] when released into the atmosphere.…”

A Combination of Swirl Ratio and Injection Strategy to Increase Engine Efficiency

“…CO2 emissions, as the main contributor to greenhouse effect, can be mitigated by diminishing fuel consumption. Thus, currently, different strategies are proposed to get this goal; thermal management improvement [2,3], indicated cycle optimization [4,5], in-cylinder heat transfer (HT) reduction [6,7,8], engine friction and auxiliaries losses reduction [9,10] or new combustion modes [11,12,13] among others. In the present work, the research effort has been focused on obtaining an engine setting combination, which leads to a heat transfer reduction with a combustion process improvement and therefore a better engine thermal efficiency.…”