Diesel Flame Studies in an Optical Engine
2004 (English)Conference paper (Refereed)
A diesel engine with optical access through an extended piston has been developed. It is based on a heavy duty truck engine and the purpose is to generate calibration data for computer simulation of spray combustion, hereby facilitating reliable combustion prediction using Computational Fluid Dynamics (CFD). Conventional photography using a solid-state camera was adopted to image the combustion. As the upper surface of the glass window in the piston is flat, the compression ratio of the engine is reduced to 12:1, in order to avoid that the spray plumes hit the glass surface. To compensate for the lowered compression ratio, the inlet pressure as well as the inlet temperature were increased. As top dead center conditions regarding gas density and temperature are desired to be maintained, this approach results in an increased overall air-to-fuel ratio. Additionally, the cylinder pressure decay due to the piston movement becomes slower than it should be at the present engine speed. However, despite these drawbacks, the engine allows for spray combustion studies under realistic diesel engine conditions regarding pressure and temperature. In the preliminary study the inlet pressure was 400 kPa absolute and the temperature was 450 K, resulting in a compression pressure of about 8.6 MPa at top dead center when the engine runs at 1200 rpm. To predict the air mass in the cylinder as accurately as possible, the exhaust back pressure is always kept equal to the inlet pressure. To minimize the thermal load on the piston, fuel is injected only during cycles when an image is exposed. This is also beneficial when estimating the air mass in the cylinder, as the temperature of the rest gas from the preceding cycle is quite low. In the preliminary study a nozzle with eight orifices fitted to a common-rail injector was used to generate the sprays. The orifice diameter was 190 µm. The rail pressure was 160 MPa and the injected amount of fuel was 80 mg. The resulting combustion was dominated by diffusion flames.
Place, publisher, year, edition, pages
IdentifiersURN: urn:nbn:se:kth:diva-181482OAI: oai:DiVA.org:kth-181482DiVA: diva2:899532
Seminar on "Optisches Indizieren", Haus der Technik, Munich, December 7, 2004.
QC 201602242016-02-022016-02-022016-02-24Bibliographically approved