Heat Release Rate of Two-Stage Injection Diesel Engine
Kouji IWAZAKI* Goro OGIWARA** and Masataka ARAI**
This research work focused on the effects of injection pattern on combustion characteristics and performances of diesel engines. Injection patterns used in this study were single-stage and two-stage injections. Both of direct injection (DI) diesel engine and swirl chamber type indirect injection (IDI) diesel engine were used to analyze the effect of injection pattern on heat release rate. As a result, ignition delay period of IDI diesel engine with two-stage injection became shorter than that of DI diesel engine with same injection system. The maximum value of heat release rate was suppressed by the two-stage injection. Exhaust emission and fuel consumption of IDI diesel engine with two-stage injection were improved when the first stage injection timing was early and amount of fuel in the first stage injection was small. However, smoke and fuel consumption of DI diesel engine become worse, but NO emission was improved by the two-stage injection when the first injection timing was early.
Key Words: Internal Combustion Engine, Diesel Engine, Combustion, Exhaust Emission, Two-Stage Injection
Various efforts to develop the new combustion system for improving engine performances have been carried out. For example, premixed lean mixture combustion of DI diesel engine has been recently proposed . Fuel for premixed lean mixture combustion was injected at very early timing in a compression process. NO emission from DI diesel engine was greatly reduced by premixed lean combustion. However in this combustion process, there were some problems such as increases in HC and CO emissions , and high fuel consumption. Also, the operating region was limited in partial toad conditions because of premixed lean combustion.
The operating region of the above engine could be expanded to higher load conditions by a two-stage injection system , in which fuel of the first stage injection corresponded to the premixed lean mixture combustion. NO and Smoke emissions on a high load condition were reduced by two-stage injection .
Ignition delay and diffusion combustion in IDI diesel engine were controlled by swirl chamber geometry . Fuel-air mixing in the swirl chamber was more promoted than fuel-air mixing in DI diesel engine . However, only a few research studies for IDI diesel engine with early stage injection or two-stage injection were found in the published literatures.
This paper presents an experimental study of the effects of early stage injection and two-stage injection on diesel engines of IDI and DI types.
2. EXPERIMENTAL APPARATUS AND TEST CONDITIONS
The experimental apparatus is shown in Fig.1. The test engine had two injection pumps, and two-stage injection was achieved by these two pumps. Injection lines from the pumps were connected through CP valves. It was connected with one injection nozzle. Injection timings of both injection pumps could be widely controlled. Cylinder and line pressure indicators were equipped on the cylinder head and injection nozzle. Heat release rate was calculated from cylinder pressure. However, cylinder pressure of the IDI diesel engine was measured only at the main combustion chamber.
* Graduate Student of Gunma University
1-5-1 Tenjin-cho Kiryu Gunma 376-8515 JAPAN
** Gunma University
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