A Study of the Characteristics of Mixture Formation and Combustion in a PCCI Engine Using an Early Multiple Injection Strategy

Abstract

As world attention has focused on global warming and air pollution, high-efficiency diesel engines with low CO 2 emissions have become more attractive. Premixed diesel engines in particular have the potential to achieve a more homogeneous mixture in the cylinder which results in lower NO x and soot emission. It is well-known that the injection strategies such as the injection timing and the spray included angle are important to create the optimal mixture formation for a PCCI (premixed charge compression ignition) engine. In this research, we investigated the effect of injection angle, injection timing, and frequency on the combustion and mixture formation in a direct injection type PCCI engine using an early multiple injection strategy. The experimental results showed that the mixture formation, IMEP, and emission characteristics in the PCCI engine were dominantly affected by the fuel injection timing and spray included angle. In particular, the injection timing of 65°BTDC with the spray included angle of 100°effectively reduced the smoke emission in the early single injection case. In other words, the smoke number was less than 1 FSN when the IMEP exceeded 3.5 bar. The multiple injection method also resulted in more homogeneous mixture formation due to decrease in spray penetration and increase in the total amount of fuel evaporation in the combustion bowl. In addition, a simulation was conducted in order to estimate the mixture distribution within the cylinder according to injection conditions such as spray included angle and injection timing. The simulation result is very effective to clarify the air fuel distribution of a PCCI combustion.

Guidelines for Improving Diesel Engine Characteristics

“…Multiple fuel injections along with high fuel injection pressures represent an effective way of diesel engine combustion improvements (Kim et al 2008;Wang et al 2009). These are the main reasons for the development of electronically controlled high pressure fuel injection systems like the common rail system shown in Fig.…”

Investigation of Cluster-Nozzle Concepts for Direct Injection Diesel Engines

“…If higher amounts of fuel are injected, the start of injection has to be advanced to earlier times in order to separate the ignition and evaporation process but is limited by the nozzle design. Fuel-wetting on the liner due to spray-wall interactions has to be avoided by applying a narrow spray angle as proposed and studied in [74,75]. The narrow spray angle limits the system only to early injection events and is not suitable to conventional combustion mode at high loads.…”

“…The narrow spray angle limits the system only to early injection events and is not suitable to conventional combustion mode at high loads. The additional use of EGR is another way to shorten the spray penetration, as observed in [75] and in [76] where moderately narrow spray angles are investigated, to prevent the fuel-wetting of the liner.…”

A Review of the Utilisation of Natural Gas with High Carbon Dioxide Content as Automotive Fuel in an Indirect Injection Diesel Engine

“…These include homogeneous charge compression ignition (HCCI) [8]- [10], premixed charge compression ignition (PCCI) [5], [11], [12], partially premixed charge compression ignition (PPCI) engines [13] and EGR [14], [15]. HCCI and PCCI engines demonstrate pronounced capabilities in terms of simultaneous ultra-low NOx and PM emissions.…”