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Transition from HCCI to PPC: Investigation of the Effect of Different Injection Timing on Ignition and Combustion Characteristics in an Optical PPC Engine

Lund University-Miao Zhang, Saeed Derafshzan, Leilei Xu, Xue-Song Bai, Mattias Richter, Marcus Lundgren
  • Technical Paper
  • 2020-01-0559
To be published on 2020-04-14 by SAE International in United States
The partially premixed combustion (PPC) concept is regarded as an intermediate process between the thoroughly mixed Homogeneous charge compression ignition (HCCI) combustion and compression ignition (CI) combustion. It’s a combination of auto-ignition mode, a fuel-rich premixed combustion mode, and a diffusion combustion mode. The concept has both high efficiency and low soot emission due to low heat losses and less stratified fuel and air mixtures compared to conventional diesel CI. The mechanisms behind the combustion process are not yet very well known. This work focuses on the efficiency and the in-cylinder process in terms of fuel distribution and the initial phase of the combustion. More specifically, double injection strategies are compared with single injection strategies to achieve different levels of stratification, ranging from HCCI to PPC like combustion as well as poor (43%) to good (49%) of gross indicated efficiency. The experiments were performed in an optical heavy-duty CI engine.To analyze how the efficiency was affected in a transition from HCCI to PPC, the natural luminosity (N.L.) was captured with high-speed video (HSV). To complement…
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Impact of Multiple Injection Strategies on Efficiency and Combustion Characteristics in an Optical PPC Engine

Lund University-Miao Zhang, Leilei Xu, Saeed Derafshzan, Xue-Song Bai, Mattias Richter, Marcus Lundgren
  • Technical Paper
  • 2020-01-1131
To be published on 2020-04-14 by SAE International in United States
Partially premixed combustion (PPC) is a promising way to achieve high thermal efficiency and low emissions, especially by using multiple injection strategies. The mechanisms behind PPC efficiency are still to be explained and explored. In this paper, multiple injections have been used to affect the gross indicated efficiency in an optical PPC engine modified from a Volvo MD13 heavy-duty diesel engine. The aim is both to improve and impair the gross indicated efficiency to understand the differences. The combustion natural luminosity is captured by a high-speed camera, and the distribution of fuel, oxygen, and temperature during the combustion process has been further explored by CFD simulation. The results show that with the right combination of the pilot, main, and post injection the gross indicated efficiency can be improved. Using a post injection in a triple-injection case show to have less effect on the combustion phasing than pilot injection in a double-injection case, while it can significantly affect combustion efficiency. The later of the double-injection cases tested (c30/16), has less heat transfer losses since the high-temperature…