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Low Speed Pre-Ignition (LSPI), also referred to as superknock or mega-knock is an undesirable turbocharged engine combustion phenomenon limiting fuel economy, drivability, emissions and durability performance. Numerous researchers have previously reported that the frequency of Superknock is sensitive to engine oil and fuel composition as well as engine conditions in controlled laboratory and engine-based studies. Recent studies by Toyota and Tsinghua University have demonstrated that controlled induction of particles into the combustion chamber can induce pre-ignition and superknock. Afton and Tsinghua recently developed a multi-physics approach which was able to realistically model all of the elementary processes known to be involved in deposit induced pre-ignition. The approach was able to successfully simulate deposit induced pre-ignition at conditions where the phenomenon has been experimentally observed.

Gasoline direct-injection (GDI) engines have a well-known propensity to form intake valve deposits (IVD), regardless of operator service, engine architecture, or cylinder configuration. Due to the lack of a fuel-washing process that is typical of Port Fuel Injected (PFI) engines, the deposits steadily accumulate over time and can lead to deterioration in combustion, unstable operation, valve-sticking, or engine failure. Vehicles using these engines are often forced to undergo expensive maintenance to mechanically remove the deposits, which eventually re-form. The deposit formation process has not been well-characterized and there is no standardized engine test to study the impact of fuel or lubricant formulation variables. To meet this need, a proprietary vehicle-based GDI-IVD test that is both repeatable and responsive to chemistry has been developed.

Catalyzed gasoline particulate filter (cGPF) is the prime technology to meet future stringent regulations for particulates from gasoline direct injection (GDI) engines. One of the technical concerns is the ultimate durability of cGPF in regards to engine lubricant formulations. This study investigated two tailored lubricant formulations on catalyzed GPFs which were aged on engine followed by emission testing on vehicle. An engine accelerated aging protocol was developed for cGPFs to simulate thermal aging, ash and soot loading that is at least equivalent to 200,000 km durability requirement. Evaluations include tailpipe emission levels, backpressure, catalytic performance, and post-mortem analysis. Both formulations have demonstrated a high level of cGPF performance retention; performance being assessed in terms of emission level at the end of durability demonstration testing. These formulations provide flexibility in selecting robust lubricant to meet various system requirements.

In this paper, the impacts of Aromatic and Olefin on the formation of poly-aromatic hydrocarbons (PAHs) in the gasoline direct injection (GDI) engine were experimentally and numerically investigated. The objective of this study is to describe the formation process of the soot precursors including one ring to four ring aromatics (A1-A4). In order to better understand the effects of the fuel properties on the formations of PAHs. Three types of fuels, namely base gasoline, gasoline with higher aromatics content, and gasoline with higher olefin content were experimentally studied. At the same time, these aspects were also numerically investigated in the CHEMKIN code by using premixed laminar flame model and surrogated fuels. The results show that higher aromatics content in gasoline will lead to much higher PAHs formation. Similar trend was also found in the gasoline with higher olefin content.

High boost and direct injection are effective ways for energy saving in gasoline engines. However, the occurrence of super-knock at high load has become a main obstacle for further improving power density and fuel economy. It has been known that super-knock can be induced by pre-ignition, and oil droplet auto-ignition is found to be one of the possible mechanisms. In this study, experiments were conducted in a single-cylinder thermal research engine (TRE), in which different types of oil and surrogates were directly injected into the cylinder and then led to pre-ignition and super-knock. The effect of oil injection timing, oil injection quantity, different gasoline and different oil were tested. All the oil in this work could induce pre-ignition, even though their combustion phasing was much later than that in the case of n-hexadecane.

Gasoline particulate filter (GPF) is considered a suitable solution to meet the increasingly stringent particle number (PN) regulations for both gasoline direct injection (GDI) and multi-port fuel injection (MPI) engines. Generally, GDI engines emit more particulate matter (PM) and PN. In recent years, GDI engines have gained significant market penetration in the automobile industry owing to better fuel economy and drivability. In this study, an accelerated ash loading method was tested by doping lubricating oil into the fuel for a GDI engine. Emission tests were performed at different ash loads with different driving cycles and GPF combinations. The results showed that the GPF could significantly reduce particle emissions to meet the China 6 regulation. With further ash loading, the filtration efficiency increased above 99% and the effects on fuel consumption and backpressure were found to be limited, even with an ash loading of up to 50 g/l.

Because of the increased use of gasoline direct engine (GDI) in the automobile industry, there is a significant need to control particulates from GDI engines based on emission regulations. One potential technical approach is the utilization of a gasoline particulate filter (GPF). The successful adoption of this emission control technology needs to take many aspects into consideration and requires a system approach for optimization. This study conducted research to investigate the impact of vehicle driving cycles, fuel properties and catalyst coating on the performance of GPF. It was found that driving cycle has significant impact on particulate emission. Fuel quality still plays a role in particulate emissions, and can affect the GPF performance. Catalyzed GPF is preferred for soot regeneration, especially for the case that the vehicle operation is dominated by congested city driving condition, i.e. low operating temperatures. The details of the study are presented in the paper.