Fuel injector deposits in direct-injection spark-ignition engines

Abstract

Controlling fuel injector deposits is recognised as a challenge for advanced direct-injection sparkignition (DISI) engines. This paper gives a comprehensive overview of the research on formation, measurement, effect, and mitigation of injector deposits in DISI engines. Methodologies for the injector deposit studies include visual and compositional analysis. It is shown that injector deposits will reduce injector fuel flow rates, and lead to changes in spray characteristics. Consequently, spray angle and envelope are likely to be affected, and spray penetration distance as well as droplet diameter can be increased. Injector deposits are revealed to be primarily fuel-derived and created by two distinct free radical pathways, i.e., low temperature auto-oxidation and high temperature pyrolysis. Fuel compositions (olefins, aromatics, and sulphur), as well as T90 parameter, are significant factors in injector deposit formation. The worst consequences of injector fouling are pre-ignition, and engine misfiring and malfunction. Emissions, especially particulates, dramatically increase as the fuel injector becomes fouled. It appears that fuel detergent is the most effective method in controlling injector deposit formation if its chemistry and dosage rate are optimized. Outward opening piezo-driven injector configuration with a good surface finish, a sharp nozzle inlet, and a counter bore design, is useful in preventing injector deposit formation. Reducing injector nozzle temperature by methods such as designing special injector cooling passages, and improving engine design are also proven to be 2 helpful in reducing injector fouling. Anti-deposit coatings only delay the onset of injector deposit formation.

Injector Fouling and Its Impact on Engine Emissions and Spray Characteristics in Gasoline Direct Injection Engines

“…This is usually referred to as injector fouling or coking and can have an adverse effect on fuel consumption, engine performance and both hydrocarbons and particulate emissions. Formation of deposits on the injector tip can result in alteration of spray pattern leading to increased spray impingement and therefore increased particulate emissions [13,14,15,16].The phenomenon of injector fouling and how it is influenced by fuel and engine parameters was the focus of a number of studies. Aradi et al [17] investigated different fuel blends under several conditions in a four cylinder engine.…”

“…This is usually referred to as injector fouling or coking and can have an adverse effect on fuel consumption, engine performance and both hydrocarbons and particulate emissions. Formation of deposits on the injector tip can result in alteration of spray pattern leading to increased spray impingement and therefore increased particulate emissions [13,14,15,16].…”

Sulfate Salts in Gasoline and Ethanol Fuels -- Historical Perspective and Analysis of Available Data

“…Higher olefin and aromatic content increase the quantity of deposits, and a higher T90 has a similar but smaller effect (Carlisle et al 2001). The temperature of the injector tip is also believed to affect the amount of deposits, with cooler temperatures leading to fewer deposits (Xu et al 2015).…”

Recent Progress in Automotive Gasoline Direct Injection Engine Technology

“…A review by Xu et al [130] in 2015 summarized the existing literatures on GDI injector deposits, including the formation mechanism and factors affecting deposits, their effects on engine performance and emissions and approaches to mitigating deposits. However, due to increasing concerns regarding PN emissions, many additional studies have been carried out recently.…”