Enhancement of Stratified Charge for DISI Engines through Split Injection(Effect and Its Mechanism)

Li, Tie; Nishida, Keiya; Zhang, Yuyin; Onoe, Tuyoshi; Hiroyau, Hiroyuki

doi:10.1299/jsmeb.48.687

Cited by 22 publications

(4 citation statements)

References 7 publications

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“…Such findings are not uncommon and indeed other studies of split injections for DISI engines have also reported improved air entrainment, mixing and evaporation [28]. Spray-gas momentum transfer is considered critical for defining spray structure and driving the efficiency of mixture preparation process.…”

Section: °C 90 °Cmentioning

confidence: 85%

Mixture Preparation and Combustion Variability in a Spray-Guided DISI Engine

Serras-Pereira¹,

Aleiferis²,

Richardson

et al. 2007

SAE Technical Paper Series

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In an attempt to study the numerous contributors towards cyclic variations in combustion in a direct injection spark ignition engine, simultaneous high-speed imaging of fuel injection and flame growth are undertaken on a crankangle resolved basis in a single-cylinder optical research engine. Batches of images from 100 consecutive cycles are acquired for all conditions with synchronised incylinder pressure logging. The engine is motored and fired at stoichiometric conditions at 1500 RPM under part-load and wide-open-throttle conditions (0.5-1.0 bar intake pressure), with injection timing set early in the intake stroke to promote homogeneous mixture formation with a centrally mounted multi-hole injector. Liquid impingement is observed on the cylinder walls and on the piston crown with early intake injection and multiple injection strategies are employed in an attempt to reduce impingement and alter mixture preparation and subsequent combustion. The effects are investigated for iso-octane and pump-grade gasoline at engine coolant temperatures of 50 and 90 °C. Gasoline sprays showed severe deformation and partial collapse of the individual spray plumes at 90 °C, leading to a different mixture formation process relative to iso-octane, which showed no such effects at this engine temperature. Using multiple fuel injections per cycle, but maintaining the same overall air-to-fuel ratio with single-injection strategies, a significant reduction in direct impingement on the walls was observed, together with different flame growth relative to single injection. These results suggest that injection strategy and type of fuel is playing an important role in the mixture preparation process, even for homogeneous early direct injection, and that different types of multiple-injection strategies alone have the potential to modify significantly in-cylinder phenomena, affect combustion and potentially exhaust emissions.

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Section: °C 90 °Cmentioning

confidence: 85%

Mixture Preparation and Combustion Variability in a Spray-Guided DISI Engine

Serras-Pereira¹,

Aleiferis²,

Richardson

et al. 2007

SAE Technical Paper Series

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“…Stable and smooth combustion without knocking could be possible with optimized proportions of the two-stage injection, while soot was not detected. The evaporation of the second amount of injected fuel is promoted by the ambient air motion in the tail region of first fuel spray [14,15].…”

Section: Introductionmentioning

confidence: 99%

Effect of a split-injection strategy on the performance of stratified lean combustion for a gasoline direct-injection engine

Park

Kim

et al. 2011

Proceedings of the Institution of Mechanical Engineers, Part D:

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Fuel economy can be significantly improved in a gasoline direct-injection (GDI) engine owing to the stratified mixture formation strategy which guarantees stable combustion under ultra-lean air–fuel mixture conditions. In the GDI engine, it is widely accepted that the spray-guided direct-injection system, which is characterized by a close configuration between the centrally mounted injector and the spark plug, is regarded as a promising technology among the efforts to realize stratified lean combustion. With this configuration, the split injection can be an effective fuel injection scheme because of its potential to modulate the spray characteristics as well as to create a combustible mixture in the proximity of the spark plug. In this study, the split-injection strategy was assessed as a way to achieve ultra-lean operation in a GDI engine and the resulting lean-combustion characteristics were investigated in terms of the engine performance and emissions. The engine was tested at constant operating conditions (an engine speed of 3000 r/min and an indicated mean effective pressure of 0.4 MPa) with a change in the fuel injection pressure ranging from 10 MPa to 20 MPa. The excess air ratio λ varied from stoichiometry to the lean flammability limit, which turned out to be extended in the GDI approach. The engine test results show that the split injection of fuel allowed the formation of an adequately stratified mixture in lean-combustion conditions, and thus stable combustion was guaranteed. These results indicate that an excess air ratio was one of the important factors affecting the thermal efficiency and nitrogen oxide (NO x) emissions and was significantly extended to λ = 2.0 by the split-injection scheme. In addition, several fuel injection parameters such as the injection quantity, the split ratio, and the number of splits were examined with an emphasis on their impact on the fuel economy and emissions. The results demonstrate that there exists a trade-off between the NO x reduction and the efficiency, and therefore it is required to choose an appropriate injection strategy depending on the engine operating conditions in order to satisfy emission regulations.

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“…Studies of split injections with multi-hole injectors for DISI engines have reported improved air entrainment, mixing and evaporation under late injection strategies for stratified operation, e.g. [14,15]. It needs to be noted though that the main characteristic of multi-hole injectors is that they produce very robust spray plumes consisting of individual vapour branches rather than forming a complex cloud structure.…”

Section: Split-injection Strategies For Spark-ignition Enginesmentioning

confidence: 99%

Imaging and heat flux measurements of wall impinging sprays of hydrocarbons and alcohols in a direct-injection spark-ignition engine

Serras-Pereira

Aleiferis

Richardson

2012

Fuel

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The latest generation of fuel systems for direct-injection spark-ignition engines uses injection nozzles that accommodate a number of holes with various angles in order to offer flexibility in in-cylinder fuel targeting over a range of engine operating conditions. However, the high-injection pressures that are needed for efficient fuel atomisation can lead to deteriorating effects with regards to engine exhaust emissions (e.g. unburned hydrocarbons and particulates) from liquid fuel impingement onto the piston and liner walls. Eliminating such deteriorating effects requires fundamental understanding of in-cylinder spray development processes, taking also into account the diversity of future commercial fuels that can contain significant quantities of bio-components with very different chemical and physical properties to those of typical liquid hydrocarbons. This paper presents high-speed imaging results of spray impingement onto the liner of a direct-injection spark-ignition engine, as well as crank-angle resolved wall heat flux measurements at the observed locations of fuel impingement for detailed characterisation of levels and timing of impingement. The tests were performed in a running engine at 1500 RPM primarily at low load (0.5 bar intake pressure) using 20, 50 and 90 °C engine temperatures. Gasoline, iso-Octane, Butanol, Ethanol and a blend of 10% Ethanol with 90% Gasoline (E10) were used to encompass a range of current and future fuel components for spark-ignition engines. The collected data were analysed to extract mean and standard deviation statistics of spray images and heat flux signals. The results were also interpreted with reference to physical properties and evaporation rates predicted by a single droplet model for all fuels tested.3

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Enhancement of Stratified Charge for DISI Engines through Split Injection(Effect and Its Mechanism)

Cited by 22 publications

References 7 publications

Mixture Preparation and Combustion Variability in a Spray-Guided DISI Engine

Mixture Preparation and Combustion Variability in a Spray-Guided DISI Engine

Effect of a split-injection strategy on the performance of stratified lean combustion for a gasoline direct-injection engine

Imaging and heat flux measurements of wall impinging sprays of hydrocarbons and alcohols in a direct-injection spark-ignition engine

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