Spray stability of outwards opening pintle injectors for stratified direct injection spark ignition engine operation

Marchi, Andrea; Nouri, J. M.; Yan, Youyou; Arcoumanis, C.

doi:10.1243/14680874jer605

Cited by 39 publications

(22 citation statements)

References 13 publications

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“…Two injections of fuel results in a lower effective injector orifice area compared to a single fuel injection with the effective area decreasing with an increasing number of injections. Marchi et al [43] found that a lower needle lift reduced the hollow cone fuel spray penetration length for both homogenous and stratified injection timings in an optical engine. A lower effective needle lift and injector orifice area is expected to result in a reduced fuel spray penetration length and a decrease in the piston crown fuel film mass based on these results.…”

Section: Imagingmentioning

confidence: 99%

In cylinder visualization of stratified combustion of E85 and main sources of soot formation

Johansen

Hemdal

2015

Fuel

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The combustion process and soot formation in spark ignited spray guided stratified combustion of E85 was investigated in a single cylinder optical engine with direct injection of fuel using an outward opening piezo actuated injector. The effect of engine rotation frequency, fuel quantity, injection sequence and ignition timing was studied. Combustion, soot formation and soot oxidation was analysed using cylinder pressure measurements, images recorded using high speed video cameras, the flame emission spectrum and OH * chemiluminescence and soot incandescence imaging. A maximum injection duration was found to exist for direct ignition of the fuel spray. Engine rotation frequency had little effect on the initial and maximum rate of combustion. The maximum rate of combustion decreased with increasing cycle fuel mass when a single injection was used. The rate of combustion and indicated mean effective pressure increased and the combustion variability decreased when the single injection was split into multiple injections in close succession to deliver the same total fuel mass and the last fuel spray was ignited. Ignition of the first fuel spray resulted in a more pronounced change. The absence of soot incandescence during the initial flame propagation suggested flame propagation in a partially mixed fuel and air mixture with stoichiometric to fuel lean regions. A single fuel injection resulted in piston pool fires due to fuel spray impingement on the piston and was the primary source of soot formation. The pool fires persisted until after conditions favourable to oxidation of the soot had ended. Soot formation in the gas phase occurred while favourable soot oxidation conditions existed and was efficiently oxidized. The magnitude of the piston pool fires was reduced using multiple injections. The reduction is attributed to a reduction of the fuel spray penetration length and a smaller effective injection orifice area, resulting in a shorter total duration of fuel spray impingement on the piston crown. Soot formation occurred primarily in the gas phase when the first of two fuel sprays was ignited and persisted due to the second fuel spray entering an existing flame leading to fuel rich combustion.

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Section: Imagingmentioning

confidence: 99%

In cylinder visualization of stratified combustion of E85 and main sources of soot formation

Johansen

Hemdal

2015

Fuel

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“…Their results demonstrated that a large degree of cyclic variation existed when the time delay after start of injection (SOI) was closer to its time of the opening response. Marchi et al (2010) assessed the spray stability of the injector by analyzing the mean and root mean square (rms) images of the fuel spray. Their results revealed that the positive-step inward seal band design injector produced the most repeatable spray among their three prototype SIDI injectors.…”

Section: Introductionmentioning

confidence: 99%

Analyzing the Cycle-to-Cycle Variations of Pulsing Spray Characteristics by Means of the Proper Orthogonal Decomposition

Chen

Hung

et al. 2013

Atomiz Spr

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This paper presents a novel approach to analyze the cycle-to-cycle variations of pulsing spray characteristics. The purpose is to quantify the cycle-to-cycle variations of the macroscopic characteristics of spark-ignition direct-injection (SIDI) fuel injector spray, so that improvements of air-fuel mixture formation can be made to enhance the combustion efficiency and reduce emissions of SIDI engines. The experiments were carried out using an eight-hole SIDI fuel injector under a controlled ambient environment with an extended range of test conditions. Using a strobe light as an illumination source, multiple cycles of macroscopic spray structure images at a fixed injection delay time were taken by a CCD camera. The proper orthogonal decomposition (POD) technique was implemented to analyze the cycle-to-cycle characteristics of spray variation. In addition, the effects of injection pressure, ambient pressure, and fuel type on spray variation were also investigated. POD analysis reveals that the mode 1 pattern captured the ensemble-averaged spray shape, the mode 2 pattern provided quantification of spatial fuel distribution variations of different cycles of spray, and higher mode patterns further quantified the finer details of the variations surrounding the well-atomized periphery of the spray structure. POD analysis also quantitatively confirms that better-atomized sprays led to slightly higher variations of finer structures along the spray boundary. Overall, this study demonstrates that POD analysis can be used as a novel approach to quantify the cycle-to-cycle variation of pulsing spray characteristics.

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“…To get a quantitative information on the liquid deformation in the near-nozzle area root mean square images (RMS) were created from a sequence of snapshots (750 images), see Figure 4 b), in PCO Picture Viewer 1 . The analysis of visual data using RMS images was also performed in previous works such as (Marchi et al 2010, Zaremba et al 2017. The pixel intensities in the RMS image are computed by calculating the standard deviation of the pixel intensities of the image sequence.…”

Section: Image Post-processingmentioning

confidence: 99%

An experimental analysis of the spraying processes in improved design of effervescent atomizer

Zaremba

Kozák

Malý

et al. 2018

International Journal of Multiphase Flow

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This work experimentally examines the primary atomization processes in a newly developed atomizer, similar to effervescent atomizer concept, at low pressures and low gas-to-liquid ratios (GLR). Several experimental and post-processing techniques are applied to investigate the spray spatial evolution. The near-nozzle area is captured by a high-speed camera with a long-distance microscope. Further, characteristics of the developed spray are investigated by a phase-Doppler analyser (PDA). The high-speed recordings are processed by the proper orthogonal decomposition (POD). The frequency analysis of examined phenomenon is done by the fast Fourier transformation (FFT) at selected positions in the images. The POD enables to sort out data according to the importance of characteristic shapes occurring in the recordings. The velocity and dimensions of discharging liquid are measured in images by a point-tracking method. Dimensionless criteria are estimated to describe the atomization principles where several new findings are found comparing the previous studies. The spatial spray evolution is described by the processed PDA data. A simplification, based on the Stokes number, is used to estimate a gas motion in the spray. This approach enables to investigate the interaction between the spray and ambient atmosphere. The combination of experimental and post-processing techniques confirms the previous findings of the improved effervescent atomizer. In other words, the atomizer operates inherently at annular twophase flow regime which, however, leads to a specific atomizing mechanism i.e. bubble bursts, the same as in the effervescent spraying process. However, an importance of the interaction between the two following bubble bursts is highlighted as driving atomization mechanism. This specific behaviour is reason why the atomizer can be operated at low consumption of gas and low-pressure regimes. Moreover, the applied experimental and post-processing techniques indicate a potential for further advanced data post-processing of the stochastic processes of liquid atomization.

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Spray stability of outwards opening pintle injectors for stratified direct injection spark ignition engine operation

Cited by 39 publications

References 13 publications

In cylinder visualization of stratified combustion of E85 and main sources of soot formation

In cylinder visualization of stratified combustion of E85 and main sources of soot formation

Analyzing the Cycle-to-Cycle Variations of Pulsing Spray Characteristics by Means of the Proper Orthogonal Decomposition

An experimental analysis of the spraying processes in improved design of effervescent atomizer

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