Thermodynamic and optical characterizations of a high performance GDI engine operating in homogeneous and stratified charge mixture conditions fueled with gasoline and bio-ethanol

Sementa, Paolo; Vaglieco, Bianca Maria; Catapano, Francesco

doi:10.1016/j.fuel.2011.12.068

Cited by 127 publications

(59 citation statements)

References 18 publications

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“…After this time, as shown in Figure 10, strong luminous flames were observed first systematically in the intake valves region and then in random locations near the walls. As observed in previous works [13,39,51,60], these flames were due to the diffusive combustion of stratified fuel in the injector region and on the piston surfaces. In terms of spectroscopic evidence (Figure 18b), these flames featured a continuous signal that increased with a wavelength similar to the blackbody curve described by Planck's radiation law [61].…”

Section: Hcoh + Hν → H + Hco Hcoh + Hν → H + Hcosupporting

confidence: 74%

Flame Front Propagation in an Optical GDI Engine under Stoichiometric and Lean Burn Conditions

et al. 2017

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Lean fueling of spark ignited (SI) engines is a valid method for increasing efficiency and reducing nitric oxide (NO x ) emissions. Gasoline direct injection (GDI) allows better fuel economy with respect to the port-fuel injection configuration, through greater flexibility to load changes, reduced tendency to abnormal combustion, and reduction of pumping and heat losses. During homogenous charge operation with lean mixtures, flame development is prolonged and incomplete combustion can even occur, causing a decrease in stability and engine efficiency. On the other hand, charge stratification results in fuel impingement on the combustion chamber walls and high particle emissions. Therefore, lean operation requires a fundamentally new understanding of in-cylinder processes for developing the next generation of direct-injection (DI) SI engines. In this paper, combustion was investigated in an optically accessible DISI single cylinder research engine fueled with gasoline. Stoichiometric and lean operations were studied in detail through a combined thermodynamic and optical approach. The engine was operated at a fixed rotational speed (1000 rpm), with a wide open throttle, and at the start of the injection during the intake stroke. The excess air ratio was raised from 1 to values close to the flammability limit, and spark timing was adopted according to the maximum brake torque setting for each case. Cycle resolved digital imaging and spectroscopy were applied; the optical data were correlated to in-cylinder pressure traces and exhaust gas emission measurements. Flame front propagation speed, flame morphology parameters, and centroid motion were evaluated through image processing. Chemical kinetics were characterized based on spectroscopy data. Lean burn operation demonstrated increased flame distortion and center movement from the location of the spark plug compared to the stoichiometric case; engine stability decreased as the lean flammability limit was approached.

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Section: Hcoh + Hν → H + Hco Hcoh + Hν → H + Hcosupporting

confidence: 74%

Flame Front Propagation in an Optical GDI Engine under Stoichiometric and Lean Burn Conditions

et al. 2017

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“…The diffusion flames in spray guided stratified gasoline combustion followed the piston crown in the same manner as shown in the liner images in Figure 13. Fuel film diffusion flames have also been observed for E85 in wall guided stratified operation [39]. Piston fuel films are expected due to the greater spray penetration length of ethanol in comparison to alkane fuels as discussed previously.…”

Section: Imagingmentioning

confidence: 59%

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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“…Maricq et al, 1999a;Harris and Maricq, 2001;Khalek et al, 2010) indicate that the GDI exhaust particles are (in number) mainly in particle sizes below 100 nm. In addition, the size distribution has been observed to be bi-modal (Barone et al, 2012;Sementa et al, 2012;Sgro et al, 2012;Maricq et al, 1999a). The mode of smaller particles (mean particle size between 10 and 20 nm) has previously been observed to consist of spherical amorphous carbon (Sgro et al, 2012;Barone et al, 2012) and to be partly charged indicating their formation at high temperatures (Sgro et al, 2012).…”

Section: Introductionmentioning

confidence: 92%

“…Heikkil€ a et al (2009) and L€ ahde et al (2011)). In the case of the GDI technology, the direct fuel injection can increase the risk for increased particulate emission due to incomplete fuel volatilization, partially fuel rich zones, and impingement of fuel to piston and cylinder surfaces (Maricq et al, 1999b;Bonandrini et al, 2012;Sementa et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Exhaust particles of modern gasoline vehicles: A laboratory and an on-road study

Karjalainen

Pirjola

Heikkilä

et al. 2014

Atmospheric Environment

160

114

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Thermodynamic and optical characterizations of a high performance GDI engine operating in homogeneous and stratified charge mixture conditions fueled with gasoline and bio-ethanol

Cited by 127 publications

References 18 publications

Flame Front Propagation in an Optical GDI Engine under Stoichiometric and Lean Burn Conditions

Flame Front Propagation in an Optical GDI Engine under Stoichiometric and Lean Burn Conditions

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

Exhaust particles of modern gasoline vehicles: A laboratory and an on-road study

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