Flame image velocimetry analysis of reacting jet flow fields with a variation of injection pressure in a small-bore diesel engine

Abstract

This study measures in-flame flow fields in a single-cylinder small-bore optical diesel engine using Flame Image Velocimetry (FIV) applied to high-speed soot luminosity movies. Three injection pressures were tested for a two-hole nozzle injector to cause jet-wall interaction and a significant jet-jet interaction within 45° inter-jet spacing. The high-pressure fuel jets were also under the strong influence of a swirl flow. For each test condition, soot luminosity signals were recorded at a high framing rate of 45 kHz with which the time-resolved, two-dimensional FIV post-processing was performed based on the image contrast variations associated with flame structure evolution and internal pattern change. A total of 100 combustion events for each injection pressure were recorded and processed to address the inherent cyclic variations. The ensemble-averaged flow fields were used for detailed flow structure discussion, and Reynolds decomposition using a spatial filtering method was applied to obtain high-frequency fluctuations that were found to be primarily turbulence. The detailed analysis of flow fields suggested that increased injection pressure leads to enhanced jet flow travelling along the bowl wall and higher flow vectors penetrating back towards the nozzle upon the impingement on the wall. Within the jet-jet interaction region, the flow vectors tend to follow the swirl direction, which increases with increasing injection pressure. The FIV also captured a turbulent ring vortex formed in the wall-jet head, which becomes larger and clearer at higher injection pressure. A vortex generated in the centre of combustion chamber was due to the swirl flow with its position being shifted at higher injection pressure. The bulk flow magnitude indicated significant cyclic variations, which increases with injection pressure. The turbulence intensity is also enhanced due to higher injection pressure, which primarily occurs in the wall-jet head region and the jet-jet interaction region.

Keywords

Diesel engine natural soot luminosity FIV in-flame flow field injection pressure variation

Get full access to this article

View all access options for this article.

References

Kuti

Zhu

Nishida

Wang

Huang

. Characterization of spray and combustion processes of biodiesel fuel injected by diesel engine common rail system. Fuel 2013; 104: 838–846.

Bardi

Payri

Malbec

Bruneaux

Pickett

Manin

. Engine combustion network: comparison of spray development, vaporization, and combustion in different combustion vessels. Atomization Spray 2012; 22(10): 807–842.

Uchida

Aizawa

Kondo

Kuboyama

. Diesel flame imaging and quantitative analysis of in-cylinder soot oxidation. Int J Engine Res 2016; 18: 422–435.

Bruneaux

. Mixing process in high pressure diesel jets by normalized laser induced exciplex fluorescence part I: free jet. SAE paper 2005-01-2100, 2005.

Shundoh

Kakegawa

Tsujimura

Kobayashi

. The effect of injection parameters and swirl on diesel combustion with high pressure fuel injection. SAE paper 910489, 1991.

Rollbusch

. Effects of hydraulic nozzle flow rate and high injection pressure on mixture formation, combustion and emissions on a single-cylinder DI light-duty diesel engine. Int J Engine Res 2012; 13: 323–339.

Gumus

Sayin

Canakci

. The impact of fuel injection pressure on the exhaust emissions of a direct injection diesel engine fueled with biodiesel-diesel fuel blends. Fuel 2012; 95: 486–494.

Agarwal

Srivastava

Dhar

Maurya

Shukla

Singh

. Effect of fuel injection timing and pressure on combustion, emissions and performance characteristics of a single cylinder diesel engine. Fuel 2013; 111: 374–383.

Içingür

Altiparmak

. Effect of fuel cetane number and injection pressure on a DI diesel engine performance and emissions. Energy Convers Manag 2003; 44: 389–397.

10.

Pierpont

Reitz

. Effects of injection pressure and nozzle geometry on DI diesel emissions and performance. SAE paper 950604, 1995.

11.

Pickett

Siebers

. Soot in diesel fuel jets: effects of ambient temperature, ambient density, and injection pressure. Combust Flame 2004; 138: 114–135.

12.

Agarwal

Dhar

Srivastava

Maurya

Singh

. Effect of fuel injection pressure on diesel particulate size and number distribution in a CRDI single cylinder research engine. Fuel 2013; 107: 84–89.

13.

Kook

Hawkes

. The planar imaging of laser induced fluorescence of fuel and hydroxyl for a wall-interacting jet in a single-cylinder, automotive-size, optically accessible diesel engine. Fuel 2015; 140: 143–155.

14.

Zhang

Rao

Kook

Hawkes

. The development of hydroxyl and soot in a methyl decanoate-fuelled automotive-size optical diesel engine. Fuel 2016; 166: 320–332.

15.

Rajalingam

Farrell

. The effect of injection pressure on air entrainment into transient diesel sprays. SAE paper 1999-01-0523, 1999.

16.

Bruneaux

Verhoeven

Baritaud

. High pressure diesel spray and combustion visualization in a transparent model diesel engine. SAE paper 1999-01-3648, 1999.

17.

Bergin

Reitz

Miles

Hildingsson

Hultqvist

. Fuel injection and mean swirl effects on combustion and soot formation in heavy duty diesel engines. SAE paper 2007-01-0912, 2007.

18.

Miles

Megerle

Hammer

Nagel

Reitz

Sick

. Late-cycle turbulence generation in swirl-supported, direct-injection diesel engines. SAE paper 2002-01-0891, 2002.

19.

Kook

. Injection pressure effects on the flame development in a light-duty optical diesel engine. SAE Int J Engines 2015; 8: 609–624.

20.

Musculus

MPB

. Effects of the in-cylinder environment on diffusion flame lift-off in a DI diesel engine. SAE paper 2003-01-0074, 2003.

21.

Zhang

Kim

Rao

Kook

Kim

Kweon

. In-flame soot particle structure on the up- and down-swirl side of a wall-interacting jet in a small-bore diesel engine. Proc Combust Inst 2019; 37: 4847–4855.

22.

Dembinski

Ångström

. Optical study of swirl during combustion in a CI engine with different injection pressures and swirl ratios compared with calculations. SAE paper 2012-01-0682, 2012.

23.

Rusly

Kook

Hawkes

. The shortening of lift-off length associated with jet-wall and jet-jet interaction in a small-bore optical diesel engine. Fuel 2014; 125: 1–14.

24.

Genzale

Reitz

Musculus

MPB

. Effects of piston bowl geometry on mixture development and late-injection low-temperature combustion in a heavy-duty diesel engine. SAE Int J Engines 2009; 1: 913–937.

25.

Chartier

Aronsson

Andersson

Egnell

Johansson

. Influence of jet–jet interactions on the lift-off length in an optical heavy-duty DI diesel engine. Fuel 2013; 112: 311–318.

26.

Pickett

Kook

Persson

Andersson

. Diesel fuel jet lift-off stabilization in the presence of laser-induced plasma ignition. Proc Combust Inst 2009; 32(2): 2793–2800.

27.

Rusly

Kook

. Effect of injection pressure on transient behaviour of wall-interacting jet flame base in an automotive-size diesel engine. SAE Int J Fuels Lubr 2013; 6: 615–626.

28.

Zhang

Rao

Kook

Chan

, et al. Effect of jet-jet interactions on soot formation in a small-bore diesel engine. Proc Combust Inst 2017; 36: 3559–3566.

29.

Malbec

Bruneaux

. Study of air entrainment of multi-orifice diesel injection by particle image velocimetry—effect of neighboring jets interaction and transient behavior after end of injection. SAE Int J Engines 2010; 3: 107–123.

30.

Petersen

Miles

. PIV measurements swirl-plane of a motored light-duty diesel engine. SAE Int J Engines 2011; 4: 1623–1641.

31.

Shioji

Kimoto

Okamoto

Ikegami

. An analysis of diesel flame by picture processing. JSME Int J 1989; 32: 434–442.

32.

Won

Kamimoto

Kosaka

. A study on soot formation in unsteady spray flames via 2-D soot imaging. SAE paper 920114, 1992.

33.

Winterbone

Yates

Clough

Rao

Gomes

Sun

. Combustion in high-speed direct injection diesel engines—a comprehensive study. Proc Inst Mech Eng C: J Mech Eng Sci 1994; 208: 223–240.

34.

Dembinski

Ångström

. Swirl and injection pressure effect on post-oxidation flow pattern evaluated with combustion image velocimetry, CIV, and CFD simulation. SAE paper 2013-01-2577, 2013.

35.

Dembinski

Ångström

. Swirl and injection pressure impact on after- oxidation in diesel combustion, examined with simultaneous combustion image velocimetry and two colour optical method. SAE paper 2013-01-0913, 2013.

36.

Dembinski

. The effects of injection pressure and swirl on in-cylinder flow pattern and combustion in a compression-ignition engine. Int J Engine Res 2014; 15: 444–459.

37.

Dembinski

Ångström

Razzaq

. In-cylinder flow pattern evaluated with combustion image velocimetry, CIV, and CFD calculations during combustion and post-oxidation in a HD diesel engine. SAE paper 2013-24-0064, 2013.

38.

Zha

Busch

Warey

Peterson

Kurtz

. A study of piston geometry effects on late-stage combustion in a light-duty optical diesel engine using combustion image velocimetry. SAE Int J Engines 2018; 11: 783–804.

39.

Zhao

Kaiser

. Optical diagnostics for knock in compression-ignition engines via high-speed imaging. SAE Int J Engines 2018; 11: 903–918.

40.

Rao

Kook

. Optimisation of image processing parameters for flame image velocimetry (FIV) measurement in a single-cylinder, small-bore optical diesel engine. SAE paper 2019-01-0719, 2019.

41.

Adrian

Westerweel

. Particle image velocimetry. Cambridge: Cambridge University Press, 2011.

42.

Westerweel

Scarano

. Universal outlier detection for PIV data. Exp Fluids 2005; 39: 1096–1100.

43.

Clark

Kook

. Correlation of spatial and temporal filtering methods for turbulence quantification in spark-ignition direct-injection (SIDI) engine flows. Flow Turbul Combust 2018; 101: 161–189.

44.

Rao

Zhang

Kook

Kim

Kweon

. Understanding in-cylinder soot reduction in the use of high pressure fuel injection in a small-bore diesel engine. Proc Combust Inst 2019; 37: 4839–4846.