Numerical Study of Evaporation Modelling for Different Fuels at High Operating Conditions in a Diesel Engine †
by
, ,
Ali Raza
1,*
,
Sajjad Miran
2,
Tayyab Ul Islam
1,
Kishwat IJaz Malik
1,
Zunaira-Tu-Zehra
3 and
Marva Hadia
4 1
Department of Mechanical Engineering, National University of Technology, IJP Road, Islamabad 44000, Pakistan
2
Department of Mechanical Engineering, University of Gujrat, Gujrat 50700, Pakistan
3
Department of Mathematics, The Women University, Multan 60000, Pakistan
4
Department of Mechanical Engineering, NUST College of EME, National University of Sciences and Technology, Islamabad 44000, Pakistan
*
Author to whom correspondence should be addressed.
†
Presented at the 1st International Conference on Energy, Power and Environment, Gujrat, Pakistan, 11–12 November 2021.
Eng. Proc. 2021, 12(1), 8; https://doi.org/10.3390/engproc2021012008
Published: 22 December 2021
(This article belongs to the Proceedings of The 1st International Conference on Energy, Power and Environment)
Abstract
:A fuel injection system in a diesel engine has different processes that affect the complete burning of the fuel in the combustion chamber. These include the primary and secondary breakups of liquid fuel droplets and evaporation. In the present paper, evaporation of two different diesel fuels has been modelled numerically. Evaporation of n-heptane and n-decane is governed by the conservation equations of mass, energy, momentum, and species transport. Results have been plotted by varying the droplet diameter and temperature. It was observed that droplet size, temperature of droplets, and ambient temperature have notable effect on the evaporation time of diesel fuel droplets in the engine cylinder.
1. Introduction
Automotive industries aim to enhance the efficiency and power output of engines whilst remaining within the range of imposed standard emission principles, which are becoming more strict and rigorous day by day [1]. Evaporation modelling of diesel fuel droplets was started by Landis and Mills [2], followed by Law [3]. Fuel is injected in the form of spray from a nozzle hole at a temperature higher than its saturation temperature. In this way, the fuel becomes superheated and its temperature rises above the critical value [4,5]. During the evaporation process, the gas phase is governed by the Eulerian approach, while droplet trajectories are traced in a Lagrangian frame [6]. In the present work, conservation equations of energy, mass, momentum, and species have been coupled and numerically solved to model the overall evaporation of two different diesel fuels. Evaporation of fuel droplets present in the engine cylinder starts from the surface diffusion [7]. Droplets are injected into the engine cylinder by creating a discrete phase injection. There are different types of injections that can applied. In this work, a single injection was used to inject the liquid fuel into the chamber [8,9,10,11,12]. Unsteady particle tracking was done through the DPM in the continuous phase. Liquid particles were injected in the form of spray from a hole that dispersed in the continuous phase. Particle trajectories were also observed in the continuous phase at a high temperature and pressure in the Lagrangian frame of reference.
2. Numerical Modelling
The presented model was applied to govern the evaporation of droplets of n-heptane and n-decane fuels in Ansys Fluent. The DPM was applied to solve the discrete phase, i.e., fuel droplets entering into the continuous phase present in the combustion chamber. The presented model was applied to the engine specifications available in [13].
3. Model Validation
The droplet evaporation model presented above was implemented in the Ansys Fluent; obtained numerical results were compared with the vaporization experiments by Chauveau et al. [8] as shown in Figure 1. The numerical results of the presented model were also compared with the evaporation of model of Abramzon and Sirignano [9] and additionally with the earlier work in [12,13].
4. Results and Discussion
In the following section, results for n-decane and n-heptane fuel droplets are presented under different ambient conditions. Normalized droplet diameters have been plotted using D-square law against the normalized time.
4.1. Case 1 Fuel: n-Decane
From Figure 2, we can clearly see that the n-decane droplets of 10 microns in diameter evaporated completely within a short period of time at a high ambient temperature of 973 K compared to the lower ambient temperatures of 623 K and 823 K. Similarly, in Figure 3, vaporization of n-decane droplets of 20 micron in diameter has been plotted, once again playing the same trend. Droplets of the same size evaporated more quickly at high temperatures. As the temperature increases, vaporization time decreases and vice versa.
4.2. Case 2 Fuel: n-Heptane
In Figure 6 and Figure 7, vaporization results for n-heptane fuel droplets are presented. In this section, droplets sized 10 and 20 microns were considered. It was observed that droplets of smaller size evaporated within a short time compared to droplets of larger sizes. Ambient temperature also affects the evaporation of diesel fuel droplets. At a temperature of 973 K, the droplet lifetime was much shorter than at a temperature of 623 K. Also, it was observed that the evaporation time of n-heptane fuel droplets was lower than that of n-decane.
In Figure 6, decrease in the diameter of n-heptane fuel droplets 10 microns in size have been plotted using the D2-law against the normalized time. It is obvious that at a lower temperature of 623 K, droplet life is higher than at the temperatures of 823 and 973 K. For the temperature of 623 K, the droplet residence time is greater than at the temperatures of 823 K and 973 K. In Figure 7, the evaporation of 20-micron droplets has been plotted against the normalized time. In this figure, it can be clearly seen that by increasing the droplet size, the evaporation time of droplets also increased. In Figure 7, the regression rate of 20-micron droplets has been plotted at three different ambient temperatures. Evaporation time at high ambient temperatures is low and vice versa. In Figure 8 and Figure 9, temperature profiles of 10- and 20-micron droplets have been plotted against the normalized time. The same trend can be observed across the different ambient temperatures.
5. Conclusions
Our results show that droplet with a large diameter take more time to evaporate completely compared to the smaller ones. Small droplets evaporate more quickly due to a shorter heat up period than for the larger ones. Droplets of the same size behave differently at different ambient temperatures. The droplet evaporation time for a high temperature is smaller than for a low temperature. Further temperature profiles of droplets plotted against the injection time shows that small droplets evaporate quickly by absorbing the temperature quickly.
References
- Heywood, J.B. Internal Combustion Engine Fundamentals; McGraw-Hill Education: New York, NY, USA, 2018. [Google Scholar]
- Landis, R.B.; Anthony, F. Mills. Effect of internal diffusional resistance on the evaporation of binary droplets. In International Heat Transfer Conference Digital Library; Begel House Inc.: Danbury, CT, USA, 1974. [Google Scholar]
- Law, C.K. Recent advances in droplet vaporization and combustion. Prog. Energy Combust. Sci. 1982, 8, 171–201. [Google Scholar] [CrossRef]
- Prausnitz, J.M.; Lichtenthaler, R.N.; De Azevedo, E.G. Molecular Thermodynamics of Fluid-Phase Equilibria; Pearson Education: London, UK, 1998. [Google Scholar]
- Josette, B. Supercritical (and subcritical) fluid behavior and modeling: Drops, streams, shear and mixing layers, jets and sprays. Prog. Energy Combust. Sci. 2000, 26, 329–366. [Google Scholar]
- Gosman, A.D.; Loannides, E. Aspects of computer simulation of liquid-fueled combustors. J. Energy 1983, 7, 482–490. [Google Scholar] [CrossRef]
- Youngchul, R.; Reitz, R.D. A vaporization model for discrete multi-component fuel sprays. Int. J. Multiph. Flow 2009, 35, 101–117. [Google Scholar]
- Chauveau, C.; Halter, F.; Lalonde, A.; Gökalp, I. An experimental study on the droplet vaporization: Effects of heat conduction through the support fiber. In Proceedings of the 22nd Annual Conference on Liquid Atomization and Spray Systems (ILASS Europe 2008), Como Lake, Italy, 8–10 September 2008. [Google Scholar]
- Abramzon, B.; Sirignano, W.A. Droplet vaporization model for spray combustion calculations. Int. J. Heat Mass Transf. 1989, 32, 1605–1618. [Google Scholar] [CrossRef]
- Lefebvre, H.A.; McDonell, V.G. Atomization and Sprays; CRC Press: Boca Raton, FL, USA, 1989. [Google Scholar]
- Haider, A.; Levenspiel, O. Drag coefficient and terminal velocity of spherical and nonspherical particles. Powder Technol. 1989, 58, 63–70. [Google Scholar] [CrossRef]
- Raza, A.; Latif, R.; Raza, M.; Shafi, I. Numerical modelling of diesel fuel multiphase evaporation in heavy duty diesel engine. In Proceedings of the 21st Australasian Fluid Mechanics Conference (AFMC), Adelaide, Australia, 10–13 December 2018. [Google Scholar]
- Raza, A.; Mehboob, H.; Miran, S.; Arif, W.; Rizvi, S.F.J. Investigation on the Characteristics of Biodiesel Droplets in the Engine Cylinder. Energies 2020, 13, 3637. [Google Scholar] [CrossRef]
Figure 1.
Comparison of model for n-decane droplet vaporization with experiment of Chauveau et al. and numerical results for AS-1989 at 623 K.
Figure 1.
Comparison of model for n-decane droplet vaporization with experiment of Chauveau et al. and numerical results for AS-1989 at 623 K.
Figure 2.
Vaporization of 10-micron n-decane droplets at different ambient temperatures.
Figure 3.
Vaporization of 20-micron n-decane droplets at different ambient temperatures.
Figure 4.
Effect of ambient gas temperature on the evaporation of 10-micron n-decane droplets.
Figure 5.
Effect of ambient gas temperature on the evaporation of 20-micron n-decane droplets.
Figure 6.
Vaporization of 10-micron n-decane droplets at different ambient temperatures.
Figure 7.
Vaporization of 20-micron n-decane droplets at different ambient temperatures.
Figure 8.
Effect of ambient gas temperature on the evaporation 10-micron n-decane droplets.
Figure 9.
Effect of ambient gas temperature on the evaporation 20-micron n-decane droplets.
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MDPI and ACS Style
Raza, A.; Miran, S.; Islam, T.U.; Malik, K.I.; Zunaira-Tu-Zehra; Hadia, M. Numerical Study of Evaporation Modelling for Different Fuels at High Operating Conditions in a Diesel Engine. Eng. Proc. 2021, 12, 8. https://doi.org/10.3390/engproc2021012008
AMA Style
Raza A, Miran S, Islam TU, Malik KI, Zunaira-Tu-Zehra, Hadia M. Numerical Study of Evaporation Modelling for Different Fuels at High Operating Conditions in a Diesel Engine. Engineering Proceedings. 2021; 12(1):8. https://doi.org/10.3390/engproc2021012008
Chicago/Turabian StyleRaza, Ali, Sajjad Miran, Tayyab Ul Islam, Kishwat IJaz Malik, Zunaira-Tu-Zehra, and Marva Hadia. 2021. "Numerical Study of Evaporation Modelling for Different Fuels at High Operating Conditions in a Diesel Engine" Engineering Proceedings 12, no. 1: 8. https://doi.org/10.3390/engproc2021012008
