# CFD Analysis of a Large Marine Engine Scavenging Process

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Materials and Methods

#### 2.1. Mathematical Model

#### 2.2. Engine Description

#### 2.3. The Computational Mesh and Simulation Details

#### 2.4. Validation

## 3. Simulation Results and Discussion

#### 3.1. Influence of Engine Load on the Scavenging Process

_{2}and O

_{2}are of great importance in the engine combustion process, the concentration of these species is calculated and tracked in the present work. The initial values of the concentrations in the cylinder after the previous combustion process and the values of the concentrations in the scavenging air are reported in Table 4.

_{2}and CO

_{2}, the main species responsible for the combustion process, is presented. This kind of analysis is possible with CFD simulations, since they can track single species. It can be seen that the concentration of O

_{2}has a faster rise for the low load cases. Consequently, also the concentration of CO

_{2}decreases faster for the lower load cases.

#### 3.2. Influence of the Pressure Difference on the Scavenging Process

#### 3.3. Influence of the Scavenging Port Angles on the Scavenging Process

_{2}and O

_{2}concentration during the scavenging process. The graph summarizes what can be seen in Figure 14: the replacement of combustion gases with fresh air is more efficient for scavenging ports with smaller angles to the normal direction. It can be seen that the concentration of O

_{2}rises fastest for the case with radial ports (0° inclination) and slowest for the 30° ports.

## 4. Conclusions

- -
- The open-source, free software package offers enough power and flexibility to allow the simulation of such a complex flow problem. The complexity consists of a large calculation domain with moving boundaries.
- -
- The problem of the size of the domain was attenuated by the use of cyclic boundaries and the simulation of just a 12-degree sector that embraces one of the 30 scavenging ports. The “pressure directed inlet velocity” type of inlet boundary condition is used instead of modeling the scavenging ports with sliding interfaces. Furthermore, a moderate mesh density proved to be adequate for the problem. It reduced the simulation domain and calculation time and allowed simulating many different cases.
- -
- The scavenging efficiency decreases with engine load but remains high enough for an efficient combustion. It is explained mostly by the shorter time available for the process because of the higher RPM. On the other hand, the driving forces responsible for the scavenging process, similarly to the pressure difference and the axial momentum, increase with load, but the effect is attenuated by the shorter time available.
- -
- The increased pressure difference between the inlet and exhaust improves all the scavenging parameters. Only the trapping efficiency is decreased, since more air is delivered. However, in practice, this method would require a more efficient turbocharger or more energy to power it.
- -
- The increase in the angle to the radial direction of the scavenging ports increases the angular momentum of the fluid in the cylinder at the expense of the axial momentum that drives the fluid exchange. As a consequence, the scavenging performances decrease. It can be concluded that the industry standard of 20° scavenging port inclination could be decreased as far as scavenging efficiency.
- -
- A pocket with remaining combustion gases is always found in the central region just under the exhaust valve. The region is bigger for higher loads, lower pressure difference, and greater scavenging port angle. In the worst cases, a pocket is found also in the cylinder center at the top of the piston.

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## References

- Skjølsvik, K.O.; Andersen, A.B.; Corbett, J.J.; Skjelvik, J.M. Study of Greenhouse Gas Emissions from Ships, Report to International Maritime Organization on the Outcome of the IMO Study on Greenhouse Gas Emissions from Ships; MARINTEK Sintef Group, Carnegie Mellon University, Center for Economic Analysis, and Det Norske Veritas: Trondheim, Norway, 2000. [Google Scholar]
- Heywood, J.B. Internal Combustion Engine Fundamentals; McGraw-Hill, Inc.: New York, NY, USA, 1988; pp. 235–245. [Google Scholar]
- OpenFOAM Software Page. 2021. Available online: https://www.openfoam.com/ (accessed on 18 June 2021).
- Jasak, H.; Weller, H.; Nordin, N. In-Cylinder CFD Simulation Using a C++ Object-Oriented Toolkit; SAE Technical Paper 2004-01-0110; SAE Mobilus: Washington, DC, USA, 2004. [Google Scholar] [CrossRef][Green Version]
- Lucchini, T.; D’Errico, G.; Jasak, H.; Tuković, Ž. Automatic Mesh Motion with Topological Changes for Engine Simulation; SAE Technical Paper; No. 2007-01-0170; SAE International: Warrendale, PA, USA, 2007. [Google Scholar] [CrossRef]
- Lamas, M.I.; Rodríguez, C.G. Computational Fluid Dynamics Analysis of the Scavenging Process in the MAN B&W 7S50MC Two-Stroke Marine Diesel Engine. J. Ship Res.
**2012**, 56, 154–161. [Google Scholar] [CrossRef] - Lamas, M.I.; Rodríguez, C.G.; Rodríguez, J.D.; Telmo, J. Numerical analysis of several port configurations in the Fairbanks-Morse 38D8-1/8 opposed piston marine engine. Brodogr. Teor. Praksa Brodogr. Pomor. Teh.
**2015**, 66, 1–11. [Google Scholar] - Sigurdsson, E.; Ingvorsen, K.M.; Jensen, M.V.; Mayer, S.; Matlok, S.; Walther, J.H. Numerical analysis of the scavenge flow and convective heat transfer in large two-stroke marine diesel engines. Appl. Energy
**2014**, 123, 37–46. [Google Scholar] [CrossRef] - Andersen, F.H. Integrated Analysis of the Scavenging Process in Marine Two-Stroke Diesel Engines. Ph.D. Thesis, Technical University of Denmark, Lyngby, Denmark, August 2015. [Google Scholar]
- Andersen, F.; Hult, J.; Nogenmyr, K.; Mayer, S. Numerical Investigation of the Scavenging Process in Marine Two-Stroke Diesel Engines; SAE Technical Paper 2013-01-2647; SAE Mobilus: Washington, DC, USA, 2013. [Google Scholar] [CrossRef]
- Andersen, F.; Hult, J.; Nogenmyr, K.; Mayer, S. CFD analysis of the scavenging process in marine two-stroke diesel engines. In Proceedings of the ASME 2014 Internal Combustion Engine Division Fall Technical Conference (ICEF2014), Columbus, IN, USA, 19–22 October 2014. [Google Scholar]
- Andersen, F.; Mayer, S. Parametric study of the scavenging process in marine two-stroke diesel engines. In Proceedings of the ASME 2015 Internal Combustion Engine Division Fall Technical Conference (ICEF2015), Houston, TX, USA, 8–11 November 2015. [Google Scholar]
- Jönsson, M. Stratified Scavenging Computations in Two-Stroke Engines Using OpenFOAM. Master’s Thesis, Chalmers University of Technology, Göteborg, Sweden, 2010. [Google Scholar]
- Xu, Z.; Ji, F.; Ding, F.; Zhao, Y.; Zhou, Y.; Zhang, Q.; Du, F. Effect of scavenge port angles on flow distribution and performance of swirl-loop scavenging in 2-stroke aircraft diesel engine. Chin. J. Aeronaut.
**2021**, 34, 105–117. [Google Scholar] [CrossRef] - Ghazikhani, M.; Hatami, M.; Safari, B.; Ganji, D.D. Experimental investigation of performance improving and emissions reducing in a two stroke SI engine by using ethanol additives. Propuls. Power Res.
**2013**, 2, 276–283. [Google Scholar] [CrossRef][Green Version] - Foteinos, M.I.; Kyrtatos, A.P.N.; Stamatelos, A.; Zogou, O.; Stamatellou, A.M. A Three-Zone Scavenging Model for Large Two-Stroke Uniflow Marine Engines Using Results from CFD Scavenging Simulations. Energies
**2019**, 12, 1719. [Google Scholar] [CrossRef][Green Version] - Ma, F.; Zhao, C.; Zhang, F.; Zhao, Z.; Zhang, S. Effects of Scavenging System Configuration on In-Cylinder Air Flow Organization of an Opposed-Piston Two-Stroke Engine. Energies
**2015**, 8, 5866–5884. [Google Scholar] [CrossRef][Green Version] - Ma, F.; Zhao, Z.; Zhang, Y.; Wang, J.; Feng, Y.; Su, T.; Zhang, Y.; Liu, Y. Simulation Modeling Method and Experimental Investigation on the Uniflow Scavenging System of an Opposed-Piston Folded-Cranktrain Diesel Engine. Energies
**2017**, 10, 727. [Google Scholar] [CrossRef][Green Version] - Ma, F.; Zhang, L.; Su, T. Simulation Modeling and Optimization of Uniflow Scavenging System Parameters on Opposed-Piston Two-Stroke Engines. Energies
**2018**, 11, 940. [Google Scholar] [CrossRef][Green Version] - Wu, Y.; Wang, Y.; Zhen, X.; Guan, S.; Wang, J. Three-dimensional CFD (computational fluid dynamics) analysis of scavenging process in a two-stroke free-piston engine. Energy
**2014**, 68, 167–173. [Google Scholar] [CrossRef] - Jia, B.; Wang, Y.; Smallbone, A.; Roskilly, A.P. Analysis of the Scavenging Process of a Two-Stroke Free-Piston Engine Based on the Selection of Scavenging Ports or Valves. Energies
**2018**, 11, 324. [Google Scholar] [CrossRef][Green Version] - Reuter, D. 2-Stroke Scavenging in Conventional and Minimally-Modified 4-Stroke Engines for Heavy Duty Applications at Low to Medium Speeds. Inventions
**2019**, 4, 44. [Google Scholar] [CrossRef][Green Version] - Ciampolini, M.; Bigalli, S.; Balduzzi, F.; Bianchini, A.; Romani, L.; Ferrara, G. CFD Analysis of the Fuel–Air Mixture Formation Process in Passive Prechambers for Use in a High-Pressure Direct Injection (HPDI) Two-Stroke Engine. Energies
**2020**, 13, 2846. [Google Scholar] [CrossRef] - Qiao, Y.; Duan, X.; Huang, K.; Song, Y.; Qian, J. Scavenging Ports’ Optimal Design of a Two-Stroke Small Aeroengine Based on the Benson/Bradham Model. Energies
**2018**, 11, 2739. [Google Scholar] [CrossRef][Green Version] - Grljušić, M.; Tolj, I.; Radica, G. An Investigation of the Composition of the Flow in and out of a Two-Stroke Diesel Engine and Air Consumption Ratio. Energies
**2017**, 10, 805. [Google Scholar] [CrossRef][Green Version] - Thornber, B.; Starr, M.; Drikakis, D. Implicit large eddy simulation of ship airwakes. Aeronaut. J.
**2010**, 1162, 715–736. [Google Scholar] [CrossRef][Green Version] - Jasak, H.; Vukčević, V.; Gatin, I.; Lalović, I. CFD validation and greed sensitivity studies of full scale ship self propulsion. Int. J. Nav. Arch. Ocean Eng.
**2019**, 11, 33–43. [Google Scholar] [CrossRef] - Viola, I.M.; Flay, E.G.; Ponzini, R. CFD analysis of the hydrodynamic performance of two candidate America’s Cup AC33 hulls. Trans. R. Inst. Nav. Archit. Part B Int. J. Small Craft Technol.
**2012**, 154, B1–B12. [Google Scholar] - Guillard, H.; Murrone, A. On the behaviour of upwind schemes in the low Mach number limit: II. Godunov type schemes. Comput. Fluids
**2004**, 33, 655–675. [Google Scholar] [CrossRef][Green Version] - Thornber, B.J.R.; Drikakis, D. Numerical dissipation of upwind schemes in low Mach flow. Int. J. Numer. Methods Fluids
**2008**, 56, 1535–1541. [Google Scholar] [CrossRef] - Salinas-Vázquez, M.; Vicente, W.; Barrios, E.; Martínez, E.; Palacio, A.; Rodríguez, A. A low-Mach number method for the numerical simulation of complex flows. Appl. Math. Model.
**2013**, 22, 9132–9146. [Google Scholar] [CrossRef] - Versteeg, H.K.; Malalasekera, W. An Introduction to Computational Fluid Dynamics: The Finite Volume Method; Longman Group Ltd.: Essex, UK, 1995. [Google Scholar]
- El Abbassi, M.; Lahaye, D.J.P.; Vuik, C. Modelling turbulent combustion coupled with conjugate heat transfer in Open Foam. In Proceedings of the 10th Mediterranean Combustion Symposium, Naples, Italy, 17–21 September 2017. [Google Scholar]
- Hult, J.; Matlok, S.; Mayer, S. Particle Image Velocimetry Measurements of Swirl and Scavenging in a Large Marine Two-Stroke Diesel Engine; SAE Techincal Paper 2014-01-1173; SAE Mobilus: Washington, DC, USA, 2014. [Google Scholar] [CrossRef]

**Figure 3.**The computational mesh with schematic insertions of the components, the exhaust port, and piston bowl zones enlarged and the bottom view of the mesh.

**Figure 4.**Influence of mesh density (number of cells) on the total fresh air concentration (fresh air mass [kg]/total mass [kg]) in the cylinder.

**Figure 6.**Fresh air propagation for the moment CA = 200° for the loads of 25%, 50%, 75%, and 100%, from left to right. The depicted contours represent fresh air concentration (fresh air mass [kg]/total mass [kg]).

**Figure 7.**The variation of the concentration of O

_{2}and CO

_{2}over time for different engine loads.

**Figure 10.**Fresh air propagation for the moment CA = 200° for the cases with pressure difference 0.25, 0.3, and 0.35 bar respectively, from left to right. The depicted contours represent fresh air concentration (fresh air mass [kg]/total mass [kg]).

**Figure 11.**The variation of the concentration of O

_{2}and CO

_{2}over time for different pressure differences.

**Figure 15.**Fresh air propagation for the moment CA = 200° for the cases with scavenging port angles of 0°, 10°, 20°, and 30° respectively, from left to right. The depicted contours represent fresh air concentration (fresh air mass [kg]/total mass [kg]).

**Figure 16.**The variation of the concentration of O

_{2}and CO

_{2}over time for different scavenging port angles.

Engine | MAN 6S50MC |
---|---|

Bore | 500 mm |

Stroke | 1910 mm |

Number of cylinders | 6 |

Power | 8656 kW |

Rotational speed | 121 min^{−1} |

BMEP ^{1} | 18 bar |

BSFC ^{2} | 171 g/kWh |

Compression ratio | 17.2 |

^{1}Brake Mean Effective Pressure;

^{2}Brake-Specific Fuel Consumption.

Boundary | Type | T (K) |
---|---|---|

piston | movingWallVelocity | 575 |

liner | fixedValue | 475 |

cylinderHead | fixedValue | 550 |

exhaustPort | fixedValue | 475 |

presout | fixedValue | case dependent |

valveStem | fixedValue | 475 |

inlet | pressureDirectedInletVelocity | case dependent |

valve | fixedValue | 475 |

frontAndBack | cyclic | - |

axis | symmetryPlane | - |

Engine Load | 25% | 50% | 75% | 100% |
---|---|---|---|---|

RPM (min^{−1}) | 76 | 96 | 110 | 121 |

Scavenge air pressure (bar) | 1.39 | 2.03 | 2.76 | 3.55 |

Scavenging receiver temperature (°C) | 26 | 29 | 34 | 41 |

Exhaust receiver pressure (bar) | 1.3 | 1.86 | 2.51 | 3.26 |

Turbine inlet temperature (°C) | 308 | 327 | 346 | 404 |

Initial cylinder pressure (bar) | 8 | 8 | 8 | 8 |

Initial cylinder temperature (°C) | 400 | 400 | 400 | 400 |

Inlet Air (%) | Diesel Exhaust (%) | |
---|---|---|

N_{2} | 76.6 | 67 |

O_{2} | 23.4 | 10 |

CO_{2} | 0 | 12 |

H_{2}O | 0 | 11 |

Engine Load | 25% | 50% | 75% | 100% |
---|---|---|---|---|

m_{del} (kg) | 0.0309 | 0.0398 | 0.0504 | 0.05456 |

η_{scav} | 0.997 | 0.979 | 0.968 | 0.931 |

η_{scav,IPC} | 0.996853 | 0.977621 | 0.966 | 0.917707 |

η_{ch} | 0.883 | 0.924 | 0.901 | 0.840 |

DR | 2.031 | 1.679 | 1.563 | 1.315 |

η_{trap} | 0.544 | 0.688 | 0.721 | 0.798 |

**Table 6.**The pressure difference resulting from pressure in the scavenging and in the exhaust receiver.

Pressure Difference (bar) | 0.25 | 0.3 | 0.35 |

Inlet pressure (bar) | 3.5 | 3.55 | 3.6 |

Exhaust pressure (bar) | 3.25 | 3.25 | 3.25 |

Pressure Difference (bar) | 0.25 | 0.30 | 0.35 |
---|---|---|---|

m_{del} (kg) | 0.0506 | 0.0557 | 0.0604 |

η_{scav} | 0.928 | 0.931 | 0.942 |

η_{scav,IPC} | 0.9016 | 0.9218 | 0.9369 |

η_{ch} | 0.821 | 0.844 | 0.865 |

DR | 1.237 | 1.342 | 1.435 |

η_{trap} | 0.830 | 0.787 | 0.754 |

Port Angle | 0° | 10° | 20° | 30° |
---|---|---|---|---|

Inlet velocity components | −1, 0, 0 | −0.98, 0.17, 0 | −0.94, 0.34, 0 | −0.87, 0.5, 0 |

m_{del} (kg) | 0.05996 | 0.05813 | 0.05456 | 0.05051 |

η_{scav} | 0.971 | 0.972 | 0.931 | 0.912 |

η_{scav,IPC} | 0.967 | 0.953 | 0.918 | 0.879 |

η_{ch} | 0.9203 | 0.8965 | 0.8397 | 0.7842 |

DR | 1.4452 | 1.4013 | 1.31499 | 1.2176 |

η_{trap} | 0.7960 | 0.7997 | 0.7982 | 0.8051 |

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**MDPI and ACS Style**

Senčić, T.; Mrzljak, V.; Medica-Viola, V.; Wolf, I.
CFD Analysis of a Large Marine Engine Scavenging Process. *Processes* **2022**, *10*, 141.
https://doi.org/10.3390/pr10010141

**AMA Style**

Senčić T, Mrzljak V, Medica-Viola V, Wolf I.
CFD Analysis of a Large Marine Engine Scavenging Process. *Processes*. 2022; 10(1):141.
https://doi.org/10.3390/pr10010141

**Chicago/Turabian Style**

Senčić, Tomislav, Vedran Mrzljak, Vedran Medica-Viola, and Igor Wolf.
2022. "CFD Analysis of a Large Marine Engine Scavenging Process" *Processes* 10, no. 1: 141.
https://doi.org/10.3390/pr10010141