# Numerical Analysis of Nozzle Flow and Spray Characteristics from Different Nozzles Using Diesel and Biofuel Blends

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## Abstract

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## 1. Introduction

_{x}was identified to be smaller compared to the diesel.

## 2. Mathematical Model

#### 2.1. Injector Flow Phase

_{i}is the fluid velocity, $\dot{\gamma}$ is the shear stress, and g

_{i}= −9.81 m/s is the gravitational acceleration at the earth’s surface.

#### 2.2. Discrete Particle Phase

_{p}is the fluid density; u is the velocity of the particle and u

_{p}is the velocity of the fluid phase; F

_{x}is the other forces that interact with the particles due to mass, acceleration, and pressure; and F

_{D}(u − u

_{p}) is the drag force that equates to each of the particles, where F

_{D}is defined as:

_{p}is the particle density, C

_{D}is the particles drag coefficient, Re is the Reynolds number, and d

_{p}is the particle diameter of the droplets that are assumed as spheres in this study. The equation for C

_{D}is given as:

_{1}, α

_{2}, and α

_{3}are constants based on the ranges of Reynolds number.

_{other}is the additional interaction forces, Δt is the time step, and ṁ

_{p}is the particle mass flow rates. The particle trajectory can be calculated using:

_{T}is the thermophoric coefficient, which use the form suggested by Talbot [33]:

_{c}is the fluid thermal conductivity based on translational energy only, k

_{p}is the particle thermal conductivity, m

_{p}is the particle mass, µ is the fluid viscosity, C

_{s}= 1.17, C

_{t}= 2.18, and C

_{m}= 1.14.

#### 2.3. Spray Simulations

#### 2.3.1. Primary Breakup Modeling

_{KH}) and corresponding wavelength (Λ

_{KH}) according to Reitz [36] is calculated using:

_{g}denoting the gas density, ρ

_{l}is the liquid density, σ is surface tension, U

_{r}is the magnitude of velocity between two phases, and v

_{l}is the liquid viscosity.

_{KH}occurred due to a decrease in the droplet radius. Hence, the breakup time τ

_{KH}and the critical droplet radius r

_{KH}are calculated by:

_{0}= 0.61 and B

_{l}= 20.

_{RT}) is given by:

_{t}is the droplet acceleration. The wave number is computed using:

_{T}waves were propagating, the time becoming larger than the breakup time τ

_{RT}breakup will occur. The τ

_{RT}is calculated using:

_{τ}is the Rayleigh–Taylor breakup time constant. Then, the radius of the smaller droplets is given using:

_{RT}is the breakup radius constant.

#### 2.3.2. Secondary Breakup Modeling

_{0}is the initial flow velocity, l

_{0}is the characteristic diameter of the obstacle, and t

_{0}is the particle relaxation time.

## 3. Experimental Procedures

#### 3.1. Fuel Preparation

#### 3.2. Fuel Properties

#### 3.3. Experiment Setup

## 4. Simulation Methodology

^{−3}to 10

^{−4}. The range of time step was set between 1.0 × 10

^{−6}s to 1.0 × 10

^{−8}s. The fuels used for this study are listed in Table 1.

#### Grid Independence Tests

## 5. Result and Discussion

#### 5.1. Model Validation

_{s}is the widths of the spray cloud, which were denoted as a length between the spray cloud borders.

#### 5.2. Nozzle Flow Simulations

#### 5.3. Spray Simulation Results

#### 5.3.1. Spray Images Growth

#### 5.3.2. Spray Tip Penetration

#### 5.3.3. Spray Cone Angle

#### 5.3.4. Spray Width

_{S}) over the nozzle hydraulic diameters (D) has been used to compare the data of spray width. The spray widths were taken into account to compare the spray characteristics of different nozzle shapes under the real diesel engine and high-pressure conditions. Figure 17 displays the results of spray width (W

_{S}/D) along the spray axis length. As can be seen from Figure 17, the spray width of the elliptical A and elliptical B nozzle shapes was much larger than that of the circle shape for all pressure conditions. Furthermore, the spray width of elliptical B was much bigger than the elliptical A nozzle shape. These results showed that the superior spray atomization and bigger spray cone angle could be achieved by using elliptical A and elliptical B nozzle shape compared to a circular nozzle shape. From the graph in Figure 17, it is apparent that the elliptical A and B spray widths were fluctuating along the spray axis length. This investigation shows that elliptical A and elliptical B experienced an axis-switching phenomenon under the real diesel engine and high-pressure conditions. What is interesting in this data is that as the backpressure was increased with the same injection pressure, the axis-switching phenomenon of the spray width decreased. The current study found that the aerodynamic effects could be boosted by increasing the backpressure. Another important finding was that the high-pressure conditions were useful to reduce the axis-switching phenomenon. All the nozzle shapes demonstrated higher spray width when the injection pressure was increased. It seems possible that these results were due to a higher difference between inlet and outlet velocity and steady air and fuel interaction were achieved when the spray velocity became greater under a higher injection pressure. These findings of the current study were consistent with those of Abramovich [44] who found that axis-switching was due to pressure differentials in the plane of the vortex ring.

## 6. Conclusions

- The nozzle flow simulation results indicated that the fuel type had little effect on the cavitation area and it is dependence on the nozzle spray shape. The diesel delivered slightly a higher average velocity than hybrid biofuel under high injection pressure (180 MPa). These behaviors were generally caused by viscosity and density properties. The cavitations intensity was more intensive for elliptical A and elliptical B as compared to the circle nozzle shape for the same injection time. The aspect ratio of the elliptical nozzle shape was found to affect the cavitations flow, where the elliptical B cavitations intensity was more intensive than the elliptical A nozzle shape.
- The droplet size of the elliptical nozzle shape was smaller compared to the circular shape due to higher aerodynamic effects found in the elliptical nozzle shape that could reduce the droplets size, and thus leading to a bigger cloud formation after the secondary breakup. The evidence from this study suggests that the droplet size became smaller when the pressure was increased for both diesel and hybrid biofuel
- The spray tip penetration of the elliptical nozzle shape was smaller than the circular nozzle shape. This was due to the circular nozzle having smaller spray widths and cone angles. Further analysis showed that the type of fuel on the different nozzle shape had a small effect towards the spray tip penetration, although diesel fuel gave a slightly higher spray tip penetration compared to hybrid biofuel blends. In addition, the spray tip penetration was affected by the aspect ratio of the elliptical nozzle shape.
- The elliptical nozzle shape was larger compared to the circular nozzle shape in terms of spray cone angles. The spray cone angle for elliptical B was found to be much higher than that of elliptical A. This indicated that the aspect ratio of the elliptical nozzle shape was found to affect the spray cone angles. Moreover, the type of fuel on the different nozzle shape had a minor influence to the spray cone angles. The results show that diesel produced smaller cone angles compared to the biofuel blend.
- The spray widths of the circular nozzle shape were smaller than those of the elliptical A and elliptical B under all injection pressures and backpressures. However, the fuel type had little effect on the spray widths for all the nozzle shape. Furthermore, the aspect ratio of the elliptical nozzle shape was found to affect the spray width.

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

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**Figure 4.**TAB model analogy [38].

**Figure 10.**Spray tip penetration growth for a circular nozzle shape with 50 MPa of pressure and 3 MPa of backpressure for the experiments and simulation.

**Figure 11.**Evolution of spray cone angle for a circular nozzle shape with 50 MPa of pressure and 3 MPa of backpressure for experiments and simulation.

**Figure 12.**Cavitation in diesel nozzle for different nozzle spray shape with an injection pressure of 180 MPa.

**Figure 13.**Outlet Average liquid velocity under 180 MPa pressure for different type of nozzle shape and fuel.

**Figure 14.**Fuel spray images at 0.9 ms ASOI for elliptical and circular nozzle types: (

**a**) 50 MPa pressure injection, (

**b**) 100 MPa pressure injection, and (

**c**) 180 MPa pressure injection.

**Figure 15.**Spray tip penetration under different pressures: (

**a**) 50 MPa pressure injection, (

**b**) 100 MPa pressure injection, and (

**c**) 180 MPa pressure injection.

**Figure 16.**Spray cone angle for different types of nozzle shape and fuel: (

**a**) 50 MPa pressure injection, (

**b**) 100 MPa pressure injection, and (

**c**) 180 MPa pressure injection.

**Figure 17.**Ratio of spray width over nozzle hydraulic diameters (

**a**) 50 MPa pressure injection; (

**b**) 100 MPa pressure injection; (

**c**) 180 MPa pressure injection.

Types of Fuel | Density (kg/m^{3}) | Surface Tension (N/m) | Dynamic Viscosity (mPas) | Kinematic Viscosity (mm^{2}/s) (40 °C) | Vapor Pressure |
---|---|---|---|---|---|

Diesel | 830 | 0.0273 | 2.7 | 2.57 | 0.1 kPa at 40 °C |

RP032MC068 (hybrid biofuel) | 882 | 0.032 | 5.2 | 5.9 | 1 hPa at 133 °C |

Nozzle Type | Circle | Elliptical A | Elliptical B |
---|---|---|---|

Major Axis (M) (mm) | 0.160 | 0.170 | 0.189 |

Minor Axis (m) (mm) | 0.160 | 0.142 | 0.135 |

Aspect ratio (M/m) | 1 | 1.2 | 1.4 |

Area (mm^{2}) | 0.02 | 0.019 | 0.02 |

Orifice length (mm) | 1.23 | 1.23 | 1.23 |

Engine Type | 2.2-L Turbocharged DI Diesel Engine | In-line, Turbocharged, Intercooled |
---|---|---|

Cylinder number-Bore × Stroke (mm) | 4-86 × 94.6 | 6-110 × 115 |

Rated Power/Speed (kW/r/min) | 155/3800 | 155/2300 |

Maximum Torque/Speed (N·m/r/min) | 360/1500 | 680/1400 |

Minimum brake specific fuel consumption BSFC (g/kW·h) | 222 | 205 |

The nozzle hole diameter of injectors (mm) | 0.12 | 0.17 |

Boundary | Boundary Conditions |
---|---|

Injection pressure | 50 MPa, 100 MPa, 180 MPa |

Backpressure | 1 MPa, 3 MPa |

Ambient air temperature | T = 300 K |

After start of injection (ASOI) | 0–1 ms |

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## Share and Cite

**MDPI and ACS Style**

Ishak, M.H.H.; Ismail, F.; Che Mat, S.; Abdullah, M.Z.; Abdul Aziz, M.S.; Idroas, M.Y.
Numerical Analysis of Nozzle Flow and Spray Characteristics from Different Nozzles Using Diesel and Biofuel Blends. *Energies* **2019**, *12*, 281.
https://doi.org/10.3390/en12020281

**AMA Style**

Ishak MHH, Ismail F, Che Mat S, Abdullah MZ, Abdul Aziz MS, Idroas MY.
Numerical Analysis of Nozzle Flow and Spray Characteristics from Different Nozzles Using Diesel and Biofuel Blends. *Energies*. 2019; 12(2):281.
https://doi.org/10.3390/en12020281

**Chicago/Turabian Style**

Ishak, M.H.H., Farzad Ismail, Sharzali Che Mat, M.Z. Abdullah, M.S. Abdul Aziz, and M.Y. Idroas.
2019. "Numerical Analysis of Nozzle Flow and Spray Characteristics from Different Nozzles Using Diesel and Biofuel Blends" *Energies* 12, no. 2: 281.
https://doi.org/10.3390/en12020281