Elsevier

Energy

Volume 179, 15 July 2019, Pages 1082-1093
Energy

Properties effect of blending fischer-tropsch aviation fuel on spray performances

https://doi.org/10.1016/j.energy.2019.04.157Get rights and content

Highlights

  • The relationship between FT fuel properties and spray characteristics is discussed.

  • 75% mass fraction is considered acceptable for China's FT fuel.

  • The empirical formulas for FT and the blends are presented with a high precision.

Abstract

The physical properties of fuels have significant impact on the spray performances. Fischer-tropsch (FT) aviation fuel is mainly composed by paraffins compared with Chinese jet fuel (RP-3). Difference in composition determines the differences in physical properties. Spray characteristics of FT and the blends were investigated downstream of a pressure swirl nozzle exit at different injection pressures and compared with those of RP-3. The liquid length and the spray cone angle of FT fuel are up to18.2% and 6.75% higher than RP-3, respectively. In the area where the axial distance from nozzle exit is less than 10 mm, FT fuel has a higher droplet size and droplet velocity than RP-3. A reflux zone is observed in the hollow cone downstream the nozzle. The droplets' droplet diameter and velocity of FT fuel are 53.32% and 49.74% bigger than those of RP-3 in the reflux zone, respectively. The presence of the reflux zone is also believed to be responsible for the higher local droplet concentration in the spray. The spray performances of the blends containing 75% FT is close to that of RP-3. The differences in spray performances between the fuels are consistent with the expectation based on differences in physical properties.

Introduction

Increasing concern with respect to the growing energy demand and environmental protection drive the need for clean, alternative energy. The transportation industry, especially commercial aviation business, is playing an increasingly important role in energy consumption. According to forecast, 1950 freighter aircraft, of which 730 new build freighter aircraft will be needed by 2036 [1]. Gases and particles emitted by the aircraft could alter the concentration of atmospheric greenhouse gases including CO2, O3, CH4 and water vapor [2]. As a result, the interest in alternative aviation fuel is growing dramatically. Fuel derived from the fischer-tropsch process, owing to the near absence of aromatic and nitrogen, sulfur and other contents which could cause environmental damage in the composition, is treated as a possible alternative fuel in the near future. However, in order to be used as drop-in fuel, the characteristics of FT fuels have to meet the demanding requirements of the gas turbine engines for reliability and safety. In this situation, properties of FT fuel need to be thoroughly studied. Fully Synthetic Jet Fuel (FSJF), a coal-to-liquid fuel produced by Sasol, is known as the first fuel that can pass all the ASTM D7566 requirements. Studies on performances of FSJF have been carried out [[3], [4], [5]]. The results show that the properties and characteristics of Sasol FSJF fall within the experience of conventional jet fuels from petroleum. Zhao et al. [6] analyzed the atomization performance and thermogravimetric of coal-based fischer-tropsch synthetic fuel made in China, they reported that the average sauter mean diameter (SMD) and Burnout index of coal-based synthetic fuel are 9.4% smaller and 9.0% greater than those of RP-3 with a difference of approximately. Yang et al. [7] also investigated basic combustion performances and range of Chinese FT alternative fuel and reported that the FT fuel’ s lower density and higher calorific value lead to its range shortened by 2.1%. However, more researches needed to be done to thoroughly analysis the performances of Chinese FT fuel.

It is known that the combustion performance of fuels, which has a great influence on the performance of aero engines, is mostly decided by the spray characteristics of fuels. Macroscopic spray characteristics such as spray cone angle and liquid length determine the distribution of fuel in the combustion chamber, microscopic spray characteristics such as SMD and velocity of droplets have a significant impact on the combustion characteristics of the fuel. Differences of physical properties of fuels have an important effect on the atomization performances. Therefore, it is necessary to thoroughly understand how the physical properties effect the atomization characteristics. Studies on atomization have been carried out. Saha et al. [8] studied the breakup and coalescence characteristics of a hollow cone swirling spray, the effects of Reynolds number and Weber number in the liquid breakup regimes were presented in their study. Sivakumar et al. [9] investigated the atomization characteristics of aviation biofuel from a simplex swirl atomizer, they reported that the trend of SMD variation with axial distance is influenced by the atomizer flow conditions. Gan et al. [10] tested the effect of linear alkane C17, C18 on spray characteristics of jet fuel, the results show that a narrowed spray cone angle and decreased SMD were caused by additional linear alkanes. Kannaiyan et al. [[11], [12], [13]]also did considerable research on the atomization performances of synthetic alternative fuels. Comparing to the entire combustion chamber with a complex flow field, changes in fuel properties has a greater effect near the nozzle exit. However, far too little attention has been paid to discuss the differences of spray field near the nozzle exit caused by the different physical performances of FT fuel, especially flow details of the reflux zoon downstream the nozzle exit.

The objective of this study is to better understand the details of the atomization field of FT fuel near the nozzle exit and to get more insights information on the influence of fuel properties on spray reflux zoon. For this reason, this paper focuses on the macroscopic and microscopic spray characteristics of FT fuel near the nozzle exit, and attempt to relate fuel properties to their atomization performance through empirical formulas of SMD, cone angle and liquid length. Some researchers have been reported that the atomization performances of different fuels is very similar under high injection pressure [6,10], so the main objective of this study is to observe the differences of atomization performances between different fuels under low injection pressure.

Section snippets

Experimental details

Chemical components of FT fuel are different from those of conventional jet fuel due to the differences in the feedstock and refining process. As a result, both the chemical and physical performances could be different between FT fuel and conventional jet fuel. This study measured physical properties that may affect atomization performance such as density, viscosity and surface tension to help figure out how chemical components influence spray performances.

Fuel composition

Chemical compositions of RP-3 and FT fuel were investigated and shown in Fig. 4. Fig. 4 (a) classified the main components of RP-3 and FT fuel. About 70% of RP-3 is made up of normal straight chain (36.1%) and branched chain alkanes (33.5%), the remaining 30% are consisted by cyclo-paraffins (10.0%), aromatic (16.1%) and other components including polyaromatics. In contrast, the content of n-paraffins (76.8%) and iso-paraffins (22.9%) in FT fuel is close to 99% due to the characteristics of the

Conclusions

This work focus on the differences of macroscopic and microscopic spray performances between FT fuel and Chinese jet fuel RP-3 in a pressure swirl nozzle. The photographic measurement results show that both the maximum differences of the liquid length and the cone angle between fuels appear at the injection pressure of 0.1 MPa, where the liquid length of FT is 18.2% lower and the cone angle of FT fuel is 6.75% higher than those of RP-3, respectively. The results of the PDA measurement show a

Acknowledgement

This paper was supported by National Key Research and Development Program-International Cooperation Innovation-China (2016YFE0120100)

References (29)

  • R. Bhagwan et al.

    An experimental comparison of the emissions characteristics of standard jet A-1 and synthetic fuels

    Flow, Turbul Combust

    (2014)
  • G. Zhou et al.

    Combustion performance and range of coal-based fischer-tropsch aviation fuel

    J Beijing Univ Aeronaut Astronaut

    (2016)
  • A. Saha et al.

    Breakup and coalescence characteristics of a hollow cone swirling spray

    Phys Fluids

    (2012)
  • Z. Gan et al.

    Effect of linear alkane C17, C18 on spray characteristics of kerosene in hollow cone pressure swirl spray

    Atomization Sprays

    (2017)
  • Cited by (8)

    • Recent advancements in catalytic conversion pathways for synthetic jet fuel produced from bioresources

      2022, Energy Conversion and Management
      Citation Excerpt :

      It has been found that controlling aromatic content within the range of 10–20 vol% is desirable, but this may also be influenced by the seal material [58]. The typical chemical compositions of Jet A-1 fuel and biojet fuels are shown in Table 4 [25,90]. The jet fuel composition varies depending on the production pathway and feedstock used.

    • Effects of the physical properties of fuel on spray characteristics from a gas turbine nozzle

      2020, Energy
      Citation Excerpt :

      presented a procedure to design and verify the experimental behavior of pressure swirl atomizer using water which is used for gas turbine nozzle design procedure. However, variation of physical properties of injection fluid leads to the different spray characteristics [10]. Therefore, to evaluate the performance of the nozzle, it is important to investigate the effect of variation of fluid physical properties.

    • A study on aviation fuels measuring spray quality

      2020, Materials Today: Proceedings
      Citation Excerpt :

      The increasing demand for alternative fuel leads to all types of turbine engines as well as aviation. Fuel processing technologies provided many solutions, Fischer-Tropsch (FT) process among them to develop distilled fuel components [7]. FT process can develop anything to liquid that provide many possibilities to generate synthetic fuels or conversion to efficient quality of fuels.

    View all citing articles on Scopus
    View full text