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A numerical and experimental study of marine hydrogen–natural gas–diesel tri–fuel engines

Zhao Rui, Xu Leping, Su Xiangwen, Feng Shiquan, Li Changxiong, Tan Qinming, Wang Zhongcheng

Polish Maritime Research

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2020

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nr 4

80--90

EN

Maritime shipping is a key component of the global economy, representing 80–90% of international trade. To deal with the energy crisis and marine environmental pollution, hydrogen-natural gas-diesel tri-fuel engines have become an attractive option for use in the maritime industry. In this study, numerical simulations and experimental tests were used to evaluate the effects of different hydrogen ratios on the combustion and emissions from these engines. The results show that, in terms of combustion performance, as the hydrogen proportion increases, the combustion ignition delay time in the cylinder decreases and the laminar flame speed increases. The pressure and temperature in the cylinder increase and the temperature field distribution expands more rapidly with a higher hydrogen ratio. This means that the tri-fuel engine (H2 +CH4 +Diesel) has a faster response and better power performance than the dual-fuel engine (CH4 +Diesel). In terms of emission performance, as the hydrogen proportion increases, the NO emissions increase, and CO and CO2 emissions decrease. If factors such as methane escape into the atmosphere from the engine are considered, the contribution of marine tri-fuel engines to reducing ship exhaust emissions will be even more significant. Therefore, this study shows that marine hydrogen-natural gas-diesel tri-fuel engines have significant application and research prospects.

2

Microcellular Oblate Propellant with Skin-core Structure Deterred by Poly(neopentanediol adipate)

Ding Yajun, Ying Sanjiu, Xiao Zhongliang, Wu Wenlong, Li Chunzhi, He Yun

Central European Journal of Energetic Materials

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2020

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Vol. 17, no. 1

49--65

EN

In order to solve the issues of high muzzle flash, smoke, residue, migration rate and carcinogenicity of double-base oblate propellants deterred by dibutyl phthalate (DBP), skin-core structure microporous oblate propellants to replace DBP deterring technology were fabricated in the present work by supercritical carbon dioxide (SC-CO2) foaming technology. Poly(neopentanediol adipate) (NA) was employed as the deterrent to modify the combustion properties because of ist lower migration rate in storage. Scanning electron microscopy (SEM) was used to observe the morphology of the microporous oblate propellants generated by different processing conditions, and the combustion properties were investigated by closed bomb tests. The SEM images indicated that the skin region displayed smaller cell diameters and lower cell density compared with cells in the core region. The closed bomb tests demonstrated that it was feasible to adjust the progressive combustion performance by controlling the skin-core structure and the NA deterred layer. The burning time values of the original, the microcellular, and the NA deterred samples were 3.45, 2.14, and 4.20 ms, respectively. Microcellular oblate propellants, with a skin-core structure foamed by SC-CO2 and deterred by NA, provides a novel and promising method to realize progressive combustion performance.

3

Novel High-Nitrogen Content Energetic Compounds with High Detonation and Combustion Performance for use in Plastic Bonded Explosives (PBXs) and Composite Solid Propellants

Keshavarz M. H., Abadi Y. H., Esmaeilpour K., Damiri S., Oftadeh M.

Central European Journal of Energetic Materials

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2018

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Vol. 15, no. 2

364--375

EN

Five novel high-nitrogen content (N>50%) derivatives of tetrazole are introduced in the study reported here. The assessment of various properties of these compounds were performed, which include physicothermal properties (crystal density, condensed phase heat of formation, melting point, enthalpy of fusion and entropy of fusion), detonation performance (velocity and pressure of detonation, detonation temperature and power), sensitivity with respect to external stimuli (impact, shock, friction and electric spark) and combustion performance (specific impulse). The predicted results of these compounds are compared with dihydroxylammonium 5,5’-bistetrazole-1,1’-diolate (TKX-50) and octanitro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) as a high performance ionic salt and a neutral explosive, respectively. The novel energetic compounds were found to have higher detonation and combustion performance than either TKX-50 or HMX. The new explosives are therefore good candidates to obtain high detonation and combustion performance in plastic bonded explosives (PBXs) and composite solid propellants, respectively.

4

Ignition and Combustion Performance of the Primary Condensed-phase Combustion Products from Boron-based Fuel-rich Propellants

Liu L.-L., He G.-G., Wang Y.-H., Hu S.-G.

Central European Journal of Energetic Materials

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2017

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Vol. 14, no. 2

448--460

EN

The primary condensed-phase combustion products of a boron-based fuel-rich propellant were ignited using a high-power CO2 laser in a pressurized and windowed combustion chamber under variable pressure. The ignition and combustion performances were characterized using an ultraviolet-visible spectrometer and a high-speed camera. The experimental results showed that the combustion of the condensed-phase combustion products originate from the combustion of carbon, and boron may not take any part in the combustion process because of the formation of a thick boron oxide coating and agglomeration after the primary combustion process. Both particle size and the ingredients play an important role in the combustion reaction of the condensed-phase products. It was observed that a lower particle size and a higher boron carbide content are beneficial for the combustion reaction of the products; higher primary and secondary combustion pressures clearly improved the secondary combustion efficiency of the propellant in the combustion reaction.

5

Combustion Characteristics and Mechanism of Boron-based, Fuel-rich Propellants with Agglomerated Boron Powder

Xu H. -X., Pang W.-Q., Guo H.-W., Zhao F.-Q., Wang Y., Sun Z.-H.

Central European Journal of Energetic Materials

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2014

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Vol. 11, no. 4

575--587

EN

In order to extend the burning rate of boron-based, fuel-rich solid propellants with agglomerated boron powder, the effects of the boron content, the AP content, and of the magnesium powder content, on the burning rate and pressure exponent have been studied systematically. It has been shown that when the AP content is constant, the burning rate of the propellants increases with an increase in the agglomerated boron content. Furthermore, the burning rate and pressure exponent increase with increasing the contents of AP and magnesium powder. By means of single colour frame amplification photography and combustion wave tests, the combustion mechanism of these propellants has been investigated. It has been shown that the flame of the propellants becomes brighter by increasing the AP content, the dT/dxcp and dT/dxgp of the propellant FR-5 being around 6815 and 5789 °C/mm respectively, higher than those of FR-4, resulting in greater burning rates. The Ts of these propellants is above 683 °C, which is higher than the decomposition peak temperatures of agglomerated boron powder and of propellants (about 649 °C), which indicates that agglomerated boron powder is partially oxidized on the combustion surface, and the heat released from it may be beneficial to the combustion of the propellants.