“Abstract

Microalgae oil (MAO), a third-generation biofuel, can support global transportation fuel demand as a fossil fuel substitute. Schizochytrium sp. MAO is particularly promising for direct use in compression ignition (CI) engines, especially in the marine sector, due to its adaptability and high oil yield. This study investigated the performance, emissions, and optimization of a single-cylinder marine diesel engine operating on MAO and MAO/diesel oil (DO) blends. The results show that MAO significantly reduced nitrogen oxide (NOx) and carbon monoxide (CO) emissions by up to 59%, despite its higher viscosity and density and its lower heating value compared with DO. Brake-specific fuel consumption (BSFC) increased by 46%, but brake power and brake thermal efficiency (BTE) decreased by up to 40% and 26%, respectively. After 30 h of operation, the lubricant oil (LO) in MAO-fueled engines contained 15% less Zn, 19% less P, and 16% less Ca than that in DO-fueled engines.”

 

The full report is accessible via: https://doi.org/10.1002/bbb.70058

For related publications please see Resources – UK National Clean Maritime Research Hub

“Abstract

Dual-mode propellers, as propulsion and turbine devices, have found widespread application in renewable energy systems for marine vehicles, particularly in sailing boats and yachts. However, the existing dual-mode propellers in these contexts are typically chosen in an off-the-shelf manner, indicating a lack of hydrodynamic optimisation to enhance both the propulsion and energy generation efficiency in the same rotor. To address this limitation and furnish scientific validation of the design of a dual-mode propeller turbine rotor optimised to achieve a balanced performance in both propulsion and energy generation, rigorous experimentation was conducted using specialised software, Rotorysics 2019, and a case study vessel, the Princess Royale. Utilising prior experimental data for this propeller turbine, code validation was undertaken to ensure accurate prediction of the effects of the pitch, blade count and expanded area ratio on the performance in both modes. With the intention of achieving optimal power generation and propulsion efficiencies in conjunction with a single rotor, the findings reveal that the optimised fixed-pitch propeller exhibits dual functionality. They serve as both propulsion and tidal/current turbines with balanced efficiency. They are particularly suitable for low-speed vessels such as yachts anchored in currents or for sailboats utilising a propeller as a towed turbine. Through thorough testing and analysis, the concept of a dual-mode propeller turbine was feasible. Analysing them separately, in terms of the propulsion, the best geometry found through numerous tests of different expanded area ratios, blade number, pitch and speed was the 3-blade, 0.6 pitch ratio, which achieved a propulsive efficiency of 54.33% (0.5433204) and a power coefficient of 0.291843. Conversely, if the focus was on power generation while maintaining excellent propulsive efficiency, the optimal geometry would be the 5-blade, 0.6 pitch ratio, which offers a power coefficient of 0.348402 and a propulsive efficiency of 48.55% (0.48547). However, when using both power generation and propulsion as the criteria, the 5-blade, 0.6 pitch ratio, with an EAR of 0.387142, is superior, with balanced optimisation, offering a propulsive efficiency of 52.53% (0.52527) and a power coefficient of 0.319718. As expected, this encompasses a higher blade number for increased power generation efficiency and a higher pitch ratio for increased propulsive efficiency.”

 

The full report is accessible via: https://doi.org/10.3390/en17133138

For related publications please see Resources – UK National Clean Maritime Research Hub

“Abstract

The numerical work presented in the paper investigates the effect of pressure pores on hydrodynamic and hydroacoustic performances. This research aims to reduce cavitation area and underwater noise by mitigating the tip vortex cavitation. Compared to the few studies devoted to the pressure pores technique, several configurations based on the E779A marine propeller have been tested by considering different azimuthal and radial step values, a wider pore region concentrated at the top of the blade, and several pore diameter values. In addition, a numerical simulation was started to verify the effectiveness of the theoretical models in detecting the effect of pressure pores on the acoustic propagation generated by the propellers tested. The numerical approaches combining cavitating flow and noise propagation are performed using a hybrid method, which solves the Ffowcs Williams-Hawkings (FW–H) equation. A validation of the numerical simulation is carried out for cavitating and non-cavitating cases. Open water performances, cavitation area, sound pressure levels, and thrust distributions are analysed for two cavitation numbers. σ= 1,763 and σ= 1,029. The obtained results reveal that the cavitation area decreases as the pressure pore radius increases, but a slight reduction in propulsive efficiency accompanies this. Particularly for the pores radius of 0,00264D, propeller efficiency loss doesn’t exceed 2,6 % and 4,05 % for the two cavitation numbers investigated. Nevertheless, this configuration showed better acoustic performances with a diminution of 10 dB in overall sound pressure level compared to the propeller without pressure pores.”

 

Belhenniche, S.E. et al. (2024) ‘Effect of pressure pores size on hydrodynamic and hydroacoustic marine propeller performances under cavitating case’, Ocean Engineering, 307, p. 118164. doi:10.1016/j.oceaneng.2024.118164.

The full report is accessible via:https://doi.org/10.1016/j.oceaneng.2024.118164