The realistic flow on each blade of the front and rear propellers with contra-rotating propellers (CRPs) are most complex because that consist the interaction forces with themselves and it affects to the actual efficiency of the propeller blades. The wake of CRPs at the gap between the front and rear propellers have influent to the variation of propeller performance for the front and rear propellers. So, this paper presented the numerical simulation of propeller performance on CRPs with steady method in the first. Second, it is applied to evaluate the propeller performance with unsteady method in time accuracy including investigating the wake on a transverse plane between the front and rear propellers and a transverse plane located downstream of the rear propeller. The wake was analyzed through velocity vector magnitude contours. The numerical simulations were conducted using the Reynolds Averaged Navier-Stokes (RANS). The calculation results have been compared the measurement data.

Inclined shaft propeller arrangements are demonstrated in the high-speed boat. The flow field around the propeller blades with inclined shaft propeller is unsteady due to the cross-flow component from the influx of the shaft direction which complicated more than the straight shaft propeller condition (without inclined shaft propeller). Therefore, realistic flow around inclined shaft propeller is important to the actual efficiency of propeller. In addition, propeller characteristics such as the pitch, skew and rake are influences to propeller performance, maybe not done in design condition which is different from the straight shaft propeller. This paper offers the investigation of unsteady propeller performance with operating the different inclined shaft angle conditions for Long-Tail Boat (LTB) using a Reynolds Averaged Navier-Stokes (RANS) solver. The unsteady calculations are conducted by inclined flow conditions. The computational results of propeller performance and pressure distribution on the suction and pressure sides at the blades of time-accuracy have been compared to each other including the wake effect behind the propeller. The results can be applied to adjust the inclined shaft angle of the boat.

An ever-increasing demand for electrical power and soaring levels of energy consumption around the world have led to an energy crisis. Thus, this paper aims to review the conventional technologies against those of newer developments in electrical power generation such as using nitrogen generators. The nitrogen generator method is most appealing as it is a seemingly free energy already existing in nature. A nitrogen generator with a 5000 (Nm³/h) capacity has the potential to be used to analyze gas composition and the results are compared with the gas composition of a conventional steam turbine, which is used to pressurize 6000 (kWh) injection steam turbines. The magnetic bearing must be installed in both systems to modify all centrifuged systems which reduces all energy consumption in all systems by more than 50%. Artificial intelligence is used with the machine to analyze and control nitrogen gas flow to provide a more precise evaluation resulting in a more efficient technology. It should further be noted that the nitrogen turbine is superior to the steam turbine because it does not require the burning of fossil fuel to generate power. Hence, it is crucial to modify conventional technologies to improve energy sustainability and begin the long task of tackling environmental issues.

The propeller guard is a device on the long-drive shaft of the Long-Tail Boats, which is significant for preventing the propeller from hitting submerged metal or rocks when the boat runs aground in shallow water. There is also a tab device attached to the propeller guard, it alleviates the lifting force in the vertical axial from the propeller force, when operating an inclined shaft angle while the boat is a high speed. As a result, the stern of the boat does not raise (reducing the boat's stern trim). Therefore, realistic fluid flow through a long-drive shaft and propeller guard kits is important. These affect the actual performance of the propeller. This research paper proposes the numerical evaluation of the propeller performance on a full scale with a long-drive shaft and inclined propeller guard kits using the Reynolds-averaged Navier-Stokes equations (RANS) solver. The SST k-ω turbulence model is adopted to the Reynolds-stress terms in the RANS equations. The computations are performed under oblique flow conditions. The results of propeller performance, pressure distribution, and wake fields around the propeller blades and the propeller guard kits have been examined. The results may be used to optimize the shape and characteristics of propeller guard kits for the Long-Tail Boats.

The Long-Tail Boat (LTB) is a high-speed boat in Thailand. The propulsive system has a long-drive shaft that holds the propeller on the end of the shaft. It is used under inclined shaft conditions because of shallow water draft. Thus, the fluid flow into the propeller blade area is unsteady due to the cross-flow component. Therefore, the long-drive shaft is an important parameter in generating the flow field before entering the propeller blades, which affects propeller efficiency. This paper presents a numerical analysis of the flow field around a long-drive shaft and propeller blade areas in a full-scale propeller size using the Reynolds-Averaged Navier-Stokes (RANS) solver. The unsteady propeller performance is carried out by considering inclined flow conditions. In addition, the computational results of fluid flow in terms of the pressure distributions and wake fields around a long-drive shaft and propeller are investigated, which influence the propeller performance and the generating drag forces by a long-drive shaft. The results can be applied to modify the long-drive shaft of boats. Highlights The Long-Tail Boat (LTB) is a local vessel in Thailand that has a high speed Computational fluid dynamics (CFD) code ANSYS Fluent to study the effect of a long-drive shaft propeller with inclined shaft angles The long-drive shaft should be designed in suitable for operating the inclined shaft conditions because it will directly affect the propeller efficiency