Abstract: The internal combustion and friction of the moving parts of ship machinery generate a great amount of heat, leading to the increase of the running temperature, which should be kept within the maker permitted thresholds. This is ensured by the ship cooling system, which consists of two independent systems, i.e. fresh water-cooling system and seawater cooling system. The seawater cooling system plays a vital role in the normal function of ship machinery. Its failure leads generally to the overheating of the running equipment, causing its breakdown and may lead to disastrous maritime accidental events. Therefore, this system must be reliable and continuously available to ensure the normal operation of the engine room equipment. In this paper, we use the Bayesian Network Analysis to evaluate the commonly used conventional seawater cooling system to identify the weak system components in order to enhance their reliability and to propose an improved system with enhanced automation, that may be fitted onboard of autonomous ship.

Abstract: This study aims at evaluating stress on piston, connecting rod, and the crankshaft of the 4-stroke diesel engine due to compressive and thermal loads. The study applied the finite element method, the design was made using CATIA V5, and analysis was carried out in steady-state using ANSYS R15. Mechanical and thermal compressive loads were applied based on the actual combustion chamber condition. The focus of this study was set up by determining the reference points of observation. The research variable used different types of material for each component. The piston used alloy cast iron, AlSi12 CuNiMg Forged and AlSi18 CuNiMg casting. Connecting rod used AISI 1045 steel, 42CrMo and alloy cast iron. Crankshaft uses AlSi18 CuNiMg casting, AISI 1045 steel and alloy cast iron. The study results showed the maximum stress depending on the material type which had different properties. Piston experienced thermal and compressive loads so that maximum stress influenced by the young modulus and the thermal expansion coefficient of the material. The maximum piston stress occurred in alloy cast iron material in the piston pin area. Connecting rod and crankshaft received a lot of mechanical compressive load, and the young modulus value was the most influential thing on the stress that occurred. The connecting rod experienced the highest stress in the big end area of the 42CrMo material. Crankshaft experienced the highest stress in the crank journal fillet area on AISI 1045 material.

Abstract: The influence of chemical treatment of sisal fibres through the subsequent processes of mercerisation (alkali treatment), then silane treatment and eventually acid hydrolysis on the fibres were investigated. The effect of the treated fibres on the tensile and flexural properties of their composites with epoxy resin were also studied. Scanning electron microscopy examination of the treated and untreated fibres showed that the subsequent processes of chemical treatment enhanced the removal of surface impurities and therefore increased the roughness of the fibre surfaces. It was concluded that this would avail an increased surface area on the fibre for interlocking with matrices and would therefore enhance adhesion of the two. Consistent to this conclusion, subsequent testing of treated fibre reinforced composites gave rise to higher values of tensile and flexural strength and stiffness than the untreated fibre reinforced composites.

Abstract: The present study has investigated numerically the effect of a circular cylinder diameter installed at the side of the advancing blade on the performance of vertical axis Savonius water turbine. The 2D simulation in the Gambit and Fluent Ansys 17.0 software has been performed by using the technique of the moving mesh and the realizable k-epsilon turbulence model, to compare the Savonius turbine performance between without (conventional turbine) and with a circular cylinder installed at the side of the advancing blade. The numerical validation is done by comparing the result with published experimental data. In this phase, the parameter used is the torque coefficient on the air fluid by varying the three meshes from coarse to fine. Then, after the numerical validation is reached, the working fluid in the simulation will then be converted to water, then the ratio of the diameter of the circular cylinder and the Savonius turbine varies ds/D = 0.1, 0.3, 0.5, 0.7 and 0.9. The flow visualization show that placing the circular cylinder beside of the advanced blade will reduce the pressure and increase the velocity attached on convex advancing blade. The results show that the highest power coefficient (Cp) occurs at ds/D = 0.7 and TSR = 0.7, where the increase in Cp can reach more than 28% compared to the conventional one.

Abstract: This paper aims to evaluating a new ventilation concept: displacement ventilation (DV) aided with personalized ventilation (PV) which is assessed for improving indoor air quality. This approach could be improved ventilation system design that could even provide individual control of indoor microclimate. The airflow motion and temperature distribution by adopting DV and PDV(personal-displacement ventilation) systems investigated experimentally and numerically with best flow rate from personal ventilation and best situations of occupant distribution for DV and PDV. This work includes a discussion of ventilation strategies, air and temperature distribution including personal-displacement ventilation (PDV) system in office room under Iraqi climate to predict Indoor Air Quality (IQA) and thermal human comfort by using computational fluid dynamics (CFD) modeling and rigorous validation experiments. The experimental study was performed to investigate how the use of the two different arrangement would effect on thermal environment inside a tested room of dimensions (3×1.75×3) m used as an office room. The results of the experimental study were used to validate the CFD simulations. The boundary conditions for Computational Fluid Dynamics (CFD) study were obtained from the same set-up measurement for one way direction-rectangular displacement and personal ventilation system. RNG, k-ε turbulence models are evaluated to show how the shape and location of ventilation devices and occupant would affect the air quality and thermal environment in the room. The supply air device has been chosen according to the data provided by manufactures depending on supply airflow rate in order to avoid drafts. For DV supply temperature of 18◦C (64.4◦F) and PV air supply temperature range of 18◦C to 22◦C (64.4◦F to 71.6◦F), it was found that PV at flow rate 10 L/s (21.19 cfm) in addition to the distribution of occupants could improved the inhaled air quality in the breathing zone. And that the arrangements at an office room for the air supply diffuser DV and PV combined give accepted thermal human comfortable depending on the magnitude of air distribution performance index (ADPI) and effectiveness temperature(ɛt) which are improved about 71% and about 1.8 respectively

Abstract: The dual fuel system is a new concept to reduce the use of fossil fuels. However, dual fuel engine performance is still experiencing a decline and an increase in CO and HC emissions. The reason is the introduction of CNG through the intake manifold so that it disrupts the amount of air entering the cylinder so that the combustion process is interrupted. Thus the correct CNG injection timing is needed to improve combustion processes and reduce the emissions. This research was conducted experimentally on a CPO biodiesel-CNG dual fuel engine, which is equipped with an electric supercharger to increase the amount of air supply. The research parameter is CNG injection timing from 700 to 1500 CA ATDC with 200 intervals, which is set on a programmable ECU, at different engine loads. The results showed that the CPO biodiesel fuel as a pilot had a positive impact on the ignition delay on dual fuel engines because it had a higher cetane number and oxygen content. Then by optimizing injection time of 1100 CA ATDC on dual fuel engines, especially high loads resulting in a significant increase in-cylinder pressure and heat release rate of 6.4% and 41.7% as well as a decrease in ignition delay and duration of combustion by 8.2% and 26.7%. The combustion performance is higher compared to a single fuel engine. Likewise, CO and HC emissions decreased by 21.4% and 11.8%, although the value was still above single fuel, while PM emissions were lower than single fuel.

Abstract: Different requirements from the gas turbine engines have to be fulfilled by modern control systems, like unburden the operator of any engine specific control, limiting tasks, reduce the engine fuel consumption, maximize the mechanical power, and follow the operator's commands as fast as possible with safe and reliable operation. Two control system models were developed to control the behaviors of the gas turbine engine. The first controller model is the power controller model, which is responsible on governor the net mechanical power created from the engine and make the system reaches its steady state region as soon as possible without cares for any critical exceed points, like the temperature overshooting, transient acceleration, and uncontrolled pressure rising. The second controller model has a temperature controller loop, which is added to the power control loop to control the temperature rising due to the power controller action within a limiting value. The temperature controller loop programmed to operate only at the abnormal operating conditions, i.e. when the engine temperature exceeds the allowable critical point. The power-temperature controller model has Multi Input- Single Output (MISO) type, where the input to the controller is the feedback power and temperature singles, while the fuel valve position is the single output signal. The control system changes the fuel flow according to the engine demands by changing the value of the fuel valve angle. The auto selector was added to pass critical controller signal and ignore the other. Mathematical modeling of real-life systems is very much needed for simulation and controller design. The linearized thermodynamic equations are based on the first engineering principles utilizing algebraic equations for the thermodynamic processes and differential equations of motion to model the dynamic nature of the system. The two controller models are going to simulate by Matlab\Simulink software under different types and values of excitation. The responses of the main effective parameters of gas turbine engines and the relationship between these parameters and the fuel flow rate will present later.

Abstract: The Muara Tawar Power Plant is located on the coast of Bekasi, which is part of the Jakarta Bay area, Indonesia. There are plans to conduct sea reclamation around the Muara Tawar Power Plant and build it as a port and industrial area. The objective of this paper is to analyze the effect of reclamation on the performance of the Muara Tawar Power Plant steam turbine, which uses seawater as a condenser cooling medium. The intended performance is condenser pressure, steam turbine output power, and system efficiency. Changes in seawater temperature are simulated using Computational Fluid Dynamic software, Ansys Fluent version 19.1. The performance of the steam turbine is simulated using Cycle-Tempo software. The results showed that after reclamation there was an increase in the mean seawater temperature of the region as 2.04 °C, i.e., from 30.43 °C the water temperature measured before reclamation became 32.47 °C after reclamation. This condition has an impact on increasing the percentage of condenser pressure around 10.7%, which results in a reduction in the percentage of output power by 0.35%, and in general, also giving a reduction in the efficiency percentage of the Muara Tawar Power Plant around 0.35%.

Abstract: This paper presents a model for the evaluation of the optimal design of Darrieus vertical axis wind turbine by CFD analysis and experimental tests, through analyzing six models of Darrieus wind turbines, number of blades and tip speed ratio. For this purpose, a full investigation campaign has been carried out through a systematic comparison of numerical simulations with wind tunnel experiments data. The airfoil profile used in the turbine blades was DU06W200 and constant geometry dimensions to turbines. The experiments were done for all Darrieus wind turbine models by using a subsonic wind tunnel under open type test section with airflow speed range (3-7.65) m/s and different tip speed ratio TSR. The results show that Darrieus WT straight type can be self-starting at the wind velocity 3 m/s, where other types cannot be starting at less than wind speed 5 m/s. The rotational speed (N) increases for all models with the wind velocity increase. The power coefficient (CP) increases when the TSR increases at experimental results for all models. The performance of Darrieus WT with 2 blades rotor is better than other models. At low wind velocity (3 m/s) the value of CP (0.2495), the CT (0.174), the rotational speed (198 rpm) and can be self-starting at this wind velocity.

Abstract: The applications of titanium alloys are widely used for aerospace industry as this material possess light weight, high strength, and excellent corrosion resistance. However, this material has shown poor machinability with traditional cutting operations. This is one of the reasons why alternatives operation was investigated. The trading-off between attaining high productivity and meeting the demanding requirements on high surface finish are the biggest challenges for wire electrical discharge machining (WEDM) to become alternative operation for cutting. Both productivity and surface quality are key performance evaluation in the WEDM operation, however, they are always conflicting with each other. Therefore, the present study highlights the application of a generic algorithm (GA) to obtain optimal cutting parameter for high productivity and fine surface finish simultaneously. In this study, the productivity is identified through the term material removal rate (MRR) and the quality surface finish is identified by arithmetic average surface roughness value. The results revealed that parameter voltage has strong influence on the surface roughness with a contribution 73.06% and table feedrate dominated other parameters with 86.16% contribution to the MRR. The optimized parameters yield 0.957 mm³/min for MRR and 0.167 µm for surface roughness as the value predicted and recommended by GA.

Abstract: Condensate Extraction Pump (CEP) plays an important role in feeding water requirements for Boiler and Turbine operations. CEP is the main component in a condensate water system that serves to pump condensate water from hot well to deaerator. The CEP performance of Labuan power plant, Indonesia, has significantly dropped which is likely due to cavitation. Cavitation can be prevented by ensuring that the pressure in the suction pipe (before entering the pump) must be above the saturated vapor pressure at working temperature. Maintaining the pressure in the suction pipe so that it is not lower than the saturated vapor pressure; one of which is by designing the suction pipe installation such that it does not cause many head losses, so that it produces a pressure that is still high enough at the end of the suction pipe near the pump inlet. This is the objective of this present study, wherein this study the modifications of existing suction pipe installation will be carried out, in an effort to avoid CEP from the dangers of cavitation. There are two ways to reduce the head losses in the suction pipe conducted in this study, namely (i) by uniformity the overall pipe diameter, this is to avoid the effect of diffuser and/or nozzle in changes in pipe diameter that can increase minor head losses, (ii) by changing the junction angle from a large angle to a smaller angle, it is clear that with a smaller angle will increase the streamline at the confluence of two streams with different vector directions. Numerical simulations were carried out to analyze the stated problems above using Computational Fluid Dynamic software, Ansys Fluent version 19.2. The simulation results show that for all variations tested in this study, head losses increase with increasing total mass flow rates. By uniformizing the diameter of the suction pipe, which is 630 mm, and changing the intersection or junction angle from 90° to 45° have been proven to have succeeded in giving the lowest head loss in the suction pipe. In the maximum mass flow rate, of 263.88 kg/s, the total head loss of the existing model is 1.91 meters, model-1 is 1.92 meters, model-2 is 1.88 meters and Model-3 is 1.91 meters. Thus, model-2 promises the smallest risk of cavitation in CEP and certainly will increase the reliability of the Labuan Power Plant, Indonesia.

Abstract: Excessive vibration can shorten the life of high-cost engine components. Moreover, given that vibration is unavoidable, procedures to control and reduce its effect are proposed in this paper. In this study, the vibration characteristics of a cantilever plate structure excited with piezoelectric actuator elements attached to the top and bottom surfaces of the plate were investigated. The piezoelectric actuators were attached to the plate in two different configurations: straight (parallel to the axis of the plate) and angled (at an angle of 45o to the axis of the plate). In this study, a finite element modal analysis of the cantilever plate structures was conducted using ANSYS to determine the mode shapes of the plate under investigation. The effect of exciting the piezoelectric actuators to counteract the deflections detected by the modal analysis of the plate was then evaluated. Based on the analysis results, it was concluded that piezoelectric actuators can be used to overcome the effects of different modes of cantilever plate vibration.

Abstract: Stagnation point MHD flow of a viscoelastic nanofluid over a stretching cylinder with temperature-dependent dynamic viscosity is studied. Heat transfer is characterized by Cattaneo-Christov heat flux and temperature dependent thermal conductivity. The nonlinear governing equations with velocity slip and thermal slip boundary conditions are redacted and transmuted into dimensionless forms by similarity transformations to obtain a set of coupled non-linear ordinary differential equations which are accordingly solved via the Spectral Quasi-linearization method (SQLM). The usual heat source parameter is used and a new one emerges from the heat generation/absorption body force through mathematical derivation from first principle. The upshots of the engrafted flow parameters on the dimensionless velocity and temperature profiles, as well as on the skin friction coefficient are analysed. Obtained outcome shows that increasing values of the curvature parameter and viscoelastic parameter enhances fluid velocity but nanoparticle volume fraction slows it down. Temperature quashes for larger values of thermal relaxation parameter, indicating that the non-Fourier heat flux model produces lower temperature within the flow system than that of the Fourier law. However, the nanofluid temperature is raised by increasingly varying values of heat generation parameter. The skin-friction coefficient exhibits an increasing behaviour against both curvature and viscoelastic parameters.