Hamidon Salleh

Spray Characteristic of Diesel-Water Injector for Burner System

NOx and PM are the major product results from the combustion of diesel either in internal combustion engine or external burner system. Thus, the emulsification concept from diesel and water were studied with focusing in controlling of combustion process in order to minimize the harmful emission. The main purpose of this research is to investigate the effects of diesel-water emulsification on mixture formation, burning process and flame development in burner system. The studied parameters include equivalent ratio, water content in diesel-water emulsification and spray characteristics such as spray penetration length, spray angle and spray area. The spray image of different diesel-water ratio and equivalence ratio can be investigated by direct photography method with a digital camera. The real spray images with the time changes was analyzed and compared with based diesel fuel. The results show that the higher of water contents due to higher viscosity influences the higher penetration length and lower spray angle thus predominantly the lower combustible mixture and lower the flame penetration.

Assessment of URANS and DES for Prediction of Leading Edge Film Cooling

This paper describes the assessment of CFD simulations for the film cooling on the blade leading edge with circular cooling holes in order to contribute durability assessment of the turbine blades. Unsteady RANS applying a k-epsilon-v2-f turbulence model and the Spalart and Allmaras turbulence model and detached-eddy simulation (DES) based on the Spalart and Allmaras turbulence model are addressed to solve thermal convection. The CFD calculations were conducted by simulating a semicircular model in the wind tunnel experiments. The DES and also the k-epsilon-v2-f model evaluate explicitly the unsteady fluctuation of local temperature by the vortex structures, so that the predicted film cooling effectiveness is comparatively in agreement with the measurements. On the other hand, the predicted temperature fields by the Spalart and Allmaras model are less diffusive than the DES and the k-epsilon-v2-f model. In the present turbulence modeling, the DES only predicts the penetration of main flow into the film cooling hole but the Spalart and Allmaras model is not able to evaluate the unsteadiness and the vortex structures clearly, and overpredict film cooling effectiveness on the partial surface.

Numerical Study on Flat Plate and Leading Edge Film Cooling

This study describes a 3-D computation for film cooling effectiveness investigation using Fluent commercial code, version 6.2. Two configurations are examined: (1) Flat plate, and (2) Semi-cylindrical leading edge with a flat after-body. Three different RANS turbulence models and DES based on Spalart-Allmaras model are utilized to see the difference in accuracy between DES and RANS approaches. Similar to the previous RANS simulation, lateral spreading of film cooling is under-estimated in the RANS simulation, while in the DES, lateral spreading of film cooling is enhanced and shows adequate agreement with the previous experiments. The effects of velocity magnitude and orientation of plenum flow on film cooling effectiveness are also studied in the flat plate configuration. The plenum flow is eventually found to have a strong impact on the flow structure in the cooling pipe, and the distorted velocity profile in the pipe consequently lowers film cooling effectiveness, in particularly at high blowing ratio.Copyright

Development of the Premixing Injector in Burner System

Today, global warming is the biggest issues due the increasing of emissions from diesel fuel in transportation and manufacturing sectors [1-. The solution for this issue is by using Biodiesel fuel as alternative fuel in both sectors. Malaysia government has introduced the Biodiesel (B5) in the diesel engine for transportations [3]. Biodiesel fuel (BDF) in alternative fuel and renewable energy but it has low quality of fuel and can reduce the performance compared to the diesel fuel (DF)[4-6].

A Review of the Concept of Fuel-Water Internally Rapid Mixing Injector in Burner System

This paper reviews the effects of premix fluids between biodiesel, air, and water for external combustion especially open burner. During burning process, biodiesel combustion involves the fuel-air mixing characteristic such as oxidation stability, stoichiometric point, bio-fuel composition, antioxidants and viscosity that influences more NOx emissions than diesel fuel. The strategies to reduce NOx emission are acquired with water additional in biodiesel fuel mixing during early stage of burning process. The method to mix biodiesel-water with injector was acquired in burner system. A vast majority of author reported that the variation in mixing of blending biodiesel ratio and water was found to enhance the burning process and mixture formation thus predominantly reducing the NOx emissions.

Extensive Studies on Internal and External Heat Transfer Characteristics of Integrated Impingement Cooling Structures for HP Turbines

This paper deals with experimental and computational studies on internal and external heat transfer characteristics of advanced impingement cooling units combined with pin-fin cooling as well as film cooling, which is called integrated impingement cooling structure. This integrated cooling structure can be employed in the not too distant future as a simple model of quasi-transpiration cooling system for ultra high TIT (Turbine Inlet Temperature) aeroengines or gas turbines. The present study is motivated by the study of Nakamata et al. (2005) who carried out a series of studies on the integrated impingement cooling system. They found that several arrangements of impingement holes and film cooling holes mutually staggered with respect to pins yielded better cooling performance than other non-staggered configurations, although there was no evidence-based explanations shown in their study on the flow physics happening in the cooling models. Therefore, two large-scaled acrylic-resin test models with different arrangements of the impingement and film cooling holes around the pins are made in the present study, emulating the specimens used by Nakamata et al., to evaluate internal and external heat transfer coefficients as well as film effectiveness of the test models. This study accordingly aims at clarification of the reason for the clear distinction in cooling efficiency observed by Nakamata et al. between those two different cooling configurations. The measurement technique employed is a transient method using thermochromic liquid crystal to determine not only heat transfer coefficient but also film effectiveness at the same time. Steady RANS simulation is also executed using ANSYS CFX-10 to acquire detailed information on the flow behaviors and heat transfer characteristics inside and outside the cooling systems. The experimental data, along with the numerical information, reveal that the observed difference in cooling efficiency is can be explained mainly by the difference in internal heat transfer coefficient over the target plate, indicating that the pin arrangement around the impingement jet is an important factor in order to attain higher cooling performance of the proposed integrated impingement cooling system.Copyright

A review on measurement techniques of apparent thermal conductivity of nanofluids

Thermal conductivity of nanofluids has been extensively studied for a number of years because it is a very first evaluation of the heat transfer performance of nanofluids. However, not the single theoretical model predicts thermal conductivity of nanofluids accurately. Hence, different measurement techniques have been used to measure thermal conductivity of nanofluids. This paper focuses on different measurement techniques of thermal conductivity of nanofluids. The working principle, limitation and advantages of different measurement techniques have been discussed. The measurement techniques discussed in this paper included transient hot wire, transient plane source, 3-omega technique, steady-state parallel method, thermal comparator and laser flash method. Eventually, some suggestions have been made for improving the reliability of the measurement of thermal conductivity.

Effect of Algae-Derived Biodiesel on Ignition Delay, Combustion Process and Emission

Algae oil methyl esters produced from algae oil were blended with diesel at various volumetric percentages to evaluate the variations in the fuel properties. Microalgae biodiesel production has received much interest in an effort for sustainable development as the microalgae seem to be an attractive way to produce the biodiesel due to their ability to accumulate lipids and their very high actual photosynthetic yields. Correlations between fuel properties, including the calorific heat, density, kinematic viscosity, and oxidation stability of the Algae oil-diesel blends, and the blending ratio of the algae biodiesel have been established. As a result, low blending ratio of the Algae oil with diesel was recommended up to 2vol % in comparison with other type of biodiesel-diesel blends. The objective of this research is to investigate effect of biodiesel blending ratio on ignition delay, combustion process and emission for different type of biodiesel. The combustion tests of the Algae-Derived biodiesel blends were performed in a Rapid Compression Machine (RCM). The combustion tests were carried out at injection pressure of 130 MPa and ambient temperature were varied between 750 K and 1100 K. The result from the experiment is compared with Palm-Oil biodiesel which are varied in biodiesel percentage from 5vol% to 15vol% and jatropha biodiesel. Higher ignition delay period were clearly observed with higher blending ratio. It seems that increasing blending ratio exhibits relatively weakens in fuel ignitibility and therefore prolongs the ignition delay of algae biodiesel. A2 had the lowest ignition delay period when compared with J2, B5, B10 and B15 due to lower density that present in A2 molecules.The concentration of carbon dioxide and nitrogen monoxide in the exhaust gas increased with higher blending ratio while the concentration of carbon monoxide and hydrocarbon decreased.

Thermal Imaging of Flame in Air-assisted Atomizer for Burner System

Infrared thermography was used as a part of non-intrusion technique on the flame temperature analysis. This paper demonstrates the technique to generate the thermal images of flame from the air-assisted atomizer. The multi-circular jet plate acts as a turbulence generator to improve the fuel and air mixing in the atomizer. Three types of multi-circular jet plate geometry were analysed at different equivalence ratio. Thermal infrared imaging using FLIR thermal camera were used to obtain the flame temperature. Multi-circular jet 1 shows the highest flame temperature obtained compared to other plates. It can be concluded that the geometry of the plate influences the combustion, hence affects the flame temperature profile from the air-assisted atomizer.

Effects of Fuel and Nozzle Characteristics on Micro Gas Turbine System: A Review

For many decades, gas turbines have been used widely in the internal combustion engine industry. Due to the deficiency of fossil fuel and the concern of global warming, the used of bio-gas have been recognized as one of most clean fuels in the application of engine to improve performance of lean combustion and minimize the production of NOX and PM. This review paper is to understand the combustion performance using dual-fuel nozzle for a micro gas turbine that was basically designed as a natural gas fuelled engine, the nozzle characteristics of the micro gas turbine has been modelled and the effect of multi-fuel used were investigated. The used of biogas (hydrogen) as substitute for liquid fuel (methane) at constant fuel injection velocity, the flame temperature is increased, but the fuel low rate reduced. Applying the blended fuel at constant fuel rate will increased the flame temperature as the hydrogen percentages increased. Micro gas turbines which shows the uniformity of the flow distribution that can be improved without the increase of the pressure drop by applying the variable nozzle diameters into the fuel supply nozzle design. It also identifies the combustion efficiency, better fuel mixing in combustion chamber using duel fuel nozzle with the largest potential for the future. This paper can also be used as a reference source that summarizes the research and development activities on micro gas turbines.