Amir Khalid

Effect of Air Entrainment and Oxygen Concentration on Endothermic and Heat Recovery Process of Diesel Ignition

The mixture formation prior to the ignition process is a key element in the diesel combustion because it significantly influences throughout the combustion process and exhaust emissions. Purpose of this study is to clarify the effects of ambient temperature, oxygen concentration and air entrainment into the spray on the heat release process during ignition delay periods. This study investigated diesel combustion fundamentally using a rapid compression machine and high speed digital video camera. The detail behavior of spray evaporation, spray interference and mixture formation during ignition delay period was investigated using the schlieren photography system. Ignition process, flame development and images of the spray ignition with extremely dark flame were investigated by light sensitivity direct photography method. Heat release processes were analyzed by pressure measurement in the chamber. Results show that short endothermic process produces slow heat recovery, leading to gentle increase of initial heat release rate. Low oxygen concentration produces slow heat recovery process rather than long endothermic period, which suggests fuel-air mixing is required to promote chemical reaction for the case of low oxygen-concentration atmosphere. Initial heat release is activated to some extent by increase of air entrainment into spray during ignition delay period. However, excessive air entrainment increases initial heat release little and rather affects diffusion combustion.

From clay to graphene for polymer nanocomposites—a survey

The development of aerospace and automotive industries requests lightweight, high-performance materials, and polymer nanocomposites are ideal candidates in this case, which is shown by the increasingly more publications in this research field over the past two decades. However, the performance of nanocomposite not only depend on the properties of their individual constituents, but on their morphology and surface characteristics of fillers as well. Selections of nanofillers geometries, e.g. particulate, fibrous or layered have a tremendous influence on the properties of nanocomposites and their processing methods. In this paper, we review the chronological works performed in the field of polymer nanocomposites, in particular epoxy nanocomposites reinforced with layered fillers, such as clay and graphene. Surprisingly layered fillers are commercially available and more cost-effective than nanoparticles and carbon nanofibres, and these make them to the most extensively studied fillers that can be geared toward future applications, particularly in large-scale polymer nanocomposite production.

Performance and Emissions Characteristics of Diesel Engine Fuelled by Biodiesel Derived from Palm Oil

Bio fuels based on vegetable oils offer the advantage being a sustainable, annually renewable source of automobile fuel. Despite years of improvement attempts, the key issue in using vegetable oil-based fuels is oxidation stability, stoichiometric point, bio-fuel composition, antioxidants on the degradation and much oxygen with comparing to diesel gas oil. Thus, the improvement of emissions exhausted from diesel engines fueled by biodiesel derived from palm oil is urgently required to meet the future stringent emission regulations. Purpose of this study is to explore how significant the effects of palm oil blending ratio on combustion process that strongly affects the vehicles performance and exhaust emissions. The engine speed was varied from 15003000 rpm, load test condition varied by Dynapack chassis dynamometer from 050% and palm oil blending ratio from 515vol% (B5B15). Increased blends of biodiesel ratio is found to enhance the combustion process, resulting in decreased the HC emissions with nearly equal of engine performance. The improvement of combustion process is expected to be strongly influenced by oxygenated fuel in biodiesel content.

Effects of Storage Duration on Biodiesel Properties Derived from Waste Cooking Oil

The reduction of world oil reserves fossil fuels and increasing environmental concerns significantly influences the popularity of biodiesel as an alternative diesel. This research investigates the effects of storage duration of variant blending waste cooking oil ratio under different storage temperature on fuel properties. The biodiesel samples were stored at different temperatures and were monitored at regular interval over a period of 70 days. Blending of biodiesel was varied from 5vol % (WCO5) ~15vol% (WCO15) and storage temperature from 24°C~35°C. These samples were monitored on a weekly and the effects of storage conditions on properties of biodiesel such as density, kinematics viscosity, acid value, water content and flash point of biodiesel were discussed in detail. The observation of biodiesel shows that the increasing of storage duration of biodiesel derived from waste cocking oil influences to the increasing of density, kinematics viscosity, acid value and water content.

Analysis of Mixture Formation and Flame Development of Diesel Combustion Using a Rapid Compression Machine and Optical Visualization Technique

Mixture formation plays as a key element on burning process that strongly affects the exhaust emissions such as nitrogen oxide (NOx) and Particulate Matter (PM). The reductions of emissions can be achieved with improvement throughout the mixing of fuel and air behavior. Measurements were made in an optically-accessible rapid compression machine (RCM) with intended to simulate the actual diesel combustion related phenomena. The diesel combustion was simulated with the RCM which is equipped with the Denso single-shot common-rail fuel injection system, capable of a maximum injection pressure up to 160MPa. Diesel engine compression process could be reproduced within the wide range of ambient temperature, ambient density, swirl velocity, equivalence ratio and fuel injection pressure. The mixture formation and combustion images were captured by the high speed camera. Analysis of combustion characteristics and observations of optical visualization of images reveal that the mixture formation exhibit influences to the ignition process and flame development. Therefore, the examination of the first stage of mixture formation is very important consideration due to the fuel-air premixing process linked with the combustion characteristics. Furthermore, the observation of a systematic control of mixture formation with experimental apparatus enables us to achieve considerable improvements of combustion process and would present the information for fundamental understanding in terms of reduced fuel consumption and exhaust emissions.

Effect of High Swirl Velocity on Mixture Formation and Combustion Process of Diesel Spray

Diesel engines generate undesirable exhaust emissions during combustion process and identified as major source pollution in the worldwide ecosystem. To reduce emissions, the improvements throughout the premixing of fuel and air have been considered especially at early stage of ignition process. Purpose of this study is to clarify the effects of swirl velocity on flow fuel-air premixing mechanism and burning process in diesel combustion that strongly affects the exhaust emissions. The effects of physical factors on mixture formation and combustion process to improve exhaust emissions are discussed in detail. This study investigated diesel combustion fundamentally using a rapid compression machine (RCM) together with the schlieren photography and direct photography methods. RCM was used to simulate actual phenomenon inside the combustion chamber with changing design parameter such as swirl velocity, injection strategies and variable nozzle concept. The detail behavior of mixture formation during ignition delay period was investigated using the schlieren photography system with a high speed digital video camera. This method can capture spray evaporation, spray interference and mixture formation clearly with real images. Ignition process and flame development were investigated by direct photography method using a light sensitive high-speed color digital video camera. Moreover, the mechanism and behavior of mixture formation were analyzed by newly developed image analysis technique. Under high swirl condition, the ignition delay is extended, the higher heat losses and unutilized high-density oxygen associated with slower initial heat recovery begins might be the explanation for the longer combustion duration, reductions of pick heat release and promote combustion and soot oxidation. The real images of mixture formation and flame development reveal that the spray tip penetration is bended by the high swirl motion, fuel is mainly distributed at the center of combustion chamber, resulting that flame is only formed at the center region of the combustion chamber. It is necessary for high swirl condition to improve fuel-air premixing.

The effects of bolted joints on dynamic response of structures

Joint is an universal fastening technology for structural members; in particular bolted joints are extensively used in mechanical structures due to their simple maintenance and low cost. However, the components of bolted joints are imperative because failure could be catastrophic and endanger lives. Hence, in this study, the effects of bolted joints on vibrating structures are investigated by determining the structural dynamic properties, such as mode shapes, damping ratios and natural frequencies, and these are compared with the monolithic structures (welding). Two approaches of experimental rigs are developed: a beam and a frame where both are subjected to dynamic loading. The analysis reveals the importance of bolted joints in increasing the damping properties and minimizing the vibration magnitude of structures, this indicates the significant influence of bolted joints on the dynamic behaviour of assembled structures. The outcome of this study provides a good model for predicting the experimental variable response in different types of structural joints.

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.

Vibration Characteristics of Composite Plate Embedded with Shape Memory Alloy at Elevated Temperature

Unique functional material of shape memory alloy has attracted tremendous interest from researches, thus has been broadly investigated for a wide range application. Current research effort extends the use of SMA for the design of smart composite structures due to its shape memory effect, pseudo-elasticity and high damping capability. This paper presents an assessment of applications of the SMA materials for structural vibration controls, where the influences of SMA as reinforcement in the composite plate at different temperature are investigated. Four cases of composite plate are studied, which two of them are SMA-based composite fabricated at 0° and 45° angles, and the other two plates are neat (without SMA wires) and built with local stiffener. By using modal testing, the free vibration analysis is carried out to determine the vibration characteristics of composite plates. The results show that infusing SMA wires into composites increased the natural frequencies of the plate considerably, while decreased slightly for damping percentage. However, when SMA wires are heated, the damping percentage improved tremendously due to the phase transformation temperature of SMA from martensite to austenite. The outcome of this study reveals the potential of SMA materials in active vibration control.

Study of Passive Vibration Absorbers Attached on Beam Structure

Structural vibration is undesirable, wasting energy and possibly leading to excessive deflections and structure and machine’s failure. In order to reduce structural vibration, one of the common way is considering vibration absorber system attach to the structure. In this study, a vibration absorber is developed in a small scale size. The host structure selected for the study is a fixed-fixed ends beam. The effectiveness of vibration absorbers attached to a beam is investigated through experimental study. In prior to experiment, a finite element analysis of Solidworks® and analytical equations of Matlab® are produced in order to determine the structural dynamic response of the beam, such as the natural frequency and mode shapes. The preliminary results of finite element analysis demonstrate that the first five natural frequency of fixed-fixed end beam are 17Hz, 46Hz, 90Hz, 149Hz and 224Hz, and these results are in agreement with the beam’s analytical equations. However, there are slight discrepancies in experiment result due to noise and error occurred during the setup. In the later stage, the experimental works of beam are performed with attached vibration absorber. Result shows that the attachment of vibration absorber produces better outcome, which is about 45% vibration reduction. It is expected that by adding more vibration absorber to the structure, the vibration attenuation can significant.