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This paper presents a schlieren optical visualization technique and its application in observation of the changes of intensity in real images. Schlieren optical visualization technique system is the unique technique because it produces a neutral image easily-interpretable image of refractive-index-gradient fields. The schlieren technique remains to be one of the most powerful techniques to visualize the flow and useful as a tool in order to observe the flow characteristics, fuel-air mixing, spray evaporation and flame development. The schlieren system provides a method to viewing the flow through the transparent media. This paper present the basics technique of schlieren system especially for Z-type and two mirror schlieren system. This optical visualization photography together with digital video camera will capture the detail spray evaporation, mixture formation and flame process.

The use of energy and natural resources being increase due to the growth of economy and world population. One of the natural resources is being consumed heavily is diesel for transportation and burner combustion. However, the major product results from the combustions of diesel are NOx and PM emissions. This review paper focuses on the influences of the emulsified renewable biodiesel fuel such as crude palm oil and waste cooking oil with the concept fuel-air-water internally rapid mixing injector for the open burner system. Water is introduced directly into the combustion field. The concept of rapid mixing from biodiesel and water are controlling of the combustion process in order to minimize the emissions. The water content in the emulsified biodiesel fuels effectively in the reduction of NOx emissions especially the high blending biodiesel. Moreover, emulsion technology significantly reduced particulate matter (PM) emissions as compared to the standard biodiesel fuel combustion. The parameters include equivalent ratio, water content in biodiesel-water, and spray characteristics such as spray penetration, spray angle and spray area.

Concern shortage and limited of petroleum, bio-fuels or also known as alternative fuel offer an advantage in order to sustain in long terms and economical. This renewable source is a good offer as an improvement attempt of automobile fuel and burner combustion. The main issue in using biodegradable alternative fuel such as 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, this study investigated the effects of different kind of biodegradable alternative fuel tested at variant in storage ambient condition under different storage duration. These tests were performed on the biodegradable alternative fuel such crude palm oil (CPO), and waste cooking oil (WCO) with different of ambient temperature and variant of blending ratio. The biodegradable fuel samples were stored in clinical compartment, at different temperatures and were monitored at regular interval over a period of 60 days. Blending of biodiesel was varied from 5vol% ~ 15vol% and storage temperature from 5°C~33°C. The effects of ambient temperature and storage duration on properties of biodegradable fuel such as density, kinematics viscosity, acid value, water content and flash point of biodiesel were discussed in detail. Analysis of this study showed that the different storage duration gave a significant effect toward the changes of water content; acid value and viscosity. As a conclusion, a long period of storage would decrease the quality of biodiesel no matter what kind of condition and environment is exposed to.

Schlieren optical visualization technique system is the unique technique due to the ability in producing a neutral image easily-interpretable image of refractive-index-gradient areas. The Schlieren system provides a method for viewing the flow through the transparent media and the most using this technique is to photograph the flow. This paper presents the review of the application of the Schlieren optical visualization system external and internal combustion engine in order to observe the fuel-air mixing and flame development during the burning process. The basic technique of Schlieren system, especially for Z-type and two mirror Schlieren system provide a powerful and clearly image to visualize the changes of the density in a transparent medium. This method can capture spray evaporation, spray interference and mixture formation clearly with real images. Analysis of optical image visualization observations reveals that the mixture formation of fuel and air exhibits the influence of the ignition and flame development. Thus, the observation of systematic control of the creation of a mixture of experimental apparatus allows us to achieve significant progress in the combustion process and will present the information to understanding the basic terms of reduced fuel consumption and exhaust emissions.

The prospects of fossil oil resources and strengthen of future emission regulation have raised keen attention together with the issue of renewable alternative fuel. As one of the different solutions to these problems, emulsion fuel technology in biodiesel has received close attention because it may provide better combustion efficiency and would contribute to a reduction in emissions, such as nitrogen oxides (NOx) or particulate matter (PM).The solution of this issue is by using Biodiesel fuel as an alternative fuel from waste cooking oil (WCO), crude palm oil (CPO) and Jatropha Oil (JPO). In addition, Waste cooking oil is one of the most economical options for producing biodiesel due to the biodegradable properties and preserves energy. This study focuses on the observation of ignition and combustion characteristics of biodiesel-water-air rapid mixing of biodegradable fuel using internally rapid mixing injector in burner combustion. In this research, the relation of mixture formation, burning process and flame development of biodiesel were investigated in detail. The parameters include equivalent ratio, water content and mixture formation are studied. The flame development is analysed in term of flame longest for testing. The result shows that equivalent ratio and water content affect the combustion. Increasingly of water content will reduce the flame length and increase the probability of misfire.

The Schlieren technique remains to be one of the most powerful technique to visualize the flow and it is relatively easy to implement, high and variable sensitivity, low cost and its used conventional of light. This technique allows us to see the invisible of the optical inhomogeneities in transparent media like air, water and glass that otherwise cause only ghostly distortions of our normal vision. This research investigates the mixture formation and flame development of biodiesel fuel using the Schlieren optical visualization principle. This method can capture spray evaporation, spray interference, mixture formation and flame pattern clearly with real images. During the experiment, the camera lens was used with telephoto lenses (Nikon 70-300mm f/4-5.6G) in order to capture a large amount of light especially the low flame intensity during the initial flame development. The flame development was captured with color images from a color digital video camera. This method can capture the flow of fluids of varying density, such as spray evaporation, spray interference and mixture formation clearly with real images. The result shows that the mechanism of fuel-air mixing and a better comprehension of combustible mixture that can give valuable information to improve and optimize the combustion process.

There are many technologies about exhaust emissions reduction for wide variety of spark ignition (SI) engine have been considered as the improvement throughout the combustion process. The stricter on legislation of emission and demands of lower fuel consumption needs to be priority in order to satisfy the demand of emission quality. Besides, alternative fuel such as methanol-gasoline blends is used as working fluid in this study due to its higher octane number and self-sustain concept which capable to contribute positive effect to the combustion process. The purpose of this study is to investigate the effects of methanol-gasoline fuel with different blending ratio and variant ambient pressures on flame development and emission for gasoline engine. An experimental study is carried towards to the flame development of methanol-gasoline fuel in a constant volume chamber. Schlieren optical visualization technique is a visual process that used when high sensitivity is required to photograph the flow of fluids of varying density used for captured the combustion images in the constant volume chamber and analysed through image processing technique. Apart from that, the result showed combustion burn rate increased when the percentage of methanol content in gasoline increased. Thus, high percentage of methanol-gasoline blends gave greater flame development area. Moreover, the emissions of CO, NOX and HC are performed a reduction when the percentage of methanol content in gasoline is increased. Contrarily, the emission of Carbon dioxide, CO2 is increased due to the combustion process is enhanced.

The stricter on emission legislation and growing demands for lower fuel consumption require significant efforts to improve combustion efficiency while satisfying the demand of emission quality. Gasoline blend with ethanol provided advantages due to its self-sustaining concept and high octane number which can be influenced to the combustion process. The purpose of this study is to investigate the effect on the emission and flame propagation of gasoline under the different blending ratio of ethanol fuel in a constant volume chamber. In this paper, the flame propagation of ethanol blends with gasoline in a constant volume chamber has been carried out. The real image is observed by schlieren optical visualization technique and image processing technique. The parameters in this study also included different types of injection pressure, characteristics of flame propagation and different blending ratio of ethanol in gasoline fuels. As a result, the burn rate increases when the content of ethanol percentage in gasoline increased. Therefore, the higher flame propagation area for 0.2 MPa, 0.3 MPa, 0.4 MPa were headed by E15 followed by E10, E5 and gasoline fuels respectively. It is subjected that the increasing of ethanol percentage blends with gasoline could lead to the reduction of CO, HC and NOX emissions. However, the CO2 emission is higher due to the combustion process was enhanced.