Influence of physical and chemical properties of biodiesel fuels on injection, combustin and exhaust emission characteristics in a direct injection compression ignition engine

2001 ◽  
Vol 2 (4) ◽  
pp. 249-261 ◽  
Author(s):  
K Yamane ◽  
A Ueta ◽  
Y Shimamoto

This paper describes two topics. One is a study of the effects of biodiesel fuel physical properties on injection characteristics and spray behaviour. The study was done via numerical simulation of the injection system and via laser-sheet imaging of the spray. The second topic is a study of the effects of the constituents of biodiesel fuel on combustion and exhaust emission characteristics in a retrofitted compression ignition engine, as well as combustion under high injection pressure. A critical difference between the gas oil and biodiesel fuel properties is the dependence of the bulk modulus on pressure and temperature. Computation results show that at lower fuel temperatures, the injection timing of biodiesel is effectively advanced relative to that of gas oil. This is because at lower liquid temperatures the bulk modulus of biodiesel fuel is higher than that of gas oil; then the rate of liquid pressure rise goes up and the injection timing is advanced. At higher fuel temperatures, there is no difference in the injection timing and the injection pressure between biodiesel fuel and gas oil. Engine measurements showed that at low engine load, the exhaust particulate matter (PM) using biodiesel contained a higher level of soluble oragnic fraction (SOF) than that using gas oil. This result was related to the results of spray visualization. It was found that the spray penetration for biodiesel was shorter than that for gas oil. Thus the air-fuel mixing process was relatively poor for the biodiesel fuel. Substantial fuel-rich mixture was formed at the centre of the combustion chamber, and a portion of this mixture that failed to burn was emitted as SOF. It was found that both the SOF level and the ignition delay increase with a decrease in the fraction of methyl oleate ester in biodiesel fuel.

This paper represents the relative performance of a small single-cylinder diesel engine having capacity 3.5 kW. This paper covers experimental investigations of most influencing combustion parameters such as compression ratio, injection pressure and start of injection timing and their values on performance, emission and combustion characteristic of the small single-cylinder CRDI diesel engine for which the mechanical fuel injection system retrofitted with a simple version of the CRDI system. CRDI has yielded good results for large diesel and petrol engines but still not incorporate for cheaper small single-cylinder engines, typically used in the agricultural sector and decentralized power sector for a country like India. It is observed that starts of injection timing and injection pressure are the key parameters for improving the combustion characteristics and therefore engine performance while compression ratio mainly affects the emission characteristics of the engine. Retrofitted CRDI system yielded improved exhaust emission and performance of the engine.


Author(s):  
Khanh Cung ◽  
Toby Rockstroh ◽  
Stephen Ciatti ◽  
William Cannella ◽  
S. Scott Goldsborough

Unlike homogeneous charge compression ignition (HCCI) that has the complexity in controlling the start of combustion event, partially premixed combustion (PPC) provides the flexibility of defining the ignition timing and combustion phasing with respect to the time of injection. In PPC, the stratification of the charge can be influenced by a variety of methods such as number of injections (single or multiple injections), injection pressure, injection timing (early to near TDC injection), intake boost pressure, or combination of several factors. The current study investigates the effect of these factors when testing two gasoline-like fuels of different reactivity (defined by Research Octane Number or RON) in a 1.9-L inline 4-cylinder diesel engine. From the collection of engine data, a full factorial analysis was created in order to identify the factors that most influence the outcomes such as the location of ignition, combustion phasing, combustion stability, and emissions. Furthermore, the interaction effect of combinations of two factors or more was discussed with the implication of fuel reactivity under current operating conditions. The analysis was done at both low (1000 RPM) and high speed (2000 RPM). It was found that the boost pressure and air/fuel ratio have strong impact on ignition and combustion phasing. Finally, injection-timing sweeps were conducted whereby the ignition (CA10) of the two fuels with significantly different reactivity were matched by controlling the boost pressure while maintaining a constant lambda (air/fuel equivalence ratio).


The purpose of this study is to investigate the effect of fuelinjection pressure onhomogeneous charge formation and performanceand emission characteristics of Homogeneous charge compression ignition engine. The fuel injection pressure isone of the primary parameter for improvingthe homogeneity of the mixture and governing the power output and emission characteristics of HCCI engine. In this investigation, diesel fuelwasinjected at different injection pressuresas 2bar, 3bar, 4bar and 5bar respectively throughbyport fuel injector. The experimental investigationsshow that increasing the fuel injection pressure will promote the fuel to penetrate with air and creates well pre mixedair/fuel charge.The result shows, the specific fuel consumption (SFC) of HCCI engine isslightlyhigherthan the SFC of conventional diesel engine.The HCCI engine with 3bar injection pressure operated engine has lower SFC values compared to other injection pressure operated HCCI engine.The brake thermal efficiency of HCCI engine, operated with 3barinjection pressure has maximum BTE values over the other injection pressure operated engine.From theresult, it is observed that HCCI engine has lower smoke density values compared to conventional diesel engine andfurther reducedby increasing the fuel injection pressure. The 3bar injection pressure operated HCCI engine has emitted lower smoke densitycompared to other injection pressure operated HCCI engine. The 3bar injection pressureoperated HCCIengine hasemittedmaximum oxides of nitrogen (NOx) emissions than the other injection pressure operated HCCI engine. Other exhaust emissions of carbon monoxide (CO) and hydrocarbon (HC)emissions are increased when compared toconvention diesel engine


Author(s):  
Dae Sik Kim ◽  
Ki Hyung Lee ◽  
Chang Sik Lee

The objective of this work is to investigate the effect of premixed fuel ratio on the combustion and emission characteristics in diesel engine by the experimental and numerical method. In order to investigate the effect of various factors such as the mixing ratio, EGR rate, and engine load on the exhaust emissions from the premixed charge compression ignition diesel engine, the injection amount of premixed fuel is controlled by electronic port injection system. The range of mixing ratio between dual fuels used in this study is between 0 and 0.85, and the exhaust gas is recirclulated until 30 percent of EGR rate.


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