Blends 65 Table 4.22. Select Fuel Properties and Emission Results of Test Blends 69 Table B.l. There has been no reported effect of storage container on biodiesel ageing, unless if the container is metallic in nature or of a translucent material that can absorb light (Mittelbach and Gangl 2001; Thompson et al. Accelerated ageing studies have examined the impact of oxygen flow rate, temperature, antioxidants, feedstock type and metals on fuel oxidation (Canakci et al. Accelerated test methods are conducted under extreme conditions involving high oxygen concentrations, high temperatures and high pressures; where the idea is to advance the chemical reactions that would occur otherwise under "non-accelerated" or "real-23 time" conditions. The results of accelerated ageing can be compared to what may happen in practice, but cannot be relied upon to simulate natural ageing. As there are cases where reactions that occur during accelerated ageing may not transpire during real time ageing (Services 1997). Bondioli et al. 1 year under real time conditions and biodiesel stored for 24 weeks at 43掳C with biodiesel aged at 80 掳C for 24 hours and concluded differences in the rates and types of degradation reactions taking place at each case.
The ageing behaviour of biodiesel is different under different conditions and there is a limit in applying accelerated ageing methods to estimate biodiesel stability and properties under real time conditions (Bondioli et al. Accelerated samples will have markedly different fuel properties when compared to samples undergoing ageing for long periods in ambient conditions. 1 OP-XT 100 T P D100 (3) The mixing of 20% vol. B20 fuel with a fuel property value that is correlated to the above formula. The result can only be confirmed with experimental testing and would depend on how well the two fuels mix and blend to reflect their independent characteristics in the blend. Depending on the accuracy of 24 results of fuels used in blends, users and producers could better evaluate certain fuel properties of the mixed blends by using the above formula and can avoid conducting tests on the blend itself. For example, they can calculate predicted fuel properties of blends based on the fuel property information of the B100 and D100 blends.
This may be useful since there is no standard in place yet for B20 or any other biodiesel blend and there have been limited comparative investigations or research into fuel property sets of biodiesel blends. The diesel engines of today with their high temperature and pressure operating conditions require fuels of good stability (Miyata et al. Using poor quality fuel in a diesel engine may lead to plugging of fuel filters, poor atomization characteristics, formation of deposits and injector coking. 10 -72 (Haas etal. 9 -68 (Sheehan et al. 23 -35 -10 -26 (Purcell et al. 11 -66 (Graboski etal. 2 -14 (Sheehan et al. 5 -11 (Schumacher et al. 1 -14 (Graboski et al. 3 -15 (Chang etal. The results are summarized in Table 2.13 where the change in emissions between the YGME and SME are statistically insignificant. 11.6 -64.2 Table 2.14. Regulated Exhaust Emissions of No. 1 Diesel, 20 % SME and SME (Canakci 2005) CO (%) HC (%) NOx (%) No. 2 Diesel - - -No. 11.2 27 The magnitude of the emission variations between different studies is not only dependent on the test engine and test conditions, but also on fuel properties.
Fuel properties affecting the combustion process can influence emission characteristics. The properties of viscosity, cetane number, heat of combustion and specific gravity are known to impact combustion (Canakci et al. The requirement to conduct more research on how the properties of biodiesel effect engine emissions has been stressed. From the summarized data, biodiesel relative to petrodiesel reduces the amount of CO, HC and PM and causes increases in NOx. Some reasons for these observations is that, compared to petrodiesel, biodiesel contains no aromatic compounds, is 10-12 % oxygen by weight, and has a higher cetane number (Canakci et al. 2006; Jeong et al. The main factors affecting NOx emissions is the fuel oxygen content, combustion temperature and combustion time (Jeong et al. NOx increases as temperature increases in the combustion chamber. NOx is problematic due to its potential to react in the atmosphere and produce ozone, which is a component of smog. 28 3.0 MATERIALS AND METHODS 3.1 Test Fuels The test fuels used in this study are commercially available biodiesel and petrodiesel fuels.
