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Comparing the Effect of Palm and Jatropha Biodiesel in a Diesel Engine

3 November 2006

Researchers at Indonesia’s Institut Teknologi Bandung have compared the effects and performance of biodiesel fuels derived from two different feedstocks of importance to that country—palm oil and jatropha—in a direct-injection diesel engine.

The study, described in a paper presented at the recent FISITA 2006 conference in Yokohama, Japan, by Dr. Iman Reksowardojo, compared five fuels: B10 palm oil biodiesel, B100 palm oil biodiesel, B10 jatropha biodiesel, B100 jatropha biodiesel and petrodiesel.

The tests measured the effects on the injection pump and nozzles, piston crowns and cylinder heads. The tests also measured emissions of NOx and CO, and fuel consumption.

Fuel Properties
ParameterUnitPalm Oil BiodieselJatropha Oil BiodieselPetrodiesel
Viscosity Cst 5.3 (40°C) 3.576 (50°C) 3.15(40°C)
Density g/cm3 0.868 (25°C) 0.8809 (15°C) 0.8253 (40°C)
Flash point °C 191 174 70
Calorific value kJ/kg 36,764 39,340 45,457
Cetane number 61.5 58.4 51.5
Acid value mg KOH/g 0.24 0.38 0.06
Total glycerol % 0.08 0.17
Free glycerol % 0.001 0.01

Among the results the study found were that:

  • Fuel consumption. The differences between fuels were not significant, but B10 Jatropha Curcas turned in slightly lower results that the other blends. The researchers assumed this is because the low viscosity, oxygen content and higher cetane number of B10 Jatropha Curcas contributed to better combustion. This result is still under exploration.

  • CO emissions. CO exhaust gas emissions decreased as the content of biodiesel fuel increased in the blending fuel. B100 Palm emitted more CO than other fuels except Petrodiesel, and the researchers concluded this is a result of the highest viscosity of the fuel leading to poorer atomization.

  • NOx emissions. B100 Jatropha emitted significantly more NOx than the other fuels. This result is also still under investigation.

  • Effect on the injection plunger. The additional weight added to the plungers using the biodiesel blends was lower compared to Petrodiesel, with the exception of B100 jatropha biodiesel.

  • Effect on the injection nozzle. While the weight of all nozzles—B100 Palm, B10 Palm, B100 Jatropha Curcas, B10 Jatropha and Petrodiesel—increased, the higher the biodiesel percentage in the fuel burned, the lower the weight increase of the nozzle. This was attributed to the oxygen content in the biodiesel contributing to improved combustion, resulting in lower deposits in the nozzle. Palm Oil biodiesel nozzles had the lowest weight gain.

  • Effect on the piston. Although deposits formed in the piston crowns from all the fuels, the deposits resulting from biodiesel use were easier to clean compared to the Petrodiesel.

  • Effect on the cylinder head. The thickness of the deposits on the cylinder head followed the same trend as the piston crown deposits. Use of B100 jatropha resulted in the lowest amount of deposits.

The team concluded that the results highlighted that the quality of biodiesel and its effect on engine components is determined partly by the raw material of the feedstock.

November 3, 2006 in Biodiesel, Engines | Permalink | Comments (6) | TrackBack (0)

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Comments

In comparative studies such as this one, the injection timing and sometimes even the volume are kept constant. B100JC in particular appears to atomize almost as readily as petrodiesel and its higher cetane number causes it to ignite more readily. The result is more rapid combustion, which leads to higher temperatures and hence, higher NOx.

The more rapidly the fuel combusts, the better the approximation to the thermodynamically ideal isochoric Otto process. I suspect the Jatropha tests also generated the highest level of combustion noise. B10JC should yielded a slight (I'm guessing <2%) improvement in fuel efficiency. With B100JC, the timing of the 50% conversion point may not have been optimal or, the additional radiative heat loss (proportional to abs. temp to the fourth power) may have overcompensated for the thermodynamic gain.

The NOx increase observed in high biodiesel (or xTL, for that matter) blends can be compensated for via modifications to the intercooler, injection strategy, EGR rate and/or adding retardant additives to the fuel formulation. A much more difficult challenge is to detect fuel properties automatically and adapt accordingly, because of the significant impact even small changes can have on power, noise and emissions. A useful strategy is for governments to mandate modest biodiesel blends so engine developers have a predictable, standardized fuel composition to optimize against.

Isochoric combustion (Otto cycle) is really the most efficient way of fuel combustion in IC engine. It is employed in gasoline SI engines, where max compression ratio is limited by antidetonation properties of gasoline. In diesel engine there is no such limitation. Instead, max compression ratio of diesel engine is limited by ability of its components to withstand stress of max combustion pressure. That’s why normal isobaric combustion of injected diesel fuel is beneficial to thermal efficiency of diesel engine, allowing higher compression ratio with same max combustion pressure. Modern multi-event common rail diesel fuel injection systems are generally mimicking such isobaric combustion. Additional advantage is lower NOx generation.

It is, actually, basics.

You can get more, per acre, from oil palm than jatropha. On the flipside, palm is more capital intensive, and jatropha can assist in the restoration of depleted soils.

With turbo boost, injection timing and amount relatively easy to control, why would ya mess it up with a spark plug?

Jatropha can be grown on wastelands in India, not many palm trees grow here

I need your help. I am not an engineer and I know nothing about car engine, but I am very interested in community development--educating Cambodian rural inhabitants to use local resources, restore and improve soil through practical farming methods.

For my non-profit, I am starting a Jatropha farm and I want to encourage subsistent farmers to grow Jatropha and we will form a Co-op. So, I am looking for (or creating) a local Jatropha market.

In Cambodia, the petroluem fuel costs over $1.00 per liter (the income per capita is around $300 per year).

1. Can we use Jatropha biodiesel in cars with diesel engines?
2. Do we need to do anything to the engines or biodiesel?

Any ideas, suggestions are greatly appreciated it. Please point me to the right resources on this topic.

Thanks. Mardi

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