Several methods have been reported for enhancement of biodiesel fuel as an engine fuel. However, there are certain shortcomings like increasing fuel consumption at higher torques and loading conditions? Would this be economical also considering the adoption of the fuel? Also, would the combustion process of more fuel not result into increased heat release rate from the engine?
I suppose the problem is for modern engines.
The simplest way to start on the problem is to make the hypothesis that the engine efficiency is not modified by the use of biodiesel. My experience is this is true when the LHV (lower heating value) is not very different of diesel fuel LHV. Let us say less than 15%. This is the case with esters.
After, as the diesel engine control the injection volume, the engine adjust the injection volume to the torque required by the user ... but until the maximum possible volume ... So less maximum torque when there is less LHV....
and more consumption when there is less LHV.
There is no other solution on the fuel. There is possible solution on engines when they are not optimized for fuel efficiency. But in that case they are optimized to pass pollution rules ...
To be short :
same torque and speed = same injection of energy => more volume injection
but same heat rejected.
Having blends of around 20% along with diesel gives near brake thermal efficiency as diesel. However the optimum combination percentages of biodiesel (methyl esters) differs slight from one to other. Brake thermal efficiency depends on calorific value and consumption of fuel.
Respected,
If you are researching the improvement of biodiesel characteristics, for example by the technological process of obtaining, it is essential that the biodiesel characteristics comply with EN 14214 (for the EU or similar). But this is not enough from the aspect you mentioned (and which is typical), in my opinion .
The production of biodiesel should be directed to:
1. increase FAME content to the maximum possible.
2. Reduction of density (to 860 kg/m3) and viscosity (to 3.5 mm2/s)
3. Reduce Iodine value etc.
In addition, the sound velocity and the bulk modulus of biodiesel should be checked for the range of operating pressures and temperatures.
After all this, you can also consider a partial increase in oxygen content in biodiesel to get better combustion, etc., given the lower heating value of biodiesel.
Considering the ecological character of this fuel, on the basis of everything else, if necessary - try with additives, of course, ecologically, if possible.
Adjusting the injection system is another option if it is so important that you get improved engine performance in higher operating modes.
An ideal solution would be that the injection system may recognize the type of fuel (or mixture) and correct the set-up on the intended.
To answer this, increasing of fuel consumption at higher torque and loads are unavoidable things but the economical outcome depends upon the type of biodiesel used (their raw material cost, extraction cost, purification, transportation, storage cost etc). lesser these expenses, lesser will be the overall cost and also the increased fuel consumption will not affect the economical values. but this is highly unlikely to obtain while the biodiesel is prepared in a small amount, higher the scale higher the economical aspects will be.
More the fuel doesnt necessarily means more heat release rate. since many factors also controls the heat release rate. and on the other hand At higher loads and torques, you could also notice the increase of HC and CO emissions, which states that more amount of the fuel escapes combustion.
Thanks to you all @ Paul Gateau Boban Nikolic Mebin Samuel , Pisipaty Srinivas Kishore
Your comments are well noted. I would get back to you to inquire for more help as at when needed. I appreciate your time and I covet more of it.
Kind regards.
@oyetola as soon as you blend a fuel, a certain importance should be given to the air supply or the A/f ratio. Generally it is overlooked and is said to be a factor to be kept constant. If I am blending my fuel I do need to check the stoichiometric shift.
Except for very low loads, the thermal efficiency of a diesel engine should not change by replacing petroleum diesel with biodiesel or its blends. The engine will consume more fuel by volume and by weight, because of the lower energy content of biodiesel relative to diesel fuel, but this is not because of lower efficiency.
Most of papers cited in the literature reported that blending of diesel with bio diesel reduces the brake thermal efficiency slightly as well as increases the BSFC. The improvement comes from optimization strategies to enhance the performance of diesel engine. please refer to :
"Optimization strategies to reduce the bio diesel NOx effect in diesel engine with experimental verification"
Energy Conversion and Management 68 (2013) 96–104
Several ways you can follow to boost the efficiency of diesel engine
using diesel blended with bio diesel and recording parameters for combustion, performance, and emissions
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