Fuel Selection Guidelines per type of Diesel Engine 1

[DreamyOiler]

Hi EveryOne
I am preparing for a short-course about Diesel Fuels, attendantees are lab chemists from several oil companies here in Alexandria, Egypt. I find good enough published lecturenotes about the design of Diesel Engine in the Mechanical Engineering literature. I need a reference, textbook or published pdf file, from which I can find info that let me relate the "Fuel Type/Grade" to the "Service/Speed" of the Diesel Engine. I couldn't find clear cut info covering this issue in ASTM D 975 as for example when touching the engine's speed it specifys only variable vs constant speed, but what about low vs high speed and the fuel type preferentially or recommended per each speed? Which type/grade of ASTM D 975 Diesel Fuels to be used per each service as Automotive/Locomotive/Marine/Power Generation??? I sincerely wish to clarify this issue to the chemists who analyze the fuels without being able to relate the characteristics they find in their tested oils and the enduser Diesel Engine type. Appreciate any elaboration that can lead me to the correct vision of this ignored issue in the published literature.

 

[ivymike]

From the manufacturer's point of view, you want to design your engine to run on the widest variety of fuels that you can achieve economically while still meeting the relevant performance and emissions requirements.

Emissions requirements have driven diesel engine fuel selection for the last decade or so in more-regulated countries, with Sulfur being one of the main regulated constituents of the fuel (because of its effects on exhaust catalyst performance/durability, its contributions to corrosion within the engine if EGR is used, and its effect on SOx emissions from larger engines).

Looking at a non-egr, non-aftertreatment high speed (1800rpm) diesel engine of about 13L displacement, you could run nearly any fuel on the list if it were not for emissions requirements. The one kind of fuel you wouldn't typically run is bunker fuel / marine diesel oil / heavy fuel oil.

Looking at the same engine with a current model year in the USA, you're prevented by law from running >15ppm S, which eliminates most things on the list.

Bunker fuel / marine diesel oil / heavy fuel oil are typically run by large seagoing vessels in areas without stringent emissions (particularly SOx) restrictions. They're not commonly used in any land-based application, and they're not typically used in smaller vessels. In fact, there are examples of medium-speed (600-1000 rpm) diesels up to about 8000hp which cannot burn HFO/MDO.

 

[Lou Scannon]

Certainly the US Navy has conducted/funded extensive research into what is necessary versus what is desireable in the way of comprehensive properties of distillate fuel for all the types of reciprocating engines used in their shipboard equipment (including propulsion engines). I was involved in a very small part of this in 1990 through 1992, which was presented and published in ASME. I'm trying to search the site right now but the engine is going very slowly, i.e. no results coming up. I don't want to focus too much on the work I was involved in, which was more or less the end game of durability testing a selection of high speed engines on the designated "worst case" fuel.
Some suggested keywords & phrases for burrowing into this work:
[ul]
[li]US Navy[/li]
[li]Annapolis MD
(headquarters directing this work)[/li]
[li]NIPER
(private laboratory where I worked, that conducted some of the chemical studies in addition to durability testing)[/li]
[li]"distillate fuel"
(Navy's term for what we commonly call diesel fuel)[/li]
[li]"broadened specification"
(i.e. the objective of the research)[/li]
[li]shipboard
(i.e. broadened fuel specification was intended for shipboard equipment, not necessarily land based)[/li][/ul]

Search still churning at ASME site. If I get any successful hits I'll link them in this thread.


"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

 

[DreamyOiler]

IvyMike/Hemi: I teach several chemical engineering courses that need experience in the real world as Adjunct Professor in 3 Egyptian universities. I encourage my students to enter/subscribe into Eng Tips forum to learn. I tell my students when people are as generous with info/help as in Eng Tips this tells of selfconfidence and also of good ethical value/trait. This expanded introduction is to say thanks for your help. When I teach the Gasoline engine to chemistry/chemical engineering students; I describe the importance of 10, 50 & 95 % distillation as to reflect on the response of the fuel to the startability/acceleration/dilution of crankcase oil of the engine. When I am going to teach the Diesel engine, is there a similar significance of the distillation of a given Diesel fuel oil that reflects on the response of the fuel to the engine performance?? Is the "combustion lag" is the only accelereation limit in Diesel engines when compared to Gasoline engines (Diesel: slower vs Gasoline: faster)? All that I could see in the Specs is the 350 Celsius limit on % Distilled that it should not exceed 95% V. This limit exists to avoid including waxy distillates ( Boiling over 350 C/662 F) among the components of Diesel fuel. What determines a given Diesel engine's speed? is it, as in Gasoline engines, relevant to compression ratio? Is combustion chamber capacity relevant to the maximum power that I can get from a Diesel engine? If so; in Diesel engines; would the high compression ratio with high combustion chamber capacity be an operational problem? When I prepare for a course I try to predict what would the audience thinking of/wishing to know from the instructor. The Diesel engine courses are written for mechanical engineering students; hence I find in them info gabs because of my chemistry background. Thanks for your patience with me.

 

[ivymike]

It might help you to read this:

http://www.dieselnet.com/tech/fuel_diesel.php

Is the "combustion lag" is the only accelereation limit in Diesel engines when compared to Gasoline engines (Diesel: slower vs Gasoline: faster)?
I'm actually surprised by the question - I had never considered combustion rate as a limiting factor in engine acceleration (not sure it is in a practical sense, but perhaps others will chime in). If you mean maximum angular acceleration of the engine then there are some other things to consider:
- size of the flywheel or other inertial elements connected to the engine (will "rev up" faster with less inertia)
- response rate of the turbocharger - not sure how much impact this will have on unloaded acceleration, but it is a big player in loaded acceleration of the engine - if your turbocharger does not quickly respond to engine load changes, and assuming that your air-to-fuel ratio must be maintained within a specific range to achieve your desired emissions, the amount of fuel you can burn (and thus power, and consequently acceleration) will be adversely affected.
- drawing a blank, but I'm not spending much time thinking about this at the moment

What determines a given Diesel engine's speed?
The governor or engine control module will control the speed of the engine once the engine is built. From a design standpoint, the maximum achievable speed is dependent upon a host of mechanical factors in addition to any chemical ones. In a practical sense the application determines the speed of the engine. You can design diesels to operate at very low speeds, somewhat high speeds, and just about anything in between. I've never seen a diesel that runs at 7500 rpm, but I've seen posts on the internet to suggest they may have been demonstrated. Somewhere above 4500 rpm the fuel probably gets to be very important - below that the speed limit is whatever the design team picked, which would be based on whatever the application demanded. The efficiency of the engine tends to be higher if the engine is slower, and the power density (vs volume or mass) tends to be higher if the engine is faster.

is it, as in Gasoline engines, relevant to compression ratio?
I'm not aware of a link between compression ratio and max rpm of a gasoline engine, but maybe I'm thinking about this question incorrectly? If someone asked how fast I could run the engine in my car (absent a rev limiter) I would first think about the connecting rods and valvetrain, and then some other mechanical bits, and then about the air system, and maybe after that the ignition system, and maybe after that some other things, and eventually the fuel itself?

Is combustion chamber capacity relevant to the maximum power that I can get from a Diesel engine?
Yes, there is a relationship between displacement and power output. Displacement is not the same thing as combustion chamber volume, but I think displacement is more likely what you meant to say. You should pick up virtually any basic book about engines if you need more information on this topic. There are some college-level books about engines if you want a deeper dive:

http://www.amazon.com/Internal-Comb...qid=1384359932&sr=1-1&keywords=heywood+engine

http://www.amazon.com/Engineering-F...d=1384359953&sr=1-1&keywords=pulkrabek+engine

If so; in Diesel engines; would the high compression ratio with high combustion chamber capacity be an operational problem?
I wonder what you mean by the question ... if you really mean combustion chamber capacity (the volume between the piston and head when the piston is at its closest approach to the head) then you just need a longer stroke to get a higher compression ratio when you make the chamber bigger ... obviously there are combinations which work better than others. I can't recall ever having seen a situation where someone said "I'd really like to have a larger combustion chamber, but I can't get the compression ratio I'm after if I do that." At that point I think you're saying "I need a bigger engine." There can be lots of debate about the right compression ratio and combustion chamber geometry for a particular performance & emissions target with a given engine size. Fuel characteristics like the distillation curve undoubtedly have some impact on what is/isn't a successful chamber geometry & spray pattern & nozzle size.