Naked Science Forum

Non Life Sciences => Technology => Topic started by: Petrochemicals on 10/01/2019 12:47:17

Title: Could diesel be made clean?
Post by: Petrochemicals on 10/01/2019 12:47:17
Not counting efficiency, could the diesil engine be made clean ? Deisel engines where initially used for there high torque output espexially at the low end of engine rpm compared to petrol engines, lorries buses tractors etc used them as they provide lots of slow constant power. It is only in recent years diesils heve become popular because the fuel takes less energy to create ie refine and is more efficient and given that turbo diesils have developed, they also now give higher acceleration, somewhere near that of petrol engines. We have all been told by different mechanisms to buy deisels and then not to, yet it doesnt seem that we will be getting rid of large diesil vehicles any time soon, as even though a bus could run off petrol, it is likely that the efficiency versus the present diesil engine would be far far below the efficiency of having a bus with a diesil engine and that means citys and motorway avenues full of dioxins from diesil.

Unfortunatley as anyone with a brian and a bit of experience could have told the governments of earth before they started pushing diesils,  what comes out of a diesil exaust is very very toxic. Is there any reasonable way to process the exaust gasses such as reburning the exaust ( efficiency not withstanding) whilst the vehicle remains largely as mobile and as maintainance free as prior to modification.
Title: Re: Could diesel be made clean?
Post by: Bored chemist on 10/01/2019 12:51:34
Is there any reasonable way to process the exaust gasses
Yes.
https://en.wikipedia.org/wiki/Diesel_particulate_filter

On an unrelated note, do you know that some web browsers contain a spelling checker?
Title: Re: Could diesel be made clean?
Post by: alancalverd on 10/01/2019 14:21:19
Diesel exhaust can in principle be much cleaner than petrol exhaust as the initial combustion phase is more complete and the exhaust temperature is fairly constant so you can clean it up with catalysts. The problem is that the peak efficiency is limited to a fairly narrow speed range, which is why trucks have as many as 24 gears - the engine speed may be limited to 950 rpm idle and 1200 rpm maximum.

This isn't a problem on ships, where you can run a huge stratified-charge engine for several weeks at 120 rpm, and may be an advantage in future aircraft running a small turbine at 10,000 rpm and delivering thrust via contrarotating electric propellors. My hope is that someone (I'm too old to start the project now) will produce a diesel-electric drive train for cars with a 100 HP diesel running at 2500 rpm charging a battery for overtaking (150 - 200 HP delivered to short-term overdriven electric motors) and town driving (diesel off, 25 HP from the battery) with 80 HP cruise power available, so the diesel is either at optimum power setting or off.

The best thing to to with government advice, whether on wind power, salt, fat, or diesel emission,  is to ignore it.
Title: Re: Could diesil be made clean ?
Post by: Petrochemicals on 10/01/2019 19:56:30
Is there any reasonable way to process the exaust gasses
Yes.
https://en.wikipedia.org/wiki/Diesel_particulate_filter

On an unrelated note, do you know that some web browsers contain a spelling checker?
Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Diesel Deisel

The filter does not remove all particles, leaving the smallest most dangerous there, being the smallest there will be more particles per quantity too. And filters soon become blocked. With it being a fuel oil too, there are more pollutants in the mix than petrol.
Title: Re: Could diesel be made clean?
Post by: alancalverd on 12/01/2019 10:21:14
At least one manufacturer (Saab) has demonstrated that the exhaust from an optimised diesel engine was cleaner than the city air it was breathing in.

All flters can get blocked but a modern DPF has an automatic  cleaning cycle that oxidises the deposits or flags up its condition if it can't be cleaned. This resolves the particulates problem for cars and trucks, which occasionally travel long distances at high speeds (when the DPF can get hot enough to clean itself) but probably not for city buses and taxis. Sadly, our lords and masters seem keen to prevent cars and trucks from entering their domains, and to promote the public transport that causes the problem.
Title: Re: Could diesel be made clean?
Post by: chris on 12/01/2019 11:21:07
Diesel exhaust can in principle be much cleaner than petrol exhaust as the initial combustion phase is more complete and the exhaust temperature is fairly constant so you can clean it up with catalysts. The problem is that the peak efficiency is limited to a fairly narrow speed range, which is why trucks have as many as 24 gears - the engine speed may be limited to 950 rpm idle and 1200 rpm maximum.

This isn't a problem on ships, where you can run a huge stratified-charge engine for several weeks at 120 rpm, and may be an advantage in future aircraft running a small turbine at 10,000 rpm and delivering thrust via contrarotating electric propellors. My hope is that someone (I'm too old to start the project now) will produce a diesel-electric drive train for cars with a 100 HP diesel running at 2500 rpm charging a battery for overtaking (150 - 200 HP delivered to short-term overdriven electric motors) and town driving (diesel off, 25 HP from the battery) with 80 HP cruise power available, so the diesel is either at optimum power setting or off.

The best thing to to with government advice, whether on wind power, salt, fat, or diesel emission,  is to ignore it.

Very interesting post @alancalverd

You refer to drive trains for cars based on a diesel electric hybrid principle. You might recall we covered a similar technology for London's ageing bus fleet:
https://www.thenakedscientists.com/articles/interviews/hybrid-buses-are-coming-london
Title: Re: Could diesel be made clean?
Post by: Petrochemicals on 14/01/2019 21:48:15
AlanCalvert heve you a link on this please, as i cannot seem to find one.

The city bus link only states the better mpg because of no idling, so does this mean significant losses in the conversion to electric.
Title: Re: Could diesel be made clean?
Post by: alancalverd on 14/01/2019 23:13:04
Nothing more detailed from me, I'm afraid, but I think the transcript was a bit inexplicit. The trick he explained was that the diesel engine is either running at peak efficiency or switched off, but without actual figures it's difficult to see if the system could be extended as I suggested to deliver short-term overpowering of the electric motor. This probably isn't necessary for a city bus, which has a limited speed range and doesn't need to overtake anything faster than a bicycle.

Title: Re: Could diesel be made clean?
Post by: Galaser on 24/01/2019 01:17:39
Looking forward to one.
Title: Re: Could diesel be made clean?
Post by: nekS576 on 25/01/2019 14:58:03
I'm waiting for it
Title: Re: Could diesel be made clean?
Post by: Petrochemicals on 07/05/2019 10:30:00
https://patents.justia.com/patent/3952507

Could something like this be used to burn all the unburned fuel, or would the particulates be too small or inconbustable.
Title: Re: Could diesel be made clean?
Post by: alancalverd on 08/05/2019 08:41:04
A bit more complicated than just using a catalyst and recovering the heat energy with thermocouples, and returning zsecondary combustion products to the carburetor will surely reduce the efficiency of the primary engine?   
Title: Re: Could diesel be made clean?
Post by: Petrochemicals on 09/05/2019 11:47:04
A bit more complicated than just using a catalyst and recovering the heat energy with thermocouples, and returning zsecondary combustion products to the carburetor will surely reduce the efficiency of the primary engine?   
Well the lowering of efficiency is acceptable to a point. The diesil engine is superbly efficient as compared to the petrol engine in high torque situations, seriously something like twice or more than petrol,  so even if they lowered the efficiency by 25 percent to have clean air you would be quids in.

I do not think it is a recirculation system, where only a portion of exaust is returned, its more like a secondary engine chamber, more air and therefore oxygen is taken in to the exaust system and an attempt at ignition takes place, i should think that most of the particulates are partially combusted material, so new oxygen would be needed. I was thinking that the mixture may be too dilute for ignition by that stage, or the particulates incombustable. If the problem is the fact that the diesel in the cylinders is expected to perform a function ?Even if you added a bit of super heated extra diesil to getting the ignition going this would be easily efficient enough for the bus and lorry application.
Title: Re: Could diesel be made clean?
Post by: teragram on 21/05/2019 23:32:14
A bit more complicated than just using a catalyst and recovering the heat energy with thermocouples, and returning zsecondary combustion products to the carburetor will surely reduce the efficiency of the primary engine?   

Carburetor??
Title: Re: Could diesel be made clean?
Post by: alancalverd on 22/05/2019 18:21:24
If you have combustible particles in the exhaust you should have run the engine slower, with more oxygen!
Title: Re: Could diesel be made clean?
Post by: teragram on 05/06/2019 23:58:17
My hope is that someone (I'm too old to start the project now) will produce a diesel-electric drive train for cars with a 100 HP diesel running at 2500 rpm charging a battery for overtaking (150 - 200 HP delivered to short-term overdriven electric motors) and town driving (diesel off, 25 HP from the battery) with 80 HP cruise power available, so the diesel is either at optimum power setting or off.

Why a "short term overdriven electric motor"? The average electric vehicle has an electric motor which very capably copes with all running conditions, cruising, acceleration, town traffic...The best situation is an electric car with an engine used only for charging the battery. The engine can then be run at a constant speed corresponding to it's maximum efficiency, something in fact like the BMW i3 with "range extender", although this is a petrol engine. Electric motors are far better at moving vehicles than piston engines.
Incidentally (my apologies for being picky) diesel engines do not have a carburettor.
On second thoughts, the "best solution" is not to have a heat engine at all.
Title: Re: Could diesel be made clean?
Post by: Bored chemist on 06/06/2019 07:44:34
Obviously, all this depends on the definition of "clean".
Teh production of CO2 is still a problem.
Title: Re: Could diesel be made clean?
Post by: Petrochemicals on 27/06/2019 03:37:57
Obviously, all this depends on the definition of "clean".
Teh production of CO2 is still a problem.
Weve been through this before, co2 is not the problem its water vapour heating the earth !
Title: Re: Could diesel be made clean?
Post by: alancalverd on 27/06/2019 23:17:37
CO2 is not a problem. It is the basis of plant growth, on which all animal life depends. The climatic fragility of human civilisation is a problem, which is in our power to solve. But we won't.
Title: Re: Could diesel be made clean?
Post by: alancalverd on 27/06/2019 23:29:43
Why a "short term overdriven electric motor"?
The maximum power obtainable from modern electric motors is limited by their temperature rise. You can water-cool a motor to optimise its continuous-power to weight ratio, and allow short-term overdrive of around 20% of max continuous for takeoff. This is common with aircraft engines which have cruise (optimum fuel consumption), METO ("maximum except takeoff") used for continuous climb, and MAX2MIN settings for getting off a short runway. Might just be useful for road transport, particularly for heavy goods vehicles.

The "range extender" logic baffles me. If your car needs say 50 horsepower to maintain 60 mph, then you need a 50 HP electric motor AND a 50 HP petrol engine for when the battery runs out. Either that, or you have to run say a 10 HP engine continuously to trickle charge the battery, and in either case carry enough liqjuid fuel to run the car for x miles at 60 mph where x is the range extension. 
Title: Re: Could diesel be made clean?
Post by: KevinSalyer on 01/07/2019 09:46:29
Firstly, sediment diesel oil. Usually after sediment 96 hours, 0.005 mm of particles can be removed. The longer the sediment  time is, the more obvious the removal effect of minor impurities which can not be removed by the filter is.

Then, when use diesel oil which has sediment, do not shake it. A sucker or hose for pumping can not be inserted directly into the bottom of the barrel, leave at least 80-00mm away from the bottom of the barrel, refueling cannot be done by pouring oil in an inclined drum. As for diesel oil below 80-100mm in oil drums, they can be centralized and reused after precipitation and filtration.

When refueling, it must be filtered, this is to prevent mechanical impurities from entering the final pass of diesel engine, when refueling with sucker or self-flow method, it is better to filter with fine cloth or other filter material.

So how to store diesel oil is also important.

Title: Re: Could diesel be made clean?
Post by: teragram on 05/07/2019 23:02:36
The maximum power obtainable from modern electric motors is limited by their temperature rise. You can water-cool a motor to optimise its continuous-power to weight ratio, and allow short-term overdrive of around 20% of max continuous for takeoff. This is common with aircraft engines which have cruise (optimum fuel consumption), METO ("maximum except takeoff") used for continuous climb, and MAX2MIN settings for getting off a short runway. Might just be useful for road transport, particularly for heavy goods vehicles.The "range extender" logic baffles me. If your car needs say 50 horsepower to maintain 60 mph, then you need a 50 HP electric motor AND a 50 HP petrol engine for when the battery runs out. Either that, or you have to run say a 10 HP engine continuously to trickle charge the battery, and in either case carry enough liqjuid fuel to run the car for x miles at 60 mph where x is the range extension. 

I mentioned the BMW i3 because I know it is what used to be called a "series hybrid", and because I know someone who owns one. The series hybrid is where the petrol engine is not mechanically connected to the vehicle transmission, and can only produce electrical energy to charge the main battery and/or power the electric motor (as you describe). The 10hp engine in your description is apparently rated at 33HP (25KW), while the main electric drive motor is rated  at 168HP (125KW) or 184HP (137KW) depending I think on model. The point is that the electric motor does all the work of directly driving the vehicle, for accelerating, cruising, hill climbing, and town traffic, and contributing to braking by regeneration. It does all this admirably with only one gear (even for reversing)  and no clutch , friction or hydraulic. But this is what electric motors do. I like to say that my Nissan Leaf can go from 0 to 90mph in 1st gear, it can also go from 0 to 90mph in top gear.
The average energy consumption of an electric car is 330Watts per mile. In theory, a comparatively small petrol engine/generator can maintain the state of charge (SoC) of the battery fairly effectively, without having to cope with high torque and power requirements.
How successful this is in real life I'm not sure, but the i3 and it's peers are called "range extended" because the preferred mode of use is to charge the battery from mains, and only call the petrol engine into play if the vehicle cannot reach a charging point before the battery is exhausted. Many people (including my i3 owner friend) find that the journeys are such that the petrol engine is never called into action.
According to Wiki, the fuel consumption of the i3 operating on petrol only is about 50mpg. Not brilliant by todays standards, but I have yet to determine whether the car can be driven with a fully charged battery, and with the petrol engine doing what you suggest, keeping the battery SoC healthy. Again, Wiki says that BMW claims a fuel consumption figure of 400mpg!! Whether this figure is obtained by using the petrol engine as a "trickle charger" I can't say, although it smacks of smoke and mirrors.
A couple of general points:-
I prefer to use KW instead of HP (incidentally, why PS these days?), and
We seem to have drifted from the original topic somewhat, "Can Diesel be made clean?"
With regard to that, I think "No", even with all particles and NOX etc removed, petrol and diesel engines convert atmospheric oxygen into CO2.

Title: Re: Could diesel be made clean?
Post by: alancalverd on 06/07/2019 00:17:48
330 W/mile is not a measure of energy consumption. 2.5 megajoule/mile (around 60 mpg) is a good target for a diesel engine in a small-to-medium car. The electrical consumption of an equivalent car will be less because the inefficient bit, the generation of electricity, has been done somewhere else.

CO2 is not a pollutant: it is essential for life.
Title: Re: Could diesel be made clean?
Post by: Bored chemist on 06/07/2019 13:21:15
CO2 is not a pollutant: it is essential for life.
So is water, but that doesn't stop people drowning.

The average energy consumption of an electric car is 330Watts per mile.
No it isn't
Title: Re: Could diesel be made clean?
Post by: teragram on 06/07/2019 18:21:18
330 W/mile is not a measure of energy consumption. 2.5 megajoule/mile (around 60 mpg) is a good target for a diesel engine in a small-to-medium car. The electrical consumption of an equivalent car will be less because the inefficient bit, the generation of electricity, has been done somewhere else.

CO2 is not a pollutant: it is essential for life.

GUILTY AS CHARGED! Thanks for everybody for pointing out my mistake. The average consumption of an electric car is 330WATT HOURS per mile.
The discussion as I am aware was not about the efficiency of electric cars versus ICE powered cars, but I think that the inefficient part is not the generation of electricity,  generators have a very high efficiency. Using heat engines to power the generators is the inefficient part. The nearer we approach total electricity generation without burning stuff, the less will be the importance of thermal efficiency.
Title: Re: Could diesel be made clean?
Post by: alancalverd on 07/07/2019 11:10:09
That's about 1.2 MJ/mile, roughly half the end-user energy consumption of an equivalent diesel, when running on electricity alone. Exactly as expected.

The problem arises when you introduce a range extender or build a standard "half-and-half" hybrid: you are carrying twice the engine weight and using the same 50%-efficient prime mover. Friends with a classic Prius are pleased if they get more than 35 mpg now that the battery is approaching middle age. The useful power output is around  60 kW, compared with 110 kW  from a standard 1.9 liter/ 50 mpg diesel. It is indeed a delight to drive in town, very quick and quiet off the mark up to 30 mph, but on the open road you can definitely feel  the consequences of weight minimisation and the need to overtake with caution. Clearly designed with the Californian speed limit and emissions laws in mind.

I'm more impressed with my neighbour's electric-only BMW, provided you aren't in a hurry to go anywhere at short notice. Overnight charging gets her to the office smoothly and quietly, and the acceleration and roadholding are more like a Tesla than a milk float, but if she has to visit a client more than 100 miles away, there's an ancient petrol-driven Renault for serious motoring!
Title: Re: Could diesel be made clean?
Post by: teragram on 08/07/2019 17:51:43
I think the Prius didn't quite fulfil it's promise on fuel economy. I agree it came into existence to supply the market in America. The early versions were powered by an Atkinson cycle engine, which is slightly more efficient than a traditional 4stroke. I don't know whether that engine type is still in use.
I have a confession. My electric car is the early Leaf which only has a 24KWh battery. I had to keep my old Peugeot 1.6 Diesel to keep my wife quiet when planning the 420 mile trips to see her grandchildren in Scotland. If only I could afford an EV with 300mile range, and manage the journey with only one stop for charging each way. I'm now far too old for that to happen.
Title: Re: Could diesel be made clean?
Post by: RandyWilliams on 13/07/2019 13:00:02
I'm waiting for it
Me too
Title: Re: Could diesel be made clean?
Post by: syhprum on 14/07/2019 08:02:33
Pferdestärke (PS) is German for Horse power, slightly different  1% as it is based on SI units
Title: Re: Could diesel be made clean?
Post by: alancalverd on 14/07/2019 08:13:39
And on that subject, it is only just beyond living memory that the streets of London were ankle-deep in horse sh1t and the  traffic jams lasted for days. But as it was organic and inefficient, I guess those were the Good Old Days that the green lobby wants to replicate. 
Title: Re: Could diesel be made clean?
Post by: Bored chemist on 14/07/2019 11:01:24
I guess those were the Good Old Days that the green lobby wants to replicate. 
Guess again.
Pferdestärke (PS) is German for Horse power, slightly different  1% as it is based on SI units
Thus far, that's the most interesting thing I have read in this thread.
Title: Re: Could diesel be made clean?
Post by: teragram on 14/07/2019 18:12:28
Pferdestärke (PS) is German for Horse power, slightly different  1% as it is based on SI units

I see, thank you for that.
Title: Re: Could diesel be made clean?
Post by: alancalverd on 14/07/2019 20:56:28
Quote
from: alancalverd on Today at 08:13:39 I guess those were the Good Old Days that the green lobby wants to replicate.
Guess again.
Not a guess. I was briefly involved in a pro-horse anti-car group until I pointed out that the horse, standing still in a field, produced as much CO2 in a year as a small car driving 10,000 miles.
Title: Could diesel be made clean
Post by: BeJimmiecot on 02/09/2019 14:58:53
The wankel is very smooth and can rev very high, but fuel economy has always sucked a bit.  But theres good power to weight ratio to be had.  The Mazda 13b rotary was a popular choice for experimental aircraft that had need of high hp/w.

IIRC, a 4-stroke diesel is about as efficient as an internal combustion engine can be made, efficiency being defined as mechanical power output per mass of fuel burned.