Uncle Roger and engine emissions

[jjb1970]

I received the latest Roger Ford e-mail last night (well, I noticed it in my in box last night), he is one of the few railway magazine columnists who is genuinely technically knowledgeable and I always enjoy his unsweetened analysis of technical matters. This time however I couldn’t help disagreeing with him on the matter of engines. For those who haven’t read his e-mail he comments on making engines less efficient to lower NOx emissions and remarks on a comment from the former chief engineer of EWS on the absurdity of making their class 66 engines burn more fuel in order to lower emissions.

 

Putting aside the unfortunate fact that if you were really worried about fuel efficiency then you wouldn’t buy EMD 710 engines and that he is conflating GHG and local pollution issues, Roger is correct that if you use techniques such as retarding timing to suppress NOx then you take an efficiency hit (you also generally take a CO and PM hit), but what he doesn’t remark on is that there were already mature technologies for lowering NOx without affecting engine efficiency in the 1990’s, principally selective catalytic reduction. And today engine builders can supply SCR units built into on-engine exhaust arrangements for the smaller large engines (if that makes any sense) used in rail applications. There are other techniques such as EGR, adding water to fuel, ultra high pressure pulsating injection etc. I’m slightly disappointed in Roger for seeming to regurgitate some of the spin put about a few years ago when we were told it’d be impossible to make compliant diesel trains for the UK market. I remember reading an article in Rail a few years ago and I’m pretty sure I knew the real author of certain sections as I recognised the syntax (it wasn’t the Rail journalist with their name in the by-line). Diesel engine emissions control was hardly a new discipline in the 1990’s when the 66’s were ordered, it’s a very mature discipline now and can actually be used to improve engine efficiency by tuning combustion for maximum thermal efficiency and then abating pollutants (these days downstream systems have a pretty small footprint and if well designed and packaged hardly add anything).

 

I’d expect this sort of stuff from lesser journalists but I find it a little disappointing that Roger Ford seems to be swallowing spin about the evils of emissions control.

[The Stationmaster]

Drop him a line to put him right JJB - unless he's changed he has always been interested in getting proper technical information related to railway subjects (and more importantly prepared to listen).

[Edwin_m]

That paragraph did ring a few alarm bells with me to, although I can't claim to be an expert.  I remember reading many years ago (90s or even 80s) that US diesels had to have their timings retarded to comply with California emissions regulations, but it's good to know that's one environmental either-or that we no longer have to worry about. 

[jjb1970]

I was also slightly disappointed that he made the classic mistake of referring to nitrous oxide as NOx. NOx is nitrogen oxide (NO, NO2), not nitrous oxide which is N2O.

[DCB]

Sorry I'm with Roger on this.

Its pretty much a given that to lower N0x you hurt efficiency and fuel consumption.  Its why 1980s 2 litre Diesel cars could get 70mpg on the motorway and euro 4 compliant 2 litre diesel cars struggle to manage 50 mpg at the same speed.

Makes you think major oil companies must be funding these so called "Environmentalists"  Blanking EGR is usually worth 5% to 10% improvement in fuel consumption as efficient combustion produces N0x.   

[jjb1970]

The reason some engines reduce fuel efficiency to reduce NOx emissions is because they use techniques such as retarded timing and EGR, Roger's comments are seemingly predicated on an assumption that the only way to lower NOx is to use such techniques. SCR decouples NOx created during combustion from NOx emitted from the exhaust outlet and allows you to optimise the engine for maximum combustion efficiency without worrying about NOx. I worked with SCR fitted Wartsila medium speed diesels built in 1994 that reduced NOx by about 97% with no adverse impact on fuel consumption, by 2008 they'd replaced their catalyst blocks once and had worked reliably and effectively for over 20 years. Another point to note is that after an initial drop in the late 90's as NOx emission standards took effect the fuel consumption of large engines again improved as engine designers developed their engines even using some of the NOx control techniques which hit fuel consumption. What was more of an issue was limiting CO and PM.

 

Something to note is that a 5 - 10% improvement does not close the gap between 50mpg and 70mpg in an automotive engine.

[david.hill64]

I recall that some work was done a few years ago looking at the efficiency of diesel engines used by UK rail vehicles. The work was done I think by Ricardo, well known for their expertise in internal combustion engines. IIRC the conclusions were that there was not much that could be done to improve the US designs, but mods could made to the mostly German designs that would result in significant improvements. I have no idea if these were implemented or not.

[Hesperus]

The big drop in car fuel economy has more to do with increased weight.  Compare an 80s Citroen BX 1.9 diesel estate at 1220kg with a C4 Picasso 2.0 Hdi (that has less space inside) at 2040kg.  I'm not certain the fuel economy has fallen much though as my partners 2011 Focus 1.6 Tdci (1352kg) is about 30% better on fuel than my 1994 Peugeot 405 turbo diesel (1210kg).  Neither the BX or 405 will achieve 70mpg in normal use but the Focus will on a long run.

[Dunsignalling]

43 minutes ago, Hesperus said:

The big drop in car fuel economy has more to do with increased weight.  Compare an 80s Citroen BX 1.9 diesel estate at 1220kg with a C4 Picasso 2.0 Hdi (that has less space inside) at 2040kg.  I'm not certain the fuel economy has fallen much though as my partners 2011 Focus 1.6 Tdci (1352kg) is about 30% better on fuel than my 1994 Peugeot 405 turbo diesel (1210kg).  Neither the BX or 405 will achieve 70mpg in normal use but the Focus will on a long run.

 

Not helped by the accompanying drastic increase in tyre sizes, and thus rolling resistance, either.

 

John

Edited March 21, 2019 by Dunsignalling

[Classsix T]

Not to mention the drag coefficient on a C4 sized "bus".

 

C6T. 

[jjb1970]

Engine technology has advanced hugely since the 80's. Common rail and advanced fuel injection systems, variable timing, multiple stage turbo charging, software based engine management, tools such as FEA and improvements in materials technology have reduced large engine weight massively whilst maintaining strength and durability, thermodynamic modelling tools have facilitated much greater optimization of the combustion process etc. 

[Classsix T]

Absolutely jjb, and I always enjoy your posting on the subject, if you'll forgive my exhaust driven smoke blowing..!

 

One of my favourite reads has been 'The Diesel Impact On British Railways'. A fascinating subject to me, the figure that stands out the most in the time from the '50s to now is the advancement in horsepower per  cylinder.

 

Obviously emissions are the topic of the time nowadays, I personally would appreciate your views on (within forum rules, natch) policy regarding the demonisation of and eradication of the good Doctor's superb invention and what the hell happened to bio-fuel solutions to make such more carbon neutral?

Although you're more than likely to have covered that elsewhere!

 

C6T. 

Edited March 22, 2019 by Classsix T

[Nearholmer]

Seconded.

 

And, if you'd be prepared to give us the benefit of an e-lecture on the subject of "what is in diesel exhaust emissions and how does each component arise", I for one would be grateful.

 

Kevin

[roythebus]

My limited experience of this subject is in the bus industry. Take the "standard" London Routemaster bus as built with the AEC 9.6 litre diesel. the RM is still the lowest unladen weight per passenger seat bus built with an unladen weight for the 72 seat RML at 7760kg, just over 100kg of bus per seated passenger. Fuel consumption can be up to 12 mpg on town work and up to 15 mpg with the later Cummins conversions. The AEC 9.6 gives about 115 bhp, the Cummins with 6900 gives 125 bhp. when derated to London spec but gets the 15mpg.

 

Modern "box" buses typically have an unladen weight of around 11000kg for maybe 72 seated passengers. fuel consumption on these can be as low as 3mpg. when these were first introduce in the early 2000's I had many discussions with other operators about the effect on the atmosphere about these new low floor buses using more diesel than the older ones. I'm told the latest London deckers do about 5mpg, the "low emission" kit accounting for a sizeable increase in weight. On the other side, the engines are even smaller with the Mercedes OM0900 type engine being used to deliver in excess of 250bhp to move a big decker along. however, with the low servie speed of buses in towns the low emission kit never gets hot enough to work properly!

 

The problem with trains is that they spend a lot of time idling. the southern diesel fleet which my son is in charge of spends an inordinate amount of time idling. Shut-down isn't really an option at somewhere like Victoria as a flat battery can cause lots of delays; not only that the time taken for the computers to shut down and reboot doesn't really help.

 

Edited to add: an article in a recent edition of Transport Engineer stated that modern diesels now emit less harmful emissions that their petrol counterparts, despite what politicians say.

Edited March 21, 2019 by roythebus

[Davexoc]

All pretty irrelevant really, because if we were bothered we would all catch the bus or train.

Alternative is drive single occupancy the most gas guzzling largest SUV status symbol your income can afford and have the next best one down for the wife for the school run and coffee mornings with the like minded mummys.....

 

 

[jjb1970]

I think it is a little sad that Rudolf Diesel's name is now a dirty word, thanks to a certain scandal and the consequential reaction against diesel engines. Whatever we might think of the diesel engine in today's world and when considering the future, Rudolf Diesel was a brilliant engineer. That said, I think the world is changing and the future is low emissions technology. Emissions and emissions control paid my mortgage for a few years and gave me a good career, however I think that it makes much more sense to just not make the pollution in the first place rather than expend effort making pollution and then abating it. In the case of railways there is a technologically mature and available alternative to diesel engines - electrification. At one time a criticism of that idea was that it just moved the pollution around, from the train itself to a power plant, but even then power plants were pioneers in emissions abatement and optimising thermal efficiency. Now the grid is making solid progress from fossil fuels to low emission forms of generation, not just carbon (which is driving the changes) but adopting renewable energy also avoids an awful lot of other pollutants being emitted. I think the sad thing about the dieselisation of railways was that what should have been a transitional technology between steam and electric trains became a longer term solution. I don't think anybody could seriously question the benefits of diesel locomotives relative to steam locomotives in just about every way except initial upfront cost but ultimately they still consume fossil fuels and still emit CO2 as well as a swathe of local pollutants which doesn't really help the world or public health. There are applications for which the internal combustion engine remains the most appropriate technology for now and maybe far into the future after switching to low carbon or carbon free fuels. However, switching to low carbon/carbon free fuels may address GHG impact but not necessarily other pollutants, for example a hydrogen fuelled internal combustion engine still emits NOx and may also emit hydrogen peroxide. Funnily enough, this is another area where I disagree with Roger, he is fond of joking about bionic duckweed and clearly sees interest in alternative fuels as something of a joke, however there are potential alternatives and a lot of effort is now going into commercialising some of the alternatives for the simple reason that some industries such as shipping know they need a low carbon energy carrier and also appreciate that retaining internal combustion engines fuelled with alternative fuels is the most viable low carbon pathway at the moment (although I actually see a lot of potential in electrification of shipping using batteries and/or fuel cells). There are some interesting proposals for circulating CO2 systems based on methanol fuel, the carbon and oxygen would be split from the hydrogen as liquid CO2 prior to combusting hydrogen in an engine with the CO2 being recombined with hydrogen at a fuel plant to make more methanol for fuel. Why do this? Methanol is a liquid fuel and relatively easy to transport, store and handle, avoiding the issues around liquid hydrogen (which is within 20C of absolute zero), avoids cryogenic plant. Another hydrogen carrier is ammonia, but that's nasty stuff.

However, I digress, sorry. Regardless of all the above it is actually not especially difficult to abate NOx and it does not have to bring fuel efficiency down

[Covkid]

1 hour ago, Davexoc said:

All pretty irrelevant really, because if we were bothered we would all catch the bus or train.

Alternative is drive single occupancy the most gas guzzling largest SUV status symbol your income can afford and have the next best one down for the wife for the school run and coffee mornings with the like minded mummys.....

 

 

 

Not really. When you live in South Staffs and have to be at your desk in Birmingham city Centre at 0600 there is no other option. And forget it on Sundays because the Arriva bus depot doesn't do anything, and the gates remain locked. 

 

The introduction of emissions charging for Birmingham means at least one colleague with a 14 plate diesel will be impacted, and another with a 61 plate diesel plans to retire anyway. 

[Covkid]

2 hours ago, roythebus said:

The problem with trains is that they spend a lot of time idling. the southern diesel fleet which my son is in charge of spends an inordinate amount of time idling. Shut-down isn't really an option at somewhere like Victoria as a flat battery can cause lots of delays; not only that the time taken for the computers to shut down and reboot doesn't really help.

 

Edited to add: an article in a recent edition of Transport Engineer stated that modern diesels now emit less harmful emissions that their petrol counterparts, despite what politicians say.

 

With respect, those trains should never have been built with hydraulic transmissions.

They should have been diesel electric transmissions, so that they could be easily modifiable to use the juice rail where possible.  

[mikejames]

this thread raises a lot of interesting points about alteratives to diesel engines etc

but I don't have the engineering background to really understand the options

 

Can anyone point me to a good source of (free) background reading about these

alternative energy vectors and their pluses and minuses

 

thank you

regards

mike j

[Covkid]

15 minutes ago, mikejames said:

this thread raises a lot of interesting points about alteratives to diesel engines etc

but I don't have the engineering background to really understand the options

 

Can anyone point me to a good source of (free) background reading about these

alternative energy vectors and their pluses and minuses

 

thank you

regards

mike j

 

You are in the same boat as me Mike !!! We are semi reliant on the media for information, from which we then have to make our our decisions on what is and isn't true, and what is and isn't viable.  It seems that diesel is becoming a dirty word and alternative power sources are sought. We are told diesels will be "outlawed" from 2040 which leads us to suppose that sales of diesel powered vehicles will fall off between now and then. 

 

I hear of "electrification" in aviation and in the motor industry which basically means using electricity as a means of propulsion. Obviously the new diesel / dual powered trains rolling off production lines for TPE, ARN, GA etc were ordered several years ago, with then state of the art diesels, but what is the future ? I find it very difficult to accept that the brand new EWR (East West Rail) is being planned as a non electrified line when it connects two of England's centres of learning - Oxford and Cambridge  There are suggestions it might be electrified later, but that is an unacceptable situation to be in, for engineers seeking possession of a line for engineering work.  Much easier and more convenient to build a brand new railway completely (notwithstanding Oxford-Bletchley is on existing formation) than subsequently close it to the users to erect catenary and power systems.  

 

Quite what kind of non electric trains are being planned for this route is intriguing, ruling out diesel it can only really be hydrogen or battery in my view.      

 

 

[kevinlms]

11 hours ago, Covkid said:

 

With respect, those trains should never have been built with hydraulic transmissions.

They should have been diesel electric transmissions, so that they could be easily modifiable to use the juice rail where possible.  

On the contrary, electric locos should have overhead, rather than a 'juice rail'.

[Nearholmer]

East West Rail as a missed opportunity in terms of electrification deeply bugs me too.

 

The big issue with 25kV electrification is the cost of the structures, and to some degree the cost of grid intakes, and the challenge of electrifying this route in an affordable way ought to be viewed as an interesting engineering challenge to be overcome ........ something along the lines "you've got £nnM with which to do it; now find a way.", rather than being put-off to the indefinite future. I'm very confident that if the question was put in the right way, which it never seems to be, clever people could cut the cost of electrification very significantly, by going back to first-principles on "holding the wires up" and using on-train energy stores to get over the difficult bits.

 

However, and more broadly, when it comes to freight, there is an issue, in that it is hard to justify using anything other than a straight diesel loco on heavy-long-haul until a very high percentage of the route to be used is electrified (at which point using an electro-diesel or electro-battery cuts the mustard), and a huge mileage of freight routes isn't electrified, and doesn't seem to be in prospect of electrification, so big straight-diesels seem t have a long future, even accounting for the pace of battery development.

[Nearholmer]

And, getting slightly into the 25kV OLE vs 750V third-rail thing .......

 

From a train traction package point of view, it really doesn't matter much, either or both are easily digestible, given a modern electric drive-train.

 

What does seriously matter is that the drive-train should be electric, rather than mechanical/hydraulic. because it is vastly, vastly easier to implement regenerative braking and on-train energy storage, and multi-mode, with such a system.

 

The Class 230s that are about to go into service Bedford-Bletchley are more or less an electric tram with diesel-alternator on board; the power electronic package they use was originally designed for electric trams, so that family of trains has an easy and direct route to become multimode (electrification of any flavour; battery; diesel; hydrogen; any combination you fancy). People are too keen to deride them as "secondhand underground trains", when what is being created there is actually some very good new wine in an old bottle.

[Edwin_m]

The existence of mechanical and hydraulic transmissions implies that they are better or (more likely) cheaper than electric ones for relatively low power applications such as DMUs.  This probably isn't surprising because the rating is similar to trucks and buses and the components are likley to benefit from the vast economies of scale that presents. 

 

However two things are now likely to happen, although it's unclear how quickly.  Firstly the automotive industry will move to electric transmissions, whether for battery, hydrogen or hybrid, so these will start benefitting from the same economies of scale.  Secondly the reducing demand for straight DMUs will make it unviable for manufacturers to produce bespoke designs for them - we thought that was going to happen ten years ago but it hasn't yet.  So it's most likely that DMUs will become an adjunct to suppliers' primarily electric products - the platform will accommodate the diesel module, the electric module, the hydrogen module and the battery module in any combination all feeding power to traction motors.  Ironically Vivarail is the only supplier in the UK market who offer this choice today.

[phil-b259]

17 hours ago, jjb1970 said:

Funnily enough, this is another area where I disagree with Roger, he is fond of joking about bionic duckweed and clearly sees interest in alternative fuels as something of a joke, however there are potential alternatives and a lot of effort is now going into commercialising some of the alternatives for the simple reason that some industries such as shipping know they need a low carbon energy carrier and also appreciate that retaining internal combustion engines fuelled with alternative fuels is the most viable low carbon pathway at the moment (although I actually see a lot of potential in electrification of shipping using batteries and/or fuel cells).

 

The whole 'bionic duckweed' thing is less about the actual technologies involved and more about the fantasy land way the DfT and ministers have latched onto them as an excuse to NOT do anything as regards electrification.

 

We saw this in the first couple of decades after privatisation where the UKs electrification skills base was allowed to wither away to practically nothing as ministers and Whitehall mandarins insisted it was 'unnecessary' and 'future fuel technology' would render any investment in adding OLE as being 'poor value for money'.

 

These days I think even Roger acknowledges that the likes of Hydrogen fuel cells or battery power can have a role to play on our railways - its just that such solutions are no substitute for proper electrification of our most intensively used routes

 

The problem is to politicians electrification = expensive investment by the state*, where as 'on board' or 'self powered' solutions are far more attractive to HM Treasury as its the private sector leasing companies which have to stump up the cash.

 

 

*Not helped by NRs miss-management of the attempts to get it going again - but then again what do you expect when Government inaction had totally destroyed the necessary skills base