[97_Octane]

Excellent thread! I have been following this method since recent times only. Just hope I haven't done too much damage as all my 3 cars are turbo diesels. But sometimes when I'm running late for college I have to drive hard for most of the route but I slow down in the last 500 metres (due to bad roads ). In this case, I can idle the engine for only about 15 secs (to avoid running late and being restricted entry to the class ) after reaching the parking. I know this is bad but better than shutting it off immediately right?

[Jeroen]

Originally Posted by Sutripta

The piston engine reacts much faster to load changes compared to turbines. The steam generator is a particularly bad example, but the fault there actually lies with the boilers, not so much the turbines. Which is why thermal power plants are meant to provide baseline load. With other systems (notably hydro) meant to cater to the peak requirements.
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The boilers have a time lag to produce extra volume of steam. You can shove in a few extra burners and push the fuel controls to max, but there is no instant response. Steam turbines, at least in my experience, are susceptible to thermo shock. I've sailed on a few steam ships and it would take us several hours to go from what was known "maneuvering full speed" to "cruise full speed". That was mostly due to avoiding thermos shock. Large marine diesel, by the way have to be handled in an identical way.

As you correctly say steam plants are extremely good at providing base load. You can also design and run them extremely efficient. Many power stations around the world would have gas turbine generator sets for handling peak load. Just hit start and as soon it has completed its starting sequence you go to full power!

I've worked with several gas turbine sets in various marine applications,(electricity generation and fire fighting monitors).

See this picture I took years ago:



These two fire monitors were both powered by its own 4500HP gas turbine.
I was always amazed on how quickly you can them run them up to full power. And how small they are, but that's a very different story altogether.

Jeroen

[SKavuri]

Originally Posted by Sutripta

Some random (and possibly OT) thoughts.

As an example, larger steam turbines (for electricity generation) are Hydrogen cooled.

Regards
Sutripta

I am sure you meant the generators are Hydrogen cooled, not the Turbines.

[Sutripta]

^^^
Offshore oil rig support vessel?

Fire pump prime movers are always a special case. Incidentally the Coventry Climax was originally designed as a fire pump engine.

The GT can hit full power from a cold start very quickly without any damage. This is different from response to 'throttle' inputs, where the piston engine is superior.

In any large lump of metal, thermal management becomes critical. More than the turbines, boiler life is considerably shortened if one makes car like demands of it.

Regards
Sutripta

[Jeroen]

Originally Posted by Sutripta

^^^
Offshore oil rig support vessel?

Fire pump prime movers are always a special case. Incidentally the Coventry Climax was originally designed as a fire pump engine.

The GT can hit full power from a cold start very quickly without any damage. This is different from response to 'throttle' inputs, where the piston engine is superior.

In any large lump of metal, thermal management becomes critical. More than the turbines, boiler life is considerably shortened if one makes car like demands of it.

Yes, these are the fire monitors of the SmitLLoyd 2. See http://www.smit-lloyd.com/2.htm. One of the first supply vessels that was modified for fire fighting duty on the North sea. Those two monitors throw some 2500 tonnes of water per hour 140 meters up! If we pointed them straight aft, the vessel would move forward at 6 knots! Specially designed Lips joystick system that controlled propellors, thrusters and rudders to keep the vessel in place.

Did two tours on her as engineer somewhere in the early eighties. Some of the picture in the above link were take by me during these tours. My name still shows up as the photographer, some thirty years later!

You are correct, throttle input response on piston engines is much better. All GT require spool up time.

I have some experience running steam plans. My Chief Engineers certificate is actually valid for both diesel as well as steam driven plants. Although boiler life is influenced by rapid changing demands there are other factors that have far greater influence. However, a big thermal shock on the turbine could well damage beyond repair, with no immediate effect on the boiler. Maybe a bit less life time left, that's all. Having said that, having to install tubes in a boiler is a big pia job!

Typically steam plants are dimensioned in such a way that the boiler in terms of continuous steam production is already slightly over dimensioned compared to turbine output required. Even so, most boilers are able to produce a peak loading of around 110-115% continuous loading. That peak loading comes at a high price in terms of reducing boiler life time. Peak loading, used to be or maybe still is, I'm not exactly current on this, limited to four hours a day. For exactly this very reason, aggressive reduction of boiler life.

Most of my "steam knowledge" is a bit dated these days, so I'm happy to hear if and how boiler design has improved over the years.

Jeroen

[swiftdiesel]

While on this topic can someone explain what's the difference between VGT and Variable Nozzle Turbo (VNT)? Checked a couple of entries on Wikipedia but there wasn't any clear explanation. I know the Innova's diesel has a VNT while other engines like the K9K and Multijet have the VGT. Which is better and what are the reasons for adopting either of them? Like why not a VGT 2.5 D-4D or a VNT 1.3 Multijet? Thanks!

[Sutripta]

Originally Posted by SKavuri

I am sure you meant the generators are Hydrogen cooled, not the Turbines.

You are right!

Originally Posted by Jeroen

Although boiler life is influenced by rapid changing demands there are other factors that have far greater influence.

You are the expert!
(Waay OT: Tube leakage detected in boiler running near capacity. What would be the SOP? And what is generally done here in India?)

Regards
Sutripta

[Jeroen]

Originally Posted by Sutripta

You are the expert!
(Waay OT: Tube leakage detected in boiler running near capacity. What would be the SOP? And what is generally done here in India?)

Expert, far from it, my knowledge is more than thirty years old, and I just amend it by a few google searches to brush up or get confirmation that by and large things are still as they were.

Now on the tube leakage. I really cant remember the exact numbers, but a certain percentage of leakage is as such no problem as long as you are able to keep replenishing. Too much leakage can lead to permanent damage, but I'm not exactly sure what the criteria is. But when you get to that point the SOP is "shut down" and fix the tube.

Fixing the tube can be done in several ways. Depends a bit on the type of boiler, which tube is leaking etc.

The most rigorous one is replacing the damaged tube. Big job, requiring specialized tools and people who now how to execute the job. The more simple one is to localize the damaged tube and plug it. Could be as easy as hammering in a plug in both ends of the tube. Simple and straightforward. Obviously, you can't keep plugging endlessly, because with every tube you plug, you effectively reduce the capacity of the boiler. In addition you might create additional problems in the boiler. No water/steam going through a tube also means no cooling. So it can't be done on all tubes.

On ships we would mostly just hammer in plugs. Especially when we had problems whilst at sea. Easy and fast. Use the exact same technique on repairing all heat exchangers (tubed heat exchangers obviously)

No idea what is done in India. My (limited) experience is with Marine Boiler Systems. And some insights from former colleague marine engineer who went from sea to shore and run electrical plant with huge steam systems. Have visited a number of them. Somewhat different from marine systems

Jeroen

[sriramr9]

Originally Posted by GTO

Abusing your turbocharger can affect its longevity. With time, the turbo will become less effective. Take care of your turbo so that it gives your engine adequate boost and thus, an enjoyable driving experience for years to come.

Thanks a lot GTO. I have three of questions.

1. During cold start will it not be wise to keep the aircon off and turn it on later while driving and after the engine reaches desired temperature, i use the radiator water temp guage in to judge it. As during cold start does turning the aircon not put a load directly on the alternator which may transfer to the running engine??

2. This is slightly off topic but wanted to merge my question to the first one, can we turn ON and OFF the a/c while driving based on need, i hear mixed reviews on this, need more clarity as to what effect can this have to engine on long run.

3. is it advisable to let the engine idle with air con on tough traffic signals like minimum wait period of 300 seconds and multiple halts till crossing happens. i see every car, be it cab indica, innova, swift ritz, i10, vento all in idle with air con on. i do generally turn off the engine after 75 seconds but wonder as why no one ever realizes the same ?

4. (car equipped with turbocharger) A scenario where, while on the move in cruising speed, due to broken roads if one had to slow down abruptly due to bad road patches and in the event of down shifting what if by mistake the engine shuts down, improper release of clutch (happens sometimes), in that cse to avoid turbo damage, what if the car is started again immediately & revved beyond 2000rpm to spool the turbo will it help in the lubing process ?

[Jeroen]

Originally Posted by sriramr9

Thanks a lot GTO. I have three of questions.

1. During cold start will it not be wise to keep the aircon off and turn it on later while driving and after the engine reaches desired temperature, i use the radiator water temp guage in to judge it. As during cold start does turning the aircon not put a load directly on the alternator which may transfer to the running engine??

2. This is slightly off topic but wanted to merge my question to the first one, can we turn ON and OFF the a/c while driving based on need, i hear mixed reviews on this, need more clarity as to what effect can this have to engine on long run.

3. is it advisable to let the engine idle with air con on tough traffic signals like minimum wait period of 300 seconds and multiple halts till crossing happens. i see every car, be it cab indica, innova, swift ritz, i10, vento all in idle with air con on. i do generally turn off the engine after 75 seconds but wonder as why no one ever realizes the same ?

4. (car equipped with turbocharger) A scenario where, while on the move in cruising speed, due to broken roads if one had to slow down abruptly due to bad road patches and in the event of down shifting what if by mistake the engine shuts down, improper release of clutch (happens sometimes), in that cse to avoid turbo damage, what if the car is started again immediately & revved beyond 2000rpm to spool the turbo will it help in the lubing process ?

On 1: More advanced ECU's will disable the AC during the start cycle and only switch on once the engine idles. Once it idles the AC does put a bit of extra load on the engine, but nothing much. Your typical AC on a midsize saloon would probably pull the equivalent off 6-8 HP. Not much to get exited about for you or the turbo. Typically all AC's are automatically disabled below approx 4oC anyway.

Coolant temperature is not the best way to really judge what is happening temperature wise. It's the oil temperature which is relevant for your engine and turbo. And that temperature could lack behind the coolant temperature. Especially with engines with large volumes of oil. Better indication can be, if you have one the oil pressure indicator. Only when the engine oil reaches its normal operating temperature will that start showing normal readings too.

On 2: No worries, you can switch on and off as often as you like. Other than wearing out the on/off switch and possible the AC clutch you have nothing to worry about this engine wise. Accelerating away from a traffic light puts a considerable higher load on the engine, than switching your AC on.

On 3: If you want to keep cool, keep the engine and AC running at all times.
If you want to save fuel and the environment, switch the engine off.
There is nothing else to it.

On 4: Don't worry these things happen all the time. If you do it a couple of thousand times maybe you should worry.

In general and I think I said this before; There are a couple of dozen guys on this forum who worry about the idling rule for Turbo's. There are literally tens of millions other guys out there who never even heard about the rule and are pottering around with their turbo's never getting idled. At least not on purpose.

Reading through this thread you'd think the world would be awash with damaged turbo's. The fact is that a failed turbo due to not adhering to the idling rule is a very rare occurrence indeed.

So just go by what the owner manual advises and if you forget once in a while, just don't worry about it.

Enjoy your car.

Jeroen

[headers]

Originally Posted by Jeroen

In general and I think I said this before; There are a couple of dozen guys on this forum who worry about the idling rule for Turbo's. There are literally tens of millions other guys out there who never even heard about the rule and are pottering around with their turbo's never getting idled. At least not on purpose.

Reading through this thread you'd think the world would be awash with damaged turbo's. The fact is that a failed turbo due to not adhering to the idling rule is a very rare occurrence indeed.

Wow - very well said

This thread is educative how TCs work and is not a gospel to follow IMHO

No offense to thread OP or otherwise

[parsh]

Originally Posted by swiftdiesel

While on this topic can someone explain what's the difference between VGT and Variable Nozzle Turbo (VNT)? Checked a couple of entries on Wikipedia but there wasn't any clear explanation. I know the Innova's diesel has a VNT while other engines like the K9K and Multijet have the VGT. Which is better and what are the reasons for adopting either of them? Like why not a VGT 2.5 D-4D or a VNT 1.3 Multijet? Thanks!

Both are essentially same, used alternatively and named specifically by various designs and manufacturers. You could get a nice explanation in the article here http://paultan.org/2006/08/16/how-do...geometry-work/ and also some basic incite at Wikipedia at http://en.wikipedia.org/wiki/Variabl...y_turbocharger

[subratasenn]

I have an interesting point to make. I started following the idle rule after reading GTO's valuable thread at start and stop. Also stopped switching off the ignition at red lights unless I know I have to wait for more than two minutes.
This has noticeably increased the mileage of my car in city traffic. Previously my Etios Liva Diesel was consistently returning 17+ km to a litre. Now, after following the idle rule it's 19+ km to a litre. (last two refills tank full method after starting the practice).
So, this idling thing not only saves my turbo, but also saves fuel I suppose!

[Pancham]

Thanks for this thread but I am a little confused here. Do I need to practice this for my Hyundai i20 PETROL ??

[coolboy007]

Originally Posted by Pancham

Thanks for this thread but I am a little confused here. Do I need to practice this for my Hyundai i20 PETROL ??

No buddy you dont need to, it is only required for turbo charged cars - petrol and diesel. i20 petrol is a normal aspirated engine without any turbo and hence you dont need to do any idling.