Gas Producer Combustion System - The KLR way

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Much of what follows has been culled from the KLR website at http://www.kirkleeslightrailway.co.uk

As the KLR was gradually extended and the service became more intensive problems which had previously been annoying become a real issue. These problems being clinker and smoke production. With Clayton West station being surrounded by houses keeping smoke to a minimum is a must. It was felt the best way to tackle these problems was to draw on the work of L.D.Porta, David Wardale and others and introduce a Gas Producer Combustion System to the line's locomotives.

The fleet of KLR locos have a simple application of GPCS that has not seen secondary air holes cut in the firebox. This may occur in the future but for now all secondary air is admitted via the firehole. The comparatively large firehole opening relative to the small grate area has helped make the system a success. (This factor would limit the success of this specific form of GPCS on locomotives with a much larger grate area as the firehole does not dramatically increase in size as a locomotive gets larger.) All locomotives have restricted primary air flow but retain standard firebars which are fixed. None of the locos yet has a rocking or drop grate. Clinker control steam is admitted to the primary air flow from the outside rather than via pipework under the grate as on, for example, the RFIRT locos in Argentina.

The system has made the locomotives easy to fire whilst the control of clinker has turned them into much more reliable performers. The lack of smoke and considerable reduction in firebed particle entrainment make the locomotives much more pleasant to travel behind in open and semi-open coaches making up part of the KLR fleet. Another benefit of having lower firebed temperatures is the increased live of the firebars.

This type of firehole door is fitted to Fox and Badger. This shows the door closed with the secondary air regulator closed tight (the disc in the middle of the door) on Badger whilst is was parked cold in the shed at Clayton West. April 12 2004
This type of firehole door is fitted to Fox and Badger. This shows the door closed with the secondary air regulator closed tight (the disc in the middle of the door) on Badger whilst is was parked cold in the shed at Clayton West. April 12 2004

This view shows the door closed with the secondary air regulator opened wider than is normal in service. However it serves to show the setup opened and the airholes in the door itself. April 12 2004
This view shows the door closed with the secondary air regulator opened wider than is normal in service. However it serves to show the setup opened and the airholes in the door itself. April 12 2004

With the secondary air regulator removed the hole in the door is clear as are the air ducts behind. Note also the pin below the thread to prevent the secondary air regulator from rotating when opened. If it were free to rotate shutting it fully would be a problem. April 12 2004
With the secondary air regulator removed the hole in the door is clear as are the air ducts behind. Note also the pin below the thread to prevent the secondary air regulator from rotating when opened. If it were free to rotate shutting it fully would be a problem. April 12 2004

With the exception of Hawk all the locos have a similar cast and fabricated section on the fire side of the firehole door. This is used to direct the secondary air evenly over the fire and impart extra turbulence with the swirl shaped plates in the ducts (these being the fabricated sections.) The secondary air ducts have an area of approximately 2% of the grate area. Again this is on Badger. April 12 2004

With the exception of Hawk all the locos have a similar cast and fabricated section on the fire side of the firehole door. This is used to direct the secondary air evenly over the fire and impart extra turbulence with the swirl shaped plates in the ducts (these being the fabricated sections.) The secondary air ducts have an area of approximately 2% of the grate area. Again this is on Badger. April 12 2004

A close up of one of the air ducts with the turbulence inducing swirl shaped plate. On a monitor resolution of 1024x768 this is somewhat bigger than it is in reality. April 12 2004
A close up of one of the air ducts with the turbulence inducing swirl shaped plate. On a monitor resolution of 1024x768 this is somewhat bigger than it is in reality. April 12 2004

Visible here is the fixed area primary air damper through which all primary air is admitted to the fire and through which ash is removed. On the opposite side of the engine is a similar opening but this is fitted with a door to allow cleaning but is left shut during normal running. The black pipe at the top of the opening is perforated on the firebox side and supplies clinker control steam. This clinker control steam is made up from the air brake pump exhaust, a percentage of cylinder exhaust steam and also receives steam when the blower valve is open. This is Badger. April 12 2004

Visible here is the fixed area primary air damper through which all primary air is admitted to the fire and through which ash is removed. This damper area is approximately 35% of the grate area. On the opposite side of the engine is a similar opening but this is fitted with a door to allow cleaning but is left shut during normal running. The black pipe at the top of the opening is perforated on the firebox side and supplies clinker control steam. This clinker control steam is made up from the air brake pump exhaust, a percentage of cylinder exhaust steam and also receives steam when the blower valve is open. This is Badger. April 12 2004

The admission of clinker control steam on Fox is much the same as on Badger. Here, during a stop steam can be seen escaping after the air pump had exhausted. During times when the blower valve is open or the engine is powering this steam is sucked up under the fire by the primary air flow. There is little significant leakage at this time. April 11 2004

The admission of clinker control steam on Fox is much the same as on Badger. Here, during a stop steam can be seen escaping after the air pump had exhausted. During times when the blower valve is open or the engine is powering this steam is sucked up under the fire by the primary air flow. There is little significant leakage at this time. April 11 2004

On Hawk the primary air is admitted at the rear of the ashpan as is the clinker control steam. As can be seen there is a regulating valve on the steam flow which allows alteration, on shed, to cope with the different clinkering characteristics of various coals. That said the KLR tries to always use the same source to reduce such alterations to a minimum. It is normal for KLR locomotives to run with openings in the delivery pipe adding up to about 7 or 8% of the total blast nozzle area. The locomotives are also arranged such that steam from the blower, when is use, is also used to control clinker. The delivery being based on 15 to 20% blower nozzle area. This also prevents ash being drawn into the exhaust passages such a partial vacuum develop in them. April 12 2004
On Hawk the primary air is admitted at the rear of the ashpan as is the clinker control steam. As can be seen there is a regulating valve on the steam flow which allows alteration, on shed, to cope with the different clinkering characteristics of various coals. That said the KLR tries to always use the same source to reduce such alterations to a minimum. It is normal for KLR locomotives to run with openings in the delivery pipe adding up to about 7 or 8% of the total blast nozzle area. The locomotives are also arranged such that steam from the blower, when is use, is also used to control clinker. The delivery being based on 15 to 20% blower nozzle area. This also prevents ash being drawn into the exhaust passages such a partial vacuum develop in them. April 12 2004

A fire arch is important in ensuring a long flame path and good gas mixing which all adds up to efficient, and clean, combustion. All the locos currently have steel arches rather than firebrick arches. On such small locomotives retaining the maximum firebox volume is crucial to the use of steel is very important. It should also be noted that these arches ARE NOT supported from above with extensions from the crown stays as is normal on larger locomotives to prevent the arches from warping. In such small fireboxes deformation has not been a major problem and when it has occurred the arch has been refitted the other way up ! This view shows the arrangement on Owl. April 11 2004

A fire arch is important in ensuring a long flame path and good gas mixing which all adds up to efficient, and clean, combustion. All the locos currently have steel arches rather than firebrick arches. On such small locomotives retaining the maximum firebox volume is crucial to the use of steel is very important. It should also be noted that these arches ARE NOT supported from above with extensions from the crown stays as is normal on larger locomotives to prevent the arches from warping. In such small fireboxes deformation has not been a major problem and when it has occurred the arch has been refitted the other way up ! This view shows the arrangement on Owl. April 11 2004

The firehole door on Owl, when seen in April 2004, was of a new design on test. The door opens vertically and is held open by a spring. When in the running position, as seen here, the door is held open by moveable metal catches. These can be removed to fully close the door but are designed to be awkward to adjust on the move to encourage GPCS operation ! On the fire side of the door is a air duct system as on Owl and Badger. However in this case all secondary air is admitted around the edge of the door with much being sucked behind the air ducting system. April 11 2004
The firehole door on Owl, when seen in April 2004, was of a new design on test. The door opens vertically and is held open by a spring. When in the running position, as seen here, the door is held open by moveable metal catches. These can be removed to fully close the door but are designed to be awkward to adjust on the move to encourage GPCS operation ! On the fire side of the door is a air duct system as on Fox and Badger. However in this case all secondary air is admitted around the edge of the door with much being sucked behind the air ducting system. April 11 2004

With the door open Owl gets some more coal added to the nice bright GPCS fire - there was certainly a lot of heat in there !! April 11 2004
With the door open Owl gets some more coal added to the nice bright GPCS fire - there was certainly a lot of heat in there !! April 11 2004

Of crucial importance to any steam loco is an efficient exhaust ejector. All KLR locos have a 4 nozzle Lempor arrangement, which incorporates a straight walled Kordina*, and has been fitted within the existing external chimney profile. The Lempor's fitted to all of the fleet are crucial to the success of the GPCS application. Without them a strong enough draft to could not be guaranteed. Once more this shows the arrangement on Badger. Note no use of spark arresting, the line at worst gets one lineside fire a year. Also of interest is that the blower nozzles are internally shaped to be converging/diverging as the blast nozzles are. The Lempor nozzles have a exit to throat ratio of 1.1:1. April 11 2003
Of crucial importance to any steam loco is an efficient exhaust ejector. All KLR locos have a 4 nozzle Lempor arrangement, which incorporates a straight walled Kordina*, and has been fitted within the existing external chimney profile. The Lempor's fitted to all of the fleet are crucial to the success of the GPCS application. Without them a strong enough draft to could not be guaranteed. Once more this shows the arrangement on Badger. Note no use of spark arresting, the line at worst gets one lineside fire a year. Also of interest is that the blower nozzles are internally shaped to be converging/diverging as the blast nozzles are. The Lempor nozzles have a exit to throat ratio of 1.1:1. April 11 2003

Not only has the application of GPCS and the Lempors made smoke a thing of the past and reduced clinkering to an almost insignificant amount but the locos are able to pull heavier trains. This fact can be attributed to the Lempor and Kordina improving cylinder efficiency but also the more complete combustion in the firebox. Whilst it was not a primary aim of GPCS adoption impressive reductions in coal and water consumption have been noted.

It is hoped in time to further improve the performance of the GPCS in light of experience and also to add secondary air holes in the firebox sides. However as ever with such work it is always a question of balancing time, money and the workforce to allow it to be done.

What the KLR shows to the world today is that GPCS can work outside of Argentina and South Africa, that is does not need to be complicated nor does it dictate serious visual alterations to locomotives. So the question has to be posed why is it not more commonly applied. Few preserved operations in the UK could honestly be able to say they never suffer with clinker problems - well here is the solution. Don't say you haven't been told !!

* During experimentation whilst working in China David Wardale found that a straight walled Kordina is more effective than a curved wall Kordina. It was found imparting a swirl to the exhaust steam actually impaired ejector performance. Ref: 'The Red Devil and Other Tales from the Age of Steam' by D. Wardale. Page 476

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