by Helen
Wed Jul 12th, 2006 at 08:47:24 AM EST
When LD died in 2003 the chapter of Great Steam Locomotive Engineers was brought to a close. It is arguable that they were never many in number: Becoming a chief engineer in any large organisation is rarely gifted to innovators. Richard Trevithick, George Stephenson, OVS Bullied and of course, the greatest of them all, Andrée Chapelon (as described by DoDo). But LD Porta was a distinguished member of the club.
His demonstration piece was his very first rebuild in 1947. Sanctioned by President Peron himself, he transformed an old 4-6-2 wheelbase locomotive into a 4-8-0 that was internally completely different from any engine that had gone before.
All of the steam circuit, the means by which high pressure steam moves through the engine from generation to exhaust, was completely re-modelled. He took Chapelon's ideas of promoting efficiency through the use of large-bore pipes and over-sized valves for low reistance to even greater heights.
However, it was his development of the coal gas circuit that was Porta's great contribution to steam engine efficiency. Previous understanding of the heat exchange from burning coal was that it burnt in the grate. So air would be intruduced through the base of the grate by means of vents to provide oxygen to feed the fire. This would, at high speed, create a white hot furnace from a hurricane force blast of air that would frequently lift the coal directly from the fireman's shovel and fire it unburnt from the chimney itself. It was not uncommon to see flames coming from the chimney of a hard-working engine as if the entire locomotive was on fire.
Porta was the first to realise that it was these gases that were being burnt as they were driven from the coal that was providing the heat and not the coal itself. If these gases were being burnt anywhere else in the engine apart from the designated combustion chamber of the firebox, then it wasn't going to happen efficiently. So he re-designed the firebox with an enlarged brick arch (burn catalyst), a reduced draught through the fire-grate and with the innovation of most of the air being introduced above the fire. This was the first use in a locomotive of the Gas Producer Combustion System common to most industrial coal burners and provided a much more effective combustion capability.
Finally he finished off with the use of a Kylchap chimney that was the most effcient way then known of dragging these exhaust gases through the engine (it is the steam being evacuated from the cylinders that "entrains" the coal gases out of the chimney).
The results were remarkable. On test the engine was found, in non-optimal track conditions, to have a thermal efficiency of 11.9%. A truly phenomenal figure considering that most British steam locomotives built in the same era was below 8%. It achieved a projected tractive effort of 52000 lb, fully 10,000 more than the most powerful British engine of similar type (Thompson A2).
And this was his first effort !!
Sadly, politics and the oil lobby were against him. Argentina largely abandoned the development of steam very soon after. He did some work breifly for the American coal producers and thereafter jobbed around the world, essentially frittering his genius away until David Waredale of South African Railways contacted him in the late 70s. Between them they re-designed one of the old 25-NC express train warhorses and created the class 26 "Red Devil". Although SAR were belatedly following the world in energetically eliminating steam which curtailed a full examination of the engine's capabilities, preliminary studies showed that, with a reduction of fuel consumption of nearly 40%, thermal efficiency had been increased to over 15%..
With diesel fuel increasing in price, who knows whether LD Porta's work may achieve some posthumous revitalisation ? But his legacy remains as one of the great might-have-beens in railway history.
