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Bombardier's gas turbine powered IC125 replacement is a bit girly – so can we have the real deal they are testing in Canada
Frankly, the Bombardier gas turbine poweer Jetrain, unveiled at Railtex was a disappointment.
For some reason, I had assumed that we would be offered a version of Bombardier's prototype 5,000hp gas turbine powered High Speed Fossil Fuel Locomotive which made its inaugural test run at La Pocatiere, Canada in November. This uses a tractionised version of the Canadian Pratt & Whitney PW150 turboprop.
Instead Bombardier has teamed up with my old chums Turbomeca. This French manufacturer's
Makila II turbine, originally developed for helicopter applications, was the basis of the Turbotrain multiple units for French Railways and export.
Jetrain is a straight IC125 replacement and would be formed with eight or nine coaches between twin 3 200hp Bo-Bo power cars. Each power car would have two Makila II 1,600hp turbines, each driving two axles on the adjacent bogie via a Voith hydraulic transmission.
This turbine/transmission combination is identical to that used in the Turbotrains so it should be well sorted.
Each power car would also have a 500kW diesel generator set to provide auxiliary power. And because firing up a gas turbine for a few minutes is not efficient or desirable, the diesel generators would be able to move the train through an electric motor on the hydraulic transmission.
Bombardier quote the weight of the Jetrain power car at ‘under 70 tonnes'. The IC125 power car, rated at 2250hp, has a weight of 68 tonnes.
So why am I disappointed. Well, for a start 3,200hp isn't that impressive when 40 years ago you could buy a 3,300hp diesel loco on a 16.5tonne axle load. Yes, I know we are talking Bo-Bo now versus Co-Co then, but surely we should be looking for significantly more power than a Class 91 in a 21 st Century High Speed Train?
There is also that hydraulic transmission driving through four axles. Adhesion is an issue at high speed and I wonder whether mechanical drive can provide wheel slip protection with a fast enough response.
Now, back in nineteen mumble mumble, when our founder editor Geoffrey Freeman Allen sent back by my youthful effort proposing a 4000hp Bristol Proteus powered gas turbine locomotive, he was obviously right to do so because gas turbines guzzled fuel compared with a diesel engine. But technology has improved, and Turbomeca tell me that the Jetrain would use 5% more fuel than an IC125 with its original Paxman Valenta diesel engine.
Now I always raise a mental eyebrow when an engine manufacturer quotes percentages rather than specific fuel consumption (SFC) figures. General Motors is the classic example, each new engine always being x% more fuel efficient than its predecessor.
And taking a 30 year old design as Jetrain's yardstick is a bit disingenuous, since the diesel engine in a new generation IC125 replacement, whether power car or underfloor, would be around 10% more fuel efficient than the Valenta.
That fuel consumption is seen as an issue is reflected in the proposed driving technique. All four turbines would be used for acceleration, with one or more shut down, and I checked that they meant shut down and not just idling, in the cruise.
This suggests to me that Bombardier have forgotten why the Valenta had problems in IC125 service and why putative replacements flopped. Even on a straight railway like the East Coast Main Line an IC125 is forever braking and accelerating, what Paxman's Chief Engineer called ‘binary driving'.
It's a long time since I worked on industrial gas turbines but I remember that they didn't like the thermal shock of being shut down and restarted. And even with today's turbocharged cars you are supposed to let the engine idle at the end of a journey to stop heat soak damaging the turbo's bearings.
Of course, traction engineering is all about trade-offs and a higher fuel consumption would be acceptable if the gas turbine offered something diesels couldn't do. Established traction engines didn't want the Deltic, but at the time it was the only way to get that much power in a loco.
So what does the Makila offer? Well, with only rotating shafts rather than lots of reciprocating bits it should offer higher reliability, lower maintenance and higher availability than a diesel. According to Turbomeca, the Makila needs only 1hr maintenance every 80,000 miles. Overhauls at intervals of up to 1million miles take the train out of service for six hours.
Meanwhile, First Great Western has issued an OJEC notice inviting expressions of interest in the supply of 20 ‘diesel fuel powered' train sets. A pre-series set would start test in January 2004, with the whole fleet in revenue earning service by January 2006.
Maximum speed is quoted at 140mile/h, with higher acceleration than an IC125 while maintaining ‘the minimum of axle loading'.
FGW has been evaluating gas turbine power for high speed trains for over two years and the specification clearly reflects their preference. Note, in particular the requirement ‘to meet or exceed the current and emerging legislation on environmental emissions' which could favour the gas turbine which is particularly clean.
Clearly FGW is aware that it risks repeating the old familiar story of high tech whiz kids from other industries coming to show the backward railways just what new technology can do – and falling flat on their faces. Thus the OJEC Notice differentiates between bidders offering diesel powered trains and those with ‘an alternative propulsion solution to the traditional diesel engine powered rail vehicle'.
To avoid disappointment, the latter will be required to demonstrate traction and rolling stock experience for their products. Also required will be a minimum of 15 years experience of rail vehicles capable of speeds up to 225 km/h and project management capability. So that's Bombardier then.
Overall Captain Deltic rates Turbotrain as a nice try but no cigar. A 4000hp diesel generator car at each end of a train with distributed three phase traction is still his option to beat. And if Alstom had the first idea about the future development of the UK inter-city market they would have a demonstrator in build right now.