Gas turbine-electric locomotive
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A gas turbine-electric locomotive, or GTEL, is a locomotive that uses a gas turbine to drive an electric generator or alternator. The electric current thus produced is used to power traction motors. This type of locomotive was first experimented with in 1920 but reached its peak in the 1950s to 1960s. The turbine (similar to a turboshaft engine) drives an output shaft, which drives the alternator via a system of gears. Aside from the unusual prime mover, a GTEL is very similar to a diesel-electric. In fact, the turbines built by GE used many of the same parts as their diesels.
A turbine offers some advantages over a piston engine. There are few moving parts, decreasing the need for lubrication and reducing maintenance costs, and the power to weight ratio is much higher. A turbine of a given power output is also physically smaller than an equally powerful piston engine, allowing a locomotive to be very powerful without being inordinately large. However, a turbine's power output and efficiency both drop dramatically with rotational speed, unlike a piston engine, which has a comparatively flat power curve. Turbines also produce a great deal of noise.
Union Pacific operated the largest fleet of such locomotives of any railroad in the world, and was the only railroad to use them for hauling freight. Most other GTELs have been built for small passenger trains, and only a few have seen any real success in that role.
After the oil crisis in the 1970s and the subsequent rise in fuel costs, gas turbine locomotives became uneconomical to operate, and many were taken out of service. This type of locomotive is now rare.
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[edit] Union Pacific's turbine fleet
Union Pacific has long sought the biggest and best locomotives available. In the 1930s a pair of steam turbine locomotives were tried out but ultimately rejected. Even before World War II Union Pacific had been adding diesels to its roster, but these were mostly for passenger trains. The idea of lashing together four diesels to equal the power of a single steam locomotive was unappealing, so the search began for something bigger. General Electric had been building gas turbines for aircraft and proposed using something similar to create a more powerful locomotive. Union Pacific had discovered that the maintenance costs for a locomotive were independent of the locomotive's power output. Using a smaller number of more powerful locomotives would thereby save money.
Union Pacific decided that the best way for the turbine locomotives to realize their potential would be to put them on mainline freight trains. The long uninterrupted runs and relatively high speeds would keep the turbines turning at high speeds. The turbines were considered for use on the Los Angeles-Salt Lake City route, but their high noise levels resulted in them being banned from operating into Los Angeles.
Union Pacific operated the largest fleet of turbine locomotives of any railroad in the world. The turbines were used extensively; at one point Union Pacific claimed that the turbines hauled more than 10% of the railroad's freight. Their fuel economy was rather poor, as the turbine consumed roughly twice as much fuel as an equally powerful diesel engine. This was initially not a problem, since Union Pacific's turbines were fueled by Bunker C heavy fuel oil. This highly viscous fuel was far less expensive than Diesel, but difficult to handle. When cold, its consistency was likened to tar or molasses. To solve this problem, a heating apparatus was built into the fuel tenders to heat the fuel to 200 °F (93 °C) before being fed into the turbine. Soot buildup and blade erosion caused by corrosive ashes plagued all of the turbines.
The turbines were delivered in three main groups after extensive testing of a prototype. Union Pacific intended to use the turbines to replace the famous Big Boys which were about to be retired at the time.
1948
After Union Pacific expressed interest, Alco-GE built a prototype, GE 101. After tests in the Northeast, it was renumbered UP 50. Painted in Union Pacific Armour Yellow, UP 50 began an extensive round of tests. Union Pacific never took possession of this locomotive, however. This was one of the few internal combustion-powered locomotives used in North America that had a cab at each end. The cabs themselves resembled the FA units being built by Alco-GE at that time. The sides of the locomotive had numerous air intake louvers which could be opened and closed in varying patterns.
It was a carbody unit with a B+B-B+B wheel arrangement. The turbine produced 4800 horsepower (3.6 MW), of which 4500 hp (3.4 MW) was available for traction. This power output was more than double that of diesel-electric locomotives of that era. A small diesel engine was also installed inside the unit. This was used for moving the unit around when uncoupled and for starting up the turbine. The turbine would first be spun up to starting speed, then combustion would be started using the onboard diesel fuel supply. Once the turbine was running, the fuel supply would automatically switch to the Bunker C fuel oil. This machine weighed 500,000 pounds (230,000 kg) and was over 80 feet (24 m) long.
1952
Units 51 to 60 were delivered to the Union Pacific. These were essentially identical to the prototype except that they had cabs at only one end. These and later turbines were nearly always equipped with fuel tenders converted from old steam locomotive tenders, with a capacity of 23,000 US gallons (87,000 l). A heating apparatus was installed to make sure that the viscous fuel would flow properly. The tenders were also equipped with MU connections so that trailing diesel locomotives could be controlled as well. The turbines rarely operated alone; most usually operated with at least two diesel locomotives in their consist, as protection. Should the turbine fail en route, the diesels could be used in allowing the train to clear the main track.
UP 57 was briefly converted to burn propane and was equipped with a pressurized tank car as a tender. This fuel burned cleanly but was more difficult to transport. No other conversions were attempted.
1954
Units 61 to 75 were delivered to the Union Pacific. These were visibly different from the previous generation because of the addition of external walkways on the sides of the locomotives, earning them the nickname "verandas" and making them hybrids of carbody and hood locomotives. The turbine and electrical equipment were essentially the same, though the variable side louvers were replaced by fixed ones.
1958-1961 Units 1 to 30 were delivered to the Union Pacific. These units, nicknamed "Big Blows" because of their high noise levels, were very different from the previous generations. A larger turbine produced 8500 horsepower (6.3 MW), and the unit consisted of two permanently coupled six-axle units, giving a C-C+C-C wheel arrangement. The first unit contained the cab, auxiliary diesel engine, and other control equipment. The second unit contained the turbine and electric generators. Together, the locomotive looked like an A-B set, which was reinforced by the numbers assigned to the units. The two halves of no. 19, for instance, would be numbered 19 and 19B. These turbines eventually displaced units 51 to 75 from service. There had also been problems with fuel filters clogging on the earlier turbines, so it was decided to filter the fuel before filling up the locomotive fuel tanks and the tender.
Rumors persist that the Big Blow turbines were uprated to 10,000 hp (7.5 MW). This may stem from the fact that at sea level the turbines could produce that much power. The electrical equipment, however, could only handle 8500 hp (6.3 MW). Also, the turbines in revenue service always operated above sea level. Even so, the turbine design used in these units is still the most powerful prime mover ever installed in a locomotive.
Bunker C's cost advantage waned as the plastics industry began to find uses for it and improved "cracking" techniques allowed the oil (which had previously been considered waste) to be converted to lighter fuel grades. The oil crisis in the 1970s and the rise in fuel costs highlighted the inefficiency of the turbines. All were out of service by 1970. Their running gear was recycled into the GE U50 series of locomotives. Parts from units 51 to 75 were used to make the U50, and parts from units 1 to 30 were used to make the U50C.
Two of the turbines survive - UP 26 in Ogden, Utah, and UP 18 at the Illinois Railway Museum. Several of the tenders were retained and converted to hold water for use with Union Pacific's operating steam locomotives, UP 844 and UP 3985.
In October 1961, Union Pacific constructed an experimental GTEL of their own, using an Alco PA-2 as a cab, the chassis of a GE W-1 class electric locomotive (bought for scrap from the Great Northern) as the second unit, and an modified turbine prime mover from the 50 to 75 series. The setup was numbered 80, but changed to 8080 in 1965 to avoid conflict with the EMD DD35s being introduced. The bizarre-looking consist had a bizarre wheel arrangement as well: A1A-A1A+B-D+D-B, i.e. 18 axles of which 16 were powered. A "centipede" steam locomotive tender was rebuilt with a coal crusher to pulverize and feed the coal to the turbine. Power output was estimated at 7000 hp (5.2 MW). The original diesel engine in the PA was retained and produced 2000 hp (1.5 MW) and the turbine produced the additional 5000 hp (3.8 MW). The blade erosion and soot buildup problems encountered in the earlier locomotives were magnified with UP 80/8080. Grinding coal into fine particles was also troublesome. Any oversized coal particles could damage the turbine blades. Ultimately, UP 80/8080 was declared a failure, and this "contraption" was dismantled. The conventional gas turbines each racked up well over a million miles in revenue service, by comparison the coal turbine prototype ran less than 10,000 miles before being stricken from the UP roster.
UP 26 photographed by Jim Munding, all others courtesy of Don Ross
[edit] Other GTELs
Union Pacific was not the only user of GTELs. United Aircraft built the Turbo passenger train, which was tested by the Pennsylvania Railroad and later used by Amtrak and VIA Rail.
SNCF (French National Railways) uses a number of gas-turbine trainsets, called the Turbotrain, in non-electrified territory. These typically consisted of a power car at each end with three cars between them. Turbotrain was in use up until 2005. The first TGV prototype, TGV 001, was also powered by a gas turbine, but steep oil prices prompted the change to overhead electric lines for power delivery.
The British Rail APT-E, prototype of the failed Advanced Passenger Train, was turbine-powered. Like the TGV, later models were electric instead. This choice was made because British Leyland, the turbine supplier, ceased production of the model used in the APT-E.
Amtrak purchased two different types of turbine-powered trainsets, which were both called Turboliners. The first set were similar in appearance to SNCF's Turbotrain, though compliance with FRA safety regulations made them heavier and slower than the French trains. None of the first set of Turboliners remain in service. Amtrak also added a number of similarly named Rohr Turboliners (or RTL) to its roster. A number of refurbished RTL IIIs are currently in service.
In 2002, Bombardier Transportation announced the launch of the JetTrain, a high-speed trainset consisting of tilting carriages and a locomotive powered by a Pratt & Whitney turboshaft engine. No JetTrains have yet been sold for actual service.
