Our first post on this prototype locomotive gave some basic information and characteristics. Let's take a look this time at the powerplants used in this locomotive.
Here is a drawing of the gas turbine powerplant as shown in a Westinghouse sales brochure from 1947. At left are the two DC traction generators, coupled together; to the right is the reduction gearbox; the drive shaft enclosure seen running into the turbine compressor is actually at the center of the concentric air intake. The combustion chambers are individual, and expansion bellows can be seen placed between the chambers and the exhaust elbows. The exhaust elbows direct the hot combustion gas to the turbine, and finally the exhaust stack angles 90 degrees to direct exhaust gases through the roof.
According to the materials in the specification book, work on the Westinghouse Gas Turbine Locomotive project began in 1945, and rapid progress led to a test unit of the configuration seen here on this blog being constructed, with testing of this unit beginning in September, 1946. This test set was operated at Westinghouse until December, 1948 at which time it was modified and shipped to Arkansas to be used as a test and prototype natural gas pump. This modification was not a removal from the locomotive testing program; rather, the test imposed greater stress on the "hot" parts of the turbine from which Westinghouse could extrapolate data and develop modifications for locomotive service.
Each turbine contained a 23 stage axial compressor, 12 combustion chambers, and an 8 stage turbine. Combustion temperature was approximately 1350 degrees F. The turbine itself developed roughly 6000 HP, but roughly 4000 HP of this power was needed to drive the axial compressor, leaving 2000 HP available for propulsion and auxiliary needs on board the locomotive. The turbines burned Bunker C oil, as did the General Electric turbines built for the Union Pacific for freight service.
The March, 1947 edition of "Westinghouse Engineer" details some of the features, development, and problems with the prototype turbine set. Mentioned is the fact that the turbine sets had to endure fairly rapid combustion temperature changes ranging from 700F to 1350F in railroad locomotive conditions, that is, no load to full load. Westinghouse did not apparently tackle all of the problems associated with very rapid temperature and pressure changes, and the control system applied to the prototype locomotive (pneumatic throttle in cab, incidentally) was designed to limit the rate of increase of load to an acceptable value. Idle speed of the turbines was roughly 60 percent of the speed at full load. Our sources do not give a speed for the turbine rotors, although Westinghouse Engineer gives a generator armature speed of 1200 RPM at full load while the specification states 1150 RPM.
Starting of the turbines began with rotation of the whole machine by use of one of the traction generators as a motor. Test results in the lab indicated that 80 KW of cranking power (battery power) would bring an engine to operating speed in one minute, while 50 KW would do it in 1-1/2 minute. Operating experience with the prototype showed that total starting time for one turbine set was about 3-1/2 minutes.
Each turbine set drove, in addition to two traction generators, a 50 KW auxiliary generator, an exciter, and a 2 CDB Westinghouse air compressor. Westinghouse used a sophisticated combination of components including main exciters and YG-53A pilot exciters to match desired load characteristics (for train handling) to the peculiar speed-torque characteristics of gas turbine engines; the pilot exciters were belt driven like the aux generators / main exciters but mounted on the floor. One electrically driven auxiliary air compressor was also fitted on board, which could be either powered from the battery or from the auxiliary diesel.
At left, one of the two turbine sets manufactured for locomotive service. Note the application of lagging (insulation) and shielding to the production machines to be placed side by side in close proximity in a locomotive.
Next time, we'll cover the general construction of the locomotive and describe the overall equipment layout with the help of some large and never-seen diagrams from the specification book.