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The EMD SD24 was a six-axle (C-C) diesel-electric locomotive built by General Motors' Electro-Motive Division of La Grange, Illinois between July 1958 and March 1963. A total of 224 units were built for customers in the United States, comprising 179 regular, cab-equipped locomotives and 45 cabless B units. The latter were built solely for the Union Pacific Railroad. The SD24 was the first EMD production locomotive to be built with an EMD turbocharged diesel engine, sixteen months before the four-axle (B-B) model GP20. Power output was 33 percent higher than the of the concurrent Roots blower-equipped SD18s with the same engine displacement, per axle, limited by the traction motors then available (this limitation was eliminated in the ''40-Series''). Nevertheless, the turbocharged SD24 provided full rated power at all altitudes, which the Roots-blown SD18 could not provide. In terms of sales, the SD24 was only a moderate success, and few had long service lives in SD24 configuration (though a few rebuilds are still in operation), but the SD24 was a milestone in EMD locomotive development and the forerunner to today's high-powered six-axle locomotives.〔 EMD thought the Duluth, Missabe & Iron Range Railway would want to start purchasing the SD24 and sent one to the DMIR painted in the road's livery. The DMIR did not end up purchasing the SD24 and the demonstrator went to the Union Pacific Railroad.〔http://trainlife.com/magazines/pages/141/10171/september-2004-page-21〕 == EMD-type Turbo-Compressor (Turbocharger) == The turbocharger was the then-new EMD mechanically assisted turbo-compressor. During engine startup, and at lower power levels, during which there is not sufficient exhaust heat energy to drive the turbine fast enough for the compressor to supply the air necessary for combustion, the engine drives the compressor through a gear train and an overrunning clutch. At higher power levels, the overrunning clutch is disengaged, and the turbo-compressor operates as a true turbocharger. It is possible for the turbo-compressor to revert to compressor mode momentarily during commands for large increases in engine power. Turbocharging provides higher horsepower and good running characteristics at all altitudes. Turbocharging also improves fuel consumption and reduces emissions. Previous Union Pacific experiments with turbocharging had utilized multiple Elliot〔Elliot turbochargers are now serviced by http://www.sinorengine.com/httpdocs/elliot_turbocharger.php〕 or Garrett AiResearch turbochargers feeding the usual pair of Roots blowers. EMD's mechanically assisted turbocharger eliminated the need for the pair of Roots blowers and also integrated the turbocharging function from two (Elliot) or four (AiResearch) smaller add-on turbochargers into one much larger, turbo-compressor (turbocharger) with intercooling. The introduction of the EMD-type turbocharger was successful and all subsequent SD series were offered with this turbocharger, although not all models within a series were offered with turbocharging (e.g., the ''38'' sub-models within the ''40 Series'' were Roots-blown). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「EMD SD24」の詳細全文を読む スポンサード リンク
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