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Kiha 391 performance test data

These schemas are copies from original hand-written data derived test runs of kiha 391 on Hakubi, Sanyo lines in 1972 to 1973.

Tractive effort (actual measurement)

 Each plot shows the relation between the speed and tractive effort by each notch. Solid straight lines are the planned theoretical tractive effort.

The measured efforts are higher than planned except for the full notch-7. The starting effort at notch position 1 or 2 is too weak to overcome the starting resistance so the train could not start. To reduce the friction loss of the transmission, the hydraulic jack was equipped to the reduction gear box. This system increased the tractive effort at low notch. At notch position-4, 250 kg improvement was shown on this schema.

At notch position-7, derived tractive effort was somewhat lower than planned.
Probably this might have been caused by the high temperature (nearly 30 degrees Celsius).
Engine output usually
changes according to the ambient temperature. The rated output usually shown is the output at the temperature of 15 degrees Celsius. The output of a simple cycle gas turbine decreases  when the absorbing air temperature rises. 




Fuel consumption

The right graph shows the relation between the speed and fuel consumption ratio by each notch. Y-axis unit If a plot goes in the upper area of Y-axis, it means the fuel consumption is bad.Unit of the Y-axis is g/PS・h. If a 1000 hourse power  engine's fuel consumption ratio is 300 g/PS・h, 300 kg fuels are consumed in one hour.
The fuel consumption worsens at low notch positions and low speeds. This feature is especially specific to a single speed direct drive gas turbine car. 

Acceleration test

 This list shows the actual measurement of the acceleration test. The used notch position was 6, not full notch position. (Full position is 7.)
The start-up characteristic is  very bad, it took about 11 to 15 seconds (in this case 12 seconds) to rise the power turbine torque and start the train. A poor response of a gas turbine is well known, but this value is too large. After the engine control unit was improved, the lag time was shortened to 4 seconds and this is the acceptable lag time in the train operation planning.

The train reached the speed of 63 km/h 60 seconds after starting, 85km/h 90seconds after starting. This was not bad performance in comparison to DMUs in those days. But series 181 DMU "Tsubasa", consisted of 11 motive car and 1 trailer could reach the speed of 73 km/h 60 seconds after starting, 91km/h 90seconds after starting and the performance of kiha 391 was somewhat unsatisfactory.
There are different points of view. If the initial speed is set to 45 km/h, this speed was the speed limit to pass through turnouts usually used in local main lines, the time required to reach the speed of 95 km/h (top operating speed  in these lines) is 60 second at notch position 6. It took 66 seconds by series 181 at full notch position. This means the low acceleration performance of the single speed direct drive turbine railcar at lows speed and comparably good performance at middle to high speed. A turbine test driver, who was also the driver of series 181 "Yakumo" stated his impression that the turbine had a better acceleration than series 181 after it got some speed.

If kiha 391 starts with notch position 7, it has better performance, of course.
Computer simulations shows this clearly, at the rated output is set to 1050 horse power (same as kiha 391 7 notch position), this train reaches the speed of 73 km/h 60 seconds after starting, 99 km/h 90seconds after starting. If the output is set to 1250 horse power, 30 minutes rating, each reached speed is 85 km/h and 112 km/h, far more faster than DMUs in those days.



Running curves

These are running curves drawn for test runs between Seto to Higashiokayama, outbound Sanyo line in 1972.







This is the notification from the Yonago Railload Administration of old JNR concerning the test run of kiha 391 in 1972.


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