Open Rails Steam Parameters

Aim - this section describes the "optimal" settings for steam related parameters in Open Rails (OR) ENG files. Example settings are based upon NSWGR standards.

If you wish to provide any feedback on this page, please use the contact page. It would br great to have some feedback as this helps to ensure the accuracy of the information and models.

Index

Introduction

Steam Production and Use

Key Open Rails Parameters for Steam Locomotives

Sample Steam Code

Boiler Parameter Calculator - Saturated

Boiler Parameter Calculator - Superheated

Steam and Water Usage Calculator

         Steam and Water Usage - Imperial

         Steam and Water Usage - Metric

Useful References


Introduction

The two key elements impacting the performance of a steam locomotive are

  • Tractive Effort
  • Steam Production and Usage

For realistic performance it is important to set the Open Rails steam parameters to calculate the correct values.

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Steam Production and Use

The steam locomotive relies upon the principle of converting steam energy to tractive effort through the cylinders. Therefore sufficient steam is required to be generated to match the amount of steam being used by the cylinders to drive the wheels around.

Steam generation is impacted by two heat transfer processes:

  • Fuel combustion
  • Steam production

The amount of heat energy produced by fuel combustion is impacted by a number of factors, including fuel energy, oxygen drawn into the fire (draft). In designing a locomotive, the priniple design factor for fuel combustion was the size of the grate area.

The amount of heat energy available to convert water into steam is determined by the heating area in contact with both the fire, and the boiler water. In a typical locomotive boiler, the boiler water was in contact with parts of the firebox, and also the flue tubes taking smoke and heat through the boiler to the smokebox at the front of the locomotive, and out of the stack. Thus the evaporation area of the locomotive was another key factor, which was determined by calculating the area of the firebox, tubes, arch tubes and combustion chamber in contact with the boiler water.

If you do not have values for Grate Area, or Evaporation Area or Boiler Volume, then you can use the Boiler Parameter Calculator - Saturated or Boiler Parameter Calculator - Superheated to calculate some sutable values.

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Key Open Rails Parameters for Steam Locomotives

The key parameters that impact upon the performance of a steam locomotive are described on the following web page.

Standard Settings for ENG and WAG Files (updated Feb 2017)

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Sample Steam Code

The code parameters shown below are those that are required to define a steam locomotive within Open Rails. They should be set using known parameters so that the optimal accuracy of operation can be obtained. Depending upon the type of locomotive some of the parameters can be omitted from the ENG file, for example, non-geared locomotives will not require the geared section below.

When inserting values in these parameters it is recommended that you use the appropraite units of measure.

Comment ( *** General *** )
Type ( Steam )
ORTSSteamLocomotiveType ( Compound ) Comment (Used to define type of locomotive)
WheelRadius ( 19.0in )
NumWheels ( 4 )
ORTSDriveWheelWeight ( 177000lb )
Sanding ( 25mph )
IsTenderRequired ( 1 )

Comment ( *** Cylinders *** )
NumCylinders ( 2 )
CylinderStroke ( 15in )
CylinderDiameter ( 17.25in )
LPNumCylinders ( 2 ) Comment (Used to for compound locomotives)
LPCylinderStroke ( 26.0in ) Comment (Used to for compound locomotives)
LPCylinderDiameter ( 25.0in ) Comment (Used to for compound locomotives)

Comment ( *** Boiler *** )
ORTSSteamBoilerType ( Saturated ) Comment (Used to define type of locomotive)
BoilerVolume ( 297.0ft^3 )
ORTSEvaporationArea ( 2225.0ft^2 )
MaxBoilerPressure ( 200psi )
ORTSSuperheatArea ( 612.0ft^2 ) Comment (Not required for saturated locomotives)
MaxSteamHeatingPressure ( 80psi ) Comment (Not required for locomotives without steam heating installed)

Comment ( *** Fire *** )
ORTSFuelCalorific ( 13700btu/lb )
ORTSGrateArea ( 33.0ft^2 )
SteamFiremanMaxPossibleFiringRate( 3000 )
ShovelCoalMass ( 14lb ) Comment (For manual fireman?? )

Comment ( *** Fuel *** )
MaxTenderCoalMass ( 10600lb )
MaxTenderWaterMass ( 28571lb )

Comment ( *** Gearing *** ) Comment (Not required for non-geared locomotives)
ORTSSteamGearType ( Fixed )
ORTSSteamGearRatio ( 2.18 1.0 )
ORTSSteamMaxGearPistonRate ( 700 )

Make sure that you test your settings with the performance tests described on the testing page.

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Boiler Parameter Calculator - Saturated

The methodology and factors used in this calculator is based on the work "Locomotive Ratios" (found on page 67 of Locomotive handbook - American Locomotive Company (Alco) ) by F. J. Cole (Chief Consulting Engineer) of the Alco Company, and others for designing locomotives. The figures produced by this calculator appear to be conservative in some instances (or higher then sometimes seen in reality).

Tractive force factor is a constant that allows for pressure and friction losses between the steam locomotive boiler and the steam cylinder. This value often varied between different countries and railway companies - typically it appears to have been in the range between 0.7 - 0.9.

Note: The boiler volume, grate and evaporation area values produced by this calculator should only be used where data is not obtainable from known sources.

Insert the appropriate values and hit the calculate button

Dr Wheel Dia (in):   Cyl Dia (in):   Cyl Stroke (in):

Num Cyl:   Boiler Pressure (psi): Tractive Force Constant:

Results

General

Cyl Area (sq in):     Tractive Effort (lbf):
Saturated Steam
Max Hp: Max Steam (lb/h):     Max Coal (lb/h):
For insertion into ENG File

Copy and paste these parameters into the ENG File for a saturated locomotive.

Grate Area (sq ft):     Evap Area (sq ft):     Boiler Volume (cu ft):

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Boiler Parameter Calculator - Superheated Locomotives

The methodology and factors used in this calculator is based on the work "Locomotive Ratios" (found on page 67 of Locomotive handbook - American Locomotive Company (Alco) ) by F. J. Cole (Chief Consulting Engineer) of the Alco Company, and others for designing locomotives. The figures produced by this calculator appear to be conservative in some instances (or higher then sometimes seen in reality).

Note: These values should only be used where data is not obtainable from known sources.

Insert the appropriate values and hit the calculate button

Dr Wheel Dia (in):   Cyl Dia (in):   Cyl Stroke (in):

Num Cyl:   Boiler Pressure (psi):   Tractive Force Constant:

Results

General

Cyl Area (sq in):     Tractive Effort (lbf):
Superheated Steam
Max Hp:     Max Steam (lb/h):     Max Coal (lb/h):
For insertion into ENG File

Copy and paste these parameters into the ENG File for a Superheated locomotive.

Grate Area (sq ft):     Evap Area (sq ft):     Superheat Area (sq ft):     Boiler Volume (cu ft):

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Steam and Water Usage Calculator

The amount of water used by a locomotive will be proportional to the amount of steam used by the steam cylinders. In short, the steam used in each stroke of the piston will be determined by the "swept volume" of the cylinder (ie the volume of the piston calculated from the cylinder diameter and stroke), the pressure of the steam in the cylinder (which is influenced by the throttle and cutoff values), and the number of piston strokes in a period of time (ie the speed of the locomotive). A saturated steam locomotive will tend to use slightly more steam due to cylinder condensation effects condensing some of the steam and requiring additional steam to replaced steam condensed in the cylinder.

The calculator below can be used to calculate the approximate steam used by the locomotive at different operational settings (ie speed, working pressure, cutoff, and throttle). If the default values for the cutoff and throttle are used, this will represent the 'worst' case scenario for steam usage in the steam cylinders. It should be noted that steam can also be exhausted by other means, such as the whistle, safety values, compressor and cylinder cocks, which are not allowed for in the calculator. As can be expected, a locomotive traveling along a route will face numerous rising and falling grades which will require the driver to adjust the operational settings. Thus the results shown in the calculator, in particular for a long period of time, such as per hour, may not be reached if the locomotive is actually operating, for periods of time, at lower cutoff and throttle settings then those applied in the calculator default values.

This calculator is provided to allow approximations to be made between the locomotive's water usage in Open Rails, and the amount of usage that could be expected to be used based upon the design features of the locomotive. Probably the best way to compare usage, is to calculate at the amount of steam used per hour by the locomotive at the current operational settings, and then compare this to the value shown in the OR HUD.

It should also be noted that the amount of steam produced by the locomotive boiler and fire will be the ultimate limit to the performance of the locomotive, in other words the amount of steam consumed by the cylinders (and locomotive) cannot exceed the amount of steam produced by the boiler otherwise the boiler pressure will rapidly drop.


Imperial Units:
Cyl Dia (ins): Cyl Stroke (ins): No Cyls: Drive Wheel Dia (ins):
Speed (mph): Working Pressure (psi): Cutoff: Throttle (%):

Note: The calculator does not support pressure values over 300 psi.

Saturated
Superheated
      
Results
Wheel RPM:     Swept Volume per Rev (ft3): Steam Volume @ Pressure (ft3/lb):
Steam Consumption (lb/min): Steam Consumption (lb/hr):
Water Consumption (gals (uk)/min): Water Consumption (gals (uk)/hr):

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Metric Units:
Cyl Dia (mm): Cyl Stroke (mm): No Cyls: Drive Wheel Dia (m):
Speed (kph): Working Pressure (kPa): Cutoff: Throttle (%):

Note: The calculator does not support pressure values over 2068 kPa.

Saturated
Superheated
      
Results
Wheel RPM:     Swept Volume per Rev (m3): Steam Volume @ Pressure (m3/kg):
Steam Consumption (kg/min): Steam Consumption (kg/hr):
Water Consumption (litres/min): Water Consumption (litres/hr):

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Useful References

Locomotive handbook - American Locomotive Company (Alco)

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