Reply To: Kylchap Exhaust Systems

[Martin Johnson]

Hi Chris,
Have been out of circulation for a while, and then locked myself out of my account one here!

Anyway, to pick up on your recent posts:
Koopmans says “It is conceivable that a properly designed petticoat could act as a sequential ejector.” – Is that not a Kylchap, which we were discussing right at the top of this thread?

I’m thinking that the design of the Kylchap, with the various cowls and mixing areas would have maximised the effective surface area of the steam jet, and therefore minimised the “lost” KE of the perpendicular moment of flow. – Maybe. I come at it from the ESDU graph, which shows that as the steam / gas mass ratio moves lower, the area ratio increases and the peak efficiency will increase – which seems to be the question you are posing. Whether or not the efficiency increase is due to the mechanism you postulate I can’t say for sure, but it looks reasonable.

Further to the above post, I came across some data for a Class 6 locomotive, and at the maximum boiler output this quantity would be of the order of 50kW. – Yes, quite a lot of power and when you factor in the jet pump efficiency, thats at least 150 kw off the DBHP!

If you take the pulsing effects into account it could easily be double this value. I think that is a very valid point. The “oft quoted received knowledge” is that the pulsation does not have a measurable effect. However, I think that is mis-leading. The pulsations affect the nozzle peak Mach number, the kinetic energy loss, the porosity of the firebed, and IMHO the tendency of the fire to lift, the loss of unburnt fuel.

Martin