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From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Letter from Vauxhall Motors Ltd discussing aviation engine combustion analysis and flame front control.

Identifier  ExFiles\Box 127\4\  scan0094
Date  25th February 1938
  
1097
Vauxhall Motors Ltd
CONTRACTORS TO THE ADMIRALTY, WAR OFFICE & AIR MINISTRY.
LUTON. BEDS.
TELEPHONE NUMBER 2600 LUTON.
TELEGRAMS CARVAUX, TELEX, LUTON

WHEN REPLYING PLEASE QUOTE
→ OUR REF: AT/SFE
YOUR REF:

25th. February 1938

W.A.Robotham Esq.,
Messrs Rolls Royce Ltd.
DERBY.

Dear Robotham,

I thought you might be interested in the following. -

During a visit by Dr. Ker Wilson of De Havilland we discussed my own pet notion that aviation engines were being subjected to considerable more punishment than necessary, due to the lack of flame front control.

The result of this conversation was that De Havilland permitted us to make a plaster cast of the combustion chamber of two engines.

As expected they show rather badly yet with a simple change we - in plaster - converted the very bad to very good. I am enclosing two flame front control charts of one of the above engines - a before and after picture. "A" is as received and shows a bad spot wherein the maximum flame front area comes late enough to be involved with 65% of the volume.

This type of analysis may be resolved roughly into kinetics - assuming the ratio of volume increase to travel increase, as the velocity - volume as in lower curve - is weight or force. The time may be roughly assumed as 40° of crank travel - top dead centre approximating the fifty percent point.

On this basis compare curve A and B and you see what a tremendous difference you get. The peak is 170 - the volume involved is 25% and all this is not happening at top dead centre. (The rigid zone). The
  
  


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