Design and Development of Exhaust Valves From the Perspective of Modern Thinking: Part 3: Reverse Engineering of American and British Sodium-Cooled Valves

Abstract

Reverse engineering is a procedure normally used for producing close copies of engineering equipment made by an industrial competitor or in an enemy country. But it can be used by industrial historians to explain why components which were apparently doing similar jobs had a rather different configuration. In this case, the reasons behind the distinct differences between exhaust valves used in two American air-cooled radials, the Pratt and Whitney Double Wasp, the Curtis Wright Twin Cyclone and the Rolls-Royce liquid-cooled Merlin are explored. Comments are also made on the sleeve valve engines made by Bristol, intended to avoid the supposed problems of the hot poppet exhaust valve. Sodium cooling of the valves in all engines was needed because of the high rates of heat transfer. The American engines incorporated a hemispherical cylinder head incorporating two valves. Because of the size of valves, these had to be of the hollow head type. The Merlin engine, to minimise frontal area, opted for a pan shaped head, which forced the use of four valves per cylinder. Stem cooling in these valves was adequate.

Keywords:

• reverse engineering
• poppet valves
• sodium cooling
• Pratt & Whitney Double Wasp
• CW Cyclone
• RR Merlin
• sleeve valves,
• heat transfer

Acknowledgements

I would like to thank E. Marshall for his extremely helpful comments on combustion processes and for discussions on the pros and cons of the sleeve valve engine; Graham White for comments on the coking problems of valves; Kim McCutcheon for his extremely useful comments on sleeve valve manufacture and permission to use pictures from the Aircraft Engine History Society Website; D. Dulieu for forwarding early drafts of his book on stainless steel and for general encouragement; A. Grenside of G.S. Valves Ltd, Godalming, UK, for showing me how valves are fabricated in his factory

Notes

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2. F. Starr, ‘“The Key to Record Breaking-Exhaust Valve Cooling”: The Piston Engine Revolution (papers presented at the Conference on the History of Reciprocating Internal Combustion Engines, Manchester, UK, April 14–17, 2011), eds F. Starr, E. Marshall and B. Lawton, (London: Newcomen Society, 2011), pp. 509–37.

3. B. Price, ‘Developments of Aero-Engine in War 1915–1950: Impacts of Knowledge Management and Heuristics in the Configuration of Aero-Engine Architecture,’ in The Piston Engine Conference proceedings referenced immediately above, pp 401–420.

4. V. Kotelnikov and T. Butler, Early Russian Jet Engines – the Nene and Derwent in the Soviet Union, and the Origin of the VK-1 (Derby: Rolls-Royce Heritage Trust, 2003).

5. M. A. Carr, ‘Thermodynamic Analysis of a Newcomen Steam Engine,’ International Journal for the History of Engineering and Technology, 83 (2013), 187–208.

6. G. W. Gray, ‘Problems of Engine Cooling and High Speed Cowls,’ in Frontiers of Flight: The Story of NACA Research, (New York: Alfred A. Knopf, 1948), pp.113–17.

7. J. V. Becker, ‘High Speed Cowlings, Air Inlets and Outlets,’ in The High Speed Frontier: Case Histories of Four NACA Programs, 1920–1950, (Washington DC: National Aeronautics and Space Administration, Scientific and Technical Information Branch, 1980), pp. 139–65.

8. ^<https://en.wikipedia.org/wiki/Meredith_effect> [accessed September 2014].

9. ^<https://en.wikipedia.org/wiki/Pratt_&_Whitney_R-2800_Double_Wasp> [accessed September, 2014].

10. ^<https://en.wikipedia.org/wiki/Wright_R-2600> [accessed September, 2014].

11. A. Harvey-Bailey, The Merlin in Perspective – The Combat Years (Derby: Rolls-Royce Heritage Trust, 1985); A. Harvey-Bailey and D. Piggot, The Merlin 100 Series (Derby: Rolls-Royce Heritage Trust, 1993); A. S. C. Lumsden , ‘Rolls-Royce Merlin’ in British Piston Engines and Their Aircraft (Shrewsbury: Airlife, 1994) pp 201-16.

12. A. S. C. Lumsden ‘Bristol Hercules,’ in British Piston Aero-Engines and Their Aircraft, pp. 119–125.

13. S. D. Heron, History of the Aircraft Engine – A Brief History (Detroit MI: Ethyl Corporation, Research and Development Department, 1961), p. 27.

14. Anon, Handbook of Operation and Maintenance for Allison V-1710 F-Type Engine, 3^rd edn (Indianapolis IN: Allison Division, General Motors Corporation, April 1943).

15. A. Harvey-Bailey, The Merlin in Perspective – The Combat Years, (Derby: Rolls-Royce Heritage Trust, 1985), pp. 8–11.

16. R. Banks, ‘Ethyl,’ Aircraft Engineering, 25 January 1934.

17. A. T. Cowell, ‘Modern Aircraft Valves,’ SAE Transactions, 35 (1940), 147–165.

18. J. E. Morgan, ‘Aero-Engine Exhaust Valve Development,’ Proceedings of the Institution of Mechanical Engineers: Automobile Division, 9 (1955), 138–46.

19. A. T. Cowell, Figure 4 in ‘Modern Aircraft Valves,’ SAE Transactions, 35 (1940), 148.

20. F. Starr, ‘Design and Development of Exhaust Valves for the Internal Combustion Engine from the Perspective of Modern Thinking: Part 2 1930–90,’ International Journal for the History of Engineering and Technology, 84 (2014).

21. ‘The Selection of Material for Engine Valves,’ in Metals Handbook, (Cleveland OH: American Society for Metals, Cleveland, 1961), 626–34.

22. M. A. Zipkin and J. C. Sanders, Correlation of Exhaust Valve Temperatures with Operating Conditions in an Air Cooled Cylinder, Report No. 813 (Cleveland OH: Aircraft Engine Research Laboratory, NACA, October 1945); F. Starr, ‘The Key to Record Breaking-Exhaust Valve Cooling’, pp. 509-37).

23. Heat transfer rates when water is on the point of visibly boiling are extremely high. The latent heat in the formation of steam itself results in good rates of heat removal. In addition the formation of bubbles of steam increases turbulence, which is also critical increasing heat removal; J. H. Lienhard IV and J. H. Lienhard V., A Heat Transfer Textbook, (Cambridge MA: Phlogiston Press, 2008), p. 21, Table 1.1.

24. J. C. Sanders, H. D. Wilsted and B. A. Mulcahy, Operating Temperatures of a Sodium-Cooled Exhaust Valve as Measured by a Thermocouple, Report No.754 (Cleveland OH: Aircraft Engine Research Laboratory, NACA, December 1943).

25. Graham White (acknowledged expert on Pratt and Whitney and other American Radials), e-mail message to author, June 2014.

26. Bill Gunston, ‘Sleeve Valves,’ in Fedden: The Life of Sir Roy Fedden, (Derby: Rolls-Royce Heritage Trust, 1998), pp. 156–80.

27. C. F. Taylor ‘Aircraft Propulsion,’ Smithsonian Annals of Flight, (Washington DC: Smithsonian Institution Press, 1971), p. 41. This reference originated from a file at the Smithsonian on ‘Reminiscences of Heron’ by T. T. Neill and R. W. Young.

28. R. J. Raymond, Comparison of Sleeve and Poppet-Valve Aircraft Piston Engines (Aircraft Engine Historical Society, April 2005, www. enginehistory.org, accessed 28 January 2016); E. L. Marshall, ‘A Lifelong Love Affair – Sir Harry Ricardo and the Sleeve Valve Engine,’ International Journal for the History of Engineering and Technology, 83 (2013), 62–95.

29. E. L. Marshall (Newcomen Member with expertise in engine and fuel research): his work at Cambridge University was directed at speeding up the burn rate of lean mixtures by stretching the flame front using small-scale turbulence.

30. It might be thought that when a spark plug fires this is at a time when the piston has reached ‘top dead centre’, and when the air-petrol mixture is at maximum compression. But to allow time for the mixture to burn, the spark plug is fired before the piston reaches top dead centre. This time is given in terms of the angle that the crankshaft is at when the spark plug fires and is given as the number of ‘degrees of advance’. If the spark plug did fire at top dead centre it would be at, by definition, zero degrees of advance. In practice the amount of advance varies depending on the engine output and the fuel characteristics. It is usually between 5º and 35º of crank angle. The higher the advance the better, but low octane fuels cannot tolerate high values.

31. M. Munger, H. D. Wilsted and B. A. Mulcahy, The Effect of Valve Cooling Upon Maximum Permissible Engine Output as Limited by Knock, Report TN 861 (Washington DC: NACA, September 1942.)

32. R. A. Beaumont, Aeronautical Engineering – A Practical Guide to Everyone Connected with the Aircraft Industry (London: Odhams Press, ca. 1942), pp. 160–61.

33. Nevil Shute, No Highway, (London, Pan Books, 1969), p. 63.

34. Bill Gunston, ‘Centaurus,’ in Classic World War II Aircraft Cutaways, (London: Osprey, 1995), pp. 142–43.