World War Engineers and Scientists (part three)
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Sir Frank Whittle
There are many dubious postings on the subject of Sir Frank Whittle’s part in the invention and design of the jet engine but I would certainly like to set the record straight with regards to this. Sir Frank Whittle did indeed invent this form of propulsion and did indeed patent the turbojet before Hans van Ohain, the German jet aircraft pioneer co-accredited to this engine design. Ohain was certainly the first to have a turbojet fitted to an aircraft and make it flyable albeit initially rather unreliably. (Heinkel HE-178)Ohain however was an independent thinker and did develop a jet propulsion unit which ran from an electric motor and compressor. For this I sincerely feel, in my own opinion that he should be known as the co-inventor of the jet engine but not the turbojet – this honour should go to Sir Frank. Sir Frank should have been a few years ahead of Ohain but for the stubbornness of the British Air Ministry (read lack of vision) which would definitely have had a jet-powered aircraft in the skies before the Germans. In actual fact history tells us that most of Sir Frank’s efforts were sponsored by himself, two colleagues and British Thomson-Houston.
Years ago I was told by a merchant naval chief engineer that the reason why he liked the steam turbine propulsion unit so much better than the two stroke diesel units was all in the stupid waste of energy when making something go up and down to make something go round and round. He may indeed have read Sir Frank’s own mind – because this was one of the many reasons why a turbojet is superior in most ways to a petrol/gasoline powered reciprocating engine – a piston goes up and down which turns a propeller. Turbojet theory is not all that difficult to understand but the theory quickly becomes a nightmare when one gets into the complexities of design. Whittle had a great idea. Putting pen to paper was the best part, putting thoughts into a practical working unit nearly lead to early demise through frustration and nervous breakdowns. Ohain had the luxury of an excellent cash injection through the German defence initiatives. Modern jet aircraft use engines costing millions of dollars each with good reason. In the 1930s aircraft engines were all piston types, huge mammoths developing upwards of a thousand horsepower. Sir Frank initially entertained the thought of using the motorjet principle but the impractical weight constraint (in comparisons with standard propeller driven aircraft) led to the idea of using turbocharger technology i.e. exhaust gasses to feed a turbine/ compressor seemed like a very much more likely solution. And with Sir Frank’s engineering and scientific mind simpleness was indeed a solution but did he have the support of the government?
The Motorjet Principle.
The concept of a thermal engine was not new in the 1930s. Fuel was injected into a combustion chamber which had a force fed air supply from a compressor driven by a piston engine. The fuel was ignited which in turn resulted in a very high pressure inside this combustion chamber – in turn escaping through the exhaust resulting in thrust to move the vehicle or craft forward. Russian aircraft using this propulsion often used an air screw or propeller as well to increase the thrust. Whittle however cleverly calculated that there were no proven merits to using this system at the time – his concept was to use the exhaust gasses of a burning fuel air mixture to spin a turbine which in turn drove the compressor , the idea stemming from turbo charger technology.
The Turbojet.
Using supercharger compressor blade design at the time, Sir Frank modified the design and shape to become more efficient – this efficiency adding weight to his theories about jet propulsion. The air ministry in 1929 saw no merit to what they thought was a too simple, impractical form of propulsion and declined to consider any further thought to the matter. This lead to Whittle successfully filing patent on his design in 1930 which drew immense interest from Germany. Of course the air ministry, with absolutely no interest in promoting the turbo jet idea allowed the idea to become public knowledge which allowed Whittle to retain the rights to the engine. In 1935 the patent was allowed to lapse due to the indifference of the Air Ministry and Whittle’s lack of funds to renew. Whittle subsequently, with the assistance of two colleagues, two investment bankers and steam turbine specialists Thomson-Houston manufactured their first successful but dangerously uncontrollable turbojet in April 1937. In 1938 the W.U. fell under the Official Secrets Act of the time and put under government control which hampered Whittle’s efforts due to lack of public funding.
In mid-1939 the Director of Scientific Research made a visit to Whittle’s premises at Thomson-Houston and was totally convinced of the superior performance of the W.U. which resulted in immediate changes to their strategy which resulted in the necessary funding and manufacture of more Whittle Units.
In 1941 the first jet powered aircraft (Gloster-Whittle E28/39) took to the skies, built by the Gloster Aircraft Company.
Sadly, the Germans had won this race – for the most part caused by the lack of vision of the British Air Ministry.
Jet Engine Design.
The first of Whittle’s engines had control problems relating to the combustion process. It was caused by unburnt diesel (the fuel used at this stage) pooling in the combustion chamber of the U-1, Whittle’s first unit. The design eventually lead to an atomised fuel burner ten combustion chamber unit (the Whittle Unit), the combustion chambers all assembled externally from the compressor and turbine. The first successfully flown aircraft, the Gloster-Whittle, only had an 860lb thrust engine but could attain a speed of nearly 350 m.p.h. Engine thrust was too low to power fighter aircraft. Twin engine aircraft design became of interest.
The centrifugal design was chosen over the axial design although the axial design proved later to be superior. The reason for the original choice was put down to the engineers at the time having had much more experience with the centrifugal type compressor used in aero superchargers and turbochargers.
I’d appreciate any comments on this article – I’d really love the article to be an experience for any cadet, student or otherwise.
- For some details on how the Brayton Cycle works see HERE. (This is a very good Wiki article – I certainly hope that you get Wiki’s wheel turning by making your donation).
- Please read A PERSONAL REMINISCENCE, http://www.frankwhittle.co.uk/index.php. Truly a superb man.
Go back to Part Two or Part One
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