Alan Arnold Griffith - Turbine Engines

Turbine Engines

In 1926 he published a seminal paper, An Aerodynamic Theory of Turbine Design. He demonstrated that the woeful performance of existing turbines was due to a flaw in their design which meant the blades were "flying stalled", and proposed a modern airfoil shape for the blades that would dramatically improve their performance. The paper went on to describe an engine using an axial compressor and two-stage turbine, the first stage driving the compressor, the second a power-take-off shaft that would be used to power a propeller. This early design was a forerunner of the turboprop engine. As a result of the paper, the Aeronautical Research Committee supported a small-scale experiment with a single-stage axial compressor and single-stage axial turbine. Work was completed in 1928 with a working testbed design, and from this a series of designs was built to test various concepts.

At about this time Frank Whittle wrote his thesis on turbine engines, using a centrifugal compressor and single-stage turbine, the leftover power in the exhaust being used to power the aircraft directly. Whittle sent his paper to the Air Ministry in 1930, who passed it on to Griffith for comment. After pointing out an error in Whittle's calculations, he stated that the large frontal size of the compressor would make it impractical for aircraft use, and that the exhaust itself would provide little thrust. The Air Ministry replied to Whittle saying they were not interested in the design. Whittle was crestfallen, but was convinced by friends in the RAF to pursue the idea anyway. Luckily for all involved, Whittle patented his design in 1930 and was able to start Power Jets in 1935 to develop it.

Griffith went on to become the principal scientific officer in charge of the new Air Ministry Laboratory in South Kensington. There he invented the contraflow gas turbine, which used two sets of compressor disks rotating in opposite directions, one "inside" the other. This is as opposed to the more normal design in which the compressors blow the air against a stator, essentially a non-moving compressor disk. The effect on compression efficiency was noticeable, but so was the effect on complexity of the engine. In 1931 he returned to the RAE to take charge of engine research, but it was not until 1938, when he became head of the Engine Department, that work on developing an axial-flow engine actually started. Joined by Hayne Constant, they started work on Griffith's original non-contraflow design, working with steam turbine manufacturer Metropolitan-Vickers (Metrovick).

After a short period Whittle's work at Power Jets started to make major progress and Griffith was forced to re-evaluate his stance on using the jet directly for propulsion. A quick redesign in early 1940 resulted in the Metrovick F.2, which ran for the first time later that year. The F.2 was ready for flight tests in 1943 with a thrust of 2,150 lbf, and flew as replacement engines on a Gloster Meteor, the F.2/40 in November. The smaller engine resulted in a design that looked considerably more like the Me 262, and had improved performance. Nevertheless the engine was considered too complex, and not put into production.

Griffith's original rejection of Whittle's concepts has long been commented on. It certainly set back development of the jet engine in England. His motivations have long been the topic of curiosity, with many people suggesting that his endless quest for perfectionism was the main reason he didn't like Whittle's "ugly" little engine, or perhaps the belief that "his" design was innately superior.

Griffith joined Rolls-Royce in 1939, working there until 1960. He designed the AJ.65 axial turbojet which led to the development of the Avon engine, the company's first production axial turbojet. He then turned to the turbofan (known as "bypass" in England) design and was instrumental in introducing the Rolls-Royce Conway. Griffith carried out pioneering research into vertical take-off and landing (VTOL) technology, culminating in the development of the Rolls-Royce Thrust Measuring Rig.