Aero engines

Now a second example, taking us from low technology to the advanced materials design involved in the turbofan aero-engines which power large planes. Air is propelled... 

These requirements severely limit our choice of creep-resistant materials. For example, ceramics, with their high softening temperatures and low densities, are ruled out for aero-engines because they are far too brittle (they are under evaluation for use in land-based turbines, where the risks and consequences of sudden failure are less severe - see below). Cermets offer no great advantage because their metallic matrices soften at much too low a temperature. The materials which best fill present needs are the nickel-based super-alloys. 

Slides Turbofan aero-engine super-alloy turbine blades, showing cooling ports [3] super-alloy microstructures [4] DS eutectic microstructures [3, 5] ceramic turbine blades. 

Nickel and its alloys form another important class of non-ferrous metals (Table 1.3). The superb creep resistance of the nickel-based superalloys is a key factor in designing the modern gas-turbine aero-engine. But nickel alloys even appear in a model steam engine. The flat plates in the firebox must be stayed together to resist the internal steam pressure (see Fig. 1.3). Some model-builders make these stays from pieces of monel rod because it is much stronger than copper, takes threads much better and is very corrosion resistant. 

A third set of similar but simpler calculations were described by MacArthur [12] who applied aero-engine cooling technology to obtain improved performance of industrial type gas turbine power plants. 

Mac Arthur. C. D, (1999). Advanced aero-engine turbine technologies and their application to industrial gas turbines, ISABE Paper No. 99-71.31. 14th International Symposium on Air-Breathing Engines, Florence. Italy, 1999,... 

Horlock, J.H. (1997), Aero-engine derivative gas turbines for power generation thermodynamic and economic perspectives, ASME Journal of Engineering for Gas Turbines and Power 119(1), 119-123,... 

The performance characteristics of a lubricating oil depend on its origin and on the refining processes employed, and in order to ensure consistent properties these are varied as little as possible. Some aero-engine builders insist on a complete re-evaluation of a lubricant, costing many thousands of pounds, whenever there is a change of source (crude) or refining process. 

Several coating techniques are now available to overcome the oxidation problems with molybdenum above 300°C. One of these, based on molybdenum disilicide, is finding increased usage in flame breakout shields for aero-engines where tests have shown (unpublished work) that the coated material can withstand a high pressure torching type flame attack at temperatures in excess of 2(X)0°C. 

Despite the fact that thermo-acoustic instabilihes have been studied for more than a century, their control and elimination in practical combustion devices is still a problem that is difficult to master, particularly in devices with a high energy density such as aero-engines and rocket propulsion systems [24-28]. 

Yttrium is also used in other areas of metallurgy notably as a component of certain nickel-base and cobalt-base superalloys of the NiCrAlY and CoCrAlY type.(3) These alloys possess excellent corrosion and oxidation resistance, properties that have attracted the attention of the aero-engine industry where they are used as protective coatings on turbine blades. The alloys, when applied by vapour deposition, form an oxide coating that exhibits remarkable adhesion, a property attributed largely to the yttrium component acting to prevent the formation of voids at the oxide/substrate interface.(4)... 

Emission of nanoparticles in the atmosphere from anthropogenic sonrces (machines, aero engines, power stations, smelters, plasma, welding and heat treatment processes) has been continnonsly inaeasing ever since the beginning of the indnstrial revolntion. 

Hutchison (Ref 5a) discusses in detail the use of EtN in liq rocket propints. The use of EtN is not recommended as a means of operating aero engine starters, or for any other operations where the unit is to be repeatedly used in close proximity to human life... 

The 1957 Defence White Paper made clear that there would be fewer research and development projects and production orders for military aircraft in future. In July 1957 a backgroimd paper was circulated to the Cabinet listing a number of well-known aircraft firms where workers were likely to be made redundant as a result. It was expected that over the next four or five years the numbers employed in the manufacture of airframes, aero-engines and related equipment, excluding electrical equipment, would fall by about 100,000 to about 150,000, or what had been the level before the Korean War. ° The programmes for guided... 

Data, Naval Air Material Center, Aero. Engine Lab., Philadelphia, Pa., Rept. No. AEL-1157 (November 1950). 

Ohnabe, H., Masaki, S., Onozuka, M., Miyahara, K., Sasa, T. (1999), Potential application of ceramic matrix composites to aero-engine components , Composites, 30A, 489-496. 

Uneven development of sub-systems resulting in contradictions, e.g. powerful aero-engines developed faster than the wing design. 

Zeman, A., Becker, V., and Peper, K. 1993. Deposit Formation in Aero Engines Investigation by Pressure Differential Scanning Calorimetry (PDSC). Thermochim. Acta, 219, 305-313. 

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