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Aviation History
1951
1951 - 0248.PDF
V 154 FLIGHT, 8 February 1951 A B Bl B2 C = R-4360-C engine ^air-intake =atr-to-supercharfer =ai r-to-aftercool er •=exhaust tract to turbo- blower D -=aftereooler E ^compressed air to engine F = control valve G =exhaust-to-»tmotphere H =CH 9 turbo-supercharger Fig. 4. Diagram of air and gas flow-paths in R-4360C Wasp Major power-plant with CH 9 turbo-blower. Direct fuel injection is used, and there is no mechanical connection between engine and supercharger. TURBO-SUPERCHARGING . . . was put under the direction of Sanford Moss. The G.E. turbo was submitted for test in 1918 and so was inaugurated a continuous progress of development which extends to the present day and may well continue for some time to come. It is indisputable that this is in ne small measure due to the fact that, until 1937, when he retired, the work was con- tinously directed by Dr. Sanford Moss, but there is also little doubt that some advantage accrued as a result of the U.S. Army paying the entire costs of the development from 1919 until a few years ago. Whilst briefly reviewing the historical background of the exhaust turbo-blower, it is worth while to note that in Britain, a turbo-supercharger was designed during the 1914-18 war by James E. Ellor, of the Royal Aircraft Factory —later the ILA.E. Development with EUor's turbo-blower was carried forward energetically at the R.A.E. during the first half of the 1920s, but, for a variety of reasons, the focus of attention was shifted at about 1926-27 to mechanically driven superchargers, and the exhaust turbo-blower was shelved. James Ellor, undoubtedly the most brilliant mind in the supercharging field in this country, left the R.A.E. in 1927 and went to Rolls-Royce. To revert, however, to the G.E. turbo-blower, this has been developed to supersede the type BH 4 (Fig. 1) which, Fig. 5. Comparative chart showing gain in power and altitude per- formance given by the CH 9-supercharged engine relative to the standard R-4360 Wasp Major equipped with BH 4 turbo-blower. 4,500 ApOO 1D5O MORE B.H.R ^ 63OOH HIGHER 25OB.HJ? 3DOOft HIGHER 1. TAKE-OFF DRY RATING 2. NORMAL RATED POWER J. CRUISING POWER 1O 15 2O ALTITUDE(ftKiOOO) on the Pratt and Whitney Wasp Major, has a background of something approaching 200,000 hours of operation on Stratocruisers alone. In mechanical design, the new unit— the CH 9—is essentially similar to the BH 4, but engine modifications necessary for the new installation have resulted in the use of a new series number, and the engine is designated as the Wasp Major R-4360C. Test-bench work has shown that a take-off power increase of 32 per cent and a reduction in specific fuel consumption of 20 per cent is given by the new development by comparison with the R-4360 engine with BH 4 turbo-supercharger. On the basis of this per- formance, General Electric asserts that the new power-plant will enable a large transport (presumably such as the Strato- cruiser) to fly non-stop between New York and London and to carry 75 per cent more payload on other long flights as, for example, from Paris to Dakar, or from San Francisco to Honolulu. The new supercharger (Fig. 2) was designed for applica- tion to transport type aircraft for which take-off power requirements are limited to 5,OOO-7,OOOft altitude, and for which maximum cruising power is not used above 25,000ft. It is claimed, however, that in conjunction with booster turbos the new unit can be applied to military aircraft for operation at considerably greater altitudes. The most im- portant differences between the BH 4 installation (Fig. 3) and the new power-plant (Fig. 4) are the elimination of the intergral mechanically-driven supercharger and the carburet- tor in the former in favour of the direct fuel injection and no secondary (internal) supercharger in the latter. Normally the mechanically-driven supercharger, as used in the BH 4 installation, absorbs 500 h.p. from the crankshaft, and only a small part of the available exhaust energy is used because, at cruising conditions, the supercharger serves as a medium for fuel distribution to the cylinders, and the turbo-blower airflow is limited. By virtue of its use of direct fuel injec- tion, the CH 9 installation is able to employ a large part of the exhaust energy to provide full manifold pressure. Thus, most of the 500 h.p. which would be absorbed in driving a mechanically coupled supercharger remains in the crank- shaft and is therefore available for propelling the aircraft. The CH9 is somewhat larger than the BH4 in having a maximum diameter of about 28in, a maximum length of 26Jin, and a weight, with accessories, of 300 lb. It consists, essentially, of a single-stage centrifugal-flow compressor, driven by a single-stage axial-flow exhaust-gas turbine. The compressor and turbine arc mounted on the same shaft and are assembled, together with an oil pump and bearings, in relative positions in the casing so that their openings will align with the appropriate ducts and pipelines of the par- ticular power-plant installation. The basic units of an installation, as may be seen from Fig. 4, are the engine, the supercharger, and an external aftercooler. Air enters the ramming intake, and is intro- duced into the eye of die supercharger compressor; a por- tion of the entrained air is diverted across the aftercooler, whence it escapes to atmosphere. The main engine air is compressed in the supercharger to between 25 and 35 lb/sq in, and is then discharged through the aftercooler, which removes the heat of compression and, in fact, reduces the temperature of the air by more than 65 per cent. From the aftercooler the air enters the engine intake system at a temperature of less than 38 deg C. The increase in volu- metric efficiency thus gained is claimed to make possible a specific fuel consumption as low as 0.36 lb/bJi.p./hr. Simplification, enhanced reliability, and a reduction in maintenance is implicit in the absence of mechanical connec- tion between engine and supercharger. It is claimed that the CH9 can compress air at mass-flows up to 350 lb/min, and can provide aircraft cabin pressurization at altitudes up to 30,000ft. The chart shown in Fig. 5 indicates the all- round gain in power and altitude performance of the R-4360C engine equipped with the new" turbo-blower as compared with the BH4 turbo-blown R-4360 engine incor- porating the built-in mechanically driven supercharger. The CH 9 turbine has a mavimum continuous speed rating of 18,000 r.pjn., and exhaust gas entering the turbine installa- tion at a maximum continuous temperature of 955 deg C is discharged at a maximum continuous temperature of 233 degC *» .
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