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PERFORMANCE EVALUATION OF CONVENTIONAL TURBOPROP ENGINES

KrishiKosh

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Title PERFORMANCE EVALUATION OF CONVENTIONAL TURBOPROP ENGINES
 
Creator Ranjan, Rajiv
 
Contributor TARIQ, MOHAMMAD
 
Subject null
 
Description PERFORMANCE EVALUATION OF CONVENTIONAL TURBOPROP ENGINES
Aircraft gas turbine cycles differ from shaft power cycles in that the useful power output is in the form of thrust. The whole of the thrust of the turbojet and turbofan is generated in propelling nozzles whereas with the turboprop, most of the thrust is produced by a propeller with only a small contribution from the exhaust nozzle. A second distinguishing feature is the need to consider the effect of forward speed of flight and altitude on the performance. It was the beneficial aspect of these parameters, together with a vastly superior power/weight ratio that enabled the gas turbine to so rapidly supplant the reciprocating engine for aircraft propulsion except for aircraft propulsion and low powered lighter aircraft.The designer of aircraft engines recognized the various requirements for take-off, climb, cruise and manoeuvring, the relative importance of these being different for civil and military applications and for long and short haul aircraft. In the early days, it was common practice to focus on the take-off thrust, but this is no longer acceptable. Engines for long range civil aircraft, for example, require low SFC at cruise speed and altitude, while the thrust level may be determined either by take-off thrust on the hottest day likely to be encountered or by the thrust required at top of climb. Evidently the selection of design condition is much more complex than for a land- based unit. As examples, ‘design point’ calculations will be shown for take-off (static) and cruise condition.
In turboprop engines a conventional aircraft propeller is usually mounted in front of the jet engine and in one type of engine is driven by a second or free turbine. This is located behind the turbine that is driving the compressor. In other designs the power is obtained by additional stages on the main turbine.Since turbine speeds are much higher than propeller speed, a reduction gear is required between the turbine and the propeller. About 90 percent of the energy in the hot gases is absorbed in the turbine, and only about 10 percent remains to increase the speed of the exhaust jet. Accordingly, only a very small portion of the overall thrust is produced by the jet; most of it comes from the propeller. Turboprops are usually rated on the basis of equivalent power at take-off conditions and the specific fuel consumption and specific power are often expressed in terms of that equivalent power. It is nevertheless desirable to quote both the shaft power and jet thrust available.
 
Date 2017-11-10T04:31:57Z
2017-11-10T04:31:57Z
2017
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/5810035269
 
Language en
 
Format application/pdf
 
Publisher Department of Mechanical Engineering Shepherd Institute of Engineering & TechnologySAM HIGGINBOTTOM UNIVERSITY OF AGRICULTURE, TECHNOLOGY & SCIENCES ALLAHABAD, UTTAR PRADESH