Browsing by Author "Pant, Rajkumar S."
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Item Open Access GENENG : A generic turboprop engine model(1995) Pant, Rajkumar S.This report describes GENENG, a code developed t o model the performance of a generic turboprop engine. Using published data from various sources, a database of 7 turboprop engines suitable for General Aviation, Commuter & Regional transport aircraft was developed. This database consists of the values of the SHP available, Fuelflow, and Jet Thrust produced by the engines at specific altitudes between sea-level and 35000 ft and forward speeds between 0 and 350 knots (TAS), at max. take-off, max. Climb & max. Cruise ratings. GENENG can then be used to obtain realistic estimates of any of these three parameters for a generic engine that lies within this database at any operating condition, i.e. altitude, forward speed, and engine rating. The user has to specify the ball-parking criterion, i.e. the desired value of any one of the three parameters at a specific operating condition. The generic engine is then positioned in the database, by identifying the nearest two engines at the ball-parking criterion. The fractional ratio of the location of the generic engine from these two engines is then calculated. Assuming that the same fractional ratio would also apply at all the other data points, the values of all the parameters at all engine ratings are then generated at specific combinations of forward speed and altitude. Using Bicubic Spline interpolation routines, the value of any of the three parameters at any forward velocity and altitude can then be obtained.Item Open Access Generalised cost optimisation of short-haul twin-turboprop aircraft including airport considerations(Cranfield University, 1997-02) Pant, Rajkumar S.; Fielding, JohnIn this thesis, a methodology is proposed for the conceptual design and optimisation of twin-turboprop Commuter & Regional aircraft suitable for operation over a spe¬cific short-haul route. Using this methodology, the optimum configuration and flight profiles of such aircraft for operation over various stage-lengths can be obtained. By significantly modifying an existing computer code for synthesis and trajectory opti¬misation of Commuter aircraft (CASTOR), a new code (CRAGER) has been developed to estimate the Generalised cost of travel incurred by a passenger for air-travel be¬tween two cities. A new sub-module has been developed for the geometric sizing of a suitable airport as per ICAO/FAA recommendations, and estimation of the Airport cost, i.e. the cost associated with setting-up and operating this airport at one of the two cities. This module is incorporated into CRAGER. Generalised cost is assumed to consist of the Access cost, Flight cost, Time cost and the Airport cost, and is proposed as a new objective function to be minimised. In an exploratory case study, the efficacy of two stochastic optimisation methods viz. Genetic Algorithms (GA) and Simulated Annealing (SA) was demonstrated for handling complicated objective functions related to aircraft conceptual design. In particular, the SIMANN SA code was found to be quite robust and easy to imple¬ment, and came up with better solutions compared to conventional gradient based optimisers for multi-modal objective functions. As an example of the application of the proposed methodology, several case studies were carried out for business travel in India, using both CASTOR & CRAGER. Based on a survey of existing regional airports in India, the airports were classified under three levels, enabling estimation of Airport cost associated with operating a specific aircraft. A model was developed for predicting the demand for business travel in India between a metropolitan city (hub) and another city located near-by (spoke). The case studies revealed the non-linear nature of the airport sub-module, due to the airport classification system followed by ICAO & FAA. It was seen that when the annual travel demand is low, the Generalised cost is dominated by the Airport cost and the Time cost. With increase in annual travel demand, however, the Flight costs dominate the Generalised cost, hence larger aircraft have lower Generalised costs. High-capacity aircraft were seen to have a low Flight cost, but this advantage was more than overcome by the excessively high Airport and Time costs associated with them. Compared to pressurised aircraft, the un-pressurised commuter aircraft suffer from severe penalties due to limitations imposed on their cruising altitude and descent profile. Finally, the optimum 50 seater aircraft obtained by CRAGER had better or marginally lower DOC and Generalised cost compared to existing aircraft.