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 Question: What physical phenomena causes slip in centrifugal compressors?? By: Ahilan A     Date: 2012-06-26 Answer: In an actual compressor, towards the exit of the impeller, the Coriolis pressure gradient disappears. This leads to a difference in the relative whirl/tangential velocity and the blade speed. This causes the relative whirl/tangential velocity to lag behind the blade speed resulting in slip. By: Prof. A M Pradeep     Date: 2012-06-29

 Question: how sfc of different engines varies with altitude? By: Brijesh Kumar     Date: 2012-07-31 Answer: Brijesh: please refer to Chapter 5 of book Mechanics and Thermodynamics of Propulsion by Hill and Peterson. Detailed description of variation of SFC of different types of engines with altitude is given there. By: Prof. A M Pradeep     Date: 2012-08-10

 Question: sir in lecture 6 in ideal brayton cycle efficiency isentropic relation b/w pressure and temperature is nt correct By: tulsiram sahu     Date: 2012-08-04 Answer: Thanks for pointing out the error. This slide was supposed to have been replaced by the editors. Will ask them to do so as soon as possible. By: Prof. A M Pradeep     Date: 2012-08-10

 Question: lecture no. 17 problem no. 1 formula used for finding degree of reaction is wrong By: tulsiram sahu     Date: 2012-08-11 Answer: Thanks for pointing out the error. The correct formula is Rx=Ca/2U x {tan(beta1)+tan(beta2)} By: Prof. A M Pradeep     Date: 2012-08-23

 Question: degree of reaction= 1/2-Ca/2U(tan(alfa1)-tan(beta2)) is given in slide no 14 ....i am not getting this derivation sir can u help me? By: tulsiram sahu     Date: 2012-08-11 Answer: Please refer to any of the books, say by Dixon or by Hill and Peterson for a detailed derivation. By: Prof. A M Pradeep     Date: 2012-08-23

 Question: sir in case of ram jet....how can be ..T0a/Ta=T07/Te???....if it be dan Ta=T7...is it possible?...in lect 38 its given like dat By: tulsiram sahu     Date: 2012-08-14 Answer: It is the ratio that is equal and not the temperatures. The ratios are assumed to be equal for a fully expanded nozzle. Therefore the pressure ratios and the Mach numbers come out to be equal too. The individual temperatures are not assumed to be equal. By: Prof. A M Pradeep     Date: 2012-08-23

 Question: How much distance spacecraft goes in a spiral path while escaping from earth surface? By: mani     Date: 2012-08-26 Answer: There is no fixed distance that must be attained for escaping the earth's gravitational. A powered spececraft can straigtaway be propelled out of earth's orbit. Most of the times for controlled mission they are made to orbit a few times before going out for space missions. A loose way to put it is wherever it attains escape speed it goes out of earth's gravity field. By: Prof. Bhaskar Roy     Date: 2012-09-12

 Question: sir can you please explain chocked nozzle, and how does it help gaining thrust By: thomas     Date: 2012-09-06 Answer: Choked nozzle refers to a state of operation on the nozzle wherein the nozzle has accommodated or passes the maximum possible mass flow under the given conditions of pressure ratio, and area ratio. In this condition, the Mach number at the throat of the nozzle becomes unity. For a supersonic nozzle, the nozzle has to be choked at the throat to achieve supersonic flow in the diverging portion of the nozzle. Aero engines operate under choked condition most of the time ensuring best possible performance of the engine under various operating conditions. By: Prof. A M Pradeep     Date: 2012-09-08

 Question: An aircraft engine is provided with thrust reversal facility. While taxiing down the runway at 150 kmph the engine sucks in air at 50 kg/s with a jet velocity of 150m/s.How to calculate the thrust vector if the exhaust of the same mass flow is deflected by 90 degrees ? By: Santhosh     Date: 2012-10-13 Answer: I can only give you a hint for this question: the thrust equation is derived in such a way that thrust is always along the axis of motion. Therefore, if the exhaust is deflected, there would not be any thrust due to this exhaust. However what about the flight speed? By: Prof. A M Pradeep     Date: 2012-10-19

 Question: what will happen to properties of flow in subsonic nozzle if the flow is entering at mach number 1? By: ravi ranjan     Date: 2012-10-16 Answer: A supersonic flow cannot be obtained in a converging nozzle. So, if the flow entering the nozzle itself if sonic or supersonic, there would a normal shock/bow shock upstream or at the nozzle lip (depending upon the nozzle angle and Mach number). Downstream of this shock, the flow would be subsonic and then would accelerate in the converging nozzle. By: Prof. A M Pradeep     Date: 2012-10-19

 Question: what is effect on efficiency and pressure ratio of axial flow compressor if stator is designed such that it is also rotating with rotor? By: dinesh     Date: 2012-10-22 Answer: A stator by its name is a stationary set of blades. It is aerodynamically matched to the rotor only when it is stationary. If it is made to rotate (somehow) it will be automatically unmatched with the rotor and the efficiency and pressure ratio will fall drastically. By: Prof. Bhaskar Roy     Date: 2012-10-29

 Question: sir there is a typographical error in lecture 10, diffuser efficiency equation and in burner efficiency equation. By: phaneendra     Date: 2012-10-23 Answer: Please let me know the corresponding slide numbers. Thanks. By: Prof. A M Pradeep     Date: 2012-10-30

 Question: sir as in L17- axial flow compressor tutorial, number of stages is find out with overall temperature rise to per stage temp. rise, can be get number of stages with overall pressure rise to per stage pressure rise. By: vishal agrawal     Date: 2012-11-04 Answer: You could also use the per stage pressure rise to determine the number of stages. Here again the assumption of equal pressure rise per stage will be implied. By: Prof. A M Pradeep     Date: 2012-12-07

 Question: why we do not evaluate Degree of Reaction in case of centrifugal compressor..? sir would u plz explain it, while we have there impeller as a rotor and diffuser as a stator. By: vishal agrawal     Date: 2012-11-04 Answer: Degree of reaction is a two dimensional estimate of share of diffusion between rotor and stator. In a centrifugal compressor the rotor is a highly 3-D machine - there is no scope for such 2-D concepts to be utilized. By: Prof. Bhaskar Roy     Date: 2012-12-18

 Question: What is the classification of propulsion?list out AIR BREATHING engines and NON AIR BREATHING ENGINES? By: Ashok kumar     Date: 2012-11-16 Answer: Air-breathing engines are those that use air from the atmosphere for combustion. All jet engines, petrol and diesel engines etc are air-breathing engines. Non-airbreathing engines on the other hand carry an oxidiser (not necessarily oxygen) for combustion. Rocket engines are examples of these type of engines. By: Prof. A M Pradeep     Date: 2012-12-07

 Question: IF 12% ethanol is added in petrol is it gives good combustion and at what percentage of efficiency it will give?IS it help to save fuel? please give explanation sir? By: Ashok kumar     Date: 2012-11-16 Answer: Addition of alcohol to petrol is being practiced in many countries. Though the overall efficiency may not change significantly, it does help reduce to consumption of fossil fuels. By: Prof. A M Pradeep     Date: 2012-12-07

 Question: what is combustion intensity By: prakash     Date: 2013-03-28 The co-ordinator will post his answer
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