Mechanical Engineering

I.C engine 200 MCQ-ssc-upsc- mechanical engineering :- Part - 1 1.Indicated power of four stroke engine is equal to -     A. pLAN                        B. 2pLAN     C. pLAN/2.                    D. 4pLAN ANS - C 2.Compression ratio of I.C. engine is- A. the ratio of volumes of air in cylinder before compression & after compression stroke. B.volume displaced by piston per stroke & clearence volume in cylinder. C.swept volume/cylinder volume D.cylinder volume/swept volume ANS- A 3.Scavenging air of diesel cycle means- A.air used for combustion. B.forced air for cooling cylinder. C.air used for forcing burnt gases out of engine's during the exhaust period. D.air fuel mixture. ANS- C 4.The working cycle un case of four stroke engine is completed in following number of revolutions of crankshaft-     A. 1/2                                  B. 1     C. 2                                     D. 8 ANS - C 5.An engine indicator is used to determine the

                              I.C ENGINE Difference of petrol and diesel engine :- 1.Petrol engine run on otto cycle and diesel engine run on diesel cycle. 2.Air fuel mixture suction Stroke in petrol engine.In diesel engine only air sucks in suction stroke. 3.In petrol engine,spark plug is needed.In diesel engine,no spark plug is needed. 4.In petrol engine,compression ratio 6-12. In diesel engine,compression ratio 14-22. 5.In petrol engine,high efficiency. In diesel engine low efficiency. 6.In petrol engine,less vibration & noise. In diesel engine,more vibration & noise. 7.Petrol engine light weight engine. Diesel engine heavy weight engine. 8.Petrol engine generaly use motor cycle,car,light weight vehicles. Diesel engine generaly use truck,bus etc.    GOVERNINNG OF I.C ENGINES : Various methods are : a. Heat and miss governing — used for small engine,No fuel admited during the cycle by keeping suction valve closed. b. Quantitative governing — Quantity of c

                          I.C ENGINE Dual cycle : It is also called as limited pressure cycle or it also called as mixed cycle. →In this process heat addition process takes place both at constant volume & constant pressure. → This cycle is used for heavy duty diesel engine. The process which takes place in dual cycle are - A. Process (1-2) : Reversible adiabetic(isentropic)compression. B. Process(2-3) : Constant volume heat addition. C. Process(3-4) : Constant pressure heat addition. D. Process(4-5) : Reversible adiabetic(isentropic) expansion. E. Process(5-1) : Constant volume heat rejection. At bellow pV diagram and T-S diagram 1.At point 1, Air enters the cylinder or air is completely filled in the cylinder. 2. Process(1-2) : Compression of air takes place & it is reversible adiabetic compression. 3. During compression process,there is decrease in volume with corresponding in pressure keeping the entropy constant. 4. At the point 2,heat addition( fuel

                                I.C ENGINE Diesel cycle : It is a theoritical cycle used for compression ingnition or diesel engine. → In this cycle,the heat addition process takes place at constant pressure. → Hence,this cycle is also caled as 'constant pressure process' The following process takes places in diesel cycle - 1. Process (1 - 2) = Reversible adiabetic(isentropic)compression. 2. Process (2 - 3) = constant pressure heat addition. 3. Process (3 - 4) = Reversible adiabetic(isentropic)expansion. 4. Process (4 - 1) = Constant volume heat rejection. PV-diagram of diesel cycle :-           T-S diagram :-                       1. In point 1,only air is taken into the cylinder or engine. 2. Process(1 -2) After air has entered the engine,it is compress isentropically [S 1 - S 2 ]. → During the compression process volume of air decrease but there is an increase pressure & temperature of the air. 3. The fuel ignition start,fuel is added at con

                             I.C ENGINE HERE WE KNOW ABOUT CARNOT CYCLE, we already discuss in thermodynamics cheptra history behind carnnot cycle and details about this plz check the link : https://engineerapk.blogspot.in/2017/11/history-behind-carnot-cycle-details-of.html?m=1 OTTO CYCLE : Basic of otto cycle ;  * This cycle was introduced by german scientists Dr. A.N. Otto. * It is successfully aplied on petrol engine. * It consist two reversible adiabetic process & two constant volume process. * This is six event cycle -                 A. Suction                 B. Compression                 C. Combustion                 D. Expansion                 E. Blow by(heat rejected)                 F. Exahust Theory of otto cycle Process (0 - 1) suction of the air fuel mixture in cycle. Process (1 - 2) adiabetic compression. Process (2 - 3) compress volume of heat addition. Process (3 - 4) adiabetic expansion. Process (4 - 1) constant volume heat reject

                          I.C ENGINE Engine perform parameter,                                         Parameters are used to measure performance of an engine:            (1) Power  (2) Efficiency (3) Fuel consumption 1.power : (a) Indicated power (IP)                  (b) Brake power (BP)                  (c) Frictional power (FP) 2.Efficiency( η) : (a) Indicated tharmal efficiency (b) Brake tharmal efficiency (c) Mechanical efficiency (d) Relative efficiency (e) Volumetric efficiency 3.Fuel consumption : (a) Indicated specific fuel (b) brake specific fuel             In suction stroke; piston moves T.D.C to B.D.C.  Crank moves (A to B) in rotary motion.  Connecting rod moves reciprocating motion. In comparison stroke ; Piston moves B.D.C to T.D.C. Connecting rod moves (B to A) Combustion: also known as power or ignition This is the start of the second revolution of the four stroke cycle. At this point the crankshaft has completed a full 360 degr