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1-2 Reversible adiabatic (isentropic) compression.2-3 Constant pressure heating heat input to cycle via combustion and mechanical power delivered by thecycle.3-4 reversible adiabatic (isentropic) expansion mechanical power deliveredby the cycle.4-1 Constant volume cooling heat lost from cycle when the exhaust valve opens.

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1dC:\Users\Martin\AppData\Local\Microsoft\Windows\Temporary Internet Files\Content.Word\scan0020.jpg1eC:\Users\Martin\AppData\Local\Microsoft\Windows\Temporary Internet Files\Content.Word\scan0020.jpg2 (i)C:\Users\Martin\AppData\Local\Microsoft\Windows\Temporary Internet Files\Content.Word\scan0021.jpg1 to 2 - Ainiscompressed reversibly and adiabatically. Work is put in but no heat transfer occurs. Isentropic compression (no entropy change)C:\Users\Martin\AppData\Local\Microsoft\Windows\Temporary Internet Files\Content.Word\scan0021.jpg2 to 3 - The air is heat at constant volume no work is done, Head is addedair expands at constant pressure to V3.isochoric expansion no volume change.C:\Users\Martin\AppData\Local\Microsoft\Windows\Temporary Internet Files\Content.Word\scan0021.jpg3 to 4 - The air expands reversibly and adiabtically with no heat transfer back to its original volume. Work output is obtained isentropic expansion.C:\Users\Martin\AppData\Local\Microsoft\Windows\Temporary Internet Files\Content.Word\scan0022.jpg4 to 1 Air is cooled at constant volume back to its original pressure and temperature. No work is done. Heat is rejected at constant volume .Real 4 Stroke Cycle SI Engine

Also the real 4 stroke cycle includes an exhaust stroke 4-5 and an induction stroke 5-1. For naturally aspirated spark ignition engines the induction stroke occurs below atmospheric pressure resulting in a pumping loss. This is exacerbated at part load conditions. When the throttle is nearly closed. This sub-atmospheric pressured has to be recovered during the compression stroke and therefore reduces this power and the efficiency of the cycle.C:\Users\Martin\AppData\Local\Microsoft\Windows\Temporary Internet Files\Content.Word\scan0024.jpg2 ii)

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2 iii) dC:\Users\Martin\AppData\Local\Microsoft\Windows\Temporary Internet Files\Content.Word\scan0028.jpg1-2:- Reversible isothermal compression heat output Qout2-3:- Reversibleadiabatic compression3-4:- Reversible isothermal expansion. The ideal gas absorbs heat Qinwork done.4-1:- Reversible adiabatic gas expansion/ Gas expands and does work on surrounds which causes system to cool to a lower temperature.

2iii) eThe importance of the Carnot CycleHeat transfer in the carnot cycle is at constant temperature. This is the most efficient way of transferring heat into or out of a fluid. Heat transfer into the cycle occurs at a high temperature (That). Heat transfer out of the cycleoccurs at a cold temperature (T cold).Efficiency of the carnot cycle is as follows:-C:\Users\Martin\AppData\Local\Microsoft\Windows\Temporary Internet Files\Content.Word\scan0029.jpgOtto, Diesel and mixed cycles all have efficiencies less than the Carnot efficiency when operating between the same temperature limits.2 iii) fEngine EfficiencyNo enginecan be 100% efficient because some work is dissipated by fiction between the piston and cylinder as well as into the bearings. Also due to the inefficiencies in the fuel and air mixing process no all the fuel and air mixing process not all the fuel that is supplied is burnt some passes straight through the combustion process unburnt forming hydrocarbons in the exhaust.

3)IntroductionThis is a report into the thermodynamic improvements made by supercharging, turbocharging and engine management systems.3 a) Superchargers Increase the volumetric efficiency in the cylinder by increasing the mass flow. As on the inlet stroke the pressure is above atmospheric pressure pumping losses are reduced. Atmospheric pressure does not need to be recoveredduring theinductionstroke therefore efficiency is increased. Thereby improving performance.Most motorsport superchargers arescrew types. The air is drawn into the top of the supercharger using twin screws.http://image.popularhotrodding.com/f/10190564/0808phr_05_z+2008_pontiac_g8+tvs_blower.jpghttp://static.ddmcdn.com/gif/super-charger-13.jpg[William Harris, (2011)][(Popular Hot Rodding. (2014)]The supercharger has a belt which connects to the splined shaft, connect to the pink screw in fig 2. Superchargers do have the draw backs one is being drivenbythe engineasthey the can use up to 20% ofenginepower.Superchargingalso placesmore stress onotherengine components, such as the pistons, con-rods and head gaskets.Mercury Verado 250 HPBelow is a flow diagram of a supercharger system, the air enters the system at (A) the air intake it then flows to the supercharger C and into the intercooler D which cools the air down to increase its density. (B) the boost control valves regulate the air entering the engine to avoid damage.
[Boattest.com. (2014)]http://newmexicosolarandwind.com/Turbos%20Simplified_files/image001.gif3 b) Turbochargers Have the same effect as superchargers as theyalsoincrease volumetric efficiency. They also create pressure above atmospheric during the induction and compressionstroke, therefore as with superchargers pressure is not recovered during the compression strokethereby improving performance. They decrease pumping losses on the induction stroke and increase pumping losses on the exhaust stroke due to back pressure.[New Mexico Solar Wind, (2012)]Whereas superchargers draw air into the engine using a belt driven by the engine turbocharges have two wheels one which acts as a compressor (compressor wheel) and another which acts as a turbine (turbine wheel) to drive the compressor wheel. A drawback of turbochargers is the extra stress on the engine similar to superchargers. Another difficulty which superchargers dont have is turbo lagthis is caused by the time taken for the turbochargertoachieve sufficient speed to generate the required boost.Turbo lag can causea pressure drop in the induction systemcan have detrimental effect on the pressure during the induction strokecausing ittotemporarily bebelow what it would be in a naturally aspirated engine.Turbocharger flow diagram:- Air is drawn into the compressor case via the compressor wheel. It them moves down the compressor pipe/hose into the intercooler, to be cooled to increase its density and therefore the amount of oxygen in the combustion chamber. Theexhaustgasses then flowout of the engine through the exhaust valve, to the turbine via the turbine pipe/hose. The waste gasses spin the turbine, the more waste gasses run through the turbine the fast the compressor wheel spins and hence the more oxygen flows into the engine. Not shown on this diagram is the waste gate, waste gates direct exhaust gasses away from the turbine wheel, reducing the RPM of the compressor wheel to prevent damage to the engine. The compression ratio forturbocharged engines is generally lower than naturally aspirated engines to limit cylinder pressure.http://www.beesandgoats.com/boostfaq/turbo_diagram.jpg

[Barry Brideau, (2010)]3c) Engine management Engine management systems improve engine performance using techniques such as altering cam profile. Altering the cam profile for example increasing valve liftand periodwillimprove volumeair entering the cylindersimproving volumetric efficiency therebyhaving a similar effect to that of compressors such as superchargers and turbochargers. This reduces the pressure loss on the induction stroke, and the pressure that must be recovered on the compression stroke. Delayed ignition can also cause a loss of pressure in the cylinder and therefore a loss of work done.Enginemanagement systems cancontrol the ignitiontimingmore preciselythanmechanical distributorsfor example. Engine management systems can also manage fuel timing to the optimum level.http://image.modified.com/f/tech/modp-1211-2003-honda-civic-si/40416452/modp-1211-02%2B2003-honda-civic-si%2Becu.jpgEngine management systems are often combinedinto one ECU which also controls engine related ancillaries. The sensors and actuatorsmay control ignition timing (whichaffects the thermodynamic cycle of the engine) arethe spark plugs areconnectedvia on-plug ignition coilsto the ECU (plugs shown in fig 5). Sensors which may input toignition timing include Throttle position sensor (TPS) crank position sensor (CPS), the actuators include the ignition coils and spark plugs. Enginemanagement systems carry extra costbecause of the additional sensors and actuators compared, to mechanical systems,buttheengines will operatemore efficiently with their usethey may be more susceptible to electronic noise and disturbance.Engine managementsystems are also more costly to engineer due to the additional time taken for up-front engineeringand development of the engine management systemcalibration, its communicationsand diagnostics.[Modified, (2010)].ConclusionEngine management systems arevery effective at improving the performance of engines.Superchargers arevery effective atimproving volumetric efficiencyandreducingpumping losses on the induction stroke, butdoabsorbsomeof the power theyproduce as they driven by the engine.Turbo-chargers are also very effective atimproving volumetric efficiencyand reducing pumping loses during the induction stroke butcan suffer from a lagwhilst thecompressor wheelachieves its optimum speedto achieve sufficient boost pressure. Ifthe compressor isspinningtooslowlythe turbochargermaycause apressuredrop inthe inductionmanifold and thereby restrict performance. Both systems have pros and cons the weighting of these pros and cons is dictated by the vehicles they are applied to.

4) AcronymsMass of fuel (MF)Fuel Power (Fp)Brake power (Bp)Mean effective pressure (MEP)Indicated Power (IP)Mechanical efficiencyIndividual thermal efficiencyOverall efficiency

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BibliographyBarry Brideau, (2010),Turbocharger Flow Diagram[ONLINE]. Available at:http://www.beamalarm.com/Documents/how_does_a_turbo_work.html[Accessed 02 June 14].Boattest.com. (2014).Mercury Verado 250 HP. [ONLINE] Available at:http://www.boattest.com/engine-review/Mercury/7000028_Verado-250-HP_2013rel2502. [Accessed 02 June 14].New Mexico Solar Wind, (2012),Turbocharger Diagram[ONLINE]. Available at:http://newmexicosolarandwind.com/Turbos%20Simplified.htm[Accessed 02 June 14].Modified, (2010),THonda Si ECU[ONLINE]. Available at:http://www.modified.com/tech/modp-1211-2003-honda-civic-si/photo_02.html[Accessed 02 June 14].Popular Hot Rodding. 2014. (2008) Pontiac G8 Magna Charger G8 Supercharger Kit Photor Gallery. [ONLINE] Available at:http://www.popularhotrodding.com/tech/0808phr_2008_pontiac_g8/photo_05.html. [Accessed 02 June 14].William Harris. (2011).How Superchargers Work. [ONLINE] Available at:http://static.ddmcdn.com/gif/super-charger-13.jpg. [Accessed 02June 14].

Thermodynamics 302/06/2014