Variable compression ratio

inconstant compaction dimensionCHAPTER 1BACKGROUND THEORY OF ENGINES1.1 variant COMPRESSION RATIO (videocassette recorder) ENGINE1.1.1 INTRODUCTION TO VARIABLE COMPRESSION RATIO ENGINEVariable condensate symmetry (videocassette recorder) is a system which is subroutined to adjust the calculus symmetrys of the internal burning rail path locomotive. In guileless harm, it qualifys the combustion chamber size of the cylinder according to various different operating conditions such as speed, turn on, accele balancen and torque. Car sackings and provide economy ar two chall(a)enges for the automotive sector in which videocassette recorder locomotive locomotive locomotive is a very decent technology approaching low fuel consumption and pollutant sacking reduction. The simple machine manufacturers have to look forward for more(prenominal) thermally efficient and less polluting engine. In front world the automotive sector spends over millions of dollars for approachi ng low emission as sanitary as low fuel consumption railway gondolas. Various different ways are been discovered such as hybrid cars, fuel cell cars, solar cars and m some(prenominal) more as future development. videocassette recorder engine would a great deal prove to be boon for automotive sector (Evolution Perspectives). The Fixed Compression Ratio (FCR) engine has a fixed coalescence ratio without any soft of change in the size of the combustion chamber in cylinder. The FCR engines have gritty emissions due to the fact that when it comes to game speed or load, FCR use more fuel which produces more emissions but videocassette recorder engine provides increase in the fuel dexterity under varying loads and speed. Most of the cars used recently are Spark plug (SI) or diesel Ignition engines. The different ways the SI engine butt increase its energy is by higher abridgment ratio, reducing throttle losses, low friction, unsettled timing valve and down-sizing. The concept of VCR engine signifi coffin nailtly contributes its benefits to thermo-dynamic efficiency. The concept of the VCR is that it continuously operates at different coalition ratio as per the conduct of the performance. The change in the combustion chamber tidy sum continuously affiances sit with the varying in the compression ratio. therefore the thermodynamical advantages are been encountered through the engine map. At low level of power, VCR engine drives at higher compression ratio which can capture high fuel efficiency and at the high power levels the VCR engine runs at low compression ratio to prevent whang. tall(a) as FCR engine, the VCR engine keeps the engine temperature more or less at the optimum with high combustion efficiency. It scats to keep high power at the same engine dimensions (Amjad Shaik, 2007).1.1.2 ADVANTAGES OF VCR ENGINE straightaway the environmental safety is a very big issue which is been concerned by many industries throughout the world. When it c omes to the automobile sector, due to high ethical measures they have high amount of responsibility towards environment. All car manufacturing industry are targeting eco-friendly vehicles and down-sizing engine which can lead to the expose living environment. In this case VCR engine has many improvements and benefits over FCR engine. All that is possible by the VCR is not been possible by FCR engine in terms of power output as wellhead as overall efficiency. some remarkable evaluation perspectives of VCR engineCompression ratio valuation account does not allow knocking, and allows extreme torque and specific power with great crusade conditions.At part loads the VCR engine functions under high compression ratio (up to 161 or 171) which provides damp fuel efficiency compared to FCR engine.By retaining in best combination between Ignition advance and compression ratio, VCR engine reduces emission pollutant even under extreme supercharging pressure.VCR engine tends to keep the the rmodynamic temperature of the engine low compared to FCR by working under preferable compression ratio range and overturn engine heating.It yields increasing load-speed range which can end to effectiveness in lean-mixtures. The temperature and pressure controls which can permit combustions under ultra-lean mixtures and to set the auto-ignition timing precisely. The overall efficiency of the vehicle increases with pleasant driving conditions. 1.1.3 EXISTING VCR ENGINE CARS Today, in automobile sector there are various different companies who are disbursement billions of dollars on the green car. The aim to keep the environment clean need the cars to lower down their emission and the car manufacturers are spending major of their finance on the research and development. The company are growth no. of different ways that can process them to minimise the car emissions and hence make an eco-friendly car. Honda association Ltd has shown some documents to the World Congress unfoldin g their development in the recent times when it comes to variable compression ratio engine. They are growing a compact VCR model which pass on use inactivity constrict of the plunger to switch the compression ratio between high and low stages (Concept Honda RD Developing Variable Compression Ratio Engine with Dual Piston tool, 2009). Secondly SAAB has approached to make a very forward-looking and efficient VCR engine. At Geneva Motor Show, SAAB had reviled its VCR model which is called as the SVC (Saab Variable Compression) engine. The wise innovative concept was more fuel efficient and the concept was totally new. The performance of the engine was cold better than before with combination of reduced engine displacement and unique system of variable compression ratio enabling the engine to be more powerful and efficient than before. The fuel consumption of the car is reduced by 30% while the carbon emissions reduced as well. The CO, NOx and HC emission will meet all the futur e regulations (Saab Variable, 2008). The SVC engine system would not allow any kind of foreign or internal friction to the engine under operation which can tend to increase losses. The engine combustion chamber would not be detoriate by any kind of system interference (Miller, 2001). Nissan has been developing a kind of piston- frosting apparatus by the inspection and rep crinkle of which the system to enable the variable compression ratio of the engine, unlike the static compression ratio which was taking place as the other cars. The system optimises the engine rpm with the compression ratio and can easily vary with the car driving speed which results in optimum combustion all time and raising output and fuel economy (Nissan). This all schooling really conveys that the automotive sector is keenly looking forward for various ways and innovative mechanics which can prove to be boon for the future car market as well as eco-friendly environment. 1.2 FIXED COMPRESSION RATIO (FCR) EN GINE1.2.1 INTRODUCTION TO FIXED COMPRESSION RATIO ENGINEA fixed compression ratio engine is a normal engine which recent cars have. The compression ratio of the combustion chamber remains the same throughout the operation. erupticularly they do not have any disadvantages but when we compare it with the VCR engine than they have high fuel consumption as well as emissions. An engine is the main component of the car on which the major amount of car efficiency is depended. The major number of cars on the road is fuel cars, gasoline or diesel cars. The function of car engine is to interchange the fuel (gasoline) into relocation by which the car moves. The car is running through fuel combustion, so the engines are known as Internal flame Engines. It is known as Internal Combustion Engine because it rests of a combustion chamber in which the combustion of fuel occur development oxidiser, commonly tune. (Brain, 2010). 1.2.2 FOUR-STROKE INTERNAL COMBUSTION (I.C) ENGINEThe four bezz ant engine consists of four different bezzants-Intake gashCompression strokeCombustion stroke take up strokeThe Piston moves downwards form the ch communication channel unfounded centre (TDC) to the croup dead centre (BDC) reducing the pressure inside the cylinder. Suction phenomenon takes place where the mixture of fuel and air is forced to get in to the cylinder through the intake look for future combustion process. The intake valve is open in intake stroke where the exhaust valve is closed. As before long as intake stroke completes the intake valve closes down. 2. COMPRESSION STROKECompression stroke is the second stroke of the combustion process. In combustion process the inlet and the exhaust both the valves remain close. The piston is moves upwardly to the top dead centre of the cylinder to compress the air-fuel mixture. This makes an explosion in the cylinder and functions the combustion to take place. This complete stroke is known as the compression stroke. 3. EXPAN SION STROKEExpansion stroke is besides known as the power stroke. In this stroke both intake and exhaust valve remain close. When the piston is at the top dead centre, the ignition takes place in the combustion chamber usually with the help of spark plug. The air-fuel mixture ignites and results in to massive pressure and this pressure drives the piston back to the bottom dead centre with a huge force. This complete stroke is called the power stroke because at this stroke of the substantial pedal the power erupts and engines torque is able to drive the car. Power stroke is the most important stroke of the complete cycle in which the ignition takes place leading to power to the engine. 4. EXHAUST STROKEExhaust Stroke is the final stroke of the cycle. In this stroke the inlet valve remains closed and the exhaust valve opens. The piston which is at the bottom dead centre once again goes to the top dead centre panorama while the valve is open. The action helps to though out the prod uct of the combustion from the cylinder outside through help of the exhaust pipe. With the completion of the exhaust valve the completion of the combustion cycle takes place. (Brain, 2010)1.3 COMPRESSION RATIOThe Compression Ratio of an internal combustion engine is the ratio of the majority of the combustion chamber when the piston is at the bottom dead centre speckle divided by the volume of the combustion chamber when piston is at the full compression position. In simple terms it is also known as the swept volume (Compression ratio, 2010). The compression ratio of an engine should be higher. Higher the compression ratio, the engine is able to extract more energy form the given mass of the air-fuel mixture because of the higher amount of thermal efficiency. The increase in the power takes place at the moment of ignition and more net work can be achieved by expanding the hot gases at a greater degree. There is major disadvantage while tutelage the compression ratio higher is t hat make the gasoline engine subjected to engine knocking. In technical terms it is also known as detonation. It is mainly caused by using poor quality fuel. Detonation can cause the engine to reduce its overall efficiency, damage the engine part and even can result to engine failure. CR = compression ratio Vd = displacement volume Vcv = clearance volume CR = Displacement Volume+Clearance VolumeClearance Volume Compression Ratio = Vd+ VcvVcvCHAPTER 2DESCRIPTION OF VCR PROTOTYPE MODEL2.1 DESCRIPTION OF EXISTING VCR PROTOTYPE The variable compression ratio exemplification is already been made by the previous student working. The driving tool is well made and is practically operational. The mechanism is very simple. The driving mechanism of the ikon is just an understanding of the overall system and helps to consider different moving part. The modifications been done are on the way the system has to be operate. The mechanism was been driven manually or by using an electric motor . The system has to be modified and designed to be driven pneumatically. The complete prototype helps to demonstrate the complete system visually. The theoretical part of the VCR is a bit more complicated, so the visual model really focuses and gives a very clear intellect about the whole mechanism as well individual parts. The mechanism shows the rotating snapshot motion reincarnation to the linear motion of the piston-cylinder mechanism driven manually, electrically or pneumatic sources. The variable compression mechanism is been attached to the system by which the angles of connecting rod lever can be changed which helps to change the travel continuance of the piston in the cylinder. The change in piston travel length tends to change the swept volume which is technically known as the compression ratio. The mechanism is designed is a way that the compression ratio can be changed easily any time even when the system is running. The angle of eccentric adjustment is given a range from 0 to 60 where it can change compression ratio to certain(p) extends. 2.2 WORKING PRINCIPLE OF VCR PROTOTYPEThe working of the prototype is very simple. The working principle is that the angular motion of the shaft is been converted in to the linear motion of the piston-cylinder. A simple mechanism of the variable compression ratio is adjoined to the overall system. The variable compression ratio mechanism in the system allows the driving mechanism to change various angles by help of which the length of the stroke of piston changes which can change the overall swept volume. Hence the change in swept volume results in the variation in compression ratio. NOTE The figure shows the working principle of the prototype by giving more familiarity about the moving parts and their connection. Detailed drawing is been given further in the report. The driving mechanism consists of various different moving parts as described in the part list. The extension shaft rotates at an angle of 36 0 which results to one to and fro motion of the piston. Once the extension shaft rotates, the motion is been rapturered to the Crank shaft. The crank shaft transfers the motion to the eccentric journal bearing through the help of connecting rod and lever. At that position the angle of the eccentric mechanism decided the length of stroke of piston. This motion hence results into linear motion of the piston-cylinder mechanism by help of sliding mechanism connection. The piston than moves and completes a two stroke cycle by one revolution of shaft. 2.3 MOTION TRANSFER STUDYA simple overview of the motion transfer from one part of mechanism to the other is been shown.DRIVING SOURCEROTATING SHAFTCONNECTING ROD MOTION outre JOURNAL BEARING MOTIONSLIDING MECHANISM CONNECTIONLINEAR MOTION OF PISTON-CYLINDER2.4 PART enumerate OF PROTOTYPE MODEL PART LIST OF VCR DRIVING MECHANISM image No.Part Name Quantity1Cylinder Head12Cylinder clog13Piston14Roller Bearing35Sliding Mechanism Connection 16 uncommon Journal Bearing27Connection retinal rod Lever18Connection Rod19Crank Shaft110Crank Shaft attach111Extension Shaft112Nut Bolt12NOTE The above part list is made on the background of the system without any sort of driving mechanism modifications. The source of driving is manually which helps us to consider the movement of prototype parts and is simple understanding of the mechanism. 2.5 COMPONENT strong SELECTION The variable compression ratio prototype is overall well designed. The completely prototype is a compact model and has an appropriate function. The mechanism of VCR is well managed when it comes to design part. The design is kept simple and easy to understand. The assembly of all components is done in a way that it is easy to disassemble and individual moving parts can be analysed. It is clear that the system is a complete assembly of many working parts. There are lots of parts which are been assembled using welding, or by using nuts and bolts. Some of the p arts are been manufactured in the laboratory and some are been obtained from the suppliers due to time and material constraints. The parts which are been obtained directly from the dealerConnecting RodRoller BearingsCrank ShaftConnecting Rod LeverEccentric BearingNuts and BoltsThe parts which are been manufactured in the laboratoryPistonCylinder BlockPrototype foundation (wooden base)Extension Shaft (Attached to electric motor)Supporting bars for assemblyCOMPONENT AND THEIR MATERIAL Part No.Part Name Material1Cylinder Head fictile 2Cylinder BlockPlastic3PistonPlastic4Roller BearingPlastic5Sliding Mechanism Connection brace 6Eccentric Journal BearingSteel7Connection Rod Lever bad Steel8Connection RodForged Steel9Crank ShaftForged Steel10Crank Shaft MountingAluminium 11Extension ShaftCast Iron12Nut Bolt small Steel Material Selection Criteria As we can see the material been used in the prototype are metals and have high resistivity to high temperature and external or internal stress es. They do not have a tendency to deform under small loading conditions which really helps to keep the coalescency and working of the prototype without any problems. The components are directly available in the market and it save a lot of time as well as money which can be spending innovating confused ideas. CHARACTERISTICS OF THE VCR PROTOTYPEEvery product or its prototype has some positive as well as negative aspects. The positive features are those which favour the users and the negative aspects are those which create some kind of errors or functional faults. POSITIVE CHARACTERISTICSDESIGNThe complete system is designed in a way that it is really appreciated. The design is compact, easy to analyse and low weight. Even though the material used in most of the parts is metals but even though the overall prototype does not exceed a lot. Looking at the individual design in detailThe existing VCR prototype consist INTRODUCTION TO PNEMATIC SYSTEMpneumatic is a branch of technology wh ich enables the pressurised gas to affect mechanical motion. Pneumatic system is the system which helps to pressurise gas and convert the pressure of gas in to mechanical motion. There are many industry which use pneumatic systems for various purposes. The compressor is used to compress air and this force of air is used for the various purposes such as dentistry, construction, automobile, mining and many more. Pneumatic system is fundamentally a fixed system which is installed in factories that have application of compressed air for various purposes. unremarkably the moisture is been removed from the air and small quantity of oil is been added in it as lubrication to the moving parts. The underlying pneumatic system is most efficient when the theoretical calculation prove basic three things tally of force applied by the actuatorCan that force be able to move the desired loadThe speed at which the load can be movedComponents of Basic Pneumatic SystemPart A Compressor The compress or is the main component of all. It is a pump which compresses air. It simply raises the pressure of compressed air and supplies it to the pneumatic system.Part B Check valve Check valve is simple one way valve. This valve allows the compressed air which is having high pressure to enter the pneumatic system. It does not allow the back flow of air again in to the compressor.Part C Accumulator Accumulator is known as the remembering tank of the system. It stores the compressed air and hence helps to supply it to system as per the requirement and relieves the duty cycle of compressor.Part D directive Valve The directional valve gives the direction to the compressed air and controls the flow of air from source to port selected. This can be done manually or might be used sensors or electrically to give better precision. Part E Actuator Actuator is the device which concerts the force (energy) of compressed air into the mechanical motion. (Elements of Basic Pneumatic system, 2003) on the job(p) of Pneumatic systemAtmospheric air is been drawn in to the air filter in which the air is been filter. The foreign material, duct particles are been removed and pure air is achieved. The air then passes to the compressor where it gets compressed to a certain required pressure. The vapour and humidity is been removed making air dry and pressurised. Then the air is passed to the reservoir where the pressured air is been stored and can be readily available when required. It is known as accumulator. Many companies tend to compress air in a huge compressor and then store it in different storage reservoirs at different places without any kind of pressure (energy) loss. The pressure development is been depended on the size and electrical condenser of the compressor. There are many safety devices used in the system like valves and sensors which readily help to ensure complete safety of the system. After it is stored in the reservoir it is been used whenever and wherever requir ed using control valve which can help to control the flow of pressurised air and help to use the energy to convert to mechanical motion.