CYLINDER MANAGEMENT full report
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Active fuel management is one of the important concerns in the present day automobile industry. Cylinder management is a variable displacement technique adopted to increase the fuel efficiency of the engine. The technique aims at having more efficient power trains for cars. Depending upon the power requirements of the car the cylinders of the engine are made operational. In cases where the power requirement is less, as in the case of heavy traffic, a few of the automobile IC engine cylinders are shut down. The process of deactivating the cylinders at part load is analogous to the fitting of a smaller engine for a shorter period. In contrast when the power requirements are high, such as during acceleration, all the cylinders of the engine are made operational. This paper explores the developing concept and technology for Cylinder Management which aims at improving fuel efficiency of automobile engines.
Active fuel management is one of the important concerns in the present day automobile industry. Because of fuel crisis in recent years, considerable research efforts are being made for Fuel management. Making engines efficient is a very important factor to overcome future fuel crisis. Considerable research efforts are being made to increase the efficiency of an internal combustion engines. To have more efficient power train in cars gave rise to a concept called CYLINDER MANAGEMENT. Cylinder Management involves the selective operation of cylinders of an engine according to the power requirements of the vehicle. Depending upon the power requirements of the car the cylinders of the engine are made operational. In cases where the power requirement is less, as in the case of heavy traffic, a few of the automobile IC engine cylinders are shut down. This makes the optimized use of fuel possible and there by enhancing the fuel efficiency of the engine.
The term Active Fuel Management was first coined by the General Motors. Active Fuel Management (formerly known as Displacement on Demand) is a trademarked name for the automobile variable displacement technology from General Motors. It allows a V6 or V8 engine to "turn off" half of the cylinders under light-load conditions to improve fuel economy. The Environmental Protection Agency (EPA or sometimes USEPA is an agency of the federal government of the United States charged with protecting human health and with safeguarding the natural environment: air, water, and land) tests show a 6% to 8% improvement in fuel economy, but real-world highway use promises even larger gains. GM's current Active Fuel Management technology uses a solenoid to deactivate the lifters on selected cylinders of a pushrod V-layout engine. The concept of cylinder management can help in achieving an increased fuel efficiency there by saving large quantities of fuel.
Cylinder deactivation is an advanced fuel economy boosting process. Cylinder deactivation is a variable displacement technique adopted to increase the fuel efficiency of the engine. Variable displacement is an automobile engine technology that allows the engine displacement to change for improved fuel economy. The cylinder deactivation system turns off half of the engineâ„¢s cylinders under certain driving conditions. The simple fact behind this system is that a few of the engineâ„¢s cylinders is shut down when less power is needed and there by saving fuel. Based on the power requirements of the car the cylinders of the engine are made operational. Whenever the power requirement is less, as in case of heavy traffic or when under gentle acceleration on motorway, a few engine cylinders are shut down and this leads to optimized consumption of the fuel. And on high power requirements, such as during acceleration of the car, all the cylinders of the engine are made operational. The process of deactivating the cylinders at part load is much like temporarily fitting a smaller engine.
Cylinder deactivation is used to reduce the fuel consumption and emissions of an engine during light load operation. Reduced fuel consumption saves the costly fuel and also results in smoother and safer operation of the engine with decreased pollution. In typical light load driving you use only around 30 percent of an engineâ„¢s maximum power. In these conditions, the throttle valve is nearly closed and the engine needs to work to draw air. This causes an inefficiency known as pumping loss. Mercedes says that some large capacity engines need to be throttled so much at light load that the cylinder pressure at Top Dead Centre is approximately half that of a small four-cylinder engine. Low cylinder pressure means low fuel efficiency. The use of cylinder deactivation at light load means the throttle valve can be opened further to provide the same power output. This reduces pumping losses and increases pressure in each cylinder. Fuel consumption can be improved by around 20 percent in highway conditions.
CYLINDER DEACTIVATION IN DIRECT INJECTION ENGINES
Far more familiar and already in production with Mitsubishi, Volkswagen, Audi, Peugeot and Mercedes is the direct injection petrol engine but its benefits are far less clear cut and rely very much on driving style. Conventional carbureted or port injection petrol engines all have several things in common. They all ingest a Ëœhomogeneousâ„¢ mixture of evenly mixed fuel droplet and air. They all operate at a Ëœstoichiometricâ„¢ air/fuel ratio of 14.6:1 and all modern injection engines use three way catalytic converters to reduce emissions of hydro carbons, carbon monoxide and nitrogen oxides. Three way cats are so called because as long as the engines air/fuel mixture is maintained at stoichiometric, they can successfully remove a large percentage of all three pollutants from the exhaust. Run the engine too rich or too lean and the balance is spoilt sending emission soaring.
Like direct injection diesel, direct injection petrol engines rely on very accurate injectors and control systems such as those produced by Delphi or Bosch. GDI (gasoline direct injection) engines work by sucking air through inlet ports as usual, but fuel is injected into the cylinder. The crucial difference is that the air and fuel is not mixed Ëœhomogeneouslyâ„¢ but is delivered as a Ëœstratified chargeâ„¢, a ball of fuel droplets injected straight in to the cylinder like a tiny rain cloud surrounded by what is almost fresh air. The result is the air/fuel mixture is very lean indeed, as lean as 50:1, there by cutting fuel consumption dramatically.
But the simple fact is, there is no such thing as a free lunch and burning less fuel produces less power. So direct injection engines have to switch between two modes â€œËœstratifiedâ„¢ (lean) mode at low throttle openings ,say, around town and more conventional homogeneous mode â€œ for higher power. It doesnâ„¢t take a genius to work out that making impressive savings made by some manufacturers (up to 15 percent in the case of Volkswagen and Audi) involves being extremely light footed with the accelerator pedal and thatâ„¢s where more advanced strategies, such as controlled auto ignition (CAI), could be much more effective at saving fuel and cutting emissions.
The deactivation process is done by mechanically disabling inlet and exhaust valves. Cylinder deactivation can be done by various methods.
1. Cam profile switching.
2. Camless drive technology.
3. Active valve train.
CAM PROFILE SWITCHING
Cam profile switching tappet is used to switch between two different cam profiles (different cam lobes adjacent to each other on the camshaft). It will allow engine to manageable at low speed while delivering max power at the top end.
In this method cylinder deactivation is done by switching between a normal cam lobe and a plain, circular lobe which does not produce any valve lift.
CAMLESS DRIVE TECHNOLOGY
Camless engines use solenoid valves instead of the conventional camshaft, cams, gears, rocker arms combination. Solenoid valves are driven electronically allowing completely freedom of valve control. A microcontroller controls the opening and closing of the valves instead of cam lobes actuating rocker arms. The absence of all that mechanical bulk allows for a lighter and more compact valve train package. It also doesnâ„¢t require a timing belt anymore.
Camless engines have been around for the past 5 years in testing phases and used in competitions but very few have been put into production cars yet. Itâ„¢s the next logical step from the current variable valve timing and cam profile phasing technologies that try to go around the limitation of a camshaftâ„¢s fixed timing properties. With the flexibility of the valve being electronically controlled, maximum torque at all engine revs and the best fuel mileage possible. A racing cam is shaped to optimize engine output at high speeds without regard for the way it roughens up an idle. With camless valve trains, we donâ„¢t have to live with that.
ACTIVE VALVE TRAIN TECHNOLOGY
Lotus which has been working on cylinder deactivation since the late 1990â„¢s, has high hope for its future. Current deactivation systems work by mechanically disabling the inlet and exhaust valves, but things could become simpler in future cam less engines. Lotus Active Valve Train (AVT) technology is still at the research stage and does away with camshafts altogether. Instead, the valves are operated by high-speed hydraulic actuators allowing infinitely variable valve timing and lift. AVT is expected to appear on a production car for the first time in 2008. Renault has also experimented with cam less valve train using sprigs and solenoids.
CONTROLLED AUTO IGNITION
Being able to time the timing and lift of valves to an infinite degree creates immense possibilities. One such example is controlled auto ignition (CAI). It works in absence of one crucial independent-spark. Instead of the usual sparkplug, firing at a carefully timed moment to set the compressed charge of fuel alight, compressed auto ignition instead work by trapping a portion of hot exhaust gases from the previous cycle, their heat igniting the incoming fuel spontaneously.
This is done by trapping the exhaust gases in the cylinder and with active valve train, by closing the exhaust valve early on the exhaust stroke before all the exhaust gases has been expelled. The trapped gases are compressed and expand again as the piston goes over top dead centre. At the same time the inlet valve opens to let the fuel and air, which mixes with hot gas. When the compression stroke follows as normal, the mixture ignites automatically.
At idle speeds, compressed auto ignition is less effective because exhaust gas temperature are low and so it is necessary to revert to a spark. Hence change to spark ignition at idle speeds. At compressed auto ignition engine out NOx is reduced by more than 90% compared to a conventional spark ignition petrol engines.
BALANCING THE ENGINE AT THE TIME OF DEACTIVATION The Delphi cylinder deactivation power train mount is an adaptive hydraulic mount that helps provide improved vibration isolation during engine idle and cylinder deactivation events. The mount creates a dynamic stiffness reduction (rate dip) at frequencies related to engine idle and cylinder deactivation conditions, without sacrificing isolation or performance at higher frequency operation. The dynamic properties of this adaptive mount change directly according to engine rpm. The electronic controls and actuation of this controllable mount are completely integrated into the mount itself, requiring only power, ground, and an engine rpm signal.
The cylinder deactivation power train mount is applicable where additional power train isolation is desired, and is particularly intended for a vehicle that has large power train forcing functions, such as cylinder deactivation gas engine and diesel engine applications. The cylinder deactivation power train mount can provide the additional isolation required to enable cylinder deactivation vehicles to idle in the reduced cylinder mode, which helps result in further fuel economy.
The cylinder deactivation power train mount uses the principle of fluid inertia to generate a dynamic rate dip that results in a decrease in stiffness of the mount at the desired frequency. The stiffness of the mount can be reduced without large, costly high-powered actuators. The mount simply generates the stiffness reduction through the natural flow of fluid in the mount, which results in a minimal impact on the package size, cost, and power requirements of the mount.
The diverse technologies adopted for cylinder deactivation for attaining proper use of engine cylinders as per power requirement opens up a wide range of new possibilities. The automobile firms all over the world have been striving to manufacture engines that are more fuel efficient. The Concepts of Active Fuel Management and Cylinder Management are enlightening and can be developed to manufacture highly fuel efficient engines. The Automobile industry looks forward for the practical implementation of various Cylinder Management technologies to optimize fuel requirements and there by obtain increased efficiencies.
1. General Motors V8-6-4 (Cadillac)
2. General Motors Active Fuel Management
3. DaimlerChrysler Multi-Displacement System (MDS) (for Chrysler)
4. DaimlerChrysler Active Cylinder Control (ACC) (for Mercedes-Benz)
5. Honda Variable Cylinder Management (VCM)
6. Lotus Elise: Rover K Series
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