CAMLESS ENGINE SEMINAR REPORT PDF
Camless Engine seminar report in PDF explains how it works for greater optimization of overall engine performance during different phases of. Explore Camless Engine with Free Download of Seminar Report and PPT in PDF and DOC Format. Also Explore the Seminar Topics Paper on Camless Engine. Camless Engine Report - Free download as Word Doc .doc /.docx), PDF File . pdf), Text File .txt) or read This is to certify that the Seminar entitled CAMLESS.
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Camless Engines Seminar Report - Download as PDF File .pdf), Text File .txt) or read online. Camless Engines Seminar Report. Camless Engines Seminar Report. ACKNOWLEDGEMENT. I would like to thank everyone who helped to see this seminar to completion. In the camless technology valve motion is operated by valve actuators of electro- mechanical and electro-hydraulic type. In this seminar report we compare.
In such systems the issue of energy consumption is often unimportant. The system described here has been conceived for use in production engines. It was, therefore, very important to minimize the hydraulic energy consumption. Hydraulic pendulum The Electro hydraulic Camless Valve train, ECV provides continuously variable control of engine valve timing, lift, and velocity. It uses neither cams nor springs. It exploits the elastic properties of a compressed hydraulic fluid, which, acting as a liquid spring, accelerates and decelerates each engine valve during its opening and closing motions.
This is the principle of the hydraulic pendulum. Like a mechanical pendulum," the hydraulic pendulum involves conversion of potential energy into kinetic energy and, then, back into potential energy with minimal energy loss".
During acceleration, potential energy of the fluid is converted into kinetic energy of the valve. During deceleration, the energy of the valve motion is returned to the fluid. This takes place both during valve opening and closing. Recuperation of kinetic energy is the key to the low energy consumption of this system.. Figure 7 illustrates the hydraulic pendulum concept. The system incorporates high and low-pressure reservoirs.
A small double-acting piston is fixed to the top of the engine valve that rides in a sleeve. The volume above the piston can be connected either to a high- or a low-pressure source. The volume below the piston is constantly connected to the high-pressure source.
The pressure area above the piston is significantly larger than the pressure area below the piston. The engine valve opening is controlled by a high-pressure solenoid valve that is open during the engine valve acceleration and closed during deceleration. Opening and closing of a low-pressure solenoid valve controls the valve closing. The system also includes high and low-pressure check valves.
During the valve opening, the high-pressure solenoid valve is open, and the net pressure force pushing on the double-acting piston accelerates the engine valve downward.
When the solenoid valve closes, pressure above the piston drops, and the piston decelerates pushing the fluid from the lower volume back into the high-pressure reservoir.
Low-pressure fluid flowing through the low-pressure check valve fills the volume above the piston during deceleration. When the downward motion of the valve stops, the check valve closes, and the engine valve remains locked in open position. The process of the valve closing is similar, in principle, to that of the valve opening. The low-pressure solenoid valve opens, the pressure above the piston drops to the level in the low pressure reservoir, and the net pressure force acting on the piston accelerates the engine valve upward.
Then the solenoid valve closes, pressure above the piston rises, and the piston decelerates pushing the fluid from the volume above it through the high-pressure check valve back into the high-pressure reservoir. The hydraulic pendulum is a spring less system. Figure 8 shows idealized graphs of acceleration, velocity and valve lift versus time for the hydraulic pendulum system. Thanks to the absence of springs, the valve moves with constant acceleration and deceleration.
This permits to perform the required valve motion with much smaller net driving force, than in systems which use springs. The advantage is further amplified by the fact that in the spring less system the engine valve is the only moving mechanical mass.
If the ball is rotated such that the passage lines up with other openings in the valve assembly, gas can pass through it. Exactly like the ball valves many of us use valve is accomplished by electromagnets positioned around its exterior. Opening and closing the Referring to Figure 10, the valve housing 7 is shown in two pieces. Ball valve 8 has two rigidly attached pivots The disc 10 is permanently attached and indexed to the ball valve and contains permanent magnets around its perimeter.
The electromagnets 11 are situated on both sides of the ball valve 8 and they are fixed to the valve housing.
The electromagnets are controlled through the ECU. A crank trigger sensor on the crankshaft provides information about the position of the pistons relative to top dead centre. Thus, at top dead centre of the power stroke, the ECM could be used to fix the polarity of both electromagnets so that they are of opposite polarity to the magnets in the ball valve, rotating the ball valve to the closed position.
The substitution of a simple, efficient ball valve and valve housing arrangement in a a four stroke reciprocation piston engine eliminates all the independent moving parts in the valve train.
This may even be an improvement over the poppet valve camless system - the ball valve needs only to rotate on its axis to achieve the desired flow conditions, rather than be accelerated up and down in a linear fashion. A partially open ball valve state may also be able to be used to create more turbulence. Electromechanical valve train implementation would not be possible witha normal 12V electrical system.
As has been covered previously inAutoSpeed "Goodbye 12 volts Consequently, the energy demand of EMVT can be optimally matched by a crankshaft-mounted startergenerator KSG - in Siemens speak operating at 42V; it is integrated in the flywheel and designed for the starting process as well as generator operation. Electrohydraulic Poppet Valves In general terms, present designs of electrohydraulic valves comprise poppet valves moveable between a first and second position.
Used is a source of pressurised hydraulic fluid and a hydraulic actuator coupled to the poppet valve. The motion between a first and second position is responsive to the flow of the pressurised hydraulic fluid.
Camless Engines Seminar Report and PPT
An electrically operated hydraulic valve controls the flow of the pressurised hydraulic fluid to the hydraulic actuator. In one design, the provision is made for a three-way electrically operated valve to control the flow of the pressurised hydraulic fluid to the actuator. This supplies pressure when electrically pulsed open, and dumps actuator oil to the engine oil sump when the valve is electrically pulsed to close.
The use of engine oil as the hydraulic fluid simplifies and lowers the cost of the design by removing the need for a separate hydraulic system. The basic design of the electrohydraulic valvetrain hardware is illustrated in Figure The engine poppet valves 22 and the valve springs 24 that are used to reset them are shown.
The poppet valves are driven by hydraulic actuators 26 , which are controlled by electrically operated electro-hydraulic valves 28 supplying hydraulic fluid to the actuators via conduit The preferred hydraulic fluid is. An engine-driven hydraulic pump 32 supplies the oil pressure, receiving the oil from the engine oil sump The pump output pressure is also limited by an unloader valve 36 , as controlled by an accumulator 38 connected to the oil pressure rail.
With this design the hydraulic pump could be periodically disconnected, such as under braking, so that the valve train would run off the stored accumulator hydraulic pressure.
As is the trend with all modern engine systems, the camless engine has an even greater reliance on sensors. A valve developed by Sturman Industries is said to be about six times faster than conventional hydraulic valves. To achieve such speeds, it uses a tiny spool sandwiched between two electrical coils.
By passing current back and forth between the coils, a microprocessor -based controller canquickly move the spool back and forth, thereby actuating the engine valves in accordance. However, electrohydraulic systems are mostly being developed for diesel truck use because it is currently not clear whether the technology will have the speed needed for higher revving passenger car engines.
The Electro hydraulic Camless alve train, EC provides continuously variable control of engine valve timing, lift, and velocity. It uses neither cams nor springs. It exploits the elastic properties of a compressed hydraulic fluid, which, acting as a liquid spring, accelerates and decelerates each engine valve during its opening and closing motions.
This is the principle of the hydraulic pendulum. Like a mechanical pendulum, the hydraulic pendulum involves conversion of potential energy into kinetic energy and, then, back into potential energy with minimal energy loss. During acceleration, potential energy of the fluid is converted into kinetic energy of the valve. During deceleration, the energy of the valve motion is returned to the fluid.
This takes place both during valve opening and closing. Recuperation of kinetic energy is the key to the low energy consumption of this system.. Fig ure 7 illustrates the hydraulic pendulum concept. The system incorporates high and low - pressure reservoirs. A small double-acting piston is fixed to the top of the engine valve that rides in a sleeve. The volume above the piston can be connected either to a high- or a low-pressure source. The volume below the piston is constantly connected to the high-pressure source.
The pressure area above the piston is significantly larger than the pressure area below the piston. The engine valve opening is controlled by a high- pressure solenoid valve that is open during the engine valve acceleration and closed during deceleration.
Opening and closing of a low pressure solenoid valve. The system also includes high and low-pressure check valves. Figure 7. Hydraulic Pendulum. During the valve opening, the high-pressure solenoid valve is open, and the net pressure force pushing on the double-acting piston accelerates the engine valve downward.
When the solenoid valve closes, pressure above the piston drops, and the piston decelerates pushing the fluid from the lower volume back into the high-pressure reservoir. Low-pressure fluid flowing through the low-pressure check valve fills the volume above the piston during deceleration. When the downward motion of the valve stops, the check valve closes, and the engine valve remains locked in open position. The process of the valve closing is similar, in principle, to that of the valve opening.
The lowpressure solenoid valve opens, the pressure above the piston drops to the level in the low pressure reservoir, and the net pressure force acting on the piston accelerates the engine valve upward.
Then the solenoid valve closes, pressure above the piston rises, and the piston decelerates pushing the fluid from the volume above it through the high-pressure check valve back into the highpressure reservoir. The hydraulic pendulum is a spring less system. Figure 8 shows idealized graphs of acceleration, velocity and valve lift versus time for the hydraulic pendulum system. Thanks to the absence of springs, the valve moves with constant acceleration and deceleration.
This permits toperform the required valve motion withmuch smaller net driving force, than in systems which use springs. The advantage is further amplified by the fact that in the spring lesssystem the engine valve is the only moving mechanical mass. Tominimize the constant driving force in the hydraulic pendulum theopening and closing accelerations and decelerations must be equal symmetric pendulum.
Valve opening and closing A more detailed step-by-step illustration of the valve opening and closing process is given in Figure 9.
It is a six-step diagram, and in each step an analogy to a mechanical pendulum is shown. In Step 1 the opening high- pressure solenoid valve is opened, and the high-pressure fluid enters the volume above the valve piston. The pressure above and below the piston become equal, but, because of the difference in the pressure areas, the constant net hydraulic force is directed downward. It opens the valve and accelerates it in the direction of opening.
The other solenoid valve and the two check valves remain closed. In Step 2 the opening solenoid valve closes and the pressure above the piston drops, but the engine valve continues its downward movement due to its momentum.
The lowpressure check valve opens and the volume above the piston is filled with the low-pressure fluid. The downward motion of the piston pumps the high-pressure fluid from the volume below the piston back into the high- pressure rail.
This recovers some of the energy that was previously spent to accelerate the valve.
The ratio of the high and low-pressures is selected so, that the net pressure force is directed upward and the valve decelerates until it exhausts its kinetic energy and its motion stops. At this point, the opening check valve closes, and the fluid. This prevents the return motion of the piston, and the engine valve remains fixed in its open position trapped by hydraulic pressures on both sides of the piston.
This situation is illustrated in Step 3, which is the open dwell position. The engine valve remains in the open dwell position as long as necessary. Step 4 illustrates the beginning of the valve closing. The closing low-pressure solenoid valve opens and connects the volume above the piston with the low-pressure rail.
The net pressure force is directed upward and the engine valve accelerates in the direction of closing, pumping the fluid from the upper volume back into the low- pressure reservoir. The other solenoid valve and both check valves remain closed during acceleration. In Step 5 the closing solenoid valve closes and the upper volume is disconnected from the lowpressure rail, but the engine valve continues its upward motion due to its momentum.
Rising pressure in the upper volume opens the high-pressure check valve that connects this volume with the high-pressure reservoir. The upward motion of the valve piston pumps the fluid from the volume above the piston into the high-pressure reservoir, while the increasing volume below the piston is filled with fluid from the same reservoir.
Since the change of volume below the piston is only a fraction of that above the piston, the net flow of the fluid is into the high-pressure reservoir.
Again, as it was the case during the valve opening, energy recovery takes place. Thus, in this system the energy recovery takes place twice each valve event. When the valve exhausts its kineti c energy, its motion stops, and the check valve closes. Ideally, this should always coincide with the valve seating on its seat. This, however, is difficult to accomplish. A more practical solution is to bring the valve to a complete stop a fraction of a millimeter before it reaches the valve seat and then, briefly open the closing solenoid valve again.
This again connects the upper volume with the however, is difficult to accomplish. A more practical solution is to bring the valve to a complete stop a frac tion of a millimeter before it reaches the valve seat and then, briefly open the closing solenoid valve again.
This again connects the upper volume with the low-pressure reservoir, and the high pressure in the lower volume brings the valve to its fully closed position.
Step 6 illustrates the valve seating. After that, the closing solenoid valve is deactivated again. For the rest of the cycle both solenoid valves and both check valves are closed, the pressure above thevalve piston is equal to the pressure i n the low-pressure reservoir, and the high pressure below the piston keeps the engine valve firmly closed. Varying the activation timing of both solenoids varies the timing of the engine valve opening and closing.
This, of course, also vanes the valve event duration. Valve lift can be controlled by varying the duration of the solenoid voltage pulse.
Changing the high pressure permits control of the valve acceleration, velocity, and travel time. The valve can be deactivated during engine operation by simply deactivating the pair of solenoids which control it.
Deactivation can last any number of cycles and be as short, as one cycle. Increasing the number of valves in each cylinder does not require a corresponding increase in the number of solenoid valves.
The same pair of solenoid valves, which controls a single valve, can also control several valves running in-parallel. Thus, in a four-valve engine a pair of solenoid valves operates two synchronously running intake valves, and another pair runs the two exhaust valves. Unequal lift modifier In a four-valve engine an actuator set consisting of two solenoid valves and two check valves controls the operation of a pair of intake or a pair of exhaust valves. Solenoids and check valves are connected to a common control chamber serving both valves.
In a four-cylinder engine there are total of eight control chambers connected to eight pairs of valves. For each pair, the volumes below the hydraulic pistons are connected to the high pressure reservoir via a device called the lift modifier.
Cylinder head Two cross sections of the cylinder head are shown in Figure The aluminium casting is within the original confines and contains all hydraulic passages connecting the system components. The high- and low-pressure hydraulic reservoirs are integrated into the casting. The reservoirs and the passages occupy the upper levels of the cylinder head and are part of the hydraulic system. The hydraulic fluid is completely separated from them engine oil system.
Camless Engines Seminar Report
A finite element analysis was used to assure the cylinder head integrity for fluid pressures of up to 9 M a. The lower level of the head contains the engine coolant. Figure Cross sections of cylinder head. The engine valves, the check valves and the modifiers are completely buried in the body of the head.
The solenoid valves are installed on the top of the cylinder head and are kept in their proper locations by a cylinder head cover. Hydraulic and electric connections leading to the hydraulic pump and the electronic controller, respectively, are at the back end of the cylinder head. The height of the head assembly is approximately 50 mm lower than the height of the base engine head.
Figure 13 is a photograph of the head on the engine with the head cover removed. Components of camless engine 1. Engine valve 2. Solenoid valve 3. Lift modifier 4. High Pressure Pump 5. Low Pressure Pump 6. Cool-down Accumulator.
Figure 15 shows a cross section of the solenoid valve. The solenoid has conically shaped magnetic poles. This reduces the air gap at a given stroke. The normallyclosed valve is hydraulically balanced during its movement. Only a slight unbalance exists in the fullyopen and the fully-closed positions. A strong spring is needed to obtain quick closing time and low leakage between activations.
The hydraulic energy loss is the greatest during the closing of either the high- or the low-pressure solenoid, because it occurs during the highest piston velocity. Thus, the faster the solenoid closure, the better the energy recovery.
The valve lift and the seat diameter are selected to minimize the hydraulic loss with a large volume of fluid delivered during each opening. Both high-pressure and lowpressure solenoid valves are of thesame design. To conserve the mechanical power needed to drive the pump, its hydraulic output should closely match the needs.
A variable displacement, high efficiency, axial plunger-type pump was initially selected for that reason. Taking into account the prohibitively high cost of such pump for automotive applications, a low-cost variable capacity pump was conceived. A cross section of the pump is shown in Figure The pump has a single eccentric-driven plunger and a single normally-open solenoid valve. During each down stroke of the plunger the solenoid valve is open, and the plunger barrel is filled with hydraulic fluid from the low pressure branch of the system.
During the upstroke of the plunger, the fluid is pushed back into the low pressure branch, as long as the solenoid valve remains open. Closing the solenoid valve causes the plunger to pump the fluid through a check valve into the high pressure branch of the system. Varying the duration of the solenoid voltage pulse varies the quantity of the high-pressure fluid delivered by the pump during each revolution.
Low pressure pump A small electrically driven pump picks up oil from the sump and delivers it to the inlet of the main pump. Only a small quantity of oil is required to compensate for the leakage through the leak-off passage, and to assure an adequate inlet pressure for the main pump. Any excess oil pumped by the small pump returns to the sump through a low-pressure regulator.
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A check valve 1 assures that the inlet to the main pump is not subjected to pressure fluctuations that occur in the low-pressure reservoir. The system also includes a cooldown accumulator that, during normal operation, is fully charged with oilunder the same pressure as in the inlet to the main pump. When the engine stops running, the oil in both the high- and the lowpressure branches cools off and shrinks. As the system pressure drops, the accumulator discharges oil into the system, thus compensating for the shrinkage and preventing formation of pockets of oil vapor.
The high - pressure branch is fed from the accumulator through a check valve 2 that is installed in-parallel to the main pump. The low-pressure branch is fed through an orifice that is installed in-parallel to the check valve 1.
The orifice is small enough to prevent pressure wave propagation through it during each engine cycle, but sufficient to permit slow flow of oil from the accumulator to the reservoir. In some applications, the orifice can be incorporated directly in the check valve. After the oil in the system has cooled off, the accumulator maintains the system at above atmospheric pressure by continuously replenishing the oil that slowly leaks out through the leak-off passage.
When the engine is restarted, the accumulator is recharged again. If the engine is not restarted for a very long time, as it is the case when a vehicle is left in a long-term parking, the accumulator will eventually become fully discharged. In that case, the pressure in the accumulator drops to an unacceptable level, and a pressure sensor, that monitors the accumulator pressure, sends a signal to the engine control system which reactivates the electric pump for a short period of time to recharge the accumulator.
This process can be repeated many times, thus maintaining the system under a low level of pressure until the engine is restarted. After the engine restarts it takes less than one revolution of the main pump to restore the high pressure.
Operating the hydraulic system in a closed loop contributes to low energy consumption. The amount of hydraulic power consumed by the system is determined by the flow of fluid from the high- to the low-pressure reservoir times the pressure differential between the outlet from and the inlet to the high pressure pump. A small loss is also associated with leakage. There are good reasons to use high hydraulic pressure in the system, one of them being the need to maintain a high value of the bulk modulus of the oil.
In a closed-loop system the pressure in the low-pressure reservoir can also be quite high, although lower than in the high-pressure reservoir thus the pressure in the lowpressure rail is low only in relative terms. Hence, the system can operate with very high hydraulic pressure, and yet the energy consumption remains modest due to a relatively low pressure differential.
The ratio of high pressure to low pressure must be sufficiently higher than the ratios of the pressure areas above and below the valve piston to assure reliable engine valve closure. Advantages of camless engine Electrohydraulic camless valve train offers a continuously variable and independent control of all aspects of valve motion.
This is a significant. It brings about a system that allows independent scheduling of valve lift, valve open duration, and placement of the event in the engine cycle, thus creating an engine with a totally uncompromised operation.
Additionally, the ECV system is capable of controlling the valve velocity, perform selective valve deactivation, and vary the activation frequency. It also offers advantages in packaging. Freedom to optimize all parameters of valve motion for each engine operating condition without compromise is expected to result in better fuel economy, higher torque and power, improved idle stability, lower exhaust emissions and a number of other benefits and possibilities.
Camless engines have a number of advantages over conventional engines. In a conventional engine, the camshaft controls intake and exhaust valves. The cams always open and close the valves at the same precise moment in each cylinder s constantly repeated cycle of fuel-air intake, compression, combustion, and exhaust. They do so regardless of whether the engine is idling or spinning at maximum rpm.
As a result, engine designers can achieve optimum performance at only one speed.A Siemens ECU is used and two cable rails connect the actuators to it. A partially open ball valve state may also be able to be used to create more turbulence.
Rotating steel camshafts with precision-machined cams they push open the valves at the proper time and guide their closure, typically through an arrangement of pushrods, rocker arms, and other hardware. Closing the solenoid valve causes the plunger to pump the fluid through a check valve into the high pressure branch of the system. Crankshaft is the engine component from which the power is taken.
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