THE SYSTEMS OF FEEDING IN THE DIESEL ENGINES
THE SYSTEMS OF FEEDING IN THE DIESEL ENGINES
In the diesel engines the feeding is made separately introducing, inside the cylinders, the air that in the time of compression 600º C reaches, and the fuel that is injected to high pressure, which are mixed inside the combustion chamber, where the combustion of this mixture takes place.
Generally, in the induction manifold, there is no butterfly valve that regulates the amount of air in the admission.
By means of the accelerator pedal that it activates the bulk injection pump doses the amount of fuel that is injected in the third time, moment at which the mixture becomes inflamed, taking place work.
The factors that influence the combustion are the following ones:
or a good air filling.
or Good pulverization of the fuel.
or Good distribution of the fuel in the air.
or Control of the pressure.
or Burn time.
Systems of combustion
The first drops of diesel oil that enter the compression chamber where already find the compressed air and to high temperature, they take a time in beginning to burn itself, time necessary to acquire his temperature of combustion.
This time, call “retraso in the initiation of combustión”, it has been tried to reduce to the minimum by different procedures. On the one hand, pulverizing the most possible diesel oil, so that the particles have little volume in proportion to the surface that present/display to the air to receive the heat. On the other hand, to equip the air with a movement (turbulence) so that it crosses the diesel oil spurt in the injection and, therefore, is not the diesel oil the one that cools the air that surrounds to him.
These procedures are those that have made appear the different systems from combustion in the diesel engines.
In the diesel engine the form of the combustion chambers or the one of the head of the piston, is designed to favor the combustion, to improve therefore the yield and the power. In effect, two types of injection systems exist:
or direct Injection.
or indirect Injection.
Direct injection
The diesel oil is injected on the head of the piston (being the hottest part), to a pressure of 150 to 300 atmospheres, to obtain its pulverization. The air at the end of the compression has a pressure of about 40 bars or kg/cm2.
The turbulence of the air is obtained by the form of the head of the piston, in which it takes a toroidal concavity, or spherical that causes that the expansion is to regulate, improving the engine efficiency and in addition it causes that the fuel cannot be diluted in the lubrication oil nor be caused its draining in the cylinder.
The formation of the air eddy is facilitated sometimes by a baffle plate that takes in the admission valve, that orients the air towards the edges of the existing concavity in the head of the piston.
This system has two main advantages: to be economic in consumption of fuel, and easy starting, not needing spark plug heating to warm up the air generally. The small surface of the butt does not allow that much heat is radiated, obtaining itself a good starting. The compression ratio is low from 18 to 1. The combustion chamber is simple.
As inconvenient it is possible to be mentioned the noisiest being and to be required great pressure of injection, which implies a good system of injection, and as it uses an injector with orifices (0.2 mm of diameter), these are obstructed with relative facility.
Indirect injection
In this type of motor the injection is not made directly in the combustion chamber or the camera of the piston. Three types of indirect injection exist, that receive different denominations:
or System of pre-combustion chamber or antechamber
or System of vortex chamber or auxiliary combustion chamber or separated.
or System with camera of reserve of air or storage cell.
System of pre-combustion or antechamber
This system takes in the butt an antechamber that communicates with the one of combustion by very fine orifices (pulverizing).
The injector has a single orifice and ends at the pre-combustion chamber, that represents approximately 1/3 of the volume of the total camera. It must use start unit in cold, generally heating spark plug.
The compressed air lodges in the antechamber, where the diesel oil to a pressure of 80 to 120 atmospheres is injected. To the contact with the hot air and in movement, it initiates his combustion; the expansion of produced gases expels the rest from fuel without burning, through the sprayer, to the combustion chamber, where it finishes burning itself and it finalizes the phase of the cycle.
This system is less economic than the one of direct injection in diesel oil consumption. The starting is more difficult, because when existing more surface, the compressed air loses heat, being needed to facilitate the starting the use of incandescence spark plugs (Chaldean) and a mean-high compression ratio from 20 to 1.
As advantages present/display: smaller noise, minor injection pressure, to have injector of unique hole of difficult obstruction and minor wears away of the mechanical organs to have minor pressure in the combustion chamber.
System with vortex chamber, separated combustion or of auxiliary combustion chamber
This system avoids part of the disadvantages of the direct injection. The vortex chamber is lodged normally in the butt, although sometimes it is it in the block of the motor. It is a variant of the pre-combustion system.
In the vortex chamber all the accumulated air in the cylinder lodges almost during the admission. This camera communicates with the cylinder by an ample orifice and so that it prints to the air, when entering, a strong movement of eddy, favored by the a little concave form of the head of the piston.
The injection is made in the auxiliary combustion chamber or of turbulence where it is burned in his totality. The gases leave burning, happen violently to the cylinder (head of the piston). The strong produced detonation is left braking in the auxiliary combustion chamber and throughout the tube of communication with the cylinder, arriving very diminished at the top from the piston.
The vortex chamber approximately represents the 2/3 of the total volume of the camera and is located in a part noncooled (normally in the butt). The injector that is used is of needle or projection.
The advantages and disadvantages of this system are similar to the one of pre-combustion.
The advantages must a:
or the small pressure of injection (approximately 100 bars).
or the smaller consumption than in the system with pre-combustion chamber.
or the smooth march (little tendency to I strike or shaking).
The disadvantages are:
or a greater fuel consumption than in the systems of direct injection.
or To need a start unit in cold (generally preheating spark plugs).
or To need a high compression ratio.
System with reserve camera or air storage cell
The air is compressed in a storage cell that can be in the butt, or the head of the piston. As much in a case as in another one, one communicates by a narrow conduit, Venturi or diffuser. The diesel oil is injected in this narrowing, where its combustion begins. The heat produced in him, expands the air of the storage cell, increases its pressure. At the same time the piston descends and the pressure diminishes simultaneously in the cylinder, takes place in her a strong turbulence and therefore, a burnup.
Advantages:
or Minor injection pressure that in the previous cases.
or Loss pressure in the combustion chamber.
or the equipable consumption to the system of direct injection.
Disadvantages:
or Motor noisier than those of vortex chamber.
or Difficulty in the starting. They have preheating spark plug.
or upper middle Compression ratio from 20 to 1.
Circuit of air feeding
The air of the atmosphere introduces filtrate inside the cylinders properly. The admitted amount of air depends solely on the aspiration of the pistons.
The necessity to filter the air in these motors is the same one that in those of explosion. The air always takes in suspension dust; if that dust is introduced in the cylinders will act like emery on its walls, wearing away them, giving rise to a misalignment that would take with himself a loss of pressure in the compression and the passage of the diesel oil to the oil, diluting it and losing its viscosity. For the filtrate, a filter is placed in the admission pipe. The used filters are identical to those of the explosion motor, that studied in subject 8, being used three types of filter elements: dry filters, filters of metallic mesh and filters in oil bath.
The filters of oil bath are used in motors of great piston displacement, applied to trucks and buses.
The difference with the explosion motor resides in which the maintenance of these has to be more frequent.
Circuit of feeding of the fuel
This circuit has since mission to make arrive at the cylinder the amount of necessary fuel and in the right conditions of pressure for its good mixture with the air and later combustion.
In the diesel engine the fuel is taken from the deposit to the combustion chambers by two different circuits:
or Circuit of low pressure.
or Circuit of high pressure.
Circuit of low pressure
Description and operation
Call also circuit of feeding; he is the one in charge to send the fuel from the deposit to the creative device of the high pressure (inyectora pump), that is necessary to make the introduction and the pulverization of the fuel inside the combustion chamber.
The pressure sent from the booster pump to the inyectora pump is from 1 to 4 bars.
The circuit of low pressure is made up of the following elements:
To – Fuel tank
B – Filter (strainer)
C – Prefilter
D – Booster pump
And – Main filter
F – Spill valve of diesel oil
G – Pipe of filter pump
H – Pipe of bulk injection pump filter.
I – Leftover pipe of injectors.
J Tube of return
Fuel tank
The deposit has the same characteristics that the employees in the explosion motors and takes built-in:
or the filter strainer.
or an exit to the atmosphere by the cork or another system.
or Two canalizations, one for aspiration and another one for return.
or Well of movement.
or filling Cork.
or Elements of control for fuel level.
Booster pump
She is the one in charge to inhale the fuel of the deposit and to send it, through several filters, to the bulk injection pump. They are aspiring-propelling pumps that, inhale the diesel oil of the deposit through the prefilter and they send it to the bulk injection pump through the main filter. The feeding pressure must be included/understood between 1 and 4 kg/cm². They are generally of mechanical drive and we are going to see types both more using:
or membrane Pump: seemed to the gasoline pump.
or Pump of piston: used aspiring-propelling pump with some bulk injection pumps in line.
Membrane pump
They are equal to the employees in the gasoline motors, explained in subject 8. These pumps are self-regulating; the car-regulation obtains by balance of the pressure in the canalization of impulsion and the tension of the means of the membrane. It goes located on the motor and it receives the movement of an eccentric of the camshaft.
Pump of piston (0 and 11)
This type of pump is used in the case of linear bulk injection pump, and go placed in the body of the bulk injection pump, receiving the movement of an eccentric of the camshaft of the inyectora pump.
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It is a pump of simple effect, is car-adjustable.
Operation:
When the eccentric disappears, the piston, moves downwards by the action of the means. The camera increases and is aspiration in the deposit. In the camera the diesel oil is impelled towards the bulk injection pump. When the eccentric makes contact with enemy, she elevates the piston by means of the piston rod. The camera diminishes, the aspiration valve is closed, the impulsion valve is opened, and the diesel oil is trasvasado to the camera located underneath the piston.
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Fuel filtrate
The used diesel oil must be of dust particles or other matters clean, completely free. The necessity of it imposes the perfect adjustment of the injector and bulk injection pump, in which an inferior dust particle to 3 thousandth of millimeter can line some element or make difficult its operation. A small ray supposes a flight able to allow that the small amount escapes that supposes an injection, given the pressure to which is had to introduce in the compression chamber.
Another important part is to eliminate any rest of water that can take the diesel oil; otherwise its presence would oxidize and create failures in the pump.
The filtrate of the diesel oil becomes several times. In the first place it is made to the entrance of the pump of aspiration of the fuel and in the interior of the deposit (strainer); later it is made him happen through a prefilter from which it is sent to the main filter and of this one to the bulk injection pump.
Filter strainer
This filter strainer (to see), is placed in the interior of the deposit. It is a metallic mesh and it does not allow that they pass particles heavy.
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Prefilter
The prefilter is placed between the deposit and the booster pump or same pump.
It intends to store to the impurities and the water.
These prefilters of great filtrate capacity, are constituted by replaceable cartridges of screen or nylon.
In the 2 its positioning within the booster pump can be appreciated.
The filter mounts on the body that can be a metallic glass or of crystal, being subject by the screw and nut.
Main filter
The filters, depending on their positioning and its assembly, go placed between the booster pump and the bulk injection pump.
It has the mission to retain emulsionadas water particles in the diesel oil, as well as the smallest impurities.
Different types with different assemblies exist (simple or double).
They must have the following characteristics:
or To have great filtrate surface, being occupied a small volume.
or To be of effective filtrate.
or Lasting and of easy maintenance.
or To offer little resistance in the filtrate so that the fuel flow stays constant on the bulk injection pump.
Next some of the filters will study more using.
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or fuel Filter with felt plates
It is formed by felt plates through which it is commited to happen to the fuel, depositing in them its impurities. This filter can be washed with gasoline, although he is not advisable to do it more than two or three times.
or Filter Simms fuel
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or it is constituted by a paper of special cellulose, in form of accordion, coil to give greater filtrate surface him. The particles that the diesel oil takes are retained in the paper. They cannot be washed being necessary his substitution in terms that depend on the dirt of the used diesel oil and crossed kilometers. The cartridge is easily replaceable.
or Filter without body
In this filter the same cartridge does as well of container.
The filter canister is formed by a lamina battery of paper or filter weave, separated by fine alternate metallic washers, that maintain the lamina separated.
All this form a set mounted within a metallic cylinder.
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or
or Filter with double cartridge (fig.16 and 17)
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or
This type of filtrate forms two normal filters mounted one after the other and that form a single unit.
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or the assembly of the filters can be:
In parallel
In series
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or the most frequent assembly of both filters is in parallel, sharing the same cover has supported.
The operation is equal to the previous case, when leaving the first filter it happens to the second if it is in series, and if it is in parallel, to the entrance it derives the diesel oil for each one from the filters and when coming out they become to find to connect with the pipe that goes to the bulk injection pump.
It is possible separately to be placed two simple filters like the one of the 9.
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Circuit of high pressure
Description and operation
Call also circuit of injection. He is the one in charge to introduce, to pulverize and to distribute inside the combustion chamber a precise fuel load. The circuit of high pressure is made up of the following elements:
B – Bulk injection pump.
T – Tube of injection.
I – Injector.
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The injection system must like mission introduce, when finalizing the time of compression, a small amount of fuel in the compressed air, treating of which it is mixed with the greater amount of possible air and, therefore, very pulverized. This amount, small of by himself, has to be equal for all the cylinders and, nevertheless, variable in accordance with the exigencies of power at every moment; it has to be injected in a brief space of time, beginning therefore the principle of the combustion. In order to obtain that atomizaton that small amount to a great pressure must be injected.
The pressure of injection and the characteristics of the pulverization are in charge of the injector and its setting; the distribution in amount necessary to guarantee the good operation is assured by the bulk injection pump.
They are, also, the complementary organs of the pump the people in charge to cover the exigencies with the different conditions of use of the motor; that is to say, to assure the shutdown, the slow motion, the overload in the starting, etc.
The 1 shows to the different components from the circuit of high pressure and the corresponding ones to the circuit of low pressure.
The canalizations must have the same length to have times of injection such.
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Bulk injection pump
The bulk injection pump is the set in charge to provide the fuel in the precise amount, the necessary conditions and the moment adapted, according to the exigencies that are required of the motor at every moment.
The pump must inject the diesel oil to very high pressure, but in little very well dosed amount and, to burn 1g. of diesel oil 32 are necessary air g. for a good combustion. A liter of diesel oil needs approximately 13,000 liters air, (a 30% more than the gasoline).
Therefore the pump and its elements have to reunite a series of conditions:
or exact Metering of the amount of fuel to inject based on the engine power.
or Distribution of equal volumes for each cylinder.
or Injection at the suitable moment (injection order).
The bulk injection pumps can be of two types: and in line rotating. Although they have the same mission, his conception is different.
Linear pumps
At the present time and special, they are being used in the motors of great powers, whereas the rotating pumps, are being used in the light vehicles due to his smaller weight, size and minor mechanical complexity.
Vista the mission of the bulk injection pump, we see its description and operation.
The pump in line (fig 22) is constituted by so many elements of pump as cylinders have the motor.
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Each element of pump, is constituted fundamentally by: a bomb body, and its corresponding piston; piston that has two movements, one linear ascending action by the levy and another descendent action by the wharf. It has another tumbling by means of the rack. It has an own camshaft, that receives the movement of the crank by means of the gears of the distribution and turns to half of revolutions that the motor.
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The principle of the injection is based on the displacement of the piston caused by the control levy (camshaft of the bulk injection pump), at the precise moment.
The essential mission of the piston of the pump, is to elevate the pressure of the fuel of 4 bars until the pressure of injection within the main cylinder.
The amount of sent fuel depends on the drawee who is the piston, that is obtained by the action combined of the accelerating pedal and the speed governor on the rack.
Centrifugal Variador of advance to the injection
In a diesel engine the injection of the fuel begins before the piston has reached the top dead center at the end of the time of compression.
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In effect, the inflammation of the fuel does not begin until last a certain time, call “tiempo of ignition or delay to the initiation of combustión”, that it is the necessary time so that the fuel can take from the compressed air, the necessary temperature for the inflammation of the fuel.
So that the diesel engine works rationally, the advance to the injection must vary in direct reason of the regime; that is to say, of r.p.m.
The regulation can be controlled, normally, acting on the camshaft of the pump by means of a mechanical system of automatic action. Of this form they go ahead to the levies a certain angle with respect to the motor tree, this will have as result to advance the ascending movement of the pistons of the pumping elements.
This device goes mounted in the camshaft of the bulk injection pump, in the entrance of the originating movement of the organs of the distribution, alongside opposed of the speed governor.
Speed governor of the motor
The missions of this regulator are:
or To regulate the speed of rotation to the slow motion (minimum speed).
or To regulate the speed of Maxima rotation (terminal velocity).
They can be of two types:
or centrifugal Regulator of speed.
or Regulator by speed depression.
Centrifugal regulator of speed
Fig 25 represents the location of the centrifugal regulator, in the linear pump.
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Its operation is based on the action of the centrifugal force, that the movement of the camshaft (of the pump) produces in two counterbalances that take leaned. The movement of the counterbalances is transmitted independently to the rack, increasing or diminishing the volume of injection based on the revolutions of the motor and of the position of the accelerator.
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Regulator by speed depression
The previous regulator is used in great diesel engines and medium, in the small diesel engines a bulk injection pump with a regulator by depression is used.
Contrary to the habitual thing, is here an air butterfly sent by the accelerator in the air intake in the induction manifold.
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The accelerating one indirectly sends the rack by pneumatic route through the butterfly, the greater one or smaller opening causes the movement of the rack (depression Venturi system)
The regime between minim and Maxima speed is regulated in the butterfly of air intake by means of tops located on the body of the Venturi.
In the regulation by this system the state of the air cleaner has great influence.
It takes a handle for the shutdown of the motor.
Rotating pumps
These pumps very are used in the present motors for light vehicles due to their simplicity, watertightness, size and weight. It can be placed as much vertical as horizontally, making sure his autolubricación with the same diesel oil.
A slight existing overpressure in its interior does not allow the penetration of air, water or dust.
An only element of pumping is used to push and to distribute the fuel properly dosed to each one of the cylinders of the motor. They take, as in the case of the linear pumps, a regulator of advance to the automatic injection and a speed governor, that can be centrifugal or hydraulic engineer. His movement receives it, as it is explained in the linear pump, of the camshaft of the motor, or of a control system that turns, also, to half of returns that the crank.
The elements that independently compose the rotating pump of the used system of regulation are:
or Rotor of pumping and distributor: pistons and ring of levies.
or hydraulic Head.
or Pump of transference.
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or
or mechanical Regulator (box of the regulator and counterbalance) and hydraulic engineer.
or Systems of automatic advance.
or Valve pressure controller.
or dosificadora Valve.
Element of pumping
In the detail of the figure one is, of schematic and simple form the main pieces of the pumping element.
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When turning the rotor the fuel enters moderate pressure through an orifice the head and of another one the rotor, lowering by the central conduit towards the space between the pistons, forcing to these to separate. This is the admission piston stroke.
When continuing the rotation (detail of the figure), closes the entrance orifice. When the radial orifice of distribution in the rotor agrees with an orifice of exit in the mall pillow, the levies force the pistons to join themselves and the fuel is expelled towards one from the injectors. This is the injection piston stroke.
Principle of fuel distribution
The operation of the distribution rotor is demonstrated in the detail of the figure. The superior Vista shows the rotor in the admission position. The metering orifice agrees with one of the orifices of entrance in the rotor (six in this case), whereas the distributor does not agree with any of the orifices of unloading in the hydraulic mall pillow.
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To greater rotation of the rotor the relative positions change, until the injection point is reached. In this point no of the entrance orifices agrees with the orifice dispenser.
Adjustment of the maximum fuel (8 and 29)
The amount of injected fuel is controlled by the dosificadora valve and the effective race of pumping of the pistons. The adjustment of the maximum fuel is limited by the route of the tops of the rollers outwards.
Valve pressure controller
This valve is of the type of piston, is lodged in the plate of the end of the transference pump and carries out two missions.
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First it regulates the transference pressure, maintaining the wished relation between this pressure of transference and the speed of rotation. Secondly, it provides a filling of the pump and the purge avoiding air intake the conduits of the mall pillow.
Speed governor
or Regulator of counterbalance (mechanic)
The main characteristics of the pumping unit remain invariable, with the exception of the dosificadora valve. This one is of the revolving type in the regulator. The regulation obtains by means of counterbalances, that when going away separating, due to the centrifugal force, act on the dosificadora valve. The movement receives it from the axis of the pump.
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or hydraulic Regulation
The circuit differs solely from the previous one in which it talks about the speed control, that takes place taking advantage of the variation the pressure of transference based on the speed of the axis of the pump. The dosificadora valve is of the type of piston.
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Automatic advance
In some models it goes mounted an additional mechanism of control of automatic advance.
Action by the pressure porporcionada by the pump of transference to the fuel, advances to the point of injection when increasing the speed (r.p.m. of the motor).
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Dosificadora valve
It is driven by the accelerator, regulating the amount of fuel to inject in the cylinders.
Injector
It is the element through as the fuel in the combustion chamber is introduced. On him the pressure depends, pulverization, distribution and penetration in the air mass diesel oil.
They are like tubes that go spiral in the butt like the spark plugs in the explosion motor.
Types of injectors
All have the same principle of operation, but they differ by the form of the extremity of the needle, its seat and by the form of the spurt.
There are several types of injectors; the most used they are those of orifice and the one of ear or projection. Also there are others are special. They are different from others, to take one or several drills of entrance of fuel to the cylinder.
The 5 represent the section of an injector of several orifices in which the fuel, coming from the pump, arrives by the pipe until the inferior part of the needle. The pressure of the diesel oil raises to the needle and the piston rod of the injector compressing the wharf, leaving the fuel to pressure; as soon as the pressure coming from the pump stops, the soft one sends to the piston rod and the needle against the seat, closing the exit.
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The reference indicates the pipe of return of the fuel that can escape (for its lubrication) between and with its body.
Figures 36 and 37 show to the forms of a projection injector and another one of orifices, at the moment of the injection.
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The injectors of ear or projection have a conical needle of seat, that take a projection of diameter smaller than the exit orifice, causing the exit of the fuel in form of inclined spurt.
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Injector with strangling. The injection is made in two phases, one first pre-injection that the inflammation initiates, and the later injection of the rest of fuel. This causes that the combustion is smoother and the most flexible operation of the motor.
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Special injectors
They are used in the great diesel engines and special dispositions of the combustion chamber. They emphasize:
or Injector of orifice pilot
It consists of an injector of projection with great surface of covering, in whose nozzle it goes located auxiliary an orifice oblique that ends underneath the seat of the valve.
He is very useful for a good starting and effective feeding to low operating conditions.
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or
or Injector cooled by oil
It takes around the nozzle a refrigeration chamber around which diesel oil coming from the booster pump circulates. Employee in great motors that use appropriate fuels (heavy oils, such as fuel-oil).
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Overfeeding
The amount of air supporter of combustion available in each cycle determines the possible power of a diesel engine.
If to the motor we adapted a compressor to him, it allows to increase to the amount of air supporter of combustion him available and, therefore, it assures the increase of power until a 30%.
In order to introduce the additional air in the cylinders two methods are used:
or Positive displacement supercharger.
or Turbocompressor.
By positive displacement supercharger
This positive displacement supercharger is, in fact, a simple air compressor.
The positive displacement supercharger is moved by the own motor and compresses the air, elevating the pressure, reason why the moment for opening the admission valve air highly compressed (1’5-2 will enter the cylinder atmospheres) and greater amount of air in a same volume (until a 50 percent more) of piston displacement will be admitted.
It is possible to make emphasize that, to total engine power, these compressors absorb a part very important of the engine power.
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Positive displacement supercharger Roots
He is comparable to a pump of gears: it has two revolving elements (To and B) with two projections. These “lóbulos” actions by means of gears do not make contact with enemy with others and the comfort must be reduced possible.
They simultaneously present/display the advantage of which these motors with positive displacement supercharger are very smooth and progressive that powerful.
By turbocompressor
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This set is the suitable solution for the diesel engines when obtaining in these its greater benefits.
The turbocompressor name, comes from which this element is a turbine located in the exhaust manifold, turbine that is together with by its axis a compressor located in the induction manifold. This form the energy of exhaust gases takes advantage of, without having to reduce power, as in the case of the positive displacement supercharger.
When the motor works, it emits certain amount of burned gases that high temperature and pressure are to.
This exhaust gases flow drives the turbine wheel.
The movement of the turbine is communicated directly to the wheel of compressor C by means of its axis of connection.
The compressor feeds this way the motor with air to pressure through the admission valve.
The interchanger or intercooler is a radiator cooled by outer air, or water of refrigeration of the motor.
It is placed between the compressor and the induction manifold. The air interchanger has the mission approximately to reduce to the temperature of compressed air 50ºC or 60ºC. Of this form it allows:
or To improve a little the filling, when increasing the density of the air.
or To improve the mechanical behavior of the motor, when diminishing the detonation risk.
or To increase the compression ratio, that is favorable for the use to zone charges.
The system also can take a spill valve to limit the Maxima pressure provided by I disturb. It goes when coming out placed of the escape before the turbine and is driven by presió of admission gases.
The advantages of the overfeeding with I disturb and with compressor they are:
or Greater yield and benefits.
or Minor consumption of fuel to power equality.
or Possibility of reducing the compression ratio and of increasing the life of the motor.
or Greater benefits.
At the moment the “turbos calls of geometry exist variable”, in which the passage of exhaust gases to the turbine is regulated. To low revolutions of the motor the effect is increased of these exhaust gases on I disturb, activating its operation before, and, avoiding therefore “retraso” or time that takes I disturb in entering.
Common rail or system of injection of common pipe
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It is a system of diesel injection of last generation, in which, by means of a mechanical pump the fuel is provided to the injectors to a pressure of about a 1500 Kp/cm2 (atm), through an feeding incline. The injection control takes place electronically through an Electronic Unit of Control (UCE).
The injectors work like electroválvulas. They are electronic, very similar to the employees in gasoline injection. The opening is regulated by means of an electromagnet, that receives current of the UCE. They are fed on an incline (conduit or deposit) common, call “Common Rail”, where the diesel oil is to a very high pressure (1400-1500 atm).
The pump of high pressure is mechanical, driven by the motor, and it is in charge to provide to the incline the fuel to that high pressure, by means of a regulator stays in constant values.
The functions of distribution, amount to inject and order of injection, are controlled with a UCE: Several sensors inform it based on the load into the motor (position of the accelerator pedal), RPM and amount of air. It evaluates the gathered data and it determines the electrical impulse that it sends the opening of the corresponding injector, in the suitable cylinder (injection order).
One is a direct, multipoint and discontinuous injection. All the injectors work to the same pressure, independent of the number of r.p.m.
Main advantages:
or Increase of the engine efficiency.
or Reduction of noises and smoke.
or Minor fuel consumption.
Diesel engine start-up
The engine start-up diesel is one of the great disadvantages of these motors with respect to those of explosion.
Because the inflammation of the mixture takes place by pre-ignition by means of the elevation of temperature and pressure when the starting takes place, specially in cold time, the air and the walls of the cylinder are to low temperature, reason why the temperature reached at the end of the compression is not sufficient to inflame the fuel.
The procedures that are used to obtain that preheating of the air are: spark plugs of incandescence, heating in the induction manifold or introducing a small amount of a very inflammable liquid.
Spark plug of incandescence or heating
They are electrical resistance that warm up the air of the cameras to facilitate the inflammation of the gasohol when starting in cold.
It takes an electronic system that determines the necessary time of preheating according to the temperature of the motor.
The spark plugs are located in the center of the cameras, more or less, in the axis of the injectors.
They are possible to be connected in series or parallel, although for security reasons, they are connected of two in two.
It is driven by means of the starter switch and the time that lasts ignition the witness of the picture, receiving the tension of the battery and when this it is extinguished it is the moment for driving the starter engine.
Heating in the admission gallery
The incandescence spark plug has the disadvantage of being put under, constantly, to the heat, turbulences and pressures of the combustion, reason why its resistance fails with certain frequency. In order to save this problem one resorts to warm up the air before entering the cylinder. For it electrical resistance are used, installed in the admission gallery, that are put incandescent when doing to pass through them an electrical current coming from the battery.
Incendiary fuel
Ether is used, and consists generally of depositing a small amount of this liquid in the entrance of the induction manifold. Of this form the inhaled air, steam load of this liquid, becoming inflamed with facility, still with little heat that takes place in the first compressions.