Piston work in a petrol engine
The first link in the chain of a piston combustion engine. Power transmission components. A dynamic power transmission The wall, it, How does a piston work in a petrol engine piston work together with the piston rings, must reliably seal the Combustion chamber and against the gas column Lubricant flow at each operating and loading position.
Especially the combustion can designed as an integral part Chamber that affects flow conditions across the piston crown. During the gas exchange, mixture formation, and combustion Various operating modes. Increase speed and brakes. How does a piston work in a petrol engine The mean effective pressure will maintained constant by supercharging Increases demand for mechanical and thermal loads Diesel engine piston capacity. However, the load increased.
There is a problem in fulfilling the requests
In modern piston design. Adaptation to changing operating conditions, anti-seizure, high structural strength, NVH performance, low oil consumption, and long service life. Additionally, there are limitations in some traditional applications The piston design and common materials became clear. How does a piston work in a petrol engine Therefore, every choice of material and structural design is essential. This should considered when designing a piston for high performance Diesel engine.
Temperature and load on piston
Converting fuel-based energy to heat very quickly Due to this the temperature and pressure increase significantly During combustion. Different work policies can require Different compression and air/fuel ratios. Thus, gases are the maximum temperature of the combustion chamber is between 1,800 and 2,6008C. During this period the temperature drops significantly
Combustion cycle, combustion gases
Room temperature may still be 500 to 1,0008C. Heat from the hot combustion gases can transferred primarily to the walls of the combustion chamber and thus to the piston crown by convection and only a small part by radiation. The temperature in the upper layer of the piston crown varies due to strong periodic fluctuations of temperature in the combustion chamber. their dimensions
The degree of fluctuation is about 10-408C
surface and decreases inward within a few millimeters according to an exponential function [8–70]. Most of the heat can absorbed by the piston crown. Refrigerant can released during the expansion stroke
from the piston ring area and cylinder wall. Depending on the Engine and piston design and effects Operating mode and piston speed, 20 to 60% Amount of heat accumulates in the piston crown. Released mainly by piston rings. A small part of Heat can converted into new gas during gas exchange.
Lubricating oil and cooling oil reaching the inner wall of the piston
Absorbs residual heat.
A three-dimensional temperature field it generated The piston can simulated with finite element programs using appropriate boundary values. How does a piston work in a petrol engine typical surface temperatures on a gasoline piston.
They can measured in a machine with non-electrical measuring methods (fusible plug, temp plug, and residual hardness) or sophisticated electrical measurement methods (thermocouples, NTC thermistors, and telemetry). Cooling (spray cooling and forced oil cooling) can affect
Piston temperature significantly
Gas, inertial, and auxiliary forces (connecting rod and side thrust) can balanced on the piston. Maximum Gas pressure is very important to the mechanics of the piston. tension In naturally aspirated diesel engines it is 80-110 bar 160-250 bar in supercharged diesel engines. Pressure Increases at a rate of 3-8 bar/8Ca and is greater than 20 bar/8Ca When combustion can interrupted [8-71-8-73].
Piston design and pressure
Main piston dimensions
The functional components of a piston include the piston crown, Piston top land, ring zone with piston pin boss and skirt. Additional functional elements such as cooling galleries And the ring carrier has a piston design. Piston The assembly includes the piston ring and the piston Pin and pin retention. How does a piston work in a petrol engine Major piston dimensions Main mechanical dimensions and closely related Dimensions of other components (crankcase, crankshaft). and connecting wire). Apart from the cylinder diameter,
The most important piston dimension is compression height,
That is the distance between the center of the pin and the top Piston top land edge. Piston mass plays an important role, Especially in high speed machines.
Loading conditions of piston
General details Gas, inertial and skirt side forces acting on the piston Creates a deflection in the piston and creates pressure. The pressure of the combustion gases acts on the piston crown. Piston pin and connecting rod. Since the piston pin boss The piston pin can supported in the skirt area The open end of the piston skirt deforms elliptically. Distortion can additionally affected by distortion Pin and through (ovalization and bending deflection). Contact forces in the cylinder, which also actuate the piston Twisting. Deformations caused by temperature field In piston deformations the piston can overloaded
As a result of mechanical forces. They form the crown Warping in piston at operating temperature and diameter Extend from the end of the lower skirt to the top end of the piston. The purpose of piston design is to take into account adequate wall thickness Prevent fractures and deformities even due to side effects However, in some areas the forces are sufficiently elastic
They are capable of withstanding the ravages of external use (like from a cylinder). Since the piston is moving faster The mass of the engine compartment should always can kept to a minimum. Deformations and stresses caused by operation Forces and temperature fields can simulated as finite Element pattern.
Piston crown mounting
Diesel piston crowns can subjected to extreme temperatures Loaded at temperatures above 3008C Fatigue strength of prestressed aluminum materials reduced significantly. The bowl rim should prevent local temperature peaks and weak peak effects from occurring to facilitate crack initiation [8-76–8-78]. Engine operation creates a significant heat cycle bowl rim. Local heating and distortion inhibition Piston materials can deteriorate due to cold surrounding areas Produce locally and, in extreme cases, heat cycles Fatigue.
Hard anodizing the piston crown makes it harder to produce A layer of aluminum oxide reduces its initial tendency Thermal cracking. Optimizing exhaust emissions for direct injection Engines often requires the design of combustion bowls With the minimum possible radius and mostly undercut. A pronounced temperature maximum inevitably arises the rim of the bowl. Aluminum oxide ceramic fiber incorporated.
Employer and support zone
The forces acting on the piston can transmitted through the piston pin hole to the piston pin and connecting rod to the crankshaft. The piston pin boss is one of the most stressed parts of the piston.
Various bore geometries (block, trapezoidal, or step support designs) can used to properly support the piston crown to transfer loads. Pin bore contact pressure can often reduced by step pin bosses (step connecting rods) in large diesel engines for rail and marine operations. The center holes that hold the piston pin are located in the boss support. Since the pin holes act as bearings, it must can machined with a high-quality finish
Loading the ring zone
Because their first (and sometimes their second) ring grooves are thermally and mechanically loaded, aluminum diesel engine pistons require additional measures to achieve the required service life. Radial movement of the ring due to the rocking motion of the piston in the cylinder is the primary cause of ring groove wear. How does a piston work in a petrol engine Axial movement and rotation of the rings as a result of gas, mass and frictional forces contribute to ring groove breakage.
On the one hand, the high thermal stress of the first ring groove particularly accelerates mechanical wear. On the other hand, it can cause ring groove coking and first ring sticking in diesel engines.
The thermal load of a piston can only increased to a certain extent because the fatigue strength of AlSi alloys decreases strongly can the temperature increases above about 1508C. Therefore, diesel engines require proper piston cooling in most cases [8-82]. Spraying oil from a steady jet to cool the piston interior (reducing the first ring groove temperature to 10-308C) is sufficient in many cases. A cooling gallery, an annular cavity behind the annular zone, can often required.
Car diesel engine piston
Depending on their process, diesel engines experience not only high heat but also high mechanical loads. Hypereutectic aluminum materials with 18% silicon content can only adequate for relatively lightly loaded car diesel engines. The ring carrier has established itself as a very effective protection against wear in the first groove in heavily loaded machines. Such pistons can usually made of eutectic Al alloy containing 11-13% silicon.
Cooling of the piston is essential in supercharged engines with high heat loads. This can take the form of oil spray cooling of the inner piston rim or forced oil cooling inside the piston with a cooling gallery.
In addition to conventional salt core cooling gallery pistons cast pistons with cooled ring carriers can used, creating a significant ability to reduce temperatures at critical component points. An effective reduction of 158C at the edge of the bowl doubles the service life.
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Locomotive, Stationary and Marine Diesel Engine Pistons
More stable operating conditions in power plants, marine propulsion, and rail car and locomotive engines previously allowed the use of aluminum full-skirt pistons in many cases.
The crown and ring zones in such pistons can robustly constructed and provide adequate cross-section for heat flow. Pistons with ring carriers and cooling coils or cooling galleries, cast iron or cast ring bands covering the forged piston body, and the ring carriers and cooling channels can joined by electron beam welding
It proved that the usefulness of light compounds in medium-speed engines running on heavy fuel had limitations. They do not adequately resist mechanical abrasion due to solid combustion residues on the Piston top surfaces.
The use of special alloys not used in other components for the piston during the development of the combustion engine so manifestation of the unusual demands that this component must meet. In fact, common piston materials form a compromise between a whole series of partially conflicting demands.
Aluminum silicon alloys (mainly eutectic) can widely used as materials for the manufacture of pistons High thermal conductivity, low density, good ductility and workability and good mechanical properties and high temperature strength are some of the properties of these light composites.