diesel oilThe engine is an engine that burns diesel to obtain energy release.It is made by GermanyinventorRudolph·diesel (Rudolf Diesel) in 1892,diesel oilIt is expressed by his surname Diesel, and the diesel engine is also called Diesel engine.
The advantages of diesel engine are large torque and good economic performance.The working process of diesel engine andgasoline engineThere are many similarities. Each working cycle also experiences air intakecompressFour strokes of power and exhaust.But becauseDiesel engineThe fuel used is diesel, and its viscosity ratiogasolineLarge, not easy to evaporate, but its autoignition temperature is higher thangasolineLow, therefore, the formation and ignition mode of combustible mixture are similar togasoline engineDifferent.The main differences are:CylinderThe mixture in is compression ignition rather than ignition.diesel oilengineDuring operationatmosphere, when the air in the cylinder is compressed to the end point,temperatureIt can reach 500-700 ℃, and the pressure can reach 40-50Atmospheric pressure。pistonNear TDC,Oil supply systemOfFuel injection nozzleInject fuel into the cylinder combustion chamber at extremely high pressure in a very short time,diesel oilForm subtleOil particle, mixed with high pressure and high temperature air, the combustible mixture burns by itself and expands violentlyExplosive power, promotepistonDownward work, when the temperature can reach 1900-2000 ℃ and the pressure can reach 60-100 atmospheres, the torque generated is very large, so diesel engines are widely used in large diesel enginesequipmentOn.
Features of traditional diesel engines:thermal efficiencyGood economy, diesel engine adoptscompressed airTo improveair temperature Make the air temperature exceed the autoignition point of diesel oil, and then inject diesel oil, diesel spray and air, and ignite and burn by itself.Therefore, diesel engines do not needignition system。At the same time, the diesel engineOil supply systemIt is also relatively simple, soDiesel engineIts reliability is better than that of gasoline engine.Due to the freedom from deflagration and the need for diesel spontaneous combustionCompression ratioVery high.The thermal efficiency and economy are better than those of gasoline engines. At the same time, under the same powertorqueLarge, low speed at maximum power, suitable fortruckUse of.
But the diesel engine workspressureLarge, all relevant parts are required to have high structural strength and stiffness, so the diesel engine is bulky and bulky;DieselFuel injection pumpThe manufacturing precision of the nozzle is high, so the cost is high;In addition, the diesel engine works rough and has large vibration and noise;Diesel is not easy to evaporate, and it is difficult to start when the car is cold in winter.Because of the above characteristics, diesel engines were generally used on large and medium-sized trucks in the past.Traditionally, diesel engines have been rarely favored by cars because of their bulkiness, lower power index than gasoline engines (lower speed), higher noise and vibration, and more serious soot and particle (PM) emissions.Especially with the new development of small high-speed diesel engines, a number of advanced technologies, such as electronically controlled direct injection, common rail, turbocharging, intercooling and other technologies, have been applied to small diesel engines, which has solved the shortcomings of the original diesel engines. However, the advantages of diesel engines in terms of energy saving and CO2 emissions,All thermal engines, including gasoline engines, cannot be replaced as "green engines".
inventor
Rudolf Diesel（
Diesel is expressed in English as Diesel, which is in memory of the inventor of diesel engine -Rudolf Diesel （RudolfDiesel）。[1]
Diesel was born in 1858 in Germany and graduated fromMunich University of Technology。In 1879, he graduated from Diesel University and became a refrigeration engineer.In his work, Diesel felt that the efficiency of the steam engine at that time was extremely low, and he had the idea of designing a new engine.After saving some money, Diesel resigned from his position as a refrigeration engineer and opened an engine laboratory by himself.
in the light ofsteam engineLow efficiency weakness, Diesel focuses on developing efficientinternal-combustion engine。At the end of the 19th century, petroleum products were extremely rare in Europe, so Diesel decided to use vegetable oil to solve the fuel problem of machines (peanut oil was his experiment).Because the ignition performance of vegetable oil is poor, the structure of Otto internal combustion engine cannot be applied.Diesel decided to start a new career, improve the compression ratio of the internal combustion engine, and use the high temperature and pressure generated by compression to ignite the oil.Later, this compression ignition engine cycle was calledDiesel cycle。
Like all greatinventorSimilarly, the way forward for Diesel was full of difficulties.Experiments have proved that vegetable oil is unstable in combustion and too expensive to bear the "heavy responsibility" of Diesel.Fortunately, petroleum products were gradually popularized in Europe at that time. Diesel, a heavy distillate fuel originally used for heating, was chosen as the fuel of the machine.The structural strength of compression ignition engine is always a difficult problem.In one experiment, the parts on the cylinder flew around like fragments of shells, almost causing casualties.The experiment did not go well, and Diesel's funds were gradually exhausted.He had to return to the refrigerator factory to make a living.But Diesel did not give in to difficulties. He continued to experiment in his spare time to improve his machine step by step.
In 1892, Diesel finally developed a practical diesel powered compression ignition engine.suchengineHigh torque, low fuel consumption, and the use of low-quality fuel show a brilliant development prospect.Diesel immediately put himself into the business venture of diesel engine production.Unfortunately, as a good engineer, Diesel lacks business acumen.He is getting into trouble financially.In 1913, Diesel was on the verge of bankruptcy.But diesel engine invented by Diessera shipAnd the whole industrial field is getting more and more extensive development.
In 1976, VolkswagenGolf carDiesel engine is adopted on the platform;
1989, VolkswagengolfThe diesel vehicle won the title of "low emission vehicle".In the same year, Volkswagen obtained some technology from Fiat's research and development organization, and produced the first 5-cylinder engine R5 TDI with supercharging and direct injection technology, which was put on trial on Audi 100 model.
In 1990, German Volkswagen officially launched a turbocharged, direct injection series of diesel engine TDI. Since then, German Volkswagen has been leading the world in the development and application of diesel power technology;
In 1993, developed 4-cylinder turbocharged direct injection diesel engine (TDI);
In 1995, developed the naturally aspirated direct injection (SDI) diesel engine;
In 1995, variable cross-section was developedTurbochargerVGT；
In 1998, the pump D ü se technology was developed;
In 1999, it developed diesel power of Lubo car with a fuel consumption of 3 liters per hundred kilometers.The production of an upgraded diesel powered car createdFuel consumption per hundred kilometersThe record of 0.99 liters is the highest in the worldFuel economyA car.The engine is aluminum naturally aspiratedSingle cylinder diesel engine, adopting advanced high-pressure direct injection technology,displacement0.3L;
In 2002, FAW Volkswagen took the lead in launching Jetta SDIChinese market；
In 2004, FAW-VW introduced TDI technology.
Development prospect
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Diesel Engine Industry Chain Diagram
Diesel engines are widely used and are at the core of the industry chain.In the past ten years of development, the diesel engine production industry has formed a series of supporting enterprises. Many diesel engine enterprises have played more roles as the general assembly contractor, while some key parts of the diesel engine: crank connecting rodpiston、Cylinder linerCams have been produced by professional companies.Specialized division of labor enables diesel engine manufacturers to focus more on their own advantages and focus on the design and manufacturing of diesel engines.
Diesel engines are mainly used for final supporting products, such as high-power high-speed diesel engines mainly supporting heavy vehicles, large buses, engineering machinery, ships, generator sets, etc.Therefore, the development of the diesel engine industry depends to a large extent on the market conditions of related end products.
In the field of agricultural diesel engines, the market growth of developing countries will make up for the market decline of developed countries. The rapid growth of the global population and the upgrading of old equipment have a greater demand for agricultural machinery. The global agricultural diesel engine market will show a rapid growth.In the field of aero engines, the engine industry is the core fine molecule industry of the aviation industry, with a very broad prospect for future development.Based on the above analysis of various fields, we believe that the global diesel engine will maintain a steady development rate of 8%.
working principle
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The working process of diesel engine is the same as that of gasoline engine. Each working cycle also experiences intakecompressFour strokes of power and exhaust.
The diesel engine draws pure air in the intake stroke.When the compression stroke is near the end, the diesel oil pressure is increased to more than 10MPa by the injection pump, injected into the cylinder through the injector, and mixed with the compressed high-temperature air in a very short time to form a combustible mixture.As the compression ratio of diesel engine is high (generally 16-22), the air pressure in the cylinder at the end of compression can reach 3.5-4.5MPa, and the temperature can reach 750-1000K (while the mixture pressure of gasoline engine at this time will be 0.6-1.2MPa, and the temperature can reach 600-700K), which is much higher than that of diesel engineAutoignition temperature。Therefore, after diesel fuel is injected into the cylinder, it will ignite immediately after mixing with air in a short time.The air pressure in the cylinder rises rapidly to 6-9MPa, and the temperature also rises to 2000-2500K.Driven by high-pressure gas, the piston moves downward and drivescrankshaftWork by rotating,waste gasIt is also discharged into the atmosphere through the exhaust pipe.
The fuel supply system of ordinary diesel engine is composed ofCamshaftDrive and deliver diesel oil to the fuel chamber of each cylinder by means of high-pressure oil pump.suchOil supply modeTo change with the engine speed, it is impossible to achieve the optimal fuel supply at various speeds.
The common rail injection fuel supply system consists of high-pressure fuel pump, common fuel supply pipe, fuel injectorElectronic control unit(ECU) and somePipeline pressure sensorEach injector in the system is connected to the common fuel supply pipe through its own high-pressure fuel pipe, which plays a hydraulic pressure storage role for the injector.During operation, the high-pressure fuel pump delivers fuel to the common fuel supply pipe at high pressure, and the high-pressure fuel pump, pressure sensor and ECU form a closed loop to control the oil pressure in the common fuel supply pipe accurately, completely changing the phenomenon that the fuel supply pressure changes with the engine speed.Its main characteristics are as follows:
1. The injection timing and fuel metering are completely separated, and the injection pressure and injection process are timely controlled by ECU;
2. The injection pressure, injection starting point and duration of each cylinder can be adjusted according to the working condition of the engine, so as to pursue the optimal control point of fuel injection;
3. It can realize high injection pressure and pre injection of diesel.
Crank connecting rod mechanism of diesel engine
Working conditions: when the diesel engine is working, the internal crank connecting rod mechanism is directly in contact with the high-temperature and high-pressure gas, the rotation speed of the crankshaft is very high, the linear speed of the reciprocating movement of the piston is quite large, and it is also in contact with the combustible mixture and combustion exhaust gas. The crank connecting rod mechanism is also subject to chemical corrosion, and lubrication is difficult.It can be seen that the working conditions of the crank connecting rod mechanism are quite bad, and it must withstand high temperature, high pressure, high speed and chemical corrosion.
Composition: The main parts of the crank connecting rod mechanism can be divided into three groups: the body group, the piston connecting rod group and the crankshaft flywheel group.
Function: Crank connecting rod mechanism isDiesel engineThe transmission mechanism that realizes the work cycle and completes the energy conversion is used to transmit force and change the motion mode.In operation, the crank connecting rod mechanism converts the reciprocating motion of the piston into the rotary motion of the crankshaft in the power stroke, and outputs power to the outside. In the other three strokes, namely the intake, compression, and exhaust strokes, it converts the rotary motion of the crankshaft into the reciprocating linear motion of the piston.Generally speaking, the crank connecting rod mechanism is the mechanism by which the engine generates and transmits power.Through it, the heat energy generated by fuel combustion is converted into mechanical energy.
load characteristic
The load of diesel engine usually refers to the magnitude of diesel engine resistance torque.Since the average effective pressure is proportional to the torque, the average effective pressure is often used to represent the load.The working condition of diesel engine is determined by the speed and load together.The so-called load characteristic refers to the relationship between other main performance parameters (fuel consumption rate ge, fuel consumption Gf, exhaust temperature tr, etc.) and load when the speed of the diesel engine is constant.At this time, since the speed is constant, the effective power can be used to measure the load.In the process of engine debugging, load characteristics are often used as the standard for performance comparison.In addition, the load characteristic gives the relationship between the engine load and fuel consumption rate under the condition of constant speed, so it has special significance for fixed engines (such as engines for generator sets) whose load can be changed in a large range and whose speed is basically unchanged.If a series of load characteristic curves at different speeds are measured from the engine, the most economical operating conditions of fixed or transport engines can be selected.During the operation of the diesel engine, the charge volume does not change much. The main reason is to change the mixture concentration (i.e. excess air coefficient) by changing the fuel supply volume per cycle, so as to adjust the load of the diesel engine (called quality control). In other words, the diesel engine changes the load mainly by changing the position of the fuel injection pump regulating rod and increasing or decreasing the fuel supply volume.The figure shows the general law of some parameters changing with the load when the diesel engine operates according to the load characteristics.Increasing the load of diesel engine means increasing the fuel supply per cycle, so the fuel consumption Gf increases with the increase of load, while the excess air coefficient a decreases with the increase of load;More fuel supply and more heat release make the exhaust temperature tr increase with the increase of load.When the load is empty, Ne=0, Pi=Pm, then m=0, so ge is infinite.With the increase of load, m increases rapidly, while ge decreases.When the load increases to point A, ge reaches the minimum value.Then continue to increase the load, because the excess air coefficient a decreases, the mixture formation and combustion deteriorate, and ge increases instead.The exhaust smoke increases with the increase of load, but it increases slowly at low load, and the smoke is very small at low load, which is invisible to the naked eye, and is generally considered as smoke-free exhaust.At high load, smoke density increases rapidly.When approaching the maximum power, due to the decrease of a, the mixture formation and combustion worsen, the combustion is incomplete, and the exhaust smoke increases sharply (point B in the figure). At this time, the fuel consumption rate ge also increases rapidly.The heat load of piston, cylinder head and other parts also increases rapidly.If the fuel supply continues to increase, the diesel engine will emit a lot of black smoke, and the power will decrease instead, so there is a smoke limit for the diesel engine.In order to ensure the safe and reliable operation of the diesel engine, it is not allowed to work under the smoke limit.
sensor
Delphi of the United States announced that it has developedengine oilDiesel engine oil sensor for status.The sensor determines the oil change time by detecting the state of the oil, which can significantly extend the time of oil change andfilterTime interval for.In addition to measuring the original viscosity and permittivity, the new sensor also measures the soot content and the dilution of fuel to engine oil, so as to detect the state of engine oil more accurately.It will start mass production for truck manufacturers in 2009.
Due to diesel engineengineControl the increase in the use of multiple rear jets, viaPiston ringThe amount of fuel added to dilute the engine oil is increasing, which is easy to reduce the lubricity and viscosity of the engine oil.In addition, the amount of soot mixed into the engine oil through EGR (exhaust gas recirculation) increases, leading to the reduction of additive effect and the increase of engine oil viscosity.Because only viscosity is measured, it is easy to be affected by these two opposite factors, and it is difficult to accurately grasp the deterioration degree of oil.
The dilution of fuel to engine oil can be measured by the improved viscosity measurement system according to the convection time.On the other hand, the content of soot can be calculated from the detected dielectric change.The sensor can measure the oil temperature and oil volume, and is supposed to be installed on the machinetankOn the bottom shell or engine body, the shape is designed as small size.
The sensor can be used not only for commercial truck diesel engines, but also for light vehicle diesel engines such as large SUVs and pickups, as well as industrial diesel engines.
difference
In gasoline engines, gasoline is injected into the intake pipe and mixed with air to form a combustible mixture, which then enters the cylinder, ignites, burns, expands and works through the spark plug.People usually call itPositive ignition engine。The diesel engine generally injects diesel oil directly into the engine cylinder through the fuel injection pump and nozzle, and evenly mixes with the compressed air in the cylinder, which ignites spontaneously under high temperature and pressure to push the piston to do work.People usually call this kind of engineCompression ignition engine。
gasoline engine
Gasoline engine vehicles have the characteristics of high speed (the speed of gasoline engine for cars can reach 5000-6000 rpm, and that of gasoline engine for trucks can reach about 4000 rpm), light weight, low noise during operation, easy starting, low manufacturing and maintenance costs, so they are widely used in cars, medium and small trucks, and military crossover vehicles.The disadvantage is that the fuel consumption is high, so the fuel economy is poor.Due to the high compression ratio, the fuel consumption of diesel engine vehicles is about 30% lower than that of gasoline engine vehicles on average, so the fuel economy is good.The 1.7L diesel car can save 2L of fuel per 100km compared with the 1.6L gasoline car.Generally, most trucks use diesel engines.The weakness of diesel engine is that its speed is lower than that of gasoline engine (generally the highest speed is about 2500-3000 rpm), its quality is high, and its manufacturing and maintenance costs are high (because the fuel injection pump andFuel injectorHigh machining precision is required).Its application scope is expanding to medium and light trucks.Foreign diesel cars have also developed rapidly, with the maximum speed of 5000 rpm.
America and Diesel Engine
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Diesel engines not only lead gasoline engines in CO2 emissions, but also will have less sulfur in fuel than gasoline engines in the near future.For a long time, automobile exhaust has been considered as one of the important reasons for the greenhouse effect.The United States and China are considered to be the two countries with the largest CO2 emissions.
According to a survey, nearly half of the new cars in the European car market in 2004 used new green diesel engines.However, only 1% of the cars driving on American roads use diesel engines.The reason is simple: American consumers have the lowest gasoline price in the world.But now the gasoline price in the American domestic market is close to the highest level in the same period of history, which makes American consumers have to pay attention to those economical cars that can save them money.
Two years ago, only two cars in the American car market used diesel engines.Today, with the rising price of gasoline, 13 diesel cars have appeared in the American car market, and by 2006, 6 new cars will be on the market.By then, there will be nearly 20 types of vehicles using diesel engines.
President Bush's signing of the document on diesel engines points out the way forward for diesel vehicles in the future.American policy makers and consumers have found that diesel cars are a good choice.Diesel is also a good choice for China.Under the condition of market mechanism, vehicles with diesel engines will have a broader prospect.[2]
Europe and Diesel
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Europe is the birthplace of diesel engine technology. Due to the many characteristics of diesel, since the mid-1990s, major European automobile companies have vigorously developed diesel engine technology and gradually promoted it to consumers. More than two-thirds of cars use diesel engines.Mercedes Benz, Volkswagenbmw、renault, Volvo and other European famous brands have diesel engine models.
Cummins diesel engine
Volkswagen, Germany: TDI diesel technology was first developed by Fiat, Italy, and later acquired and developed by Volkswagen.
BMW: D technology, characterized by high power and torque, and the use of dual turbo variable cross-section turbocharging technology.
Mercedes Benz: CDI technology
The logo of Citroen: HDI technology is the same as Volkswagen in Germany and also comes from Fiat in Italy.
Renault: DCI technology, whose reliability was questioned before 2006 because the turbocharged turbine was fragile, was subsequently improved by Renault.
Fiat: JTD technology
Opel: TDCI technology, compared with Volkswagen's TDI technology.
new technique
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Exhaust after treatment system with diesel particulate filter
Many people have a bad impression of diesel engines because of their bulkiness, loud noise and black smoke. After years of research and application of new technologies, the current situation of modern diesel engines is beyond comparison with the past.Modern diesel engines generally adopt electronic control injection, common railturbineSupercharging and intercooling technologies have made major breakthroughs in weight, noise and smoke, reaching the level of gasoline engines.
Electronic control injection technology
In terms of electronic control injection, the main difference between diesel engine and gasoline engine is that the electronic control injection system of gasoline engine only controls the air-fuel ratio (the ratio of gasoline to air), while the electronic control injection system of diesel engine regulates the load by controlling the injection time.
Electronic control injection system of diesel engineIt consists of sensor, ECU (control unit) and actuator.Its task is to electronically control the fuel injection system, so as to realize the operation of fuel injection quantity and timingworking conditionReal time control of.Speed, temperature, pressure and other sensors are used to synchronously input the real-time measured parameters into the computer, compare them with the parameters stored in the ECU, control the actuator according to the optimal value after processing and calculation, drive the fuel injection system, and make the diesel engine operate in the optimal state.
In order to make the load regulation more accurateCommon rail technology。The turbocharger of diesel engine has been introduced.as forSupercharged intercooling technologyThat is, when the turbocharger willfresh airThe compression is cooled by the middle cooler, and then flows to the cylinder through the intake manifold and intake valvecombustion chamber。The effective intercooling technology can reduce the pressurization temperature to below 50 ℃, which helps to reduce exhaust emissions and improve fuel economy.
Common rail technology
Common rail system
In the automotive diesel engine, the time of the diesel injection process is only a few thousandths of a second due to the high-speed operation. The experiment proves that the pressure of the high-pressure fuel pipe varies with the time and position during the injection process.Due to the compressibility of diesel fuel and the pressure fluctuation of diesel fuel in the high-pressure fuel pipe, the actual fuel injection state is quite different from the plunger fuel injection rule specified by the fuel injection pump.The pressure fluctuation in the fuel pipe sometimes causes the pressure in the high-pressure fuel pipe to rise again after the main injection, reaching the pressure that makes the needle valve of the fuel injector open, and reopening the closed needle valve will cause the secondary fuel injection phenomenon. Because the secondary fuel injection cannot be completely burned, the smoke and hydrocarbon (HC) emissions will increase,oil consumptionIncrease.In addition, the residual pressure in the high-pressure oil pipe will change after each injection cycle, which will cause unstable injection, especially at low speedregionThe above phenomenon is easy to occur. In serious cases, not only the fuel injection is uneven, but also intermittent non injection will occur.In order to solve the defect of fuel pressure change in diesel engines, modern diesel engines adopt a technology called "common rail".Common rail technology refers to a fuel supply method that completely separates the generation of injection pressure and the injection process from each other in a closed-loop system composed of a high-pressure fuel pump, a pressure sensor and an ECU. The high-pressure fuel pump delivers high-pressure fuel to the common fuel supply pipe, and precisely controls the oil pressure in the common fuel supply pipe, making the pressure of the high-pressure fuel pipe independent of the engine speed,It can greatly reduce the change of fuel supply pressure with engine speed, thus reducing the defects of traditional diesel engines.The ECU controls the fuel injection quantity of the fuel injector. The fuel injection quantity depends on the pressure of the fuel rail (common fuel supply pipe) and the opening time of the solenoid valve.[3]
maintain
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In order to extend the service life of diesel engines, the air filter should be strengthened during the useLubricating oilFilters andFuel filterThe maintenance of these three filters will give full play to their functions.
During the installation of the air filter, it is not allowed to omit to install, reverse to install, or install each sealing washer and rubber connecting pipe by mistake, and ensure the tightness of each embedded position.The paper dust cup air filter used should be cleaned once every 50-100 hours of operation. The surface dust can be brushed off with a soft bristle brush. If the working time exceeds 500 hours or it has been damaged, it should be replaced in time.When using oil bath air filter, clean it with clean diesel oil every 100-200 hoursfilter elementAnd replace the lubricating oil in it. If the filter element is broken, it needs to be replaced immediately, and pay attention to adding lubricating oil as required during use.
If the lubricating oil filter is not maintained in time during the use of the diesel engine, the filter element will be blocked, the lubricating oil pressure will increase, the safety valve will open, and the lubricating oil will flow directly into the main oil passage, which will aggravate the wear of the lubricating surface and affect the service life of the diesel engine.Therefore, the lubricating oil filter should be cleaned once every 180-200 hours of operation. If it is damaged, it should be replaced immediately to prevent impurities from entering the lubricating surface.The diesel engine should be cleaned when it is used in different seasonsCrankcaseAnd each lubricating surface by mixing lubricating oil, kerosene and diesel oil as washing oil. After the lubricating oil is drained, add washing oil for cleaning. Then, run the diesel engine at low speed for 3-5 minutes, drain the washing oil, and add new lubricating oil.
All kinds of fuel filters in the fuel supply system should be cleaned or replaced once every 100-200 hours of operation, and the fuel tank and all oil pipelines should be thoroughly cleaned.Especially for electronic controlCommon rail system, due to high pressure precise injection,fuel system The high precision of the coupling parts and small fitting clearance put forward higher requirements for the filtering efficiency and water separation efficiency of the fuel filter.class aOil water separator, Level IDiesel fine filterThe water separation efficiency is required to be greater than 95%, and the particle filtration efficiency of 3-5 microns is required to be greater than 98.6%.Such as BOSCH, Luber Finder, Fleetguard, Mann Hummel, Parker, etc., and DIFITE in China.During daily maintenance, special care shall be taken. If any abnormality is found, or the driving mileage and time meet the requirements of the engine, it shall be replaced in time.When changing oil in seasonal transition, all parts of the entire fuel supply system shall be cleaned.The diesel used shall meet the seasonal requirements and undergo 48 hours of precipitation purification treatment.
Treatment of black smoke
The equipment using the diesel engine as the engine system will emit wisps of black smoke in the process of operation, which will not only cause the operator's surrounding environment to be polluted, but also cause serious harm to the environment. Therefore, solving the problem of black smoke from the diesel engine is not only a vexation for the operator, but also a headache for the industry.Now let professionals explain some relevant knowledge to you.
First of all, it can be confirmed that the main cause of diesel engine black smoke is incomplete fuel conversion. In addition to the structural design of the equipment itself, it may also be caused by some details that the operator did not pay attention to.The main solutions are as follows:
1： The fuel tank of the diesel engine is not sealed and has been in contact with the air for a long time, which causes some suspended impurities and dust in the air to fall into the air filter and cause the air inlet to be blocked, resulting in insufficient air supply for internal combustion and incomplete combustion. Therefore, it is recommended that the fuel tank should be cleaned frequently in a harsh environment,In an environment with good air, the air filter can be cleaned at intervals and replaced regularly.
2： It may also be that the fuel quality is poor, which causes the blockage of the oil pipe passage inside the oil tank, which causes insufficient oil supply. The best solution is to replace the solenoid valve.If the fuel quality is poor, the fuel filter may also be damaged. The internal oil may deteriorate, causing black smoke. In serious cases, the fuel system may also be damaged. If the fuel filter is found to be substandard, it must be replaced in a timely manner.
3： The oil pipe of the fuel system has some impurities attached to the pipe surface due to poor oil quality, so it is necessary to clean the oil pipe regularly and add diesel additives twice to effectively improve the black smoke.
High temperature cause
For the mechanical equipment powered by diesel engine, if the temperature is high for a long time, it will have a certain impact on the running condition of the whole machine.The internal performance will cause lubrication failure, increased wear of parts, cylinder scuffing, cylinder gasket burning and other serious failures.Therefore, it is necessary for us to understand the cause of high temperature of diesel engine in order to make a simple prevention plan.
Working with overload for a long time will lead to increased oil consumption, increased internal heat dissipation, boiling of cooling water, etc.The best way to deal with this situation is to avoid overloading for a long time.
It is very important whether the liquid quantity inside the mechanical equipment meets the standard. Generally, if the liquid quantity is insufficient, especially the coolant is insufficient, the heat dissipation effect of the equipment will be reduced, thus causing the overheating of the diesel engine.For the high temperature caused by this situation, as long as the inspection work is done well in the daily use process, the insufficient liquid can be replenished in time.
Whether the heat dissipation of mechanical equipment is good, whether the surface cleanliness is good, and whether the cooling fan plays a good role in heat dissipation may result in high temperature failure of diesel engine.In order to put an end to this situation, we only need to do a good job of inspection in daily use to find some abnormalities in time and do a good job of repair or replacement.
advantage
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The advantages of diesel engine are large torque and good economic performance.Each working cycle of the diesel engine also experiences four strokes: intake, compression, power and exhaust.However, because the fuel used in diesel engines is diesel, its viscosity is higher than that of gasoline, and it is not easy to evaporate, and its autoignition temperature is lower than that of gasoline, the formation and ignition mode of combustible mixture are different from that of gasoline engines.The main difference is that diesel enginesCylinderThe mixture in is compression ignition rather than ignition.When the diesel engine is working, air enters the cylinder. When the air in the cylinder is compressed to the end point, the temperature can reach 500-700 ℃ and the pressure can reach 40-50 atmospheres.When the piston is close to TDC, the high-pressure pump on the engine injects diesel oil into the cylinder at high pressure. The diesel oil forms fine oil particles, which are mixed with high pressure and high temperature air. The diesel oil mixture burns by itself, expands violently, generates explosive force, and pushes the piston down to do work. At this time, the temperature can reach 1900-2000 ℃, the pressure can reach 60-100 atmospheres, and the torque generated is large,Therefore, diesel engines are widely used in large diesel vehicles.
According to the national standard (GB252-87),Light diesel oilThe specifications are divided into six grades, namely 10, 0, - 10, - 20, - 35 and - 50 according to the freezing point, which respectively indicate that the freezing point is not higher than 10 ℃, 0 ℃, - 10 ℃, - 20 ℃, - 35 ℃ and - 50 ℃;The higher the grade, the lower the freezing point.
Diesel fuel is used for compression ignitionengine(i.e. diesel engine).The appearance of diesel oil is water white, light yellow or brown liquid.Diesel oil is divided into light diesel oil and heavy diesel oil.Light diesel oil is used as fuel in high speed diesel engines above 1000 r/min, and heavy diesel oil is used as fuel in medium and low speed diesel engines below 1000 r/min.Generally, diesel sold by gas stations is light diesel.The executive standard of light diesel oil products is GB 252-2000 Light Diesel Oil, in which the grades of diesel oil are divided into 10, 5, 0, - 10, - 20, - 35 and - 50, and the diesel oil grades are divided according to the freezing point of diesel oil.
Cold filter point is an important index to measure the low temperature performance of light diesel oil, which can reflect the actual low temperature performance of diesel oil and is closest to the actual minimum operating temperature of diesel oil.When selecting the diesel brand, the user should take into account the local temperature and the cold filter point corresponding to the diesel brand.The cold filter point of No. 5 light diesel oil is 8 ℃, that of No. 0 light diesel oil is 4 ℃, that of No. 10 light diesel oil is - 5 ℃, and that of No. 20 light diesel oil is - 14 ℃.
Brand selection
According to the requirements of GB 252-2000 standard, the light diesel oil brand shall be selected according to the following principles:
1.10 # light diesel oil is applicable to diesel engines with preheating equipment;
No. 2.5 light diesel oil is applicable to areas with a risk rate of 10% and a minimum temperature of 8 ℃ or above;
No. 3.0 light diesel oil is suitable for use in areas where the risk rate is 10% and the minimum temperature is above 4 ℃;
4. No. 10 light diesel oil is suitable for use in areas where the risk rate is 10% and the minimum temperature is above - 5 ℃;
5. No. 20 light diesel oil is applicable to areas with a risk rate of 10% and a minimum temperature of - 14 ℃ or above;
6. - 35 # light diesel oil is suitable for use in areas where the risk rate is 10% and the minimum temperature is above - 29 ℃;
7. - 50 # light diesel oil is suitable for use in areas where the risk rate is 10% and the minimum temperature is above - 44 ℃;
matters needing attention
It is the lack of technical level, rather than the essential problem of diesel engine, which can be solved through technological progress.
First of all, all kinds of driving forces have their due position and timing of development.Don't start research and developmentgaseous fuelAutomobile, hybrid electric vehicleelectric vehicleAs well as new technologies such as fuel cell vehicles are lagging behind, but it is wrong to unilaterally emphasize the possibility of large-scale promotion in the short term, even against the normal development of conventional power.Secondly, gas fuel engines should be evaluated in two ways.Although gas fueled engines can better meet the current emission requirements, which is of great significance to the adjustment of energy utilization structure, the total hydrocarbon emissions (mainly methane) of natural gas engines are higher than diesel engines, and they will also encounter many difficulties in meeting the Euro IV emission standards.Third, emissions and energy conservation are equally important, and both should be considered comprehensively. Energy conservation is not only a matter of saving oil resources, but also an important environmental issue.Take the global greenhouse effect as an example. Diesel engines have low fuel consumption, and CO2 emissions are far lower than gasoline engines, which can reduce by more than 45%Greenhouse gas emissions。
1. Key parts technology: such as oil pump nozzle and supercharging intercooling technology.
2．Fuel quality: High quality and low sulfur diesel fuel is the premise for diesel engines to meet increasingly stringent emission regulations.
3．Electronic control technology: The electronic control technology of diesel engine is very important for the optimization and improvement of the comprehensive performance of the engine.
4. Key technologies of emission post-treatment: such asExhaust gas recirculation(EGR) technology, particulate capture technology and NOx catalytic conversion technology.
5. Complete machine development and matching technology: such as matching and optimization technology of diesel engine fuel, intake and combustion systems, and diesel engine technology for heavy vehicles and cars.
6. Manufacturing, process, material and other technologies of diesel engine.
engine oil
The existing engine oils in the market are classified according to the SAE method. Single grade engine oils include 6 kinds of winter engine oils, 4 kinds of summer engine oils and 16 kinds of multi grade engine oils.The grades of winter oil are 0W, 5W, 10W, 15W, 20W and 25W respectively;The grades of summer oil are: 20, 30, 40, 50;The general oil grades in winter and summer are: 5W-20, 5W-30, 5W-40, 5W-50, 10W-20, 10W-30, 10W-40, 10W-50, 15W-20, 15W-30, 15W-40, 15W-50, 20W-20, 20W-30, 20W-40, 20W-50.
The details are as follows: API isAmerican Petroleum InstituteThe API grade represents the quality grade of engine oil.It uses simple codes to describe the working ability of the engine oil.
API engine oil is divided into two categories: "S" series represents gasoline engine oil;"C" series represents diesel engine oil;When the two letters "S" and "C" exist at the same time, it means that the engine oil is of gasoline diesel universal type.
The letter after S or C means:;From "SA" to "SL", the performance of the engine oil will be better than the former with each letter increment, and there will be more additives used to protect the engine in the engine oil.The later the letter is, the higher the quality level is. The oil level of international brands is more than SF.For example, Shell Helix Plus is API SL, while Shell Helix Red Motor Oil is API SG, which indicates that the quality level of Shell Helix is higher than that of Red Heineken.
Mechanism components
Diesel engineThe main mechanism components of the engine generally include: engine body, crank connecting rod mechanism, valve mechanism, fuel system, lubrication system, cooling system, and electrical system.
1. Engine body: it is the framework of the diesel engine, which supports and installs other parts, including: cylinder block, cylinder liner, cylinder head, cylinder gasket, oil pan, flywheel housing, timing gear housing, front and rear feet.
2. Crank connecting rod mechanism: it is the main moving part of the diesel engine. It can transfer the energy generated by fuel combustion into mechanical energy through the piston, piston pin, connecting rod, crankshaft and flywheel.Including crankshaft, connecting rod, piston, piston pin, piston pin circlip, piston pin bushing, piston ring, main bearing, connecting rod bushing, thrust bearing, crankshaft front and rear oil seals, flywheel, shock absorber, etc.
3. Valve mechanism: open and close the inlet and exhaust valves regularly.Including timing gears, camshafts, tappets, lifters, rocker arms, valves, valve springs, valve seat rings, valve guides, valve keys, intake and exhaust pipes, air filters, silencers, superchargers, etc.
4. Fuel supply system: according to the needs of the diesel engine, diesel fuel is supplied to the combustion chamber for combustion in a regular and quantitative manner.Including diesel tank, fuel delivery pipe, diesel filter, fuel injection pump, fuel injector, etc.
5、lubricationSystem: It supplies lubricating oil to all moving friction pairs, including oil pump, oil filter, pressure regulating valve, pipeline, instrument, oil cooler, etc.
6. Cooling system: It is used to distribute the heat generated by the diesel engine to the atmosphere.includewater tank、Water pump、Fan, water pipethermostat, water filter, fan belt, water temperature gauge, etc.
7. Electrical appliances: auxiliary equipment for starting, lighting, monitoring and operation.includealternator, starting motor, battery, relay, switch, circuit, etc.
Maintenance
The maintenance is different for different seasons.Before starting the vehicle, the heavy truck diesel engine must be fully filled with coolant to avoid starting without water.Do not add cold water when the engine body temperature is too high to prevent the cylinder body from cracking.
When parking at low temperature outdoors in winter, pay attention to water drainage (or add antifreeze) to prevent the cylinder body from freezing;The specified temperature must be maintained when the vehicle is running, and cooling water is indispensable to prevent the engine from being too cold or overheated;Check the oil level before starting. The oil level must reach the specified scale on the oil dipstick. Add or replace it if necessary;The engine maintenance shall strictly follow the operating procedures to avoid unnecessary artificial damage.
When the flatness error of the cylinder block plane exceeds the limit, the cylinder gasket will not be pressed tightly, resulting in water leakage, air leakage, oil leakage and ablation.
Level II maintenance can be checked with a dial indicator: support the cylinder block on the platform so that the plane of the cylinder block is parallel to the platform, that is, find two equal high points on the four diagonal lines.Move the dial gauge holder along the platform, and the difference between the maximum and minimum readings of the dial gauge in the tested plane is the flatness.It can also be checked by placing a flat ruler on the tested plane and filling the gap between the two planes with a feeler gauge. The maximum value of the feeler gauge inserted into the gap is the flatness.The technical requirement is that the flatness error of the upper plane of the cylinder block shall not be less than 0.05mm for every 50mm length.The total length of six cylinder engine with cast iron cylinder block shall not exceed 0.30mm, four cylinder engine shall not exceed 0.20mm, aluminum alloy cylinder engine shall not exceed 0.50mm, four cylinder engine shall not exceed 0.30mm.
If the flatness error of the cylinder block plane exceeds the limit, it must be repaired.If it is a local bulge, it can be smoothed with an oilstone or a fine file;Slightly large depressions can be repaired by grinding or milling, but the machining allowance should not be too large, otherwise the compression ratio will increase and cause sudden explosion.
In December 2012, the production and sales of automotive diesel engines declined year-on-year
In December 2012, 1598626 and 1552041 engines were produced and sold in China, respectively. In 2012, 17538111 and 17525853 engines were produced and sold in total, representing an increase of 4.90% and 3.27% respectively over the previous year. The indifference of the diesel engine market dragged down the year-on-year growth of the whole industry.In December 2012, 305454 and 306140 diesel engines were produced and sold in China. In 2012, 3320805 and 3395241 diesel engines were produced and sold in total, down 7.73% and 10.41% from the previous year, respectively, by 0.25 percentage points and 2.88 percentage points.In December, the diesel engine supply and demand trend was developing, and the demand market slightly improved.
Oil leakage treatment
Diesel engine is the most widely used power element in agriculture, and most agricultural machines are powered by diesel engine.However, the phenomenon of diesel engine oil leakage is also common. How to save fuel costs, please treat it skillfully according to the following circumstances.
Fuel return of fuel injection nozzle: fuel injection nozzle is a precision part.If the diesel engine does not use clean diesel or the machine has been used for a long time, the fuel will return due to wear of the fuel injection nozzle.However, it is expensive and uneconomical to replace the fuel injection nozzle. In order to avoid leakage of the return oil, the oil can be led back to the fuel tank through the return pipe or into the diesel filter.If the oil return pipe is damaged, a piece of plastic pipe can be used to introduce the oil into the self provided container, and then the oil can be poured back to the oil tank after being filtered.
Oil leakage in the oil transmission part: appropriate treatment can be made according to the situation: the washer of the hollow screw of the oil transmission pipe is uneven, the washer can be removed, polished and then padded. If the problem cannot be solved, the washer can be replaced with a new one, or the washer can be cut into thick soft plastic materials and replaced with a new one;The oil leakage at the joint between the plastic oil pipe and the metal is mostly caused by the hardening or cracking of the plastic oil pipe. The hardened and cracked parts can be cut off, and then the hot water can be used to soften them. They can be installed on the metal joint while it is hot, and then the metal wire can be used to bind them firmly;If the metal oil pipe is broken and leaks oil, the broken part can be brazed.In addition, in order to prevent the oil pipe from cracking, when installing the oil pipe, the bending should be appropriate, do not pull it hard for installation, and do not contact the body of the pipe to avoid abrasion.
Oil leakage of valve cover: when the valve cover is installed, if the tightening force is too large, it is easy to deform and leak oil.At this time, the leaking valve cover can be removed, and carefully hammered and reshaped with a wooden rod to make its contact surface smooth. Then, the gasket can be padded and installed.
