Heat exchanger of engine lubrication systems SMD-31

Contents

Introduction

1 Structurally operational analysis

Lubrication systems

Requirements for lubrication systems

Oil cooling system

Oil radiators

Patent search

Design diagram selection and substantiation of basic parameters

Heat Exchanger Layout

Design part

3.1Heat calculation of SMD- engine

3.1.1Defining of compression polytron in compressor and air temperature after cooling

3.1.2 Working medium parameters

3.1.3 Cylinder cleaning and charging parameters

3.1.4 Calculation of compression process

3.1.5 Calculation of combustion process

3.1.6 Calculation of expansion process

3.1.7 Definition of indicator and effective indicators

3.2 Heat Balance

3.3 Calculation of recuperative heat exchanger of tubular type

3.3.1 Selection of cooler type and coolant relative motion diagram

3.3.2 Determination of oil flow through heat exchanger

3.3.3 Determination of water flow through heat exchanger

3.3.4 Selection of the main structural dimensions of the cooler

3.3.5 Finding the final water and oil temperatures at the heat exchanger outlet

3.3.6 Finding the average temperature head

3.3.7 Find the number of pipes in the heat exchanger core

3.3.8 Find heat transfer coefficient for oil

3.3.9 Finding heat transfer coefficient from water

3.4 Hydrodynamic calculation of heat exchanger

Production and technical operation

Types and periodicity of maintenance

List of works performed for each type of maintenance (maintenance)

Safety of life

The analysis of production dangers and harm at operation of the upgraded SMD-engine

Engineering Solutions

Fire safety

Environmental protection

Emergency security

Economic section

Source Data for Calculation

Performance calculation

Calculation of investments (capital investments) in equipment

Calculation of operating costs

Wages of production workers

Cost of maintenance of machine shift

Calculation of economic impact and efficiency indicators

Notion- annual savings from reduction of track cost

Payback period for new capital investments

We calculate the annual economic effect by the formula

Net discounted income is determined by formula

Conclusion

List of literature used

Applications

Introduction

Progress in the automotive and tractor industry, a further increase in the turnover of road transport, a significant expansion of the tractor fleet in agriculture provide not only for the quantitative growth of the motor tractor fleet, but also for a significant improvement in the use of existing cars and tractors, an increase in the culture of their operation, and an increase in inter-repair time.

In the field of development and improvement of automobile and tractor engines, the main tasks at the present stage are: expanding the use of diesel engines, reducing fuel economy and specific gravity of engines, the cost of their production and operation. At a fundamentally new level, the fight against toxic emissions into the atmosphere is set, as well as the tasks of reducing the noise of engines during their operation. Considerable attention is paid to the use of electronic computers in the calculation and testing of engines. Ways of using computer equipment are outlined directly in engine designs and primarily in diesel engine designs. [7]

Internal combustion engines, which are one of the main means of energy, are used in various sectors of the national economy. Not only the field of application, but also the specific purpose of the engine imposes certain specific requirements on its design, operation modes, control method, etc., as a result, the engines of the same dimension and power, but intended for different areas of use, have nothing to do with each other and cannot be unified by the main elements.

Tractor engine building in our country has characteristic features due to the wide range of agricultural tools used on tractors, which often have active organs, which requires the availability of additional power take-off devices on engines.

Scientific research and design organizations of the industry have accumulated extensive experience in developing and refining forced tractor engines. Specific methods for calculating the main units and systems of tractor diesel engines, methods for choosing the main structural relationships, fundamental layout schemes of both the diesel engine as a whole and its main elements have been established.

The general technical requirements for tractor diesel engines, determined by the current GOST, include such specific requirements as fuel and oil standards, degree of forcing, control methods, degree of unification, motor resource, start-up features, etc. It is their totality that determines the task of creating an engine of specific models.

Structurally Operational Analysis

Lubrication systems

The oil system provides lubrication of engine motors in order to reduce friction, prevent corrosion, remove wear products and partially cool its individual units.

Engine lubrication system shall be equipped with devices for oil storage, its supply to friction surfaces, oil cleaning from contamination, cooling, as well as monitoring of lubrication processes and oil condition. The combination of all these devices form the engine lubrication system.

Depending on the method of organization of oil supply to friction surfaces, the following lubricating systems are distinguished: sprayed oil, forced and combined.

The sprayed oil lubrication system is used in simple engines, which, as a rule, have rolling bearings as bearings of the crankshaft and distribution shaft. In this case, lubricating oil is poured into the crankcase of the engine to the level at which a special protrusion - a scoop on the connecting rod or the cover of the connecting rod bearing is immersed in the oil when the piston is located near n.m.t. The resulting small splashes of oil (oil mist) are spread by crankcase gases over the entire volume of the crankcase and, settling on the working surfaces of cylinders, rolling bearings, piston pins and pushers of the gas distribution mechanism, lubricate them. In such engines, the rockers of the valve mechanism, speed controllers and other units are lubricated from separate lubricants with grease or liquid oil poured into the corresponding cavities. If the engine is used as connecting rod bearings, sliding bearings, then a hole is drilled in the cover near the scoop and bearing insert, through which, when the scoop strikes the oil surface, the latter is forced into the bearing.

Sometimes the engines are equipped with the simplest gear pump, which supplies oil to special trays under the connecting rods. This reduces the energy consumption for excessive bubbling of oil at a high level immediately after filling and increases the reliability of the engine, since the lubrication intensity does not depend on the oil reserve in the crankcase.

In carburetor two-stroke engines with a crank chamber gas exchange scheme, oil is added to the fuel in a proportion of 1:20.... 1:50; when filling crankcase with fuel-air carbureted mixture, oil mist is deposited on friction surfaces and lubricates them.

Forced lubrication systems are used in forced engines, in which to eliminate overheating of friction surfaces in oils, using special pumps, its intensive circulation is created not only through the bearings of the crankshaft, but also through the bearings of the piston pin, camshaft, transmission shafts, coolers and filters. In addition, oil is supplied to the pistons for their cooling, to the drives of the units, to the devices for controlling the engine and its units (servomotors of the mechanisms for reversing the ship's engines).

Depending on the storage location of the oil reserve required for circulation, forced lubrication systems, in turn, are divided into systems with a wet crankcase, in which the oil supply is stored in the crankcase tray or engine frame and on dry crankcase systems, in which the oil supply is stored in circular cans or tanks, and the crankcase tray or engine frame are only oil collectors, cooled pistons, servomotors, gears or units flowing from lubricated surfaces or cavities.

In wet crankcase lubrication systems, pressurized oil is supplied to the rubbing surfaces. For cooling, part of the oil of the discharge section of the pump is supplied to the oil radiator.

In dry crankcase systems, oil from the tank is supplied to the main oil line and under pressure to all rubbing surfaces, and then pumped from the crankcase to the tank by the pump. The dry crankcase lubrication system is used in engines that change their position relative to the horizon during operation, as a result of which it is possible to expose the oil intake and disrupt the oil supply by the pump, increase the oil release through the glands and oil filling necks (ship, aircraft engines, etc.). in high-speed engines, the use of the dry crankcase system is also explained by the fact that the oil contacts the crankcase gases and heated engines less time, foams less, oxidizes more slowly and is saturated with water and fuel, which helps to preserve the oil properties, reduce costs and increase the time between oil changes.

Combined lubrication systems make it possible to simplify the design of the engine, since part of the friction surfaces is lubricated by spraying, and under pressure oil is supplied only to the most stressed friction units, mainly to the bearings of the crankshaft and distribution shaft.

As regulating and controlling the operation of lubrication systems, devices and a number of devices are used. Reduction valves are installed, as a rule, in oil pumps on the discharge side and are adjusted to the maximum permissible pressure (0.2... 1.5) Mpa.

Opening at high pressures occurring during the start-up of cold engines, when the viscosity of the oil is high, they ensure that the oil is drained into the crankcase or bypassed for suction into the pump. In addition, these valves protect the oil pump and its drive., filters, lines, pressure gauges from breakdowns and damage.

Safety bypass valves are installed parallel to full-flow filters and coolers. They are adjusted accordingly to the pressure (0.2... 0.25) Mpa and (0.08... 0.15) Mpa. The purpose of these valves is to provide access of at least crude oil to the main oil line and uncooled oil to the tray or circulation tank, bypassing filters and coolers in case of their clogging or excessive oil viscosity at engine start-up. In the last designs of engines, they began to install bypass ones with an annunciator - contact, which includes a test light bulb on the instrument panel when the slide valve moves. This reduces engine operating time without oil filtration.

Drain valves connected to the main oil line maintain a constant pressure (0.4... 1.0) Mpa in it, as a result of which the oil (circulation reserve) is drained into the crankcase through the drain valve. In addition, the drain valves are annunciators of the state of conjugated friction pairs: as the wear increases, clearances increase, less oil is drained through the drain valve, then the drain stops, and the pressure in the main line begins to drop, since the oil flow through the clearances exceeds its supply by the pump. When minimum pressure is reached in the main oil line, the engine shall be repaired .

Control devices in engine lubrication systems are - indicators of oil quantity in tanks of lubrication system (crankcase, circulation tanks), made in the form of steel round or flat rods with marks corresponding to lower and upper oil levels; oil-metering glass tubes installed on circulation and spare tanks; electrical remote level indicators; pressure gauges and differential pressure gauges, which allow to monitor pressure in the main oil lines, in front of individual units, for example turbocompressors, and pressure drop in filters and oxidizers; thermometers for determination of oil temperature in oil collector or in main oil line (after cooler).

The lubrication systems also include the following additional devices:

drain holes with plugs and cranes in crankcase pallets, filter and cooler housings, as well as in circulation tanks, allowing to drain oil when replacing it or cleaning the internal cavities of the corresponding devices from deposits and settling;

defoamers in the form of nets located in crankcase and circulation tanks;

necks for oil pouring into crankcase and tanks having devices,

connecting cavities of crankcase and tanks with atmosphere and preventing oil mist release in case of pressure fluctuations in crankcase and ingress into it together with air (breathers);

ventilation devices contain elements preventing

removal of oil drops (stuffing, chops, etc.);

- crankcase ventilation systems, by means of which gases, water and fuel vapors are sucked from the latter and sent to the engine inlet system, which improves the operating conditions of oil, oil collecting rings, filters, glands and reduces the release of toxic components into the atmosphere;

- oil heaters and oil pumping devices are included in the lubrication system to ensure the engine shaft is checked during start-up and reduce wear of its parts during start-up and warm-up periods.

Oil is heated by electric heaters, which are installed in tanks and pallets of engines. They work from batteries. Also starting heaters of the PZHB type.

- oil pumping devices are designed to create pressure in the system before starting the engine and are oil pumps with manual or electric drive.

1.2. Requirements for lubrication systems

Lubrication systems shall provide the following functions:

- reliable oil supply at all engine operating modes to all friction parts of the engine, internal device cooled by oil and surfaces in which oil is used as working medium (servomotors and regulators);

- operation of engines and their units in different environmental conditions and in all operating modes;

- assigned duration of engine operation without stops for oil filling, regulation and elimination of flaws in lubrication system for cleaning of deposits, impurities, slag and coke on surfaces of engine parts and their units;

- long-term operation of oil and its low consumption;

- in addition, they must be compact, simple and non-labor-intensive in maintenance, have a low cost.

Based on the operating conditions of diesel engines, their types, assignments, the degree of satisfaction with these requirements can be different, which determines the complexity, cost, compactness of the lubricating system and their elements. It should be noted that there is a clear trend of structural complication of lubricating systems of all types of engines, not only due to the expansion of oil functions in power plants, but also in order to increase the reliability of the engine components of lubricating systems, simplify and automate maintenance, increase the service life of oil, reduce its costs.

1.3. Oil purification and cooling system

Oil filters are designed to clean oil in the engine lubrication system, from impurities (water, soot, fuel, dust, parts wear particles, deposit products, etc.)

Oil filters with good cleaning action shall have low hydraulic resistance at small sizes and operate without maintenance for long periods determined by the necessary engine maintenance at stops, or allow such when the engine is operating.

According to the principle of action, all used filters are divided into mechanical, absorbing, chemical, hydrodynamic and magnetic, and according to the degree of oil purification and the method of inclusion in the circulation circle - into coarse (full-flow), included in series, and fine filters, included in parallel to the main oil line. Through fine filters is passed from (8. 20)% of oil supplied by pumps.

Supercharging turbocompressor bearing lubrication systems use full-flow oil cleaning in fine filters regardless of whether the system is part of the engine lubrication system or separate.

Mechanical filters are divided into mesh and slot filters. Filter elements of screen filters are made of metal nets or set of perforated plates. The degree of oil purification in them is determined by the size of the cells and the number of filter layers in the oil path. As safety nets and for foam extinguishers, nets with a number of holes up to 100 per 1 cm2 are used, as filter nets - nets with a number of holes (200.... 50000) cm2.

In order to increase the continuous operation time of the engine, coarse filters are sequentially connected, which makes it possible to turn on one of the filters for cleaning.

Slot filters can be cleaned when the engine is running; cleaning process is easily automated. These filters are divided into plate and wire filters. Width of slots between plates and wire turns (0.03... 0.15) mm. Such filters are used as full flow coarse filters.

Mechanical filters also include filters having a filter element of felt, cotton yarn, textile materials, cardboard, paper. They are used for both coarse cleaning and fine cleaning.

Absorption filters not only retain mechanical impurities, but also absorb free acids, alkalis, water, providing deeper purification of the oil. The filtering materials used are paper, sawdust, yarn, felt and other materials with special impregnations, as well as inorganic materials, for example, mixtures of alumina (30... 35)%, bauxite 50%, manganese additives 1%, sulfur 0.5% and filler - slag wool. During clogging, the filter element is replaced.

Hydrodynamic filters. The principle of operation of the filter (centrifuge) is based on the use of centrifugal forces. In the rotating stream, impurities having a density greater than that of the oil are separated from the oil. Cleaned oil is sent to cooler, engine crankcase or main tank. Impurities from the centrifuge are periodically removed. The rotor is driven from one of the engine shafts, by an autonomous electric motor (active drive) or by jet forces of the cleaned oil jets ejected from the rotor through special nozzles (jet drive).

Centrifuges provide good cleaning of oil from particles of more than (0.5... 1) mm at low resistance, so they are used in engines of all types, both with serial and with parallel inclusion in the system.

Centrifugal cleaning of oil also takes place in hollow journals of crankshaft, at that oil is extracted into bearings from layers located as close to axis of shaft rotation as possible.

During centrifugal cleaning, the densest impurities are determined,

having abrasive properties, therefore, the wear of rubbing surfaces during such cleaning is reduced by 3... 4 times. An example of a centrifugal filter design is the 12DN23/30 motor filter. it is connected parallel to the main oil flow. A check valve is included in the structure, which turns off the centrifugal filter when the pressure in the system decreases.

Magnetic filters. These filters are installed in the engines not only for the period of run-in, but also for further operation, since they well retain metal particles together with enveloping resins and protect oil pumps and fine filters from premature wear and clogging. Such filters are permanent magnets embedded in the plugs of special holes in the crankcase tray, in full-flow filters, coolers and tanks.

When installing filters on the engine or power plant, they should be easily accessible during operation for cleaning and changing filter elements.

1.4. Oil radiators.

To maintain the oil temperature within the required limits, oil radiators are used. This is especially important when the engine is operating with a high load at a high ambient temperature. Radiators of different types are installed on engines of different types.

Air-cooled engine oil radiators are an aluminum tube connected to the oil lines through which oil flows from the filter to the engine. Tube is installed on air path from fan to engine cylinders. The temperature of the oil passing through the tube is reduced by approximately

(20... 22) ° С), in the engine crankcase (at oil temperature upstream of the radiator (95... 110) ° С).

Oil radiators of engines with liquid cooling are made of steel tubes rigidly connected to lower and upper tanks. Inside the upper tank there is one partition, and the lower tank - two. The partitions cause the oil entering the radiator to make two strokes through its tubes, which significantly improves cooling, making it more intense. Such radiators are installed ahead of the engine liquid cooling radiator and are fixed on its struts.

There are also the following methods of cooling the oil. Oil is cooled by blowing cast from light alloys of finned pan of crankcase. In forced engines, the oil is cooled in an oil radiator washed by the air flow coming in during movement and the flow created by the fan. In such cases, the radiator is installed between the fan and the engine.

Under low temperature conditions, it is necessary not only to warm up the combustion chamber (cylinder block) and facilitate the ignition of fuel, but also to reduce the viscosity of freezing motor oils (for example, by diluting with winter diesel fuel or heating using pre-start heating means). The cylinder block is almost always heated using group or individual means of pre-start thermal preparation using hot water, steam, gas-air mixture, electric energy and other heat carriers. Engine oil always does not always have time to warm up well before starting the engine, therefore, during the start-up period - heating the parts of the CPG and KSM often work in the mode of oil starvation and intense wear. Due to the long delay in the supply of fresh lubricant, crankshaft bearing failures are common in the coupling. So, it is widespread to heat the engine with hot water (by pouring it through the cooling system) the oil in the tray has to be heated primitive, inefficient and

hazardous means (soldering lamps, flares) or hot gases of individual or group heaters.

It should be noted that there is no device in the lubrication system that reduces the duration of heating of the oil after starting the engine. Also, its temperature mode during summer and winter operation is not controlled. Air-oil radiators installed on tractors and cars only cool the oil regardless of its temperature and prevent overheating in the summer, in winter they turn off.

The absence of devices that support the optimal temperature mode of the lubrication system leads to the fact that in winter operation the engines operate for a long time with a lower engine oil temperature (below 45... 50 ° С). Due to the increased viscosity and therefore insufficient consumption of oil to drive the centrifuge in these modes, the rotation speed of the centrifugal filter rotor decreases, the quality of cleaning the oil from abrasive particles sharply deteriorates, and the wear of engine parts increases. It was found that about 70% of the total crankshaft wear refers to the period of inefficient operation of the centrifuge at a reduced temperature of the lubrication system.

The noted disadvantages of the system are largely eliminated by the use of water-oil radiators that reduce the duration of heating after start-up and support the optimal temperature mode of lubrication.

When the heat exchanger is constantly connected to the cooling system parallel to the cylinder block, it performs not only pre-start heating, but also reduces the duration of heating after start-up, as well as contributes to maintaining the optimal operating temperature of the oil. Functionality of the water-to-oil heat exchanger

It is fully used when sequentially connected to the cooling system. In this case, in order to avoid a significant increase in the hydraulic resistance when the coolant moves through the heat exchanger, it is necessary to increase its flow section by using pipes of a larger diameter to manufacture it. Increasing the diameter of the work, volume and surface of the heat exchange, as well as a large amount of liquid circulating intensively through the heat exchanger, can provide not only effective pre-start heating and heating of the oil after start-up, but also an optimal temperature mode during operation. At the same time, the size of the bridges between the holes was 2.7 and 2.5 mm. In the development of the core design, a variety of pipes and sheets currently produced by our industry is used. Medium hardness solder is used for soldering.

For maintenance of engine lubrication system centrifugal fine filter is combined with heat exchanger. It is installed on top of the heat exchanger housing.

Currently, two types of water-oil heat exchangers are mainly used on modern tractor diesel engines.

Tubular coolers are widespread due to simplicity, compactness, ease of manufacture, operation and repair. Oil in tubular coolers is pumped inside or outside the tubes. In order to intensify heat transfer from oil, in the first case inside the tubes, oil flow swirlers are installed, in the second case the tubes are finned or transverse partitions are installed inside the housing to impart wave-like motion to the oil flow.

Plate coolers are assembled from sections formed by two stamped plates, between which oil flow swirler is located. The use of plate coolers gives a 50% and a weight gain of about 40% over tube coolers.

Elimination of overflow between the housing and partitions is achieved by installation of sealing rings from oil and gas resistant rubber or metal spring rings. Sealing of covers is performed by installation of gaskets from paronite or rubber.

Design diagram selection and substantiation of basic parameters

2.1 Heat Exchanger Layout

Heat exchanger arrangement on SMD engine 31 provides for engine placement on tractor LT-157.

Heat exchanger is arranged in lower left part of engine and secured on crankcase unit. Heat exchanger design with the scheme of its inclusion in lubrication systems and coolings are presented in a graphic part of the thesis on sheet 09. SAT.DP.DVS.00.000.CX and 1.2 sheets 09. SAT.DP.DVS.01.00.000.SB

Heat exchange unit (core) is located in housing made in the form of pipe. The smooth tube core is a bundle of brass tubes, 109 pieces with a diameter of 6 mm, soldered with brass tube boards by medium-melting solder by high-temperature soldering.

Oil movement is performed by countercurrent flow outside the tubes, water - inside. In order to ensure the necessary intensity of heat transfer from the oil to the surface of the tubes, the core is divided by segments with partitions providing 10 moves of transverse flow of cooling tubes ./17/

In proposed version of heat exchanger, core is arranged in tube boards with spacing of 7.0x8.0mm. In this case, the size of the jumpers between the holes will be 2.2x2.0mm. In the development of the core design, a variety of pipes and sheets currently produced by our industry is used. Medium hardness solder is used for soldering.

The following heat exchanger is provided on sheet 09.SAT.DP.DVS.01.000.SB:

centrifugal oil filter;

heat exchanger core;

heat exchanger housing;

filler neck;

drain valve.

To facilitate maintenance of engine lubrication system, centrifugal fine filter is combined with heat exchanger. It is installed on top of the body of the heat exchanger of the apparatus. In this heat exchanger, we use a centrifugal filter developed at the Department of Mechanization of L/P and L/X by Associate Professor R.P. Kapustin.

The advantage of this filter is the improvement of cleaning efficiency, prevention of sludge flushing, convenience of maintenance and low oil consumption for the centrifuge drive .

Economic section

In the diploma project, the SMD31 diesel lubrication system was modernized in order to increase power, load capacity, etc.

The economic section justifies the cost-effectiveness of modernization of the SMD31 lubrication system.

Conclusion

Switching the heat exchanger into the lubrication system of the in-line engine of increased power modification 64H 12/14 (SMD31) is carried out for full flow (see Figure 1, sheet 26).

The water cavity of the heat exchanger is partially connected in-line to the engine cooling system: on engines with an in-line arrangement of cylinders - parallel to the water distribution channel of the block case. By-pass of required amount of water into heat exchanger is achieved by installation of special throttling washers.

Advantages of oil-water heat exchangers of SMD-31 engine:

1. the use of water as a cold coolant and the use of countercurrent gives a great effect; diesel overheating is practically excluded;

2. fast heating of the engine during start-up, especially at minus ambient temperature and maintaining a stable thermal state of oil during operation in various climatic conditions and all modes helps to reduce fuel consumption due to reduced friction losses in diesel bearings;

3. the unit has relatively small dimensions and mass, since it is located directly on the engine;

4. heat exchanger core has good thermohydraulic characteristics, easy to manufacture, repairable;

5. during operation it is possible to perform periodic cleaning of oil and water cavities with low costs;

6. reduced consumption of non-ferrous metals by 7-9 kg for each water-oil heat exchanger compared to air-oil heat exchanger.