Marine engine 6l by Burmeister and Vine. Marine diesel engine marking

By discipline: Marine internal combustion engines

Marine engine 6l by Burmeister and Vine. Marine diesel engine marking

By discipline: Marine internal combustion engines

Selection of the number of shafting and the type of propeller

Selection of the number of shafting and the type of propeller

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Electronic motors MAN and Burmeister and Wine - ME (2)\u003e

The first electronically controlled engine by MAN was created on the basis of the MC model in 2003. In this engine, the company abandoned the camshaft with its drive and introduced electronic control: the fuel supply process, speed control, replacing the mechanical regulator with an electronic one, the processes of starting and reversing the engine, the exhaust valve and cylinder lubrication.

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Fuel injection and exhaust valves are controlled by hydraulic servo drives. The oil used in the hydraulic system is taken from the circulating lubrication system, passed through a fine filter and by motor-driven or electric pumps (at start-up) compressed to a pressure of 200 bar. Then the compressed oil goes to the diaphragm accumulators and from them to the fuel injection pressure booster and the exhaust valve hydraulic drive pumps. From the diaphragm accumulators, oil flows to the electronically controlled proportional valves ELFI and ELVA, which open under the action of a signal from the electronic modules (CCU) installed for reliability on each cylinder.

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Hydraulic injection pressure boosters are piston servomotors in which a large-diameter piston is exposed to oil under a pressure of 200 bar, and a small-diameter piston (plunger), which is an extension of a large-diameter piston, when it moves up, compresses fuel to pressures of 1000 bar (ratio areas of the servo piston and plunger is 5). The moment the oil enters under the servo piston and the start of fuel compression is determined by the receipt of a control pulse from the CCU electronic module. When the fuel pressure reaches the opening pressure of the injector needle and the stop of injection occurs when the fuel pressure drops, the latter is determined by the moment the control valve is closed and the oil pressure in the servomotor is released.

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Marine diesel from MAN B&W Diesel A / S, brand L50MC / MCE - two-stroke single-action, reversible, crosshead, gas turbine supercharged (with constant gas pressure in front of the turbine) with built-in thrust bearing, in-line cylinder arrangement , vertical.

Cylinder diameter - 500 mm; piston stroke - 1620mm; purge system - direct-flow valve.

Diesel effective power: Ne \u003d 1214 kW

Rated speed: n n \u003d 141 min -1.

Effective specific fuel consumption in the nominal mode g e \u003d 0.170 kg / kWh.

Diesel overall dimensions:

Length (on the base frame), mm 6171

Width (on the base frame), mm 3770

Height, mm. 10650

Weight, t 273

A cross section of the main engine is shown in Fig. 1.1. Cooling liquid - fresh water (closed system). The temperature of fresh water at the outlet of the diesel engine in the steady-state operating mode is 80 ... 82 ° С. Temperature difference at the inlet and outlet of the diesel engine - no more than 8 ... 12 ° C.

The temperature of the lubricating oil at the inlet to the diesel is 40 ... 50 ° C, and at the outlet from the diesel is 50 ... 60 ° C.

Average pressure: Indicator - 2.032 MPa; Effective -1.9 MPa; The maximum combustion pressure is 14.2 MPa; Purge air pressure - 0.33 MPa.

The assigned resource before overhaul is at least 120,000 hours. The service life of the diesel engine is at least 25 years.

The cylinder cover is made of steel. An exhaust valve is attached to the central hole using four studs.

In addition, the cover is provided with drilled holes for the nozzles. Other drills are for indicator, safety and start valves.

The top of the cylinder liner is surrounded by a cooling jacket fitted between the cylinder cover and the cylinder block. The cylinder bushing is attached to the top of the block by a cover and centered in the bottom hole inside the block. The tightness from cooling water and purge air leaks is ensured by four rubber rings nested in the grooves of the cylinder bushing. On the lower part of the cylinder sleeve between the cooling water and purge air cavities there are 8 holes for the fittings for supplying lubricating oil to the cylinder.

The center section of the crosshead is connected to the journal of the head bearing. The cross member has a hole for the piston rod. The head bearing is equipped with shells, which are filled with babbitt.

The crosshead is equipped with boreholes for supplying oil through a telescopic tube partly for cooling the piston, partly for lubricating the head bearing and guide shoes, and also through a hole in the connecting rod for lubricating the crank bearing. The center hole and the two sliding surfaces of the crosshead shoes are filled with babbitt.

The crankshaft is semi-part. The frame bearings are supplied with oil from the main lubricating oil line. The thrust bearing serves to transmit the maximum stop of the screw through the screw shaft and intermediate shafts. The thrust bearing is installed in the aft section of the base frame. The thrust bearing lubrication oil comes from the pressure lubrication system.

The camshaft consists of several sections. The sections are connected using flange connections.

Each cylinder of the engine is equipped with a separate high-pressure fuel pump (HPP). The fuel pump operates from a cam washer on the camshaft. The pressure is transmitted through the pusher to the plunger of the fuel pump, which is connected by means of a high-pressure pipe and a junction box to the injectors mounted on the cylinder cover. Fuel pumps - spool type; injectors - with central fuel supply.

Air is supplied to the engine by two turbochargers. The TK turbine wheel is driven by exhaust gases. A compressor wheel is installed on the same shaft with the turbine wheel, which takes air from the engine room and supplies air to the cooler. A moisture separator is installed on the cooler body. From the cooler, air enters the receiver through open non-return valves located inside the charge air receiver. Auxiliary blowers are installed at both ends of the receiver, which supply air past the coolers in the receiver with the non-return valves closed.

Figure:

The engine cylinder section consists of several cylinder blocks that are anchored to the base frame and crankcase. The blocks are connected to each other along vertical planes. The block contains cylinder bushings.

The piston consists of two main parts, a head and a skirt. The piston head is bolted to the upper piston rod ring. The piston skirt is attached to the head with 18 bolts.

The piston rod has a through hole for the cooling oil pipe. The latter is attached to the top of the piston rod. Then the oil flows through the telescopic tube to the crosshead, passes through the drill in the base of the piston rod and the piston rod to the piston head. Then the oil flows through the drilling to the bearing part of the piston head to the piston rod outlet pipe and then to the drain. The stem is attached to the crosshead with four bolts passing through the base of the piston stem.

Used grades of fuels and oils

The choice of the type of the main gear and the main engine will be made in a complex. The main engine options will be selected based on the calculated effective power. Consider 3 diesels:

Characteristics of the received internal combustion engine.

Required power of one main engine \u003d kW

The table shows that the lowest specific fuel consumption is for MAN-Burmeister and Vine S60MC, it is low-speed, which allows it to work on a propeller without using a reduction gear. These indicators increase the efficiency of the engine and simplify the operation process.

To summarize, we accept the CDS as a variant of the SEP installed on the projected vessel. As the main engine and type of transmission, we take the MOD "MAN-Burmeister and Vine" S60MC with direct transmission and fixed pitch propellers. To provide the required power, two such motors must be installed.

Main characteristics of the MAN-Burmeister and Vine S60MC engine

The number of shafting is selected from the assignment for the course project in accordance with the number of propulsion devices. The projected vessel must have two propellers. Modules with direct transmission are used as the main ones, so I decide to install two single-shaft SDUs. This scheme provides high survivability and maneuverability. When choosing a type of propulsion unit, one considers the advantages and disadvantages of each type, the expediency of its use on a given vessel, the initial cost of the vessel and operating costs. An installation with a fixed pitch propeller is simpler and cheaper, more convenient in maintenance, and the most maintainable compared to a fixed pitch propeller. Also, the CPP has a slightly lower efficiency (by 1 - 3%) than that of the FPP. due to the large diameter of the hub in which the swing mechanism is located. This determined the widespread use of installations with fixed pitch propellers on ships of the transport marine fleet with established sailing modes: oil tankers, dry cargo ships, timber carriers, coal carriers, refrigerated transport vessels, and fishing vessels.

The use of an adjustable pitch propeller allows for a quick transition from forward to reverse, which improves the maneuverability of the vessel.

From the above, it follows that the use of fixed pitch propellers will be expedient for this vessel.

The nozzle design of the Burmeister and Vine marine diesel engines (Fig. 6.4.5., A) was used with minor changes until a fundamentally new nozzle with a different nozzle was created (Fig. 6.4.5., B).

In the construction shown in fig. 6.4.5., A, the nozzle 10 is pressed into the body 11 (nozzle holder), which is rubbed against the lower end of the guide 8 of the needle 7. The upper end of the guide is ground against the nozzle body 1. The nozzle holder 11, the guide 8 and the lower part of the housing 1 are fastened into a single sealed unit with a massive nut 9. The pins 5 ensure the coincidence of the sections of the cooling channels 12 of the fuel line 6. The nozzle 10 is fixed in the housing 11 by shrink fit, which ensures reliable fixation of the nozzle, the holes of which must have a strictly specified direction (the number of nozzles is two or three with the central position of the exhaust valve). Three or four spray nozzles have a diameter of 0.95 - 1.05 mm. To increase the service life of the elements of the needle - the stop, the upper part of the needle 7 is made in the form of a thickened head, and the stop 4 is made in the form of a sleeve with an increased diameter. The stop is pressed into the body of the body 1. The lift of the needle is h and \u003d 1 mm. The developed head of the needle made it possible to increase the diameter of the rod 3, which transmits to the needle the tightening force of the nozzle spring 2 (P zp), which increased the reliability of the spring-rod assembly.

Burmeister and Vine injectors are cooled, as a rule, with diesel fuel of an autonomous system.

Figure: 6.4.5

In recent years, all high-power low-speed marine diesel engines Burmeister and Vine, as well as promising diesel engines MAN - Burmeister and Vine are equipped with new nozzles with a unified design (see Fig. 6.4.5., 6).

The fundamental difference in this case is that the nozzle is uncooled. Normal operation of the nozzle at high heating temperatures of heavy fuel (105-120 ° C) is ensured due to its central supply through channel 14. This results in a symmetric temperature field and equal temperature gradients over the nozzle cross-section, and, consequently, equal working gaps in conjugated vapors ( in all other nozzle designs, where hot fuel and coolant are supplied to different sides of its body, an asymmetric temperature field is created).

The atomizer consists of a nozzle 10, a guide 8, a needle 7 and a check valve 17 inside the needle. The direction of the one-sided nozzle openings is ensured by fixing the nozzle with a pin 5 (the nozzle body 1 is fixed with its pin at the attachment point not shown in the drawing). The needle 7, having the shape of a glass at the top, perceives the force of tightening the spring 2 through the slider 13, into the cutouts of which the head of the spacer 15 with the central channel 14 enters. Inside the barrel of the needle, the spring 16 of the shut-off valve 17 and the fuel channel interface in the spacer 15 and in the valve 17 are located. The lower shoulder of the spacer 15 limits the valve lift (h to \u003d 3.5 mm), and the upper shoulder limits the needle lift (h and \u003d 1.75 mm).

The nozzle circulates heated fuel when the engine is not running (during preparation for start-up and during forced stops at sea), as well as during the period between adjacent injections, when the plunger pusher roller rolls around the cylindrical part of the washer.

When the engine is parked, when the high pressure fuel pump is in the zero feed position (the filling and discharge cavities are connected), the fuel pump at a pressure of 0.6 MPa supplies fuel to the injection fuel line and the nozzle channel 14. "Since the spring 16 of the check valve 17 has a tightening of 1 MPa, the valve does not rise, and the fuel passes through a small hole 18 into the needle barrel and further upward to the drain. Thus, at a standstill of any length, the entire injection system will be filled with fuel of working viscosity. This is extremely important for the reliable operation of the fuel equipment.

When the engine is running during the active stroke of the plunger, the discharge pressure almost instantly raises the check valve 17, and the bypass hole 18 is closed. Fuel flows to the differential area of \u200b\u200bthe needle 7 and raises the needle.

At the end of the active stroke of the plunger, the entire discharge system is quickly unloaded through the working cavity of the pump, since there is no discharge valve in it. When the fuel pressure drops below the intake pressure P ap. Spring 2 sets the needle 7, and at a pressure below 1 MPa, the spring 16 lowers the check valve 17. The plunger pusher roller for a long time goes to the top of the washer, and the injection system is again pumped with fuel until the next active plunger stroke.

The considered feature of the new nozzle is a great advantage of the fuel equipment, since in any operating conditions it is constantly in the operating temperature regime, which is extremely important to guarantee reliability.

Practice has shown that during forced stops of ships at sea, during long standstills in readiness, as well as during prolonged modes of low speed and maneuvers, heavy fuel cools down along the entire injection line, its viscosity increases. In such cases, after starting the engine or with sudden load surges, the injection pressure can increase dramatically, and the hydraulic forces in the discharge line can reach dangerous levels. As a result, cracks may form in the high-pressure fuel pump housings and the walls of the injection fuel lines, breakthrough of their connections with the pump and nozzle (especially when these places are threaded).

For fuel equipment with cooled injectors, there are several solutions aimed at maintaining the temperature of the injection system under the aforementioned conditions: turning off cooling of the injectors, supplying steam to the cooling channels, installing steam "satellites" along the entire (or part) of the injection fuel line, etc. However, all these solutions are significantly inferior to the nozzle with a symmetric temperature field in terms of efficiency.

A positive factor in favor of uncooled nozzles is the fact that it eliminates the need to use a special cooling system (two pumps, a tank, pipelines, instrumentation and automation devices).

There are disadvantages, however. The design of the nozzle is complex, multi-part. There are nine lapping places, and special mandrels are required for lapping. In the fuel equipment, there is practically no pressure valve, since the shut-off valve 17 does not perform its functions: in the event of a hang-up of the nozzle needle, the fuel from the injection system is pushed out by the gas pressure in the cylinder shortly after the end of the active stroke of the plunger. Experience shows that the cylinder switches itself off in this case.

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Ministry of Education and Science, Youth and Sports of Ukraine

"Odessa National Maritime Academy"

Course work

Completed

Pisarenko A.V

Checked:

prof. Gorbatyuk V.S.

Odessa 2012

Introduction

Long-term practice has shown that on all types of vessels of the merchant and specialized fleet, we get an internal combustion engine as the main engines.

High efficiency in terms of specific fuel consumption, high effective efficiency, significant service life and reliable engine operation are the main reasons for the use of a diesel engine in the marine fleet.

Along with the frequently used complex, which consists of a piston engine, gas turbines and compressors, on transport ships with powerful diesel installations. Most of the time, operating in a constant full load mode at the crossings between ports, a combined type scheme with the utilization of the heat of exhaust gases in the GTN is widely used. and in a waste heat recovery boiler, which significantly improves the engine's economy. If the steam of the utilization boiler is sufficient, a turbine generator is additionally installed, which provides the ship with electricity on the go, which allows saving fuel for the operation of the diesel generator.

Such diesel installations are equipped with means of remote control, systems and devices for continuous monitoring of the operating parameters of the temperatures of critical engine components of the coolant and oil, alarm protection systems with a record of all parameter shutdowns from the permissible limits on the control tape.

At present and in the near future, the main direction of the development of a marine diesel structure is to improve the working process of the engine aimed at increasing the efficiency in fuel and oil consumption, deep utilization of the heat of exhaust gases and cooling water, increasing the reliability of diesel engines in all operating modes, and improving the design and application. , better materials.

On the ships of the transport and specialized fleet, we will be widely used by leading diesel - construction companies, including: Burmeister and Vine (Denmark), MAN (FRG), Sulzer (Switzerland), Buryansk Motor-Building Plant " (Russia).

To complete the course project as a prototype engine, use the engine of the company "Burmeister and Vine" brand 5DKRN 62/140

1. Engine design data

The engine is two-stroke, with direct-flow valve blowing, crosshead, reversible, blown, right-hand rotation, with 8 cylinders and an aggregate power of 10,000 hp. from.

Purge System When the engine is running in reverse, the exhaust valve opens at 83 BCM. and closes at 63 A.M. Gas turbine engine inflated.

The purge system for forward travel has the following valve timing. Exhaust valve opening occurs at 89 BCM. closing at 57 A.M. Exhaust valve opening angle at 146 purge ports at 76 crankshaft rotations.

Air is supplied to the cylinder by a centrifugal blower through a finned tubular air cooler, a common welded receiver and under the piston cavities.

The fuel supply system of the engine is arranged as follows. The fuel pump is a piston, two-cylinder, with a discharge pressure of 3-4 MPa. It is driven by a crank at the nose end of the crankshaft. Fine filters - with thin felt cartridges.

High pressure pump - spool type, with end-of-flow adjustment. The maximum injection pressure is 600 kPsm. The plunger has a diameter of 28 mm and a stroke of 42 mm. Cam washer - symmetrical profile, consisting of two halves.

The closed injector is fuel-cooled. Force opening pressure 220 kPsm. The flat-end needle has a 0.7 mm lift and the nozzle has three 0.67 mm holes.

A diesel fuel cooler is located on the front end of the frame, and a fuel heater with a thermostat for the heavy fuel system.

Cylinder cooling system, exhaust valve - closed, double-circuit, driven by electric motors.

Fresh water is supplied to the cylinders under pressure!, 8 atm. from the main and, passing through the covers and the body of the exhaust valves, is discharged at a temperature of 6065 ° C through the branch pipes into the main. Outboard water for cooling air coolers is supplied under a pressure of 0.8 atm. and is discharged at a temperature of 40-45 ° C through pipelines.

The circulating lubrication system is serviced by pumps driven by an electric motor. Oil for the crank mechanism, thrust mechanism drive compartment, drive compartment, thrust bearing and exhaust valve drive is supplied under a pressure of 1.8 atm. on the highway.

The cylinder liner is made of alloy cast iron and has 18 blow-out ports 9.8 mm high with a total of 1008 mm. In the horizontal plane, the windows have a tangential direction. The sleeve is sealed along the jacket by lapping the supporting surfaces at the top, and one red copper band at the bottom. The lubricant is supplied to the mirror of the bushing above the blow-out windows through two nipples with ball non-return valves. The cylinder cover made of heat-resistant alloy steel is sealed along the end of the sleeve by lapping, the cover contains an exhaust valve with an average diameter of 250 mm at a stroke of 66 mm, two nozzles, a safety valve and an indicator valve. From the cylinder to the cover, the cooling water passes to two nozzles and through two nozzles from the cover to the body of the exhaust valve the piston - the engine is composite. The alloy steel head houses three top o-rings 10 mm high and 17 mm wide. The short guide is made of alloy cast iron.

A welded displacer and radial holes in the cylindrical part of the piston crown provide better heat transfer from the walls to the oil. The oil is supplied through a tube. A 170mm diameter carbon steel rod is flanged to the piston head via a guide using studs. The rod is connected to the crosshead crossbar by the end annular surface by means of a guiding cylindrical shank with a gull. In the lower part of the stem, the oil is supplied by a tube sealed with a bushing separating the supply cavity from the drain. The cast iron multi-piece stem packing has two scraper and two o-rings.

The crosshead of the engine is double-sided, with 4 cast steel sliders, which are studded to the highlanders of a forged steel cross member. The working surfaces of the sliders are filled with babbitt. Connecting rod with detachable head and ball bearings made of cast steel and cast in babbit. The head bearings with a diameter of 280 mm and a width of 170 mm have two connecting rod bolts each, and a Motylev bearing with a diameter of 400 mm with a width of the upper half of 240 mm and the width of the lower bearing head 170 mm have two full connecting rod bolts. The bolts are made of alloy steel, do not have centering belts. The connecting rod rod with a diameter of 190mm with a rigid, fork-free head is hollow, made of alloy steel. The connecting rod and bearings have holes for supplying oil from the crank bearing to the head ones.

The crankshaft is composite: frame and crank journals made of carbon steel have a diameter of 400 mm, a length of 254 mm; cast steel shanks 660 mm wide and 185 mm thick; hollow necks are closed at the ends of the cover and on screws. According to the conditions of lubrication and strength, the radial holes in the crank journals are displaced from the plane of the crankshaft.

For engine balancing conditions, some of the cheeks are cast with counterweights. The thrust bearing of the engine is single-comb, with six swinging thrust segments for forward and reverse travel, which are located in 2 sectors, and are fixed in a welded housing with two covers. The barring device includes an electric motor connected to the wheel on a thrust shaft through two worm gears.

From the pallet at a temperature of 45-52 ° C, the oil is discharged into a waste tank.

The bushings of the working cylinders are lubricated from lubricators with a camshaft drive. The turbocharger bearings are lubricated from a separate system with a gear pump driven by an electric motor.

The drive of the camshaft of the fuel pumps and the camshaft of the exhaust valves is made by a single frame chain with a pitch of 89 mm. An indicator drive for each cylinder, consisting of a lever and a crown rod, receives movement from the eccentric along the exhaust camshaft. The camshaft of the spool air distributor in block design has a chain drive from the camshaft, fuel pumps.

The engine control post has a reversible and fuel handle. The engine is started by compressed air pressure 30 kg / cm with simultaneous fuel supply. The change in the direction of rotation of the engine shaft is carried out after reversing the air distributor automatically to start-up states by turning the crankshaft relative to the locked camshafts of the fuel pumps and exhaust valves.

In place at the control station are installed: a mechanical tachometer, an indicator of the direction of rotation, a total counter of engine revolutions, pressure gauges for oil, fuel, purge air, fresh and seawater, oil and exhaust gases. There are also remote tachometers for each gas turbocharger and a shut-off starting air flywheel at the control station.

The base frame, the bed with A-shaped blades, the stand consisting of two sections, and the frame of the drive compartment are of a welded structure.

The frame is connected to the bed by short bolts. Double-sided cast-iron parallels are fixed on the racks. The crankcase compartments are closed by removable steel shields with inspection windows and spring-loaded safety lamellas. The cylinder block consists of separate large jackets. To increase the water velocity in the cooling cavity, the flow area is reduced - especially in the area of \u200b\u200bthe upper part of the sleeve. The shirts have hatches for inspecting the cooling cavities. Short alloy steel anchors connect the cylinder jackets through a stand to the upper reinforced crankcase plate. Ties are located in jackets connector cavities.

2. Thermal calculation

The main task of the verification calculation is to estimate the parameters of the operating cycle in the operating mode of the engine. In this case, the values \u200b\u200bof the parameters controlled in operation with the help of standard devices are used.

2.1 Filling process

Compressor inlet air pressure.

P0? \u003d P0-Drf kgf / cm (1)

Where, P0 is barometric pressure, 720 mm Hg (given)

Pfd-pressure drop across the air filters GTK, 93 mm wc (set)

1mm Hg \u003d 0.00136 kgf / cm

1mm water column \u003d 0.0001 kgf / cm

P0? \u003d 720 * 0.000136-95 * 0.0001 \u003d 0.96

Air pressure after compressor

рк \u003d рs + Дх kgf / cm (2)

where, ps is the air pressure in the receiver (after the refrigerator), 1.42 kgf / cm

Дх - pressure drop across air coolers 250 mm water column (set)

pk \u003d 1.6 + 140 * 0.0001 \u003d 1.614

Compressor pressure ratio

p k \u003d pk / P0? (3)

p k \u003d 1.614 / 0.96 \u003d 1.68

Cylinder pressure at the end of filling

For two-stroke engines with direct-flow valve blowing and from the loop-loop Sulzer company.

pa \u003d (0.96-1.05) ps (4)

For the calculation we take 1.01

Ra \u003d 1.01 * 1.6 \u003d 1.616

Charge air temperature in the receiver (after the refrigerator)

Tk \u003d T? c * pk ^ (nk-1 / nk) K (5)

where is T? c \u003d T0 \u003d 273 + t0- air temperature at the compressor inlet

nk is the compression polytropic index in the compressor. For centrifugal pumps with a cooled casing nk \u003d 1.6-1.8. For the calculation we take nk \u003d 1.7

T? c \u003d 273 + 35 \u003d 308

Tk \u003d 308 * 1.616 ^ (1.7-1 / 1.7) \u003d 375.76

Air temperature in the receiver

Тs \u003d 273 + tz.v. + (15-20) K (6)

where tz.w - seawater temperature (tz.w \u003d 17С)

Тs \u003d 273 + 10 + 17 \u003d 300

Air temperature in the working cylinder, taking into account heating (Dt) from the walls of the combustion chamber.

Т? S \u003d Тs + Дt К (7)

Where Дt \u003d 5-10С for the calculation we take Дt \u003d 7С

Temperature of air / residual gas mixture at the end of filling

Ta \u003d (T? S + r Tr) / 1 + r K (8)

where r is the residual gas coefficient. For two-stroke with direct-flow valve blowdown r \u003d 0.04-0.08.

For the calculation, we take r \u003d 0.06

Tr-temperature of residual gases Tr \u003d 600-900 For calculation we take Tr \u003d 750

Ta \u003d (307 + 0.06 * 750) /1+0.06\u003d332

Filling ratio related to effective piston stroke

s n \u003d (/ -1) * (pG / ps) * (Ts / Ta) * (1/1 + r) (9)

where is the value of the compression ratio. For low-speed engines \u003d 10-13. For calculation we take \u003d 12

s n \u003d (12 / 12-1) * (1.616 / 1.6) * (301/332) * (1/1 + 0.06) \u003d 0.94

Filling ratio related to the full stroke of the piston.

h? n \u003d s n (1- s) (10)

where s is the relative lost piston stroke. For motors with direct-flow valve blowing s \u003d 0.08-0.12. For the calculation we take s \u003d 0.1

h? n \u003d 0.94 (1-0.1) \u003d 0.85

Full cylinder displacement.

V? S \u003d рD ^ 2/4 * S m

V? S \u003d 0.785 * 0.62 ^ 2 * 1.4 \u003d 0.24

Density of charge air

s \u003d 10 ^ 4 * Ps / R * Ts kg / m

where R \u003d 29.3 kgm / kg deg (287 J / kg rad) -gas constant

s \u003d 10 ^ 4 * 1.6 / 29.3 * 301 \u003d 1.8

Air charge referred to the total working volume of the cylinder.

(kg / cycle) (11)

where d is the moisture content of the air, determined depending on temperature and relative humidity (Table 1)

2.2 Compression process

For low- and medium-speed engines n1 \u003d 1.34 + 1.38. For the calculation we take 1.36

First approximation n1 \u003d 1.36

Second approximation n1 \u003d 1.377

Accept n1 \u003d 1.375

Pressure at the end of the compression process.

Pc \u003d p a * kgf / cm (13)

Pc \u003d 1.616-12 "377 \u003d 49.48

Temperature at the end of the compression process.

Tc \u003d Ta * K (14)

Tc \u003d 333 -12 0 - 377 \u003d 849.7

For reliable self-ignition of fuel, Tc must be at least 480+ 580 "C or 753 +853" K.

2.3 Combustion process

Maximum combustion pressure.

p: \u003d pc * l kgf / cm (15)

where, l \u003d Pz / Pc - the degree of pressure increase. For low-speed engines l \u003d 1.2 / 1.35. For the calculation, we take l \u003d 1.3

p z \u003d 49.48 * 1.3 \u003d 64.32

The maximum combustion temperature is determined from the combustion equation, which can be reduced to a form.

ATz 2 + BTz -C \u003d o

Solving the quadratic equation, we get:

where, z is the coefficient of heat utilization by the time of the beginning of expansion; For low-speed engines z \u003d 0.80 0.86.

For the calculation we take Жz \u003d 0.83

Net calorific value

Qн \u003d 81С + 300Н -26 (0-S) - 6 (9 Н + W) kcal / kg, (17)

where, С, Н, 0, W, - the content of carbon, hydrogen, sulfur and water% For the calculation we are given the F-12 naval fuel oil. From table 2 we take C \u003d 86.5%, H \u003d 12.2%, S \u003d 0.8%, O \u003d 0.5%, Qn \u003d 9885 kcal / kg.

The amount of air theoretically required for complete combustion of 1 kg of fuel:

in volume units

Lo \u003d kmol / kg (18)

in units of mass

Go \u003d Lo * mo kg / kg (19)

where mo \u003d 28.97 kg / kmol is the mass of 1 kmol of air

G0 \u003d 0.485 * 28.97 \u003d 14

The amount of air actually supplied to the cylinder for complete combustion of 1kg of fuel:

in volume units

L \u003d d * L0 kmol / kg (20)

in units of mass

G = d* G0 kg / kg (21)

where d- coefficient of excess air during fuel combustion. For low-speed engines d\u003d 1.8 + 2.2. For the calculation we accept d=2.

L \u003d 2 * 0.485 \u003d 0.97

The theoretical coefficient of molecular change. (22)

Actual coefficient of molecular change.

Average molar isochoric heat capacity of a mixture of fresh air charge and residual gases at the end of the compression process.

(mS v) s cm \u003d (mCv) s car \u003d 4.6 + 0.0006 * Tc kcal / kmol deg (24)

(mS v) s cm \u003d 4.6 + 0.0006-849.7 \u003d 5.11

Average molar isobaric heat capacity of a mixture of "clean" combustion products with excess air and residual gases remaining in the cylinder after combustion.

Substitute the obtained value into equation (25).

2.4 Expansion process

Pre-expansion ratio.

The degree of subsequent expansion.

The average exponent of the expansion polytropic z2 is determined by the method of successive approximation from the equation:

Since we do not need great accuracy when calculating h2 according to formula (28), the value of h2 for low-speed engines is h2 \u003d 1.27 / 1.29, we choose h2 \u003d 1.28

Expansion end pressure. (29)

рb \u003d 64.32 * 1 / 6.59 1 "28 \u003d 5.75

Temperature at the end of the expansion. (thirty)

2.5 Exhaust gas parameters

Average gas pressure behind the cylinder outlet.

pr- \u003d ps-zhn kgf / cm (31)

where wn \u003d (0.88 / 0.96) is the coefficient of pressure loss during purging in the inlet and outlet organs. For the calculation we take wn \u003d 0.92.

Pr \u003d 1.6 * 0.92 \u003d 1.47

Average gas pressure before turbines

PT \u003d Pr * wr kgf / cm (32)

where, lg \u003d 0.97 + 0.99) is the coefficient of pressure loss during blowing in the outlet from the cylinder to the turbines. For the calculation we take wr \u003d 0.98.

PT \u003d 1.47 * 0.98 \u003d 1.44

Average temperature of gases in front of turbines. (33)

where, qg \u003d (0.40 + 0.45) is the relative heat loss with exhaust gases in front of the turbines. For the calculation, we take qr \u003d 0.43. c a - blowdown coefficient. For two-stroke with GTN tsa \u003d 1.6 / 1.65. For the calculation we take ts \u003d 1.63.

С Р г \u003d (0.25 / 0.26) - average isobaric heat capacity of gases. For the calculation we take Сpr \u003d 0.26.

2.6 Energy and economic indicators of the engine

The average indicator pressure of the theoretical cycle related to the useful piston stroke, according to the Masing-Sinetsky formula.

Pн \u003d kgf / (34)

The average indicated pressure of the theoretical cycle, referred to the full stroke of the piston.

Average indicated pressure of the estimated valid cycle.

Where, is the rounding factor of the diagram. For two-stroke with single-flow valve blowdown. For the calculation we accept

P \u003d 12.14 * 0.97 \u003d 11.77

Indicated engine power in operating mode.

Where, z is the tact factor. For two-stroke engines z \u003d 1

Engine rated power.

Where, the mechanical efficiency of the motor at nominal mode. For two-stroke

For the calculation we accept

The mechanical efficiency of the motor is in the operating mode.

Average effective pressure in operating mode.

Pc \u003d 11.77-0.92 \u003d 10.82

Effective engine power in operating mode.

Nc \u003d Ni * zm HP (41)

Nс \u003d 7439 -0.92 * 6843.88

Specific indicator fuel consumption in operating mode.

kg / hp h. (42)

Specific effective fuel consumption in the operating mode.

kg / hp h. (43)

Fuel consumption per hour in operating mode.

Cyclic fuel supply in operating mode.

Indicator efficiency in operating mode.

Effective efficiency in operational mode.

h \u003d 0.49-0.92 \u003d 0.45

2.7 Byindicator diagram structure

We take the volume of the cylinder Va on a scale equal to the segment A \u003d 120mm.

Plot the found volumes on the abscissa axis. Determine the scale of ordinates:

mm / kgf / cm

B - the length of the segment is 1.3-1.6 times less than segment A. We accept B by 1.5 times. B \u003d 80mm.

We determine the intermediate volumes and the corresponding compression and expansion pressures. The calculation is performed in tabular form.

Using the data from the table, we plot characteristic points on the diagram and build polytropes of compression and expansion. The plotted diagram is theoretical (calculated).

To construct the proposed indicator chart, round off the corners of the theoretical chart at points C. Z and Z. The actual release process begins at point b, the position of which on the chart is found using the F.A. Brix.

The radius of the crank to the scale of the Drawing.

Brix Correction.

where l is the simplest crank mechanism. We take l \u003d 0.25. The angle (q of the beginning of the exhaust valve opening is taken equal to 90 P.K.V. to N.M.T.

From m. O, using a protractor from the abscissa axis, we postpone the angle (q, draw a vertical line to the intersection with the expansion curve and find the position of point b.\u003e Points b and a are connected by a curve.

Table 1

3. Dynamic calculation of the engine

3. 1 Problems of kinematic and dynamic analysis of motion crookedspike-connecting rod mechanism (KShM)

The parts of an internal combustion engine during its operation are under the influence of various forces. The most important unit of the internal combustion engine is the KShM.

The following forces act in the engine KShM during its operation:

1) Gas pressure on the piston:

where: p g - gas pressure in the engine cylinder, MPa;

F- piston crown area from () ;

2) Inertia of translationally moving masses

where: m pd is the mass of progressively moving parts, kg;

a - piston acceleration m / ;

3) The forces of gravity of translationally moving masses:

4) Friction forces.

They do not lend themselves to precise theoretical definition and are included in the mechanical losses of the engine. The forces of weight (gravity) are small compared to other forces and therefore they are usually not taken into account in approximate calculations.

Total driving force:

Since we do not yet know the mass of the parts of the designed internal combustion engine, then the specific forces per unit of the piston per cm 2 (m 1) are used for the calculation. In this way:

3. 2 Determination of driving force

Construction method

The indicator diagram, built on the basis of the calculation of the workflow, gives the dependence of p r on the piston stroke. For further calculations, it is necessary to relate the forces acting on the internal combustion engine with the angle of rotation of the crankshaft.

Parallel to the abscissa axis of the indicator diagram, constructed based on the results of calculating the parameters of the internal combustion engine cycle, a straight line AB is drawn. The segment AB is divided by point O in half and from this point with the radius OA they describe a semicircle. From the center of the circle (point O) in the direction of NMT, the segment 00 1 \u003d 0.5g is laid off - the Brix correction, where r \u003d OA (to maintain the scale).

Permanent KShM;

where: R is the radius of the crank;

L is the length of the connecting rod between the bearing axles.

The value of I is taken within the following limits:

For slow speed crosshead motors 1 / 4.2 - 1 / 3.5;

In our case, we take X \u003d 0.25.

From O1 (Brix pole), describe the second circle (larger than the first) with an arbitrary radius and divide it into equal parts (usually every 5-15 °). From the Brix pole, rays are passed through the division points of the second circle.

To build a diagram, we take -p.c.v.

For an expanded indicator diagram P g \u003d (a) we take the scale along the ordinate M ord \u003d 10 mm. I MPa and along the abscissa M abts \u003d 20 degrees, 1 cm.

Because the adopted scale along the ordinate is 1.5 times smaller than the scale of the p - V diagram, therefore, the ordinates taken from it are divided by 1.5 and set aside for the corresponding. and on the diagram P r \u003d (a).

To plot the diagram of inertia forces P g \u003d ѓ (a), we take t pd \u003d 7000

The diagram of the moving forces is constructed by summing the ordinates of the diagrams P, \u003d / (a) and P s \u003d / (a), taking into account their signs.

3. 3 Plotting a shear force diagram

1. Method of plotting a diagram for one cylinder:

We build the diagram of tangential forces on the same scale as the diagram of moving forces: M abts \u003d 20 deg / cm, M ord \u003d 10 mm / MPa.

We draw up table 3. Trigonometric function : we determine for \u003d 1/4 from table 2; R d - based on Fig. 3 in mm.

The tangential force (tangential) is determined by the formula:

Ra is the driving force (see above).

Trigonometric function, which is determined according to table 3, depending on a.c.c. and:

Angle of deviation of the connecting rod axis from the cylinder axis.

Certain values \u200b\u200b-, P 0, P K are summarized in tables 3 and 4, on the basis of which a diagram of shear forces for one cylinder is constructed (Fig. 3a).

Table 3


Working stroke (extension)

Table 4. Calculation of the forces of inertia of translationally moving masses P and \u003d ѓ (a) MPa

	Engine 5 DKRN 62/140

2. A method for constructing a summary diagram of tangential forces.

The summary diagram of tangential forces is built on the same scale as the diagram of tangential forces of one cylinder (Fig. 36)

Determine the specific resistance force

And the average tangential force

The scale of the ordinate axis \u003d 10 mm / MPa, therefore

Chart construction error

What is permissible

3. 4 Flywheel calculation

marine engine connecting rod flywheel

To calculate the flywheel, at the beginning, the values \u200b\u200bof uneven rotation of the crankshaft are set:

Determine the scale of the area of \u200b\u200bthe summary chart

Regarding

We plan the area of \u200b\u200bexcess work:

We determine the specific excess work:

Then the redundant work:

where: R is the radius of the crank (m); moment of inertia of moving parts of the engine and flywheel:

The moment of the moving parts of the internal combustion engine:

We calculate the moment of inertia of the flywheel:

4 \u003d 1483.08 (kg /)

We accept the reduced diameter of the handwheel :

where: S - overall dimensions; prototype engine, m; Then:

We calculate the mass of the rim:

Determine the total mass of the flywheel:

0.88 - \u003d 0.8 - 7 3 5.21 \u003d 572.2 (kg)

Determine the dimensions of the flywheel rim from the expression:

where: R- density. For steel p = 7800 (kg / m) . B and h - respectively, the width and thickness of the rim, m. We take the thickness of the rim equal to h \u003d 0.2 m, then:

Maximum flywheel diameter:

2.88 + 0.04 \u003d 2.92 (m)

Checking the peripheral speed of the flywheel rim:

The obtained value is acceptable for the designed engine.

Listliterature

1. Method of indication

2. Mikheev V.G. "Main ship power plants". Methodical recommendations for course design for the nautical and arctic schools of Minimorflot. M., CRIL "Morflot", 1981, 104s.

3. Gogin A.F. "Marine diesels", the basics of theory, design and operation. Textbook for river schools and technical schools of water transport: 4th ed. Revised And supplemented - M., Transport, 1988.439s.

4. Lebedev ON "Ship power plants and their operation". Textbook for universities vodn. transport - M .: Transport, 1987 - 336s.

5. A.A. Fock, Yu.D. Mitryushkin "Maintenance of the vessel on the voyage"

6. A. N. Neelov "Rules of technical operation of ship technical equipment", Moscow 1984. - 388p.

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