Design of diesel engine D-245
Diesel D-245 and its modifications are a four-stroke piston four-cylinder internal combustion engine with an in-line vertical cylinder arrangement, direct injection of diesel fuel and compression ignition.
The main assembly units of a diesel engine are: cylinder block, cylinder head, pistons, connecting rods, crankshaft and flywheel.
To ensure high technical and economic performance of the diesel engine, turbocharging with intermediate cooling of the charge air is used in the intake system.
The use of a turbocharger with adjustable boost pressure in the supercharging device allows for improved throttle response on a diesel engine, ensured by increased torque values at low crankshaft speeds.
Technical characteristics of diesel engine D-245.12
Diesel type - Four-stroke turbocharged diesel
Method of mixture formation - Direct fuel injection
Number of cylinders - 4
Cylinder arrangement - In-line, vertical
Cylinder operating order 1 - 3 - 4 - 2
Cylinder diameter - 110 mm
Piston stroke 125 mm
Cylinder displacement - 4.75 l
Direction of rotation of the crankshaft - Right
Compression ratio (calculated) - 15.1
Rated power kW(hp) 80(108.8)
Rated speed 2400 min -1
Maximum torque 350 Nm
Rotation speed at maximum torque value, min -1 1300-1700
Minimum stable idle speed, min -1, no more than 800±50
Specific fuel consumption according to the external speed characteristic g/kWh:
- - minimum – 218;
- - at rated power - 245
Hourly fuel consumption at rated power - 19.6 kg/h
Hourly fuel consumption at minimum stable idle speed, kg/h, no more than - 1.5
Nominal installation angle of fuel injection advance, degrees. before TDC - 19 ±1
Total oil consumption (including replacement) as a percentage of fuel consumption, no more than - 1.3
Oil consumption for waste according to GOST 18509-88 as a percentage of fuel consumption, no more than - 0.5
Oil pressure in the main oil line at the nominal operating mode of the diesel engine is 0.25-0.35 MPa
Weight of dry diesel engine - 500 kg
Overall dimensions mm - 1011.5x702.0x1080.5
The cylinder block is the main body part of a diesel engine and is a rigid cast iron.
Four removable sleeves made of special cast iron are installed in the vertical bores of the block.
The liner is installed in the cylinder block along two centering belts: upper and lower.
In the upper belt the liner is secured with a collar, in the lower belt it is sealed with two rubber rings placed in the grooves of the cylinder block.
Coolant circulates between the walls of the cylinder block and the liners.
The end walls and transverse partitions of the cylinder block in the lower part have bosses designed to form supports for the crankshaft. Covers are installed on these tides.
The bosses together with the covers form beds for the main bearings.
The beds for the main bearing shells are bored from one installation complete with the main bearing caps, so the caps cannot be swapped.
The cylinder block has a longitudinal oil channel, from which oil flows through transverse channels to the crankshaft main bearings and camshaft bearings.
The design of the diesel cylinder block includes five camshaft bearings.
In the upper part of the second and fourth crankshaft supports there are nozzles that serve to cool the pistons with a stream of oil.
On the outer surfaces of the cylinder block there are machined mating surfaces for attaching the oil filter, water pump, coarse and fine fuel filters, distribution board and rear sheet.
The cylinder head is a cast iron, in the internal cavities of which there are inlet and outlet channels closed by valves. Inlet channels - with screw profile
To ensure heat removal, the cylinder head has internal cavities in which coolant circulates.
The cylinder head has inserted valve seats made of heat-resistant and wear-resistant alloy
On the top of the cylinder head are mounted struts, a rocker arm axle with rocker arms, a head cover, an intake manifold and a cover cap that closes the valve mechanism
On the left side (from the fuel pump side) there are four injectors installed in the head, and on the right side the exhaust manifold is attached to the head
To seal the connector between the head and the cylinder block, a gasket made of asbestos-free fabric reinforced with perforated steel sheet is installed
The holes in the gasket for the cylinder liners are edged with sheet steel.
When a diesel engine is assembled at the factory, the cylinder holes of the gasket are additionally edged with fluoroplastic split rings.
The main parts of the crank mechanism are: crankshaft, pistons with piston rings and pins, connecting rods, main and connecting rod bearings, flywheel.
The crankshaft is steel, has five main and four connecting rod journals.
The axial force of the crankshaft is perceived by four bimetallic half-rings or half-rings made of aluminum alloy installed in the bores of the cylinder block and the fifth main bearing cover.
To reduce the load on the main bearings from inertial forces, counterweights are installed on the first, fourth, fifth and eighth cheeks of the crankshaft.
The crankshaft is sealed with cuffs at the front and rear.
A timing gear (crankshaft gear), an oil pump drive gear, a water pump and generator drive pulley are installed on the front end of the shaft. The flywheel is attached to the rear flange of the shaft.
Piston is made of aluminum alloy. There is a combustion chamber at the bottom of the piston. The combustion chamber is offset relative to the piston axis.
The piston has three grooves in the upper part - compression rings are installed in the first two, and an oil scraper ring is installed in the third.
An insert made of special cast iron is poured under the groove of the upper compression ring. The piston bosses have holes bored out for the piston pin.
Piston rings are made of cast iron. The upper compression ring is made of high-strength cast iron and has the shape of an isosceles trapezoid in cross-section.
The second compression ring is conical. On the end surface of the lock, the compression rings are marked “Top” (“TOP”). Box type oil scraper ring with spring expander.
Piston pin is hollow, made of chromium-nickel steel. The axial movement of the pin in the piston bosses is limited by retaining rings.
Connecting rod - steel, I-section. A bushing is pressed into its upper head. To lubricate the piston pin, there are holes in the upper end of the connecting rod and the bushing.
Boring of the bed in the lower head of the connecting rod for the liners is done in the assembly with the cover. Therefore, it is not allowed to change the connecting rod caps
The connecting rod and the cap have the same numbers stamped on their surfaces. In addition, the connecting rods have weight groups based on the mass of the upper and lower heads.
The designation of the mass group is applied to the end surface of the upper head of the connecting rod. The diesel engine must have connecting rods of the same group installed.
Inserts of the main and connecting rod bearings of the crankshaft are made of bimetallic strip.
Diesel engines use main and connecting rod bearing shells of two sizes in accordance with the rating of the crankshaft journals.
For diesel repair there are also four repair sizes of liners.
The flywheel is made of cast iron and is bolted to the crankshaft flange. A steel ring gear is pressed onto the flywheel.
The distribution mechanism consists of a camshaft, intake and exhaust valves, as well as parts for their installation and drive: pushers, rods, rocker arms, adjusting screws with nuts, plates with crackers, springs, struts and rocker arm axles.
The camshaft is five-bearing, driven by the crankshaft through the distribution gears.
The camshaft bearings are five bushings pressed into the block bores.
The front bushing (on the fan side) is made of aluminum alloy and has a thrust collar that holds the camshaft from axial movement; the remaining bushings are made of special cast iron.
Pushers are steel. The working surface of the pusher plate is overlaid with bleached cast iron and has a spherical surface of large radius (750 mm).
As a result of the fact that the camshaft cams are made with a slight inclination, the pushers perform a rotational movement during operation.
Push rods are made of steel rod. The spherical part that goes inside the pusher and the rod cup are hardened.
The valve rocker arms are made of steel and swing on an axis mounted on four racks. The outer pillars are of increased rigidity.
The rocker arm axis is hollow and has eight radial holes for supplying oil to the rocker arms. The movement of the rocker arms along the axis is limited by spacer springs.
Inlet and exhaust valves are made of heat-resistant steel. They move in guide bushings pressed into the cylinder head.
Each valve closes under the action of two springs: external and internal, which act on the valve through a plate and crackers.
The sealing collars installed on the valve guides prevent oil from entering the diesel cylinders and exhaust manifold through the gaps between the valve stems and the valve guides.