Engine of small-class passenger engine -PZ, Drawings

Contents

Introduction

1 Select additional source data

1.1 Selection of design parameters

1.2 Selection of fuel parameters

1.3 Determination of FA initial parameters

1.4 Selection of parameters of indicator diagram

2 Calculation of the working cycle

2.1 Intake Process

2.2 Compression Process

2.3 Combustion process

2.4 Expansion and Release Processes

2.5 Engine indicators

2.6 Effective engine performance

2.7 Construction of indicator diagram

3 Calculation of engine dynamics

3.1 Determination of parameters of the calculation model

3.2 Calculation of forces acting between KSM parts

3.3 Construction of polar diagram of forces S and rsh

3.4 Determination of engine indicator moment

3.5 Engine balancing

4 Design and calculation of main units and systems

4.1 Piston group

4.1.1 Design of piston group parts

4.1.2. Calculation of piston group parts

4.2 Connecting rod group

4.2.1 Design of connecting rod group parts

4.2.2 Calculation of connecting rod group parts

4.3 Crankshaft Group

4.3.1 Design of crankshaft group parts

4.3.2 Calculation of crankshaft group parts

4.4 Housing Parts

4.4.1 Structure of housing parts

4.4.2 Calculation of housing parts

4.5 Gas distribution mechanism

4.5.1 Design of the GPM

4.5.2 Calculation of parts of the hydraulic engine

4.6 Lubrication system

4.7 Cooling system

5 Technical and economic evaluation of the designed engine

5.1 Construction of AHS engine

5.2 Selection of parameters for engine quality determination

5.3 Analysis of parameters of designed engine

Conclusion

List of sources used

Applications

Sheet of project (19060165.DR16KP.00000VP)

Introduction

In this course design, the engine of a small car with positive ignition is designed. The rated power of the designed engine is 52 kW at a crankshaft speed of 5100 rpm. An additional requirement is easy start-up at low temperatures (LPT).

1.2 Selection of fuel parameters

Average elemental composition and molecular weight of fuel (gasoline AI92): C = 0.855, H = 0.145 and μt = 120 kg/kmol. The lowest combustion heat of gasoline is Hu = 44,000 kJ/kg.

1.3 Determination of FA initial parameters

Since the designed engine will work without pressurization, air enters the cylinder from the atmosphere. In this case, when calculating the engine operating cycle, the inlet pressure is taken as P0 = 0.1 MPa, and the temperature T0 = 293 K.

The excess air ratio is set based on the following considerations. Modern engines are equipped with multi-chamber carburetors, which provide an almost ideal composition of the mixture in terms of speed characteristics. The possibility of using a carburetor with an enrichment system and an idling system for the calculated engine makes it possible to obtain both a power and an economical composition of the mixture with appropriate adjustment. The value of the excess air factor α for petrol engines [1, c.21] is within the limits of 0.80... 0.96. I select α = 0.96 for the designed engine.

3.5 Engine balancing

The calculated four-cylinder single-row engine has an operating order of 1-2-4-3, the intervals between the flashes are equal to 180˚ and a crankshaft with cranks located at an angle of 180˚.

Forces of inertia of the first order and their moments at the specified arrangement of cranks are mutually balanced: ΑPJ1 = 0 and ΑMJ1 = 0. The second order inertia forces for all cylinders are equal and directed in one direction. Their equilibrium ΟRJP = 4RJP = 4mJR.

The second-order inertia forces can only be balanced with additional shafts. The total moment of these forces is zero: ΑMJII = 0. Centrifugal inertia forces for all cylinders are equal and are directed in pairs in different directions. The equilibrium of these forces and the moment are zero: ΑKR = 0 and ΟMR = 0.

4.2 Connecting rod group

4.2.1 Design of connecting rod group parts

For the designed engine, the connecting rod is made of high-quality carbon steel 45G2 (GOST 454371) by stamping. Since the piston pin of the floating type, a thin-walled bushing made of bronze BR OTS 4-4-2.5 (GOST 501774) is pressed in the upper head of the connecting rod. A hole is provided in the piston head wall of the connecting rod to lubricate the piston pin (see Figure 4.8). The rod of the connecting rod has an I-section, which provides more rigidity. Crank head of connecting rod is made detachable, with parting plane perpendicular to connecting rod axis. Two bolts attach the edge of the connecting rod crank head.

The bolts are made of 40X alloy steel because they are subjected to impact loads of inertia forces. The bolt nuts are made of the same material and are heat treated to increase hardness.

Thin-walled inserts are installed in crank head of connecting rod, high-quality BK2 babbit on lead base is used as antifriction layer.

In order not to entangle the connecting rod covers during assembly, on the connecting rod and its corresponding cover (on the side) there is a stamp of the cylinder number in which they are installed. When assembling, the numbers on the connecting rod and cover must be on one side.

Where the lower head of the connecting rod passes into the rod, there is an opening through which oil passes, lubricating the walls of the cylinder. Figure 4.6 shows the diagram of the connecting rod.

4.3 Crankshaft Group

4.3.1 Design of crankshaft group parts

The crankshaft is the most structurally complex and most stressed part of the engine, which receives periodic loads from the forces of gas pressure, inertia forces and their moments.

The crankshaft of the calculated engine is made of high-strength HF 60 - 2 cast iron (GOST 729370) full-support, i.e. with supports after each cylinder. The shaft is statically and dynamically balanced. The surfaces of the necks in order to increase their hardness and wear resistance are treated with TVH. Angle between cranks is 1800. All sliding surfaces of the shaft elbows have a high purity, which is achieved by superfinish processing - polishing after grinding. The shaft rotates in the main sliding bearings. Oil channels are provided in the crankshaft to provide lubrication of friction surfaces of the main and connecting rod bearings. Oil is supplied to the root necks from the common main line through channels in the walls of the upper half of the crankcase from the side of the low-loaded half of the bearing insert. From the main necks, it is led to the connecting rod necks through drilled channels. Axial fixation of shaft elbows at its thermal expansion relative to crankcase is performed by thrust rings and semi-rings.

4.5 Gas distribution mechanism

4.5.1 Design of the GPM

Gas distribution mechanism includes: camshaft, gear of its drive, sleeve, inlet and outlet valves, valve springs, guide bushings.

Valve distribution mechanism is upper valve with upper location of camshaft.

The camshaft is forged steel, has five supporting necks. Necks rest on bushings pressed into blocks from low-carbon tape filled with babbit. Profiles of inlet and outlet cams of shaft are the same.

To increase wear resistance, cams, support journals, fuel pump drive eccentric and oil pump drive gear made integral with shaft are subjected to surface hardening.

Camshaft is driven from crankshaft by gears with oblique teeth. A gear is put on the crankshaft, and a texolite gear with a cast-iron hub is put on the distribution shaft to ensure silent operation. Both gears have two threaded holes for extractor. Correctness of distribution phases is ensured by installation of gear by marks, which are aligned with risk at tooth cavity on textile gear. The cups are the same for all valves, steel.

We choose a scheme with two valves: inlet and outlet. Valves are made of heat-resistant steels: the inlet valve is made of chromosilicon, and the outlet valve is made of chromium-nickel-manganese with a nitrogen additive. More heat-resistant chromium-nickel alloy is additionally laid on working chamfer of outlet valve.

The inlet valve opens 17 ° to .m.t. and closes 43° after n.m.t. The outlet valve is opened 47 ° BC. and closes 13 ° after .m.t. said phases are valid at clearance between rockers and valves equal to 0.35 mm. Clearances are checked and installed on a cold (20 ° C) engine. With increased clearances, a knock of valves occurs, and with a decrease, the valve can loose fit to the seat and burn the valve. Valves operate in metal ceramic guide bushings, which are made by pressing with subsequent sintering of a mixture of iron, copper and graphite powders and processed finally after pressing into the head. The antifriction qualities of such bushings are high. To reduce the amount of oil sucked through the gaps between the bushing and the intake valve rod into the cylinder, an oil reflector cap made of oil-resistant rubber is put on the valve rod under the spring plate.

4.6 Lubrication system

The lubrication system serves to supply oil to all rubbing surfaces of the engine parts during its operation, as a result of which power losses on friction between the parts are reduced, and wear of the rubbing surfaces is reduced. In addition, the oil, passing between the friction parts of the engine, cools them and carries away the wear products.

Engine lubrication system combined: under pressure and spraying. Main and connecting rod bearings, camshaft supports, gear sleeves are lubricated under pressure. Cylinder walls, pistons with piston rings, piston pins in piston bosses and valve rods in their guide bushings are lubricated with oil flowing out of clearances and sprayed with moving parts.

The lubrication system includes: an oil pump, a intake nozzle with a filter mesh, attached to the pump housing, a full-flow oil filter installed on the left front side of the engine; reduction valve of oil pressure, built into receiving branch pipe, sensors of indicator and control lamp of oil pressure. Oil pump is driven by pair of gears with screw teeth. Oil is supplied to the central support of the camshaft through channels drilled in the cylinder block, in the cylinder head and in the bearing housing of the camshaft. Cylinder head gasket has copper-edged hole through which oil passes from block channel to head channel. Each insert of the first, second, fourth and fifth main bearings has two holes through which oil enters annular grooves on inner surfaces of inserts. From the grooves part of the oil goes to lubricate the main bearings, and the other part through the channels drilled in the journals and cheeks of the crankshaft to the connecting rod bearings, and from them through the holes in the lower heads of the connecting rods the oil jet enters the mirror of the cylinders. Oil passed to the central support of the camshaft through an annular recess in the support journal enters the main channel of the camshaft, and from the channel through holes in cams and support journals to the working surfaces of cams, levers and shaft supports. The remaining parts are lubricated by spraying and gravity.

Oil pump of gear type is installed inside crankcase and is fixed to cylinder block by two bolts. Drive gear of pump is fixed on roller, and driven gear rotates freely on axle pressed into pump housing. Oil is supplied to the pump via the oil intake branch pipe, passing through the filter mesh. A reduction valve is built into the housing of the oil intake branch pipe. When the pressure in the lubrication system is higher than the permissible oil, the reducing valve is pressed out, and excess oil is passed from the pressure cavity to the oil intake cavity. The pressure at which the reducing valve operates is provided by a spring of corresponding elasticity .

The oil filter is screwed onto the connector and pressed to the annular collar on the cylinder block. Tightness of connection is provided by rubber gasket installed between filter cover and unit collar. The filter has a back-drain valve preventing oil from flowing out of the system when the engine stops, and a bypass valve that operates when the filter element clogs and bypasses oil in addition to the filter into the main channel. Oil is filtered by paper element.

To lubricate the designed engine, we will use all-season motor oil of the brand M5z/10G1 or M6z/12G1.

Oil level is determined by means of oil measuring probe.

4.7 Cooling system

Air-type engine cooling system. The cooling system consists of the following elements: cooling ribs on the block heads and on the outer part of the cylinder liners; an air supply fan; casing to direct air flow from fan to heads and unit.

Four-bladed fan. Fan blades have variable angle of installation in radius and variable pitch in hub to reduce noise. Fan is mounted on hub pressed on crankshaft pulley.

Cavities designed for linear expansion of metal are provided in block heads for higher cooling efficiency.

Conclusion

This course design should be considered as the first stage in the development of a carburetor engine, that is, it should be considered a sketched design, which includes only preliminary calculations and drawing layout.

As a result of the work done, the indicator parameters of the engine operating cycle were calculated. Based on these results, an indicator diagram of thermal characteristics was built.

Calculations of dynamic indicators gave the dimensions of the piston, in particular its diameter and stroke, the radius of the crank, graphs of component forces were built, as well as a graph of total incoming tangential forces and total incoming torques.

The end result of the calculations was the design of engine parts. The resulting dimensions are represented by a drawing of the format A1, which shows a cross section of the engine.