Design of an auxiliary ship diesel engine with a capacity of 500 kW, crankshaft speed of 1000 rpm based on the 6CHN 18/22 DRA-600 engine, designed to drive an alternating current electro-generator with a capacity of 500 KVA

Contents

Introduction

1 Feasibility study of thesis project topic

2 Design part

2.1 Technical characteristics and design of the engine

2.2 Thermal calculation of the engine

2.3 Dynamic engine calculation

2.4 Strength calculation of engine main parts

2.5 Calculation of engine systems

3 Special part

3.1 Study of diesel operating process during fuel operation

"DT"

Conclusion

List of sources used

Introduction

Domestic diesel engineering has always been part of the heavy and transport engineering industry, the automotive industry. Diesel engines and units based on them are complex equipment that can be manufactured only with the participation of related industries (electrical, instrument making, metallurgical, turbine building, etc.)

World diesel engineering is developing very intensively and has a number of important areas that are characteristic of domestic diesel engineering:

- increase of cylinder and aggregate capacities due to forcing by average effective pressure and rotation speed;

- increase of fuel and oil economy;

- ensuring reliability, high resources before the first bulkhead and before major repairs;

- equipping diesel engines and units based on them with effective automation systems based on microprocessor equipment, adaptive mechanisms;

- reduction of specific gravity

- purchase of licenses for the production of foreign diesel engines, etc.

All this requires solving issues of organization of high-efficiency working process, reduction of heat stress of cylinder-piston group, reduction of friction, provision of quality cooling, introduction of new technological processes to provide resources and reliable operation of piston rings, valves, bearings and crankshaft, sealing of gas joint, etc., preparation of production for production of licensed engines, creation of specialized enterprises.

This task is also faced by Daldiesel Plant OJSC, which currently produces diesel reduction units with a capacity of 100465 kW with an average effective pressure of up to 17 bar. More forced motors are required to increase aggregate power.

A number of other diesel-building enterprises of the country went along the path of creating forced diesel units: Kolomna Diesel Locomotive Plant (Kolomna), Mamin Plant JSC (Balakovo), etc. The successful economic development of the industry will depend on the result of the activities of each diesel-engineering enterprise, in which case this activity should fit into the tasks that are ahead of domestic diesel-engineering.

2.1.2 Schematic Layout Diagram

Increasing the average effective pressure, maximum cycle pressure and, respectively, thermal and mechanical loads in modern ship medium-speed engines requires a revision of the design of engines, primarily the most important parts of the units.

Since the average effective pressure, the maximum cycle pressure in the designed unit slightly exceeds the same parameters in DR600, it is therefore advisable to evaluate the acceptability of the design of this unit for the designed diesel engine.

2.1.2.1 Engine frame

As before, the main design solution for the framework of engines in world practice can be considered an overhead crankshaft. This makes it possible to achieve high rigidity of the monoblock block - a crankcase in which the bearings of the crankshaft, fixed by means of anchor ties and side bolts (springel ties), are placed. Previously, in world practice, the divided design of the foundation frame and the cylinder block with the laying of the crankshaft in the bed of the foundation frame was often used.

In new models of medium-speed diesel engines, split frame and unit structures are usually not used, and the presence of such design models in the production programs of leading foreign firms is explained by the modernization of previously designed and manufactured series by firms within the scope of this modernization without a fundamental revision of the structures.

Initially, the 6CHN 18/22 diesel engine (DRA600) was designed according to the scheme of the suspended crankshaft. However, during the production of the first batch of diesel engines, Daldiesel OJSC faced great production difficulties, since the existing technological lines provided for the manufacture of only detachable structures of the framework of separate cylinder blocks and foundation frames. Therefore, Daldiesel OJSC was forced to redesign this diesel engine along the framework similar to other mass-produced diesel engines.

Currently, it is known that one of the leading companies in MaK has retained the divided structure of the backbone during the modernization of the M601 type diesel engine.

Therefore, in the project we will dwell on the structural diagram of the designed engine in the framework similar to the prototype of the Daldiesel plant (see Fig. 2.1). The material of the foundation frame and cylinder block is preserved similar to the prototype - gray cast iron.

2.1.2.2 Piston group

The design of the piston group (piston, piston rings) is determined primarily by the degree of acceleration of the engine by the average effective pressure. Depending on the average effective pressure and speed of the diesel engine, all-aluminum pistons, cast iron and composite (a head made of heat-resistant steel, troncaluminum or cast iron) are used. In the present design, the average effective pressure is 1.787 MPa, the crankshaft rotation speed is 1000 rpm, and in terms of the degree of forcing by the average effective pressure, the designed diesel engine differs slightly from the prototype. In the prototype, an all-cast cast iron piston with an open combustion chamber is used, cooled by circulating oil supplied to the cooling cavity through an opening in the connecting rod and the piston pin. In piston grooves of piston there are two semi-trapezoidal chrome compression piston rings, semi-trapecoidal chrome compression oil distribution ring and oil-collecting box with spring expander.

Given the insignificant difference in the degree of forcing of the designed engine and prototype, we maintain the design diagram of the piston group according to the prototype.

2.1.2.3 Connecting rod group

There is no reason to abandon the prototype connecting rod group in the designed engine.

Rod of connecting rod - steel, I-beam section, has hole for oil supply to head bearing. Upper head has bronze bushing locked with screw, lower head with oblique connector and bimetal inserts has toothed lock. The connecting rod cover is fixed with a pin and fixed with connecting rod bolts.

2.1.2.4 Crankshaft

The prototype uses a crankshaft - a steel one-piece steel 45A (select).

The shaft has six connecting rod and seven main necks, the fourth root neck - installation. Support surfaces of knee cheeks perceive axial forces arising during diesel engine operation. Shaft elbows are arranged in three planes arranged at angle 120.

The diameter of the main and connecting rod necks is 150 mm. To increase wear resistance, surfaces of main and connecting rod necks are hardened with high-frequency current.

The crankshaft has drills for supplying oil from the main necks to the connecting rod. Flywheel is attached to flange of crankshaft rear end.

Given the slight increase in the degree of forcing by the average effective pressure compared to the prototype, there is no reason to abandon the design of the crankshaft according to the prototype.

The prototype is designed as a main drive engine, while the diesel engine is connected to the reverse reduction gear by an elastic rubber-cord clutch, for fastening on the end of the flywheel there are threaded holes for fastening bolts.

2.1.2.5 Gas distribution mechanism

In the prototype, the gas distribution mechanism includes a camshaft and a distribution and mechanism drive. The prototype has a lower camshaft arrangement in the diesel cylinder block. This is a traditional design for diesel engines manufactured by Daldiesel OJSC. To simplify the production of the designed engine under the conditions of Daldiesel OJSC, it is advisable to keep the design of the gas distribution mechanism similar to the prototype in the project.

2.2 Thermal calculation

2.2.1 Justification and selection of initial data

The choice of compression ratio depends on the type of diesel engine, its speed, mixing, pressurization. Recommended values = 1216. We take with = 12.5. This compression ratio corresponds to the compression ratio of the prototype and therefore allows you to maintain the design of the diesel engine, since design changes of the main engine parts compared to the prototype are not practical in the design.

Recommended maximum combustion pressure Pmax = 1216 MPa. Maximum economy is achieved with high Pmax values. The maximum combustion pressure above 16 MPa leads to high mechanical stresses, which requires the use of expensive materials, requires high production technology. The maximum combustion pressure shall provide an optimal degree of pressure increase. We take pmax = 13.5.

Complete combustion of the fuel, in which all its combustible parts are converted into final oxidation products, can be obtained only with an excess air ratio of 1 > 1. The values ​ ​ of 1 for diesels vary within 1 = 1.62.2. A decrease in the excess air ratio contributes to an increase in the average effective pressure, but negatively affects the economic performance of the diesel engine. Higher values of 1 slightly reduce temperature stresses. We accept 1 = 2.2.

The coefficient of active heat generation characterizes the amount of heat that is communicated to the working medium and is used to increase the internal energy of the gas and perform mechanical work. The value of the heat release coefficient at point z z is affected by the insufficiency of combustion, dissociation of combustion products and the return of part of the extracted heat to the cooling medium. Experimental values of the active heat release coefficient are: z = 0.750.85; b=0,860,92. We take z = 0.85; b=0,9.

Initial data for thermal calculation:

Effective power Pe, kW 500

Speed n, min-1 1000

Compression ratio with 12.5

Excess air ratio 1 2.2

Heat utilization factor at point b b 0.9

Heat utilization factor at z z point 0.85

Maximum combustion pressure pmax, MPa 13.5

Residual gas temperature Tr, K 725

Heating of a fresh charge from T walls, K 10

Adiabatic efficiency of compressor k.ad 0.75

Indicator chart completeness factor p 0.97

Lower calorific value of fuel Hu, MJ/kg 42.5

Mechanical efficiency m 0.92

Charging factor 1 1

Cleaning factor 2 0.8

Ambient pressure Pa, MPa 0.1

Ambient temperature Ta, K 288

Fuel composition, kg: С = 0.87; H = 0.126; O = 0.004

Conclusion

In this work, the project of the main ship's diesel engine based on the 6CHN diesel engine 18/22-600 was completed, when working on a fixed-pitch screw. The developed diesel engine is more forced by the average effective pressure compared to the prototype and has higher effective performance than the prototype.

Calculations were made: thermal, dynamic and strength.

A comparison of the designed diesel engine with foreign analogues was made, and it was found that according to environmental indicators, the designed engine lags behind its analogues, but the level of emissions is within the limits of IMO and GOST 512492000 standards.