Vehicle turbine recovery (worn-out surface - axle)

Contents

Introduction

1. Theoretical part

1.1. History of creation and further development

1.2. Turbine Design and Operating Principle

1.3. main characteristics of turbines

1.4. Peculiarities of turbine operation

1.5. Part Analysis for Processability

2. Process Part

2.1. Analysis and selection of the best way to restore the part and the equipment used

2.2. Development of routing process

2.3. Calculation of recovery modes

3. Description of process control tool

4. List of used literature

Introduction

The constant lack of maintenance of spare parts is a serious factor in the decrease in technical readiness of the automobile fleet. The expansion of the production of new spare parts is associated with an increase in material and labor costs. At the same time, about 75% of the parts rejected during the first overhaul of cars are repairable or can be used without restoration at all. Therefore, a viable alternative to expanding the production of spare parts is the reuse of worn-out parts restored during the repair of cars and its units.

It is known from repair practice that most parts rejected by wear lose no more than 1-2% of the original mass. At the same time, the strength of the parts is practically preserved. For example, 95% of the parts of internal combustion engines are rejected with wear not exceeding 0.3 mm, and most of them can be reused after recovery.

From the point of view of material-intensive reproduction of machines, the economic feasibility of repair is due to the possibility of reusing most parts both suitable and extremely worn out after restoration. This makes it possible to carry out repairs in a shorter time with lower costs of metal and other materials compared to the costs of manufacturing new machines.

The high quality of repaired cars and units places increased requirements on the resource of restored parts. It is known that in cars and units after overhaul, the parts work, as a rule, in significantly worse conditions than in new ones, which is associated with a change in the basic dimensions, displacement of the axes in the body parts, a change in the lubrication supply conditions, etc. In this regard, part repair technologies should be based on coating and post-treatment methods that would not only preserve, but also increase the life of repaired parts. For example, when restoring parts by chromium, plasma and detonation spraying, induction and laser surfacing, contact welding of a metal layer, their wear resistance is significantly higher than that of new ones.

The restoration of automotive parts has become one of the most important indicators of the economic activity of large repair, specialized small enterprises and cooperatives. In fact, a new industry has been created - the restoration of worn-out parts. For a number of the most important metal-intensive and expensive parts, the secondary consumption of restored parts is much more than the consumption of new spare parts. For example, restored engine blocks are used 2.5 times more than received new, crankshafts - 1.9 times, gearbox crankshafts - 2.1 times more than new ones. The cost of recovery for most recoverable parts does not exceed 75% of the cost of new parts, and the cost of materials is 15-20 times lower than for their manufacture. The high economic efficiency of enterprises specializing in the restoration of automotive parts ensures their competitiveness in market production.

Abroad also focuses on technology and the organization of part recovery. In highly developed countries - the USA, England, Japan, Germany - repairs are mainly carried out at car manufacturers. Expensive, metal-intensive, mass automotive parts are restored - crankshafts and camshafts, cylinder liners, block blocks and block heads, connecting rods, brake drums, etc. The repair base is the motor and aggregate repair enterprises of the manufacturers of new * machines, independent intermediary companies. For example, in the United States, about 800 firms and companies are engaged in the restoration of parts. These include both specialized firms and companies that produce components for automotive enterprises, in the total volume of production of which 10-40% is accounted for by the production of restored parts. The repair fund is parts from decommissioned cars that are supplied by manufacturers or firms specializing in the processing of unsuitable cars. In the United States, 25 per cent of vehicle spare parts requirements are met as a result of the refurbishment of parts.

Main characteristics of turbines

The main two values are the main size of the turbine and the area/radius ratio (A/R).

It is assumed that the main size of the turbine characterizes its ability to produce the power on the shaft necessary to drive the compressor at the desired air flow rate. Therefore, large turbines, generally speaking, provide higher output than small ones. For the simplicity of the picture, you can estimate the size of the turbine by the diameter of its outlet. Strictly speaking, this is a simplification of turbine theory, but in practice this approach makes it possible to assess the ability of the turbine to provide a particular flow rate.

While the main size of the turbine is a criterion for gas flow through the turbine, the A/R ratio gives a tool for accurate selection from the range of main sizes. To easily understand the idea of ​ ​ the A/R ratio, imagine a turbine casing in the form of a cone wrapped around a shaft in the form of a spiral. Flatten this cone and cut off a small piece some distance from the end. Hole in end of cone is outlet section of casing. The area of ​ ​ this hole is "A" with respect to A/R. The size of the hole is significant because it determines the speed at which the exhaust gases leave the turbine snail and enter its blades. At any given gas flow rate, a reduction in the outlet area is required to increase the flow rate. This speed is essential for turbine speed control. It should be understood that the outlet area affects the side effect of the exhaust back pressure and thus affects the processes in the engine combustion chamber.

"R" with respect to A/R is the distance from the center of the section area in the cone to the axis of rotation of the turbine shaft. All "A" divided into their corresponding "R" will give the same result: R "also has a strong influence on turbine speed control. Imagine that the tips of the turbine blades move at the same speed as the gas when it enters the blades. From here it is easy to understand that the smaller the "R," the higher the turbine speed.

It should be noted that the increase "R" gives an increase in torque on the turbine shaft to drive the compressor impeller, since the same force (exhaust gas flow) is applied on the larger arm of the lever (R). This allows a larger compressor impeller to be driven if the conditions of use so require.

Incorrect selection of the A/R ratio may result in increased supercharging inertia if the ratio is too large. The A/R ratio can be so large that it will not allow the turbocharger to develop speeds sufficient to achieve the desired pressurization pressure. If the ratio, on the contrary, is excessively small, the turbocharger reaction can be so fast that it will seem nervous and difficult to control. The result will also appear in the form of lack of power in the upper third of the engine speed range. This will be similar to an atmospheric engine with a small carburetor, which has an air flap closed.