Notes, summaries, assignments, exams, and problems for Technology

Compressor Group Components

To use the air in a pneumatic circuit, it is necessary to increase the pressure, and this is achieved by the compressor group:

1. The compressor: This is the basic element, and its function is to increase the pressure of the air sucked from the atmosphere. The simplest is the single-phase piston compressor, and the pressure is usually between 6 and 7 bar.
2. The auxiliary engine: This communicates rotary motion to the compressor shaft. It can be a combustion engine or an electric motor.
3. The cooler: This reduces the temperature to 25ºC and eliminates up to 80% of the water it contains.
4. The tank: This stores the compressed air for use when needed.
5. The maintenance unit: This is responsible for achieving good air quality, and for

Gas Turbine Engine Fundamentals

Gas turbines are rotary internal combustion engines. The working fluid undergoes transformations: compression, combustion, and expansion. The fluid expansion takes place between the blades of a turbine to produce mechanical energy.

Applications of Gas Turbines

Applications of gas turbines can be classified into:

• Industrial
• Aeronautics

Industrial Turbine Uses

Industrial turbines are used in both fixed and mobile installations. Among the main uses of industrial turbines are:

• Generating electricity via generators
• Driving large compressors and pressure pumps
• Propelling ships

They are also used in combination with other thermo-mechanical systems for exhaust heat recovery.

Aviation Turbine Types

Aviation turbines apply to retrorockets,... Continue reading "Gas Turbine Engine Fundamentals and Applications" »

Helices and Threads: Fundamental Concepts

A helix is a curve of indefinite length that rotates around the axis of a cylinder, advancing a uniform distance for each rotation. If external, it forms a screw; if internal, it forms a nut.

Generation of Threads

Threads are generated by creating a helical groove on a cylindrical or conical surface.

Classification of Threads

By Number of Starts

• Single-Start: Has a single helix.
• Multi-Start: Has two or more helices.

By Position

• External: Found on screws.
• Internal: Found in nuts.

By Hand of Helix

• Right-Hand Thread
• Left-Hand Thread

By Thread Profile

• Triangular Thread

  Features triangular-shaped flanks, commonly used for fasteners like nuts and bolts.

• Square Thread

  Used in applications requiring high power transmission,

Natural, Synthetic, and Artificial Polymers

A polymer is a macromolecule composed of long strings, where a smaller molecular unit, known as a monomer, is repeated. It is a typical type of structure of organic compounds, formed by the union of monomers, which are carbon compounds, hydrogen, and other radicals, with the ability of carbon to establish bonds between their atoms.

• Natural polymers: proteins, nucleic acids, lignin, chitin, and rubber.
• Synthetic polymers: nylon, polystyrene, polyester, PVC.
• Artificial polymers: rayon, nitrocellulose, and vulcanized rubber.

PVC and Wood: Properties and Uses

PVC

PVC is a thermoplastic polymer that comes in two varieties:

• Rigid: used for structural elements of construction such as door frames, windows, and pipes.

General Documentation

• Name: Tassel House
• Author: Victor Horta
• Date: 1892 - 1893
• Style: Art Nouveau
• Location: Brussels
• Material: Stone, iron, glass, ceramic, and wood
• Construction System: Industrial materials

Formal Analysis

We are in a formal analysis of the Tassel House floor plan, which is narrow, elongated, and almost rectangular, consisting of three floors. The distribution of the floors is determined by the staircase that starts in the lobby and the rooms that are placed on either side of a corridor. The support elements are fine iron columns that allow for the bypass of load-bearing walls. These columns are decorated in the capital with great imagination and creativity. As for the supported elements, apart from the roof, of note are the iron beams... Continue reading "Victor Horta's Tassel House: A Deep Dive into Art Nouveau" »

Theoretical Concepts of CNC Machining

Understanding the fundamental principles of CNC operation is essential for precision machining and proper equipment handling.

Machine Zero and Part Zero

• Machine Zero: Set by the manufacturer, this point serves as the absolute origin of the axes.
• Part Zero (Workpiece Zero): Set by the operator at the origin point of the piece. All movements are programmed from this coordinate. It can be placed anywhere within the machine's workspace.

While an axis moves, the machine or part zero remains constant using codes from G55 to G59. The selection of zero will always be aligned with the Z-axis.

Machine Reference Search

In this operation, the axes are moved to a point defined by the manufacturer, known as the Machine Reference

Applications of the Freewheel Mechanism

The freewheel mechanism is utilized in rear-wheel bicycles and automobile starters. It transmits motion from the starter to the engine; once the engine reaches a higher speed than the starter, it uncouples to prevent damage.

Ratchet Mechanisms: Definition and Types

A ratchet is a mechanism designed to allow rotation in one direction while preventing it in the other. They are classified as:

• Reversible: The direction of blocking can be changed.
• Non-reversible: Blocks in only one direction.
• Configuration: Can be external or internal.

Description of the Welding Arc

An electrode is connected to a transformer cable. When the electrode is brought close to the parts to be joined, an arc jumps, melting both the electrode... Continue reading "Mechanical Engineering Principles: Mechanisms, Welding, and Fasteners" »

Introduction

For the determination of these three characteristics, test power is very limited; a common denominator in all is that the power output is zero.

The power supplied by a three-phase alternator is given by the expression: P = √3 · U · I · cos φ

Which may be zero if any of the three factors are zero.

The current is zero in the vacuum test.

The voltage is zero in the short circuit test.

A power factor of zero is the condition required in determining the reactive characteristic.

Basis of Practice

A three-phase alternator typically consists of an inductor (field winding) based on salient poles, powered by direct current and generally located on the rotor, and a distributed three-phase winding generally located in the stator, called the... Continue reading "Three-Phase Alternator Characteristic Tests" »

Flywheel Functionality

A flywheel counteracts irregular movements. When irregularities occur, the flywheel helps achieve a more uniform rotation in the machine's output shaft.

Coefficient of Fluctuation in Rotating Shafts

The coefficient of fluctuation is the angular speed difference between the average angular velocities, expressed as (wf - wo) / wm.

Types of Clutches

• Friction Clutches
• Tooth Clutches
• Single-Disk Clutches
• Hydraulic Clutches

Hydraulic Clutch vs. Friction Clutch

A hydraulic clutch comprises two turbines and transmits motion using the momentum of oil at high speeds. It operates automatically without requiring any manual input. In contrast, a friction clutch requires a series of actions for proper operation.

Types of Springs

• Tension and Compression

Charging System

Mission: A group of elements whose purpose is to supply electric power to the vehicle and recharge the battery when the engine is running.

Constitution:

• Alternator
• Bridge Rectifier
• Regulator
• Brush holder
• Semicarcasas
• Fan
• Pulley

Alternator Principle

The alternator supplies power in the form of a three-phase rectified supply to electrical appliances and to charge the battery.

Brush Set – Slip Rings

Mission: To enable the feeding of the rotor coil.

Constitution:

• Graphite brushes
• Slip rings

Each ring is connected to one end of the coil and is placed on the shaft. The slip rings must be isolated from each other and from the mass (ground). They are housed in a semicarcasa, often forming part of the regulator-brush holder assembly.

Bridge Rectifier