Why is a diesel engine using a turbocharger instead of a supercharger?

The reason is quite simple: superchargers use or consume engine power while operating, and because diesel engines usually don't produce much power, installing superchargers is not popular, especially for diesel engines with a low load range or RPM.

On the other hand, a turbocharger utilizes waste energy from exhaust gases to drive a turbine, which then powers a compressor to increase the intake air pressure. This process is driven by the engine's exhaust gases, resulting in improved fuel efficiency compared to a supercharger, which is typically driven mechanically by the engine via a belt.

Because diesel engines are usually used in applications that require high torque and load-carrying capacity, they require a higher boost at high RPMs, and turbochargers are more suited to this use because they provide a greater boost at higher engine speeds and can handle higher air flow rates, while the supercharger tends to be more effective at lower engine speeds and may struggle to deliver sufficient airflow for heavy loads.

The latter may be due to size; turbochargers are more compact and do not take up space, while superchargers are usually large and take up space, so their use is less preferred in large-engined vehicles such as trucks or other vehicles, so their use is rarely found in diesel engines.

Why is Diesel–Electric engine more effective than direct diesel engine?

Why do converting mechanical power to electric power then convert electric power back to mechanical power is more effective than directly use mechanical power?

They are most certainly not more efficient. Efficiency is not the reason that diesel-electric locomotives or monster mining trucks exist. The reason is that the electric motor can produce enormous torque at startup without needing a container-sized gearbox. The 2nd advantage is that power can be directly applied to all 10 or 12 locomotive wheels without needing any gearing or coupling rods.

Note the lack of a gearbox and the comparatively small diesel engine….

How do I convert a 230v AC to a 110V DC?

Converting 230V AC (Alternating Current) to 110V DC (Direct Current) involves a two-step process: transforming the voltage level and rectifying the current type. This conversion is commonly required for operating equipment that requires 110V DC and is essential in various electrical applications. The first step in the conversion process is to reduce the AC voltage from 230V to 110V.

This is achieved using a step-down transformer, which adjusts the voltage through electromagnetic induction. The transformer's primary coil receives the 230V AC, and its design ensures that the secondary coil outputs the desired 110V AC. Once the voltage is stepped down, the AC needs to be converted into DC. This is done through a process called rectification.

A rectifier, typically a bridge rectifier, is used for this purpose. It consists of diodes that only allow current to flow in one direction, thus converting the alternating current into direct current. However, this DC is not pure and contains ripples. To smooth out the ripples and achieve a stable 110V DC, a filter (usually comprising capacitors or inductors) is employed.

In some cases, a voltage regulator might also be used to ensure a constant voltage output.

[1]

 The combination of these components—step-down transformer, rectifier, and filter—allows for the efficient conversion of 230V AC to 110V DC.

Footnotes

[1] 

Free energy generator for home

Air-over-oil circuit

 Fig.8.22 illustrates a typical air-over-oil circuit to make best use of advantages of both fluid mediums for counterbalancing application.

AIR-OVER-OIL CIRCUIT

1. Circuit

Fig.8.22 illustrates a typical air-over-oil circuit to make best use of advantages of both fluid mediums for counterbalancing application. This circuit uses an air-oil surge tank, a manually operated 3/3 DC valve, a FRL unit, a flow control valve, a pressure relief valve, and a cylinder. In the surge tank, oil is filled at the bottom and the air at the top.

2. Operation

Extension: When the 3/3 DC valve is shifted to its upper envelope flow path configuration, the compressed air flows via FRL unit and the valve to the surge tank. So the surge tank is pressurized by the compressed air. This pushes the oil (out of the bottom of the surge tank) to the blind end of the cylinder through the flow control valve. Thus the cylinder extends to lift a load. Here the flow control valve can be used to regulate the extension speed of the cylinder.

Retraction: When the 3/3 DC valve is shifted to its lower envelope flow path configuration, the air leaves the surge tank and exhausts into the atmosphere via the DC valve. So the oil at the blind end of the cylinder returns back steadily through the flow control valve and thus the cylinder retracts.

The load (Fload) can be stopped at any intermediated position by shifting the 3/3 DC valve to its spring-centered position. This circuit eliminates the use of a costly hydraulic pump and an oil reservoir. Also this circuit uses the oil for the advantage of generating high force and precision control of the cylinder.

Hydrostatic Transmission System

 Hydrostatic transmissions do not make use of the hydrodynamic forces of the fluid flow.

HYDROSTATIC TRANSMISSION SYSTEM

1. What is Hydrostatic Transmission?

• Hydrostatic transmission is special case of energy transmission system where the mechanical energy of the input drive shaft is converted into pressure energy in the nearly incompressible working fluid and then reconverted into mechanical energy at the output shaft.

• Hydrostatic transmissions do not make use of the hydrodynamic forces of the fluid flow. There is no solid coupling of the input and output. The transmission input drive is a central hydraulic pump and final drive unit(s) is/are a hydraulic motor, or hydraulic. Both components can be placed physically far apart on the machine, being connected only by flexible hoses.

• Hydrostatic transmission consists of a drive wherein the hydraulic energy input element is a pump and the output element is a hydraulic motor.

• Usually hydrostatic transmission pumps and motors are designed and matched to optimise energy transmission.

2. Difference between Hydrostatic Transmission and Hydraulic Energy Transmission Systems

The primary difference between hydrostatic transmission system and a hydraulic system equipped with hydraulic pumps and motors is that an hydrostatic transmission is a whole unit in which pump and motor are specifically matched to work together. Also, hydrostatic transmission controls are designed to provide the specific functions to enable the transmission to perform specific tasks.

3. Advantages of Hydrostatic Transmission

Hydrostatic transmission offer many important advantages over other forms of power transmission. Depending on its configuration, anhydrostatic transmission system:

(i) transmits high power in a compact size;

(ii) exhibits low inertia;

(iii) operates efficiently over a wide range of torque-to-speed ratios;

(iv) maintains controlled speed (even in reverse) regardless of load, within design limits;

(v) maintains a preset speed accurately against driving or braking loads;

(vi) can transmit power from a single prime mover to multiple locations, even if position and orientation of the locations changes;

(vii) can remain stalled and undamaged under full load at low power loss;

(viii) does not creep at zero speed;

(ix) provides faster response than mechanical or electromechanical transmissions of comparable rating; and

(x) can provide dynamic braking.

4. Basic Hydrostatic Transmission System Circuits

• The two basic hydrostatic transmission system circuits are open circuit and closed circuit. The terms 'open circuit' and 'closed circuit' describe how the hydraulic lines in the conducting circuit are connected.

• In an open circuit, the flow path of the fluid is not continuous and is interrupted by the reservoir.

• In closed circuit, flow path remains uninterrupted.

5. Open-Circuit Hydrostatic Transmission System

A simple open-circuit hydrostatic transmission system is presented in Fig.8.23. The major elements of the open-circuit are indicated in Fig.8.23.

6. Closed Circuit Hydrostatic Transmission System

• A typical closed circuit hydrostatic transmission system is depicted in Fig.8.24. 

• Elements: A closed circuit hydrostatic transmission system essentially consists of all the elements of open circuit. In addition, the following two elements are included: (i) Feed or charge pump to replace the leakage oil; and (ii) Dual shock valve to protect the system from the damage in case of pressure over ride and over running condition.

• To improve the performance and to fulfill other desired tasks, many other appropriate components such as accumulator, cooling system, special purpose valves, etc are included in the circuit.

Hydromechanical and Elecrohydraulic Servo system

 Mechanical-type servo valves are generally employed in the less complex systems.

HYDROMECHANICAL AND ELECROHYDRAULIC SERVO SYSTEM

MECHANICAL HYDRAULIC SERVO SYSETM

1. Application of Hydromechanical Servo Valve 

(Hydromechanical Servo System)

• Mechanical-type servo valves are generally employed in the less complex systems.

• Applications for hydromechanical servo valves are on: steering devices (such as power steering system of automobiles); test and training devices; copying devices (such as on machine tools); and heavy-duty mobile equipment.

Now we shall discuss on the automotive power-steering application.

2. Automotive Power-Steering Application of Hydromechanical Servo System

1. Construction

The construction and operation of an automotive power-steering application of hydromechanical servo system (closed-loop system) is illustrated in Fig.8.25.

2. Operation

The functioning of this hydromechanical servo system is as follows:

1. The turning of the steering wheel is the input or command signal to the servo system.

2. The steering wheel moves the valve sleeve that ports oil to the steering cylinder (actuator).

3. Now the piston rod moves the wheel through the steering linkage, as shown in Fig.8.4. 4. Since the valve spool is attached to the linkage, the valve spool moves with linkage. 5. When the valve spool has moved far enough, it cuts off oil flow to the cylinder. This stops the motion of this cylinder.

6. Thus the position of the steering wheel determines the motion of the output wheel to the desired position. To cause the further motion of the output wheel, additional motion of the steering wheel is required.

Thus a given input motion (motion of steering wheel) has produced a specific and controlled amount of output motion (motion of output wheel) and also the output motion is fedback to modify the input via the feedback line (here it is the mechanical feedback recentre called 'null'*)

• Null is the relational condition between the spool and valve port where the valve supplies no control flow at zero load pressure drop. The change in null bias resulting from changes in operating conditions or environment is called null shift.

Electrohydraulic Servo System

 Fig.8.26 illustrates a circuit that uses a closed-loop electrohydraulic servo control system.

ELECTROHYDRAULIC SERVO SYSTEM

1. Construction

Fig.8.26 illustrates a circuit that uses a closed-loop electrohydraulic servo control system. This circuit is very much similar to the open loop hydraulic circuit except that a servo valve replaces the flow control and directional valves.

2. Operation

In this servo system, a feedback device which is attached to the hydraulic actuator senses the actuator position or speed and transmits a corresponding electrical signal to the servo valve. This feedback signal is compared with electrical input signal. Suppose the actuator position or speed is not that intended, then the electronic summer will generate an error signal. This error signal is amplified and fed to the torque motor to correct the difference.

Therefore electrohydraulic servo valves can provide very accurate control relative to position, speed, pressure and load by incorporating the appropriate feedback devices.

Accumulators and Intensifiers

 An accumulator is basically a pressure storage reservoir in which a non-compressible hydraulic fluid is retained under pressure from an external source.

Chapter: 9

Accumulators and Intensifiers

"Think big thoughts but relish small pleasures.

- Jackson Brawn. Jr.

"However far moderne science and techniques have fallen short of their inherent possibilities, they have taught mankind at least one lesson: Nothing is impossible."

- Lewis Mumford

"Men who accomplish great things in the industrial world are the ones who have faith in the money producing power of ideas.

- Charles Fillmore.

Learning Objectives

While reading and after studying this chapter, you will be able to:

• Understand and appreciate the functions and applications of accumulators.

• Discuss the purpose, construction, and operation of various types of accumulators.

• Calculate the capacity and sizing of the accumulators for an application.

• Describe the construction and operation of various accumulator circuits.

• Understand and appreciate the functions and applications of pressure intensifier.

• Explain the construction and operation of a pressure booster.

• Describe the construction and operation of various intensifier circuits.

ACCUMULATORS

1. What are Accumulators?

• An accumulator is basically a pressure storage reservoir in which a non-compressible hydraulic fluid is retained under pressure from an external source.

• In other words, hydraulic accumulator is a device used to store the energy of liquid under pressure and make this energy available as a quick secondary source of power to hydraulic machines (such as presses, lifts, and cranes).

• Example: In case of hydraulic crane or lift, the liquid under pressure needs to be supplied only during the upward motion of the load. This energy is supplied from hydraulic accumulator. But when the lift is moving downward, no large external energy is required and during that period the energy from the pump is stored in the accumulator.

• Thus the function of hydraulic accumulator is analogous to that of the flywheel of a reciprocating engine and a capacitor in an electronic circuit.

• Definition: A hydraulic accumulator is a device that stores the potential energy of an incompressible fluid held under pressure by an external source (such as pump) against some dynamic force (such as weight or gravity, mechanical force by springs, or pressurised gas).

2. Suitability and Applications of Accumulators

• Suitability: Accumulators are suitable for the following types of applications:

1. For hydraulic shock suppression.

2. For fluid make-up in a closed hydraulic system.

3. For leakage compensation.

4. For source of emergency power in case of power failure.

5. For holding high pressures for long periods of time without keeping the pump unit in operation.

• Applications: Accumulators in conjunction with hydraulic systems are used on large hydraulic presses, hydraulic lifts, hydraulic cranes, farm machinery, power brakes and landing gear mechanisms on airplanes, diesel engine starters, and other devices and machinery.

3. Types of Accumulators

Accumulators are classified in terms of the manner in which the load is applied. Various types of accumulators used in hydraulic systems are presented in Fig.9.1.

weight-loaded (or dead-weight) accumulators

 The construction and operation of a dead-weight type accumulator is illustrated in Fig.9.2.

WEIGHT-LOADED (OR DEAD-WEIGHT) ACCUMULATORS

1. Construction

The construction and operation of a dead-weight type accumulator is illustrated in Fig.9.2. It consists of a piston rod or plunger loaded with a dead weight and moving within a cylinder to exert pressure on the hydraulic oil. The dead-weight provides the potential energy to compress the fluid. The dead-weight may be concrete block, iron or steel block, or any other heavy material. The piston should have a precision fit with the accumulator tube so as to reduce the leakage past the piston. One side of the accumulator cylinder is connected to the fluid source (pump) and the other side to the work load (machine).

2. Operation

In the beginning, the ram is at the lower-most position. During idle periods of driven machine (say lift or crane) high pressure fluid (oil) supplied by the pump is admitted in the accumulator cylinder through the check valve. Fluid is allowed continuously till the ram. reaches its uppermost position. At this position, the accumulator cylinder is full of fluid and the maximum amount of pressure energy is accumulated.

During the working stroke of the driven machine (i.e., when it requires maximum amount of energy), the accumulated energy is discharged to the driven machine.

3. Advantages

The advantages of the weight-loaded type accumulators are:

1. The weight-loaded accumulators produce constant pressure for the full stroke i.e., until all the fluid is sent out.

2. They can supply large volume of fluid under high pressure.

3. The large volume of fluid makes them possible to supply pressure to several hydraulic circuits.

4. Disadvantages

The weight-loaded type accumulators are not often used in modern hydraulic systems because of the following disadvantages:

1. They are very heavy and expensive.

2. They are not portable and hence cannot be used for mobile applications.

3. They also do not respond quickly to changes in the system demand.

Spring-loaded Accumulators

 The spring-loaded accumulators are similar in construction to that of dead-weight type accumulators.

SPRING-LOADED ACCUMULATORS

1. Construction

The spring-loaded accumulators are similar in construction to that of dead-weight type accumulators. In this type, instead of loading the ram with dead- weight, it is preloaded with compression spring, as shown in Fig.9.3. It consists of a cylinder body, a moveable piston, and a compression spring. The spring provides the compression energy required for this accumulator.

2. Operation

As the spring is compressed by the piston, the hydraulic fluid is forced into the accumulator cylinder. The pressure in the accumulator is dependent on the size and preloading of the spring. The accumulator pressure increases as the spring gets compressed, because incoming fluid flow increases the load required to compress the spring.

When the fluid is discharged out of the accumulator, it causes the spring to expand. As the spring approaches its free length, the accumulator pressure drops to a minimum. Thus the pressure exerted by the spring-loaded type accumulator on the fluid is not constant as in the dead-weight type.

3. Advantages

1. The spring-loaded accumulators are usually smaller and less expensive than the dead-weight type accumulators.

2. They are easy to maintain.

4. Disadvantages

1. The pressure exerted of the fluid is not constant.

2. They are used mostly for low-volume, low-pressure systems.

3. For high-pressure and high-volume, applications, they tend to be bulky and costly.

Gas-loaded Accumulators

 Gas-loaded accumulators, also popularly known as hydro-pneumatic accumulators, are the most commonly used accumulators in almost all the industrial applications.

GAS-LOADED ACCUMULATORS

1. What are Gas-Loaded Accumulators?

• Gas-loaded accumulators, also popularly known as hydro-pneumatic accumulators, are the most commonly used accumulators in almost all the industrial applications.

• They work on the basis of the Boyle's gas law. They Boyle's gas law states that for a constant temperature process, the pressure of the gas varies inversely with its volume. Mathematically,

• For example, when the gas is compressed more (say half the initial volume), then the pressure of the gas is increased (in this case, the pressure is doubled). This compressibility of gas accounts for the storage of potential energy. This potential energy forces the hydraulic fluid out of the accumulator when the gas expands due to reduction in system pressure..

2. Types of Gas-Loaded Accumulators

• The two types of gas-loaded accumulators (Fig.9.1) are :

1. Non-separator type, and

2. Separator type.

(a) Piston type, (b) Diaphragm type, and (c) Bladder type.

• In the non-separator type, the gas which provides the load is in direct contact with the hydraulic fluid, whereas in the separator type, they are separated by a piston, diaphragm, or bladder.