Hydraulic Brake System

The Hydraulic brake system is a braking system which uses brake fluid usually includes ethylene glycol, to transmit pressure from the controlling unit, which is usually near the driver, to the actual brake mechanism, which is near the wheel of the vehicle.

The most common arrangement of hydraulic brakes for passenger vehicles, motorcycles, scooters, and mopeds, consists of the following

• Brake pedal or Brake lever
• Pushrod, also called an actuating rod
• Reinforced hydraulic lines
• Rotor or a brake disc or a drum attached to a wheel
• Master cylinder assembly includes:
    Piston assembly is made up of one or two pistons, a return spring, a series of gaskets or O-rings.
    Fluid reservoir
• Brake caliper assembly usually includes:
    One or two hollow aluminum or chrome-plated steel pistons called caliper pistons.
    Set of thermally conductive brake pads.

A glycol-ether based brake fluid regularly loads the system or some other fluids are also used to control the transfer of force or power between the brake lever and the wheel.

The automobiles generally use disc brakes on the front wheels and drum brakes on the rear wheels. The disc brakes have good stopping performance and are usually safer and more efficient than drum brakes. The four wheel disc brakes are more popular, swapping drums on all but the most basic vehicles. Many two wheel automobiles design uses a drum brake for the rear wheel.

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What is Lean-Manufacturing ?

Lean Manufacturing is a business initiative to reduce waste in manufactured products. The basic idea is to reduce the cost systematically, throughout the product and production process, by means of a series of engineering reviews.
The crucial insight is that most costs are assigned when a product is designed. Often an engineer will specify familiar, safe materials and processes rather than inexpensive, efficient ones. This reduces project risk, that is, the cost to the engineer, while increasing financial risks, and decreasing profits. Good organizations develop and review checklists to review product designs.
At the system engineering level, requirements are reviewed with marketing and customer representatives to eliminate costly requirements. Shared modules may be developed, such as multipurpose power-supplies or shared mechanical components or fasteners. Requirements are assigned to the cheapest discipline. For example, adjustments may be moved into software, and measurements away from a mechanical solution to an electronic solution. Another approach is to choose connection or power-transport methods that are cheap or that used standardized components that become available in a competitive market.
In mechanical engineering, the process usually begins with a team review of the materials and processes. The team will include a cost accountant, manufacturing and design engineers. Quite often, parts can be combined into a single injection-molded plastic or die-cast part reducing both fabrication and assembly costs. Fasteners are eliminated, reduced or commonized. Tolerances (critical dimensions) are eliminated, widened and adapted to production processes to achieve theoretical 100% yields. Adjustments are eliminated

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Main Components of Compressed Air Systems

Compressed air systems consist of following major components: Intake air filters, inter-stage
coolers, after-coolers, air-dryers, moisture drain traps, receivers, piping network, filters,
regulators and lubricators.

Intake Air Filters : Prevent dust from entering a compressor; Dust causes sticking valves,
scoured cylinders, excessive wear etc.
Inter-stage Coolers : Reduce the temperature of the air before it enters the next stage to
reduce the work of compression and increase efficiency. They are normally water-cooled.
After-Coolers: The objective is to remove the moisture in the air by reducing the
temperature in a water-cooled heat exchanger.
Air-dryers: The remaining traces of moisture after after-cooler are removed using air dryers,
as air for instrument and pneumatic equipment has to be relatively free of any moisture. The
moisture is removed by using adsorbents like silica gel /activated carbon, or refrigerant
dryers, or heat of compression dryers.
Moisture Drain Traps: Moisture drain traps are used for removal of moisture in the
compressed air. These traps resemble steam traps. Various types of traps used are manual
drain cocks, timer based / automatic drain valves etc.
Receivers : Air receivers are provided as stora ge and smoothening pulsating air output -
reducing pressure variations from the compressor.

Compressor Plant and its parts

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Flywheel Energy Storage

Flywheel energy storage systems store kinetic energy (i.e. energy produced by motion) by constantly spinning a compact rotor in a low-friction environment. When short-term back-up power is required (i.e. when utility power fluctuates or is lost), the rotor's inertia allows it to continue spinning and the resulting kinetic energy is converted to electricity.

Active Power's CleanSource® Flywheel Technology, as shown below, integrates the function of a motor, flywheel rotor and generator into a single integrated system. The motor, which uses electric current from the utility grid to provide energy to rotate the flywheel, spins constantly to maintain a ready source of kinetic energy. The generator then converts the kinetic energy of the flywheel into electricity. This integration of functionality reduces the cost and increases product efficiency. 

            A flywheel, in essence is a mechanical battery - simply a mass rotating about an axis. Flywheels store energy mechanically in the form of kinetic energy. They take an electrical input to accelerate the rotor up to speed by using the built-in motor, and return the electrical energy by using this same motor as a generator. Flywheels are one of the oldest and most common mechanical devises in existence. They may still prove to serve us as an important component on tomorrow's vehicles and future energy needs. Flywheels are one of the most promising technologies for replacing conventional lead acid batteries as energy storage systems for a variety of applications, including automobiles, economical rural electrification systems, and stand-alone, remote power units commonly used in the telecommunications industry. Recent advances in the mechanical properties of composites has rekindled interest in using the inertia of a spinning wheel to store energy. 

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Vapour Compression Refrigeration Cycle

Vapour compression refrigeration systems are the most commonly used among all refrigeration systems. As the name implies, these systems belong to the general class of vapour cycles, wherein the working fluid (refrigerant) undergoes phase change at least during one process. In a vapour compression refrigeration system, refrigeration is obtained as the refrigerant evaporates at low temperatures. The input to the system is in the form of mechanical energy required to run the compressor. Hence these systems are also called as mechanical refrigeration systems. Vapour compression refrigeration systems are available to suit almost all applications with the refrigeration capacities ranging from few Watts to few megawatts. A wide variety of refrigerants can be used in these systems to suit different applications, capacities etc. The actual vapour compression cycle is based on Evans-Perkins cycle, which is also called as reverse Rankine cycle.

Vapour Compression Refrigeration System

Compression: In this process vapour is drawn in the compressor cylinder during its suction stroke and is isentropically compressed to pressure P2 during its compression stroke. Hence temperature of vapour increases. 

Condensation: The vapours after leaving the compressor enters the condenser where is is condensed to high pressure liquid. cooling water is supplied to remove heat from the vapour.

Expansion: high pressure liquid is now expanded through throttle valve and the liquid at stage 3 is throttled to lower pressure P1 and has a low temperature. After throttling we get vapours at low temperature.

Vapourization: After the throttle valve the wet vapours are passed through the evaporator. The vapour absorbs the heat from the surrounding hence reach the condition 1.

Figure shows the schematic of a standard, saturated, single stage (SSS) vapour compression refrigeration system and the operating cycle on a T s diagram. As shown in the figure the standard single stage, saturated vapour compression refrigeration system consists of the following four processes:

Process 1-2: Isentropic compression of saturated vapour in compressor
Process 2-3: Isobaric heat rejection in condenser
Process 3-4: Isenthalpic expansion of saturated liquid in expansion device
Process 4-1: Isobaric heat extraction in the evaporator

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Mechanical Parts Drawing for practice

Here i am sharing some mechanical parts industrial drawing solely for practice and understanding.

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Marine Engines Or Parts of Internal Combustion Engine

Here i am sharing the simple marine engine; 9 hp; for small ship:

Marine engine and its parts ( please enlarge to view clearly)

Description of important parts:

1. Cylinder head: In an internal combustion engine, the cylinder head (often informally abbreviated to just head) sits above the cylinders on top of the cylinder block. It closes in the top of the cylinder, forming the combustion chamber. This joint is sealed by a head gasket. In most engines, the head also provides space for the passages that feed air and fuel to the cylinder, and that allow the exhaust to escape. The head can also be a place to mount the valves, spark plugs, and fuel injectors.
2. Intake valve & Exhaust valve: The valves through which fresh fuel enters into the combustion chamber is called intake valve and valve through which residual gases leave are called exhaust valve. These valves are controlled by CAM shaft.
3. Valve rocker arm: Generally referred to within the context of the internal combustion engine of automotive, marine, motorcycle and reciprocating aviation engines, the rocker arm is an oscillating lever that conveys radial movement from the cam lobe into linear movement at the poppet valve to open it.
4. Pre-combustion chamber: This chamber is located at the cylinder head and is connected to the engine cylinder by small holes. It occupies 40% of the total cylinder volume. During the compression stroke, air from the main cylinder enters the pre-combustion chamber. At this moment, fuel is injected into the pre-combustion chamber and combustion begins. Pressure increases and the fuel droplets are forced through the small holes into the main cylinder, resulting in a very good mix of the fuel and air. The bulk of the combustion actually takes place in the main cylinder. This type of combustion chamber has multi-fuel capability because the temperature of the pre-chamber vaporizes the fuel before the main combustion event occurs.
5. Intake Silencer: It serves the purpose of silencing the air intake in engine.
6. Mixing Elbow:  Its function is to cool the engine exhaust gases by mixing them with the cooling water discharged from the engine heat ex-changer  It requires no regular maintenance, but neither should it be completely forgotten. Over time, the exhaust mixer elbow can become restricted with accumulated soot from the engine exhaust, resulting in increased exhaust gas back pressure and loss of engine power.
7. Camshaft: A camshaft is a shaft to which a cam is fastened or of which a cam forms an integral part.
8. Tappet: A tappet is a projection which imparts a linear motion to some other component within a mechanism.
9. Pushrod: An overhead (OHV) engine, also informally called pushrod engine or I-head engine, is a type of piston engine that places the camshaft within the cylinder block (usually beside and slightly above the crankshaft in a straight engine or directly above the crankshaft in the V of a V engine), and uses pushrods or rods to actuate rocker arms above the cylinder head to actuate the valves.
10. Piston:  In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod. 
11. Connecting rod: In a reciprocating piston engine, the connecting rod or conrod connects the piston to the crank or crankshaft. Together with the crank, they form a simple mechanism that converts reciprocating motion into rotating motion.
12. Crankshaft: The crankshaft, sometimes abbreviated to crank, is the part of an engine that translates reciprocating linear piston motion into rotation. To convert the reciprocating motion into rotation, the crankshaft has "crank throws" or "crankpins", additional bearing surfaces whose axis is offset from that of the crank, to which the "big ends" of the connecting rods from each cylinder attach.
13. Flywheel: A flywheel is a rotating mechanical device that is used to store rotational energy. Flywheels have a significant moment of inertia and thus resist changes in rotational speed. The amount of energy stored in a flywheel is proportional to the square of its rotational speed. Energy is transferred to a flywheel by applying torque to it, thereby increasing its rotational speed, and hence its stored energy. Conversely, a flywheel releases stored energy by applying torque to a mechanical load, thereby decreasing its rotational speed.

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Let's Prepare for Technical Interview (Part-6)

Mechanical engineering interview questions:

Que: What is bending moment?
Ans: When a moment is applied to bend an element, a bending moment exists in the element.

Que: What are the points in the Stress Strain curve for Steel?
Ans: Proportional limit, elastic limit or yield point, ultimate stress and stress at failure.

Que: Define Reynolds number?
Ans: Reynolds number is the ratio of inertial force and viscous force. It is a dimensionless number. It determines the type of fluid flow.

Que: What is a Newtonian fluid?
Ans: A Newtonian fluid possesses a linear stress strain relationship curve and it passes through the origin. The fluid properties of a Newtonian fluid do not change when any force acts upon it.

Que: How many Joules is 1 BTU?
Ans: 1 BTU is equal to 1055.056 joules.

Que: What is PS?
Ans: PS is Pferdestarke, the German unit for Horsepower.

Que: Explain Otto cycle?
Ans: Otto cycle can be explained by a pressure volume relationship diagram. It shows the functioning cycle of a four stroke engine. The cycle starts with an intake stroke, closing the intake and moving to the compression stroke, starting of combustion, power stroke, heat exchange stroke where heat is rejected and the exhaust stroke. It was designed by Nicolas Otto, a German engineer.

Que: Explain the nomenclature of a 6203-ZZ bearing?
Ans: 6 is the type code, which shows it is a single-row ball bearing, 2 is the series, means light, 03 is the bore, which is 17 mm and ZZ is the suffix meaning double shielded bearing.

Que: What is Gear ratio?
Ans: It is the ratio of the number of revolutions of the pinion gear to one revolution of the idler gear.

Que: What is Annealing?
Ans: It is a process of heating a material above the re-crystallization temperature and cooling after a specific time interval. This increases the hardness and strength if the material.

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Let's Prepare for Technical Interview (Part-5)

Mechanical Engineering Interview Questions:

Que: The purpose of jigs and fixtures are to: a. Increased production rate
b. Increased machining accuracy
c. Facilitate interchangeable manufacturing
d. Enable employ less skilled operators
e. All of the above
Ans: All of the above.

Que: Which one of the following methods produces gear by generating process
a. Hobbing
b. Casting
c. Punching
d. Milling
e. Broaching
Ans: Hobbing

Que: Tool life of the cutting tool is most affected by
a. Cutting speed
b. Tool geometry
c. Cutting feed and depth
d. Micro-structure of material being cut
e. Not using coolant and lubricant
Ans: Cutting speed

Que: Metal in machining operation is removed by
a. Tearing chips

b. Distortion of metal
c. Shearing the metal across a zone
d. Cutting the metal across a zone
e. Pushing the metal with tool
Ans: Shearing the metal across a zone.

Que: A feeler gauge is used to check
a. Radius
b. Screw pitch
c. Surface roughness
d. Unsymmetrical shape
e. Thickness of clearance
Ans: Thickness of clearance.

Que:The property of a material which enable it to resist fracture due to high impact loads is known as
a. Elasticity
b. Endurance
c. Strength
d. Toughness
e. Resilience
Ans: Toughness

Que: Spring index is
a. Ratio of coil diameter to wire diameter
b. Load required to produce unit deflection
c. Its capability of storing energy
d. Indication of quality of spring
e. Nothing
Ans: Ratio of coil diameter to wire diameter.

Que: Nodular iron has
a. High machinability
b. Low melting point

c. High tensile strength
d. Good fluidity
e. All of the above
Ans: All of the above.

Que: Explain the Second Law of Thermodynamics.?
Ans: The entropy of the universe increases over time and moves towards a maximum value.

Que: How do you measure temperature in a Wet Bulb Thermometer?
Ans: Wet bulb temperature is measured in a wet bulb thermometer by covering the bulb with a wick and wetting it with water. It corresponds to the dew point temperature and relative humidity.

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Let's Prepare for technical interview (Part-4)

Mechanical engineering interview questions:

Que:What is the importance of thermodynamics in the field of mechanical engineering ?
Ans:All the mechanical engineering systems are studied with the help of thermodynamics. Hence it is very important for the mechanical engineers.

Que: How many laws of thermodynamics are there?
Ans: There are three laws of the thermodynamics:

First Law: Energy can be neither created nor destroyed. It can only change forms.In any process in an isolated system, the total energy remains the same.

Second Law: When two isolated systems in separate but nearby regions of space, each in thermodynamic equilibrium in itself, but notin equilibrium with each other at first, are at some time allowed to interact, breaking the isolation that separates the two systems, and they exchange matter or energy, they will
eventually reach a mutual thermodynamic equilibrium. The sum of the entropies of the initial, isolated systems is less than or equal to the entropy of the final exchanging systems. In the process of reaching a new thermodynamic equilibrium, entropy has increased, or at least has not decreased.

Third Law: As temperature approaches absolute zero, the entropy of a system approaches a minimum.

Que: State law of conservation of energy ?
Ans: According to the laws of conservation of energy, “energy can neither be created nor be destroyed. It can only be transformed from one form to another.”

Que: Is boiler a closed system ?
Ans: yes, boiler is definitely a closed system.

Que: What is carnot engine?
Ans: It was being designed by Carnot and let me tell you that Carnot engine is an imaginary engine which follows the Carnot cycle and provides 100% efficiency.

Que:which formula forms a link between thermodynamics and electro-magnetism?
Ans: Gibbs Helmholtz formula is the formula which forms the link between the thermodynamics and electromagnetism.
ΔHs/R = [∂ lnp /∂ (1/T)]x

Que:Which is the hardest compound known?
Ans: diamond.

Que:What is hess law?
Ans:According to the Hess law the energy transfer is simply independent of the path being followed. If the reactant and the product of the whole process are the same then same amount of energy will be dissipated or absorbed.

Que: Which engine is more efficient diesel engine or petrol engine?
Ans: Diesel engine

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Let's Prepare for technical interview (part-3)

Mechanical engineering interview questions:
Que: What is the difference between generator and invertor ?
Ans: An inverter is only effective if there is already a source of electrical energy. It cannot generate
its own. It can simply convert electrical energy that is already there. On the other hand, a traditional generator cannot make AC current into DC current.

Que: What is the difference between qualitative and quantitative research ?
Ans: Quantitative research involves gathering data that is absolute, such as numerical data, so that it can be examined in as unbiased a manner as possible.
Qualitative research may yield stories, or pictures, or descriptions of feelings and emotions. The interpretations given by research subjects are given weight in qualitative research, so there is no seeking to limit their bias. At the same time, researchers tend to become more emotionally attached to qualitative research, and so their own bias may also play heavily into the results.

Que: Difference between adsorption and absorption ?
Ans: In absorption, one substance (matter or energy) is taken into another substance. But in adsorption only the surface level interactions are taking place.

Que: Difference between liquid and aqueous ?
Ans:

• Liquid is a state of matter, while aqueous is a special type of liquid formed by dissolving a compound in water.
• All aqueous solutions are liquids, but not all liquids are aqueous solutions.

Que: Difference between gas and vapor ?
Ans:

• Vapour can turn back and forth into liquid and solid states but a gas cannot.
• Gases cannot be see while vapours are visible.
• Vapours settle down on ground while gases do not.

Que: Difference between boiling and melting point ?
Ans:

• The melting point is a defined for solids when it transfers from solid state to liquid state.
• The boiling point is defined for liquids for a state change from liquid to gas.
• Boiling point is highly dependent on the external pressure whereas the melting point is independent of the external pressure.

Que: why sound is faster in warm air ?
Ans: The speed of sound in air cair = 331.3 + (0.66 x T) m/s, where T is the temperature in °C.
         The speed of sound is proportional to gas temperature and inversely proportional to its
molar mass.
 Sound is transferred by collisions of molecules. Therefore sound waves will travel faster on warm air because collisions of molecules of air in warm air is greater.

Que: How Cavitation can be eliminated in a pump ?
Ans: Cavitation means bubbles are forming in the liquid.

• To avoid Cavitation, we have to increase the Pump size to One or Two Inch;
• To increase the pressure of the Suction Head, or
• Decrease the Pump Speed.

Que: Which pump is more efficient centrifugal pump or reciprocating pump?
Ans: Centrifugal pump.

Because flow rate is higher compared to reciprocating pump. Flow is smooth and it requires less space to install. Lower initial cost and lower maintenance cost.

Que: Why centrifugal pump not called positive displacement type of pump ?
Ans: The centrifugal has varying flow depending on pressure or head, whereas the Positive Displacement pump has more or less constant flow regardless of pressure.

         Likewise viscosity is constant for positive displacement pump where centrifugal pump have up and down value because the higher viscosity liquids fill the clearances of the pump causing a higher volumetric efficiency. When there is a viscosity change in supply there is also greater loss in the system. This means change in pump flow affected by the pressure change.

        One more example is, positive displacement pump has more or less constant efficiency, where centrifugal pump has varying efficiency rate.

Que: Why centrifugal pump is called high discharge pump ?
Ans: Centrifugal pump is a kinetic device. The centrifugal pump uses the centrifugal force to push out the fluid. So the liquid entering the pump receives kinetic energy from the rotating impeller. The centrifugal action of the impeller accelerates the liquid to a high velocity, transferring mechanical (rotational) energy to the liquid. So it discharges the liquid in high rate. It is given in the following formulae:

Centrifugal force F= (M*V2)/R.
Where,
M-Mass
V-Velocity
R-Radius

Que: why cavitation will occur in centrifugal pump and not in displacement pump ?
Ans: The formation of cavities (or bubbles) is induced by flow separation, or non-uniform flow velocities, inside a pump casing. In centrifugal pumps the eye of the pump impeller is smaller
than the flow area of pipe. This decrease in flow area of pump results in increase in flow rate. So pressure drop happened between pump suction and the vanes of the impeller. Here air bubbles or cavities are formed because of liquid vapour due to increase in temperature in impeller. This air bubbles are transmitted to pump which forms cavitation.

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Let's prepare for technical interview (part-2)

Mechanical engineering interview questions:
Que: what is the other name of micrometer and vernier caliper?
Ans: micrometer's other name is screw gauge & vernier caliper's other name is slide caliper.

Que: what is flash-point?
Ans: flash-point is the lowest temperature at which the vapor of combustible liquid can be ignited in air.

Que: what is the difference between impulse turbine and reaction turbine?
Ans: » In impulse turbine, jet is used to create impulse on blades which rotates the turbine and in reaction turbine, no jet is used pressure energy is converted into kinetic energy.
» In impulse turbine fluid enter & leaves with same energy, but in reaction turbine fluid enter with pressure energy and leaves with kinetic energy.

Que: What is the difference between BSP thread and BSW thread?
Ans: The British Standard Pipe thread (BSP thread) is a family of standard screw thread types that has been
adopted internationally for interconnecting and sealing pipe ends by mating an external (male) with an internal
(female) thread. British Standard Whit-worth (BSW) is one of a number of imperial unit based screw thread standards which use the same bolt heads and nut hexagonal sizes.

Que: What is refrigerant?
Ans: Any substance that transfers heat from one place to another, creating a cooling effect. water is the refrigerant in absorption machines.

Que: The amount of carbon present in cast Iron?
Ans: Carbon is basically present in the form of cementite in cast iron.Its percentage lies in the range of 2.03-6.67(% by weight of cementite for Cast Iron.If the amount is less than the above range than it is stainless steel.

Que: What loads are considered while designing nuts and bolts ?
Ans: Shear loads and crushing loads.

Que: What is the effect of reheat on rankine cycle?
Ans: Its efficiency increases.

Que: Why are the head gaskets blown ?
Ans: Normally head gasket blows, when the engine overheats and they can also blow from incorrect installation or poor design. Head gaskets expand and contract according to engine temperature, these cycles may happen after a long period of time, causes the gasket to fail. If you’re replacing the gasket, check the engine block, and head for warping. Follow proper cleaning and torque specifications during assembly.

Que: What is the difference between humidifier and vaporizer ?
Ans: The basic difference between humidifiers and vaporizers is that humidifiers disperse cool mist
 into the air, and vaporizers heat the water to disperse hot steam. Humidifiers are normally used in cooler climates, when due to the usage of heater, the air in the house becomes too dry for comfort and also, it becomes very difficult to breathe. Humidifiers release cool moisture droplets into the air.
    Vaporizers also help in moistening the dry air in the house, but vaporizers release hot vapor into the air. There is a heating element in the vaporizers, which help in releasing steam. Vaporizers heat the water and then release vapors.
    The basic difference between them is that one emits cold vapors, while the other one emits hot vapors.

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Let's prepare for technical interview( part-1)

Mechanical engineering interview questions:
Q. What if the gasoline is used in diesel engine? Diesel engine will work?
Ans. No, it will not work, as the compression ratio of petrol engine is 6 to 10 & that of diesel engine is 15 to 22. Thus on such high compression, gasoline gets highly compressed and it may blast.
Q. Which mechanism is used in automobile gearing system?
Ans. Differntial mechanism.
Q. Why different types of sound are produced in different bikes though they all ran on SI engine?
Ans. Engine specifications are different in different manufacturer like bore diameter(cc), ignition timing. Also the exhaust passage take more responsible for sound.
Q. 1HP= how much watt ?
Ans. 746.2 watt.
Q. How to calculate bearing number to diameter of inner and outer?
Ans. Divide shaft diameter size by 5, it will give last two digits of the bearing number and according to type of load we have to choose the type of bearing and that will give prior no. Of the bearing .
Q. Define octane and cetane number?
Ans. Octane number: octane number is defined as the percentage, by volume, of iso-octane in the mixture of iso-octane and h-heptane. It is the measure of rating of SI engine.
Cetane number: cetane number is defines as the percentage, by volume, of n-cetane in the mixture of n-cetane and alpha methyl naphthaline. It is measure of rating of CI engine.
Q. Poissons ratio is higher in rubber/steel/wood ?
Ans. When material is compressed in one direction, it usually tends to expand in the other two directions perpendicular to the direction of compression. This phenomenon is called the poissons effect. Poisson's ratio is measure of the poisson effect.
For rubber= 0.5
For steel = 0.288
For wood < 0.2
Thus poisson's ratio is higher in rubber.
Q. The fatigue life of the part can be improved by?
Ans. Improving the surface finish by polishing and providing residual stress by shot peening.
Q. When crude oil is heated which hydro-carbon comes first.?
Ans. Natural gas ( gasoline) i.e. at 20 degree celsius.
Q. Difference between technology and engineering?
Ans. Engineering is application of science. Technology shows various methods of engineering. A bridge can be made using beams to bear the load,by an arc or by hanging in a cable; all shows different technology but comes under civil engineering and science applied is law of force/load distribution.

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Common Rail Direct injection (CRDi Engines)

CRDI: Widely know as CRDi, CRDe, DICOR and Tdi and so on by various manufacturers, it has been marked as the technology for this week. The reason, as we can see all around us the fact that the modern diesel is no longer a smoke breathing rattling workhorse, but is the biggest buzzword in the Indian car market. This technology, coupled with rising fuel prices of course has made a diesel car both economical and enjoyable.
 

First conceived by Marelli in 1987 but it wasn't until Fiat acquired the technology that it got tested on one of their cars in 1992. The process was later sent to Bosch group for implementation in the commercial market. The most important contributor to its effectiveness remains with the common rail. Which basically means same fuel line. That is, when fuel gets injected into say cylinder 1; there is virtually no pressure loss at the rest of the rail. This in turn means that there is always adequate pressure available for the injection. Common rail technology makes use of 2 pumps in order to bring the fuel up to high pressures of up to 1350 bar. During the first stage, an electronic pump draws required amount of fuel from the fuel tank; this low-pressure pump is governed by the engine management system. The speed of the pump is determined by driver inputs and other information obtained from sensors. This has allowed Common rail systems to reduced emissions due to absence of unburnt fuel. The second stage of pumping is done with the help of a mechanical pump that is coupled with the crankshaft and geared in order that it may rotate at half engine speed. The fuel now goes to an accumulating duct (rail), where these pressures maybe maintained. This tank allows for the maintaining of this constant pressure even during the injection. The injection maybe carried out using electromagnetic valves, which govern the exact amount of fuel for injection. Leaks occurring at the pump, leaks for opening the valves etc are returned back to the fuel tank. Which in turn results in zero wastage of fuel.

When common rail technology is integrated with turbo chargers or superchargers the power delivered by a diesel engine may well exceed that attained by a similar sized petrol engine. Today's manufacturers are embracing this technology due to all the advantages it holds. At the rate with which this technology is catching up, Diesel definitely holds the key as far as development in efficiency is .

Principle: 

Solenoid or piezoelectric valves make possible fine electronic control over the fuel injection time and quantity, and the higher pressure that the common rail technology makes available provides better fuel atomisation. In order to lower engine noise the engine's electronic control unit can inject a small amount of diesel just before the main injection event ("pilot" injection), thus reducing its explosiveness and vibration, as well as optimising injection timing and quantity for variations in fuel quality, cold starting, and so on. Some advanced common rail fuel systems perform as many as five injections per stroke.

Common rail engines require no heating up time and produce lower engine noise and emissions than older systems.

Diesel engines have historically used various forms of fuel injection. Two common types include the unit injection system and the distributor/inline pump systems. While these older systems provided accurate fuel quantity and injection timing control they were limited by several factors:

• They were cam driven and injection pressure was proportional to engine speed. This typically meant that the highest injection pressure could only be achieved at the highest engine speed and the maximum achievable injection pressure decreased as engine speed decreased. This relationship is true with all pumps, even those used on common rail systems; with the unit or distributor systems, however, the injection pressure is tied to the instantaneous pressure of a single pumping event with no accumulator and thus the relationship is more prominent and troublesome.
• They were limited on the number of and timing of injection events that could be commanded during a single combustion event. While multiple injection events is possible with these older systems, it is much more difficult and costly to achieve.
• For the typical distributor/inline system the start of injection occurred at a pre-determined pressure (often referred to as: pop pressure) and ended at a pre-determined pressure. This characteristic results from "dummy" injectors in the cylinder head which opened and closed at pressures determined by the spring preload applied to the plunger in the injector. Once the pressure in the injector reached a pre-determined level, the plunger would lift and injection would start.

In common rail systems a high pressure pump stores a reservoir of fuel at high pressure — up to and above 2,000 bars (29,000 psi). The term "common rail" refers to the fact that all of the fuel injectors are supplied by a common fuel rail which is nothing more than a pressure accumulator where the fuel is stored at high pressure. This accumulator supplies multiple fuel injectors with high pressure fuel. This simplifies the purpose of the high pressure pump in that it only has to maintain a commanded pressure at a target (either mechanically or electronically controlled). The fuel injectors are typically ECU-controlled. When the fuel injectors are electrically activated a hydraulic valve (consisting of a nozzle and plunger) is mechanically or hydraulically opened and fuel is sprayed into the cylinders at the desired pressure. Since the fuel pressure energy is stored remotely and the injectors are electrically actuated the injection pressure at the start and end of injection is very near the pressure in the accumulator (rail), thus producing a square injection rate. If the accumulator, pump, and plumbing are sized properly, the injection pressure and rate will be the same for each of the multiple injection events.

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Cam-less Engines

The internal combustion engine (ICE) finds its place in the market with latest design modifications in various components to improve efficiency, economy and overall performance. However, one component has remained unchanged in the internal combustion engine development i.e., the camshaft, has been the primary means of controlling the valve actuation and timing, and therefore, influencing the overall performance of the vehicle. Cam-less technology is capturing the future of internal combustion engines. It has been known to man that if valves could be controlled independently in an Internal Combustion Engine then there would be benefits like increased power, reduced emissions and increased fuel economy. In the cam-less technology valve motion is operated by valve actuators of electro-mechanical and electro-hydraulic type.
Introduction: Cams, lifters, push-rods all these things have up until now been associated with the internal combustion engine. But the end is near or these lovely shiny metal objects that comprise the valve train
hardware in your pride and joy. Camless engine technology is soon to be a reality for mass-produced vehicles. In the camless valvetrain, the valve motion is controlled directly by a valve actuator - there's no camshaft or connecting mechanisms. Various studies have shown that a camless valve train can eliminate many otherwise necessary engine design trade-offs.Automotive engines equipped with camless valvetrains of the electrohydraulic and electro-mechanical type have been studied for over twenty years, but production vehicles with such engines are still not available.
Cam-less Valve-train Operation: The types of camless variable valve actuating systems being developed can be classed in two groups: electrohydraulic and electromechanical. When it comes to electromechanical valve trains, there are several designs that are being trialed. Most developers are using the conventional poppet valve system (ie valves that look the same as in today's engines) but an alternative is a ball valve set up. Both use electromagnets in one way or another to open and close the valve. Originally created for the Apollo space program, the electrohydraulic valve actuator works by sending pressurised hydraulic fluid to the engine valve to move it open or closed. These systems are mainly retain poppet valves and are preferred by truck engine manufacturers.

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Water-Jet Cutting

Introduction: In the battle to reduce costs, engineering and manufacturing departments are constantly on the lookout for an edge. The water jet process provides many unique capabilities and advantages that can prove very effective in the cost battle. Learning more about the water jet technology will give us an opportunity to put these cost-cutting capabilities to work. Beyond cost cutting, the water jet process is recognized as the most versatile and fastest growing process in the world. Water jets are used in high production applications across the globe. They compliment other technologies such as milling, laser, EDM, plasma and routers. No poisonous gases or liquids are used in water jet cutting, and water-jets do not create hazardous materials or vapors. No heat effected zones or mechanical stresses are left on a water-jet cut surface. It is truly a versatile, productive, cold cutting process. The water jet has shown that it can do things that other technologies simply cannot. From cutting whisper, thin details in stone, glass and metals; to rapid whole drilling of titanium; for cutting of food, to the killing of pathogens in beverages and dips, the water jet has proven itself unique.
Theory Of Water-jet Cutting: Most water-jet cutting theories explain water-jet cutting as a form of micro erosion as described here. Water-jet cutting works by forcing a large volume of water through a small orifice in the nozzle. The constant volume of water traveling through a reduced cross sectional area causes the particles to rapidly accelerate. This accelerated stream leaving the nozzle impacts the material to be cut. The extreme pressure of the accelerated water particles contacts a small area of the work piece. In this small area the work piece develops small cracks due to stream impact. The water-jet washes away the material that "erodes" from the surface of the work piece. The crack caused by the water-jet impact is now exposed to the water-jet  The extreme pressure and impact of particles in the following stream cause the small crack to propagate until the material is cut through.

Water-jet Cutting Process: Pure water-jet is the original water cutting method.  Water-jet cutting uses only a pressurized stream of water to cut through material. This type of cutting is limited to material with naturally occurring small cracks or softer materials like disposable diapers, tissue paper, and automotive interiors. In the cases of tissue paper and disposable diapers the water-jet process creates less moisture on the material than touching or breathing on it. The figure shows the water-jet cutting process.

   In this process water is increased in pressure by high-pressure pump to about 40000-60000 PSI and is forced through the orifice on to the target material. This high-pressure water on striking the surface performs the machining operation. The potential energy contained in the water is converted in the process to kinetic energy, i.e., into jet velocity, thus achieving its "cutting" effect.

pure water-jet

The basic water-jet process involves water flowing from a pump, through plumbing, and out a cutting head.

   In water-jet cutting, the material removal process can be described as a supersonic erosion process. It is not pressure, but stream velocity that tears away microscopic pieces or grains of material. Pressure and velocity are two distinct forms of energy. The pump’s water pressure is converted to the other form of energy, water velocity by a tiny jewel. A jewel is affixed to the end of the plumbing tubing. The jewel has a tiny hole in it. The pressurized water passes through this tiny opening changing the pressure to velocity. At approximately 40,000 psi the resulting stream that passes out of the orifice is traveling at Mach 2. And at 60,000 psi the speed is over Mach 3.

Applications Of Water-jet Cutting:
• Sheet metal: Stainless steel, carbon steel, high-alloy nickel steels, aluminum, titanium, copper
• Building: Decorative stone, marble, granite, tiles, plasterboard, glass and mineral wool
• Glass: Laminated glass, safety glass, and bulletproof glass
• Foodstuffs: Baked goods, deep-frozen products and fish
• Paper: Cardboard, corrugated cardboard, printing papers
• Miscellaneous: Plywood, leather, textiles, composites, rubber, plastics, sealing materials and foams .

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Friction Welding

Friction welding (FRW) is a welding process that generates heat through mechanical friction between a moving work-piece and a stationary component, with the addition of a lateral force called "upset" to plastically displace and fuse the materials. Technically, because no melt occurs, friction welding is not actually a welding process in the traditional sense, but a forging technique. However, due to the similarities between these techniques and traditional welding, the term has become common. Friction welding is used with metals and thermoplastics in a wide variety of aviation and automotive applications.

Benefits and uses:

• Friction welding techniques are generally melt-free, which avoids grain growth in engineered materials, such as high-strength heat-treated steels.
• Another advantage is that the motion tends to "clean" the surface between the materials being welded, which means they can be joined with less preparation. During the welding process, depending on the method being used, small pieces of the plastic or metal will be forced out of the working mass (flash). It is believed that the flash carries away debris and dirt.
• Another advantage of friction welding is that it allows dissimilar materials to be joined. This is particularly useful in aerospace, where it is used to join lightweight aluminum stock to high-strength steels. Normally the wide difference in melting points of the two materials would make it impossible to weld using traditional techniques, and would require some sort of mechanical connection. Friction welding provides a "full strength" bond with no additional weight. Other common uses for these sorts of bi-metal joins is in the nuclear industry, where copper-steel joints are common in the reactor cooling systems; and in the transport of cryogenic fluids, where friction welding has been used to join aluminum alloys to stainless steels and high-nickel-alloy materials for cryogenic-fluid piping and containment vessels.

Techniques used for friction welding:

1. Spin Welding: Spin welding systems consist of two chucks for holding the materials to be welded, one of which is fixed and the other rotating. Before welding one of the work pieces is attached to the rotating chuck along with a flywheel of a given weight. The piece is then spun up to a high rate of rotation to store the required energy in the flywheel. Once spinning at the proper speed, the motor is removed and the pieces forced together under pressure.This technique is also known as inertia welding,rotational welding or inertial friction welding.
2. Linear Friction welding: Linear friction welding (LFW) is similar to spin welding except that the moving chuck oscillates laterally instead of spinning. The speeds are much lower in general, which requires the pieces to be kept under pressure at all times. This also requires the parts to have a high shear strength. Linear friction welding requires more complex machinery than spin welding, but has the advantage that parts of any shape can be joined, as opposed to parts with a circular meeting point.
3. Friction Surfacing: Friction surfacing is a process derived from friction welding where a coating material is applied to a substrate. A rod composed of the coating material (called a mechtrode) is rotated under pressure, generating a plasticized layer in the rod at the interface with the substrate.

Video Presentation of Inertia Friction Welding:

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Bernoulli Principle (Best Understanding)

Here i am sharing the video of Bernoulli Principle for better understanding.

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Anti-lock Braking System (ABS)

• What is an ABS ?

Anti-lock braking systems (ABS's) are electronic systems that monitor and control wheel slip during vehicle braking. ABS scan improve vehicle control during braking, and reduce stopping distances on slippery (split or low coefficient of friction) road surfaces by limiting wheel slip and minimizing lockup. Rolling wheels have much more traction than locked wheels. Reducing wheel slip improves vehicle stability and control during braking, since stability increases as wheel slip decreases.
 ABS's can be applied to nearly all types of vehicles and can be successfully integrated into hydraulic and air brake systems (including air over hydraulic). This document applies to the ABS's used with air brake systems on commercial vehicles.
 The equipment requirements of FMVSS 121 specify that ABS's on truck-tractors and full trailers must control the brake pressures to at least one front axle and one rear axle. The ABS's on semi-trailers and dollies must control at least one axle of the vehicle. Additionally, the ABS's on tractors must control one of the rear axles with two modulator valves so that the brake pressure on one end of the axle is independent of the brake pressure on the other end. The performance requirements of FMVSS 121 can require an ABS on additional axles.

• How do ABS's works ?

An ABS consists of several key components: electronic control unit (ECU), wheel speed sensors, modulator valves, and exciter rings. Here’s how these components work together:

•  Wheel speed sensors constantly monitor and send electrical pulses to the ECU at a rate proportional to the wheel speed. 
•  When the pulse rates indicate impending wheel lockup, the ECU signals the modulator valve(s) to reduce and/or hold the brake application pressure to the wheel(s) in question.
•  The ECU then adjusts pressure, seeking one which gives maximum braking without risking wheel lockup.
•  When the ECU acts to modulate the brake pressure, it will also (on most vehicles) turn off the retarder (if so equipped) until the risk of lockup is over.
•  The ECU continually checks itself for proper operation. If it detects malfunction/failure in the electrical/electronic system, it will shut down that partof the ABS affected by the problem—or the entire ABS—depending upon the system and the problem. 
•  When this happens, the ABS malfunction lamp lights. 
•  An ABS adjusts brake pressure much faster and more accurately than can drivers. It’s faster because:

  Electronic controls are very fast and ABS modulator valves are physically closer to the brakes than is the driver’s foot brake valve. It is more effective, too, because an ABS can tailor the brake pressure to each wheel or set of wheels to provide maximum braking/stability. Some vehicles also use a traction control system in conjunction with the ABS. Traction control helps the ABS improve vehicle traction by minimizing wheel slip on the drive axle during acceleration. If a wheel on the drive axle starts to slip, the traction control system automatically brakes the wheel slightly, transferring engine torque to the wheels with better traction. If all the drive wheels start to slip, the traction control system may also reduce engine power.Traction control systems are referred to by several different names, depending on the manufacturer. These include: a. Automatic Traction Control (ATC) b. Traction Control (TC) c. Automatic Slip Regulation/Anti-Spin Regulation (ASR)

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Drilling

• Drilling is an operation of producing circular hole in a work-piece by using a rotating cutter called DRILL.
• The machine used for drilling process is called drill machine.
• The drilling operation can also be accomplished in lathe in which drill is held in tailstock and work piece is held by chuck.
• The most common drill tool used is called TWIST DRILL.

DRILL MACHINE: It is the simplest and accurate machine used in production shop. The work piece is held stationary i.e. Clamped in position and the drill rotates to make a hole.

TYPES Of Drilling Machines: 

Sensitive drilling machine: Drill holes from 1.5 mm to 15 mm . Operator senses the cutting action so sensitive drilling machine.

Sensitive drill.

Up-right drilling machine: This type of machine can drill holes up to 50 mm .Table can move vertically and radially.

up-right drill

Radial drilling machine: It the largest and most versatile used form of drilling medium for large and heavy work pieces.

radial drill

Tool Nomenclature:

Precautions for drill machine: 

• Lubrication is important to remove heat and friction.
• Machines should be cleaned after use
• Chips should be removed using brush.
• T-slots, grooves, spindles sleeves, belts, pulley should be cleaned.
• Machines should be lightly oiled to prevent from rusting.

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