TURBOPROP ENGINE

For relatively high take-off thrust or for low-speed cruise applications, turboprop engines are employed to accelerate a secondary propellant stream, which is much larger than the primary flow through the engine. The relatively low work input per unit mass of secondary air can be adequately transmitted by a propeller. Though a ducted fan could also be used for this purpose, a propeller is generally lighter compared to ducted fan could also be used for this purpose, a propeller is generally lighter compared to ducted fan engine and with variable pitch, it is capable of a wider range of satisfactory performance.

In general, the turbine section of a turboprop engine is very similar to that of a turbojet engine. The main difference is the design and arrangement of the turbines. In the turbojet engine the turbine is designed to extract only enough power from the high velocity gases to drive the compressor, leaving the exhaust gases with sufficient velocity to produce the thrust required of the engine. The turbine of the turboprop engine extracts enough power from the gases to drive both the compressor and the propeller. Only a small amount of power is left as thrust. Usually a turboprop engine has two or more turbine wheels. Each wheel takes additional power from the jet stream, with the result that the velocity of the jet is decreased substantially.

Figure shows a schematic diagram of a turboprop engine. The air enters the diffuser as in a turbojet and is compressed in a compressor before passing to the combustion chamber. The compressor in the turboprop is essentially an axial flow compressor. The products of combustion expand in a two-stage or multistage turbine. One stage of the turbine drives the compressor and the other drives the propeller. Thus the turbine expansion is used to drive both compressor as well as propeller and less energy is available for expansion in the nozzle. Due to lower speeds of propeller a reduction gear is necessary between turbine and the propeller. About 80 to 90% of the available energy in exhaust is extracted by the turbine while rest, about 10 to 20%, contributes the thrust by increasing the exhaust jet velocity.

Total thrust = jet thrust + propeller thrust

Turboprop engines combine in them the high take-off thrust and good propeller efficiency of the propeller engines at speeds lower than 800 km/h and the small weight, lower frontal area and reduced vibration and noise of the pure turbojet engine.

Its operational range is between that of the propeller engines and turbojets though it can operate in any speed up to 800 km/h.

The power developed by the turboprop remains almost same at high altitudes and high speeds as that under sea-level and take-off conditions because as speed increases ram effect also increases. The specific fuel consumption increases with increase in speed and altitude. The thrust developed is high at take-off and reduces at increased speed.

Advantages :-

1.      Turboprop engines have a higher thrust at take-off and better fuel economy.

2.      The frontal area is less than air screw so that drag is reduced.

3.      The turboprop can operate economically over a wide range of speeds ranging from low speeds, where pure jet engine is uneconomical, to speeds of about 800 km/h where the propeller engine efficiency is low.

4.      It is easy to maintain and has lower vibrations and noise.

5.      The power output is not limited as in the case of propeller engines (air screw).

6.      The multicast arrangement allows a great flexibility of operation over a wide range of speeds.

Disadvantages :-

1.      The main disadvantage is that at high speeds due to shocks and flow separation, the propeller efficiency decreases rapidly, thereby, putting up a maximum speed limit on the engine.

2.      It requires a reduction gear which increases the cost and also consumes certain energy developed by the turbine in addition to requiring more space.

ADAPTIVE HEADLIGHT SYSTEM

Suppose you are driving home from a weekend vacation. It's late at night, and the winding two-lane road has no streetlights. You approach a curve at 40 mph -- slow enough to make the turn, but too fast to stop suddenly if you need to. 
In this case what would you do ?

One option is to slow down your vehicle and look what is in front as headlights are focusing in straight line.

         Second option is to go with adaptive headlight system.

Standard headlights shine straight ahead, no matter what direction the car is moving. When going around curves, they illuminate the side of the road more than the road itself. Similarly, when a vehicle with standard headlights crests a hill, the headlight beams temporarily point upwards towards the sky. This makes it difficult for drivers to see the road ahead and for oncoming motorists to see the driver approaching.Adaptive headlights react to the steering, speed and elevation of the car and automatically adjust to illuminate the road ahead. When the car turns right, the headlights angle to the right. Turn the car left, the headlights angle to the left. This is important not only for the driver of the car with adaptive headlights, but for other drivers on the road as well. The glare of oncoming headlights can cause serious visibility problems. Since adaptive headlights are directed at the road, the incidence of glare is reduced.

A car with adaptive headlights uses electronic sensors to detect the speed of the car, how far the driver has turned the steering wheel, and the yaw of the car. Yaw is the rotation of the car around the vertical axis -- when a car is spinning, for example, its yaw is changing. The sensors direct small electric motors built into the headlight casing to turn the headlights. A typical adaptive headlight can turn the lights up to 15 degrees from center, giving them a 30-degree range of movement.

Adaptive headlights also benefit other motorists on the road. For example, when a vehicle turns around a bend in low-light conditions, standard headlights will temporarily point directly at oncoming traffic. This can lead to discomfort and temporary blindness for oncoming motorists. This problem is avoided with adaptive headlights, since their beams stay on the road and do not point at oncoming traffic. In addition, since headlight beams to not point at other motorists, it is safe for drivers who own a vehicle with adaptive headlights to use bi-xenon lights. Emitting a slightly blue-ish tint, these lights are brighter than standard lights and offer a clearer, more distinct view of the road ahead.

THERMODYNAMIC SYSTEM AND SURROUNDING

 When we are discussing thermodynamics, the particular item or collection of items that we’re interested in (which could be something as small as a cell, or as large as an ecosystem) is called the system, while everything that's not included in the system we’ve defined is called the surroundings.

There are three types of systems in thermodynamics: open, closed, and isolated.

An open system can exchange both energy and matter with its surroundings. The stove top example would be an open system, because heat and water vapor can be lost to the air.

A closed system, on the other hand, can exchange only energy with its surroundings, not matter. If we put a very tightly fitting lid on the pot from the previous example, it would approximate a closed system.

An isolated system is one that cannot exchange either matter or energy with its surroundings. A perfect isolated system is hard to come by, but an insulated drink cooler with a lid is conceptually similar to a true isolated system. The items inside can exchange energy with each other, which is why the drinks get cold and the ice melts a little, but they exchange very little energy (heat) with the outside environment. 

REASON BEHIND HAVING VERTICAL EXHAUST SYSTEM IN TRACTOR

What is the reason behind having a vertical exhaust system in a tractor?

1) Tractor is a off-road vehicle, usually used in every terrain including water dominated areas, where, there are chances of water to get in exhaust pipe and causing harm to the engine and exhaust system itself.

2) Most of tractors don't have protective cab, so to avoid suffocation vertical arrangement is best.

3) Many chemicals are spread on crops or plants by driving tractor on the space between plants. If exhaust system is horizontal and below the driver them harmful and hot emissions can harm the crop.

Special note - Sometimes the end of exhaust pipe is curved, or has a hinged cover flap which the gas flow blows out of the way, to try to prevent foreign objects (including droppings from a bird perching, rain drops, ice on the exhaust pipe when the vehicle is not being used) getting inside the exhaust pipe.

CHECK OUT THE REASON WHY TRACTORS DO NOT HAVE SUSPENSION SYSTEM

Why does a tractor not have a suspension system?

First its required to get know what are things affected by a suspension system.

If a suspension is installed in a vehicle , then the vehicle will not have constant motion body. The body tend to oscillate in the direction of axis of the spring.

This oscillation can change ride height while operating . The condition may be while working or moving.Well tractors are supposed to maintain a constant depth in ploughing/digging. For this it requires the movement of the body to be restricted so that we do not disturb the main tractor functions.

If we have a suspended tractors which bounces too much over undulations in a field then we can't expect to have a constant ploughing depth which is a requirement in agriculture.

Suspensions also affects the off road stability.

As the speed of the tractor is less and the tyres big(which absorbs more shocks),the need of suspension is felt less. 

SHAPER MACHINE

The shaper is a machine tool used primarily for:

1. Producing a flat or plane surface which may be in a horizontal, a vertical or an angular plane.

2. Making slots, grooves and keyways

3. Producing contour of concave/convex or a combination of these

Working Principle: The job is rigidly fixed on the machine table. The single point cutting tool held properly in the tool post is mounted on a reciprocating ram. The reciprocating motion of the ram is obtained by a quick return motion mechanism. As the ram reciprocates, the tool cuts the material during its forward stroke. During return, there is no cutting action and this stroke is called the idle stroke. The forward and return strokes constitute one operating cycle of the shaper.

Construction: The main parts of the Shaper machine is Base, Body (Pillar, Frame, Column), Cross rail, Ram and tool head (Tool Post, Tool Slide, Clamper Box Block).

Base: The base is a heavy cast iron casting which is fixed to the shop floor. It supports the body frame and the entire load of the machine. The base absorbs and withstands vibrations and other forces which are likely to be induced during the shaping operations.

Body (Pillar, Frame, Column): It is mounted on the base and houses the drive mechanism compressing the main drives, the gear box and the quick return mechanism for the ram movement. The top of the body provides guide ways for the ram and its front provides the guide ways for the cross rail.

Cross rail: The cross rail is mounted on the front of the body frame and can be moved up and down. The vertical movement of the cross rail permits jobs of different heights to be accommodated below the tool. Sliding along the cross rail is a saddle which carries the work table.

Ram and tool head: The ram is driven back and forth in its slides by the slotted link mechanism. The back and forth movement of ram is called stroke and it can be adjusted according to the length of the workpiece to be-machined.

BELTS

It is used to transmit power form one shaft to another by means of pulleys which rotate at the same speed or at different speed. The amount of power transmitted depends upon the following factors:

1. Velocity or speed of the belt

2. Type of the belt

3. The tension under which the belt in placed on the pulleys

4. The arc of contact between the belt and the smaller pulley.

5. Types of belt drive used. 

Types of transmission belts:

There are many size and shapes belts used in power transmission but today we are describe the mostly used belts.

According to the Shape:

1. Flat belt:

This belt is mostly used in the factories and workshops, where a moderate amount of power is to be transmitted, from one pulley to another when the two pulleys are not more than  eight meters apart.

2. V- belt:

The V-belt as shown in figure is mostly used in the factories and workshops where a moderate amount of power is to be transmitted form one pulley to another, when the two pulleys are very near to each other.

3. Circular belt or rope:

The circular belt or rope as shown is mostly used in the factories and workshops, where a great amount of power is to be transmitted, from one pulley to another, when the two pulleys are more than eight meters apart.

4. Timing belt or toothed belt:

These belts are used for power or motion transmission with accurate timing. These belts have toothed surface with meshed with the pulley so it is not a ordinary belt works on friction. This belts required special type of pulley so it is most expensive belt. This is used to obtain accurate timing.

 

According to Material used for belt:

The material used for belts and ropes must be strong and flexible and should have high coefficient of friction to provide higher efficiency. So the belts material plays a major role in power transmission. According the belt material is classified as follows.

1. Leather belt:

This are the most important belt used in workshops. It is made by 1.2 meter to 1.5 meters long strips cut from either side of the bhack bone of the top grade steer hides.  The hair side of lather is more smoother and harder than the flesh side but the flesh side is interwoven and parallel to the surface. 

The leather may be either oak-tanned or mineral salt tanned. To increase the thickness of belts, the strips are cemented together. According to this the belt are designate by the numbers of layers, single ply, double ply etc.

2. Cotton or fabric belt:

Canvass or cotton duck are used in the fabric belts. These belts are made by three or more layer stitching together. These belts are woven also into a strip of the desired width and thickness. These belts are impregnated with some filler like linseed oil in order to make belts water proof and to prevent injury to the fibers. The cotton belts are suitable in warm climates, in damp atmospheres and in exposed positions. Since cotton belts require little attention, therefore these belts are used in farm machinery, belt conveyor etc. 

3. Rubber belt:

The rubber belts are made of layers of fabric impregnated with rubber composition and have a thin layer of rubber on the faces. These belts are very flexible but the quickly destroyed if allowed to come into contact with heat, oil and grease. The rubber has elastic quality so these belts are easily made endless. These belts are found suitable for saw mills, paper mills where they are exposed to moisture.

4. Balata belts:

These belts are similar to rubber belts except that balata gum is used in place of rubber. These belts are acid proof and water proof and it is not effected by animal oils or alkalies. This belt has higher strength than rubber belt.