STUDY OF MICROTURBINE

Prepared by:

Monark trivedi

B.E.3rd Electrical

Gyuided By,

Mr. Shabbir Bohra

Mr. Naman Bhatt

CONTENT

IntroductionWhat is Micro-turbineNecessity of Micro turbineConstructionPrincipal and workingTypes of Micro turbinePerformanceAdvantages and LimitationsFuture scopeApplicationsConclusion

WHAT IS MICRO TURBINE?

Micro turbines are small gas turbines used to generate electricity. Occpying a space no larger than telephone box. They typically have rang from hand held units producing less than kilowatt, to commercial sized systems that produce tens or hundreds of kilowatts. Micro turbines are a new class of small gas turbines used for distributed generation of electricity. Micro turbines are small version of gas turbines emerged from four different VIZ. small gas turbines, auxiliary power units, automotive and turbochargers.

The small size of micro turbine is a major advantage that allows them to be situated right at a source of electricity demand. This eliminates energy losses that usually occur when transmitting electricity from power station. Such transmission losses are quite significant and can easily amount to 7% of power generated.

Micro turbines operate at lower temp than larger turbines. Their operating temp is 1000C/1832F. Bellow this temp structural change occurs in metal. Material utilized in compressors used in micro turbine included cast iron, aluminum, and stainless steel. Advanced materials such as ceramics and thermal barrier coating are some of the key enabling technologies to further improve micro turbines. Efficiency gain can be achieved with material such as ceramics, which allow a significant increase in engine operating temp. Some generators use samarium cobalt in their design, which is costly but results in higher power density and greater thermal and magnetic stability.

They accept most commercial fuels, such as gasoline, natural gas, propane, diesel, and kerosene as well as renewable fuels such as bio diesel and biogas. Typical micro turbine efficiencies are 25 to 35%. When in a combined heat and power cogeneration system, efficiencies of greater than 80% are commonly achieved.

NECESSITY OF MICRO TURBINE.

In today’s energy economy, most electricity is produced using fossil fuel burning generator. This machine consists of a motor and a dense of the coil of copper wires that surround a shaft containing powerful magnets. To get this power to a home or factory typically requires a local utility to run a heavy copper cable to the residence or business site, But what if site requiring energy is in a remote mountain location, or it’s an offshore oil rig where electricity is scare and hookups doesn’t exists? Here the micro turbines come into the pictures. It is one of the best options to set up a local power generation plant, perhaps using a micro turbine a small, sometimes portable, fossil fuel burning system that can provide enough electricity to power anywhere from 10 to 5000 homes. Also it has an important application as a turbocharger in vehicles when more energy is required from the engine in less amount of fuel.

COMPARISION WITH TURBINE:

Typically micro turbines have power outputs in range of 25 to300KW. In comparison with large power station are entire building and much higher output of around 600MW to 1000MW. One way in which micro turbines can be distinguished from larger turbine is that micro turbine use a single shaft to drive the compressor, turbine and generator. Where is in large power plant, the turbine and generator are on separate shaft and connected by gears that can slow down the high speed rotation of the gas turbines, simultaneously increasing the torque sufficient to run much larger electric generators.

Some micro turbines even include the ability to generate electricity from heat of exhaust gases.

CONSTRUCTION:

Micro turbines are typically single shaft machines with the compressor and turbine mounted on the same shaft as the electrical generator. It therefore consist of only one rotating part, eliminating the need of gear box and associated numerous moving part. Micro turbines are miniature version of the huge machines used to generate power from natural gas, and evolved from aircraft engines and automotive turbochargers

A cut way view of micro turbines is shown in the fig. The single stage turbine and compressor wheels are inertia welded to shaft, which supports the generator alternator rotor and provides for a cold end drive. The inner barring is hydrodynamic barring and outer utilizes a ceramic ball barring. A device called recuperator plays an important role in completing the cycle of micro turbine. Recuperators are difficult to design and manufafacture because they operate under high pressure and temp differentials. Without recuperator the micro turbine electric efficiency is cut to half. Typically, the recuperator is made of metal and takes one of two distinctly different design configuration.

FUNCTION:

The working cycle of micro turbine is shown in the fig. The high velocity exhaust gases coming from the combustor rotate the turbine used in the micro turbine. The preheated air is then used in the combustion process. The combustor is supplied with the fuel in the gaseous form by the gas compressor also fresh and compressed air is supplied to the combustor by the compressor through the recuperator. By preheating the air, less fuel is needed to raise the temp to required level at the turbine inlet. The rest of the exhaust stream is passed through a west heat recovery device that capture more of the heat for use in industrial process, space heating and water heating. The basic working principle of the micro turbine is that the compressor as well as the electric generator is mounted on the same power shaft of the turbine because of this the compressor and generator also rotate with turbine. The generator rotates with the same speed as that of turbine and generates the electricity. The electricity is first given to the power

conditioning devices and then it is supplied to the required areas.

In order to achieve good electrical efficiency despite low peak temp usually heat exchanger (recuperator) is used for preheating combustion air with the help of the hot turbine exhaust gases. Here the recuperator plays an important role of heat exchanger. It absorbs the heat from hot gases coming from the turbine, then it gives this heat to the compressed air coming from the compressor. Thus the air supplied to the combustor is hot and compressed. This helps to increase over all efficiency of the cycle. Micro turbines are very similar in operation to gas turbine. They too work on brayton cycle. If high waste temp are required the micro turbine represent the better solution. Efficiency gains can be achieved with material such as ceramics that allow a significant increase in engine operating temp.

TYPES OF MICRO TURBINES:

There are many types of micro turbines. As a example micro turbine development is based on turbine used for aircraft auxiliary power units, which have been used in commercial airlines for decades. Micro turbines like aero derivative turbines, steam micro turbines, and hydro micro turbines.

1. Aeroderivative turbine : An aeroderitive turbine is an engine derived from a jet engine, which operates at very high compression ratios and which tends to be very compact. Aeroderivative technology enables the manufacture of more efficient gas turbine generators for electric utilities. A steam micro turbine is a device for converting energy from high pressure steam produced in a boiler into mechanical power, which can then be used to generate electricity. Micro turbines

such as a hydro micro turbine are devices for gathering electric power from moving water sources.

2. Steam micro turbine : It is a kind of micro turbine which takes steam as input.3. Hydro micro turbine : It’s a kind of micro turbine which takes water as input.

PERFORMANCE:

MICRO TURBINES EFFICIENCY for 25 to 500 KW

CONFEGURATION EFFICIENCY

Unrecuperated 15%

Recuperated 20-30%

With heat recovery Up to 80%

The performance of the micro turbine is given tabular form as above.

Commercial micro turbines used for power generation range in size from about 25KW to 500KW. They produce both heat and electricity on relatively small scale. The energy of electricity conversion efficiencies are in the range of 20 to 30%. These efficiencies are attained when using recuperator. Cogeneration is an option in many cases as a micro turbine is located at the point of power utilization. The combined thermal electrical efficiency is 85%. Unrecuperated micro turbines have lower efficiencies at around 15%.

FEATURES:

Micro turbines offer many potential advantages for distributed power generation. Selected strengths and weakness of micro turbines of the micro turbine technology are listed bellow.

Advantages:

Smell number of moving parts. Compact size. Light weight. Good efficiency in cogeneration. Low emission. Can utilize waste fuel. Low maintenance cost.

Limitations:

Low fuel to electricity efficiency.

Loss of power output and efficiency with higher ambient temp and elevation.

FUTURE SCOPE:

Extensive field test data collected from units currently in use at commercial and industrial facilities will provide the manufactures with the ability to improve the micro turbine design, lowering the cost and increasing the performance, in order to produce a competitive distributed generation product. Utilities, government agencies and other organization are involved in collaborative research and field testing.

Development is ongoing in a variety of areas:

Heat recovery / cogeneration. Fuel feasibility. Vehicles Hybrid system (e.g. fuel cell/ micro turbines, fly wheel / micro turbines).

APPLICATIONS:

Simplest application for a micro turbine prime movers is of power generation other application exists. Micro turbine prime movers cab used for cooling refregeneration, air compression and pump compression and pump driven application whereby the inherent high speed of power shaft can be used to drive high efficiency and low cost centrifugal compressors.

Micro turbines can be used for stand by power, power quality and reliability, peak saving and cogeneration applications.

Micro turbines are being developed to utilize a variety of fuels, they are being used for resource recovery and landfill gas applications.

It produce between 25Kw to 500Kw of power and are well suited for small commercial building establishments such as restaurants, hotels/motels, small offices, retail stores and many others.

The development of micro turbine technology for the transportation application is also in progress. One of the major applications used is the turbo charger in the small vehicles. Automotive companies are interested in micro turbines to provide a light weight and efficient fossil fuel based energy source for hybrid electrical vehicles, especially buses.

Micro turbines also promise a lot of further development. The competition into the electric market place has driven the development of new electric generation technologies. Most technologies being developed for distributed generation applications are currently too costly, and can be utilized in some applications.

Micro turbines are capable of generating power even with the availability of low grade fuel or low head of water. It is rightly said that the micro turbines will start eating the market share that diesel engine has so far enjoy.

CONCLUSTION:

Being a new technology many countries have not used micro turbines. With increasing rate of power demand micro turbine will soon find their access to the market. Because of their easy handling system and compact size it is very useful in remote area where it is either expensive or not possible to extend the cable line.

Bibliography

1. www.noiseindia/article .com

2. www.google. Com/pictures of micro turbines.

3. Www. Pdf-search engine.com/micro turbines.

4. www.capstone microturbine.com