ABSTRACT

In the world of growing pollution and increasing energy crisis, a need for building a greener way of converting the waste energy is very much required. Exhaust sound energy converter is a device which converts the energy which is wasted to the atmosphere to useful work (electricity). In an automobile only 15-20% of the total fuel energy is used to actually run the car. Rest of the 80-85% of the energy is wasted in the form of heat in the exhaust, sound, vibration and heat given to engine walls (cooling system).

Hence we aim at converting the sound and heat energy back into useful energy through advanced technology. The project consists of two parts. In the first part sound energy is harvested from the exhaust manifold and convert heat energy from the radiator and exhaust gases to sound energy. This sound energy which is actually a mechanical energy can be converted into useful energy by using various techniques. second part we are going to make the sound incident on a transducer device which will convert the vibrations into electric current.

General Terms

Experiments, Investigation, Energy conversion.

Keywords

Sound energy , electrical energy, piezoelectric materials.

1. INTRODUCTION

In this 21st century electric power has very deeply indulged in our society. Can you imagine your life without computer mobile lights and other daily used appliances? It is really very hard to imagine our life without these electric appliances and all these appliances required electricity to operate. And as fast as these world population is rising and also due to the drastic of mankind day by day the electric consumption is increasing drastically on the other hand the production of electric power is limited it is not increasing to that extent due to which there is scarcity of electricity not only ,in India or particular region but across the whole world as development is taking place in a very high rate, according to the METI long term vision · proposed in 2005, the final energy will be mainly supplied by electricity towards 2050 for a low carbonated society. Actually today, the demand of electricity is. Continuously growing in this world and set to be doubled by 2030 so it is necessary to increase the supply of electric power for that it is very essential for us to find other alternative methods to produce electric energy. when we think of another method we think of solar energy, wind energy, hydro energy but we forget sound energy. In the world of growing pollution and increasing energy crisis, a need for building a greener way of converting the waste energy is very much required. Exhaust Sound Energy converter is a device which converts the energy which is wasted to the atmosphere to useful work (electricity). In an automobile only 15-20% of the total fuel energy is used to actually run the car. Rest of the 80-85% of the energy is wasted in the form of heat in the exhaust, sound, vibration and heat given to engine walls (cooling system). Hence we aim at converting the sound and heat energy back into useful energy though advanced technology. The project consists of two parts. In the first part sound energy is harvested from the exhaust manifold and convert heat energy from the radiator and exhaust gases to sound energy. This sound energy which is actually a mechanical energy can be converted into useful energy by using various techniques. In second part we are going to make the sound incident on a transducer device which will convert the vibrations into electric current.

2. LITERATURE REVIEW

Karthikeyan.D and Santhosh. P, ISSN 2248-9967 Volume 4, Exhaust energy conversion through transducer, November 2014.

In an Engine, pulses of alternating high and low pressure are created when an exhaust valve opens and a burst of high-pressure gas suddenly enters the exhaust system. The molecules in this gas collide with the lower-pressure molecules in the pipe, causing them to stack up on each other. In this way the sound wave makes its way down the pipe much faster than the actual gases do. A higher wave frequency simply means that the air pressure fluctuates faster. The faster an engine runs, the higher the pitch we hear. Likewise slower fluctuations produce low pitch sound. The wave's amplitude determines how loud the sound is. It is possible to add two or more sound waves together to get less sound. The key thing about sound wave is that the resultant sound you hear is the sum of all the sound waves that are hitting yow ear drum at that time. Suppose you are listening to an orchestra, even though you may hear several distinct sources of musical notes, the number of pressure waves hitting your ear drum adds together, so your ear interprets only one pressure at any given moment. Now, it is possible to produce a sound wave that is exactly the opposite of another wave. This forms the basis of designing of headphones that are capable of canceling out noises. when the first and the second waves are in phase with each other, they add up to a wave of same frequency but twice the amplitude of incident waves. This is known as constructive interference. But, when these two waves are out phase with each other, they add up to zero. This is known as destructive interference. By the principle of destructive interference, when the first wave is at its maximum pressure and the second wave is at its minimum pressure, if both of these waves hit our ear drum at the same time, then we would hear nothing as the two waves add up to zero. This is what actually happens in the exhaust system of a vehicle.

The exhaust system of a vehicle consists of resonator and a muffler, which is used to reduce the sound made by the engine. By eliminating those sound reducing devices, a high efficient dynamic transducer can be placed at the exhaust pipe. This could convert the sound energy into electrical energy, but requires some measures for its efficient working. It is necessary that it must possess impedance which produces higher output voltage and the transducer must be unidirectional, which picks up sound from one direction only. The sound coming from the engine must undergo constructive interference and focused towards the diaphragm of the transducer, so that it is utilized to the maximum. Now, the sound energy hitting the diaphragm puts the wire coil under fluctuation which changes magnetic field enclosed by it, resulting in the generation of current of definite voltage. The sound of an engine without a silencer lies around 130 db which can teed the 12 volt electrical system of a vehicle. Hence, by the principle of constructive interference and with the help of a transducer, the sound energy could be converted into electrical energy to feed the accessories of a vehicle which draws 2% of the total output of the vehicle.

Oliver B. Wright & Sam Hyeon Lee, Physical Review Letters, 110, 244302, Acoustically invisible walls, June 2013.

Solid walls do not normally transmit sound very well, Even if you open a few small holes here or there, the transmission is still poor. We show that, counter intuitively, if you stretch membranes across the holes, sound or the right frequency transmits almost perfectly.

Sound is incident at a slanting angle on the Wall. If there are no membranes, the sound is, forming a novel lens for sub-wavelength-resolution imaging. Almost all reflected and produces a characteristic interference pattern, With membranes installed in the holes the sound transmits without reflection. It works for any angle of incidence. Also there is a discovery of a giant acoustic concentration, by a factor of up to 5700 in Intensity, inside the holes. A tiny force from the sound wave is sufficient to launch a large motion of the membrane, as if the air in the hole were moving with zero mass. This is responsible for this extraordinary transmission'. Materials with tailored structure on tiny length scales are called Meta materials, and show strange properties such as invisibility. Invisibility for multiple angles of incidence has Previously only been demonstrated for electromagnetic meta materials. Our zero-mass acoustic meta material achieves this at audio frequencies. This invisible wall could be used for security glass that allows you to talk across it while protecting you from any mechanical intrusion. It also could be used to concentrate acoustic energy through a tiny hole,forming a novel lens for sub-wavelength-resolution imaging.

Shalabh Rakesh Bhatnagar, ISSN 2250-2459, Volume 2, Issue 10, Converting sound energy to electrical energy, October 2012.

We all know everywhere there is huge scarcity of energy and for running most of OUR appliances and to carry out daily work we need electricity. It's really very difficult to imagine our life without electricity, our life would really stop so there is high need, to produce electricity at faster rate and find some other feasible method to produce electric energy.Sound is a mechanical form of energy which travel in the form of wave, mechanical wave that is an oscillation of pressure this pressure created by the sound could be used to convert it into electric energy or other form of energy. Also according to law of thermodynamics mechanical energy could be converted into electricity.

Piezo material converts mechanical strain into electric energy this property of piezo material could be used to make a device which would be able to sustainably convert the sound energy to electric energy as piezo material convert sound energy to electric energy. Transducer is also used to convert Mechanical energy to electric energy i.e., it can convert sound energy to electric energy the simple e. g. of use of transducer to convert sound to electric and vice versa is in speakers, headset. Also it could be converted into electric energy by other methods which we will see in the paper.

Sound energy could be converted by different methods

1. Method 1- By creating apparatus using diaphragm, magnet and conductor.
2. Method 2- By converting sound energy to heat energy and then heat energy to electrical energy.
3. Method 3- By using transducers such as piezoelectric material which converts mechanical strain to electrical energy.

Matveev K.I., Wekin A Richards, C.D and Shafiei-Tehrany, vol. 224 no. 1 133-141 Miniature thermoacoustic engine, January 2010.

This article reports experimental and modeling results obtained with a small-scale standing-wave thermoacoustic engine. Reticulated vitreous carbon is used as the stack material and atmospheric air as the working fluid. The engine is tested with resonators of variable lengths in the range 57– 124 mm. The engine starts generating sound at temperature differences of 200–300 °C between the hot and cold parts of the system. The acoustic pressure amplitudes up to 2 kPa are measured inside the resonator in the excited regimes. A simplified energy-balance theory adequately predicts a trend in the temperature difference for the sound onset, while underestimating actual values. Model estimations show that the stack-generated acoustic power reaches 100 mW at the stack-based efficiencies of several per cent.

Orest Symko , A sound way to turn heat into electricity, University of Utah, June 2007.

University of' Utah physicists developed small devices that turn heat into sound and then into electricity. The technology holds promise for changing waste heat into electricity, harnessing solar energy and cooling computers and radars Using sound to convert heat into electricity has two key steps. Symko and colleagues developed various new heat engines (technically called "thermo acoustic prime movers").

Then they convert the sound into electricity using existing technology :"piezoelectric" devices that are squeezed in response to pressure, including sound waves, and change that pressure into electrical current.

Here are summaries of the studies by Symko's doctoral students:

Student Bonnie McLaughlin showed it was possible to double the efficiency of converting heat into sound by optimizing the geometry and insulation of the acoustic resonator and by injecting heat directly into the hot heat exchanger.

She built cylindrical devices 1. 5 inches long and a half-inch wide, and worked to improve how much heat was converted to sound rather than escaping. As little as a 90-degree Fahrenheit temperature difference between hot and cold heat exchangers produced sound. Some devices produced sound at 135 decibels-as loud as a jackhammer.

Student Nick Webb showed that by pressurizing the air in a similar-sized resonator, it was able to produce more sound, and thus more electricity.

He also showed that by increasing air pressure, a smaller temperature difference between heat exchangers is needed for heat to begin converting into sound. That makes it practical to use the acoustic devices to cool laptop computers and other electronics that emit relatively small amounts of waste heat, Symko says.

Student Ivan Rodriguez used a different approach in building an acoustic device to convert heat to electricity. Instead of a cylinder, he built a resonator from a quarter-inch-diameter hollow steel tube bent to form a ring about 1.3 inches across. In cylinder-shaped resonators, sound waves bounce against the ends of the cylinder. But when heat is applied to Rodriguez’s ring-shaped resonator, sound waves keep circling through the device with nothing to reflect them. Symko says the ring-shaped device is twice as efficient as cylindrical devices in converting heat into sound and electricity. That is because the pressure and speed of air in the ring-shaped device are always in sync Student Myra Flit croft designed a cylinder-shaped heat engine one-third the size of the other devices. It is less than half as wide as a penny, producing a much higher pitch than the other resonators. When heated, the device generated sound at 120 decibels-the level produced by a siren.

3.Conversion of sound to electricity:

Hypothesis 1-

Using Piezoelectric Materials

Piezoelectric transducers are used for conversion of sounds into electric energy. The word piezoelectricity means electricity resulting from pressure. Piezoelectricity is the charge that accumulates in certain solid materials in response to applied mechanical stress. The piezoelectric effect exists in two domains, the first is direct piezoelectric effect that describes the material's ability to transform mechanical strain into electrical charge, the second form is the inverse effect, which is the ability to convert an applied electrical potential into mechanical strain energy.

The direct piezoelectric effect is responsible for the materials to function as a sensor and the reverse piezoelectric effect is accountable for its ability to function as an actuator. A material is deemed piezoelectric when it has this ability to transform electrical energy into mechanical energy, and vice versa. The piezoelectric materials are transducers and exist naturally as quartz, possess properties for the production of electricity in very small quantity, however, compare to quartz,an artificial piezoelectric materials such as PZT (Lead Zirconate Titanate) presents advantageous characteristics of generating more electricity.

Hypothesis 2-

Using Dynamic Transducer

A dynamic transducer is the one which uses wire coil, permanent magnet and a thin curtain like diaphragm as its components. It consists of a thin diaphragm attached to the wire coil so that the movement in diaphragm produces a longitudinal motion on the wire coil. The wire coil is wounded over a permanent magnet, which produces an uniform magnetic field. The output is drawn out from the ends of wire coil. When a sound of certain loudness is made to incident on the diaphragm of the transducer it transfers the mechanical disturbance to the coil that is connected to it. That wire coil which is wounded over a magnet, undergoes fluctuation, those results in the production of electric current.

The motion of coil affects the magnetic field of the permanent magnet, so it generates voltage across the wire coil. The movement of the coil depends on the amount of fluctuation of diaphragm, which in turn is decided by the frequency and loudness of the incident sound. Coming to the exhaust system of a vehicle, it consists of resonator and a muffler, which is used to reduce the sound made by the engine. By eliminating those sound reducing devices, a high efficient dynamic transducer can be placed at the exhaust pipe. This could convert the sound energy into electrical energy, but requires some measures for its efficient working. It is necessary that it must possess impedance which produces higher output voltage and the transducer must be unidirectional, which picks up sound from one direction only.

The sound coming from the engine must undergo constructive interference and focused towards the diaphragm of the transducer, so that it is utilized to the maximum. Now, the sound energy hitting the diaphragm puts the wire coil under fluctuation which changes magnetic field enclosed by it, resulting in the generation of current of definite voltage. The sound of an engine without a silencer lies around 130db which can tiled the 12 volt electrical system of a vehicle. Hence, by the principle of constructive interference and with the help of a transducer, the sound energy could be converted into electrical energy to feed the accessories of a vehicle which draws 2% of the total output of the vehicle.

4. Problem Definition

In this project our basic aim is to convert sound energy developed by exhaust gases emitted by IC engine into useful electrical energy. This electrical energy can be use to recharge automobile batteries reducing load off the engine.

The Sound energy is produced in an automobile when fuel enters the combustion chamber; the spark plug ignites hence burning the fuel in chamber where flame propagation starts.

5. Proposed Methodology

1. First the exhaust gases and sound energy flows through the exhaust manifold and then through the exhaust pipe.
2. The sound energy is extracted with the help of the technology developed by south Korean Utah scientist, which is of drilling small holes in the pipe and covering the inside part of the pipe with thin heat resistant polymer.
3. Theoretically Almost 90% of the sound energy is extracted from the pipe on the first bend but to be on the safer side we are assuming 60-70% sound extraction, hence we will be extracting sound on two more turns.
4. This sound energy which is extracted is then vulnerable to the outside atmosphere and its damping properties. Hence it needs to be accumulated and focused on the diaphragm.
5. These sound waves when focused on the diaphragm set it into vibration.
6. These vibrations are transferred from the centre point of the diaphragm to the piezoelectric crystal trough a rigid link.
7. The piezoelectric is held rigidly at the ends by the help of four arms which are fixed at the frame of the diaphragm.
8. Hence the piezoelectric crystal with the help of piezoelectric effect converts the strain exerted on the crystal into electric current. This electric current is then stored with the help of a capacitor.

5. CONCLUSION

Sound is a mechanical disturbance produced in the air, which can be converted into electrical energy by the means of dynamic transducer and piezoelectric materials. Hence we have accomplished the task of converting the sound energy to electrical energy by making an efficient device. A 12 volts bulb can easily be lit with the output available. The results we have obtained are extremely optimised and improvements can be done in it. This idea of creating energy from probably the most underrated form of energy which is present everywhere around us. Hence more than the actual result and progress and improvements the idea is more important. We think this device can be the solution to ever rising problem of energy crisis and pollution.