DESIGN METHODOLOGY FOR COMPRESSED AIR ENGINE

Transcription

1 DESIGN METHODOLOGY FOR COMPRESSED AIR ENGINE Patel Vivek B 1, Raj Kumar 2, Badgujar Nikhil A 3, Vekariya Kinjal G 4, Mr. Govind N. Patel 5 1,2,3,4 UG Student, 5 Assistant Professor, Mechanical Department, SCET-Saij, Kalol, Gujarat, India ABSTRACT: Combustion engines, commonly used for mobile propulsion in vehicles, portable machinery, and so on, are generally powered by gasoline, diesel, or other, fossil fuel that produce significant emission due to the combustion of the fuel. Carbon dioxide, carbon monoxide and nitrous oxide are generated from the combustion of fuels. The emissions have a negative effect on the environment. With escalating fuel costs and increasing concerns over the effects of emissions green technology or clean technology has become a favorable alternative within the last few decades. Currently, the most popular green technology alternatives for combustion engines available in the market are solar, electric, and heated compressed air. Conventional vehicular transportation even in crowded urban environments has required toleration of sulfur and carbon-containing chemical environmental pollutants produced by internal combustion engines and ozone emission and high battery cost of electrically operated vehicles. By the apparatuses and process of this invention, chemical pollution is ratuses and process of this invention, chemical pollution is eliminated. Further, the systems herein described utilize what might otherwise be lost energy on braking a moving vehicle and also utilize usual lost exhaust pressure energy. The prior art has not taught or provided pollution-free transportation vehicles that provide conventional passenger seating and comfort at costs competitive with conventional internal combustion enginepowered vehicles nor air engines that cycle exhaust and vehicular energy. I. INTRODUCTION Overview The motor which is operated by air was first applied to the field of transportation in the mid-19th century. A Two centuries before Dennis Papin capage 9me up with the idea of using compressed air. The first successful application of the pneumatic motor in transportation was the Mekarski system which is used in locomotives. Mekarski engines was first used by Tramway de Nantes in December 13, 1879 to power their fleet of locomotives. It is located in Nantes, France. Robert Hardie had introduced a new method of heating which increases the range of the engine which helped to increase in distance in Charles B Hodges, will also be remembered as a true father of compressed air concept because he didn t invent only cars which run by compressed air but also have a considerable commercial success with it. After the. hard work of twelve years of researches and developments a French engineer by profession Guy Negre, has also designed low consumption and low pollution engine for urban motoring that runs on compressed air technology (CAT).In year 2008, India largest car manufacturer company TATA was also announced that it would introduce world s first commercial vehicle that will run on compressed air. II. COMPRESSED AIR ENGINE In previous chapter we collect the literature survey and found some important design methods for engine components, now in this chapter we prepare design for all component of engine using some specifications. It s very beneficial for making cad model and easily prepaid working model. One of the less orthodox method being developed to provide power for cars is that of compresses air normal air is compressed & stored in tanks along the bottom of the car. The gas is then released into a cylinder, where due to its high pressure if pushes a piston therefore driving the car.the process is the same as that employed in a steam engine, with the exception that the gas is already under pressure &does not need to be heated. Current technology allows air powered car to travel at speed of up to 90 km/h,with a range of up to 300km.The car s 300 liter tanks can be refilled in as little as three minute from special pumps,or in the absence of these,an onboard compressor can do the job in four hours, if plugged into the mains one feature of the air powered engine is that at no time does it make use of electricity meaning that a dynamo has to be fitted to power higher etc. in city where pollution is a larger problem a company is planning to put air powered cars offer a cheap, environmentally friendly solution and in this field they have great potential. Due to their limited range &size it is hard to see them providing an alternative to the combustion engine over long distances or for large scale weight transport. Working Principal Today, internal combustion engines in cars, trucks, motorcycles, aircraft, construction machinery and many theirs, most commonly use a four-stroke cycle. The four strokes refer to intake, compression, combustion (power), and exhaust strokes that occur during two crankshaft rotations per working cycle of the gasoline engine and diesel engine. The cycle begins at Top Dead Center (TDC), when the piston is farthest away from the axis of the crankshaft. A Copyright 2017.All rights reserved. 600

2 stroke refers to the full travel of the piston from Top Dead Center (TDC) to Bottom Dead Center (BDC). 1) INTAKE stroke On the intake or induction stroke of the piston, the piston descends from the top of the cylinder to the bottom of the cylinder, reducing the pressure inside the cylinder. A mixture of fuel and air is force by atmospheric (or greater) pressure into the cylinder through the intake port. The intake valve(s) then close. 2) COMPRESSION stroke With both intake and exhaust valves closed, the piston returns to the top of the cylinder compressing the fuel-air mixture. This is known as the compression stroke. 3) POWER stroke While the piston is close to Top Dead Center, the compressed air fuel mixture is ignited, usually by a spark plug (for a gasoline or Otto cycle engine) or by the heat and pressure of compression (for a diesel cycle or compression ignition engine). The resulting massive pressure from the combustion of the compressed fuel-air mixture drives the piston back down toward bottom dead center with tremendous force. This is known as the power stroke, which is the main source of the engine s torque and power. 4) EXHAUST stroke During the exhaust stroke, the piston once again returns to top dead center while the exhaust valve is open. This action evacuates the products of combustion from the cylinder by pushing the spent fuel-air mixture through the exhaust valve(s). In our project we have to modified these four strokes into totally two stoke with the help of inner CAM alteration. In air engine we can design a new CAM which is operate only Inlet stroke and exhaust stroke. Actually in four stroke engine the inlet and exhaust valve opens only one time to complete the total full cycle. In that time the piston moving from top dead center to bottom dead center for two times. A stroke refers to the full travel of the piston from Top Dead Center (TDC) to Bottom Dead Center (BDC).In our air engine project, we have to open inlet and exhaust valve in each and every stroke of the engine so that it will convert the four stroke engine to two stroke engine by modifying the CAM shaft of the engine. Merits of CAE 1) Air is economical, inflammable, abundant, easily transportable, storable, and non-polluting. 2) Mechanical design for engine is simpler & robust. 3) Low maintenance cost, manufacturing cost as well as low operating cost. 4) Manufacturing cost reduces because there is no need of fuel tank, spark plug, silencers, cooling system and Complex fuel injection mechanism. 5) Very less wear& tear of parts, so smooth working is possible. 6) There is no possibility of knocking and detonation which is major problem of conventional engines. 7) Longer life span; compressed air powered vehicle gives higher efficiency than electric vehicles, which is another technology which fulfils the shortage of fuel and environment friendly. 8) Refilling of tank is time consuming than time of batteries to be charged. 9) Problem of recycle or dispose of batteries can be eliminate by accepting this one. Design of Air Engine The values noted down are used for calculating the mechanical efficiency, indicated power brake power; etc. Since this proto type was designed for low speed, the output power; applied load was also kept low. The prime aim being to test the concept of application of air and the suitability of special connecting rod assembly with its related advantages, hence the obtain result may not be the exact measure of its potential, since it wasn't very professionally designed. Indicated power It can be seen that the indicated power is increasing for increase of load. As load is increased, the speed falls down, to maintain it constant injection pressure has to be increased. As the injection pressure has to be increased, the indicated mean effective pressure gets increased; hence the indicated power is increased. Pimep = indicated mean effective pressure, L = Length of stroke (meter), A = area of piston (m2), N = speed in revolution per minute, n = no of power stroke per minute K = no. of cylinder. We have taken some assumption for calculate cylinder diameter than find break power. A 2cylinder single stroke engine develops 20kw at 2000 rpm. The main effective pressure of each cylinders 800 kpa and flow rate of air L/D =1.5. As per assumption make cylinder design than calculate mechanical efficiency as Indicated Power = indicated network cycles/sec. Ip = Pimep L A N K / 60,000 kw Where, Now, Indicated Power = indicated network cycles/sec. Ip = Copyright 2017.All rights reserved. 601

3 Pimep L A N K / 60,000 kw A= 4 D2 and length= 1.5 D 0.3 = ( D π/4 D )/60000 D = M Take 55 mm diameter of cylinder for air engine as specification. Brake Power The product of the moment arm R & the measured force, F is termed the torque of the engine & is usually expressed in Nm. Torque, T is the uniform or fluctuating turning moment, or twist, exerted by tangential force acting at a distance from the axis of rotation. For an engine operating at a given speed and delivering a given power, the torque must be fixed amount, or the product of F and R must be the constant (T=FR). In case, R is decreased, the F will be increased proportionately and vice-versa. Cylinder List of all components mansion as below:- 1 Cylinder 7 Crank Pin 2 Cylinder Head 8 Crank shaft 3 Cylinder Support 9 Housing 4 Piston 10 Wrist Pin 5 Piston Rings 11 Plastic pipe 6 Crank 12 Washer (Pin Spacer) Where, N = speed in revolution per minute, T = Torque. Bp = Bp = 0.15 kw Mechanical Efficiency The mechanical efficiency is increasing with the increase of output power. At lower output it was very low. However the overall mechanical efficiency is low compared to the conventional engine, the reasons being the addition of three extra joints and the rotating pairs which has increased the frictional loss. The slightly oversized links also has contributed significantly in increasing the frictional force and high initial torque required to set the link in the motion. This can however be improved by optimizing the link sizes, and reducing the frictional loss in the rotating pairs. Figure 3.2:- CAD Model of Cylinder. For making the cylinder, various sizes of pipes are readily available in the market. I used 60mm OD*55mm ID aluminum tube or pipe and cut the cylinder to length of 100mm.Use care not to distort the cylinder when cutting off. Now to drill the 3mm diameter hole in the middle of the cylinder. De-burr the cylinder ID around the hole when finished. Cylinder Head Assembly Drawing of Engine Figure 3.1:- Assembly Cad Model of Air Engine. These are cut from the Teflon bar. Cut the OD of 60mm and 5mm thickness with the help of lathe machine. Drill the 6mm diameter hole in the center of each. Copyright 2017.All rights reserved. 602

4 Cylinder Support It is cut from 1mm thick aluminum sheet. Cut the rectangle 60mm*75mm.Then drilling the 12mm diameter, hole first and then bending the aluminum sheet to a 12.5mm radius. Bend over a round bar with the help of a wooden hammer.finish by re-drilling the 12mm diameter hole because it will be distorted slightly in bending. File any uneven surfaces. Both the connecting rods are the same except for the length between 4.8mm and 3.5mm diameter holes. The parts should be cut out and filed to shape after the holes are drilled. The longer rod is bent as shown on the drawing. Crank Piston Drill the 10mm and 14mm diameter holes first in the piece of 10mm flat stock. After the holes are drilled, cut and file to the shape specified. Crank Pin Material for the piston is Teflon bar. This is light and machines well. According to the size of piston as shown in figure. Cut from the 65mm diameter Teflon bar. The surface finish must be good and also keep the tolerance properly. Piston s OD is 55 mm. Use the still rod of 4mm diameter. This must be fit in to the 4.17mm diameter hole in crank. Crank Shaft Connecting Rod Here, the crank shaft is made from the 10mm diameter of Copyright 2017.All rights reserved. 603

5 copper rod which is readily available in the market. Then filed the flats as per the dimensions. Check the fit in the shaft housing and adjust the OD accordingly. The fit such that to prevent excessive air leakage. Washer (Pin Spacer) Shaft Housing These spacers are easily available in market in various sizes. These spacers are to be a free fit on the crankpin. FLYWHEEL Flywheel is cut from the 5mm thick aluminum plat. The diameter of flywheel is 150mm.Plastic or nylon propeller or wooden propeller of 150mmdiameter can be used as a flywheel. Make this from the length of 15mm OD Teflon rod. Drill the inside diameter of 10mm and then use a reamer to bring the diameter up to size. The outside diameter is 17mm and length of 100mm.Then drill the holes of 10mm diameter go through both walls of the tube at some distance apart. Assembly drawing Wrist Pin Use the steel rod. But here I used cotter pins. Plastic Pipe Transfer pipe is cut from the plastic pipe of 5mm OD which is readily available in the market. The engine is timed so that the inlet opens when the piston is 25 degree from axis of TDC. The air inlet remain s open for 65 degree of rotation.air enters the cylinder pushing the piston downwards. This downward reciprocating motion is transferred by connecting rod to the crank and crankshaft where the reciprocating motion of piston is converted in to the rotary motion of shaft. The admitted air is cut off with the piston 90 degree from the axis of TDC. But it is continues to do work as it expands in the cylinder pushing on the piston downward until the piston has passed BDC and is 12 degree from BDC when the exhaust valve opens. The exhaust opens for period of 180 degree. The exhaust valve has opened and instead of trying to re-compress the air in the cylinder, it is pushed out through the transfer tube for the next 180 degree of rotation until the piston has passed TDC by 12 degree. Then the period of 13 degree during which the piston is trying to suck the air and the cycle repeats. We have Copyright 2017.All rights reserved. 604

6 considered one cylinder only. If in the case of two opposite cylinder engine, the other cylinder will be identical but occur 180 degree out of phase, giving a very balanced power stroke. Show model of air engine assembly drawing. III. RESULTS AND DISCUSSION In the previous chapter3 a brief CAD modeling has been done so we can easy to understand the fabrication of engine. In this chapter discus about working model result. The power outputs from the modified air engine were measured at air pressures ranging from 5 to 9 bar, and the pressure and temperature data were measured at various locations including the inlet, exit, and cylinder. This study also presents a pressure and temperature evaluation inside the cylinder at various crank angles to address the issues of air intake and exhaust and low temperature. the minimum pressure in the cylinder during exhaust pressure also increases as the supplying air pressure increases. A higher cylinder pressure will easily encounter choke flow during exhaust process and restricts the discharging flow rate, leading to a higher residual pressure in the engine. Torque and Pressure Measurements on the Compressed Air Engine in One Cycle Figure 4.1 shows cylinder pressure, inlet pressure, outlet pressure and torque variation acquired at different crank angles at 7 bar supply pressure and 800 rpm. These data were phase-averaged at the same crank angle after 200 cycles. Power Measurements of the Compressed Air Engine The torque and power output from the compressed air engine were evaluated (averaged after 200 cycles) at the test bench at various supplied air pressures, as shown in Figures 4.2 and 4.3. The maximum supplied air pressure during the experiments was limited to 9 bar, which is the highest pressure that small/medium size air compressors can provide. The highest torque 9.99 N m was measured at 9 bar and 465 rpm, and the highest power output of 0.96 kw was obtained at 9 bar and 1320 rpm. The flow rates of the compressed air engine (supplying pressure: 9 bar) vary from 500 L/min to 1050 L/min as the rotation speed changes from 500 rpm to 2000 rpm. The highest torque and power output were obtained at the highest supplied air pressure, indicating that the highest air pressure provides the highest force applied on the piston. Figure 6 shows the P-V diagrams acquired at 1200 rpm at various supplying pressures. The area within the P-V diagram indicates the work output from the piston movement in the engine cycles. Both the enclosed areas in the P-V diagrams and the cylinder pressure during the intake process increase while the supplying air pressures increase. However, Figure 4.5 Shows the P-V diagrams acquired at 7 bar supply pressure and various rotation speeds. The maximum cylinder pressures decreases at higher rotation speeds during the intake processes because the compressed air does not have enough time to fill the cylinder. The cylinder pressure during the exhaust process also increases at higher rotation speeds, and takes more time to decay. This is because the compressed air has less time to discharge from the cylinder. The rotation speed has greater effect on the residual pressure inside the cylinder than the supplied air pressure. Copyright 2017.All rights reserved. 605

7 practical applications in vehicles. The residual air pressure disposed during the exhaust process could be reused if additional cylinders are attached (i.e., adopting a split-cycle design). The exhaust air with a pressure of approximately 2.25 bar can be expanded with additional cylinders, producing extra work. The concept of a split-cycle design can improve the energy usage of compressed air, thereby extending the duration of compressed air engines used in vehicle applications. IV. CONCLUSIONS This study presents the power output examination and pressure/temperature measurements of a pistontype compressed air engine to be installed on vehicles as a main or auxiliary power system. Results show that the compressed air engine, which was modified from a commercially available IC engine, can be operated at an air pressure from 5 to 9 bar and provide 0.96 kw power output and 9.9 N m torque. Although the power output is not as much as that of conventional IC engines using gasoline fuel, the torque generated from the compressed air engine is greater than that obtained from an IC engine. The air consumption (flow rate) of current air engine is low, at approximately 1050 L/min, which limits its power performance. The temperature inside the engine was monitored during the operation, and low temperatures were recorded. The cylinder temperature will continue to decrease if using a higher supply pressure than the pressure applied in current study, causing problems of lubrication and sealing between the piston and cylinder. The efficiency of the compressed air operation is approximately 13% at 5 bar supplying air pressure while the rotation speeds is below 1500 rpm. An increase of exhaust air pressure is expected at higher operating pressures or rotation speeds. Therefore, it is necessary to recycle this energy for REFRENCES [1] Swadhin Patnaik, Compressed Air Engine IJRMET Vol. 5, Issue 2, May - Oct 2015, ISSN: [2] Jadupati Bhakat, Mukul Gupta, Gummadi Gokul Manikanta, Lalit Sai G, MentorMragank Sharma, DESIGNING AND FABRICATION OF COMPRESSED AIR ENGINE International Journal of Research in Engineering and Technology, Volume: 05 Issue: 05,May [3] Kripal Raj Mishra, Gaurav Sugandh, Study about Engine Operated By Compressed Air (C.A.E): A Pneumatic Power Source, IOSR Journal of Mechanical and Civil Engineering, Volume 11, Issue 6 Ver. IV (Nov- Dec. 2014), PP [4] JP Yadav, Bharat Raj Singh, Study and Fabrication of Compressed Air Engine, S-JPSET: ISSN: , Vol. 2, Issue 1. [5] Nitin Parashar, Syed Mazhar Ali, Sumit Chauhan, Ravi Saini, Design and Analysis of Compressed Air Engine, International Journal of Engineering Research & Technology (IJERT), Vol. 3 Issue 6, June Copyright 2017.All rights reserved. 606