FABRICATION OF AIR COOLING BY EXHAUSTABSTRACT

This project work water absorption refrigeration system using the exhaust of an internal combustion engine as energy source. The exhaust gas energy availability and the impact of the absorption refrigeration system on engine performance, exhaust emissions, and power economy are evaluated. The exhaust gas energy availability suggests the cooling capacity can be highly improved for a dedicated system. Exhaust hydrocarbon emissions were higher when the refrigeration system was installed in the engine exhaust, but carbon monoxide emissions were reduced, while carbon dioxide concentration remained practically unaltered.

INTRODUCTION

Energy efficiency has been a major topic of discussions on natural resources preservation and costs reduction. Based on estimates of energy resources reduction at medium and long terms, it is vital to develop more efficient processes from energy and exergy standpoints. Environment preservation must also be considered through energy optimization studies. An important point to mention absorption refrigeration systems is the continuing substitution of chlorinated fluorocarbons (CFCs) by alternative refrigerants, according to the Montreal Protocol, signed in 1987 by 46 countries and revised in 1990 to protect the ozone layer.Other motivating factors are the continuous optimization of the performance of internal combustion engines and the increasing utilization of air conditioning in vehicles, as it reaches the status of essential need for modern life. Internal combustion engines are potential energy sources for absorption refrigeration systems, as about one third of the energy availability in the combustion process is wasted through the exhaust gas. Thus, use of the exhaust gas in an absorption refrigeration system can increase the overall system efficiency.This work has as an objective the study of the feasibility and potential of using the internal combustion engine exhaust gas as energy source for an absorption refrigeration system. For this purpose was performed an experimental study on a commercial 215-l refrigerator. The impact of the absorption refrigeration system on engine power output and exhaust emissions is analyzed, in order to know how this system influences the operation of an internal combustion engine.

OBJECTIVE

The demand for fossil fuels is on the rise and the threats possessed by the pollutants cannot be neglected. And so is the requirement for energy efficient machines and this topic deals with the usage of wasteful energy from vehicular exhaust emissions for refrigeration or air conditioning purpose.Air conditioning is also becoming a necessity in our society. Considering this, usage of different methods like absorption refrigeration systems, adsorption systems, solar systems, can contribute to the overall efficiency of vehiclesThe topic also deals with an experiment related to a vehicle integrated with absorption refrigeration system. Its results and the scopes are also discussed in the topic.

INTERNAL COMBUSTION (IC) ENGINESAn IC engine is one in which the heat transfer to the working fluid occurs within the engine itself, usually by the combustion of fuel with the oxygen of air.In external combustion engines heat is transferred to the working fluid from the combustion gases via a heat exchanger. E.g. steam engines, Stirling engines.IC engines include spark ignition (SI) engines using petrol as a fuel, and compression ignition (CI) engines (usually referred to as Diesel engines) using fuel oil, DERV, etc as a fuel.In these engines there is a sequence of processes:1. Compression2. Combustion3. Expansion4. Exhaust / Induction Four strokes of the piston - hence the 4-stroke engine, or Two strokes of the piston - hence 2-stroke engines.5.1 PETROL ENGINES:In petrol engines the air-fuel ratio (AFR) is maintained at an approximately constant value of 14-16:1 by the carburetor or fuel injection system. The top temperature (T3) and the torque is determined by the amount of air-fuel mixture admitted by the throttle. Hence petrol engines are described as being quantity governed.In normal running - the flame front advances through the mixture at flame propagation speed after a short delay from spark ignition. Under certain conditions detonation - combustion / shock waves form (often referred to as pinking or knocking). The Octane rating of a fuel - is a measure of its tendency to resist detonation (from a mixture of iso-octane & n-heptanes).In petrol engines air and fuel are pre-mixed and ignited by an electric spark and the combustion process proceeds as a flame front across the combustion chamber. If the design and mixture is correct then there are no problems but if rc > 9 the mixture tends to explode prematurely. Also, fuel will not ignite and burn except between air-fuel ratios of between 10 and 20 to 1.An air-fuel ratio of 14.7 to 1 is the chemically ideal ratio (known as the stoichiometric ratio) and the carburetor or fuel injection system attempts to provide this.5.2 DIESEL ENGINES:In diesel engines varying amounts of fuel, in the form of very fine droplets, are injected into approximately the same amount of air, irrespective of the engines speed, to control the top temperature and the torque. The AFR therefore varies (typically between 20 -100:1), hence Diesel engines are described as being QUALITY governed. Fuel burns (after a slight delay) on injection. Compression ratios (rc, typically 18 - 22:1] are limited more by engine component strength than thermodynamics.Diesel knock can also occur (initial rapid combustion).Fuel ignitability is measured by 'CETANE' rating On the compression stroke air is compressed adiabatically to a temperature such that when liquid fuel is sprayed into the combustion space in droplet form it self-ignites. This is why the compression ratios of diesel engines are typically about twice those of petrol engines. The droplets move around in the combustion space seeking oxygen and burning takes place on the droplet surface at a local AFR of about 15 to 1.To promote finding oxygen turbulence is induced in the combustion space. In a diesel engine only enough fuel is injected, to produce the torque required at any given engine speed. It is not possible to use the stoichiometric AFR because the fuel will never find enough oxygen quickly enough - and unburned fuel in the form of black smoke (carbon particles) will be emitted.At 300 RPM the time for combustion is about 8 milliseconds early diesel engines used constant pressure heat transfer rather than constant volume heat transfer as in the Otto cycle. In practice this can be achieved by a relatively short air blast fuel injection process. The ideal (or 'true') diesel cycle is shown below in which the process 23 is constant pressure heat transfer to the cycle.

CHAPTER-6EXHAUST SYSTEM AND RECUPERATORS6.1 EXHAUST SYSTEM DESIGN:Exhaust system is relatively simply constructional system but complex set to fulfill all functions as mentioned above. A typical exhaust system consists of exhaust manifold, exhaust pipe, after-treatment device, muffler (silencer), tailpipe and clamps. All parts should be designed according to very hot and corrosive exhaust gases, which leave the engine under high pressure giving vibration and noise. The exhaust gases are pollutants and this fact has to be taken during designing process for environment protection, too

Fig: No: 6.1 Exhaust ManifoldThe exhaust manifold collects the burned gases escaped from the engine cylinders and directs them into the exhaust pipe. Manifolds may be made of cast iron or be assembled from steel tubing. Usually, flanges are made on the manifold where it connects to the engine and to the exhaust pipe. The mating surfaces of the flanges are machined to a smooth finish for an airtight seal against the engine and the exhaust pipe to prevent exhaust gases from leaking. Sometimes metal-to-metal contact provides the seal. Nuts made of brass are used to secure the manifold flanges because brass does not rust. Exhaust passages inside the manifold must be fairly smooth and free of any obstructions that would slow the flow of exhaust gases. 6.1.1 Exhaust Pipe The exhaust pipe is the passageway for the exhaust gases to flow from the manifold to the muffler. It is a heavy steel tube, usually flanged at both ends, and attached to the muffler. The diameter of the exhaust pipe is usually determined by the size of the engine. On a small, one-cylinder engine, a pipe no larger than a household water pipe is enough to do the job. Larger engines may require exhaust pipes 80-100 mm in diameter to carry the larger amount of exhaust gases. The length of the exhaust pipe is determined by the design of the vehicle. If the engine is in the front of the vehicle and the muffler is mounted in the rear, the pipe will be long. (Often, long pipes will be made in two sections.) To provide as much road clearance as possible, pipes are formed in odd shapes that fit well up under the vehicles without touching other components. Pipes are supported from the vehicle frame by hangers. The center portion of the hanger can be made of flexible material to absorb vibration.6.2 AFTER-TREATMENT DEVICES: To help reduce the emissions, there have been developed interesting devices called after-treatment ones or catalytic converters, which treats the exhaust before it leaves the engine and removes a lot of the pollution.Muffler (silencer): The purpose of the muffler is to muffle the exhaust noise. A perfect muffler would silence all the noise made by the exhaust gases and would eliminate all backpressure. However, it is not practical to make a muffler so perfect. There are two basic muffler designs: straight-through and baffle. The straight-through type has a pipe extending straight through the muffler and a chamber surrounding it. Holes are drilled all around the pipe, and metal shavings or glass wool is packed in the chamber that surrounds the through pipe. On the baffle-type muffler, the exhaust must travel through holes in several baffles before it escapes through the muffler outlet. Often, a small hole is drilled in the bottom of the muffler to allow condensed water to drain. Mufflers are made of sheet metal and are crimped or welded together at the seams. They cannot be disassembled. Located inside the muffler is a set of tubes. These tubes are designed to create reflected waves that interfere with each other or cancel each other out

Fig: No: 6.2 MufflersTailpipe: The tailpipe carries exhaust gases from the muffler outlet to a point where they can be safely ejected. It is made of steel tubing and may be a little smaller in diameter than the exhaust pipe. A smaller pipe can be used because the muffler has cooled the gases a great deal, causing them to contract. The pipe may be secured to the muffler by either a flange or a slip-together connection. To ensure that the pipe stays in the proper position along the body or frame of the vehicle, hangers are used. Some trucks have their tailpipes run up beside the vehicle cab.6.3 SINGLE OR DUAL EXHAUST SYSTEMS: Vehicles with V-type engines may have single or dual exhaust systems. When the dual system is used, each bank of cylinders has a separate exhaust system with its own manifold exhaust pipe, muffler, and tailpipe. The dual exhaust permits the exhaust gases to travel in a straighter path to the rear of the vehicle. Therefore, the dual exhaust system causes less back pressure than the single and is desired for best engine performance. However, the additional parts make dual exhaust systems more expensive than single exhaust systems. If a single exhaust system is used on a V-type engine, the exhaust gases from the two banks of cylinders must be brought together at some point. On some engines, a crossover pipe made from a steel tube connects the two exhaust manifolds. Exhaust gases from both cylinder banks then leave through one exhaust pipe that is connected to one of the exhaust manifolds. Another method is to bring together the exhaust pipes from the right and left cylinder banks, forming a "Y" connection.6.4 TYPE OF WASTE HEAT RECOVERY RECUPERATORS: Heat exchange between flue gases and the air through metallic/ceramic walls Ducts/tubes carry combustion air for preheating Waste heat stream on other side

Fig: No: 6.3 Waste Heats 6.4.1 Metallic Radiation Recuperators: Simplest recuperator Two metal tubes Less fuel is burned per furnace load Heat transfer mostly by Radiation

Fig: No: 6.4 Metallic Radiation Recuperators6.4.2 Convective Recuperators Hot gas through parallel small diameter tubes Tubes can be baffled to allow gas to pass over them again Baffling increases heat exchange but more expensive exchanger is needed

Fig: No: 6.5 Convective Recuperators6.4.2 Radiation/Convective Hybrid Recuperators: Combinations of radiation & convection More effective heat transfer More expensive but less bulky than simple metallic radiation recuperators

Fig: No: 6.6 Radiation/Convective Hybrid Recuperators6.4.3 Ceramic Recuperators: Less temperature limitations: Operation on gas side up to 1550 C Operation on preheated air side to 815 C New designs Last two years Air preheat temperatures