25-09-2014, 11:40 AM
INFLUENCE OF INJECTOR OPENING PRESSURE ON THE REDUCTIONOFTHE HARMFULEXHAUST EMISSION WITH THREE LEVELS OF INSULATION COMBUSTION CHAMBER
INFLUENCE OF INJECTOR.docx (Size: 120.57 KB / Downloads: 14)
ABSTRACT:
Studies were conducted on exhaust emission of direct injection (DI) diesel engine with different levels of low heat rejection (LHR) such as 1.ceramic coated cylinder head 2. Air gap piston and air gap insulated liner and 3. Ceramic coated cylinder head along with air gap insulation with pure diesel operation with variedinjector opening pressure.Exhaust emissionof particulate matters and oxides of nitrogen (NOx) were determinedatvarious values of brake mean effective pressure(BMEP) of the engine particulate emissions were measured by AVL smoke meter ,while NOx by chromatograph NOxanalyzer .engine with different levels of low heat rejection(LHR) combustion chamber showed comparable particulate emissionand comparableNOxemissions than comparing it with conventional engine. However exhaust emission reduced with an increase of injector opening pressure with different version of combustion chamber.
INTRODUCTION:
CONVENTIONAL ENGINE:
The internal combustion engine (ICE) is an engine where the combustion of a fuel (normally a fossil fuel) occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit In an internal combustion engine the expansion of the high-temperature and high-pressure gases produced by combustion apply direct force to some component of the engine. The force is applied typicallytopistons, turbine blades, or a nozzle. This force moves the component over a distance, transformingchemical energy into useful mechanical energy. The term internal combustion engine usually refers to an engine in which combustion is intermittent, such as the more familiar four-stroke and two-stroke piston engines, along with variants, such as the six-stroke piston engine and the Wankel rotary engine. A secondclass of internal combustion engines use continuous combustion: gas turbines, jet engines and most rocket engines, each of which are internal combustion engines on the same principle as previously described.
LOW HEAT REJECTION ENGINE:
The subject of Low Heat Rejection (LHR) Engine has been given considerable attention recently as engine builders struggle to find remaining avenues to improve economy and lower emissions.
Energy conservation and efficiency have always been the most concern of engineers with internal combustion engine. The diesel engine generally offers better fuel economy than its counterpart petrol engine. Even the diesel engine rejects about two third of the heat energy of the fuel, one third to the coolant, and one third to the exhaust, leaving only about one third as useful work output. Theoretically if the heat rejected could be reduced, then the thermal efficiency would be improved, at least up to the limit set by the second law of thermodynamics. Low heat rejection engine aim to do this by reducing heat lost to the coolant. The diesel engine with its combustion chamber, piston surfaces and valves insulated by ceramics andair gap provided within the piston is referred to as low heat rejection (LHR) engine. A large number of studieson performance evaluation of LHR engine have been carried out recently.
There are three different types of LHR engine: low grade, medium grade and high grade LHR engine. Low grade LHR engine [1] is the one which is obtained by providing thermal barrier coating over the piston surfaces or cylinder walls, medium grade LHR engine [2] is the one which is obtained by providing the air gap insulated piston and the high grade LHR engine [3] is the one which is obtained by providing the air gap within the piston material as well as thermal barrier coating is provided over the piston surface, valves and piston liners etc
CERAMIC INSULATED CYLINDER HEAD:
The use of low conductivity engineering ceramics for the cylinder head in combination withconventional cast iron combustion chambers, has received considerable attention in recent years by most of the major engine manufacturers. This approach has obvious attractions, since the ceramic is restricted to the region where its low thermal conductivity and high temperature capability can be best exploited. The use of both thermally sprayed coatings and solid ceramics are inherently brittle and cannot accommodate any permanent strain thus localized high stresses, which in metallic components would be reduced by local yielding, are liable to result in catastrophic failure. Furthermore ceramics and metals are dissimilar in nature and cannot be joinedby the conventional processes of brazing or welding. The useof screw threadedfastenings is also desirable since these usually produce unacceptable stress concentrations in the ceramic. These are many other formidable problems arising from the use of ceramic insulation are being tackled in Automobile Engineering’s long term work. Indeed some ceramic may be necessary in the insulated piston to withstand the highest levels of insulation that are now achievable. In consequence of the long time scale anticipated for the ceramic developments, readily available all-metal technologies such as air gap insulation.
OPERATING CONDITIONS:
Test fuel used in the experiment is diesel. Different injector openingpressure attemptedin this experiment was 190, 230 and 270 bar. The various combustion chambers used in the experiment were conventional combustion chamber ,lowgrade insulated combustion chamber with ceramic coated cylinder head (LHR-I), medium grade combustion chamber(LHR-II) with air gap insulated piston and air gap insulated liner and high grade insulated combustion chamber (LHR-III) withceramic coated cylinder head, air gap insulated piston and air gap insulated liner . The engine was started with diesel fuel and allowed to have a warm up for about 20 minutes and the test were performed according to the procedure and results were tabulated and comparative studies of exhaust emissions were reported at different operating conditions of compression ignition engine. A conventionalengine some connections are to be made they are emission measuring machine, smoke meter, exhaust Temperature measuring instrument. The engine is started and allowed to warm-up for about 15 minutes. The readings on dynamometer scale (load) time taken for 10cc of fuel consumption. NOx, CO, HC emission in emission measuring instrument, exhaust temperature and smoke measurement in smoke meter have been recorded. This procedure is repeated by changing the loads fromno Load, 3 Kg, 6Kg, 9Kg, 12Kg and 15Kg. After this work the pistonisover changed with newly machined air gap insulated piston. The above said procedure is repeated.
CONCLUSION:
With the analytical investigations it is concluded that the air gap thickness is suitable for LHR engine and with this we obtain the reduction in the fuel consumption and increase in thermal efficiency from that of conventional engine also the emissions like HC & CO are comparatively reduced and increase in NOx emission is obtained which can be reduced by a modern catalytic converter. However pollution levels improved with engine with various configurations of LHR combustion chamber at an injector opening pressure of 270 bar in comparison with 190 bar .