PERFORMANCE OF A FOUR STROKE ADIABATIC DI DIESEL ENGINE
Extensive research is going on in the area of improvement of the engine thermal efficiency. In diesel engines approximately only one-third of the fuel energy is converted into useful work and major part of the energy is lost to cooling water. In an adiabatic engine (or insulated engine), the energy loss through cooling system is avoided by applying a layer of insulating material over the walls of the combustion chamber. The commonly used insulating materials are ceramic coatings such as silicon nitride, silicon carbide, zirconia (zirconium oxide) etc. As per the literature the partially Stabilized Zarconium (PSZ) is quite useful for the adiabatic engine application because of its excellent insulating characteristics, adequate strength and thermal expansion characteristics. Further this improves fuel economy, reduces, emissions and further reduces noise due to a lower rate of pressure rise. In the present investigations an adiabatic engine is developed with air gap insulation over the piston and cylinder liner, PSZ coated cylinder head and valves. With the higher temperatures in the combustion chambers in an adiabatic engine, widely available low cetane fuels like alcohols (which have high latent heat of vaporization) can also be burnt so that the ever-increasing demand for imported diesel can be reduced. In the present investigations a computer program has been developed in C language for an insulated engine and with that the theoretical results are obtained and then the same thing is compared with experimental results of adiabatic engine.
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Electron transfer reactions are at the heart of many biological processes. Whereas time-resolved electron paramagnetic resonance (EPR) is normally too slow to directly observe primary photochemical events, it has the unique capability of detecting the spin dynamics of radical pairs that often result from electron-transfer processes. In the last decade, such radical pairs have gained major interest as one possible mechanism by which migratory birds are able to sense the direction of Earth’s magnetic field for the purpose of navigation. The idea of a radical-pair based compass is quite old, but only recently candidate biomolecules, the cryptochromes, have been discovered. These proteins were proposed to form radical pairs upon illumination with blue light. Using time-resolved EPR together with point mutations of the respective proteins, we could demonstrate for the first time that cryptochromes indeed form such spin-correlated radical pairs. Furthermore, details of the spin–spin interaction in the radical pairs could be revealed from spectral simulations showing that cryptochromes are in principle well suited for being the compass molecule in, but not restricted to, migratory birds.
The Reduction of Heat Losses to the Diesel Engine Cooling System
The benefits of applying thermal insulation to the exhaust ports and combustion chamber components are predicted using a computer simulation of a highly rated turbocharged DI diesel truck engine. Comparisons are made between a standard engine and engines with the exhaust port, cylinder head, piston and cylinder liner insulated individually or in combination. The necessity of re-optimizing engine conditions when heat losses through the combustion chamber walls are significantly changed is also examined. The importance is recognized of developing techniques of reducing heat losses to the engine cooling system which can be applied at low cost and with minimal changes to existing engine designs. Potential methods of achieving these objectives are reviewed and their effectiveness assessed. This paper also describes the successful testing of a ceramic liner located in the exhaust duct of a diesel engine during more than 1000 hours of engine operation.