Alternate Fuel for Engine (Alcohol)

Introduction

The very purpose of testing the engine is to verify whether the engine is performing well as per the specifications given by the manufacturers. Also, the tests are also conducted to find the effects of different parameters like temperature, pressure, altitude differences, climate difference, etc on the performance of the engine.

There are different types and methods of testing the engines performance under different conditions. The sole purpose of this blog is to introduce the effects of different parameters on the working performance of the engine as well as to find out the methods or change in system parameters so that the overall efficiency of the engine will improve.

The basic task of mechanical engineers is to reduce the cost and weight of engine per kW and this should be achieved at possible running cost. The number of parameters which effect the engine performance are so many. The study concerning the performance of the engine is limited to a few factors only as B.P., bsfc, thermal efficiency, mechanical efficiency, speed and some more factors like pollution, A:F ratio and the inlet conditions. The useful range of these parameters is also limited by the factors like mechanical loading, overheating and knocking.

Performance Parameters:

The performance of an engine is an indication of degree of success for which engine is designed. The degree of success is compares on the following basis:

a.      Brake Power Developed or BMEP,

b.      Specific Fuel Consumption,

c.      Specific power output,

d.      Pollution produced from the engine.

The use of engine for normal and industrial purpose decides the relative importance of these given parameters. The specific power output is more important in Marine engine whereas specific fuel consumption is more important for Industrial engines.

In order to evaluate the performance of engine, certain basic parameters are chosen and the effects of various design parameters  and operating parameters are studied.

The basic parameters which can be considered are:

a.      The brake power and mechanical efficiency,

b.      Thermal efficiency,

c.      Specific fuel consumption,

d.      Volumetric efficiency,

e.      Exhaust emission.

Performance of SI Engines:

Normal engines are used at constant speed but under variable load conditions for power generation and many domestic applications. Similarly, the engines are used under variable speed and load like automobile engines. Therefore, the performance characteristics of the engine are discussed for variable load conditions when speed is constant and performance characteristics under different conditions like variable load and speed.

The most important parameters which are of interest are IMEP which indirectly exhibits the I.P. developed and maximum mechanical stresses to be faced by the engine components. Another parameter is mechanical efficiency which is an indicator of frictional losses in the engine caused by moving parts of the engine. The other two parameters are specific fuel consumption and brake thermal efficiency which are responsible for economical running of the engine. The last factor is volumetric efficiency which is important to indicate the amount of the air fuel mixture taken in during suction stroke by the engine which is responsible for the power to be developed by the engine.

Also, there are some design parameters like compression ratio and atmospheric parameters like temperature, pressure and humidity which also directly affects the performance and overall efficiency of the engines.