Efficiency Increasing System

Topics: Internal combustion engine, Thermodynamics, Air-fuel ratio Pages: 9 (2250 words) Published: February 8, 2013



The concept of increasing the fuel efficiency of a petrol engine in this project, is to pre-heat the intake air which is flowing through the carburetor. The humidity in the atmospheric air affects the petrol vapourisation in the carburettor. Therefore, by pre-heating the inlet air to the carburettor for a considerable amount, the vapourisation can be ease and in turn complete combustion is achieved. Moreover by reducing the water vapour to the engine, the steam formation in the engine can be reduced pitting of the engine cylinder, piston and exhaust pipe.

The pre-heating of inlet air to the engine can be achieved by fixing a heat exchanger inside the exhaust pipe. The atmospheric air is sucked through the heat exchanger to the carburettor. The air which is flowing though the heat exchanger gets heated by the engine exhaust gas. This reduces the water vapour in the inlet air and the temperature of the air is raised. The temperature raise causes complete combustion in the engine and it is also more suitable for warming up the engine in cold conditions.


The output of the engine exhaust gas is given to the input of the ignition system, so that the proper ignition is occurred. In this case, the efficiency of the engine is also increased. The exhaust gas is given to the heating chamber as shown in figure. The exhaust hot air is used to pre-heat the input air into the ignition system. So far this type of system has not been introduced in two wheelers. So this may be very useful to two wheelers without any complication and maintenance. But the air pre-heater design depends on the exhaust pipe fitted to the particular two wheeler engine.

The design is simple, cheap and does not give any trouble to the engine. So far the vehicle which is used for this project has covered a distance of more than 500kms, without any complications.



There is limited range of air fuel ratios, in a homogeneous mixture, which can be ignited in SI Engine. These limits are about 7:1 A/F by mass (0.14:1 F/A) on the rich side and about 20:1 A/F (0.05:1 F/A) on the lean side in the single cylinder Engines. The properties of different air-petrol mixtures in this range are shown in Fig.

a. Mixture requirements for maximum power

Maximum power is obtained at 12.5:1 A/F (0.08:1 F/A). Maximum Energy is released when slightly excess fuel is introduced so that all the oxygen present in the cylinder is utilized. More fuel than this does no help. It is disadvantageous because the combustion of a large excess of fuel with the same amount of oxygen results is smaller Energy release due to partial combustion and more carbon monoxide is formed.

Mechanical efficiency is maximum, at maximum power position.

b. Mixture requirement for minimum specific fuel consumption

At full throttle maximum efficiency occurs at an A/F ration of about 17:1 (0.08:1 F/A ration). Maximum efficiency occurs at a point slightly leaner than the chemically correct A/F ration because excess air ensures complete combustion of fuel when mixture is not perfect: and lower maximum temperature associated with the lean mixture favorably affect the chemical equilibrium and specific heat of gases. However the mixture is made too lean, the flame speed is reduced so much that the large time losses over come the above mentioned beneficial effects, and the efficiency falls off.

c. Mixture Requirements For Steady State Operation

A carburetor is mechanical device designed to full fill the following conditions.

1. Meter the liquid in such quantities as to produce the air-fuel ration required by the Engine at all the speeds and loads. 2. Automoise the fuel and mix it homogeneously with air.

In stationary Engines the desired air-fuel ratio is...
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