Performance and Emission of CNG Fuelled SI Engine at Variable Compression Ratio

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 5, Issue 7, July 2015)

436

Performance and Emission of CNG Fuelled SI Engine at

Variable Compression Ratio

Tushar P Vithalkar

1

, Prof Dinesh Y Dhande

2

1_{M.E. Student,}2_{Assistant Professor, Department of Mechanical Engineering, AISSMS College of Engineering, India} Abstract—Thepetrol engines can be operated with natural

gas with a few changes. The characteristic of the natural gas combustion is different from petrol, which ultimately produce less engine power. With regard to the oil prices and concerns about greenhouse gas emissions, the need for a cleaner and more efficient engines. So automakers are looking to improve the performance and efficiency of the engine and at the same time compliance with the emission standards. Compressed Natural Gas (CNG) is one of the most promising alternatives to conventional energy sources to combustion engines of different types of fuel. The auto-ignition temperature, octane and the heating value of methane is much better for use in internal combustion engines in comparison to CNG fuel is cheap compared to other conventional fuels is an added advantage of CNG over petrol are the sole and appropriate mixing. due to the high octane CNG engine functions smoothly with high compression ratio without knocking. With the improvement of the part of the load and efficiency.

In the present work, experimental studies on a single cylinder air cooled SI engine be performed and evaluate performance parameters and the emission characteristics The aim of this study is to improve the output power with CNG as an alternative fuel by the search for new or high compression ratio for the same engine by the cylinder head modification The tests are carried out in the stationary state and provided full load for both petrol and natural gas , and finally a comparative analysis between petrol and CNG for its performance parameters and emissions.

Keywords—CNG, Compression Ratio, emissions characteristics, Performance Parameter, Octane rating

I. INTRODUCTION

Today, the problem of alternative fuels is becoming more serious. In recent years the price of petrol and diesel is almost twice increased. Therefore, fuel consumption is very important. It is a known fact that petrol engines can easily be converted to run on compressed natural gas (CNG) or liquefied petroleum gas (LPG). The burning process is quite the same, and has similar parameters such as temperature, pressure, etc. One of the most important is the octane. Methane, propane and butane, a higher octane number (RON) and therefore the burning process can optimize for a higher performance and lower power consumption.

This optimization is provided by additional device because the petrol engines will usually not factory equipped for alternative fuel. The increased use of petroleum fuels by cars not only caused fuel shortages, price increases, higher import bills and economic imbalance, but also causes health risks because of its toxic emissions. Conventional fuels in automobiles used cause toxic pollutants, asthma, chronic cough, deterioration of the skin, shortness of breath, eye and throat problems and even cancer. In recent years, issues of improving the environment (CO2, NOx and ozone reduction) and energy have in the cares of the world and more important. Natural gas is a good alternative fuel in order to improve these problems because of its abundant availability and characteristics of cleaner burning. And we can again increase the power of engine when operated on CNG by using higher compression ratio..

II. METHODOLOGY

Components and actual arrangement is discussed in the methodology for the performance parameter the test set up is prepare and the experiments will be performed at variable load operation and with different compression ratio to calculate the performance parameters for petrol and CNG

The details of the various components of the test facility are: Single - cylinder petrol engine, different compression heads dynamometers, exhaust gas analyser, pressure reducer CNG, CNG storage cylinder, oil pump, tachometer, oil tank, fuel tank, electronic weight (50 kg)

A simple system reduction and mixers are used in petrol engines with carburettors to run on natural gas. For petrol engines to operate on naturel gas see the additional points below

The kit includes gas pressure regulator / CNG Reducer Mixer Gas cylinder valves and cylinders, petrol filling valve, pressure pipes.

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International Journal of Emerging Technology and Advanced Engineering

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TABLE I

TECHNICAL SPECIFICATION OF ENGINE

No Specification

1 Type 2 Stroke

2 Cooling Type Forced Air Cooled 3 Displacement 145.45 cc

4 Max Power 5.5 kW at 5500 rpm 5 Max Torque 12.1 Nm @ 3300 rpm 6 Ignition Type CDI

7 Transmission Type 4 forward and one reverse 8 Clutch Type Wet multidisc type

The figure below shows the project setup on which all the performance and emission test was carried out

Figure1. Actual project setup

III. COMPRESSION RATIO

Compression ratio is method to increase the performance of an engine but while operating on petrol the range of compression ratio is limited it is not possible to operate this engine at higher compression ratio due to knocking problem. But when this engine can be operate with CNG then it is possible to operate at higher compression ratio without knocking so the compression ratio of that engine get change and find out new and higher ration for that engine which operate on CNG and gives more power output.

So the tests are carried out at variable compression and find out the performance and emission parameters.

IV. RESULTS

All the sample is obtained in this paper plates at a speed of 4500 rpm for the conditions of variable load and compression ratio from 7 to 7.92, and the result during the experiment are presented discussed bellow

A. Fuel consumption

Fuel consumption has the property to decreases with increasing load. The graph shows in Figure 4 is the fuel consumption with different load conditions for petrol and CNG at different compression ratio to 7 and 7.92.

In figure 2 shows that fuel consumption get decreases with load for both the rpm at 4000 and 3500 rpm for normal compression ratio that is 7

Figure2. Load VS mf at CR of 7

In figure 3 shows the fuel consumption at Compression ration 7.92 so with increase in CR the fuel consumption is decrease with 3500 rpm and normaly equal at 4000 rpm but it is less then normal CR.

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International Journal of Emerging Technology and Advanced Engineering

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B. Brake Specific Fuel Consumption

Brake Specific Fuel Consumption is decreasing with increase in load at CR 7 and 7.92.

Figure4. Load VS BSFC at CR 7

In figure 4 and figure 5 shows BSFC get reduce when engine operated at CNG at normal CR and with increase CR 7.92 also.

Figure5. Load VS BSFC at CR 7.92

C. Brake power

When the engine operated at normal CR of 7 at 4000 and 3500 rpm Speed shows in figure 6 the brake power get decrease for CNG and while operate on petrol brake power increases.

Figure6. Load VS BP at CR 7

But whe engine operate on increased CR of 7.92 Shows in figure 7 with CNG then Brake power increase on CNG than Petrol for both the speed 4000 and 3500 rpm at variable loading.

Figure7. Load VS BP at CR 7

D. Brake thermal efficiency

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Figure8. Load VS Thermal Eff. At CR 7

Like normal CR of 7 when it is increase to 7.92 the thermal efficiency is also increase for CNG fuel than petrol from figure 9.

Figure9. Load VS Thermal Eff. At CR 7.92

E. CO Emission

CO emission for petrol is very much higher when engine is operated at normal CR but when operated on CNG emission of CO is vary less due to complete combustion of gaseous fuel from figure 10 When the CR get increases the CO emission for both the fuel get decreases than the normal CR emission level.

Figure10. Load VS CO

F. CO2 Emission

CO2 emission for CNG is less than petrol for normal CR

and when the CR gets increased to 7.92 the CO2 emission is near about same.

Figure11. Load VS CO2

G. HC Emission

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Figure12. Load VS HC

V. CONCLUSION

The overall result shows that SI engine can be easily operated on CNG fuel but the engine cannot developed desired power according to CNG fuel. When we operate that engine on higher compression ratio the engine produce more power than petrol.

So variable or higher compression ratio SI engine is better option for CNG fuelled combustion and get more power output from same engine.

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