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Friday, 16 January 2015

GASEOUS FUEL APPLICATION IN ENGINES : LPG AND CNG

In order to reduce our dependency on fuel like petroleum, it is very important to carry out research on some alternative fuels for compression ignition & spark ignition engines. Because these alternative fuels are very important for environmental protection point of views. 

The researches were carried out by using alternative fuels and decreasing consumption of petroleum and hence reducing the concentration of toxic elements in the product of combustion. With the applications of gaseous fuels such as LPG, it is observed lower emissions of Hydrocarbon and carbon monoxide.

We will consider gaseous fuel e.g. LPG and CNG application in engines separately

There are some parameters for examples operating cylinder pressure, air-fuel ratio, compression ratio and ignition timing and these parameters should be study in this literature review paper in order to secure lower emissions and good performance of engines.

Introduction

Scientists and Engineers have a dream project to develop such fuels and engine that will consume less quantity of fuel and emit very less toxic elements in product of combustion so that we may save our environment with these harmful toxic components produced during the combustion of fuels.

Government of every country has decided some standard norms and also rules, law in order to control the pollution of air. Air pollution control board of each country has to supervise the norms, law and rules on a specific frequency basis.

There are big possibilities of air pollution in urban areas due to continuous increase in numbers of vehicle on daily basis. IC engines are frequently used in transportation system as IC engine has handsome power density and thermal efficiency also. It is observed big increase in air pollution due to frequent use of IC engine. 

It is also observed in a Survey that approximate 30 Billion tons of Carbon die oxide is added (by each country) to environment air in each year. Transporting Vehicle, weather these are with CI or SI engine, are responsible for polluting of air via emitting toxic and harmful components during combustion of fossil fuels. 

If we study deeply about the emission of fossil fuels, we will come to know that Hydrocarbon, carbon mono-oxide and nitrogen oxide are more dangerous as these affects health directly. Ozone is also emitted by combustion of such fuels but ozone is not affecting health directly because they will pass through a series of reactions and after that it will be harmful to health. 

Hence ozone is considered as secondary toxic components of emitted during combustion of such fuels. Emissions from the combustion of fossil fuels are responsible for air pollution, acid rain, global warming and other different kind of health hazards. It is very important for engineers and researchers to search alternative fuels in order to avoid such harmful emissions.

As we know that LPG is produced as bi-product during the process of extraction of crude oil and natural gas. Main components of LPG are butane and propane. Octane no. of LPG is also higher as compared to petrol. LPG has octane number of 105 while for petrol it is about 91 to 97.

It is observed that with the application of LPG in IC engine, we may secure higher thermal efficiency and economical consumption of fuel as compare with the application of unleaded gasoline. Now these days LPG i.e. liquefied petroleum gas and LNG i.e. liquefied natural gas are in demand for the transporting vehicles due to better performance in efficiency and economy of fuels.

LPG gas emits lower carbon die-oxide (CO2) as compare to gasoline due to higher octane no (105) and lower carbon. Before some years this study was carried out to use LPG in modern engine and now approximates 4 million vehicles are operating with LPG as fuel. There was some medium, light and heavy truck also those were operated with gasoline fuel but later converted with LPG kit.

Lot of researches and test were carried out to know the updated status of performance of LPG fuel in SI engines and it is observed vehicle those are operated with LPG fuel will have 40 % lower hydrocarbon, 60 % lower Carbon monoxide and reduced quantity of carbon die oxide as compared with fossil fuels operated vehicles.

We must note it that fuel’s properties depends only on the chemical constituents that determines the characteristics such as thermal efficiency and power density and various kind of combustion product.

There are some modifications required for LPG vehicle kits where a strong fuel tank will be required sustain a pressure more than 150 PSI. Let us consider a spark ignition engine with LPG fuel kit.

Let us consider the chemical constituents of LPG and Gasoline with the help of following table.

Survey is carried out in order to study about the current status of performance of Liquefied petroleum gas and its emission properties.

Thirumal Mamidi investigated the impact of different compression ratios on the performance & emission properties of Spark ignition engine operating with Liquefied petroleum gas. 

He had concluded that brake thermal efficiency will be increased with the increment in value of compression ratio .As we know that Liquefied petroleum gas has a higher octane rating & thus we may say that the engine (operating with LPG) will have ability to run effectively, without any knock, at relatively higher compression ratios.

The emissions of carbon mono-oxide and HC increase with the increment in the value of compression ratio, Load and speed. If we consider the case of spark ignition engine operating with Liquefied petroleum gas, we will observe that the duration of combustion will be decreased because fuel burning rate will be higher in this case.

Thus temperatures and pressures Predicted for LPG will be higher as compared to the gasoline. Gaseous fuels combustion such as combustion of Liquefied petroleum gas occurs in a uniform mixture of air & fuel and that will lead to the reduction in the possibilities of incomplete combustion. 

Emissions of HC, CO2 and CO increase with the increase in the load on engine. Let us consider some graphs where we may easily see about the performance of engine at various load with different compression ratio. We will also see the characteristics of emissions at various load and compression ratio.

Conclusions

On the basis of above literature review, we may conclude that Liquefied petroleum gas will be better alternative for gasoline fuel because LPG has good octane no. as compared to Gasoline fuel. LPG has better performance and toxic emissions will also be lesser as compared to Gasoline fuels.

Hence, we may conclude that LPG will be the best substitute of gasoline fuel in future for transport vehicles. There are some more details that we have secured after study of this literature review of application of LPG in place of gasoline fuels and these are as described below.
  1. If we will not consider the mechanism of delivery and storage system of fuel then LPG engine is very similar to petrol engine and LPG engine will provide better performance and better thermal efficiency.
  2. Engine operation will be smoother as compared to petrol engine.
  3. It is concluded that LPG engine emits 33 % lesser CO2 as compared to petrol engine.
  4. It is also concluded that LPG engine emits 45 % lesser CO2 as compared to diesel engine.
  5. It is concluded that LPG engine emits 82 % lesser nitrogen oxide as compared to petrol engine.
  6. It is also concluded that LPG engine emits 63 % lesser CO.
  7. It is concluded that LPG engine emits 40 % lesser Hydrocarbon as compared to petrol engine.
  8. It is also concluded that LPG engine emits 70 % lesser Hydrocarbon as compared to diesel engines.
  9. LPG engine will emit Emission consisting less toxic components as compared to petrol and diesel engines.
  10. Carbon depositions will also be reduced in case of LPG engine thus life of engine will be increased.
So it is cleared from above points that Liquefied petroleum gas will be best alternative for gasoline fuel in coming future for the transport vehicles.

 Let us move towards next post  

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1 comment:

  1. Thanks for sharing the useful post on LPG used in gaseous fuel application engine. This explains well regarding the benefits of LPG over other gas.
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