What are the advantage of CNG over petrol and diesel engine? Answer:
CNG engines create less pollution than petrol and diesel engines. As it is using compress natural gas power develops more than the others and also develops more torque in the engine. which leads to give a lower fuel consumption. |
| | The Advantages of Compressed Natural Gas
The Environmentally Clean Advantage | Compressed natural gas is the cleanest burning fuel operating today. This means less vehicle maintenance and longer engine life.| | CNG vehicles produce the fewest emissions of any motor fuel.| | Dedicated Natural Gas Vehicles (NGV) have little or no emissions during fueling. In gasoline vehicles, fueling emissions account for at least 50% of a vehicle’s total hydrocarbon emissions.| | CNG produces significantly less pollutants than Petrol & Diesel.| | Tailpipe emissions from gasoline operated cars release carbon dioxide, which contributes to global warming. This is greatly reduced with natural gas.| The Maintenance Advantage | Some fleet operators have reduced maintenance costs by as much as 40% by converting their vehicles to CNG.| | Intervals between tune-ups for natural gas vehicles are extended 30,000 to 50,000 miles.| | Intervals between oil changes for natural gas vehicles are dramatically extended–anywhere from 10,000 to 25,000 additional miles depending on how the vehicle is used.| | Natural gas does not react to metals the way gasoline does, so pipes and mufflers last much longer.| The Performance Advantage | Natural gas gives the same mileage as Petrol in a converted vehicle.| | Dedicated CNG engines are superior in performance to Petrol engines.| | CNG has an octane rating of 130 and has a slight efficiency advantage over Petrol.| | Because CNG is already in a gaseous state, CNG Vehicles have superior starting and drivability, even under severe hot and cold weather conditions.| | CNG Vehicles experience less knocking and no vapor locking.| The CNG Cost Advantage | Natural gas is cheaper per equivalent gallon than Petrol (an average of 50% less than Petrol).| The Safety Advantage | Surveys indicate that CNGVehicles are as safe or safer than those powered by other fuels. A 1992 Australian Gas Assocition survey of more than 8,000 vehicles found that with more than 278 million miles traveled, CNG Vehicle injury rates per vehicle mile traveled were 34% lower than the rate for Petrol Vehicles. There were no fatalities reported–even though these vehicles were involved in over 1,800 collisions.| The Financial Incentive Advantage | Some States offers a 50% investment tax credit for each vehicle converted to natural gas. This 50% credit on state income tax features a three-year, carry-forward option.| | A federal tax deduction is also available for the cost of conversion.| CNG Conversions
Converting a Petrol-Powered car to CNG requires only minor engine modifications. To learn more about converting your car, please contact a certified CNG conversion technician. What are the major benefits of natural gas as a transportation fuel?
EconomicsOn a gallon-equivalent basis, natural gas costs an average of 50 to 60 percent less than Petrol and Diesel. Natural gas is a clean-burning fuel that reduces vehicle maintenance. Many CNG Vehicle owners report that oil changes are needed only every 15,000 Km. Standard spark plugs last as long as 60,000 Km. Natural gas, unlike liquid fuels, cannot be siphoned from a vehicle. Fuel theft is an on-going concern of fleet managers. Vehicles can be “fast filled” in five to six minutes using compressed gas stored in cascades of natural gas cylinders or fueled overnight on a “timed fill” basis in about five to eight hours. Many private fleet fueling stations use a combination of fast fill and timed fill. | EmissionsNatural gas is the cleanest burning alternative fuel. Exhaust emissions from CNG Vehicles are much lower than those from equivalent Petrol-powered vehicles. For instance, CNG Vehicle emissions of carbon monoxide are approximately 70 percent lower, non-methane organic gas emissions are 89 percent lower, and oxides of nitrogen emissions are 87 percent lower. In addition to these reductions in pollutants, CNG Vehicles also emit significantly lower amounts of greenhouse gases and toxins than do Petrol vehicles.
Dedicated CNG Vehicles produce little or no evaporative emissions during fueling and use. For Petrol vehicles, evaporative and fueling emissions account for at least 50 percent of a vehicle’s total hydrocarbon emissions. Dedicated CNG Vehicles also can reduce carbon dioxide exhaust emissions by
almost 20 percent.
Exposure to the levels of suspended fine particulate matter found in many U.S. cities has been shown to increase the risk of respiratory illness. Diesel exhaust is under review as a hazardous air pollutant. Natural gas engines produce only tiny amounts of this matter.
Greenhouse GasesPer unit of energy, natural gas contains less carbon than any other fossil fuel, and thus produces lower CO2 emissions per vehicle mile traveled. While natural gas vehicles (CNG Vehicles) do emit methane, another principle greenhouse gas, any slight increase in methane emissions would be more than offset by a substantial reduction in CO2 emissions compared to other fuels.
CNG Vehicles also emit very low levels of carbon monoxide (approximately 70 percent lower than a comparable Petrol vehicle) and volatile organic compounds. Although these two pollutants are not themselves greenhouse gases, they play an important role in helping to break down methane and some other greenhouse gases in the atmosphere, and thus increase the global rate of methane decomposition.SafetyVehicles that run on clean burning natural gas are as safe as vehicles operating on traditional fuels such as Petrol. In fact, many school transportation managers choose natural gas to power their school buses because compressed natural gas, unlike Petrol, dissipates into the atmosphere in the event of an accident. Petrol pools on the ground creating a fire hazard.
In the US a survey was taken of more than 8,000 vehicles that cumulatively traveled approximately 278 million miles from 1987-1990. The survey found that the injury rate for CNG Vehicles per vehicular mile traveled (VMT) was 37 percent lower than the rate for Petrol-powered fleet vehicles and 34 percent lower than the entire population of registered Petrol vehicles. In addition to the lower injury rate, no deaths were recorded for the CNG Vehicles in the survey. In contrast the deaths associated with the Petrol fleet vehicles surveyed came to 1.28 deaths per 100 million VMT. The US national average was 2.2 deaths per 100 million VMT for all U.S. Petrol
There are two fundamental reasons for this excellent CNG Vehicle safety record: the structural integrity of the CNG Vehicle fuel system and the physical qualities of natural gas as a fuel.
The fuel storage cylinders used in CNG Vehicles are much stronger than gasoline fuel tanks. The design of CNG Vehicle cylinders are subjected to a number of federally required “severe abuse” tests, such as heat and pressure extremes, gunfire, collisions and fires.
While fuel storage cylinders are stronger than Petrol fuel tanks, the composite material used to encase the tanks are fundamentally more susceptible to physical damage than metals under abusive conditions. For this reason, composite materials on CNG Vehicle cylinders must always be properly handled and protected. Incidents involving natural gas cylinder ruptures revealed that some form of chemical attack or physical damage to the composite overwrap on the cylinder was involved.
CNG Vehicle fuel systems are “sealed,” which prevents any spills or evaporative losses. Even if a leak were to occur in an CNG Vehicle fuel system, the natural gas would dissipate into the atmosphere because it is lighter than air.
Natural gas has a high ignition temperature, about 650 º C, compared with about 350 º C for Petrol. It also has a narrow range of flammability; that is, in concentrations in air below about 5 % and above about 15 %, natural gas will not burn. The high ignition temperature and limited flammability range make accidental ignition or combustion of natural gas unlikely.
Natural gas is not toxic or corrosive and will not contaminate ground water. Natural gas combustion produces no significant aldehydes or other air toxins, which are a concern in gasoline and some other alternative fuels.
The natural gas delivery system also has an excellent — and proven — safety
record. According to statistics from the U.S. Department of Transportation, the 1.9 million Km natural gas transmission and distribution system is the safest way to transport energy in the United States.
CNG Vehicles use the same energy that has safely and comfortably heated homes and cooked meals for more than 100 years.Where are CNG Vehicles used now?
Approximately 100,000 CNG Vehicles are on U.S. roads today. CNG Vehicles have a long-established record in Europe, Canada, New Zealand and Australia, as well. Italy has been using natural gas as a vehicular fuel since the 1940s, with more than 350,000 CNG Vehicles. In Canada, nearly 20,000 CNG Vehicles operate with a network of 220 public fueling stations. Argentina has 680,000 CNG Vehicles, and Russia has more than 30,000. Worldwide, nearly two million CNG Vehicles are in use, in countries now including Uzbekistan, Venezuela, Mexico, the Philippines and Indonesia. How do CNG Vehicles work?
The only major difference between a Petrol vehicle and an CNG Vehicle is the fuel system. Natural gas is compressed to between 3,000 and 3,600 pounds per square inch (200 bar) and is stored on board the vehicle in cylinders installed in the rear, undercarriage, or on the roof. When natural gas is required by the engine, it leaves the cylinders, passes through a master manual shut-off valve and travels through a high-pressure fuel regulator located in the engine compartment. The natural gas is injected at atmospheric pressure through a specially designed natural gas mixer where it is properly mixed with air. Natural gas then flows into the engine’s combustion chamber and is ignited to create the power required to drive the vehicle. Special solenoid-operated valves prevent the gas from entering the engine when it is shut off.What about the vehicle’s power?
Petrol vehicles converted to natural gas are subject to a small power loss when running on natural gas; however, vehicles designed specifically to run on natural gas will have no loss of power and may even have greater power and efficiency. Natural gas has a 130 octane rating, compared with 87 to 96 octane rating of Petrol.How much energy does Compressed Natural gas release compared to petrol?
A direct answer to your question is that the energy content of natural gas (CNG) is about 47 MJ/kg or 40 MJ/m3. (gross heating value). The values for a typical petrol are 60 MJ/kg and 44 MJ/liter. Another comparison on an energy basis is that 1 kg of CNG is equivalent to about 1.33 liter of petrol or 1.22 liter of diesel. Or on a volume basis 1 m3 of CNG is equivalent to about 1.10 L of petrol or 1.0 L of diesel. When making comparisons you may also need to take into account the relative energy efficiency of the engines that use the various fuels. Generally engines that are designed for natural gas fuel are slightly more efficient than a similar petrol engine (because they can run at a higher compression ratio). The CNG and diesel engines of similar size will have a much the same thermal efficiency.What is the miles per gallon equivalent of natural gas compared to gasoline?
If the CNG Vehicle is an original Equipment Manufacturer (OEM) model, it will have been designed to make the most of the excellent properties of Natural Gas – eg it will have a higher compression ratio than the petrol model and different ignition timing – and you could expect to see an improvement in performance and fuel consumption on an energy basis. This might be about 5% or more. Of course you might then drive faster, and not have any advantage. If the car has been converted from Petrol to CNG and you can choose to run on either fuel (ie a bi-fuel vehicle) then it is not possible to make the most of the higher octane rating of the CNG. In this case the change in fuel consumption will depend very much on the vehicle and engine design and on the conversion equipment used and how it is tuned. In this case you might expect an increase of possibly 5% in consumption. However the tune may be optimized to a particular power and speed range and if you can hit this you might get a small improvement. There may be more scope to achieve this on a high capacity engine with reserves of power. On a smaller engine there may be a noticeable drop in power and your consumption could increase if you try to match the old on-road performance.Cylinders in Accidents
A pressurized gas cylinder is probably the strongest component on the vehicle. Vehicles that totally destroyed in collisions show the only discernible component being the intact gas cylinder. It is unlikely that
cylinders will rupture due to collision impact.Regarding the danger of fire from leaking cylinders, all we have is the experience to date that indicates that such an event is unlikely to occur. In North America there was a problem with leaking type 4 designs from a particular manufacturer, but there has never been an ensuing fire. The risk of fire from leaking cylinders must be low since there are well over a million CNG vehicle installations worldwide that have not experienced such problems.It is worth pointing out that natural gas is lighter than air and in the unlikely event of a leak from piping or container the gas will dissipate upwards quite quickly. In the case of petrol and LPG the vapors given off is heavier than air and will tend to pool near the ground. This is where there is a strong risk of some ignition source. In general terms diesel ranks high in terms of safety, but most people rank Natural Gas next.What are the factors which affect the fuel efficiency of CNG?
In the first place let us list the energy content of the fuels you mention. Using units of MJ per kilogram, the net heating values of petrol, diesel, LPG and CNG are about 45, 43, 46, and 44; the net heating value does not include the heat in the water vapor of the combustion products. If you look up the gross heating values – which do include this, the values are different (higher). So the differences between the fuels are not large. But the values will also vary quite a lot depending on the composition of the fuel – particularly for CNG and LPG.We now need to consider the way in which different engines use the fuels – in particular the efficiency. The engine thermal efficiency is a function of many different factors but perhaps the most important one is the engine compression ratio. The higher the compression ratio the higher is the theoretical and also the actual efficiency. The maximum compression ratio (CR) different fuels can tolerate in fact defines the efficiency. Since diesel used in a compression ignition engine can operate at say 14:1 the diesel will be expected to have the highest efficiency – lets say 40% as an upper limit. The next highest efficiency in the fuels comes from CNG, which can operate at say 12:1. with an efficiency of say 35%. It is possible to run an engine on CNG at 14:1 but that is the very upper limit. We would not expect to be able to run petrol and LPG engines at much more than 9:1 and an efficiency of about 30%.
These efficiencies are the upper limits and at full load – in normal operation they will be lower than the values quoted, but in much the same proportion. The main reason for the differences is the variation in limiting CR for the different fuels. So here is a starting point for a discussion of the differences in efficiency.As far as fuel energy comparisons go (and this does not take into account the different engine efficiencies), 1 kg of CNG is equivalent to about 1.33 liters of petrol or 1.22 liters of diesel – but of course occupies a greater volume. Or 1 cubic meter of CNG at atmospheric pressure is equivalent to 1.10 liters of petrol and 1.00 liters of diesel.Note that there are a lot of other factors that we have not considered – for example the diesel engine will be much heavier than the other engines, and the Petrol fuels will need pressure vessels to contain them. Having established how much energy you get from the different fuels and how efficiently the different engines can use the fuels, you will be able find out how much they cost and then work out a cost per km or mile. In many countries CNG will come out as best value and that diesel will be next, followed by LPG and then petrol. But prices do vary a great deal. Incidentally if you have a petrol engine that has been converted to use CNG you will not achieve the high efficiency quoted above because the compression ratio will be fixed at the level required for petrol – you will only get the benefit of higher efficiency in an OEM.What are the economics of small vehicle conversion?
In very general terms the smaller the vehicle the longer is the payback period for the cost of conversion. This is because the fuel consumption – and therefore savings – for the smaller vehicles is lower, and at the same time the cost of conversion does not go down much with vehicle size. The cost of the fuel control system stays much the same and the price of a smaller storage cylinder will not be much lower (and in a small vehicle it is more difficult to find a space for the cylinder).It may be difficult to justify the conversion on an economic basis, but this does depend on annual mileage. Do a rough sum on the basis of saving half (or whatever the price differential is in your area) of your fuel costs in a year. You should expect better than a three year payback on the basis of economics.Environmental benefits and lower maintenance costs will be small.Check where you would be able to find space for the storage cylinder which must be sized to meet commuter needs. And of course allow something for the satisfaction of knowing that you are lowering your output of hydrocarbon emissions.Is driving around with cylinders full of gas under pressure dangerous?
Thick-walled reinforced aluminum cylinders, steel cylinders or 100% composite materials are used to store compressed natural gas (CNG) as a vehicle fuel. These cylinders are manufactured and tested in compliance with strict regulations, and have withstood severe abuse testing under conditions far more stringent than tanks designed for storing gasoline. Natural gas vehicles submitted to test crashes up to 52 miles per hour, which have been totally destroyed, but show little or no damage to the compressed gas cylinders (CNG). Bonfire and dynamite tests push cylinders to temperature and pressures exceeding specified limits showing that compressed natural gas (CNG) cylinders are durable and safe. Of course, as with all fuel systems, these cylinders are not indestructible and should be inspected periodically to ensure that no surface damage has occurred.In which countries are natural gas vehicles popular?
Natural gas as a vehicle fuel has a long and established record in Europe, Canada, New Zealand, Australia, and in the U.S.A. Other countries are recognizing the benefits of CNG Vehicle’s, and plan to expand the use of CNG Vehicle.In Europe, Italy has been using natural gas as a vehicle fuel since the 1920’s and has about 370,000 CNG Vehicle’s. The Italians have a network of 280 filling stations to support their use of compressed natural gas (CNG). Russia has about 75,000 CNG Vehicle’s and a fuelling network of some 250 stations. Outside of these countries, there are now several thousand CNG Vehicle’s in Europe and a slowly growing fuelling station infrastructure.Argentina has 700,000 CNG Vehicle’s – the largest fleet in the world – and is converting more than 3,000 vehicles a month and has over 950 fuelling stations in operation and more than 100 under development. Venezuela has a national CNG Vehicle programmers and will be installing 60 fuelling stations and converting vehicles.Canada has about 36,000 vehicles converted to natural gas, and the government-supported NGV programmer has created a number of incentives. The Canadian government provides cash incentives for fleets to convert their vehicles, and hopes to use CNG for 10% of the entire country’s future vehicle fuel requirements.In the U.S.A. there are now about 68,000 vehicles fuelled on natural gas. Natural gas vehicles have been in use there since the late 1960s, but comparative prices with gasoline and state-of-the-art technologies are only now making natural gas economically and technologically competitive with gasoline vehicles. There are about 1,200 private and public refueling stations.What are the conversion factors for natural gas?
Methane values are fixed and can be found in any chemical handbook, while the composition of natural gas varies with source and time so try to find a local value. Approximately, 1kg CNG is equivalent to about 1.33 liters (L) of petrol or 1.22 L diesel. And 1 cu meter of CNG is equivalent to about 1.10 L of petrol or 1.00 L diesel.