ABSTRACT.
It’s an olden practice to use vegetable oil as a working fuel in diesel engine. It was R. Diesel who first introduced vegetable oil as a fuel in his compression ignition (CI) engine. In past few decades vegetables oil have emerged as an alternative fuel. Vegetable oils are either non-edible or edible. Few of the edible oils are soya oil, peanut oil and cottonseed oil. The non-edible oils are mahua oil, jatropha oil, karanj oil, rubber seed oil, neem oil etc .The use of vegetable oil directly in the engine creates different problems such as separate engine deposits, injector chocking, injector pump failure, piston ring sticking, lubricating oil thickening and gum formation. These problems are due to the poor volatility and high viscosity. Three techniques can be used to reduce the viscosity of vegetable oils, namely heating, dilution/blending, and transesterification. The vegetable oil was preheating to an order of temperature 90o, 70o, and 500C, before inward bound the engine; many of its parameters can have values very close to that of diesel fuel. The factors like the energy,cost and time consumption in production of conventional fuels are reduced in case of vegetable oils. Vegetable oils have less emission of carbon dioxide into atmosphere. The various characteristics like Performance, combustion and emission at different load values were calculated with a single cylinder Compression ignition engine and comparison is done with that of diesel fuel and vegetable oil. The various parameters like brake power, brake specific fuel consumption, and thermal efficiency have been evaluated. The exhaust gas temperature, carbon mono oxide, smoke, nitrogen of oxide and hydrocarbon emission were compared with diesel .The aim of this study is to find out the effects on operating parameters of the engine like injection timing and fuel injection pressure on performance of diesel engine with preheated vegetable oil and diesel
1 Introduction
At present the world has been modernized and industrialized, hence there will be rapid consumption of petroleum resources which are very inadequate in quantity. so there is a necessity to discover new options which are renewable, easily available and unlimited in nature. In this modern world the petroleum fuel resource become necessary for automobile and various mechanical purpose, but these fuel resources are limited. Due to this as compare to past rate of fuel price is increasing continuously for regular retreating supply and complete of demand. So this is not a new idea because of vegetable oils used in diesel engines. Initially Rudolf Diesel supplied vegetable oils in diesel engine as a working fuel. In past years few decades occupied an alternative place. Vegetables oil has similar properties to that of fossil fuels such as physical composition and combustion characteristics. The most favourable things about vegetable oils are their renewable and eco-friendly behavior as well as they are obtained from different plants and seeds which can be available easily in our rural areas. Vegetable oils are both edible or non-edible. Some of the edible oils are palm oil, sunflower oil, rice bran oil, and cottonseed oil. The non-edible oils are mahua oil, jatropha oil, rubber seed oil etc. However, the vegetable oil is directly used in the diesel engine because it creates some durability and operational problems. However the poor volatility, cold flow nature and high viscosity of the vegetable oils. Some run time complication like fuel nozzle chocking and piston ring sticking are occurred [1]. To reduce the high viscosity and increase volatility of the vegetable oils are pre- heated [2, 3].the emission of some harmful as CO (carbon monoxide), CO2 (carbon dioxide), un-burnt hydrocarbon, NO (nitrogen oxides) and smoke can be controlled by replacing the diesel fuel by vegetable oil as a fuel [2, 3, 4, 5]. Fuel changes methods accept in the current learn can decrease the viscosity while different problems in the properties like cetane number silent live. The injection timing and pressure of diesel engine should be modified to overcome some performance difficulties occurred due to the mismatch of chemical structure of diesel fuel and vegetable oil . It is standard to injection timing predominance all single engine individuality significantly. The reasons are that injection timing predominance the mixture of the air and fuels and thus the complete combustion process. A few researchers have suggested that, the fuel injection timing is the advance; when we used of vegetable oils instead of diesel fuel in diesel engines. Due to high bulk modulus of vegetable oils, the injection pressure and valve timing should be more advanced to make the proper burning of fuel [6-7]. Unsuitable pumping and fuel spray characteristics of vegetable oil (30–200 at 40℃) due to higher viscosity. When compared to diesel fuel (4 at 40℃). For long running, preheated vegetable oils are appropriate as fuels for diesel engines.
3 Production of vegetable oils processes
There are certain processing operations. Which are came out on the oil-bearing biomass containing. An installation for the extraction of vegetable oils consists of seed storage, seed clearing, and grinding, pressing, degumming, filtration and oil storage tanks. All impurities have to be removed from the raw material, which has to be dried operations: either decanting in successive tanks, or direct filtering through a filter. For each stage in the production chain, a certain number of factors may modify or influence the quality of the oil obtained downstream. Consequently, a certain number of precautions have to be taken at each stage of the process.
Figure 1: Vegetable oil quality in relation to the production process
3.1 seed storage
Seed can be stored more than some months to in by process scheduling. They have to be regularly aired to heat build-up and prevent acidification [13]. The moisture content in the seeds should be below 9%in weight then only the batches are held to be stabilized [38]. This is the highest seed moisture content which must be current for pressing which is current available on the market to operate efficiently [39].
3.2 seed cleaning
The elimination of impurities such as soil, stones, metallic objects etc in the seed must be done up to a maximum of 2% [38] by weight. The impurities when improved in their levels in oil reason wear in the press. This reason is due to the thermal rupture of oil cell walls at temperatures above 100°C [39, 40]. Clogging in diesel engine is due to raise level of impurities which in turn increase phosphorus concentrations in the oil [13, 41].
3.3Seed grinding
The seed grinding process is the most important steps. The preheated seeds are grind on the roller mill. Crush the cleaning seed to the right consistency by Mechanized grooved rollers and hammer mills. The seeds are grinded in the form of powder. Seed powder is then heated to help the extraction of the oil. More impurities are free with the oil when the seed are grinded although it procedure allows more oil to be pressed out. These impurities must be removed before the oil can be deemed edible.
3.4 Seed Pressing
Fuel vegetable oil is obtained by simple cold pressing of oil bearing seeds and fruits. The oils extracted vary in quantity and quality. Some of the dependence in seed pressing are on the type of press, moisture content, seed variety, heating or not, and on the cleanliness of the seed [35]. Conventionally, two types of press are available [35]:‘whole cylinder or ring’’ presses for capacities under 100 kg of seeds processed per hour; ‘‘strainer’’ presses, which can be used to press up to 2 tons of seeds per hour. The quality of the oil obtained depends upon the Pressing condition. The water in the oil is due to condensation which in turn due to high humidity and a seed temperature below that of the ambient air. Preheating seeds to 20oC helps to improve the extraction rate. Oil quality directly affect by temperature and speed of pressing [34]. The phospholipids content can be affected by the pressing temperature and oil extraction yield can be affected by speed of pressing. The extraction rate is correlated with press flow. A high flow rate reduces the extraction rate. It is recommended not to exceed a temperature of 80oC inside the press. Higher the temperature higher is the phospholipids content, that’s why cold pressing is desirable [33, 35]. During pressing, it is preferable to opt for continuous press operation to obtain uniform oil and press cake characteristics. The extraction rate lies within a range of 80–85%. The extent of variations depends on the outside temperature (lower yield in cold weather) and seed moisture content [33, 45].
3.5 Degumming
The mixing of vegetable oil with high temperature water is called degumming .Where the phospholipids of vegetable oils are hydrated and some particles are formed. The drying process of vegetable oil is after centrifugation and removal of solid particles. Which makes them extremely energy-intensive and produces dissipate water [46].Degumming is the first step in processing for vegetable oil which contain amount of hydra table phosphatides. This step help in production of the lecithin and reducing the phosphatide removal load in neutralization. Degumming is an important part of processing which is used for the removing of fatty acids, phosphatides is other materials which include glycerol, metals ,resins, protein meal and carbohydrates.
3.6 Filtration
The better quality oil fuel may be obtained by removing such as solid particles, phospholipids and waxes through some chemical processes. Oil purifications are most important and necessary steps for using vegetable oils sustainably in engines [33, 35]. Filtration can be done directly in vegetable oils by the pressing through a plate filter press. Filtration must be done among temperatures of 20oC to 60oC to remove every soluble element [33]. Over 60oC, there is high risk of oil oxidation. Which reduce shelf life? Direct filtration is used to the plate filter. In fact, friction insides the pressing leaving the oils to the temperature 60oC for filtration. The vegetable oils must be filtered at 10 mm for the prevention of impurities in the oil and any pollution [36].
3.7 oil storage.
The storage condition is most important considerations. Construction of storage tanks must be done to provide proper and sufficient isolation from other oils and also from external contaminations.
Storage is a good quality and clean containers. The various parameters should be received into account to guarantee optimum oil storage [35]:
(i) The oil storage area must be cool,
(ii) The vegetable oil must be as clean,
(iii)The oil can be storage as air-tight containers.
Light is conducive to oil oxidation and acidity. Storage period should be minimized to avoid and analyzed before the start of each processing run to establish proper processing conditions. Storage of oils more than a long duration causes oil oxidation. Hence causes high viscosity and filtration problems in the engine.
4 Properties of vegetable oil
The vegetable oils and diesel fuel have similar characteristics to be burnt in the diesel engines. Density, flash point, pour point, fire point, net calorific value, cetane number and kinematic viscosity are several of the properties. The usable capacities of vegetable oils similar to diesel fuel are its Density, viscosity, flash point, pour point and cetane number. The properties of a fuel can be determined by quality. These properties also indicate performance of engine and its emission. The different types of standard which is used to define the limit of the fuel properties are ISO, ASTM, ENs, etc. The most extensively followed standard is ASTM. The value to the fuel properties must be laid in the range for the satisfaction of the standard engine emission and its performance. The most important part to use any liquid as fuel is study its fuel properties.
4.1Kinematic viscosity
The kinematic viscosity of vegetable oils varies in the range 30-40centistokes at 380C. Their molecular weights are in the range of 600to900 g/mol [14], which are about 3 times higher than those of the diesel fuels [12, 13, 14]. Lubricating oil has the most important properties of viscosity. The process of a fluid film of a lubricant between the friction surface and the frictional heat generation particular conditions of load, bearing spread and lubricant supply mostly depend upon the viscosity of the lubricant and also on its oiliness at some extent. When large working clearances exist between the friction surfaces, high viscosity oil is generally recommended to cushion the intermediate application of load. But the vegetable oils are the high viscosity. The viscosity of an oil decreases with increase of temperature as a result of decrease in intermolecular attraction due to expansion. Hence it is always necessary to state the temperature at which the viscosity was determined. Viscosity affect’s diesel engine operation, mainly due to reduction in the maximum injection by major pressure drop in the injection pump and in the filters, injectors or nozzles, and poor atomization and vaporization, hence incomplete combustion [15,16,17,18,19,20]. Lubrication problems are regularly observed at low temperature in a few injection pumps, resulting in substantial mechanical losses [12, 13, 18, 21–23]. Preheating the oil prior to starting up the engine can be a solution [22, 24, and 25]. Another solution consists in mixing the oil with diesel oil [8, 15, 25, 26, 27, and 28] or starting up the motor with pure diesel oil before switching to vegetable oil.
4.2 Density
Density is another most important property of the vegetable oil. Density is a measure of the amount of oils contained in a given volume. The mass per unit volume is called density. The diesel fuel has its density 10 % less than that of vegetable oils. This needs to be taken into consideration to regulate fuel flow rates. Density is considered at 15.5oC.Vegetable oil has densities range 900 to 930 at15.5oC.
4.3 Flash point
These of oils are defined as the lowest temperature at which the vapor pressures of the oils are sufficient to maintain the flame. These are noticeably lower for diesel fuels than for vegetable oils (+100 oC) and its rate have no particular express influence more engine performance and combustion efficiency. It is more a safety parameter for storage. The usual precautions for the storage and handling of petroleum products therefore go beyond what is needed for vegetable oils [12].The flash point shows, the volatility of the vegetable oils.
4.4 Net Calorific Value (NCV)
The net calorific value of a fuel is as the amount of net heat obtainable by the complete combustion when unit quantities of the fuels are completely burnt. Higher calorific value for fuel is desired because it facilitates the heat release during combustion and improves engine performance. The NCV of vegetable oils is lower than that of diesel oil. The difference between the mass NCV of vegetable oils and that of diesel oil is around 10–15% [13, 15]. However, the volumetric NCV of vegetable oils about 5–6% less due to high density, on average, than that of diesel oil. Combined with the density, the NCV is used to determine the volume flow rate for vegetable oils compared to diesel oil, so as to inject identical energy [29]. The consequences of the low NCV value of vegetable oils compared to that of diesel oil are around 8% extra consumption of vegetable oil, a drop in engine power and a drop in thermal efficiency [13,16,19,24,30,31,32].
2.5 Cetane number.
Cetane number is a prime indicator of the quality of fuel used in compression ignition (CI) engines. The time between injection and combustion for a diesel engine is characterized by it. The higher it is, the more flammable is the fuel. Then the cetane number of a vegetable oil is defined as the percentage by volume of cetane in a mixture of cetane and naphthalene which exactly matches in its knocking characteristics with the vegetable oil under test. The cetane number of the vegetable oil can be improved by adding substances such as ethyl nitrite, isoamyl nitrate and acetone peroxide. The cetane numbers of low speed, medium speed and high speed diesel engines should be at least 25, 35 and 45 respectively
5 Standards for vegetable oil
5.1 History
In 1937 Gaupp firstly studies about in diesel engines there are the use of vegetable oil [88]. In diesel engine what the effect of physical properties of vegetable oil he alerts that. The pour point, viscosity and iodine value are physical properties, affected diesel engines. At that time, vegetable oil content’s such as phosphorus and water effect was not point of worry [89]. In 1982, in the International Conference on Plant &Vegetable Oils as Fuels, Pryde proposed a first acceptable vegetable oil standard [90]. He found that ASTM 975 specifications for Fuel Oil No. 2 did not followed by vegetable oils. He reported that some analytical methods (such as methods of measuring 90% distillation temperature, cetane number and the flash point) did not ensemble to vegetable oils. He recommended for working on modification of vegetable oil. This work was done to successfully and to vegetable oil given them physico-chemical properties compliant with standard No. 2 ( transesterification, preheating) quite than modifiable standard No. 2. The standard have several specifications had some limit value, He suggested an adaptable standard. Vegetable oils must be recognized as experimental fuel specified by him. The suggested for using specifications only for things determination of the quality and quantity of fuel and not for heating it for specification of fuel use [90]. In1980s, us petroleum oil was cheaper prices. The work started by Pryde was never taken forward because the major interest was in biodiesel. Thereafter, the leader in vegetable oil became Germany research. In 1994,as a fuel Germany planned a draft quality standard for rapeseed oil. In 1996 the proposal had improved. In 2000, for becoming Weihenstephan Quality Plan it improved for rapeseed oil fuel to be heated [30]. in 2006 Weihenstephan Quality Plan standard was reviewed. It was done to become a quality pre-standard DIN V 51605. Now a order works to convert final standard DIN 51605 from pre-standard DIN V 51605[89]. In Table 3, the improvement of standard from the 1980s to today is shown. In phosphorus content the most important evolutions are observed. The limit of phosphorus was dropped in pre-standard DIN V 51605 from 30 to 12 ppm phosphorus forms deposits that clog injectors and valves. The walls of the combustion chamber are damages. It is phosphorus to catalysts ( used in exhaust mufflers to oxidize un-burnt wastes). So; main attention was on phosphorus. In modern diesel engines the catalysts used can be deactivated by earth alkali metal (e.g. Ca & Mg). In vegetable oils it is important organize parameters. Within the last few years commission has also been working on Na and K specifications [89, 91
5.2 Pre-standard DIN V 51605
Pre-standard DIN V51605 is accepted a reference in using vegetable oil as a fuel within the group of people [92]. The authors state that using of rapeseed oil is achievable. But offer recommended either using it as a mixture of rapeseed oil and diesel fuel or adapting the engine in a dual-fuel mode with fuel preheating [32, 91]. Also, several limitations are appears by pre-standard DIN V51605. First of all pre-standard do not follow by rapeseed oil. In regular combustion ignition engines, These are some importance such as the kinematic viscosity and cetane number are too limits and not right to the physical and chemical properties of vegetable oils for use. Based on these standard condition, while various ordinary engines are fuelled with that oils but palm oil cannot be used as fuel [93-96]. The investigation method has not been produced for diesel fuels and vegetable oils. There are need to be estimated for external validity and consistency to vegetable oils. [32]. The individual the nature of complex mixtures of petroleum-derived goods, their different methods frequently greatly necessary analytical tools are too fine ideas for the study of simple mixtures of vegetable oils. . In developing countries these tools cannot be affordable to small cheapest specialized laboratories and also the fourteen parameters favorite in the pre-standard applicable for useful in the case of regular applications. We will locate out dissimilar specifications that are improved for particular applications in terms of parameters like investigation methods and limit values in the next section. This condition will be investigation in relation to the specifications in pre-standard DIN V 51605.
6 Diesel fuel standards
The diesel fuel standards are affecting on the diesel engine performance and emissions. Diesel fuels are obtained from the refining of crude oil. Diesel fuels is a mixture of various petroleum components such a paraffin’s, naphthenic and olefins, each with their own chemical properties and physical properties. The properties of diesel fuel must be balanced to give acceptable performance. This products can be used as fuel in diesel engines [75]. Generally this fuel can be containing amounts of chosen cracked distillates [76]. Diesel fuel is used in heavy vehicle such as cars and trucks etc [69, 77]. This standard at present covers different grades of diesel fuel. The grades are scheduled in order of increasing viscosity and density. The ASTM standards guarantee satisfactory fuel quality. Diesel fuel must at a standstill meet the standard recognized by ASTM. All fuel standards are related to the performance, operability, fuel, economy durability and emissions. Gummy residual fuel oil is used in diesel engine and marine engine. The diesel fuel chemical composition is changeable depending on the nature of the refining processes and original crude oil.
7 Oxidation stability of vegetable oil
For the storage the Oxidation stability of vegetable oils is a most important issue. The vegetable oil has high stage of polyunsaturated fatty acids. These polyunsaturated fatty acids can polymerize into insoluble particles such as other deposits, Sediments, gums, sediments, oxygen and high storage temperature [104,107]. The iodine value is much closer to oxidation stability [102]. The Oxidation stability of vegetable oils plays a most important role in determining the quality. The Oxidation stability is defined as the resistance of the oil and fats to degrade. The Oxidation stability is illustrious from storage stability. The storage stability is the oxidation may occur also during production and usages. The oxidation stability of vegetable oils is measured to the degree of double bond. The fuel instability is proportional to the number of double bond. The vegetable oils Oxidation stability also depends on the oil refining process, the presence of natural antioxidants and fatty acids distribution. The oxidation stability of vegetable oils is reducing as the un-saturation of the fatty acids increases. The un-saturated fatty acids are most susceptible to oxidation than fatty acid having one or more double bond [22]. The vegetable oil can be preferred for breeding programs and genetic modification due to its improved oxidation stability. The suggested oxidation stability experiment methods of American standards [109] and European standards [108] are contentious. The vegetable oil has oxidized for the period of improper storage. Sharma and Jain stated that there are different types of stabilities such as thermal; storage and oxidation in produce the fuel unstable [25]. The volatile acid attendance is reduced by the raise in conductivity. The oil stability index or induction time is time to reaction products appear [27]. The oil molecule is the presence of water [22]. The researchers have growth a method for the determinant of oxidation stability of vegetable oils [20].
8 Performance of vegetable oil
Performance of the vegetable oil can be expressed in terms of the brake- specific fuel consumption and brake thermal efficiency etc. The most important performance of the vegetable oils is the brake- specific fuel consumption and brake thermal efficiency. These performance parameters are determined by means of orderly diesel fuel and vegetable oils. The engine load wide-ranging from 18% to 90%in steps of 18%.The performance parameters, fuel inlet temperature etc was compared and determined.
8.1. Brake- Specific fuel consumption
Brake Specific fuel consumption is an important performance parameter of the vegetable oil. It defines consumption by unit of power and unit of time. The Specific fuel consumption normally lowers with the higher in engine load for all fuel. The Specific fuel consumption is higher with vegetable oil than that of diesel fuel in diesel engines. Diesel engines given are higher volume consumption [10, 16, 18, 22, 24, 31, 36, 37, 38, 39] for vegetable oil. Brake- specific fuel consumption has increase value on load at decrease fuel inlet temperature. The fuel inlet temperature is reducing as a load increased. For preheated vegetable oil, Brake Specific fuel consumptions have decrease speed at increase value than with the purpose of a diesel fuel operation. For specific fuel utilization, every fuel inlet temperatures are different through higher speed. The specific fuel consumption becomes nearer at the highest speed for both arranged diesel fuel and vegetable oil [11].
8.2. Brake thermal efficiency.
The thermal efficiency of vegetable oils as fuel is lower than diesel oil one [31]. The brake thermal efficiency is the ratio of the brake power to the supply fuel energy. The brake thermal efficiency of the vegetable oils is below due to poor combustion characteristics. The vegetable oils can be due to poor combustion ensuing from their high viscosity and little volatility [16, 31].The preheated vegetable oils was higher than brake thermal efficiency as compared to unheated vegetable oil. The preheated vegetable oils may be improved fuel atomization since of reduced fuel viscosity and increase volatility [8]. However thermal efficiency is relatively higher for vegetable oils than for diesel oil [36].
9. Combustion characteristic of vegetable oil
In diesel engine, the temperature and pressure raise to a high value due to only air is compressed through a high compression ratio (14:1 to 20:1). Fuel is injected through one or more jets into this highly compressed air in the combustion chamber. This spray envelope is created both by atomization and volatility of the fuel. A mixture of air and fuel forms at some location in the spray envelope and oxidation starts. The time lapse between the start of injection and begin of combustion is called ignition delay. It is the research time on the air-fuel mixture previous to combustion. The ignition delays of vegetable oils are longer than for diesel fuel. The cetane numbers of vegetable oils are lower than for diesel fuel. [12, 17,39]. However, ignition delay is not the major difference between the vegetable oil and diesel fuel, whereas the variation between cetane numbers is repeatedly substantial. Fort et al. [40], like Jalinier [41] published work in the 1980s in which they found that the ignition delay of vegetable oils was shorter than for diesel oil. These disagreements in the results may be due to the conditions under which ignition delays were determined. Vaı¨tilingom (1992) [12] showed that, with an air inlet temperature of 100 oC; the same ignition delays have the diesel fuel and vegetable oils, and ambient temperature of diesel fuels at 500oC the same evaporation characteristics as vegetable oils.
10 Emission characteristic of vegetable oil
The emissions exhausted into the surroundings pollute the atmosphere. Dissociation of nitrogen, combustion and impurities in the fuel and air are the major causes of this emission. Un-burnt hydrocarbon, oxides of nitrogen, carbon monoxide, Carbon dioxide and smokes are major things responsible for emissions. Which are mainly responsible for air pollution? These pollutants are known to cause serious health problems. Therefore there are laws on emission standards, which limit the amount of each pollutant in the exhaust gas emitted by an automobile engine. The exhaust gas emissions of vegetable oils are lower than that of diesel fuels. Vegetable oil mainly emits unburned carbon monoxide (CO), oxides of nitrogen (NOx), hydrocarbons (HC), and smoke emissions. These pollutant’s emissions are generally described less when engines fueled with vegetable oil.
10.1. Carbon monoxide (CO) emission.
The greatest carbon monoxide emissions are decided at rated power. Carbon monoxide is colorless but a poisonous gas. The carbon monoxide emissions with vegetable oils are higher as compared to diesel fuel. It decreases as the engine loads increases. Preheating of vegetable oil appears the result on carbon monoxide (CO) emission. The high viscosity of vegetable oil causes poor mixture, incomplete combustion and poor spray characteristics will be also be the source for carbon monoxide emissions. The carbon monoxide emission was smaller by means of preheating due to the progress in better fuel mixing and sprays characteristics. The cause given is the poor combustion of vegetable oils, which is due to their higher viscosity and little volatility.
10.2. Carbon dioxide (CO2) emission.
The carbon dioxide emission is very high as a diesel fuels use in diesel engine. The vegetable oil decrease in carbon dioxide emission compared to diesel fuel. The vegetable oil fuel higher carbon dioxide (CO2 ) emissions compared to preheated vegetable oil fuels. The carbon dioxide emitted from diesel engines running with vegetable oil does not add to greenhouse gases into the atmosphere as it is absorbed by plant growth in the following crop cycle. Carbon dioxide ( CO2) emission from vegetable oils is around 20% higher than from diesel oil due to poor vegetable oil combustion [16]. However, the problem for this case is that the performance from the engine was particularly poor, even with diesel oil.
10.3. Nitrogen oxides emission.
Nitrogen oxides commonly called NOx, the corresponding fact to a mixture of NO and NO2. Oxide of nitrogen present is exhaust gases of engine about 2000 ppm. Exhaust gases of engine mostly contain nitrogen oxide with a small amount of nitrogen dioxide.NOX is very undesirable. Oxide of nitrogen (NOX ) is created mostly by reaction of nitrogen present in the air. The nitrogen oxide emissions of reduce is continues to become more and more strictly year by year. Nitrogen can also be found in fuel blends. NOx emissions are often lower with vegetable oils compared to diesel oil (10, 16, 18, 24, 32, 36).
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