SEMINAR REPORT ON DUAL FUEL ENGINE
DEPARTMENT OF MECHANICAL ENGINEERING,
SUBMITTED TO- SUBMITTED BY- ER. AMIT AGRAWAL SHREESH CHAUBEY B. TECH. ME-3RD YEAR 1000440047
RAJA BALWANT SINGH ENGINEERING & TECHNICAL CAMPUS, AGRA
First of all I thank the almighty for providing me with the strength and courage to present the seminar.
I avail this opportunity to express my sincere gratitude towards Dr. B.K. Kushwaha sir, head of mechanical engineering department, for permitting me to conduct the seminar. I also at the outset thank and express my profound gratitude to my seminar guide Er. Amit Agrawal Sir for their inspiring assistance, encouragement and useful guidance.
I am also indebted to all the teaching and non-teaching staff of the department of mechanical engineering for their cooperation and suggestions, which is the spirit behind this report. Last but not the least, I wish to express my sincere thanks to all my friends for their goodwill and constructive ideas. CONTENT:- DUAL FUEL ENGINE TECHNOLOGY…………………..5 1. DUAL FUEL SIX STROKE ENGINE TECHNLOGY………7 1.1 STROKE ENGINE…………………10 1.2 GLOW PLUG –PREHEATER………..13 1.3 TYPE OF STROKE……….14 1.4 ADVANTAGE……………15 1.5 DUAL FUEL TECHNOLOGY…………16 1.6 METHOD OF INJECTION ETHANOL………17 1.7 EXHAUST GAS RECIRCULATION(EGR)………..18 2. DUAL FUEL(NATURAL GAS/DIESEL)ENGINE………….23 2.1OPERATING CHARACTERSTICS AND ADVANTAGE……24 2.2 APPLICATION………….26 2.3 DUAL FUEL (LPG/DIESEL) ENGINE……….28 2.3.1. EXPERIMENTAL SETUP&EXPERIMENTATION………29 2.3.2. RESULT&DISCUSION……………30 3. CONCULUSION………………..35 3.1 PERFORMANCE……………36 3.2 EMISSION……………………37 4. REFERANCE………..38 FIGURE CONTENT:- FIG-1(a)…………6 FIG-1(b)…………7 FIG-2……………9 FIG-3………….11 FIG-4……………23 TABLE CONTENT TABLE-1(PROPERTIES OF DUAL FUEL)…………….6 TABLE-2(SPECIFICATION OF THE TEST ENGINE)……….29 TABLE-3(MASS FRACTION OF LPG IN THE BLEND)……….31
Ø Dual-Fuel uses patented electronic control of diesel pilot injection to ignite a controlled pre-mixed charge of NG and air.
DUAL FUEL ENGINE TECHNOLOGY
Ø The system incurs no change to the base diesel engine, which runs according to Diesel’s 4-stroke cycle, at high compression ratio with compression-ignition of a lean fuel-air mixture. The non-intrusive nature of the technology enables a Dual-Fuel engine to operate on 100% diesel in the absence of NG.
Ø The high compression ratio of the diesel engine can be retained due to the high auto-ignition temperature of methane (352°C higher than diesel). Where spark-ignited NG engines have issues with the ignition of lean mixtures, the Dual-Fuel engine overcomes this with the diesel pilot injection. This pilot injection provides a multitude of ignition sites as the diesel spray droplets auto-ignite under compression. The result is that the Dual-Fuel engine is the first mechanism for the reduction of both NOx emission and combustion noise. engine can run with Lambda (excess air ratio) λ ≤2.
Ø Pilot injection is well understood and can be delivered by conventional diesel FIE. As with diesel combustion, the introduction of a pilot injection reduces the pre-mixed combustion phase. Similarly with Dual-Fuel , the small diesel pilot results in minimized diesel pre-mixed combustion.
1-DUAL FUEL SIX STROKE ENGINE TECHNOLGY:-
Ø The Present scenario of Fuel Consumption is well known to everyone. Everyday technical people talk about the depleting Fuel sources and Exhaust hazards. Particularly about the Diesel engines find their importance more than the Petrol engines due to their operating cost and Fuel consumption But Diesel engines have their demerits in the area of Exhaust and Power loss. Necessary steps have to be taken in order effectively use the Fuel available.
Ø The Six Stroke Engine’s Principle resembles the Double Stage Compressor. By this way effective Compression is done and the need for Turbocharger is completely neglected. We have also considered Cylinder’s position in Six Stroke engine. Also the Pollution (NOx) emitted by the Diesel Engines is also taken into account. We found the solution in the form of Dual fuel and Exhaust Gas Recirculation system. The Combusting Temperature is above 2000 F and this is the prime reason for NOx Emission.
Ø So an Alternative Fuel which can be combusted below the level of Diesel should be used. Moreover the availability and production cost must be taken into consideration. We found Ethanol as a better alternative for Diesel. The Cold Starting of the Engine is made easier using GLOW PLUG which is used to preheat the Charge coming inside the Combustion Chamber.
Ø In today’s world, the usage of Internal Combustion Engines is inevitable..Oxides of Nitrogen (NOx) are formed when Temperatures in the Combustion Chamber get too hot. At 2500 F, the Nitrogen and Oxygen in the Combustion Chamber can chemically combine to form Nitrous Oxides, which, when combined with Hydrocarbons (HCs) and the presence of Sunlight, produces harmful effects.
Ø In order to reduce these effects, a Dual Fuel technique is implemented in which ethanol is used as a Running Fuel which has less NOx emission than the Conventional Diesel Engines. In order to achieve such a High Compression Ratio , Efficiency.
Ø Six Stroke CI engine is found to be more suitable. Starting of CI engines during cold weather becomes severe when compared to the SI engines. The conventional method of circulating hot water is being replaced by GLOW PLUG, thereby diesel consumption during starting period is reduced considerably and quick starting is achieved Exhaust Gas Recirculation (EGR)
Ø This system also gets added up in the list so as to reduce the NOx effect. A simple recirculation circuit dilutes the incoming charge in the inlet manifold thereby reducing the combustion temperature to some 100 degree which optimally reduces the NOx problem.We also had the idea of implementing Turbo charger, but usage of six stroke engine .
1.1 SIX STROKE ENGINE
ü Considering the importance of cleaner, powerful and economical engine we have come up with this new idea for practical implementation of six stroke engine , which will be nearly 40% more fuel efficient than the existing four stroke engines. The engine is also more efficient and powerful than the existing six stroke and four stroke engines. The engine is also having the scope of using heavy fuels and biofuels.
ü The majority of the actual internal combustion engines, operating on different cycles have one common feature, combustion occurring in the cylinder after each compression, resulting in gas expansion that acts directly on the piston (work) and limited to 180 degrees of crankshaft angle.
ü According to its mechanical design, the six-stroke engine with external and internal combustion and double flow is similar to the actual internal reciprocating combustion engine. However, it differentiates itself entirely, due to its thermodynamic cycle and a modified cylinder head with two supplementary chambers .
ü Combustion and an Air Heating Chamber, both independent from the cylinder. Combustion does not occur within the cylinder but in the supplementary combustion chamber, does not act immediately on the piston, and its duration is independent from the 180 degrees of crankshaft rotation that occurs during the expansion of the combustion gases (work).
ü The Combustion Chamber is totally enclosed within the air-heating chamber. By heat exchange through the glowing combustion chamber walls, air pressure in the heating chamber increases and generate power for an a supplementary work stroke. Several advantages result from this, one very important being the increase in thermal efficiency. In the contemporary internal combustion engine, the necessary cooling of the Combustion Chamber walls generates important calorific losses.
ü The engine has better turbulence due to which the combustion is smooth and effective. The engine has better air pollution control than existing four stroke engines. The engine may be smokier with heavy fuels but the pollution level when compared to the existing heavy fuel engines will be within limit. With the use of conditioned heavy fuels, this sulphur smoke can be dramatically reduced and pollution can be reduced considerably.
BASIC ENGINE PARTS
Fig-3 (six stroke engine)
Inlet Valve: when open supplies fresh air into the engine.
Exhaust Valve: When open removes the burned gases from the engine Combustion chamber.
Valve: The valve connects the cylinder with the combustion chamber. Opens to permit the flow of compressed air from the cylinder to the combustion chamber and also to permit the flow of exhaust gases from the combustion chamber to the cylinder to drive the power stroke.
Heating chamber Valve: The heating chamber has been provided with a valve, to release the pure air into the cylinder. The valve makes scavenging much more effective than what is found in the existing six stroke or four stroke engines.
Fuel Injector: Highly pressurized is injected into the combustion chamber.
Cylinder: Supplies compressed air to the combustion chamber. It also aids in Providing better turbulence in the combustion chamber making combustion smooth and effective Combustion Chamber: The combustion of the compressed fuel occurs with the aid of the fuel pumped into the cylinder.
Piston: moving in the cylinder, gets power from the exhaust of the combustion chamber and the air from the heating chamber
1.2 GLOW PLUG:--PREHEATER
To preheat the cylinder before starting. One such method is the circulation of hot water into the water jacket of the cylinder.Glow plug emerges as a very good alternative. A heating element is placed nearby the fuel injector, which is being supplied with a very high current of 25-35 amperes for a period of 5 to15 seconds prior to the starting. The heat is transferred by means of combustion from the cylinder surface to the incoming air, thereby reducing time taken to heat the air medium.
WORKING OF GLOW PLUG
Fuel blend assists in using a heater for a better running condition .High latent heat and low vapour pressure reduces the temperature of cylinder wall which necessitates the use of Glow plug.
1.3 THE STROKES:
During the first stroke the inlet valve is opened and air is sucked into the Compression Chamber. The air is compressed in the combustion chamber.
The heating chamber valve is opened and the air sucked in by the cylinder is compressed and send to the heating chamber. Simultaneously the fuel is injected in the combustion chamber. Thus the combustion takes place inside the combustion chamber
The combustion chamber valve opens and the combustion gases is realased into the cylinder. The high pressure with which the exhaust gases are pushed out aids to obtain a power stroke. Simultaneously there is a heat exchange takes place between the combustion chamber and heating chamber which is filled with pure air.
The exhaust valve is opened, driving out the exhaust gases from the cylinder
By heat exchange through the glowing combustion chamber walls, air pressure in the heating chamber is increased. When the heating chamber value is opened the high-pressured air formed will enter the cylinder which will result in another power stroke.
When the combustion chamber valve opens, the expanded air is re-compressed and sends into the combustion chamber.
1.4 ADVANTAGES ;
Ø 30% reduction in fuel consumption and Two Power Strokes
Ø More powerful than the existing conventional engines.
Ø Heavy fuel Usage, Better Scavenging
Ø Dramatic reduction in pollution
FACTORS CONTRIBUTING TO ADVANTAGE:
v The heat that is evacuated during the cooling of a conventional engine’s cylinder head is recovered in the six-stroke engine by the air-heating chamber surrounding the combustion chamber.
v After intake, air is compressed in the heating chamber and heated through 720 degrees of crankshaft angle, 360 degrees of which in closed chamber (external combustion).
v The transfer of heat from the very thin walls of the combustion chamber to the air heating chambers lowers the temperature and pressure of the gases on expansion and exhaust (internal combustion).
v Better combustion and expansion of gases that take place over 540 degrees of crankshaft rotation, 360° of which is in closed combustion chamber, and 180° for expansion.
v The glowing combustion chamber allows the optimal burning of any fuel and calcinate the residues.
v Distribution of the work: two expansions (power strokes) over six strokes, or a third more than the in a four-stroke engine.
v Better filling of the cylinder on the intake due to the lower temperature of the cylinder walls and the piston head.
v Elimination of the exhaust gases crossing with fresh air on intake. In the six stroke-engines, intake takes place on the first stroke and exhaust on the fourth stroke.
v Large reduction in cooling power. The water pump and fan outputs are reduced. Possibility to suppress the water cooler.
v Less inertia due to lightness of the moving part
1.5 DUAL FUEL TECHNOLOGY
Dual fuel engine is one which operates with two different fuels. One is the igniting fuel (diesel) and other is the running fuel. We can find huge variety of running fuels from the present researches. One such fuel is ALCOHOL.
Under Alcohol, many types are found to satisfy the budding problem such as Methanol, ethanol, Butyl alcohol, etc. We Prefer Ethanol as the suitable running fuel because of the following properties listed.
| BOILING POINT
|| LATENT HEAT
| COMBUSTION ENERGY
IN 100 PARTS
Moreover some additional advantages related with ethanol are:
Ø It is not a fossil fuel (i.e.) combusting it does not cause any Green House Effect.
Ø It is Biodegradable which does not affect the environment.
Ø Higher oxygen content ultimately reduces the NOx emission and other harmful pollution
Ø The fuel is very much economical for long run.
Ø The compression ratio is high of the order 25-27.
Since the alcohols have very high self ignition temperature, so the design of theengine using ethanol as the primary fuel will be robust and expensive. So a general idea of using ethanol in dual fuel operation is practiced.
PRINCIPLE OF OPERATION
In dual fuel engine the alcohol is generally injected into the combustion chamber. Due to high self ignition temperature of alcohols, there will be no combustion with usual diesel compression ratios of 16-18. So a little before the end of compression stroke, a small quantity of diesel oil is injected into the combustion chamber through normal pumping techniques. The diesel oil readily ignites and this initiates combustion in the alcohol-air mixture also.
1.6 METHODS OF INJECTING ETHANOL
v Methods used are pneumatic spray nozzle, vapourizer, carburetor and fuel injector.
v Another important method that can be implemented is the direct injection of ethanol into the combustion chamber after the diesel fuel injection. By this way, alcohol cooling of the charge is avoided to a degree which will jeopardize the ignition of the diesel fuel.
v This system requires two complete and separate fuel systems with their necessary fuel feed systems.
v In the dual fuel engines, major portion of the heat release is by the alcohol supplied and this alcohol is ignited by a spray of diesel oil injection.
Ø The calorific value of alcohols is lower than the diesel oils and hence a larger quantity of alcohols has to be used for producing the same amount of power output.
Ø However the air requirement for combustion is lower and hence the energy content of the mixture is the same. Since the latent heat of vapourisation is very high, the temperature and pressure at the end of compression come down due to their evaporation. Hence if the alcohol Injection rate exceeds a limit, the injected diesel will not be able to ignite and hence the engine will fail to function.
1.7 EXHAUST GAS RECIRCULATION
NEED FOR EGR
During acceleration and normal running condition, the combustion temperature inside the combustion chamber is around 2000 Fahrenheit. This condition is favourable for the NOx formation. The nitrogen and oxygen in the combustion chamber can chemically combine to form nitrous oxides, which, when combined with hydrocarbons (HCs) produes harmful effect.
EVOLUTION OF EGR :-- General Motors in 1970
Ø The exhaust from the combustion chamber is being circulated back to intake manifold by a simple piping mechanism. By this way the fuel charge is diluted and temperature is reduced so as to reduce harmful emission.
Ø The amount of exhaust circulated is determined by the Electronic control unit (ECU).Depending upon the engine loading condition, the flow is allowed by the EGR valve which is actuated by ECU.
Conditions when EGR should not respond are:
Ø Higher accelerating conditions. During idling and cold start conditions. EGR has to work for a normal loading and running condition. This phenomenon is not really understood by the people early and they started to disconnect the EGR system from the Engine. To overcome the above listed problems, closed loop system was invented in the early 1980s. The working of such EGR system is explained below.
THE DESIGN CHALLENGE
Ø The EGR system of today must precisely control the flow of re-circulated exhaust. Too much flow will retard engine performance and cause a hesitation on acceleration. Too little flow will increase NOx and cause engine ping. A welldesigned system will actually increase engine performance and economy. As the combustion chamber temperature is reduced, engine detonation potential is also reduced
Ø It has a diaphragm that pulls open a valve stem, which allows exhaust to enter the intake manifold when ported vacuum is applied to it. Ported vacuum increases with throttle opening. A thermal vacuum switch prevents vacuum from reaching the EGR during cold engine starts.
Ø Lowering the amount of oxygen in the cylinder and the combustion temperature, NOx emission is reduced therefore at the source of origin. Cooling the recirculate gas enhances the effectiveness of EGR and thus the further reduction in NOx. Intensified EGR cooling serves to reduce NOx and exhaust smoke particularly at peak load.
Ø Increased EGR cooling has practically no effects on NOx and smoke emission at very low loads (1000 rpm, 2 bar), nevertheless this causes increased HC and CO emissions. Therefore, to control these emissions, an EGR cooler by-pass has to be installed. This by-pass serves to conduct partial flow or full flow of the exhaust gas depending on the load and speed. The EGR cooler will also be by-passed for engine cold start and warm-up.
Ø EGR can also be used by using a variable geometry turbocharger (VGT) which uses variable inlet guide vanes to build sufficient back pressure in the exhaust manifold. For EGR to flow a pressure difference is required across the intake and exhaust manifold and this is created by the VGT.
Ø The purpose of the Exhaust Gas Recirculation (EGR) system is to reduce engine exhaust gas emissions in accordance with EPA regulations.
Ø Part of the exhaust gasses from the combustion chamber is routed from the exhaust manifold through the EGR cooler, past control and reed valves, and are mixed with the intake manifold charge air. The addition of cooled exhaust gasses back into the combustion airflow reduces the peak in combustion temperature. Less oxides of nitrogen (NOx) are produced at lower combustion temperatures. The recycled exhaust gasses are cooled before engine consumption in a tube (radiator) and circulated
COMPONETS OF EXHAUST GAS IN EGR TECHNOLOGY
Ø The EGR Cooler is equipped with a single-pass cooler. Part of the exhaust gasses from the cylinders are directed through the EGR shutoff valve and through the cooler and reed valves, past the EGR modulated control valve and the mixer and then back The EGR shutoff valve and the EGR modulated control valve are control valves.
Ø The EGR shutoff valve is a pneumatically driven butterfly valve, located at the inlet of the EGR cooler. It closes when the exhaust flap or turbo-brake actuates, avoiding exhaust gas flow and excessive pressure in the EGR cooler and reed valves. The EGR modulated control valve is an electronically actuated butterfly valve located after the EGR cooler and reed valves, controlled by the ECU. This valve controls the exhaust gas flow for the intake manifold.
The reed valves work like a check valve, allowing flow of gas only in one direction, avoiding gas back flow when the intake pressure is higher than exhaust gas pressure. As the average exhaust pressure is lower than the intake pressure, the gas flow through the reed valves is possible due to exhaust gas pressure peaks — peaks slightly higher than the intake air pressure, which occurs as the engine exhaust valves open. During this peak of pressure, the reed valves open and allow gas flow to the EGR modulated valve and mixer.
Ø The purpose of the mixer is to ensure good mixing of the cooled EGR gasses with filtered charge air. Once the exhaust gasses are cooled and have completed their cycle through the EGR system, they are released into the EGR mixer. The recycled exhaust gasses are combined with the charged air and directed to the cylinder.
EFFECT ON EMISSIONS AND DRIVEABILITY
Ø Too little EGR flow may cause detonation and emission failure for excessive NOx. Because EGR tends to reduce the volatility of air fuel charge, loss of EGR causes detonation to occur.
Ø Too much EGR flow for driving conditions may cause stumble, flat spot and hesitation. Because EGR dilutes the air fuel charge, too much EGR for a given engine demand can cause a misfire. It is uncommon to see tip in hesitation, stumble and surging when too much EGR is metered.
2 DUAL FUEL (NATURAL GAS/DIESEL) ENGINES:
There are an increasing number of dual fuel, natural gas/diesel engines in operation worldwide. They provide a relatively easy and inexpensive option to higher polluting diesel engines in a wide range of vehicles. The degree of sophistication of these engines varies depending upon fuel control strategies, however, they have proven reliable in many parts of the world and continue to expand their market share, particularly in regions where diesel pollution is a major concern and health hazard.
2.1 OPERATING CHARACTERISTICS AND ADVANTAGES
Ø Most natural gas engines are either bi-fuel or dedicated. Bi-fuel engines are Otto cycle (spark ignited) that run on either natural gas or gasoline. The bi-fuel natural gas engine maintains two fuelling systems on board a vehicle: a natural gas system as well as a petrol system. While not necessarily optimised for natural gas operation, they tend to be more ‘environmentally friendly’ than petrol engines and have the advantage of running on petrol in the event that a natural gas fuelling station is not readily available.
Ø Dedicated natural gas engines are Otto cycle (spark ignited) that are operated only on natural gas. They tend to be optimised, that is they have a compression ratio designedto take advantage of the 130 octane of natural gas, and have been designed to take intoconsideration the combustion characteristics of the fuel so that the engine is very low polluting.
Ø Dual fuel natural gas engines are based upon diesel technology. The primary fuel is natural gas but they are designed to operate interchangeably with diesel as a ‘pilot’ ignition source (functioning on heat of compression and not with a spark plug). These engines also can operate on 100% diesel fuel. When idling these engines tend to operate on 100% diesel. As the vehicle begins to move to full load performance, an increasingamount of natural gas replaces the diesel fuel to 80% or more.
Ø This makes them especially valuable in circumstances where the use of natural gas is desired for environmental or economic reasons but where the natural gas supply is not available in all locations.
Ø It alsois relatively easy to convert a diesel engine to dual fuel operation.Some of the dual fuel engines are throttle controlled using a fumigation systemthat adds natural gas to the engine as higher speed is required. Other dual fuel systems are computer controlled to ensure that the optimal ratio of natural gas and diesel fuel is delivered to the engine depending upon load and performance requirements.
Ø These systems’ performance and emissions vary depending upon operating conditions and the sophistication of the control system, but generally they can achieve much lower emissions diesel engines, especially of NOx and particulate matter.
2.2 APPLICATIONS OF DUAL FUEL ENGINE
Dual fuel natural gas/diesel engines are becoming popular in many parts of theworld. The more expensive, sophisticated computer control systems are being introduced successfully in North America and Australia, and are being tested in European in anticipation of market entry. But their use in other parts of the world is expanding, particularly in Latin America, India, Pakistan, China and other parts of Asia. They tend to be used in large vehicles such as buses andrefuse trucks, but also have applications in smaller commercial diesel engine vehicles.
IMPORTANCE OF DUAL AVAILABILITY FUEL ENGINES
Ø Diesel engines can be converted as dual fuel natural gas engines relatively easily because typically there are no changes in the engine compression ratio, cylinder heads, or basic operation as a diesel cycle engine. Even the sophisticated computer controlled dual fuel systems are being developed as ‘bolt on’ technologies that can be removed if necessary, to resell the vehicle as a normal diesel engine.
Ø These conversions are easy to install and easy to maintain. This flexibility makes these engines very useful in many global markets.
Ø Some cities in various parts of the world are reaching epidemically poor air quality limits and need an immediate remedy to pollution caused by urban diesel vehicles. Natural gas provides both an environmental benefit and, in most markets, a cheaper fuel than refined petroleum products.
Ø This compensates economically over the vehicle’s lifetime for the additional cost of the natural gas equipment furthermore, the companies now developing and supplying these engines and dual fuel systems account for increased economic and employment opportunities in the countries they are located.
Ø Currently there are companies in Italy, the United Kingdom, United States, Canada and Australia, to name some, that are supplying a variety of dual fuel engines and technologies. Caterpillar Engine currently offers four different models of dual fuel capable engines that meet U.S. Federal and California emission standards.
Ø Detroit Diesel currently is developing a dual fuel, natural gas/diesel engine as well. Regulations that impede these engines and engine systems from market entry should not be brought into force. Rather, regulations that foster market entry of such dual fuel systems, subject to them meeting national, regional, or worldwide homologation requirements, should be encouraged. Suggested language in ECE Regulation R11 prohibiting dual fuel engines should be amended to allow for the continued use of these
2.3 DUAL FUEL (LPG &DIESEL) ENGINE
LPG vehicles are being rapidly developed as economical and low-pollution cars .The potential benefits of using LPG in diesel engines are both economical and environmental . In the dual fuel gas engines, the gaseous fuel is inducted along with the air, and this mixture of air and gas is compressed like in conventional diesel engines. A small amount of diesel, usually called the pilot, is sprayed near the end of the compression stroke to initiate the combustion of the inducted gas air mixture. With reduced energy consumption, the dual fuel engine shows a significant reduction in smoke density, oxides of nitrogen emission, and improved brake thermal efficiency. The combustion of this pilot diesel leads to flame propagation and combustion of the gaseous fuel. The engine can be run in the dual fuel mode without any major modification, but is usually associated with poor brake thermal efficiency and high HC & CO emissions at low loads .
The increase in pilot diesel improves the brake thermal efficiency at low loads. At higher loads, it reduces efficiency due to rapid combustion . Low efficiency and poor emissions at light loads can be improved significantly by advancing injection timing of the pilot fuel . Any measures that lower the effective lean flammability limit of charge and promote flame propagation will improve part load performance .
The gas concentration is low at lower loads, thus ignition delay period of pilot fuel increases, and some of the homogeneously dispersed gaseous fuel remains unburned which results in poor performance. A concentrated ignition source is needed for combustion of the inducted fuel at low loads . Poor combustion of the gaseous fuel at low loads results in higher emission of carbon monoxide and unburned hydrocarbons.
The hot surface assisted ignition concept is commonly applied to overcome the low temperature-starting problem in diesel engine. Introducing low cetane fuel such as alcohol and natural gas requires an extended application of the hot surface as continuous ignition assistance. The function of the hot surface is to provide favourable local ignition condition, followed by combustion propagating through the fuel air mixture to establish a stable diffusion flame.
The objective of the present work is to improve part load efficiency, which is the main drawback in dual fuel operation. In the present experimental work, the effect of introducing glow plug inside combustion chamber, which was not attempted earlier in the dual fuel operation, was studied. Pilot fuel quantity of 8.5 mg/cycle was introduced. It preheats the gas air mixture; and reduces the delay period of the pilot diesel. This results in improvement in the performance and in reduced emissions at low load.
2.3.1. Experimental Setup and Experimentation
A single cylinder, 3.7 kW, four strokes, direct injection, and air-cooled diesel engine coupled to an electrical dynamometer were used for the experiments. The specifications of the DI diesel engine are shown table-2
Specifications of the test engine (table-2)
| General detail
|| Single cylinder, four stroke,
compression ignition, constant speed,
vertical, air cooled, direct injection
| Compression ratio
| rated output
|| 3.7kw at 1500rpm
| rated speed
The engine was modified to work in the dual fuel mode by connecting LPG line to the intake manifold with a flame trap, non-return valve, needle valve, and mixing unit.
A digital type platform weighing machine having an accuracy of 2 mg was used to measure the LPG fuel flow by weight difference method with an uncertainty of 1.8 %.
A Kistler make piezo electric transducer with a sensitivity of 14.2 pC/bar was installed with a Kistler charge amplifier for monitoring the cylinder pressure. This was recorded in a personal computer. Using analog to digital converter, the average pressure was obtained from 100 consecutive cycles. Carbon monoxide and unburned hydrocarbons emissions were measured using a NDIR gas analyser with an uncertainty of 5%. Smoke emissions were measured by means of a Bosch smoke meter with an uncertainty of 6%. NOx emissions from the engine were measured using a Crypton make analyser with an uncertainty of 6%. Chromel – alumel (K – type) thermocouple was used to measure the exhaust gas temperature with an uncertainty of 0.5 º C. The brake thermal efficiency was calculated by considering the calorific value and mass flow rate of both fuels Brake thermal efficiency = brake power/ ((mf x CV )LPG + ( mf x CV )Diesel) (1) .The experimental procedure consists of the following steps:
• Initially, engine was tested using the base fuel diesel at all loads to determine the engine operating characteristics and pollutant emissions. The engine speed was maintained constant through out the entire engine operation at 1500 RPM.
• The same procedure was repeated in dual fuel mode with 8.5 mg/cycle pilot diesel, with and without glow plug .The glowplug was powered by12V battery, and it was maintained at a maximum temperature of 850º C throughout the engine operation. The pilot diesel quantity was maintained constantly for the entire load range by varying the flow rate of LPG for each load condition. The mass fraction of LPG in the blend (Z) is shown in Table 3.
Z = (m.LPG / (m.Diesel + m.LPG )) × 100 %
Table 3. Mass fraction of LPG in the blend
| Load in %
| DF with GP (Z)
| DF without GP (Z)
During the engine test conditions, the cylinder pressure, exhaust gas temperature, fuel consumption, exhaust smoke, and exhaust gas emissions were recorded at all the loads .
2.3.2. Results and Discussion
The results obtained in the dual fuel operation with and without the assistance of glow plug are compared to diesel; and are presented
126.96.36.199. Brake Thermal Efficiency
The variation of brake thermal efficiency against load . The glow plug assisted dual fuel mode of operation improves the efficiency by 2% up to 80% load, but there is no significant variation at full load operation. Brake thermal efficiency ranges from 12.9 % to 27.9 % with glow plug operation whereas in the case of dual fuel mode of operation without glow plug, it varies from 10.2 % to 28.3 %. This may due to the reduction in delay period of pilot diesel and an increase in the mixture temperature around the glow plug. The brake thermal efficiency for diesel varies from 13.7 % to 26.6 %.
188.8.131.52. HC and CO Emissions
The variation of hydrocarbon emission against load. The hydrocarbon emission is reduced throughout the engine operation in glow plug assisted dual fuel mode in comparison to dual fuel mode of operation. It ranges from 3.81 g/kW h to 1.33 g/kW h whereas in the case of dual fuel mode of operation without glow plug, itranges from12.6 g/kW h to 1.4 g/kW h, and for diesel from 0.78 g/kW h to 0.31 g/kW h.
Reduction in delay period of pilot diesel, increase in pre flame reaction near the injector due to glow plug temperature, and high temperature of gas air mixture around the glow plug are the reasons for lower emissions in the case of glow plug assisted dual fuel operation.
184.108.40.206 NOx emission
The variation of CO emissions against load is shown in Figure 4. The CO emission is reduced throughout the engine operation in the glow plug assisted dual fuel mode in comparison to dual fuel mode of operation. It ranges from 0.49 g/kW h to 0.13 g/kW h whereas in the case of dual fuel mode of operation without glow plug, it ranges from 0.99 g/kW h to 0.14 g/kW h. The reason for lower emission is the increased mixturetemperature by the glow plug temperature, which creates local turbulence and increase in flame velocity. The CO emission for diesel varies from 0.24 g The variation of NOx emission with load is shown in Figure 5. It increases marginally in the case of glow plug assisted dual fuel mode in comparison to dual fuel mode of operation. It ranges from 3.7 g/kW h to 3.1 g/kW h, whereas in the case of dual fuel mode of operation without glow plug, it varies from 3.28 g/kW h to 2.82 g/kWh, and for diesel from 7.77 g/kW h to 6.28 g/kW h. The primary fuel forms a homogeneous mixture, and it leads to complete combustion and rise in the peak pressure resulting in high temperature inside the engine during combustion, and it increases the possibility of NOx formation.
The variation of smoke emissions against load is shown in Figure 6. A marginal reduction in smoke emission throughout the engine operation can be noticed in the glow plug assisted dual fuel mode in comparison to dual fuel mode of operation without glow plug. It ranges from 0.2 to 0.92 BSU whereas in the case of dual fuel mode of operation without glow plug, it ranges from 0.2 to 1.2 BSU. The reduction of smoke may be due do lower carbon/hydrogen ratio of LPG. The smoke emission for diesel varies from 0.2 to 0.92 BSU
220.127.116.11 Exhaust Gas Temperature
The variation of exhaust gas temperature against load. A marginal increase in exhaust gas temperature is noticed throughout engine operation in the glow plug assisted dual fuel mode due to high combustion temperature. It ranges from 215oC to 535oC, whereas in the case of duel fuel operation without glow plug it varies from 201oC to 531oC. The diesel mode of operation shows a variation from 224oC to 571oC.2 to 0.92 BSU/kW h to 0.11 g/kW.
18.104.22.168 Combustion parameter
The cylinder pressure with crank angle for diesel, dual fuel mode, and glow plug assisted dual fuel mode at 20% of full load. The peak pressure in dual fuel mode without glow plug is 50 bars, and in glow plug assisted dual fuel mode it is 53 bars whereas in the case of diesel it is 61 bars. At low loads, pilot diesel initiates the combustion followed by LPG combustion due to high self-ignition temperature of LPG. It leads to a retardation in the peak pressure by 3° CA .The glow plug temperature reduces the delay period resulting in an increase in peak pressure. the cylinder pressure with crank angle at full load. The cylinder pressure obtained in dual fuel mode is less than the base diesel. The peak pressure obtained in the dual fuel mode of operation without glow plug is 62 bars, and in glow plug assisted dual fuel mode it is 64 bars whereas in diesel it is 68.7 bars. The peak pressure in the dual fuel mode is advanced by 2°CA when compared to diesel. It is due to pre combustion of LPG followed by diesel combustion.
22.214.171.124.2. Heat Release Rate
The rate of heat release curves are drawn using pressure and crank angle value in the existing software. The rate of heat release for glow plug assisted dual fuel mode, dual fuel mode, and diesel modeat 20% of full load. The combustion starts at the same crank angle of about 5o CA BTDC for both glow plug assisted dual fuel operation and diesel. But the combustion starts 5o CA after the glow plug assisted dual fuel operation in dual fuel operation without glow plug. The peak heat release rate of glow plug assisted dual fuel mode is 41 J /o CA, dual fuel mode is 34.9 J / o CA, and for diesel mode it is 52 J / o CA. Figure 11 shows the rate of heat release at full load. The peak heat release rate of glow plug assisted dual fuel mode is 59.7 J / o CA, dual fuel mode is 48.4 J / o CA, and for diesel mode it is 82.7 J / o CA. The combustion in glow plug assisted dual fuel operation starts 2o CA before diesel. The combustion may be initiated by the glow plug before the pilot injection of diesel in the glow plug assisted dual fuel operation
v A good engine needs high efficiency, high performance characteristics, low emission standards. It seems that the above mentioned solution meets all these specified standards. v For the practical implementation, changes in the design of Compression Ignition engines are not of a greater magnitude. The only change that has to be implemented is that the metering system should be able to meet 9:1 air fuel ratio. v Further cold starting is performed efficiently using glow plugs. It is very much essential to implement the dual fuel technique ASAP in order to save the ozone layer and to live in a green world. v Indian economy can be considerably saved because the fuel usage does not involve any foreign exchange. v The emission of smoke is reduced by 9% in the glow plug assisted dual fuel mode of operation compared to dual fuel mode of operation. Compared to diesel, it reduces by 69%. v The glow plug assisted dual fuel operation improves the combustion. It shows higher peak heat release rate, compared to dual fuel operation without glow plug. v The peak pressures are higher in glow plug assisted dual fuel operation in the entire load range when compared to dual fuel operation without glow plug. v In general glow plug assistance improves the part load performance in dual fuel engine with a significant reduction in emissions
Ø The performance and reliability of the dual fuel engines were comparable to the diesel engine. This conclusion may need to be reassessed after more prolonged CNG use and higher mileage accumulation. Ø When in dual-fuel mode, the dual fuel natural gas engines used approximately 86% CNG and 14% diesel. At an 86% CNG substitution rate, the dual fuel natural gas engines averaged about 4.8 miles/DEG, which is about 20% less than the diesel engine average of 6 miles/DEG. Ø Averaged during the entire demonstration period, the dual fuel natural gas engines operated about 57% of the time in dual fuel mode, and 43% of the time in diesel mode. The dual fuel natural gas engine engines averaged 5.34 miles/DEG overall, which is about 11% less than the diesel engine average of 6.0 miles/DEG. Ø When operating the dual fuel natural gas engine in diesel mode, the reduced-power-mode feature provided only minimal incentive for drivers to refuel with CNG. The dual fuel natural gas engines performed satisfactorily, even when fully loaded, in the reduced power mode. Ø The lower-than-expected CNG substitution rate was the result of: Occasional failure of the vehicle operator to fuel the buses with CNG. Problems with the dual fuel natural gas engine computer operating software. Breakdowns of the CNG refueling station.
Ø The dual fuel natural gas-engine-equipped buses cost about $0.20/mile more to operate than the diesel-engine-equipped bus.
Ø Overall, the dual fuel natural gas engine operating in the dual-fuel mode had lower NOx, CO2, and PM emissions and higher CO and NMHC emissions than the diesel engine.
Ø The dual fuel natural gas engine had higher NOx and NMHC emissions (combined) than the diesel for the both the EPA UDDC and WVU CBD drive cycles. The dual fuel natural gas engine had lower NOx and NMHC emissions (combined) than the diesel engine for the 55 MPH Steady State drive cycle.
Ø The dual fuel natural gas engine demonstrated a greater percentage reduction in NOx emissions than the diesel engine in the 55 MPH Steady State drive cycle than in both the EPA UDDC and WVU CBD drive cycles. This may be due to the dual fuel natural gas engine having relatively lower NOx emissions, or to the diesel engine having relatively higher NOx emissions (as would be expected if the diesel engine computer was equipped with a defeat device), when operated in the steady-state mode.
Ø When operated in the diesel mode, the dual fuel natural gas engine had lower PM and NMHC emissions than the disel engine. Emissions of NOx, CO2, and CO from the dual fuel natural gas and diesel engine were similar when the engines were operated on diesel.
Ø brake thermal efficiency at low loads compared to dual fuel mode of operation The glow plug assisted dual fuel mode shows an improvement of 3% in, with no appreciable change at high loads.
Ø HC and CO emissions are reduced by 69% and 50% in the glow plug assisted dual fuel mode of operation compared to dual fuel mode of operation without glow plug, but marginally higher than in diesel.
Ø B. Stanislav, “The development of gas (CNG, LPG and H2) engines for buses and trucks and their emission and cycle variability characteristics”. SAE Transactions, 2001-01-0144, 2001.
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Ø D.T. Hountalas, R.G. Papagiannakis, “Development of a simulation model for direct injuction dual fuel Diesel-natural gas engine”. SAE Transactions, 2000-01-0286, 2000.
Ø R.G. Papagiannakis, D.T. Hountalas, “Experimental investigation concerning the effect of natural gas percentage on performance and emissions of a DI dual fuel Diesel engine”. Applied Thermal Engineering, Vol. 23, No. 3, 2003, 353-365. 310330350370390410CRANK ANGLE, DEG-101030507090RATE OF HEAT RELEASE,J/DEG CADiesel8.5mg/cycle Pilot +LPG8.5mg/cycle Pilot +LPG with Glow Plug
Ø C.V. Sudhir, H. Vijay, S. Desai, Y. Kumar, P. Mohanan, “Performance and emission studies on the injection timing and diesel replacement on a 4-S LPG-Diesel-fuel engine ”. SAE Transactions, 2003-01-3087, 2003.
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Ø M.P. Poonia, “Experimental investigation of the factors affecting the performance of a LPG-Diesel dual fuel mode”. SAE Transactions, 1999-01-1123, 1999.
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