Hydrogen Technology in Dual Combustion IC Engines

Transcription

1 Hydrogen Technology in Dual Combustion IC Engines Kavin Raja G 1, Karthik R 2, Santosh N 3 1,2&3 Student, B.E Mechanical Engineering, Sri Krishna College of Engineering and Technology, Tamil Nadu, India. Abstract In this paper, research on advanced engine technology is discussed. This concept of engine uses two different fuels at the same time to extract maximum work from the engine. In this concept we are implementing the idea of using hydrogen as the first fuel in addition to secondary conventional fuels like gasoline and diesel. The objective of this project is to provide a means for using hydrogen in internal combustion engines. In this concept, cylinder of the engine has two thermodynamic systems which works on Otto Cycle or Diesel Cycle and are separated by the moving boundary which is the piston. The four strokes of the Otto Cycle or Diesel Cycle works alternatively in the two systems. The two chambers of the cylinder have their own intake, exhaust and fuel injection systems. The hydrogen is injected by high pressure direct injection and is ignited by compression ignition and direct injection in turn will eliminate premature ignition of hydrogen. The strokes in the lower chamber can be initiated by just supplying heat energy to the cylinder block which is sufficient to ignite the hydrogen. The high diffusivity of hydrogen further increases the safety in case of a leak. This concept of the engine can also run using one fuel in case of absence of the other since both the systems work independently. This engine can provide only reciprocating motion as output and it must be converted to rotary motion by suitable mechanisms. In today s world of depleting resources hydrogen seems to be a promising fuel and because of its low emissions, it could be the most ideal one to be used. Keywords Hydrogen Engine, Renewable Energy Sources, Eco friendly Engine Dual Combustion Engine, Hydrogen IC Engine. TABLE 1 FUEL RESERVES Fuel Reserves Years left Oil 1,386 billion barrels 46.2 Gas trillion cubic metres 58.6 Coal 860,938 million tonnes 118 Source: BP. Reserves calculated at current price using current technologies Use of hydrogen in normal IC engines would not produce sufficient amount of power as desired. On the other hand, the conventional IC engines that runs on gasoline or diesel has low efficiencies. Using the concept explained in this paper, more power can be generated by the conventional fuels and the efficiency is improved by hydrogen. Hydrogen is a cleanest form of fuel that is available today. When hydrogen undergoes combustion process with pure air, it results in the formation of water as the by-product. Hydrogen is available in nature in the form of water. Water which is available in abundance forms a surplus source for hydrogen. Since the fossil fuels are depleting at a faster rate, hydrogen which is available in abundance proves to be the fuel of tomorrow. I. INTRODUCTION Today, the energy resources that we use mostly are non-renewable and are depleting at a very faster rate. So, why not use the available energy in a wise manner giving Mother Nature enough time to regenerate fossil fuels? This idea of engine design extracts the maximum energy from the engine. But, according to the below given data, the current energy resources may not be available to us for a long time. One of the alternative fuels that are readily available for use in automobiles is hydrogen. So, the use of hydrogen which is a renewable energy resource in this concept of engine design has been proposed. There are two ways of using hydrogen in automobiles: i) In internal combustion engines, ii) In hydrogen fuel cell vehicles. The fuel cell technology is currently in research progress while the use of hydrogen in internal combustion engines could be processed quickly. II. BODY Our concept of the engine design has two combustion chambers in a single cylinder such that the cylinder is completely enclosed at the bottom and can only give a reciprocating motion as output. Hence there form two thermodynamic systems with piston as a common moving boundary between them. The rod which reciprocates takes the reciprocatory motion as the output from the engine and is converted into rotary motion by suitable mechanisms. Both the upper and the lower chamber have their own intake, exhaust and ignition systems. ISSN: Page 177

2 TABLE 2 COMPARISON OF DIFFERENT VEHICLE TYPES Engine Type Gasoline ICE Sparkignition Gasoline Hybrid Spark-ignition & electric motor H 2 ICE H 2 Fuel Cell Fuel cell & CI (with electric electric motor) motor Average engine efficiency ~30% ~30% ~40% ~55% Max engine efficiency 32.5% 32.5% ~40% ~65% Transmission Type Standard CVT/hybrid CVT/likely hybrid CVT/likely hybrid Transmission efficiency ~40% ~60% ~60% ~60% Fig 1. Cross-section view of two-chambered engine The primary fuel in this concept is hydrogen, which is used at the lower chamber of the cylinder and the secondary fuel can be any conventional fuels like petrol and diesel. Hydrogen can be ignited by both spark ignition and compression ignition. The strokes of the engine are designed in such a way that compression and expansion of the systems takes place alternatively. The piston is made of suitable alloy such that it withstands the temperatures produced on both the chambers. The engine can produce two power strokes in a single cycle and use of hydrogen improves the efficiency of the engine. Thus it overcomes the disadvantages of gasoline engine which has less efficiency and hydrogen internal combustion engines which has less power output. A. Why Use Hydrogen in IC Engines Hydrogen can burn in a lean mixture, but the power produced by the combustion process depends on the amount of hydrogen that is fed in the combustion process. The wide range of flammability of hydrogen can be used to produce different amount of powers. Hydrogen can ignite at very low temperatures, so the heat of the piston and the cylinder due to the previous combustion reactions is sufficient to ignite the hydrogen and to start the cycles [2][3]. Fuel economy (mpg equivalent) Sizeability As much power as needed, at the cost of mpg Efficiency improvements over gas ICEs are mostly lost with increased power Efficiency losses or higher emission control costs to increase power Fuel Tank Size(constant Moderate Small Large range) Cost of Fuel Currently low Criteria Pollutant Emissions Meets emission standards Currently low Lower than gasoline ICE Developed and State of technology Developed in diffusion stage Currently high: but may be slightly lower than FCVs Likely low, some NO x Could be developed quickly Increasing power may be expensive, requiring additional FCs Large: smaller than H 2 ICE Currently high Very low or none Earlier in the research process B. Piston Design The piston is made of a suitable alloy such that it can withstand the high temperatures produced in both the chambers. The piston used in this concept is a solid piston. Due to high temperatures that are generated on both the chambers, the piston must be cooled by circulating suitable coolant by means of holes inside the piston. To completely seal off both the chambers, apart from the piston rings that are generally available, a special type of ring which is designed in a suitable shape so that it collects the fuels and oils that get leaked from the upper chamber and it is drained by means of drain hole provided in the reciprocating rod. The draining is vacuum assisted for easier drain. In such a way ISSN: Page 178

3 the two systems or the chambers are completely sealed off so that they don t interfere with each other s reaction. In this case the absence of one fuel does not affect the functioning of the engine and the engine can run using only one fuel. It acts like normal petrol or a hydrogen engine in the previous case. C. Stroke Sequence We have made the corresponding changes in the strokes of the engine to get the maximum efficiency: 1. The compression ratio of hydrogen is higher than that of petrol, so the strokes are altered in such a way that the power produced in the upper chamber running on petrol aids in compressing the air in the lower chamber that must undergo combustion reaction with hydrogen. 2. Similarly, in case of diesel as the secondary fuel the inverse situation is applied since the compression ratio in a diesel engine is higher than that of hydrogen engine. 3. Let us consider the case of petrol hydrogen engine, the stroke takes place in continuous operation as given in the following sequence below: TABLE 3 WORKING STROKES 2. Compression takes place in the petrol chamber and the piston goes up. As the piston moves up, a partial vacuum is created in the lower chamber and thus intake of air takes place in the lower chamber. 3. The compressed air fuel mixture in the upper chamber gets ignited by the spark plug and power is produced in the upper chamber. The piston is forced down by combustion of petrol and the air in the lower chamber gets compressed. 4. Hydrogen at high pressure is injected into the lower chamber and due to change in pressure, the hydrogen gets ignited and power is produced due to which the piston moves up and pushes the exhaust gases through the outlet in the upper chamber. The cycle continues and thus two power strokes are produced in single cycle. E. Calculation We have considered the Honda CBR 250R engine and the values for the Petrol chamber are taken from it. TABLE 4 PERFORMANCE PARAMETERS OF TWO CHAMBERS Characteristics Hydrogen Petrol PETROL CHAMBER Intake Compression Power Exhaust HYDROGEN CHAMBER Exhaust Intake Compression Power Compression Ratio 12:1 10.7:1 rpm Nm 23 Nm 8000 rpm HP 25 HP Efficiency 40.32% 30% The above table can be made for a diesel hydrogen engine also; but the sequence will be in the opposite way. D. Working Let us consider petrol as the conventional fuel in the upper chamber and hydrogen in the lower. The working is as follows: 1. Intake takes place in the upper chamber and the air fuel mixture from the carburettor flows into the cylinder thus lowering the piston. Simultaneously in the lower chamber the exhaust gases from the previous combustion reaction of hydrogen goes out through the exhaust valve. Hydrogen has a variety of compression ratios and varying this ratio can result in improvement of efficiency. Hence the combination of both petrol and hydrogen will increase the power and efficiency of the vehicle. F. Cam The engine is equipped with variable valve timing mechanism by using electronic cam. This mechanism has different cam profiles to adopt for different conditions of the engine. In variable valve timing, the valve operation is shifted to a different cam profile according to the engine running conditions. The electronic cam table is determined such that suitable amount of air fuel mixture is fed in correct proportions to both the chambers so power produced in both sides of the piston is almost equal [5]. ISSN: Page 179

4 limited to 17:1, and this temperature was used in the experiments reported in this paper[3][4]. G. Valve Operation The valve operation sequences for both the chambers are given below. J. Auto- Ignition of Hydrogen Jet TABLE 5 VALVE OPERATION SEQUENCES PETROL Inlet Valve Open Inlet Valve Close Exhaust Valve Open Exhaust Valve Close HYDROGEN Exhaust Valve Close Inlet Valve Open Inlet Valve Close Exhaust Valve Open H. Hydrogen Injection Hydrogen is injected by means of constant volume injection which is a direct injection method. From the following figure, it could be seen that hydrogen injected by direct means at high pressure improves the thermal efficiency of the engine [1]. Fig 2. Comparison of Injection methods I. Inlet Air Heating System Due to the high self-ignition temperature of hydro- gen, heating of the inlet air may be necessary to en- sure fuel auto ignition. A 3.5kW electric inlet air heating system, capable of raising the inlet air temperature to 120 degree Celsius, was implemented in the intake system, and the air inlet temperature was controlled using a PID controller. The air heating control system ensures that the correct compression temperature for fuel auto ignition is reached, and allows investigations into the influence of this operational variable on the engine performance. The minimum air inlet temperature was found to be 80 degree Celsius, since this particular engine compression ratio was Fig 3.Ignition delay as a function of temperature The figure illustrates the strong dependence of the cylinder charge temperature on the auto ignition delay of the hydrogen jets. It can be seen that for temperatures below approximately 1100K, the auto ignition delay increases rapidly and becomes significantly longer than for higher temperatures. The auto ignition delay is strongly dependent on the ambient gas temperature, and the temperature de- pendency follows an Arrhenius function. It was found that for temperatures below 1100K, the auto ignition delay is longer than that of conventional diesel fuels, but much shorter delays can be obtained if the cylinder charge temperature is close to or above 1100K. The figure explains the need for inlet air heating in the hydrogenfuelled engine in order to achieve acceptable ignition delays. For conventional diesel fuels, the ignition delay curve would be shifted to the left due to the lower self-ignition temperatures, and acceptable ignition delay values can be achieved with lower end-of-compression charge temperatures. K. Engine Options There is wide range of engines available by classifying the engines according to the ignition systems that are used in the two chambers. The fuels in both the chambers are compression ignited or the upper chamber can be compression ignited and the lower can be spark ignited in case of using diesel as the secondary fuel. When petrol is used as the secondary fuel, both the chambers can be spark ignited or the upper chamber can be spark ignited and the lower chamber can be compression ignited. Thus we have four options of engine based on the ignition systems. ISSN: Page 180

5 L. Engine Performance There are several possibilities to improve the performance of an automobile internal combustion engine. One is to increase the capacity of the engine. The capacity of the engine can be increased in a single cylinder or the engine can be made to have several cylinders. A single large cylinder may be a more convenient choice due to fewer parts to manufacture and maintain, but the advantages are over-weighed by the disadvantages. This concept of engine introduces a new possibility to increase the performance of an engine without increasing its capacity. The range of power that can be produced in an engine with all the fixed parameters is higher than in free piston engine. The performance parameters of the two chambers add up and it provides increased power and torque. It also provides good overall efficiency theoretically. diesel-fuelled mode. Figure 4 shows the measured NOx emissions with varying engine load for the engine running in hydrogen-fuelled and conventional diesel mode. As expected, the nitrogen oxides formation is low at low loads, for which the cylinder charge is lean and in-cylinder temperatures are lower, but increases sharply with increasing load. TABLE 6 EXPERIMENTAL RESULTS FOR ENGINE ENERGY BALANCE Fig 4.Variation of NOx concentration with Indicated Mean Effective Pressure Table 6 shows the engine efficiency results in different operating modes. Engine efficiency is significantly high in hydrogen direct injection (DI) mode, with the engine achieving a brake efficiency of 42.8%, compared with 27.9% when using diesel fuel. This is mainly due to lower losses to the cooling system, which constitute engine frictional losses and heat transfer losses, mainly to the combustion chamber walls. The frictional losses are not heavily influenced by the choice of fuel, but the increased engine power makes the relative influence of the mechanical losses lower in hydrogen-fuelled mode. Reduced in-cylinder heat transfer losses are expected in the hydrogen-fuelled engine due to the properties of the gaseous fuel, leading to enhanced fuel-air mixing, thereby reducing peak gas temperatures, and the lower inertia of the fuel, reducing the problems associated with spray-wall impingement. The data in the table are for operation on 20% diesel fuel and 80% hydrogen (on an energy basis). The improved performance when using dual fuels and HCCI compared to conventional diesel engine mode can be seen [4]. M. Reduction in Emission The nitrogen oxides emissions from a direct injection hydrogen engine are expected to be lower than those of the engine in conventional, A clear NOx emissions advantage for the hydrogen-fuelled engine can be seen over the full load range, with the NOx levels being approximately 20% lower than those obtained under diesel-fuelled operation. Although the peak gas pressures are higher in hydrogen-fuelled mode due to the higher fuel burn rate, this is seen not to have an adverse effect on NOx formation. This suggests that the peak gas temperatures are lower in hydrogen-fuelled mode due to enhanced fuel-air mixing and more homogeneous conditions within the combustion chamber. Hightemperature zones, such as those occurring in the outer regions of the fuel spray in conventional diesel operation are reduced [4]. III. CONCLUSION This concept brings about a new dimension in automotive technology and with research on fuel cells still in progress; this idea seems to be a very efficient way of utilising the resources that are available. It also provides better power to weight ratio, lesser emissions and better efficiency than the conventional IC engines. Thus this concept proves to be a better solution for a greener tomorrow. ACKNOWLEDGMENT We have presented this paper "Concept of Hydrogen Technology in Dual Combustion Engines" in various reputed institutions such as IITs (Indian Institute of Technology) and NITs ISSN: Page 181

6 (National Institute of Technology). In these competitions we were evaluated by technical experts in this field of engineering. They gave us positive reviews and also provided us with some valuable inputs. We would like to thank them whole heartedly for these inputs as it played a vital role in the development of this concept. We had presented this research paper in a student convention in front of a panel of research experts. Our novel concept of engine technology received humongous applause from them. We got the 1st place in the event and the KNIMBUS YOUNG INNOVATOR AWARD for the year In addition, we were also sanctioned an prize amount of Rs in Indian money. We have now started the prototyping of this project. It is with great pleasure I acknowledge the KNIMBUS organization for their enthusiastic support and motivation. REFERENCES [1] - U.S. Department of Energy web site for information on energy efficiency and renewable energy technologies. [2] Peter Van Blarigan, Advanced Internal Combustion Engine Research, Sandia National Laboratories, Livermore, California. [3] Kenneth Gillingham, Hydrogen Internal Combustion Engine Vehicles: A Prudent Intermediate Step or a Step in the Wrong Direction? Stanford University. [4] J.M. Gomes Antunes, R. Mikalsen, A.P. Roskilly, An experimental study of a direct injection compression ignition hydrogen engine, Sir Joseph Swan Institute for Energy Research, Newcastle University, Newcastle upon Tyne, NE1 7RU, England, UK. [5] Mrdjan Jankovic and Stephen W. Magner, Variable cam timing Consequences to automotive engine control design, Ford Research Laboratory. ISSN: Page 182