Transient State Fuel Injection - A New Concept with Different Fuel Combinations

Transcription

1 Transient State Fuel Injection - A New Concept with Different Fuel Combinations Wing Commander M. Sekaran* Professor, Department of Aeronautical Engineering, Vel Tech Dr RR & Dr SR Technical University, Avadi, Chennai 662, India. Dr.S.Mohanamurugan M.E.,Ph.D Professor, Department of Mechanical Engineering, Velammal Engineering College, Ambattur, Chennai India. *Phone: , sekaran.muthu@gmail.com Abstract- Homogenous charge compression ignition (HCCI) is a clean and efficient combustion process In this experiment we analyze the performance and emission characteristics of HCCI engine operating in premixed charge compression ignition (PCCI) mode assisted with a secondary pilot injector as combustion initiator located at the inlet manifold. Experiments were conducted in a modified single cylinder water-cooled diesel engine, employing our conceptual system known as transient state fuel induction. Here we use diesel, petrol and bio-diesel (jatropha) as the fuels at different mixing ratios. The engine wear and tear and emissions have also been found decreasing with the use of bio-diesel when compared to vegetable oil. Variable valve actuation (VVA) has been proven to extend the HCCI operating region by giving finer control over the temperaturepressure-time history within the combustion chamber. HCCI has advantages in high thermal efficiency and low emissions and possibly become a promising combustion method in internal combustion engines. The observations had proved to have increase in brake thermal efficiency with reduced emissions. This research is being conducted both in university and also as a real time experiment in the Southern agro engine private limited, Chennai. Keywords- homogeneous charge compression ignition (HCCI), pilot injection, premixed charge compression ignition (PCCI) I. INTRODUCTION To minimize the magnitude of deviation from the ideal cycle and to comply with future emission norms the best features of SI (Spark Ignition) and CI (Compression Ignition) engines combustion can be coupled to obtain a lean burning hybrid combustion mode known as homogenous charge compression ignition in which the combustion takes place spontaneously and homogenously. It is a form of combustion process which capitalizes upon the advantages of higher compression ratio, lean homogenous air fuel mixture, lower combustion temperature and instantaneous combustion to achieve. II. VARIABLE COMPRESSION RATIO There are several methods of modulating both the geometric and effective compression ratio. The geometric compression ratio can be changed with a movable plunger at the top of the cylinder head. This is the system used in "diesel" model aircraft engines. The effective compression ratio can be reduced from the geometric ratio by closing the intake valve either very late or very early with some form The First International Conference on Interdisciplinary Research and Development, 31 May - 1 June 211, Thailand 46.1

2 Wing Commander M. Sekaran and Dr. S.Mohanamurugan of variable valve actuation (i.e. variable valve timing permitting Miller cycle). III. VARIABLE INDUCTION TEMPERATURE This technique is also known as fast thermal management. It is accomplished by rapidly varying the cycle to cycle intake charge temperature. It is also expensive to implement and has limited bandwidth associated with actuator energy. employed in direct injection diesel engine the in-cylinder swirl and squish motion of the air enhances the mixture formation. The heat energy required to heat the fuel and air can be obtained from the exhaust and the cooling water which are wasted. The advantages of having vapor state fuel induction are air and vapor mixing results in homogeneous mixture. Hence the misdistribution of the air fuel mixture is eliminated resulting in shorter combustion duration. IV. TRANSIENT STATE FUEL INDUCTION It is known that obtaining homogenous charge with uniform air fuel ratio is crucial to control the combustion; this system aims to obtain homogenous charge by inducting the fuel in a transient state. Since only air and vapor can form perfect homogenous mixture, in this system the fuel is injected in to the manifold at a temperature close to the flash point of the fuel being used in a stream of heated air being inducted the fuel instantly vaporizes and produces a homogenous charge. Given that the system is V. EXPERIMENTAL SETUP The engine used for the testing purpose is a single cylinder DI (Direct Injection) engine (Agricultural type, water cooled) which is fitted to a brake drum dynamometer. The engine specifications are, it is a Water-cooled, Vertical, 4 stroke cycle, direct injection, naturally aspirated. Gravity feed fuel system with efficient Paper element filter, Force Feed Lubrication to main and large end bearings and camshaft bush, Suitable for run- through or Thermo syphon cooling. The Engine specifications are tabulated below. Number of cylinder One Bore x Stroke 8 x 11 mm Cubic Capacity.553 lit Compression Ratio 16.5 : 1 Rated Output as per BS5514/ISO 346/IS kw (5. hp) at 15 rpm. SFC at rated hp/15 rpm 245 g/kwh(18 g/bhp-hr) Lube Oil Consumption 1.% of SFC max. Lube Oil Sump Capacity 3.3 lit. Fuel Tank Capacity 6.5 lit Fuel Tank re-filling time period Every 6 hours engine running at rated output Engine Weight(dry) w/o flywheel 114 kg Weight of flywheel 33kg - Standard Rotation while looking at the flywheel Clockwise. Optional - Anticlockwise Power Take-off Flywheel end. Optional-Gear end half or full speed Starting Hand start with cranking handle. Special Issue of the International Journal of the Computer, the Internet and Management, Vol. 19 No. SP1, June,

3 Transient State Fuel Injection - A New Concept with Different Fuel Combinations VI. VARIABLE EXHAUST GAS RECIRCULATION (VEGR) Exhaust gas can be very hot if retained or reinducted from the previous combustion cycle or cool if re-circulated through the intake as in conventional Exhaust Gas Recirculation (EGR) systems. The exhaust has dual effects on HCCI combustion. It dilutes the fresh charge, delaying ignition and reducing the chemical energy and engine work. Hot combustion products conversely will increase the temperature of the gases in the cylinder and advance ignition. SPECIFICATION OF VEGR: MRU DELTA 16L MEASURING RANGES: Oxygen (O 2 ) : 25.% vol Carbon monoxide (CO) : 15.% Carbon dioxide (CO 2 ) : 2.% Hydro carbon (HC) n-hexane Nitrogen monoxide (NO) : - 2 ppm : 2 ppm Excess Air calculated according to Brett Schneider Temperature Rounds per minute Response time Mains supply 12 V DC : `c : 4 1U/min t95: 15s : V 5/6Hz or VII. WORKING PRINCIPLE The fuel is heated by means of a 1watts water bath provided with an electrical thermostat which enabled us to maintain the fuel at the desired temperature. The maximum fuel temperature that can be achieved using our set up is 75 deg c. In case of diesel we maintained the temperature at 55 deg c, and in case of bio-diesel we maintained the temperature at 75 deg c. The air is heated by means of 8watts air heater placed in inlet manifold. The air temperature is maintained by means of an electrical thermostat to a maximum of about 8 deg c. The temperature history of the hottest (and close to adiabatic) portion of the core of the experiment is reproduced by the hottest zone. This part of the charge should the first ignition site. The fuel is injected in to manifold using an electronic fuel pump through a secondary fuel injector mounted on the inlet manifold whose spray angle is 3 deg c, the fuel line pressure is maintained at 6 bars. The current rating of the fuel injection pump that we have used is 2 ampere and that of the fuel injector is.3 ampere. The injection is controlled by electronic circuit having a limit switch with frequency of about 75 cycles per minute. The limit switch is actuated by means of a bolt attached to the inlet valve rocker; we effectively have utilized the 8mm travel of the rocker arm for generating the electrical signal for initiating the injection during the suction stroke. In its original form the HCCI uses a premixed air fuel mixture. This may be achieved through a port fuel injection. In place this; very early direct injection has also been used. Early direct injection in the combustion chamber, during the intake stroke or early part of the compression stroke, allows better fuel air mixing than a standard diesel combustion scenario. Direct injection also allows stratification of the in cylinder charge, and this offers means to realize stable and efficient combustion during transition from higher to lower engine load. It has been shown that for pure HCCI conditions were a completely pre mixed charge is used, fuel chemistry and gas mixture, temperature are the 2 major facts that determine the auto ignition process. Mixing and turbulence have a much lesser impact on the auto ignition. However, for HCCI like conditions like as direct injection, where a non homogeneous charge may be formed. The amount and rate of fuel air mixing may impact the ignition delay and start of combustion. The First International Conference on Interdisciplinary Research and Development, 31 May - 1 June 211, Thailand 46.3

4 Wing Commander M. Sekaran and Dr. S.Mohanamurugan The impact of the initial (i.e. at the end of the fuel injection or start of ignition dwell) temperature and fuel air distribution on ignition dwell was investigated. Various methods to prolong the ignition dwell were used, that inclined- variations in injection timing, EGR percentage, engine valve actuation and swirl ratio. Various parameters including temperature and equivalence ratio, distribution, fuel vaporization, intermediate radical formation and turbulent time scale were measured to check if mixing and distribution had been affected by the above methods. Variable injection timings were compared in terms of their effects on air/fuel ratio, since the injection timing has little effect on the mixing of the fresh charge and diluted charge. The results found that there was more of a uniform air/fuel ratio in the cases of the start of injection at the end of exhaust valve closing and the intake valve opening at the end of compression. In relation to the HCCI engine is combustion phase control. Hot residual gas supplies heat to the combustion chamber and promotes HCCI combustion [1-4]. This hot residual gas can be controlled by a variable valve timing (VVT) device [5]. More over, the VVT device can improve volumetric efficiency by varying the intake valve s open and close timing [6]. In HCCI, however, the entire fuel/air mixture ignites and burns nearly simultaneously resulting in high peak pressures and high energy release rates. To withstand the higher pressures, the engine has to be structurally stronger and therefore heavier. Two different blends of fuels are used, that will ignite at different times, resulting in lower combustion speed. The problem with this is the requirement to set up an infrastructure to supply the blended fuel. Alternatively, dilution, for example with exhaust, reduces the pressure and combustion rate at the cost of work production. Since HCCI operates on lean mixtures, the peak temperatures are lower in comparison to spark ignition and diesel engines. The low peak temperatures prevent the formation of NOx. However they also lead to incomplete burning of fuel especially near the walls of the combustion chamber. This leads to high carbon monoxide and hydrocarbon emissions. An oxidizing catalyst would be effective at removing the regulated species since the exhaust is still oxygen rich In HCCI, the entire reactant mixture ignites (nearly) simultaneously. Since there are very little or no pressure differences between the different regions of the gas, here is no shock wave propagation and hence no knocking. However at high loads (i.e. high fuel/air ratios), knocking is a possibility even in HCCI. HCCI is otherwise classified as controlled auto ignition hence during high load operation it becomes extremely hard to obtain simultaneous auto ignition in controlled fashion. This in turn increases the probability of knocking due to the sharp rise of pressure. VIII. INJECTION TIMING Circumference of the flywheel: 126.5cm Radius of the flywheel : 2.13cm The suction stroke duration is for 219 deg The exhaust stroke duration is for 219 deg The inlet valve opens 4.5deg before TDC during exhaust stroke The inlet valve closes 34.5 deg after BDC during compression stroke The exhaust valve opens 34.5deg after BDC during expansion stroke The exhaust valve closes 4.5deg after TDC during exhaust stroke The manifold injection starts deg after TDC during the suction stroke The manifold injection closes deg before BDC during the suction stroke The injection duration is for deg during suction stroke, for about 2/5 of the suction stroke. Special Issue of the International Journal of the Computer, the Internet and Management, Vol. 19 No. SP1, June,

5 Transient State Fuel Injection - A New Concept with Different Fuel Combinations The injection rate is maintained at 7.2ml/min during the injection duration IX. RESULTS AND DISCUSSION This experiment is conducted with different fuels at different mixing ratios at the primary and secondary injectors; the order of fuel injection is as follows, 1. Diesel Diesel PCCI-DI 2. Diesel Bio-diesel PCCI-DI mode combustion The below graphs shows the characteristics of increased performance and reduced pollution. 9.1 CHARACTERISITICS OF BRAKE THERMAL EFFICIENCY The increase in the brake thermal efficiency is attributed to above mentioned reason in total fuel consumption and specific fuel consumption which makes the combustion more effective. % LOAD VS BThe, IThe Bthe1 Bthe2 Ithe1 Ithe2 Fig. 2 Effects of BThe, IThe in diesel diesel PCCI-DI 6 LOAD VS BThe, IThe 9.2 CHARACTERISITICS OF HC, NO The increase in the hydro carbon (HC) emission is due to the inability of the injection system used to inject the fuel in to the inlet manifold, to vary the fuel quantity in no load and part load operation, reduction in the oxygen concentration due to increase in the air temperature and due to the fact that the quantity of fuel injected as pilot injection does not have sufficient quantity of oxygen to react because the combustion chamber is occupied by the premixed charge in which the oxygen concentration is relatively less. In bio-diesel the reduction in the hydro carbon emission is to effective utilization of the oxygen available in it by PCCI-DI mode combustion process. The emissions characteristics are measured both in the university research lab and also in the real time market at Southern agro engine private limited, Chennai. ppm LOAD VS HC,NO HC 1 HC 2 NO 1 NO 2 Fig. 4 Effects of HC, NO in diesel diesel PCCI-DI 6 LOAD VS HC, NO % Bthe 1 Bthe2 Ithe 1 Ithe 2 ppm HC1 HC 2 NO 1 NO 2 Fig. 3 Effects of BThe, IThe in diesel diesel PCCI-DI Fig. 5 Effects of HC, NO in diesel bio diesel PCCI-DI mode The First International Conference on Interdisciplinary Research and Development, 31 May - 1 June 211, Thailand 46.5

6 Wing Commander M. Sekaran and Dr. S.Mohanamurugan 9.3 CHARACTERISITICS OF CO, CO2 The increase in the percentage of the oxygen available with the fuel does not have any considerable effect. ppm LOAD VS HC, NO Fig. 6 Effects of CO,CO2 in diesel diesel PCCI-DI % LOAD VS CO,CO HC1 HC 2 NO 1 NO 2 Fig. 7 Effects of CO, CO2 in diesel bio diesel PCCI- DI CONCLUSION CO 1 CO 2 CO2 1 CO2 2 Homogenous charge compression ignition (HCCI) has advantages in high thermal efficiency and low emissions and possibly become a promising combustion method in internal combustion engines. Recent researches have show the HCCI engine fueled with high octane number (ON) fuel has more advantages in fuel economy than that of low-octane fuel [8-14]. For the HCCI combustion with low-octane fuel, like diesel, ignition occurs in two stages (low-temperature heat release and hightemperature hear release). Therefore, ignition timing and combustion phase are difficult to optimize. Moreover, the lowtemperature here release begins at a temperature of about 8K. This ignition temperature limits the compression ratio to 13:1 and the efficiency to less than a conventional diesel engine. Generally, Diesel HCCI engine only has advantage in NOx and PM emission, but lower thermal efficiency than conventional diesel engine. In contrast, the high-octane fuel allows compression to higher temperatures with ignition occurring in a single stage at above 1K. This temperature permits higher compression ratios, which lead to higher efficiencies. HCCI engine tests have shown that using high-octane fuel, such as isooctane or gasoline, and diesel-like compression ratios, HCCI engines can achieve diesel-like efficiencies and low NO emissions [15] with stable ignition timing. The other fuel apart from diesel and petrol we used bio-diesel which gives tremendous results when injected in secondary injection before diesel. Based on the above mentioned results we conclude that HCCI process achieved by us in PCCI-DI mode has effectively increased the brake thermal efficiency and reduced pollution to a great extent. APPENDIX 1. TFC 1- Total fuel consumption in conventional, kg/kwh 2. TFC 2- Total fuel consumption in PCCI-DI mode combustion, kg/kwh 3. TFC 3- Total fuel consumption of the fuel injected in to the inlet manifold in PCCI-DI mode combustion, kg/kwh 4. SFC 1- Specific fuel consumption in conventional, kg/kwh 5. SFC 2- Specific fuel consumption in PCCI-DI, kg/kwh 6. SFC 3- Specific fuel consumption of the fuel injected in to the inlet manifold in PCCI-DI mode combustion, kg/kwh 7. IThe 1-Indicated thermal efficiency of conventional,% 8. IThe 2- Indicated thermal efficiency of PCCI-DI, % Special Issue of the International Journal of the Computer, the Internet and Management, Vol. 19 No. SP1, June,

7 Transient State Fuel Injection - A New Concept with Different Fuel Combinations 9. BThe 1-Brake thermal efficiency of conventional, % 1. BThe 2-Brake thermal efficiency of PCCI-DI, % 11. HC 1-Hydro carbon emission from conventional, ppm 12. HC 2-Hydro carbon emission from PCCI-DI, ppm 13. NO 1-Oxides of nitrogen emission from conventional, ppm 14. NO 2-Oxides of nitrogen emission from conventional, ppm 15. CO 1-Carbon mono oxide emission from conventional, % 16. CO 2-Carbon mono oxide emission from conventional, % 17. CO2 1-Carbon mono oxide emission from conventional,% 18. CO2 2-Carbon mono oxide emission from conventional, % 19. SI 1-Smoke intensity for conventional mode combustion, mg/m^3 2. SI 2- Smoke intensity for PCCI-DI mode combustion, mg/m^3 21. Ex Te 1-Exhaust temperature for conventional, degº c 22. Ex Te 2- Exhaust temperature for PCCI-DI mode combustion, deg c REFERENCES [1] Allen J, Law D. (22). Varibale valve actuated controlled auto-ignition: speed load maps and strategice regimes of operation. [SAE ]. [2] Wolters P, Salber W, Geiger J, Duwsmann M, Dilthey J. (23). Controlled auto ignition combustion process with an electromechanical valve train., [SAE ]. [3] Standing R. Kalian N, Ma T. Zhao H, Wirth M. Schamel A. (25). Effects of injection timing and valve timings on CAI operation in a multicylinder DI gasoline engine., [SAE ]. [4] Yap d. Karlovsky J.Megaritis A. Wyszynski M. Xu H. (25). An investigation into propane homogeneous charge compression ignition engine operation with residual gas trapping. Fuel, 25:84 (18) : [5] Babajimopoulos A, Assanis D, Fiveland S. (22). An Approach for modeling the effects of gas exchange processes on HCCI combustion and its application in evaluating variable valve timing control strategies., [SAE ]. [6] Jiang H, Wang J, Shuai S. (25). Visualization and performance analysis of gasoline homogenous charge induced ignition by diesel., [SAE ], [7] Gray AW, Ryan TW. (1997). Homogeneous charge compression ignition (HCCI) of diesel fuel; [SAE ]. [8] Christensen M, Johansson B, Amneus P, Mauss F. (1998). Supercharged homogeneous charge compression ignition; [SAE 98787]. [9] Christensen M, Johansson B, Einewall P. (1997). Homogeneous charge compression ignition (HCCI using iso-ocatane, Methanol and natural gas a comparison with spark ignition operation; [SAE ]. [1] Fuerhapter A, Unger E, Piock WF. (24). The new AVL CSI engine~hcci operation on a multi cylinder gasoline engine; [SAE ]. [11] Marriott CD, Kong SC, and Reitz RD. (22). Investigation of hydrocarbon emissions from a diesel injection gasoline premixed charge compression ignited engine; [SAE ]. [12] Keller J, Singh G. (22). Update on engine combustion research at Sandia National Laboratories; [SAE ]. [13] Sjoberg M, Edling LO, Eliassen T, Magnusson L, Angstrom HE. (22). GDI HCCI: effects of injection timing and air swirl on fuel stratification, combustion and emissions formation; [SAE ]. The First International Conference on Interdisciplinary Research and Development, 31 May - 1 June 211, Thailand 46.7