THESIS CONFIRMATION AND APPROVAL

This is acknowledged and confirmed that thesis entitled:

Effect of diesel displacement on the performance and emission on dual-fuel engine

by Muhammad Nabil Bin Mohammed Yazid Matric No. S46854

have been checked and all the suggested corrections have been done.

The thesis is submitted to Faculty of Ocean Engineering Technology and Informatics in partial fulfillment of the requirements for the degree of Bachelor of Applied Science (Maritime Technology).

Authorized by:

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Main Supervisor

Name: Dr. Wan Nurdiyana

Wan Mansor                                                                        Date: ……………

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Co-Supervisor (If any)

Name:                                                                                      Date: ……………

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Head of Programme

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DECLARATION

I hereby declare that this thesis is the result of my own research except as cited in the references.

Signature : ……………………………………

Name : Muhammad Nabil Bin Mohammed Yazid

Matric No. : S46854

Date : 14.7.2020

ACKNOWLEDGEMENTS

The final year project I have done was a great chance for learning process and to build up more of my knowledge in that field. Therefore, I consider myself as very lucky individual as I was provided with an opportunity and guidance by my supervisor, Dr. Wan Nordiyana Wan Mansor for his germinal ideas, invaluable guidance, continuous encouragement and constant support in making this project possible. I am also grateful for having a chance to participate in this project that led me through an experience to improve and develop something new. But first I would like to convey my gratitude towards almighty Allah for giving me strength and ability to finish my work during my project period with ease. Bearing in mind previous I am using this opportunity to express my gratitude and special thanks to University Malaysia Terengganu which give me a place for leaning processes and allowing me to carry out my project at their esteemed organization and extending during my study period. I express my deepest thanks to my lecturers for taking care of me during the study period and giving me necessary advices and guidance and who is spite of being busy with their duties, took time to hear, guide and keep me on the right path. I choose this moment to acknowledge their contribution gratefully. It is my radiant sentiment to place on record my best regards, deepest sense of gratitude to my fellow friends for their careful and precious guidance which were extremely valuable for my study both in theoretically and practically. Moreover, a lot of thanks to my beloved parents who helped me in my study and by giving a lot of their advice, assistance, suggestion and support. I perceive as this opportunity as a big milestone in my career development. I will strive to use gained skills and knowledge in the best possible way and I will continue to work on their improvement, in order to attain desired career objectives.

ABSTRAK

Pada masa ini, masalah terpenting yang berkaitan dengan enjin IC adalah prestasi, pelepasan pencemaran dan penggantian bahan bakar fosil dengan sumber yang boleh diperbaharui. Salah satu pendekatan untuk menyelesaikan masalah ini ialah enjin diesel diesel dua bahan bakar dengan gas asli sebagai bahan bakar tambahan. Walau bagaimanapun, kelemahan utama pembakaran dua-bahan bakar adalah kesan negatifnya terhadap prestasi dan pelepasan enjin. terutamanya pada karbon monoksida (CO) dan Hidrokarbon (HC) berbanding dengan operasi diesel standard. Objektif kajian ini adalah untuk mengetahui pengaruh anjakan diesel terhadap prestasi dan pelepasan enjin dua-bahan bakar dan untuk menyelidiki hubungan antara peratusan perpindahan diesel 10%, 25%, 50%, dan 75% dengan pelepasan dan prestasi dual – enjin bahan bakar. Data dikumpulkan dari kajian sebelumnya, yang dilakukan pada mesin diesel John Deere 6068H. Enjin diubah menjadi operasi dua-bahan bakar. Enjinnya adalah enjin tier II, 6-silinder, 6.8 liter, 4-stroke compression ignition (CI) dengan nisbah mampatan 17: 1. Di samping kajian eksperimental, model komputasi cecair dinamik (CFD) dikembangkan menggunakan perisian ANSYS untuk membantu memahami tingkah laku proses pembakaran bahan api gas / diesel gas asli. di bawah beban enjin yang berbeza. Eksperimen dilakukan pada kadar penggantian NG yang berbeza iaitu 10%, 25%, 50% dan 75% untuk mengukur prestasi enjin diesel. Kadar pelepasan haba yang diperoleh dari analisis diperiksa bersama dengan prestasi eksperimen dan data pelepasan. Hasil kajian menunjukkan bahawa melalui sapuan perpindahan diesel, beban rendah dan menengah mengalami kecekapan rendah dan pelepasan HC dan CO yang melampau kerana ketidakupayaan untuk mencapai penyebaran api yang mencukupi melalui campuran pracampuran yang terlalu ramping. Kesimpulannya, dari kajian ini, enjin dwi-bahan bakar dalam keadaan operasi yang sesuai mampu mengurangkan pelepasan dan mencapai pembakaran enjin diesel yang lebih bersih.

Kata kunci: enjin dwi-bahan bakar, enjin gas asli diesel, pelepasan, prestasi, anjakan diesel .

ABSTRACT

Nowadays, the most important issues relating to IC engines is the performance, pollutant emission and replacement of fossil fuel with renewable sources. One of the approaches to solve this issue is the dual-fuel diesel derived engine with natural gas as an auxiliary fuel. However, the main disadvantage of dual-fuel combustion is its negative effect on engine performance and emission. particularly on carbon monoxide (CO) and Hydrocarbon (HC) as compared to standard diesel operation. The objective of the study is to determine the effect of diesel displacement on performance and emission of dual fuel engine and to investigate the relationship between diesel displacement percentage of 10%, 25%, 50%, and 75% with emission and performance of dual fuel engine. Data gathered from previous studies, which was performed on the 6068H John Deere diesel engine. The engine was converted into dual-fuel operation. The engine is a tier II, 6-cylinder, 6.8-liter, 4-stroke compression ignition (CI) engine with a 17:1 compression ratio. Alongside the experimental study, computational fluid dynamic (CFD) model was developed using ANSYS software to help understand the behavior of natural gas/diesel dual-fuel combustion process. under different engine load. Experiment was performed at different NG substitution rate of 10%, 25%, 50% and 75% to measure the performance the diesel engine. Heat release rates obtained from the analysis were examined along with experimental performance and emission data. The finding indicates that through diesel displacement sweep, low and intermediate loads suffer from low efficiency and extreme HC and CO emissions due to the inability to achieve the propagation of adequate flame through the too lean premixed mixture. In conclusion, from this study, dual-fuel engine under appropriate operating condition are capable of reducing emissions and achieving cleaner combustion of a diesel engine.

Keyword: dual-fuel engine, diesel natural gas engine, emission, performance, diesel displacement

TABLE OF CONTENT

DECLARATION

TITLE PAGE

THESIS CONFIRMATION AND APPROVAL   ii

ACKNOWLEDGEMENTS  iv

ABSTRAK   v

ABSTRACT   vi

TABLE OF CONTENT   vii

LIST OF TABLES  x

LIST OF FIGURES  xi

LIST OF SYMBOLS  xii

LIST OF ABBREVIATIONS  xiii

CHAPTER 1 INTRODUCTION   1

1.1       Background of the Study  1

1.2       Problem Statement 2

1.3       Objective  2

1.4       Scope  2

CHAPTER 2 LITERATURE REVIEW    4

2.1       Engine  4

2.1.1    Dual-fuel background  4

2.1.2    Dual Fuel operations  4

2.1.3    Dual Fuel Emission  5

2.1.4    Dual-fuel performance  6

2.1.5    Compression Ignition Engine  6

2.2       EFFECT OF EXHAUST EMISSION   7

2.2.1    Carbon monoxide  7

2.2.2    Hydrocarbon  7

2.2.3    Oxides of Nitrogen (NOx) 8

2.2.4    Soot and Particulate Matter (PM) 8

2.3       EMISSION REDUCTION TECHNIQUE   8

2.3.1    Diesel Displacement 8

2.3.2    Fuel Spray Angle  10

2.3.3    High-Pressure Direct injection  10

2.4       Computational Fluid Dynamics (CFD) 10

CHAPTER 3 METHODOLOGY   13

3.1       Introduction  13

3.2       EXPERIMENTAL SETUP AND PROCEDURE   14

3.2.1    Combustion model 15

3.2.2    Modelling and Meshing  15

3.2.3    Meshing  16

3.2.4    Heat Release rate  16

3.3       EXPERIMENTAL PROCEDURE   16

3.4       POWER EQUATION OF CI ENGINE   18

3.5       EFFECT OF DIESEL DISPLACEMENT AND INJECTION TIMING   18

3.6       VALIDATION RESULT  19

CHAPTER 4 RESULTS AND DISCUSSION   21

4.1       Introduction  21

4.2       The Effect Diesel Displacement 21

4.2.1    Emission Analysis  22

4.2.1.1             NOx emission  22

4.2.1.2             CO emission  22

4.2.1.3             PM emission  22

4.2.1.4             THC emission  22

4.2.2    Engine performance  23

4.2.2.1             Brake specific fuel consumption  23

4.2.2.2             Brake thermal efficiency  23

4.2.2.3             Exhaust Temperature  23

CHAPTER 5 CONCLUSION   24

5.1       Introduction  24

REFERENCES  25

APPENDIX A SAMPLE APPENDIX 1  27

APPENDIX B SAMPLE APPENDIX 2  28

LIST OF TABLES

Table 3.2         The main features of the base engine  4

Table 3.3         The diesel displacement of diesel fuel by mass  4

LIST OF FIGURES

Figure 2.1        Basic Configuration of dual-fuel

Figure 2.3.1     Dual-fuel diesel displacement

Figure 3           Geometry of the cylinder and intake exhaust pipeline .

LIST OF SYMBOLS

LIST OF ABBREVIATIONS

CHAPTER 1

INTRODUCTION

1.1              Background of the Study

Internal combustion engines have been in use for more than a century and have undergone tremendous changes in design, materials used, and operating characteristics. Never had they lost their importance as the planet’s most widely used prime movers during their long history development. It is a well-known fact that the compression ignition (CI) or diesel engine is one of the most fuel-efficient power-producing units in use today. Hence, the importance of this type of engine has been long recognized, particularly in heavy-duty engine applications. Strong determination emerges to improve both performance and emission characteristics of internal combustion engines, has driven scientists and engineers working in this area to formulate and develop different parameter use on dual-fuel engine. Such solutions include a variety of operating parameters to minimize exhaust gas emission and to avoid sacrificing engine performance.

In order to reduce emissions, and without sacrificing engine efficiency, from direct injection diesel engines, engineers have proposed a variety of solutions, one of which is the use of gaseous fuel as a partial supplement for liquid diesel fuel. This engine knows as dual-fuel engine. Dual-fuel engine system is retrofit to CI engine (Mansor et al., 2015). In dual fuel engine, a gaseous primary fuel is inducted into the cylinder along with air. Dual fuel engines are described as engines that can work on two types of fuel, one gas and the other liquid gas (Basher & Growth, 2018).

Dual-fuel engine provides many of the operational advantages of conventional diesel power in this configuration. In particular, dual-fuel diesel offers similar high transient load response, which is so important in hydraulic fracturing operations (Tiwari, 2015). Dual-fuel operation with better specific energy consumption will produce higher performance than the corresponding diesel operation. Additionally, dual-fuel can provide better specific energy for higher performance. This can be achieved by offering superior emission characteristics, quieter and smoother operation, improved low ambient operation, and lower thermal charging compared to diesel operation (Evans, 1987). A dual-fuel engine is capable of reducing problematic diesel engine emission of NOx and smoke. The drawback is that, it is often accompanied by an increase in emission of CO and HC (Stewart et al., 2007)

1.2              Problem Statement

Stricter air pollution regulation of certain gas emission and increasing cost of fuel is another challenge that is faced by current manufacture. Their limited availability and environmentally impact have forced researcher in finding engine that can eliminate this problem. A dual-fuel engine is one of the ideal types of engine. In dual fuel engine, a gaseous primary fuel is inducted into the cylinder along with air. However, engine emission and performance suffer at low load. This is due to very lean mixture. the lean mixture are hard to ignite and slow to burn and part of unburn fuel will exit with exhaust gas. Therefore, the main reason of this research is to address the effect of diesel displacement parameters on different percentage of gas with the performance and emission of dual-fuel engine in order to improve efficiency and improve the control of exhaust emission

1.3              Objective

1. To determine the effect of diesel displacement on the performance and emission of dual-fuel engine
2. To investigate the relationship between diesel displacement percentage of 10%, 25%, 50%, and 75% with the performance and emission of dual fuel engine.

1.4              Scope

1. Tackle the problem of dual-fuel engine to increase performance and better control of exhaust emission using diesel displacement technique
2. Computational fluid dynamic (CFD) approach to predict combustion event and emission formation inside the cylinder.

CHAPTER 2

LITERATURE REVIEW

2.1              Engine

2.1.1        Dual-fuel background

In this chapter, studies have attempted to provide a short overview of the research work performed on dual fuel engines. Dual fuel operation has been under scrutiny since the early days of the compression ignition engine. Several early review including those (Evans, 1987) and (Karim, 1980) have demonstrate explained both the capability and the issues associated with it dual-fuel. The main objective of those research on dual-fuel engine is more on understanding in dual-fuel combustion to enhance the efficiency of conventional system in order to eliminate problem associate with air pollution. However, in more recent time, the ability of dual fuel operation to mitigate engine emissions and decrease diesel use has become a crucial factor.

2.1.2        Dual Fuel operations

The basic configuration of dual-fuel engine is shown in figure 2.1. in dual-fuel engine, a gaseous primary fuel (natural gas) is inducted into cylinder along with air. The intake of gaseous primary fuel is controlled by a throttle. The mixture is compressed and a small volume of diesel fuel is introduced at the end of the compression stroke to begin the combustion cycle. The main advantage of such an application is the easy conversion from conventional diesel to dual fuel operation without substantial changes to the overall design of the engine

Figure 2.1 Basic configuration of dual-fuel engine

Combustion of dual fuel engines is completely opposite from diesel engines. The dual-fuel engine is a standard CI style diesel engine in which some of the energy releases from combustion comes from the combustion of gaseous fuel (Krishnan, 2015). In contrast, the diesel liquid fuel continues to provide the remaining part of the energy released by timed cylinder injection. Since the diesel. combustion is basically heterogeneous, dual fuel combustion requires the initial combustion of the pilot fuel, which then ignites the lean premixed fuel-air mixture.

2.1.3        Dual Fuel Emission

The principal of dual-fuel (DF) combustion is a promising technique for the modern gas engines to achieve simultaneously low emission of unburned hydrocarbon (UHC) and of nitrogen and sulfur oxide (NOx, SOx). The Modern gas engines that work with e.g. natural gas achieve the desired properties with comparable efficiency with existing diesel engine (Kahila et al., 2019). Importantly, natural gas contains mainly methane (CH4), which naturally induce lower emissions of (CO2) due to lower carbon content.

2.1.4        Dual-fuel performance

For the specification of the engine, the performance of the engine is determined uniquely by the way fuel is inserted into the combustion chamber, which in turn is determined by the design of the fuel injection device.  The net Heat Release Rate (HRR) is determined by measuring the amount of heat produced from the fuel to achieve the predicted values pressure, while the magnitude of the combustion reaction is calculated by the released fraction of the total chemical energy from the fuel (Mansor et al., 2015).

Many researcher have performed different studies to investigate the performance  and challenges  that are encountered in dual fuel engine.  (Bari & Hossain, 2019) Bari et al. reported. The duel fuel engine performance is dependent on the gas being combusted inside the cylinder. The combustion of gas is effected by the homogeneity of the air -gas mixture, flame speed of the gas and load of engine

2.1.5        Compression Ignition Engine

The dual-fuel combustion process in CI primary features the rapid compression of the gas-air mixture below its auto-ignition condition. According to (Pulkrabek, 2013), CI (CI) engine is an engine which the combustion cycle begins when the air-fuel mixture is self-igniting due to high combustion chamber temperature induced by high compression. CI engine is often referred to as diesel engine, especially in the non-technical community.

2.2              EFFECT OF EXHAUST EMISSION

Air pollution is a global concern. For example, in Malaysia, engines operated using diesel fuels were recorded as the main contributors of air pollutants and also one of the largest automobile manufacturers and users in Asia. (Jahirul et al., 2007). The consumption of conventional fuels by a motor vehicle such as diesel and petrol would significantly donate to air pollution, global climate change, acid rain, and respiratory problem.

2.2.1        Carbon monoxide

Carbon monoxide were produced by the oxidation reaction of carbon-containing compounds; it forms where there isn’t enough oxygen to produce carbon dioxide (CO2). Throughout the presence of oxygen, including atmospheric concentrations, carbon monoxide burns with a blue flame will produce CO2 (Speight, 2017). Out of all the gases being produced by human activities, the largest supplier to the air pollutant is CO2. Due to the rising number of cars using liquid fuels, the amount of CO2 in the atmosphere continues to increase. Regulation of CO2 emissions would seem to be a significant problem. (Jahirul et al., 2007)

2.2.2        Hydrocarbon

Within diesel engine exhaust, hydrocarbon range from a few parts per million (ppm) to thousands of ppm depending on engine speed and load (Pathak & Nayyar, 2017). Hydrocarbon emission enters the atmosphere, behave as irritants and odorant; and some are carcinogenic (Pulkrabek, 2013).

2.2.3        Oxides of Nitrogen (NOx)

NOx is the most significant emission emitted by the diesel engines among the gaseous pollutants. NOx varies from a couple hundred to 1000 ppm in many engines. The release of NOx is one of the primary sources of photochemical smog in the atmosphere. NOx were reduced in modern engines with fast-burn combustion chambers, which depend on the location within the combustion chamber (Pulkrabek, 2013).

2.2.4        Soot and Particulate Matter (PM)

Emission from the engine has adverse effects on the environment and the composition of the atmosphere on earth. However, the diesel engine is one of the main contributors to pollution in the atmosphere. The main hazards emission of the diesel engines is NOx and particulate matter (PM). NOx emission is one of the major causes of photochemical smog, and it is also responsible for acid rain.

2.3              EMISSION REDUCTION TECHNIQUE

Dual fuel efficiency and emissions can be minimized by engine configuration and operating parameters. The following parameters have been studied by previous researchers with a view to enhance engine performance and efficiency.

2.3.1        Diesel Displacement

Diesel displacement occurs in an engine by adding natural gas as a combusted fuel source known as “dual-fuel”.  These terms were used to characterize this parameter, and can be described as “mixed fuel”. In general, dual-fuel terms were used to describe the use of natural gas with diesel combustion. The mixture is compressed and a small volume of diesel fuel is introduced at the end of the compression stroke to continue the combustion cycle. No changes shall be made to the internal function of the engine or the diesel injection system. The natural gas would displace some of the diesel needed to operate the engine, reducing the consumption of diesel fuel at the same power output (Mansor et al., 2015).

Basic operation of diesel displacement is shown on Figure 2.3.1. The term “Dual-fuel” has been used of this paper to identify compression-ignition reciprocating engines that are capable of co-combusting diesel fuel with CNG. It is also possible to run a dual-fuel diesel engine on diesel, providing flexibility to continue operations even if gases fuel is not available. (Tiwari, 2015).

Figure 2.3.1 dual-fuel diesel displacement

(Mansor et al., 2015)  Mansor et al. studied the effect of diesel displacement on the emission characteristics of diesel derivative dual fuel engine, through diesel displacement, during low loads, the dual fuel system provides more gas than can be used, resulting in very high THC and CO emissions. The high THC emissions for dual fuel are the product of incomplete combustion, mainly of lean air and natural gas mixtures. CO emissions depend on the equivalence ratio, the partly burnt gaseous fuel and the temperature of the cylinder. It can be improved by shutting down the dual fuel before intermediate loads were reached and increase the diesel displacement at intermediate load and high load.

2.3.2        Fuel Spray Angle

Fuel spray angle is also one of the parameters used to reduce emission and improve the dual-fuel engine’s performance and emission. Fuel is introduced by injecting the complexity of describing the physics of spray. It is defined as vaporizing two-phase flows that vary spatially and temporally from very dense to fairly diluted condition (Ambarita, 2017).

(Ekaab, 2017) Ekaab et al. organized an experimental work rectify the effect of fuel spray angle on emission of pollutant from continues combustion process. Through this parameter, increasing in spray angle decrease CO and increase NOx emission and soot. It is because when the spray angle increase, the diameter of droplet size decrease, which as a result increase the contact between fuel and air. increasing in spray angle enhance the evaporating rate and peak temperature near the nozzle.

2.3.3        High-Pressure Direct injection

In dual fuel engine, natural gas is directly injected into each cylinder when the piston is very close to the end of the compression stroke and the injected gas is mixed with compressed combustion air. Pilot diesel fuel is mixed with natural gas, normally by a modified injector that supplies both fuels. As the amount of natural gas increase, additional control must be to this system to ensure correct timing of fuel injection. NOx reduction of about 40% has been achieved (Of et al., 2003).

2.4              Computational Fluid Dynamics (CFD)

With the expanded computational power of modern computers, CFD has been useful for a variety of applications including diesel engine research, design and development. It also eliminates the time and costs involved with standard prototyping and testing of the engine concept to design and build fuel-efficient and low-emission engines (Thermal, 2016). The computational cases are based on the experiment carried out on a research.

ANSYS’ ICEngine module is gaining popularity as it takes much less time compared to other simulation techniques and we can also quickly conduct port flow simulation, simulation of combustion, simulation of cold flow easily. ANSYS IC Engine has an intuitive guide and is user friendly. Capable of forecasting gas flow patterns, Fuel spray patters, and other Fluent-like functions. It helps to understand the IC Engine heat transfer that causes thermally induced stresses affecting the life of engine parts and thus helps to design and develop better engines for greater durability and efficiency.

(Thermal, 2016) Thermal et al. conducted a simulation of dual-fuel natural gas-based IC engine using ANSYS ICE package. The ANSYS software is used to investigate the flow, heat and pollutant analysis. The result were analysed to get the values of heat transfer rate, temperature, dynamic and average pressure, the torque created and emission of combustion process. From the result, the total heat transfer rate at various flow rate and the total heat release rate at various crank angle were found to be comparable with the extrapolated experimental result of natural gas based dual fuel engine. ANSYS ICE simulation result were compared with the experimental value and found that the predicted values are in conformance with the experimental values

CHAPTER 3

METHODOLOGY

3.1              Introduction

The simulation will be performed using meshed domain in Figure 3 which are the geometry of the cylinder and intake exhaust pipeline.

Figure 3: Geometry of the cylinder and intake exhaust pipeline

3.2              EXPERIMENTAL SETUP AND PROCEDURE

The engine specification that has been selected to investigate the effect of diesel displacement on the performance and emission of Dual-fuel is listed in table 3.2.

Table 3.2 : The main features of the base engine

3.2.1        Combustion model

In this paper, the dual-fuel engine is use. The structure and principle of dual-fuel engine are similar to diesel engine. Building the model and investigate the performance and emission of dual-fuel engine will be develop by using ANSYS software.

3.2.2        Modelling and Meshing

The first phase in the development of the John Deere engine computing model includes the use of 3-D simulation tools to simulate the combustion chamber. Since the focus here lies in the fluid dynamics that dominate the combustion process, the chamber fluid volume was modeled. Precautions were taken to validate the exact measurements used to construct a correct model. Any inaccuracies in this volume (or known as clearance volume) result in an inaccurate compression ratio causing temperature and pressure fluctuations during compression. The compression ratio equation is shown below (Adam Michael Blake, 2012)

Equation 1: Compression Ratio

The compression ratio can change by altering the clearance or the volume of displacement. Changes to the piston bore or to the stroke will change the volume of the displacement. For this study, a various of compression ratio are to be used. The displacement volume equation is shown below

Equation 2: Displacement volume

Additionally, the structure of the piston bowl plays a significant role in the flow properties inside the chamber. (Xu et al., 2018) Xu et al. conducted a study on the effect of the piston shapes through biodiesel mixture combustion on diesel engine. The piston bowl’s size and shape impact air and fuel flow during the compression stroke, thereby influencing the air / fuel mixture. A strong combination helps in more effective combustion, resulting in more efficiency or fuel economy. The use of an appropriate piston bowl design will also reduce the in-cylinder emissions (such as NOx and soot) and post-treatment costs.

3.2.3        Meshing

Meshing is taken once a solid model of fluid volume develop on ANSYS Workbench is completed. Factors considered when designing the mesh included optimal precision for a reasonable number of elements. This ensures that a computational model with a reasonable computational time produces repeatable results.

3.2.4        Heat Release rate

In addition to combustion, changes in the volume of the combustion chamber are also affected by cylinder pressure due to piston travel, heat transfer to the walls and blow-by. To analyze the combustion process, it is therefore important to link each of the above to the increase in pressure and to differentiate the combustion effect from the other effects.

3.3              EXPERIMENTAL PROCEDURE

In this test, the point at five engine loads were taken correspond to 10%, 25% 50%, and 75% of the maximum load to be obtained from the test plan.

3.2. The diesel displacement of diesel fuel by mass

3.4              POWER EQUATION OF CI ENGINE

A detailed study of the CI engine can be achieved by analyzing the energy input found in the fuel and the power output available. However, the output power available at the fly wheel is known as brake power, Pb. The use of thermal brake efficiency is convenient for multi-operation, which is defined as the ratio of brake power divided by the energy input contained in the fuel. Algebraically,

Where,

Pb = Brake power, measured at fly wheel 1

nb = Brake thermal efficiency,

mf = Mass flow rate of fuel

Q = The lower heating value of fuel

3.5              EFFECT OF DIESEL DISPLACEMENT AND INJECTION TIMING

Effects of the quantity of pilot fuel and the timing of the injection will be considered to boost efficiency and the emission. At each of the five loads, a diesel displacement sweep is performed to determine operating limits and devise an optimal replacement scheme that will maximize diesel displacement. There is also a review of the injection timing to consider the effect of phasing combustion on combustion and emission. On this particular study, the spacing around the SOI is both advanced and retarded before engine instability or exceptionally high rates of emission have been detected

3.6              VALIDATION RESULT

In order to validate the simulation result, the data obtained from the previous study will be compare with the result obtained. The previous study has been carried out an investigation of the effect of diesel displacement on the performance and emission of dual-fuel engine by using John Deere 6068H diesel engine converted to dual-fuel operations. The engine is tier II, 6-cylinder, 6.8 Litre, 4-stroke compression ignition engine with a compression ratio of 17:1 and a power rating of 168 kW at 2200 rpm. Commercial Converge CFD code is used to understand the location of emission inside the cylinder.

CHAPTER 4

RESULTS AND DISCUSSION

4.1              Introduction

The result obtained, indicates that measurement is under two separate modes of service, baseline diesel and dual-fuel operation. The objective of the analysis is to examine the phenomena within the combustion chamber, the stability of the combustion, the cylinder pressure, the total average thermal release rate and the data generated by the fraction is provided. Additionally, the diesel displacement and injection timing sweeps is provided with emission and engine output data.

4.2              The Effect Diesel Displacement

In dual-fuel operation, it is expected that low and intermediate loads suffer from high CO and extremely high levels of THC emissions. To optimize diesel displacement, at every load, natural gas substitution sweep is performed to evaluate operating limits and establish an optimized swap technique to optimize diesel displacement whereas reducing emission.

4.2.1        Emission Analysis

4.2.1.1       NOx emission

NOx emission is showing a small decreasing trend as diesel displacement increase. Each emission species shows a different pattern at 50% load. During the displacement of diesel, NOx emission is showing a steady declining pattern as diesel displacement increases. As diesel displacement decrease by 0% to a maximum diesel displacement of  NOx, the emission is decreased by approximately half.

4.2.1.2       CO emission

When diesel displacement increases, CO emissions increase slowly, peaking nearly 60%  of diesel displacement, then decrease significantly with the increase of diesel further. (Mansor et al., 2015)

4.2.1.3       PM emission

     PM emission is lower for increase load under dual-fuel operation except for high load, which exhibits 60 percent higher PM than regular diesel service. The PM emission displays a rising trend in normal diesel operation, with the increase of the load. The uses of natural gas is one of the alternative that tend to reduce PM emission because natural gas contains methane, the simplest hydrocarbon primarily. (Mansor et al., 2015)

4.2.1.4       THC emission

     THC emission for both diesel and dual-fuel decrease with increase load and is minimum at 100% load. At low loads the natural gas Φ and diesel jet is the lowest at low loads, potentially leading to high low load THC emission. Therefore, the high THC emission for dual-fuel is a result of incomplete combustion, primarily of the lean air and natural gas mixture. THC emission increase with increase diesel replacement throughout the entire sweep. (Mansor et al., 2015)

4.2.2        Engine performance

4.2.2.1       Brake specific fuel consumption

According to recent research (Bari & Hossain, 2019), brake specific fuel consumption (bsfc) is compared with diesel consumption. The percentage of diesel fuel was reduced with the increase of the percentage of natural gas, and the brake specific fuel consumption increased for lower loads. As the load increased, the combustion of natural gas was higher and the bsfc decreased by a percentage of natural gas, i.e. a drop in the percentage of diesel was still higher than 100% diesel but much lower than those with lower load.

4.2.2.2       Brake thermal efficiency

It was found that the maximum thermal brake efficiency for all variations in diesel consumption was at the highest power. It’s because the gas flow rate for lower % of diesel consumption was exponentially higher. This is due to the substantial impact of flammability and therefore the combustion was low at lower diesel consumption at lower power. (Bari & Hossain, 2019)

4.2.2.3       Exhaust Temperature

     The exhaust gas temperature decreased as the percentage of diesel consumption increased at all capacities to 60% diesel consumption. This is because of the lower peak cycle temperature of natural gas, which has  lower flammability.

CHAPTER 5

CONCLUSION

5.1              Introduction

The effect of diesel displacement on the characteristics of emission and performance under different load conditions was analyzed, and the following conclusion was established.

1. Dual-fuel operations emit up to 98% of THC emission and 70% of CO emission. While the trend is increase with loads, the values is still substantially higher than the baseline diesel.
2. In dual-fuel operation, NOx emission was reduced by up to 47%. Maximum reduction occurs when the engine works with the very lean premixed mixture at low loads.
3. Maximum PM emission reduction was achieved at 60% lower than baseline diesel when 35% of diesel fuel was displaced at 12 per cent load in dual-fuel service.
4. Optimum diesel consumption for better bsfc and thermal brake efficiency was found to be 60%
5. At around 60% of diesel consumption, the exhaust temperature was also low.

REFERENCES

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APPENDIX A
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APPENDIX B
SAMPLE APPENDIX 2

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