CHAPTER-3
3.4 Experimental Methodology and Procedure
3.4.2 Experimental Procedure
The present work is focused to test whether the biodiesel can be preheated and used as a blend with diesel in the engines. It is also intended to investigate the performance, emission and combustion characteristics of the engine using preheated biodiesel blends with diesel and intake air preheating using modified operating parameters of conditions of CR-IP-IT of VCR DI compression ignition. In this regards, the important experiments carried out in the entire thesis are mentioned in test matrix of the experiments in Table 3.3. Firstly, to establish a basis for comparison of results and to ensure the consistency of the experimental observations, baseline performance tests were carried out with the operating on diesel fuel only. Secondly, characterization the different blends of biodiesels (POME and COME with diesel), which are tested in a diesel engine characteristics investigation. Thirdly, characterization preheated neat biodiesels oils (POME and COME) at different heating temperatures, which are tested in a diesel engine characteristics investigation. Fourthly, characterization preheated biodiesel (POME) and blended with diesel at different blends ratios, which are tested in a diesel engine characteristics investigation. Fifth, the effect of preheating intake air at different preheating temperatures were investigated in a diesel engine characteristics investigation. Finally, the combined effects of fuel and intake air preheating is investigated in the VCR engine for various combinations of CR (16, 17.5 and 18), fuel IP (188, 200, 212 and 224 bar) and fuel IT (19, 23, 27º bTDC) at 90% of engine load with 30% EGR rate.
3.4.2.1 Investigations with the Baseline Tests
The experiment is performed to launch the foundation for comparison of results and to ensure the consistency of the experimental observations. The baseline performance tests were carried out
with the engine operating on mineral diesel fuel only. The variations of loads ranges from a minimum ‘no load (0.1 kg) to maximum full load (12 kg) with a step of 2.4 kg. The engine tests were conducted for the entire load range i.e., 0% to 100% with an increments of 20%. The standard setting (CR=17.5, fuel IP = 200 bar and IT=23° bTDC) is maintained while operating the engine with diesel at constant speed of 1500±50 revolution per minute (rpm) thorough out the load range.
Initially, the engine is allowed to run at no-load condition for a few minutes to warm up. The water flows are adjusted to 300 and 100 liters per hour for the engine cooling and calorimeter respectively according to the engine supplier instructions. Then, as per experimental design, a load level was set for engine operation. In each test, the operating conditions were stabilized, the engine was ready to present the baseline results. The variables that were continuously measured were recorded. For this, the following data were recorded manually (referring to Figure 3.1);
dynamometer load, speed, temperatures (T1-T6), the difference in liquid level in the manometer for air flow (∆H) and time required to volume of diesel fuel consumption 5 mL of fuel, cylinder and fuel pressure variation are automatically detected by the DAC. Then important performance and combustion characteristics parameters were calculated. All these data were saved in the appropriate format for further analysis. The samples of flue gas are then allowed to pass through the AVL 444 DIGAS flue gas analyzer probe, which quantifies the amount of CO, CO2, HC, NOX
and O2 emissions. Thereafter, the load level is raised as mentioned in the experimental matrix (Table 3.3) and the same processes as described above are repeated for subsequent load.
3.4.2.2 Investigations with the Fuel Blending
In this study the effect of biodiesel and diesel blending at different ratios (0–100% by volume) on some physical and chemical properties has been studied and presented. These properties include kinematic viscosity, density, cloud point, pour point, flash point, fire point, calorific value and cetane number. The fuel properties tests were conducted in a chemical laboratory under controlled temperatures and humidity to ensure accurate results. The first objective of this study was to characterize the properties of the castor oil methyl esters (COME) and palm oil methyl esters (POME), including the kinematic viscosity, density, cloud point, pour point, flash point, fire point, calorific value and cetane number. Furthermore, the properties of the COME and POME were compared with international biodiesel standards (ASTM D6751, EN14214 and IS15607). The COME and POME showed medium fuel properties to satisfy most biodiesel specifications. Only
the kinematic viscosity and density of the COME and POME, somewhat exceeds the upper limit of biodiesel specifications. Because the they showed satisfactory biodiesel properties, the COME and POME was further blended with diesel for the applications of current mandates, including neat diesel fuel (BD0) and neat biodiesel (BD100), nine COME/POME–diesel blends were prepared by blending the COME/POME with diesel at proportions of (10−90% by volume) with 10%
increments, corresponding to the (BD10−BD90) fuels, respectively. The second objective was to investigate the properties of diesel and COME, diesel and POME blends at different blending ratios (BD0-BD100) to determine the optimal blending proportion in comparison with the biodiesel- diesel blend specifications. The second objective of this study was to investigate engine performance and pollutant emissions in the use of COME/POME and diesel blends (BD0, BD10, BD20, BD30 and BD40) in a variable compression ratio (VCR), direct injection (DI) compression ignition (CI) engine in which the effect of blending was addressed.
3.4.2.3 Investigations with the Fuel Preheating
Preheating of COME/POME was carried out using fuel heating equipment, i.e helical coiled heat exchanger mounted just upstream of the fuel pump. After COME oil and POME oil characterization, a heat exchanger was designed and developed in the laboratory for heating the fuel using waste heat of exhaust gases of the engine. The developed helical coil heat exchangers have been built in to exhaust gas piping lines and as shown in Figure 3.11. Another fuel tank used for storing biodiesel and fuel supply system were developed and attached with prepared heat exchanger to preheat the biodiesel. A two-way switch was employed to change the fuel supply to the engine from diesel fuel to biodiesel while the engine was running. The developed preheating arrangement was attached to the engine for the completion of experimental set up. The main objective of this experimental study is to determine the effects of the kinematic viscosity and density of castor oil methyl ester and palm oil methyl ester (which is decreased by means of preheating process) on the performance parameters and exhaust emissions of a diesel engine. For this aim, biodiesel was preheated up to eight different temperatures (54°C – 138°C) with increment of 12°C, and its properties of biodiesels (COME and POME) were determined and studied offline for certain ranges of fuel preheating temperatures (test matrix-Table 3.3). Theses ranges of temperatures were determined from the initial experiments carried out in a diesel engine using in the fuel preheater of the existing experimental setup. The property values are compared with
respect to diesel as per international standards (ASTM D6751 and EN 14214). Then, tested in the diesel engine at full load conditions (12 kg) and speed of 1500 rpm. The main intention of this exercise is to have an initial assessment of fuel preheating temperature at which the best performance with lower emissions are achieved. During this phase of experiments with engine using preheated biodiesels were varied at different temperatures. Finally, the engine performance and emission parameter results were compared carefully, to make recommendation for the optimal/maximum fuel preheating temperature which is suitable for best engine performance and emission parameters of the engine.
3.4.2.4 Investigations with the Fuel Preheating and Blending
An alternate fuel supply system was developed with inbuilt heat exchanger to preheat the biodiesel oil and its blends. The developed preheating arrangement was attached to the engine for the completion of experimental set up. In this experimental investigation, the sequence of experimental tests involves the following procedures:
(a) Biodiesel blends in different proportions on a volume of biodiesel from 0% to 100% in regular steps of 20% of castor oil methyl ester or palm oil methyl ester are prepared. The blends of fuel were denoted as BD0, PBD20, BD40, BD60, BD80, and BD100. The important fuel properties of different samples blend of fuels (preheated + blended) were experimentally evaluated/measured by laboratory. All the tests were conducted the biodiesel preheated at elevated fuel temperature of 114°C before blending with diesel. The blend was stirred well with the help of a mechanical agitator, to get a homogenous stable mixture. Thus, properties of the fuel were obtained by groups of tests are included the kinematic viscosity, specific weight (density), flashpoint, calorific value, cetane umber, etc. based on the American Petroleum Institute (API) standard procedure. The device specifications and test procedure are in accordance to the American Society for Testing Materials (ASTM D6751), European union (EN14214) and Indian standard (IS15607).
(b) The various blends of preheated biodiesel has been tested in a diesel engine at operating at standard ( CR 17.5, IP =200 bar and IT = 23° bTDC) conditions. Preheating biodiesel was done before blending with diesel fuel, and blending was done in a glass burette based on the requirements of percentage fractions biodiesel ratio. The flow of biodiesel and diesel flow was controlled by manually operated two-way control valve ‘v1’ and ‘v2’, respectively (refer
Figure 3.13). Initially engine test run is done with diesel fuel (BD0) for baseline case data.
Then, major experiments on diesel engine for the investigation and measurement of performance and emission characteristics were executed with different preheated blends of fuel at elevated (114°C) optimum fuel temperatures with variations of engine load (10− 90 %) with 20% increments, and compared the results with a bassline diesel data. Then, with a variation EGR rates (0−40 %) with 10% increments at full engine load condition, and compared the results with a bassline diesel data. Finally, blends of fuel were optimized for better engine performances and emissions characteristics.
3.4.2.5 Investigations with the Intake Air Preheating along with Preheated Blend Ratios It is having different combinations using both preheated intake air and preheated blends of fuel as a fuel in CI engine, and its effect on the performance, combustion characteristics and emissions of compression ignition (CI) engine. In this investigation, first the effect of intake air preheating on diesel engine performance and emission parameters are examined with variation of intake air preheating temperature (33, 41, 49 and 61°C) using various preheated blends of fuel (114°C elevated fuel temperature) at 90% of engine loading condition (refer Figure 3.15). Thus, the required intake air preheating temperature was obtained thoroughly investigations diesel engine parameters results. All the tests were conducted at the standard operating of diesel engine (CR=17.5, fuel IP = 200 bar, and fuel IT = 23° bTDC) with a rated speed of 1500 rpm.
3.4.2.6 Investigation with the Modified Parameters (CRs-IPs-ITs)
The main objective is to investigate the impact of modified parameters i.e. varying CR, IT, IP. All the tests were conducted by starting the engine with diesel only. After the engine was warmed up, it was switched to the VCR operation herewith online modification of CR, IP, and IT variation.
The various combinations of CR, IP, and IT are incorporated in test matrix (Table 3.3). Each tests were conducted at elevated temperature of fuel (114°C) and intake air (61°C) with constant 90 % (10.8 kg) load running conditions at 1500rpm. According to the company user manual, all the tests were conducted by starting the engine with diesel only at the standard CR of 17.5, IP of 200 bar, and IT of 23º bTDC. Then, according to requirement, the CR/IP/IT/ has to be changed into the intended test position for operation separately or combination. In each test, the operating conditions were stabilized and the variables that were continuously measured and recorded. The sequence of experimental tests involves the following:
(a) The percentage change in performance, combustion and emission characteristics of various blends at varying CR (16, 17.5 and 18) as compared to diesel, and the best CR, which provides improved engine characteristics are identified.
(b) In this section, impact of changing fuel IP (200, 212 and 224 bar) on the characteristics of diesel engine at different operating conditions have studied. The percentage change in performance, combustion and emission characteristics of various blends at varying IP with optimal CR as compared to diesel. Thus, the optimal fuel IP is also identified.
(c) The percentage change in performance, combustion and emission characteristics of various blends at varying IT (19, 23 and 27º bTDC) at optimal CR and fuel IP is compared to diesel.
(d) Finally, the best combination of CR-IP-IT that results is recommended best engine characteristics.
The experiments are performed maintaining the procedure described by Bureau of Indian Standard (BIS). The standards are described through IS 10000 (Part I to Part XIII) – 1980 (IS 10000). The performance and emission parameters are measured thrice as per experimental design for diesel, POME/COME biodiesel−diesel blends, preheated POME/COME biodiesel, preheated POME biodiesel/diesel blends and intake air preheating mode and averaged for each operating point. The average values of the recorded experimental data are employed for analysis purpose.
The equations (A1−A15) used for performance and combustion analysis are provided in Appendix A. During the analysis of heat release rate, it is necessary to use the ratio of specific heats γ. The value of γ is essentially dependent on combustion temperature, which is known to be very non- linear and ranges amid 300 K to 1700 K. Further, it is very difficult to measure the trend of actual combustion temperature. Hence, traditional practice is to use a mean value of γ for the calculation of heat release rate. As quoted by (Heywood, 1988; Pundir, 2010)and many other researchers, the mean value of γ lies within 1.3 to 1.35 for single cylinder, CI, diesel engine of low to mid ratings.
In this study, after multiple inspection, the value of γ is considered is 1.35. The justification of this is provided in Appendix A, with the help of ideal gas law and correlations provided by (Goering, 1998; Hansen, 2013)spatially averaged temperature in the combustion chamber. The heat release rate measured by variable γ and constant γ of 1.35 are well matched. All the experiments are executed within 20±2ºC and atmospheric condition.
Table 3.3: The test matrix for studying the engine characteristics of preheated biodiesel-diesel blends of fuel in VCR CI engine.
Major Work Activities Conditions
Blending
Characterization of the properties of COME and POME Preparation different blends fuel and its fuel properties characterization
Prepared blends of fuels are: (BD0, BD10, BD20, BD30, BD40, BD50, BD60, BD70, BD80, BD90, BD100)
Performance and emission parameters evaluation using blends of fuel
Test fuels (BD0, BD20, BD30, and BD40) at standard (CR=17.5, fuel IP = 200 bar, fuel IT = 23° bTDC)
Preheating
Characterization the properties of preheated neat COME/ POME. Preheating biodiesel at different fuel temperatures (54 °C−138 °C).
Evaluation of diesel engine Performance and emission parameters using preheated biodiesel.
Preheating biodiesel at different fuel temperatures (54 °C−138 °C) at full load operating condition.
Preheating and blending
Preparation of preheated blends of fuel and its fuel properties
characterization. Test fuels are: (BD0, PBD20, PBD40, PBD60, PBD80, PBD100)
It is also studied thermodynamics and thermos-economic analysis of preheated blends of fuel run in the diesel engine
Test fuels are: (BD0, PBD20, PBD40, PBD60, PBD80, PBD100) at standard operating conditions (CR=17.5, fuel IP = 200 bar, fuel IT = 23° bTDC) with a variation of loads (10%, 50% and 90%).
Investigations of engine performance, combustion characteristics and emission parameters using preheated blends of fuel.
Test fuels are: (BD0, PBD20, PBD40, PBD60, PBD80, PBD100) at standard operating conditions (CR=17.5, fuel IP = 200 bar, fuel IT = 23° bTDC) variation of engine loads (0−100%) with increments of 20% with no-EGR rate. And then, with variation of EGR rates (0%EGR−40%EGR) with increments of 10% with fuel engine load.
Preheating blends of fuel and intake air
Investigations engine performance, combustion and emission
characteristics using preheated biodiesel blends of fuel (114 °C). Preheating intake air at different temperatures (33 °C−61°C) in steps 12 °C at full load condition.
Modified operating parameters
Investigation the impact of modified parameters (CRs-IPs- ITs) on diesel engine
characteristics using preheated blends of fuel and intake air at 90% load.
Fuel injection pressure (bar) Fuel injection timing (° bTDC)
200 212 224 19 23 27
CR (BD0):17.5 - - - CR (BD0):17.5 -
CR (PPBD20):16 CR (PPBD20):16 CR (PPBD20):16 CR (PPBD20):16 CR (PPBD20):16 CR (PPBD20):16 CR (PPBD40):17.5 CR (PPBD40):17.5 CR (PPBD40):17.5 CR (PPBD40):17.5 CR (PPBD40):17.5 CR (PPBD40):17.5 CR (PPBD60):18 CR (PPBD60):18 CR (PPBD60):18 CR (PPBD60):18 CR (PPBD60):18 CR (PPBD60):18
POME-Palm Oil Methyl Ester, COME−Castor Oil Methyl Ester, BD0- Neat diesel fuel, PPBD-Preheated palm biodiesel.