CHAPTER 5 EXPERIMENTAL SET UP AND TESTING PROCEDURES

Transcription

1 45 CHAPTER 5 EXPERIMENTAL SET UP AND TESTING PROCEDURES 5.1 OBJECTIVES To find the suitability of METPSO as a fuel in CI engine, following experimental techniques are adopted. 1. Regular experiments on a computerized diesel engine. i.e., Performance and combustion characteristics of an engine fueled initially with diesel and followed by METPSO and its blends. 2. Exhaust gas analysis (CO, CO 2, HC, NO x, O 2 and Smoke intensity). 3. Effect of injection timing and injection pressure on neat METPSO fueled CI engine to determine the optimum condition. 4. Experiment on peroxidized METPSO fueled CI engine. 5. Effect on EGR on CI engine performance and emission. 6. Effect of compression ratio on CI engine performance and emission characteristics.

2 EXPERIMENTAL TEST SET UP A 3.5 kw, 1500 rpm, Kirloskar diesel engine is used in this investigation as shown in Figure 5.1. The detailed specification given in Table 5.1. Two separate fuel tanks with a fuel switching system are used, one for diesel (D100) and the other for biodiesel (B100). Fuel consumption is measured using optical sensor. A differential pressure transducer is used to measure airflow rate. Engine is coupled with an eddy current dynamometer to control engine torque through computer. Engine speed and load are controlled by varying excitation current to eddy current dynamometer using dynamometer controller. A piezoelectric pressure transducer is installed in engine cylinder head to measure combustion pressure. Signals from pressure transducer are fed to charge amplifier. A high precision crank angle encoder is used to give signals for top dead centre and crank angle. The signals from charge amplifier and crank angle encoder are supplied to data acquisition system. An AVL exhaust gas analyzer and AVL smoke meter are used to measure emission parameters and smoke intensity respectively. Thermocouples (chrommel alumel) are used to measure exhaust temperature, coolant temperature, and inlet air temperature. Figure 5.1 Experimental setup

3 INSTRUMENTATION DETAILS Eddy Current Dynamometer An eddy current dynamometer of 3.5 kw (1500 rpm) capacities is directly coupled with the engine. The engine and air cooled eddy current dynamometer are coupled using tyre coupling. The output shaft of the engine is connected to the dynamometer through a torque transducer for measuring torque. A torque transducer provides an electrical signal that is proportional to torque. A load cell is an electronic device (transducer) that is used to convert a force into an electrical signal. The load to the engine can be varied by operating the potentiometer provided on the panel or through computer Air Flow Sensor The air flow to the engine is routed through cubical air tank. The rubber diaphragm fixed on the top of the air tank takes care of neutralizing the pulsation for airflow measurement. The inlet air tank is provided with an orifice. The differential pressure of air was measured in the computer using a differential pressure transducer (0-99 m 3 /hr) calibrated to indicate volume airflow. The pressure ports are connected to instrumentation panel using smooth flexible hose. The pressure drop across the orifice is measured using a differential pressure transducer. The output of the differential pressure transducer is amplified using an instrumentation amplifier and fed to the data acquisition card. The differential pressure sensor use state of the art silicon micro machined pressure sensor in conjunction with stress free packaging techniques to provide highly accurate, amplified, calibrated and temperature compensated pressure readings.

4 Fuel Flow Sensor The fuel from the tank was connected by way of a solenoid valve to a glass burette and the same is connected to the engine through a manual ball valve. The fuel solenoid of the tank will open and stay open for 30sec, during this time fuel is supplied to the engine directly from the fuel tank and also fills ups the burette. After 30 sec the fuel solenoid closes the fuel tank outlet, and now the fuel in the burette is supplied to the engine. When the fuel level crosses the high level optical sensor, the sequence running in the computer records the time of this event. Like wise when the fuel level crosses the low level optical sensor, the sequence running in the computer records the time of this event and immediately the fuel solenoid opens filling up the burette and cycle is repeated. Now, volume of the fuel between high level and low level optical sensors (20 cm 3 ) is known. The starting time of fuel consumption, i.e. time when fuel crossed high level sensor and the finish time of fuel consumption, i.e. time when fuel crossed low level sensor gives an estimate of fuel flow rate i.e., 20 cm 3 /difference of time in sec Speed Sensor A non contact PNP sensor ( rpm) is used to measure the engine speed. A PNP sensor gives a pulse output for each revolution of the crankshaft. The frequency of the pulses is converted into voltage output and connected to the computer.

5 Load Cell (Torque Measurement) Torque is measured using a load cell transducer (0-100 kgs). The transducer is strain gauge based. The output of load cell is connected to the load cell transmitter. The output of load cell transmitter is connected to the USB port through interface card Temperature Sensors K-type thermocouples are located at appropriate places to measure the following temperatures. The output of the temperature transmitters is connected to data acquisition card. Combustion peak temperature Inlet water temperature in calorimeter Outlet water temperature in calorimeter Inlet exhaust gas temperature in colorimeter Outlet exhaust gas temperature in colorimeter Inlet water temperature to the engine cylinder Outlet water temperature from the engine cylinder Lube oil temperature Pressure Sensor cylinder pressure. Piezoelectric transducer (water-cooled type) is used to measure

6 Crank Angle Encoder 11 bit 2050 step crank angle encoder (Air-cooled type) is mounted on the cam shaft to measure engine crank angle. The crank angle encoder contains a precision maker disk with a trigger mark and 360 o angle marks which are scanned by a transmission photoelectric cell encased in a dust proof housing. It is powered by a 24V DC power supply and supplies one corresponding analog output between 0 o and 360 o Analog to Digital Converter (ADC) An ADC/data acquisition system (12-bit) captures data about an actual system and stores that information in a format that can be easily retrieved for purposes of engineering or scientific review analysis. Another requirement of a data acquisition system should be that it captures information programmatically or automatically in other words, without any hands-on human intervention or guidance. The seven key functions of the data acquisition systems are follows: Data collection Measurement Trimming and triggering Real time clock System control Data communication Data retrieving All seven elements must be in place for a structure to be considered a data acquisition system. There must be a series of sensors (input channel) to

7 51 a data acquisition board. In addition, there must be a trigger to synchronize the sensors inputs, as well as a control for the data acquisition board. Between data acquisition board and processor of the system and system clock, a data communications bus is also required. While data being stored real-time, the analysis and review of the information is performed after data is gathered. Table 5.1 Engine Specifications Make Kirloskar TV1 Power and Speed 3.5 kw and 1500 rpm Type of engine Single cylinder, DI and 4 Stroke Compression ratio 16.5:1 Bore and Stroke 80 mm and 110 mm Method of loading Eddy current dynamometer Method of starting Manual cranking Method of cooling Water Type of ignition Compression ignition Inlet valve opening before TDC Inlet valve closing after BDC Exhaust valve opening before BDC Exhaust valve closing after TDC Fuel injection timing 23 0 before TDC Nozzle opening pressure 210 bar Lube oil SAE Emission Analyzer Smoke meter as shown in Figure 5.2 is used to measure the intensity of smoke present in the exhaust gas and the specification of the

8 52 smoke meter is given in Table 5.2. Gas analyzer as shown in Figure 5.3 is used to measure the CO, CO 2, HC, NO x and O 2 present in exhaust gas. This analyzer consists of four detectors namely, Non-Dispersive Infrared Detector (NDIR) which detects CO and CO 2 emission, Chemiluminiscence Detector (CLD) which detects NO x emission, Flame Ionization Detector (FID) which detects HC emission and Lambda sensor which senses the O 2. Specification of the gas analyzer is given in Table 5.3. Table 5.2 Smoke meter specifications Model AVL 437 Measuring range opacity in % absorption m min C Accuracy and reproducibility ±1% Full scale reading Max smoke temperature at entrance 250 C Table 5.3 Gas analyzer specifications Type AVL DiGas 444 Measured quality Measuring range CO 0 10 % vol CO % vol HC ppm O 2 NO x 0 22 % vol ppm

9 53 Figure 5.2 Photographic view of smoke meter Figure 5.3 Photographic view of five gas analyzer

10 54 The accuracy of measurement and uncertainities of computed results are listed in Table 5.4. Table 5.4 Accuracy of measurement and uncertainties of computed results Measurements Accuracy NO x ±5 ppm CO ± 5% of indicated value CO 2 ± 5% of indicated value HC ± 1 ppm Smoke ± 1% full scale reading O 2 Temperatures ± 5% of indicated value ± 1 o C Dynamic viscosity ± 1% Calorific value ± 1% Specific gravity ± 1% Computed Results Uncertainty (%) Kinematic viscosity ± 1.3% Brake Power 0.5% BSFC 1.5% Total Fuel flow 1% Brake Thermal efficiency 1% Speed ± 3 rpm 5.4 EXPERIMENTAL PROCEDURE Base Line Testing The flow of air, the level of lubricating oil and the fuel level are checked before starting the engine. The engine is cranked by keeping the decompression lever and the fuel cut off lever of the fuel pump in the ON position.

11 55 When the engine starts, the decompression lever is disengaged and the speed of the engine is increased to 1500 rpm and maintained. The engine is allowed to run for 15 minutes to reach the steady state conditions. The time taken for 20 cm 3 of fuel consumption for every load charge is recorded. Under each load, by the exhaust gas analyzer, CO, CO 2, HC, O 2, NO x, and by smoke meter, intensity of smoke and exhaust gas temperature are measured and recorded. 5.5 EXPERIMENTAL DETAILS There are seven major experiments conducted to predict performance, combustion and emission characteristics of compression ignition engine fueled with Thevetia Peruviana seed oil. To find the suitability and feasibility of METPSO as a fuel in diesel engine the following experiments have been conducted. 1. Experiments on the CI engine fueled with blends and neat METPSO: Engine performance characteristics are the major criterion that governs the suitability of a fuel. The purpose of this study is to investigate the performance and exhaust emissions of various blends of METPSO in the computerized diesel engine and to compare them with that of D100. The METPSO has been blended with D100 in several percentages (20%, 40%, 60% and 80%) and are named as B20, B40, B60 and B80. Next METPSO is also taken up for testing (B100). The acquisition of operating parameters such as performances and emission characteristics, as a function of brake power is

12 56 done, at the engine speed of 1500 rpm. The effect of blends of METPSO on the following parameters have been investigated and discussed in this study. Brake specific fuel consumption Brake thermal efficiency Carbon monoxide Carbon dioxide Unburned hydrocarbon Nitrogen oxide Exhaust smoke Exhaust gas temperature 2. Combustion characteristics of a CI engine fueled with blends and neat METPSO: The following parameters are measured and analyzed with diesel and blend of METPSO with diesel as fuel. Cylinder pressure variation with crank angle and load. Instantaneous heat release rate. Cumulative heat release. Ignition delay. Rate of pressure rise. Combustion duration. 3. Performance and emission studies with other non-edible and edible oil based biodiesel and diesel blends with blend ratios of 20% and 100% and comparison made with that of METPSO: For making comparison of neat METPSO and 20% blend with other non-edible and edible based biodiesel of the same blend level, performance and emission studies were carried out on the same engine. The engine is run at a constant speed of 1500 rpm. Load is changed in eight levels from no load to maximum load

13 57 condition. For better clarity, results are presented and discussed only at no load, part load (1.75 kw) and maximum load (3.5 kw) conditions. MEJO MEPO MEMO MENO MECO MEPaO MECoO MEMuO MESO MERO Non- Edible Oil Edible Oil All the above methyl esters are prepared in our laboratory and properties such as kinematic viscosity, specific gravity, calorific value, flash pint, fire point, cloud point and pour point are found as per the ASTM standards. The properties of above said methyl ester is listed in the Annexure- 1and compared with diesel and METPSO. 4. Experiments to find out the optimum injection timing and optimum injection pressure for neat METPSO: Experiments are conducted at a constant speed of 1500 rpm under variable load conditions with diesel and neat METPSO. Parameters like Injection timing and injector opening pressure are varied incase of neat METPSO to study their influence on performance and emission. Results have been compared with neat diesel operation (23 o btdc and 210 bar). The injection timing is varied (23 o, 25 o 27 o and 29 o btdc) by changing the position of fuel injection pump with respect to the cam. Subsequently, injection pressure is varied (210, 215, 220, 225, 230 and 235 bar) by adjusting the screw of injector.

14 58 5. Experiments with peroxidized biodiesel for further improvement of performance and emission: METPSO obtained from transesterification process is further improved by peroxidation technology. In using this technology, 2% and 4 % (by vol.) of hydrogen peroxide (H 2 O 2 ) is then added with METPSO and stirred in the reactor tank at 60 0 C. The reaction time of this peroxidation process is min. Afterwards, the un-reacted impurities and methanol are removed by a distillation method and peroxidized biodiesel is obtained. Properties of peroxidized biodiesel and neat biodiesel are shown in Table 5.5. Table 5.5 Properties of peroxidized fuel Property METPSO B100(2%P) B100(4%P) ASTM code Calorific value, kj/kg D4809 Specific gravity D445 Viscosity (at 40 0 C)cSt D2217 Cetane number D4737 Flash point, C D92 Fire point, C D92 Cloud point, C D97 Pour point, C D97 Ash content, % D976 Vegetable oil, biodiesel and peroxidized biodiesel are then tested for their performance in a diesel engine and for their emission characteristics. The engine experiments are carried out in the same engine under constant speed at 1500 rpm and varying the engine load. Each experiment is repeated three times to calculate the mean value of the experimental data. Obtained performance and emission parameter are plotted in bar chart.

15 59 6. Performance and emission characteristics studies with different rates of Exhaust Gas Recirculation to reduce the NO x emission: Exhaust gas circulation is an effective method for NO x control. The exhaust gases mainly consist of carbon dioxide and nitrogen and possess high specific heat. When recirculated into the engine inlet, it acts as a heat sink. This process reduces oxygen concentration and peak combustion temperature, which results in reduced NO x. Exhaust gas is tapped from pipe and connected to inlet air flow passage. An EGR control valve is provided in this pipe for EGR control (Figure 5.4). The gas inlet volume is controlled by this valve and directly sent to the inlet manifold without a gas cooler. Sufficient distance for thorough mixing of fresh air and exhaust gas is ensured. Temperature of the mixture (exhaust gas and fresh air) is measured just before its entry into the combustion chamber using a K-type thermocouple. EGR amount is determined using an expression, % of EGR = Mass of air admitted without EGR- Mass of air admitted with EGR Mass of air admitted without EGR The effect of different percentage of EGR on Performance and emission characteristics of same engine fueled with METPSO is studied. All the experiments are conducted at variable engine load condition and a constant speed of 1500 rpm.

16 60 Exhaust Gas ENGINE Mixture of Air and Exhaust Gas EGR Valve Air vessel Air Flow meter Figure 5.4 Exhaust gas recirculation piping 7. Experiments on a Variable Compression Ratio engine to predict the optimum compression ratio of neat methyl ester for METPSO: This experiment is aimed to study the effect of compression ratio on performance and emission characteristics in a separate variable compression ratio diesel engine (2.3 kw). The detailed specification of engine is listed in Table 5.6 and the VCR engine setup photograph is shown in Figure 5.5. Initially, base line experiments are conducted in the VCR engine fueled with diesel for various compression ratios (14.5, 15.3, 16.1, 17.0, 18.1, 19.2 and 20.6) at a constant speed of 1500 rpm and by varying the load in six levels from no load to maximum load. Subsequently, engine is operated with neat METPSO for same condition. The performance and emission characteristics like brake thermal efficiency, brake specific fuel consumption, exhaust gas temperature, CO, CO 2, HC, NO x, O 2 and smoke intensity are measured and compared to that of diesel. From the obtained results, optimum compression ratio is determined for METPSO fuel.

17 61 Figure 5.5 Variable compression ratio diesel engine set up Table 5.6 Specification of the VCR engine Make Kirloskar TV1 Power 2.3 kw Speed 1500 rpm No of cylinder Single cylinder No of stroke Four stroke Type of Engine DI, Naturally aspirated Compression Ratio 14.5:1 to 20.6:1 Bore and Stroke 85 mm and 82 mm Method of loading Eddy current dynamometer Method of starting Manual cranking Method of cooling Water Injection pressure 210 bar Injection timing 23 0 btdc Lube oil SAE 40

18 62 All the readings have been taken after reaching the steady state. Every experiment has been conducted at eight levels of loading from no load to maximum load. But the results have been discussed with three loading conditions only namely; no load, part and maximum load to avoid the graphs from getting clustered. The engine is operated at 1500 rpm for all tests. Special care is taken to maintain steady state condition for every reading. Performance and emission parameters like brake thermal efficiency, brake specific fuel consumption, volumetric efficiency, mechanical efficiency, CO, CO 2, NO x, O 2, HC, smoke intensity and exhaust gas temperature are measured, compared and analyzed.