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81 CHAPTER 6 EXPERIMENTAL APPARATUS AND PROCEDURES 6.1 INTRODUCTION This chapter describes the about the experimental setup used for conducting experiments, procedures, specification of the engine and the measurement devices employed are clearly presented. 6.2 EXPERIMENTAL APPARATUS 6.2.1 Engine Test Setup The schematic diagram of the experimental setup is shown in Fig. 6.1. It consists of single cylinder, four stroke diesel engines with data acquisition system. It has eddy current dynamometer for loading. The setup is provided with necessary instruments for combustion pressure and crank-angle measurements. The Kistler piezoelectric air-cooled pressure transducer and 360 pulse count (ppr) crank angle encoder which measure the combustion pressure and the corresponding crank angle, respectively, are mounted on the engine cylinder head. The pressure transmitter type 6613CA contains a piezoelectric sensor and an integrated charge amplifier. These signals are interfaced to a computer through engine indicator for pressure-volume diagrams. Provision is also made for interfacing airflow, fuel flow, temperatures, and load measurement. The setup has a stand-alone panel box consisting of two fuel tanks for multi-fuel test, manometer reading, fuel measuring unit, transmitters for air and fuel flow measurements, process 82 indicator, and engine indicator. Rota meters are provided for measurement of engine cooling water and calorimeter cooling water. The setup enables the study of diesel engine performances and combustion parameters. Lab viewbased engine performance analysis software package "Engine test expresses V5.75" provides for online performance evaluation. A computerized cylinder in line pressure measurement is provided to measure the combustion pressure (Muralidharan and Vasudevan, 2011). Figure 6.1 Schematic diagram of the experimental setup 6.2.2 Variable Compression Ratio Conventional gasoline engines operate at fixed compression a ratio, which is set low enough to prevent premature ignition of the fuel, or “knock,” at high power levels under fast accelerations, high speeds, or heavy loads. Most of the time, the gasoline engine operates at relatively low power levels under slow accelerations, lower speed and light loads. If the compression ratios are increased at low-power operation, gasoline engines could achieve higher fuel efficiency (Kumaran et al. 2011). 83 Figure 6.2 Compression ratios changing lever for VCR engine setup Variable compression ratios are the technology to adjust internal combustion engine cylinder head so that the volume of a cylinder is increased. Figure 6.2 shows the compression ratio changing lever. In this setup the compression ratios can be varied from 7:1 to 20:1 and the maximum cylinder head varies from 0 to 21mm. This is done to increase fuel efficiency while varying the loads. Higher loads require lower ratios be more efficient and vice-versa. Variable compression ratio engines allow for the volume above the piston at 'Top dead centre' to be changed. For automotive use, this needs to be done dynamically in response to the load and driving demands. The compression ratios are varied by changing the clearance volume. As the bore and the head of the engine is raised and lowered, the clearance volume is changed, resulting in the change in the compression ratios. As a result, volumetric efficiency improves, which brings about better combustion. 84 6.2.3 Engine Specification The engine setup details and load ranges of VCR engine is given in Table 6.1. Also, the specification of the variable compression ratio engine shows this table. Table 6.1, The specification of the variable compression ratio engine Type No. of strokes Rated Power Kirloskar, single cylinder, inline, vertical, water cooling Four 3.7 kW Bore/Stroke Rated RPM Compression ratio Injection timing Type of ignition 80mm/110mm 1500 7:1 to 20:1 23 º before top dead center Compression ignition Method of loading Eddy current dynamometer Type Load measurement method Ranges Power Mag Strain gauge 0-50kgs Cooling Max. Speed Air cooling 3000 rev. /min. Direct Coupling type Method of starting Manual crank start Injection opening pressure Method of water flow measurement 200 bar (std.) Combustion pressure measurements Type - Acrylic body rotameter Ranges - 40-400 lph for engine cooling 10-100 lph for calorimeter cooling Make - Kistler Model - Piezoelectric Range of pressure sensor - 0-100 bar 85 6.3 MEASUREMENT DEVICES FOR ENGINE SETUP The following measurement devices are used in the engine setup. 6.3.1 Air Flow Rate Measurement Method Differential pressure sensor is used to measure the pressure difference between the orifice plates. The differential pressure sensor gives a proportional output with respect to the difference in pressure. The range of this equipment is 0-99 m3/hr. 6.3.2 Fuel Flow Rate Measurement Method In the engine tests, fuel consumption is measured as a mass flow per unit time and it is denoted by mf. The more useful parameter of fuel flow measurement is specific fuel consumption. The fuel consumption is measured by using optical sensors. The optical sensors are capable of detecting any liquid and give an output in the form of signal. The system consists of two burette fitted with two optical sensors, one at the high level and another at the low level. As the liquid passes through the high level optical sensor, the sensor gives a signal to the computer to start the time. Once the liquid reaches the lower level optical sensor, the sensor gives a signal to the computer to stop the time and refill the burette. The time taken in the consumption of fuel for a fixed volume is calculated. Also, the range of fuel flow measurement sensor is based on the engine specification. 86 6.3.3 Speed Measurement Method A non-contact PNP sensor is used to measure the engine rpm. APNP sensor gives a pulse output for each revolution of the crankshaft. The frequency of pulses is converted into voltage output and connected to the computer. The range of speed measurement sensor is 0-9999 rpm. 6.3.4 Water Flow Measurement Method Acrylic body rotameter is used to measure the water flow measurement method. Here, two types of rotameter are used for engine cooling and calorimeter cooling. The range of engine cooling is 40-400 lph and the range of calorimeter cooling is 10-100 lph. 6.3.5 Torque or Load Measurement Method The range of load measurement is 0-50 kg and method of loading is eddy current dynamometer. Torque is measured using load cell transducer. The transducer has a strain gauge base. The output of the load cell is connected to the load cell transmitter. The output of the load cell transmitter is connected to the UBS port through interface card. 6.3.6 Measurement of Temperature at Different Points The temperature is measured at seven different points in the VCR engine setup. All are ‘K’ type thermometers. The thermometer is placed at different locations and temperature is measured, thus for calorimeter water inlet and outlet temperature, the range of this temperature is 300 ºC. For exhaust gas inlet and outlet temperature, the range of this temperature is 0-1500 ºC. For engine cooling water inlet and outlet temperature, the range of 87 this temperature is 0-300 ºC. Ambient air temperature and range of the temperature is 0-300 ºC. All the measured parameters from the sensor are connected to the computer. 6.3.7 Cylinder Pressure Measurement It consists of very precise and robust pressure sensor with an in-line charge amplifier for combustion pressure measurement application. The sensor will have almost an unlimited lifetime for combustion pressure measurement application. Optimized piezoelectric sensor for continuous cylinder pressure monitoring of engines sensor measurement is used. The sensor is connected to the charge amplifier with a robust integrated high temperature Viton cable. The good linearity and repeatable measurements are recorded over a long period of time. The sealing takes place at the shoulder of adapter that requires a flat and smooth machined sealing area. The charge amplifier accepts a power supply between 7-32 VCD and has a range of 0-100 bar (40mV/ brand works with a time constant of 5 s). 6.3.8 Measurement of Crank Angle Encoder The crank angle encoder contains a precision marker disk with a trigger mark and 360 angle marks which are scanned by a transmission photoelectric cell. The disk and the photoelectric cell are encased in a dustproof housing. It is powered by a 24 VDC power supply and supplies one corresponding analog output between 0 and n dash; 360 degrees. 88 Table 6.2, The details of crank angle encoder Supply 24V DC (Regulated ± 15%) Output 0 –8V Resolution 2048 Steps (11-Bit) Max Loop Resistance Body Machined Aluminum body with anodized finish Shaft Mounting 6.3.9 Stainless steel (SS-304) of 10mm dia x 22mm Length Servo/Face is mounted with 3 screws of the M4, 120 degrees apart on a PCD of 50,60mm dia Measurement of Analog Input / Output The data acquisition card has 14 external analog inputs. AIN0- AIN3 are available on screw terminals and also on the DN37 connector. All 14 analog inputs are available on the DB37 connector. Each analog input can be configured individually as unipolar or bipolar. Analog input resolution is 12 bits at maximum speed, increasing up to 16 bits at slower speeds (2.7 ms conversion time) Commands/response analog input reads typically take 1.2+ms depending on number of channels and communication configurations. Hardware timed input streaming has a maximum rate that varies with resolution from 250 samples/s at 16 bit to 50+ K samples/s at 12 bits. The data acquisition card has two analog outputs (DAC0 and DAC1) that are available both are screw terminals and the DB37 connector. Each analog output can be set to a voltage between 0 to 4.9 volts with 12 bits 89 of resolution. The analog outputs are based on true voltage reference. The analog outputs are updated in command/ response mode, with a typical update time of 1.2-4.0 ms depending on communications configurations. 6.3.10 Measurement of Digital Input / Output The data acquisition card has 23 input/output channels which can be individually configured as input, output-high, or output low. Eight of these lines, called flexible digital I/O (FIO) and can be software-configured as up to 6 times to two counters. The first four FIO available are screw terminals and the DB37 connector. All 8 FIO and 3 MIO are available on the DB37 connector, and 8 EIO and 3 CIO are available on the DB37 connector. The command/response reads/writes typically take 1.2 – 4.0 ms depending on communication configurations. The digital inputs can also be read in a hardware timed input stream where up to 16 inputs count as a single stream channel. 6.4 EXHAUST GAS EMISSIONS MEASUREMENT SETUP 6.4.1 Measurements of Five Gas Analyzer As shown in Fig. 6.3, A Multi-gas analyzer (NETEL make, NPM- MGA-2 model) was used for measuring the exhaust gas emissions. The probe of the analyzer is inserted into the exhaust pipe of the engine before taking the measurements. After the engine is stabilized in working condition, the exhaust emissions are measured. Using this analyzer, carbon-monoxide (CO), hydrocarbon (HC), carbon-dioxide (CO2), nitrogen oxide (NOx) and oxygen (O2) have been measured for different types of biodiesels, pre-heated palm oil 90 blends and standard diesel for different compression ratios. The emission results of all test fuels are within the acceptable limits. The various Indian standards used for emission analysis are given in Table 6.3. Also, Table 6.4 shows the make, model, range, and resolution of the exhaust gas emissions. Table 6.3 The various Indian standards used for emission analysis Elements Indian Standard Carbon-dioxide IS 13270:1992 (reaffirmed 1999) Carbon-monoxide IS 11293:1992 Hydrocarbon --- Nitrogen oxides IS 11255 – (PART 7) – 2005 Table 6.4 The make, model, range and resolution of the exhaust gas emissions analyzer Gas analyzer Make NETEL Gas analyzer Model NPM-MGA-2 Emissions Range Resolution CO 0-10 % 0.01% CO2 0-20 % 0.1% HC 0-2000 ppm 1 ppm O2 0-25% 0.01% NOx 0-10000 ppm 1 ppm 91 Figure 6.3 Exhaust gas analyzer used in VCR engine Figure 6.4 View for exhaust emission measurement 6.4.2 Measurement of Smoke Also, the smoke emission from the test engine was measured in this study. In order to measure smoke emission, an opacity type smoke meter was used. The exhaust gas pipe from the test engine was connected to the smoke meter and then smoke emission results were recorded. The smoke meter specification is as shown in Table 6.5. 92 Table 6.5 Smoke meter specifications Model MEXA-130S(Horiba Co., Ltd) Measuring component Smoke from diesel engine Measuring principle Opacity method Measurement ranges Opacity 0-100% K value 0-10.00 1/m Sampling method Partial flow Input/output Digital Power source AC100 V 50/60 Hz 6.5 EXPERIMENTAL PROCEDURES The variable compression ratio engine setup is shown in figure 6.5. The engine is started by using diesel. The engine reaches the stable operating conditions when applied with part- and full-load. To cool the engine socket, water is used as cooling medium and the flow rate is maintained as 90 ml/s and the cooling water temperature is stabilized at 40º C. The tests are conducted at the rate of constant speed of 1500 rpm. In every test, all the performance and combustion parameters are measured. From the initial measurement, specific fuel consumption and brake thermal efficiency with respect to compression ratios 17:1, 18:1, and 19:1 for different blends are calculated and recorded. The combustion and emission levels are also processed and stored in computers for further processing of the results. The same procedure is repeated for all the tested fuels. Table 6.6 shows the accuracy of the measurements and the uncertainty of the calculated results of various parameters. 93 Figure 6.5 Experimental setup for computerized variable compression ratio engine test rig Table 6.6 The accuracy of the measurements and the uncertainty of the calculated results Measurements Accuracy Engine speed ± 30 rpm Temperatures ± 1ºC Carbon-monoxide ± 0.03 % Hydrocarbon ± 10 ppm Carbon-dioxide ± 0.04% Time ± 0.5% Calculated results Uncertainty Power ± 2.2% Specific fuel consumption ± 2.2% Crank angle encoder ± 0.5º CA 94 6.6 SUMMARY The selected biodiesels and pre-heated oil is tested and the following conclusions can be drawn Engine test experiments were conducted on a DI diesel engine by fueling these four kinds of methyl ester fuels, pre-heated palm oil and PBDF. 1. The specifications of test engine, equipment and measurement devices are discussed in this chapter. Also, the detailed explanation of experimental procedure and, range and accuracy of equipment are expressed. 2. Also, the detailed specification of exhaust gas emission analyzer and smoke meter are expressed in this chapter.