Chapter-4 EXPERIMENTAL SETUP. A single cylinder Kirlosker made direct injection diesel engine was

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1 PDFaid.com Chapter-4 EXPERIMENTAL SETUP A single cylinder Kirlosker made direct injection diesel engine was chosen to carry out the experiments. This engine was modified to SI engine by incorporating spark plug, ignition system and timing. The experimental investigations have been performed in two stages. In the first stage pure methanol is used separately in the single cylinder CI modified SI engine. In the second stage, methanol blends with gasoline are used to ascertain the performance. The above engine is one of the extensively used engine in agricultural and industrial sectors in India. This engine could withstand the peak pressures encountered because of its original high compression ratio. Further, the necessary modifications on the cylinder head and piston crown could easily be carried out in this type of engine. Hence this engine is selected for the present research work. The combustion of lean mixtures can reduce fuel consumption and NOx emissions in spark-ignition engines and mixture stratification has been used to extend the lean limit of automobile engines, as demonstrated. In addition, the

2 mixture concentration in the spark plug vicinity at the time of ignition has been shown to affect flame kernel development and cyclic variability. Stratification can be achieved by port injection usually with open valves and swirl or tumble, by use of a pre-chamber to create a 'torch' jet into the lean mixture, by direct in-cylinder fuel injection, where air/fuel ratios exceeding 40 have been reported Kume et al. and by combinations of port and direct injection. Port injection alone has not allowed extension of the lean limit to air-fuel ratios higher than around 25 and, although even higher values are likely to be achieved, it is unlikely to achieve the higher values associated with direct fuel injection. On the other hand, the success of direct injection has required late injection with impingement on a specially-shaped piston crown and with particularly careful metering of the fuel supply and its relationship to port-induced air flow. In the quest for increased efficiency and reduced exhaust emissions, Internal Combustion (IC) engine combustion technology appears to be converging. Engine development is moving ahead in some cases by deliberately selecting the best features found in HCCI engines, direct-injection engines, and lean-burn homogeneous charge engines. In fact, automotive engines of the future may spend part of their time operating in each of these modes, depending on the particular speed and load conditions, and the emission requirements. This section describes the development of a PSC engine combustion concept, as described its aimed at extending the lean limit of spark-ignition engines in order to reduce NOx emissions and increase part-load thermal efficiency. Lean-burn

3 natural gas engines offer higher efficiency and lower NOx than stoichiometric natural gas engines, and much lower particulate emissions than diesel engines. To a certain extent, a lean strategy allows control of the engine load without throttling by changing the air/fuel ratio. The prior section described the concept of increasing turbulence locally to extend lean operation, and this section describes the approach of locally en-richening the mixture to establish a robust flame initiation. The water brake absorber is sometimes mistakenly called a "hydraulic dynamometer." Water brake absorbers are relatively common, having been manufactured for many years and noted for their high power capability, small package, light weight, and relatively low manufacturing cost as compared to other, quicker reacting "power absorber" types. Their drawbacks are that they can take a relatively long period of time to "stabilize" their load amount and the fact that they require a constant supply of water to the "water brake housing" for cooling. In many parts of the country where, environmental regulations now prohibit "flow through" water and large water tanks must be installed to prevent contaminated water from entering the environment. The schematic shows the most common type of water brake, the variable level type. Water is added until the engine is held at a steady RPM against the load. Water is then kept at that level and replaced by constant draining and

4 refilling, which is needed to carry away the heat created by absorbing the horsepower. The housing attempts to rotate in response to the torque produced but is restrained by the scale or torque metering cell that measures the torque. Fig4.1: This schematic shows a water brake, which is actually a fluid coupling with a housing restrained from rotating - similar to a water pump with no outlet. 4.1 Components for Mixture Formation A mechanically controlled variable venture carburetor with a metering rod, is employed which has the provision for independent fuel control. Jets of large size are used for alcohols Carburettor

5 The carburetor works on Bernoulli's principle: the faster air moves, the lower its static pressure, and the higher its dynamic pressure. The throttle (accelerator) linkage does not directly control the flow of liquid fuel. Instead, it actuates carburetor mechanisms which meter the flow of air being pulled into the engine. The speed of this flow, and therefore its pressure, determines the amount of fuel drawn into the air stream. Fig4.2: Cross Sectional schematic of a Carburetor

6 When carburetors are used in aircraft with piston engines, special designs and features are needed to prevent fuel starvation during inverted flight. Later engines used an early form of fuel injection known as a pressure carburetor. Most production carbureted (as opposed to fuel-injected) engines have a single carburetor and a matching intake manifolds that divides and transports the air fuel mixture to the intake valves, though some engines (like motorcycle engines) use multiple carburetors on split heads. Multiple carburetor engines were also common enhancements for modifying engines in America from the 1950s to mid-1960s, as well as during the following decade of high-performance American muscle cars fueling different chambers of the engines intake manifold. Older engines used updraft carburetors, where the air enters from below the carburetor and exits through the top. This had the advantage of never "flooding" the engine, as any liquid fuel droplets would fall out of the carburetor instead of into the intake manifold; it also lent itself to use of an oil bath air cleaner, where a pool of oil below a mesh element below the carburetor is sucked up into the mesh and the air is drawn through the oil-covered mesh; this was an effective system in a time when paper air filters did not exist. Beginning in the late 1930s, downdraft carburetors were the most popular type for automotive use in the United States. In Europe, the side draft carburetors replaced downdraft as free space in the engine bay decreased and

7 the use of the SU-type carburetor (and similar units from other manufacturers) increased. Some small propeller-driven aircraft engines still use the updraft carburetor design. Outboard motor carburetors are typically side draft, because they must be stacked one on top of the other in order to feed the cylinders in a vertically-oriented cylinder block. Fig4.3: Carburettor and its maj Spark Plug In the case of transistorize d contact-less high energy ignition system an extended electrode is used. As it is located on the center of the combustion chamber with deep penetration into the chamber, a cooling jacket has been provided around the plug to avoid the plug tip becoming red hot and

8 pre-igniting the mixture. A gap of 0.75 mm for conventional plug and 0.5mm for extended electrode plug are used. The plug is connected to the high voltage generated by an ignition coil or magneto. As the electrons flow from the coil, a voltage difference develops between the central electrode and side electrode. current can flow because the fuel and air in the gap is an insulator, but as the voltage rises further, it begins to change the structure of the gases between the electrodes. Once the voltage exceeds the dielectric strength of the gases, the gases become ionized. The ionized gas becomes a conductor and allows electrons to flow across the gap. Spark plugs usually require voltage of 12,000 25,000 volts or more to 'fire' properly, although it can go up to 45,000 volts. They supply higher current during the discharge process resulting in a hotter and longer-duration spark.

9 Fig4.4: Spark plug As the current of electrons surges across the gap, it raises the temperature of the spark channel to 60,000 K. The intense heat in the spark channel causes the ionized gas to expand very quickly, like a small explosion. This is the "click" heard when observing a spark, similar to lightning and thunder. The heat and pressure force the gases to react with each other, and at the end of the spark event there should be a small ball of fire in the spark gap as the gases burn on their own. The size of this fireball or kernel depends on the exact composition of the mixture between the electrodes and the level of combustion

10 chamber turbulence at the time of the spark. A small kernel will make the engine run as though the ignition timing was retarded and a large one as though the timing was advanced. 4.2 Data Acquisition Nl USB Bit, 10 ks/s Low-Cost Multifunction DAQ 8 analog inputs (12-bit, 10 ks/s) 2 analog outputs (12-bit, 150 S/s); 12 digital I/O; 32-bit counter Bus-powered for high mobility; built-in signal connectivity OEM version available Compatible with Lab VIEW, Lab Windows/CVI, and Measurement Studio for Visual Studio.NET NI-DAQmx driver software and Nl Lab VIEW Signal Express LE interactive data-logging software

11 The National Instruments USB-6008 provides basic data acquisition functionality for applications such as simple data logging, portable measurements, and academic lab experiments. It is affordable for student use, but powerful enough for more sophisticated measurement applications. Use the Nl USB-6008 with the included ready-to-run data logger software to begin taking basic measurements in minutes, or program it using Lab VIEW or C and the included NI-DAQmx Base measurement services software for a custom measurement system. To supplement simulation, measurement, and automation theory courses with practical experiments, Nl developed a USB-6008 Student Kit that includes a copy of the Lab VIEW Student Edition. These kits are exclusively for students, giving them a powerful, low-cost, hands-on learning tool. Visit the Nl academic products page for more details. For faster sampling, more accurate measurements, and higher channel count, consider the Nl USB-6210 and Nl USB-6211 high-performance USB data acquisition devices. Every USB data acquisition module includes a copy of Nl Lab VIEW Signal Express LE so you can quickly acquire, analyze and present data without programming. In addition to Lab VIEW Signal Express, USB data acquisition devices are compatible with the following versions (or later) of Nl application software - Lab VIEW 7.x, Lab Windows /CVI 7.x, or Measurement Studio

12 7.x. USB data acquisition modules are also compatible with Visual Studio.NET, C/C++, and Visual Basic Specifications Product Name Product Family Form Factor USB-6008 Multifunction Data Acquisition USB Operating System/Target Windows, Linux, Mac OS, Pocket PC DAQ Product Family Measurement Type RoHS Compliant B Series Voltage Yes Analog Input Channels 8, 4 Single-Ended Channels 8 Differential Channels 4 Resolution Sample Rate Throughput Max Voltage Maximum Voltage Range 12 bits 10 ks/s 10 ks/s 10 V -10 V, 10 V

13 Maximum Voltage Range 138 mv Accuracy Minimum Voltage Range Minimum Voltage Range -1 V, 1 V 37.5 mv Accuracy Number of Ranges 8 Simultaneous Sampling On-Board Memory 512 B Analog Output Channels 2 Resolution Max Voltage Maximum Voltage Range Maximum Voltage Range 12 bits 5 V 0 V, 5 V 7 mv Accuracy Minimum Voltage Range Minimum Voltage Range 0 V, 5 V 7 mv Accuracy Update Rate Current Drive Single Current Drive All 150 S/s 5 ma 10 ma

14 Digital I/ Bidirectional Channels 12 Input-Only Channels 0 Output-Only Channels 0 Number of Channels 12,0,0 Timing Logic Levels Input Current Flow Output Current Flow Programmable Input Filters Software TTL Sinking, Sourcing Sinking, Sourcing Supports Programmable Power-Up States? Current Drive Single Current Drive All Watchdog Timer Supports Handshaking I/O? Supports Pattern I/O? Maximum Input Range Maximum Output Range 8.5 ma 102 ma 0 V, 5 V 0 V, 5 V Counter/Timer Counter 1

15 Buffered Operations Debouncing/Glitch Removal GPS Synchronization Maximum Range Max Source Frequency Minimum Input Pulse Width Pulse Generation Resolution Timebase Stability Logic Levels 0 V, 5 V 5 MHz 100 ns 32 bits 50 ppm TTL Physical Specifications Length Width Height I/O Connector 8.51 cm 8.18 cm 2.31 cm Screw terminals 4.4 Software Pressure signals were recorded through the NI USB DAQ using Lab view 8.5 signal express. 4.5 Exhaust Gas Analyzer

16 All the emission measurements are on dry basis. The following instruments are used. A non-dispersive infra-red gas analyzer is used to measure CO and HC emissions. Cold traps are provided to prevent moisture from entering the exhaust gas analyzer. 4.6 General Working of the setup Top Dead center signal is obtained by using an inductive pickup close to a disc mounted on the engine cam shaft extension. Metallic protrusion is made on the disc corresponding to the TDC mark. The data recording is triggered by the inductive pickup from the high tension lead to the spark plug. The inductive pickup is attenuated appropriately to a level compatible with the recording instrument. A high resistance suppressor is employed on the high tension lead near the spark plug to avoid any interference problem to the electronic circuit of the instrumentation. The triggering pulse and TDC are helpful in determining the spark timing accurately with the aid of a computer. 4.7 Engine specifications. of cylinders one Bore 80.0 mm Stroke V disp mm cc Rated output 3.68 kw (5.0 hp)

17 Connecting rod length mm Compression ratio 12 Exhaust valve opens at 340 Exhaust valve closes at 554 Inlet valve opens at 527 Inlet valve closes at 750 Spark advance 27 BTDC Speed 1500 rpm

18 Fig.4.5 Single cylinder Kirlosker engine

19 Fig4.6: Arrangement of ignition coil and magnet on the engine Fig4.7: Modified Piston Fig4.8: Cylinder Head