|Title of Invention||
IMPROVEMENTS RELEATED TO A SIX STROKE DIESEL ENGINE
|Abstract||The concept of multi-stroke engine mainly deals with reduction of fuel consumption by the engine and thereby increasing the mileage per liter of the fuel consumed. In a four stroke engine, the number of rotations per cycle of the crankshaft is two and they are increased to three rotations per cycle in a six stroke engine. Our focus, in this project, is a six stroke diesel engine.|
The Patent Act 1970 (39 of 1970)
& The Patent Rules 2003
DESIGN, FABRICATION AND TESTING OF SIX STROKE SINGLE
CYLINDER DIESEL ENGINE
NAME NATIONALITY ADDRESS
1. S.SAIRAM INDIAN 13/30, Kala Flats,
Giri Street, West Mambalam, Chennai-33.
2. S.BOOPATHY INDIAN 8,Lakshmi Nagar
Mosur Road, Arakkonam, Vellore Dt, Tamil Nadu-631001
5. J.L.RAJA VENKATARAMAN INDIAN New No 29,
Shanmugharayan St, George Town, Chennai - 1.
The following specification particularly describes the nature of this invention and the manner in which it is to be performed
DESCRIPTION: FIELD OF INVENTION:
1.1 INTERNAL COMBUSTION ENGINES:
The purpose of internal combustion engines is to produce mechanical power from the chemical energy contained in the fuel. In these engines, the fuel is burned or oxidized inside the cylinder, which causes the mechanical rotation of the crankshaft, and thus power is transferred. It is a fact that combustion takes place inside the power producing part (cylinder) of these engines that makes their design and operating characteristics fundamentally different from those of other types of engines.
IC engines are mainly classified into two types
1. Spark ignition engines.
2. Compression ignition engines.
1.1.1 PETROL ENGINES:
The engine which gives power to propel the modern automobiles is a spark ignited petrol engine. Here, when the piston moves downward, the homogenous mixture of air and fuel is sucked from the carburetor into the cylinder. During the upward motion, the mixture is compressed by the piston in the cylinder and ignited by an electric spark. When the mixture is burned in the cylinder, the resulting heat causes the gases to expand which exert pressure on the piston and the cylinder walls. The piston being movable is pushed downward by this pressure for the full length of the stroke.
1.1.2 DIESEL ENGINES
The engines of heavy motor vehicles, stationary power plants, big industrial units and ships mostly operate on diesel cycle or constant pressure cycle. Here, when the piston moves downward, only air is sucked into the cylinder. Then as the piston moves upward this air is compressed to a higher pressure and the temperature of this compressed air becomes sufficiently high. Diesel is injected into the cylinder at the end of the compression stroke where auto ignition takes place. There is no spark plug in a diesel engine. Since the fuel inside ignites due to the compression, these engines are classified as compression ignition engines.
BACKGROUND OF INVENTION:
WHY SIX STROKE IN A DIESEL ENGINE
The idea of six stroke engine is only designed for a diesel engine. This is because of the following reasons:
1. Here, the type of combustion is heterogeneous. Hence, the design which involves additional strokes of air compression and expansion can be carried out. This cannot be carried out in a petrol engine which is of a homogenous type. Hence, if the additional stroke involves charge compression and expansion, it may lead to pre- ignition or knocking, which is unsuitable for petrol engines.
2. The compression ratio of a diesel engine is far above than the petrol
engine thus enabling it to convert more of the chemical energy into
work. Since the flywheel has to absorb more energy to supply to the
other idle strokes, diesel engine is best suited.
3. Diesel engine has high thermal efficiency comparatively.
4. Starting torque produced is greater comparatively.
SUMMARY OF INVENTION: METHODOLOGY
The Design has been formulated for a diesel engine. This design of six Stroke single cylinder Diesel Engine is based on the principle that the power produced during the power stroke is distributed to the other five strokes through the flywheel. The Six Strokes are as follows:
• Air Suction
• Air Compression
• Air Expansion
• Power Compression (Diesel Injection)
• Power Expansion
Here the additional strokes are air compression and air expansion. The uses of these strokes are explained in the further chapters.
FIG 1 shows the working of six stroke single diesel engine AIR SUCTION
Fig l(a) shows the Air Suction stroke of this diesel engine. This stroke is similar to the suction stroke of the four-stroke engine. During this stroke, the piston moves from top dead center to the bottom dead center. When it goes down, the inlet valve opens and air enters through the intake manifold into the cylinder. When piston moves down rapidly, a low-pressure region is created inside the cylinder, which sucks the air in to it.
Fig l(b) shows the Air Compression stroke of this diesel engine. This is an additional stroke. Here the piston moves from B.D.C to T.D.C. Due to this movement, the air inside the cylinder gets compressed. But at the end of the compression the fuel is not injected. Only the air gets compressed to a high pressure.
Fig l(c) shows the Air Expansion stroke of this diesel engine. This is the other additional stroke. Here, only the compressed air is allowed to expand by the downward movement of the piston. Hence, we cannot expect power to be produced. But, the energy consumed during this process is comparatively lower than the other idle strokes.
Fig l(d) shows the Power Compression stroke of this diesel engine. This stroke is similar to the second stroke of four-stroke diesel engine. The air inside the cylinder is compressed again. At the end of this stroke, the fuel is injected in to the chamber. The advantage these three strokes are that it causes rapid compression and expansion of the air thus increasing its turbulence and duration of air inside the combustion chamber is high compare to four stroke, cause air to get preheat because of previous combustion. Due to this turbulence and preheating of air, the fuel injected will ignite quickly and the flame dispersion will be quicker. This causes the combustion to be complete and thus reduces the exhaust emissions.
Fig l(e) shows the Power Expansion stroke of this diesel engine. It is similar to the four-stroke cycle engine. The fuel injected at the end of the compression gets burnt and causes the piston to move rapidly downwards and thus rotates the crank. During this stroke, we get the work from the engine. The flywheel mounted on the engine shaft stores the energy produced in this stroke and supplies it to the other remaining strokes. Both the valves remain closed during the start of this stroke but when the piston reaches B.D.C the exhaust valve opens and all the burnt gases are released as shown in Fig l(f).
For designing the six-stroke engine, it is necessary to do three basic modifications on a single cylinder four-stroke dicscl engine. They arc
1. Flywheel modification.
2. Cam modification according to valve timing diagram.
3. Timing gears modification
A flywheel is a heavy rotating body which acts as a reservoir of energy. The energy is stored in the flywheel in the form of kinetic energy. The flywheel acts as an energy bank between the source of power and the driven machinery. This concept of energy storage by a flywheel is utilized in designing a six-stroke engine. In a six-stroke engine, the power is generated in only one stroke. The flywheel absorbs the excess energy developed during the expansion stroke, and delivers it to the other remaining strokes. Fig 2 (a), (b), (c) shows the flywheel used for the six stroke engine. In the six stroke engine the fluctuation of speed is high compare to tour stroke engine. So to reduce the fluctuation of speed it is necessary to increase the mass of the flywheel.
A cam is a device that changes rotary motion of the camshaft into linear motion of the follower or lifter. The cam has high spot or lobe. A camshaft is responsible for opening the valves. It has two cams one to operate the inlet valve and the other the exhaust valve. In addition, the camshaft has an eccentric to operate the fuel pump.
Fig 3 (a) shows the line diagram of the cam shaft and Fig 3(b) shows the manufactured cam shaft for the six stroke engine.
The crankshaft drives the camshaft either by a pair of meshing gears or by means of timing sprockets connected by a chain. The gear ratio between crankshaft and the camshaft is given by,
Gear Rear(G)=Number of rotation of crank shaft
Number of ratationn ofcam shaft
For four stroke engine,
G=720/360=2/l For six stroke engine,
Thus, it can be inferred that for three rotations of crankshaft, the camshaft has to rotate for one revolution. Therefore, the gear pairs are modified in such a way that their transmission ratio is 3:1. The cam design depends upon the valve-timing diagram. The valve timing diagram for the six-stroke engine is designed and the cam is drawn according to that.
TIMING GEARS MODIFICATION
Fig4 shows the timing gears for the 6S engine. The camshaft is driven by the crankshaft through a pair of timing gears. In a four stroke engine, the camshaft gear has twice as many teeth as the crankshaft gear. Thus, for every two revolutions of the crankshaft, the camshaft rotates only once, thus maintaining a gear ratio of 1:2. The gear maintains a definite time relationship between the camshaft and crankshaft and ensures the correct opening of the valves in relation to the piston position. Timing marks on the gears are used to set the shaft in correct time with each other when the units are assembled. These timing marks represent the TDC of the engine.
In this project, for every three rotations of the crankshaft, the camshaft makes only one rotation. Hence, the gear ratio is to be changed from 2:1 to 3:1. Therefore, the number of teeth has to be changed to get a gear ratio of 3:1 without changing the centre distance.
DESIGN OF TIMING GEARS
Fig4 shows the timing gears for the 6S engine.The center distance between the timing gears of the four-stroke engine was calculated. It was found to be around 51 mm. Depending upon this, the number of teeth for the timing gears of the six-stroke engine were calculated using the formula. We know that
M= module (2mm for four stroke)
C= center distance between the shafts (51 mm)
D= pitch circle diameter of camshaft gear (68mm for four stroke)
d = pitch circle diameter of crankshaft gear (34mm for four stroke)
T = Number of teeth in cam shaft (34 teeth for four stroke)
t = Number of teeth in crank shaft (17 teeth for four stroke)
Using the above formula, the gear dimensions for the six-stroke engine was calculated
The gears for six-stroke engine must be designed in such a way that the center distance between the shafts should be constant and the gear ratio must be 3:1. To get the gear ratio of 3:1 and also to maintain the same center distance, the timing gears must have
D= 76.5mm T=51
d= 25.5mm t=17
This has to be calculated by iteration. Thus, the camshaft gear must have 51 teeth and crankshaft gear must have 17 teeth.
DESIGN OF CAM AND CAMSHAFT
Since timing and speed ratio of camshaft for six-stroke engine differs from the normal four-stroke engine's camshaft, it is necessary to design a new camshaft. The camshaft usually rotates only once for every cycle of the engine. During this one rotation, the inlet cam has to open the inlet valve, the exhaust cam has to open the exhaust valve and the fuel cam has to lift the plunger of the fuel pump at the correct time. This timing is usually represented as angles in designing the cam. For this purpose, the valve-timing diagram for the six-stroke engine is drawn. Depending upon this, the cams are designed.
Fig 3 (a) shows the line diagram of the cam shaft and Fig 3(b) shows the manufactured cam shaft for the six stroke engine.
The cam design involves several inputs. The design of the cam mainly depends on the time (angle) to which the valves have to operate. The valve-timing diagram usually represents this angle. First, the valve-timing diagram
of the four-stroke engine is taken. Using this, the valve-timing diagram of the six-stroke engine is designed.
Using the Valve timing diagram of the six stroke engine, we predicted the angle for Opening Dwell and Closing for the inlet, exhaust and fuel cam.
TABLE 1: Represent the Angle Specification for Inlet Cam. TABLE 2: Represent the Angle Specification for Exhaust Cam. TABLE 3: Represent the Angle Specification for Fuel Cam.
By keeping this angle as a reference we draw the cam profile for the Inlet, Exhaust and Fuel cam.
Fig 6 shows the cam profile of the Inlet cam for six stroke diesel engine Fig 7 shows the cam profile of the Exhaust cam for six stroke diesel engine Fig 8 shows the cam profile of the Fuel cam for six stroke diesel engine
As already mentioned, the amount of energy stored by the flywheel can be varied by varying its mass or its radius. Generally, if mass is varied then it has to be in such a wav that it is concentrated on the flywheel's rim. This may cause additional stress on the crankshaft and may also result in a balancing problem. But, the effect can be nullified by varying the cross section of the crankshaft and adding additional weights at the crank webs. This may not be a serious problem because the power developed is lesser than the four stroke engine and hence the crankshaft will rotate at lesser speed comparatively. So, the centrifugal force acting on the crankshaft is minimized.
In our engine
Mass of the flywheel - 9.186 kg
Radius of flywheel - 12 cm
In normal tour stroke engine by calculating the rated power, rated speed from the compression ratio and stroke length to bore ratio, the flywheel is designed. But we followed the reverse engineering technique, in which the mass of the flywheel is increased up to 14.5kg (lObp engine's flywheel) to reduce the fluctuation of speed as mentioned before, from this data the power developed in the six stroke engine may be calculated.
BRIEF DESCRIPTION OF DRAWINGS:
FIG 1: WORKING OF SIX STROKE SINGLE CYLINDER DIESEL ENGINE
PARTI: INLET VALVE PART 2: EXHAUST VALVE PART 3: FUEL INJECTOR
FIG la: SUCTION
FIG l.b: AIR COMPRESSION
FIG l.c: AIR EXPANSION
FIG Id: POWER COMPRESSION
FIG I.e. POWER EXPANSION
FIG If: EXHAUST
FIG 2: FLYWHEEL
FIG 3: DIMENSIONS OF CAMSHAFT FOR SIX STROKE ENGINE
PARTI: INLET CAM
PART 2: EXHAUST CAM
PART 3: FUEL CAM
PART 4: TIMING GEAR (51 TEETH)
FIG 4: TIMING GEARS FOR SIX STROKE ENGINE
PART 1: CAM SHAFT GEAR PART 2: CRANK SHAFT GEAR
FIG 5: VALVE TIMING DIAGRAM FOR SIX STROKE ENGINE
AC- AIR COMPRESSION
AE- AIR EXPANSION
PC- POWER COMPRESSION
PE- POWER EXPANSION
IVO- INI ,FT VAI ,VE OPEN IVC- INLET VALVE CLOSE RVO- FXAUST VALVE OPEN EVC- EXAUST VALVE CLOSE FVO- FUEL VALUE OPEN FVC- FUEL VALVE CLOSE
FIG 6: INLET CAM FIG 7: EXAUST CAM FIG 8: FUEL CAM
LIST OF TABLES
TABLE 1: ANGLE SPECIFICATION TABLE FOR INLET CAM TABLE 2: ANGLE SPECIFICATION TABLE FOR EXHAUST CAM TABLE 3: ANGIM SPECIFICATION TABLE FOR FUFI, CAM
LIST OF ABBREVIATIONS
TDC: Ton Dead Centre BDC: Bottom Dead Centre ICE; Internal Combustion Engine HSU: Hatridge smoke unit
|Indian Patent Application Number||829/CHE/2006|
|PG Journal Number||12/2009|
|Date of Filing||10-May-2006|
|Name of Patentee||S. SAIRAM|
|Applicant Address||OLD NO. 13/30, KALA FLATS, GIRI ST. WEST MAMBALAM, CHENNAI - 600 033,|
|PCT International Classification Number||F02B75/02|
|PCT International Application Number||N/A|
|PCT International Filing date|