i-VTEC ENGINE

Abstract

The most important challenge facing car manufacturers today is to offer vehicles that deliver excellent fuel efficiency and superb performance while maintaining cleaner emissions and driving comfort. This paper deals with i-VTEC(intelligent-Variable valve Timing and lift Electronic Control) engine technology which is one of the advanced technology in the IC engine. i-VTEC is the new trend in Honda’s latest large capacity four cylinder petrol engine family. The name is derived from ‘intelligent’ combustion control technologies that match outstanding fuel economy, cleaner emissions and reduced weight with high output and greatly improved torque characteristics in all speed range. The design cleverly combines the highly renowned VTEC system - which varies the timing and amount of lift of the valves - with Variable Timing Control. VTC is able to advance and retard inlet valve opening by altering the phasing of the inlet camshaft to best match the engine load at any given moment. The two systems work in concern under the close control of the engine management system delivering improved cylinder charging and combustion efficiency, reduced intake resistance, and improved exhaust gas recirculation among the benefits. i-VTEC technology offers tremendous flexibility since it is able to fully maximize engine potential over its complete range of operation. In short Honda's i-VTEC technology gives us the best in vehicle performance.

1.         RECENT ADVANCES IN AUTOMOBILE ENGINES

q  Common Rail Diesel Injection System(CRDI)

q  Direct Injection System(DI-System)

q  Multi Point Fuel Injection(MPFI)

q  Digital Twin Spark Injection(DTS-I)

q  Quantum Core Engine

q  16 Valve Engine

q  Programmed Electronic Fuel Injection(PGM-FI)

q  Six Stroke Engine

2.      INTRODUCTION:-

An internal combustion is defined as an engine in which the chemical energy of the fuel is released inside the engine and used directly for mechanical work.  The internal combustion engine was first conceived and developed in the late 1800’s.  The man who is considered the inventor of the modern IC engine and the founder of the industry is Nikolaus Otto (1832-1891).

                Over a century has elapsed since the discovery of IC engines.  Excluding a few development of rotary combustion engine the IC engines has still retained its basic anatomy.  As our knowledge of engine processes has increased, these engines have continued to develop on a scientific basis.  The present day engines have advances to satisfy the strict environmental constraints and fuel economy standards in addition to meeting in competitiveness of the world market. With the availability of sophisticated computer and electronic, instrumentation have added new refinement to the engine design.

                From the past few decades, automobile industry has implemented many advance technologies to improve the efficiency and fuel economy of the vehicle and i-VTEC engine introduced by Honda in its 2002 Acura RSX Type S is one of such recent trend in automobile industry.     

q  i-VTEC:-

                The latest and most sophisticated VTEC development is i-VTEC ("intelligent" VTEC), which combines features of all the various previous VTEC systems for even greater power band width and cleaner emissions. With the latest i-VTEC setup, at low rpm the timing of the intake valves is now staggered and their lift is asymmetric, which creates a swirl effect within the combustion chambers. At high rpm, the VTEC transitions as previously into a high-lift, long-duration cam profile.

            The i-VTEC system utilizes Honda's proprietary VTEC system and adds VTC (Variable Timing Control), which allows for dynamic/continuous intake valve timing and overlap control.

The demanding aspects of fuel economy, ample torque, and clean emissions can all be controlled and provided at a higher level with VTEC (intake valve timing and lift control) and VTC (valve overlap control) combined.

The i stands for intelligent: i-VTEC is intelligent-VTEC. Honda introduced many new innovations in i-VTEC, but the most significant one is the addition of a variable valve opening overlap mechanism to the VTEC system. Named VTC for Variable Timing Control, the current (initial) implementation is on the intake camshaft and allows the valve opening overlap between the intake and exhaust valves to be continuously varied during engine operation. This allows for a further refinement to the power delivery characteristics of VTEC, permitting fine-tuning of the mid-band power delivery of the engine.

q  VTEC ENGINE:

VTEC (standing for Variable valve Timing and lift Electronic Control) does Honda Motor Co., Ltd. develop a system. The principle of the VTEC system is to optimize the amount of air-fuel charge entering, and the amount of exhaust gas leaving, the cylinders over the complete range of engine speed to provide good top-end output together with low and mid-range flexibility.

 VTEC system is a simple and fairly elegant method of endowing the engine with multiple camshaft profiles optimized for low and high RPM operations. Instead of only one cam lobe actuating each valve, there are two - one optimized for low RPM smoothness and one to maximize high RPM power output. Switching between the two cam lobes is controlled by the engine's management computer. As the engine speed is increased, more air/fuel mixture needs to be "inhaled" and "exhaled" by the engine. Thus to sustain high engine speeds, the intake and exhaust valves needs to open nice and wide.As engine RPM increases, a locking pin is pushed by oil pressure to bind the high RPM cam follower for operation. From this point on, the valve opens and closes according to the high-speed profile, which opens the valve further and for a longer time.

q  BASIC V-TEC MECHANISM                                    

                The basic mechanism used by the VTEC technology is a simple hydraulically actuated pin. This pin is hydraulically pushed horizontally to link up adjacent rocker arms. A spring mechanism is used to return the pin back to its original position.                                                                                                                                                            

To start on the basic principle, examine the simple diagram below. It comprises a camshaft with two cam-lobes side-by-side. These lobes drive two side-by-side valve rocker arms.

The two cam/rocker pairs operates independently of each other. One of the two cam-lobes are intentionally drawn to be different. The one on the left has a "wilder" profile, it will open its valve earlier, open it more, and close it later, compared to the one on the right. Under normal operation, each pair of cam-lobe/rocker-arm assembly will work independently of each other.

VTEC uses the pin actuation mechanism to link the mild-cam rocker arm to the wild-cam rocker arm. This effectively makes the two rocker arms operate as one. This "composite" rocker arm(s) now clearly follows the wild-cam profile of the left rocker arm. This in essence is the basic working principle of all of Honda's VTEC engines.

q  DIFFERENT VARIANTS OF V-TEC:-

q  VARIABLE TIMING CONTROL (VTC)

                                  VTC operating principle is basically that of the generic variable valve timing implementation (this generic implementation is also used by by Toyota in their VVT-i and BMW in their VANOS/double-VANOS system). The generic variable valve timing implementation makes use of a mechanism attached between the cam sprocket and the camshaft. This mechanism has a helical gear link to the sprocket and can be moved relative the sprocket via hydraulic means. When moved, the helical gearing effectively rotates the gear in relation to the sprocket and thus the camshaft as well.

Fig.3-VTC principle

The drawing above serves to illustrate the basic operating principle of VTC (and generic variable valve timing). A labels the cam sprocket (or cam gear) which the timing belt drives. Normally the camshaft is bolted directly to the sprocket. However in VTC, an intermediate gear is used to connect the sprocket to the camshaft. This gear, labelled B has helical gears on its outside. As shown in the drawing, this gear links to the main sprocket which has matching helical gears on the inside. The camshaft, labelled C attaches to the intermediate gear.

The supplementary diagram on the right shows what happens when we move the intermediate gear along its holder in the cam sprocket. Because of the interlinking helical gears, the intermediate gear will rotate along its axis if moved. Now, since the camshaft is attached to this gear, the camshaft will rotate on its axis too. What we have acheived now is that we have move the relative alignment between the camshaft and the driving cam-sprocket - we have changed the cam timing!

q  i-VTEC SYSTEM:-

Diagram explains the layout of the various components implementing i-VTEC.  I have intentionally edited the original diagram very slightly - the lines identifying the VTC components are rather faint and their orientation confusing. I have overlaid them with red lines. They identify the VTC actuator as well as the oil pressure solenoid valve, both attached to the intake camshaft's sprocket. The VTC cam sensor is required by the ECU to determine the current timing of the intake camshaft.  The VTEC mechanism on the intake cam remains essentially the same as those in the current DOHC VTEC engines except for an implementation of VTEC-E for the 'mild' cam.

 

                The diagrams show that VTEC is implemented only on the intake cam.  Now, note that there is an annotation indicating a 'mostly resting (intake) cam' in variations 1 to 3. This is the 'approximately 1-valve' operating principle of VTEC-E. I.e. one intake valve is hardly driven while the other opens in its full glory. This instills a swirl effect on the air-flow which helps in air-fuel mixture and allows the use of the crazy 20+ to 1 air-to-fuel ratio in lean-burn or economy mode during idle running conditions.  On first acquaintance, variations 1 and 3 seem identical. However, in reality they represent two different engine configurations - electronic-wise. Variation 1 is lean burn mode, the state in which the ECU uses >20:1 air-fuel ratio. VTC closes the intake/exhaust valve overlap to a minimal. Note that lean-burn mode or variation 1 is used only for very light throttle operations as identified by the full load Torque curve overlaid on the VTC/RPM graph. During heavy throttle runs, the ECU goes into variation 3 Lean-burn mode is contained within variation-2 as a dotted area probably for the reason that the ECU bounces to-and-fro between the two modes depending on engine rpm, throttle pressure and engine load, just like the 3-stage VTEC D15B and D17A. In variation-2, the ECU pops out of lean-burn mode, goes back to 14.7 or 12 to 1 air-fuel ratios and brings the intake/exhaust overlap right up to maximum. This as Honda explains will induce the EGR effect, which makes use of exhaust gases to reduce emissions.  Variation-3 is the mode where the ECU varies intake/exhaust-opening overlap dynamically based on engine rpm for heavy throttle runs but low engine revs. Note also that variations 1 to 3 are used in what Honda loosely terms the idle rpm. For 3-stage VTEC engines, idle rpms take on a much broader meaning. It is no longer the steady 750rpm or so for an engine at rest. For 3-stage VTEC, idle rpm also means low running rpm during ideal operating conditions, i.e. closed or very narrow throttle positions, flat even roads, steady speed, etc. It is an idle rpm range. The K20A engine implements this as well.  

          Variation-4 is activated whenever rpm rises and throttle pressure increases, indicating a sense of urgency as conveyed by the driver's right foot. This mode sees the wild(er) cams of the intake camshaft being activated, the engine goes into 16-valve mode now and VTC dynamically varies the intake camshaft to provide optimum intake/exhaust valve overlap for power.                                         

           On i-VTEC engines, the engine computer also monitors cam position, intake manifold pressure, and engine rpm, then commands the VTC (variable timing control) actuator to advance or retard the cam. At idle, the intake cam is almost fully retarded to deliver a stable idle and reduce oxides of nitrogen (NOX) emissions. The intake cam is progressively advanced as rpm builds, so the intake valves open sooner and valve overlap increases. This reduces pumping losses, increasing fuel economy while further reducing exhaust emissions due to the creation of an internal exhaust gas recirculation (EGR) effect.

              i-VTEC introduced continuously variable timing, which allowed it to have more than two profiles for timing and lift, which was the limitation of previous systems. The valve lift is still a 2-stage setup as before, but the camshaft is now rotated via hydraulic control to advance or retard valve timing. The effect is further optimization of torque output, especially at low RPMs. 

 Increased performance is one advantage of the i-VTEC system. The torque curve is "flatter" and does not exhibit any dips in torque that previous VTEC engines had without variable camshaft timing. Horsepower output is up, but so is fuel economy. Optimizing combustion with high swirl induction makes these engines even more efficient.                                                          Finally, one unnoticed but major advantage of i-VTEC is the reduction in engine emissions. High swirl intake and better combustion allows more precise air-fuel ratio control. This results in substantially reduced emissions, particularly NOx. Variable control of camshaft timing has allowed Honda to eliminate the EGR system. Exhaust gases are now retained in the cylinder when necessary by changing camshaft timing. This also reduces emissions without hindering performance.

3.APPLICATIONS :-                                                                                                                                    Currently i-VTEC technology is available on three Honda products;

Ø  2002 Honda CRV

Ø  2002 Acura RSX

Ø  Honda Civic 2006

q  CASE STUDY  OF ‘HONDA  CIVIC  2006’  WITH  1.8 liter  ENGINE

          The new i- VTEC system in Honda civic 2006 uses its valve timing control system to deliver acceleration performance equivalent to a 2.0-liter engine and fuel economy approximately 6% better than the current 1.7-liter Civic engine. During cruising, the new engine achieves fuel economy equivalent to that of a 1.5-liter engine.

          In a conventional engine, the throttle valve is normally partly closed under low-load conditions to control the intake volume of the fuel-air mixture. During this time, pumping losses are incurred due to intake resistance, and this is one factor that leads to reduced engine efficiency.

             The i-VTEC engine delays intake valve closure timing to control the intake volume of the air-fuel mixture, allowing the throttle valve to remain wide open even under low-load conditions for a major reduction in pumping losses of up to 16%. Combined with friction-reducing measures, this results in an increase in fuel efficiency for the engine itself.

            A DBW (Drive By Wire) system provides high-precision control over the throttle valve while the valve timing is being changed over, delivering smooth driving performance that leaves the driver unaware of any torque fluctuations.

          Other innovations in the new VTEC include a variable-length intake manifold to further improve intake efficiency and piston oil jets that cool the pistons to suppress engine knock.

         In addition, lower block construction resulting in a more rigid engine frame, aluminum rocker arms, high-strength cracked connecting rods, a narrow, silent cam chain, and other innovations make the engine more compact and lightweight. It is both lighter and shorter overall than the current Civic 1.7-liter engine, and quieter as well.

q  SPECIFICATIONS  OF   1.8l i-VTEC ENGINE

Ø  Engine type and number of cylinders         Water-cooled in-line 4-cylinder

Ø  Displacement                                               1,799 cc

Ø  Max power / rpm                                          103 kW (138 hp)/ 6300

Ø  Torque / rpm                                                 174 Nm (128 lb-ft)/4300

Ø  Compression ratio                                        10.5:1

q  PERFORMANCE :-

This new engine utilizes Honda's "VTEC" technology, which adjusts valve timing and lift based on the engine's RPM, but adds "VTC" - Variable Timing Control - which continuously modulates the intake valve overlap depending on engine load. The two combined yield in a highly intelligent valve timing and lift mechanism.In addition to such technology, improvements in the intake manifold, rearward exhaust system, lean-burn-optimized catalytic converter help to create an engine that outputs 103kW (140PS) @ 6300rpm,and provides ample mid-range torque. It also satisfies the year 2010 fuel efficiency standard of14.2km/Landreceives the government standard of "LEV" .

4.     FUTURE TRENDS :-                                                                                                     

               From now onwards, there is all likelihood that Honda will implement i-VTEC on its performance engines.  Again what i-VTEC does allow is for Honda to go for the sky in terms of specific power output but yet still maintaining a good level of mid-range power. Already extremely authoritative reviewers like BEST motoring have complained about the lack of a broad mid-range power from for e.g. the F20C engine. In a tight windy circuit like Tsukuba and Ebisu, the S2000 finds it extremely tough going to overtake the Integra Type-R in 5-lap battles despite having 50ps or 25% more power. To get the extreme power levels of the F20C, the wild cams' power curve are so narrow that there is effectively a big hole in the composite power curve below 6000rpm. What i-VTEC can do to this situation is to allow fine-tuning of the power curve, to broaden it, by varying valve opening overlap. Thus this will restore a lot of mid-range power to super-high-output DOHC VTEC engines allowing Honda, if they so desire, to go for even higher specific outputs without too much of a sacrifice to mid-range power.                

5.CONCLUSION: -                                                                                                  i-VTEC system is more sophisticated than earlier variable-valve-timing systems, which could only change the time both valves are open during the intake/exhaust overlap period on the transition between the exhaust and induction strokes. By contrast, the i-VTEC setup can alter both camshaft duration and valve lift.  i-VTEC Technology gives us the best in vehicle performance.  Fuel economy is increased, emissions are reduced, derivability is enhanced and power is improved.

CRYOGENIC HEAT TREATMENT

Abstract

Cryogenic temperatures are defined by the Cryogenic Society of America as being temperatures below 120⁰K (-244⁰F, -153⁰C). 

Durability is the most important criterion used to define the quality of a tool steel. Cryogenic treatment and tempering of metals has been ac- knowledge for almost thirty years as an effective method for increasing durability, or "wear life" and decreasing residual stress in tool steels. Deep cryogenics (below -300°F) is creating many new applications in science. High temperature superconductors, the super-conducting super collider, cryo-biology, magneto-hydrodynamic drive systems for ships, and low temperature physics have all developed recently. The deep cryogenic treatment and tempering process for metals is economical. It is a one time permanent treatment, affecting the entire part, not just the surface. The treatment may be applied to new or used tools, sharp or dull, and reshaping will not destroy the imparted properties. Benefits achieved from subjecting tools to this treatment include: increases in tensile strength, toughness, and stability through the release of internal stresses.

Cryogenic Treatment for Improved Properties

A research metallurgist at the National Bureau of Standards in Boulder Colorado, states, "When carbon precipitates form, the internal stress in the martensite is reduced, which minimizes the susceptibility to micro cracking. The wide distribution of very hard, fine carbides from deep cryogenic treatment also increases wear resistance." The study concludes: "...fine carbon carbides and resultant tight lattice structures are precipitated from cryogenic treatment. These particles are responsible for the exceptional wear characteristics imparted by the process, due to a denser molecular structure and resulting larger surface area of contact, reducing friction, heat and wear." There have been skeptics of the cryogenic process for some time, because it imparts no apparent visible changes to the metal. Since proper heat treating can transform 85% of the retained austenite to martensite and the deep cryogenic process only transforms an additional 8 to 15%, the deep cryogenic treatment has been considered an inefficient process. While these percentages are correct, the conclusion drawn from them is inaccurate. In addition to the trans- formation to martensite, the subjected metals also develop a more uniform, refined microstructure with greater density. Although known to exist, this type of microstructure was only recently quantified scientifically. Particles known as "binders" are coupled with the precipitation of the additional micro fine carbide "fillers". The fillers take up the remaining space in the micro-voids, resulting in a much denser, coherent structure of the tool steel. These particles are identified and counted in the above study cited, using a scanning electron microscope with field particle quanti- fiction (an automatic particle counter). It is now believed that these particles are largely responsible for the great gains in wear resistivity. The permanent irreversible molecular change created is uniform throughout the tool, unlike coatings, and will last the life of the tool, regardless of any subsequent finishing operations or regrinds.

Fig. 1 shows two photomicrographs (1000 x) representative of samples from the same S-7 bar stock. The first is untreated S-7. The second was deep cryogenically treated. Both samples initially were conventionally heat treated; that is, austenitized and oil quenched. The deep cryogenic treatment consisted of varying ramp with pause at -150°F for 1 hr, at -270°F for 2 hr and soaking for 8 hr at -310°F, followed by tempering at 300°F for 1 hr, AC to room temperature and tempering at 225°F, AC. In this micro- structure, note the considerably greater number of fine particles coupled with fine carbides in comparison with the untreated sample. The martensitic transformation is readily apparent.

Deep Cryogenic Treatment Potential

The cryogenic cycle is an extension of standard heat-treatment, and creates many outstanding increases in durability. Some examples are as follows. A major aircraft manufacturer testing deep cryogenic treatment found that with only six different tools treated, the savings in tool purchases could exceed $5 million. An Arizona State study conducted by Laurel Hunt, used deep treated C-2 debarring tools on INCONEL alloy 718, achieving a 400% improvement based on weight, after five cats of .003 in. (.007 cm) on this alloy. This deep cryogenic treatment of an 8% cobalt end mill has made dramatic improvements in two important ways. The number of milling cats was increased from three before deep cryogenic processing, to 78 cats after processing (26 times the wear life). Resharpening the end mills after deep cryogenic treatment required only 1/3 the amount of stock removal to restore the tool geometry. Rockwell, a major aircraft manufacturer, using C-2 carbide inserts to mill epoxy graphite, doubles their output after deep cryogenic treatment of the inserts. In a second test, a 400% improvement was achieved upon milling 4340 stainless steel with cryogenic treated tool. Other applications include: Leading national stock car drivers who previously raced only 4-8 races between equipment teardowns, drove in 40+ races before teardown after cryogenically treating block, crank, cam, pistons and heads.

Confirmation Of Lab Results For Field Tests (Shallow Cryogenic Cycles)

The latest research data on cryogenic and tempering cycle confirms the long standing theory that cryogenic treatment significantly enhances cutting tool life. Dr. Loan Alexandra and Dr. Constantin Picos of the Polytechnic Institute of Jassy, Romania, utilized the latest scientific equipment available, a JEOL IXA-5A Electron Probe, a DRON-1 X-ray Diffractometer, a Qaantimet 720 Quantitative Microscope, and a Chevenard Differential Dilatometer to supply the following results from the extensive study. The study involved 7 samples (A- N, Fig. 2) each subjected to a different heat/cool cycle as noted. Each sample was the equivalent of M2 steel. The carbide particles were physically counted, both before and after the deep cryogenic treatment.

The team then measured the samples with the equipment above, and with standard metallurgical evaluative testing. The results confirm with tangible evidence the carbon participation in cryogenic processing

 Fig. 2 Standard heat treating, austenitizing, oil quenching and tempering, compared to cycles with added cryogenic (-70°C) and tempering cycles. (Source :- Jassy polytechnic institute / Alexandraue ).

Fig. 3 Cryogenic and tempering cycle doubles durability, decreasing austenite while doubling micro fine carbides. (Source :- Jassy polytechnic institute / Alexandraue )

The results of the testing, Fig. 3, comparing standard heat treating to heat treating with the addition of a shallow cryogenic soak (-70°C) are summarized as follows: austenite de- creased from 42.6% to 0.9%; martensite increased from 66% to 81.7%; car- bides increased from 6.9% to 17.4%; mean number of carbides counted @ 1mm sq increased from 31,358.17 to 83,529.73; number of carbides less than 1 µm increased from 23,410.24 to 69,646.09; Rockwell increased from 60.10 to 66.10; tensile strength in- creased from 86.0 to 244.46; bending tensile rate increased from 0.65 to 1.85; KCU (resiliency) increased from .0668 to 1.18; HRC after 20 minutes hold at 675°C: 56.88 to 62.25.

Durability in terms of length of cutting time increased from 20 minutes to 45 minutes with a shallow cryogenic cycle. Fig. 2 illustrates the seven separate heat/cool cycles used to temper the lathe cutting tools. The tools were then used to cut 0.5% structural carbon steel (see Table I). Durability was established by measuring the radical component of wear.

Table :1 Parameters for Lathe Cutting Tools in Wear Resistant Test

Intensive Speed	33.6 m/min
Depth	5 mm
Feed	0.62 mm per rev
Relief Angle	8 Deg
Hack Angle	5 Deg
Plan	45 Deg

Deep Cryogenic Cycle vs Shallow Cryogenic Cycle

            Separate laboratory testing has been accomplished by Dr. Randall F. Barron at Louisiana Tech University. The results by Dr. Barron more than substantiated the Jassy study. In one series of tests compared were five common steel alloys (see Fig. 4). First they were wear tested as pro- cured, then as chilled to -120°F and finally tested after treating at -317°F. In all cases the cold treatment improved wear resistance; the colder the treatment, the more favorable the results. The -120°F (dry ice) treatment improved ratios ranging from 1.2 to 2 times depending on the alloy. This is consistent with the Jassy findings. However, the deep cryogenic treatment in liquid nitrogen at -317°F soak improved wear resistance by even greater ratios running from 2 to 6.6 times.

Process Advancement through New Equipment and Computerization

The deep cryogenic process has had an Achilles heel. It has been inconsistent. In the past, improvements to cutting tools would vary from little improvement to over 1000% increased in useful life. The key to effective improvements consistently is proper processing. If a cutting tool is dropped in liquid nitrogen, without tem- perature control, the tool could shatter. Metals require specific cooling rates; temperature changes must be controlled exactly to obtain the optimal cooling curve. The computer processor solves the problem, since it al- lows exact duplication of the optimal cooling curve, repeatedly. The older cryogenic tanks did not have adequate controls. A relatively new cryogenic system (model 2953, lead illustration) achieves consistent results. The new cryogenic machines operate with controlled dry thermal treatment. "Controlled" simply means that the process is performed according to a precise prescribed time table. A process controller (Yokogawa UP 25) operates the descent; soak and ascent modes (see Fig. 5). Generally, the material is cooled slowly to -317°F, held for 20-60 hr then raised to +300°F, and slowly returned to room temperature. The machine switches over to the electrical resistance mode for the tempering operation. The "dry" process prevents the metals from being subjected to liquid nitrogen, and eliminates the placing of an item in the freezer and pushing a button. A breakthrough in system insulation has been achieved as a result of the space program. The system is de- signed to accomplish thermal transfer, and the more efficient the better. It is essential to transfer themes from the liquid nitrogen to the metal parts being treated, without losing the therms to the outside. Thus, the vacuum chamber is designed for three- level insulation. Walls of the chamber are 3 in. stainless steel. On the inside wall are 125 wrapped layers of aluminized polyester film. Inside the chamber it self is 2 in. polyisocyanurate high density foam which is coated with Ceramaseal amorphous vapor barrier comprised of micro spherical ceramic globes. A 93% increase in processing ability is accomplished with the "space shuttle insulation" in the vacuum walls, providing considerable savings in processing and making the treatment economical for a variety of items in addition to tooling. 

Industrial Practice and Advantages for Heat Treaters

            Potentially every tool heat treated is a candidate for the additional ser- vice of cryogenic treatment and tempering. It is economical to provide the additional improvement of any perishable item. There are more than a handful of large tooling manufacturers utilizing the process today for manufacturing a premium line of cutting tools. More than 200 heat treaters provide cold cryogenic services. However, 95% of these are only utilizing -120°F (dry ice) treatments. Only a handful of companies provide cryogenic treatment below -300°F, which results in much more impressive results and accompanying benefits. A small Massachusetts firm has been processing items for 12 years. The strings on a piano which was previously tuned every six months were treated. The piano has not been tuned for five years. Musicians who play guitar and violin firmly believe that the strings are brighter in sound. Oscilloscopes confirm a shift after treatment. A firm in Michigan has been processing with the method for 27 years. They also specialize in stress relief of the plastic material used in contact lenses, among other items. A cryogenic treating company in Phoenix treats many aerospace parts. Another processor in Ohio treats many carbide tools. The treatment is gaining acceptance nationwide. The process is used in Europe and Australia under the trade name CryoTough, a BOC treatment.

CONCLUSION:

While not a "Magic-Wand" which will extend the life of everything, over 100 tools such as reamers, taps, dies, broaches, drills, end mills, slicers and cutting knives do respond consistently to this process. Cryogenic ser- vice can create a "premium" more profitable tool line for a manufacturer. It is also saving considerable tool expense for the end user. The process is effective throughout the tool un- like a coating, so tools can be resharpened and retain the benefits of the treatment until completely worn out. The process also works with Tin coatings.

When a specific tool receives wear extension, there is a  95% certainty similar tools will respond consistently in the future to the same exact cycle. Among the properties which define the cutting qualities of a tool steel, durability is the highest importance. Results in this regard are decisive in establishing the benefits of cryogenic treatment and also answer the decades long question, "what happens when parts are tested in this manner?"

Biogas Technology for Rural Development

Abstract

The utilization of microbial activity to treat agricultural, industrial, and domestic wastes has been common practice for a half century. In recent years, biogas systems have attracted considerable attention as a promising approach to decentralized rural development. Developed and developing countries and several international organizations have shown interest in biogas systems with respect to various objectives: a renewable source of energy, bio-fertilizer, waste recycling, rural development, public health and hygiene, pollution control, environmental management, appropriate technology, and technical cooperation. This paper provides an overview of biogas technology and opportunities to use this technology in livestock facilities across the ruler area. First, a brief description of biogas technology is provided. Then the benefits of biogas technology are discussed. Finally, the experience and status of biogas technology development in the India are described.

Keywords- Biogas, Fermentation, Methane, Rural Energy, Renewable Energy

 

1.      Introduction

Developing-country rural areas have a variety of available biomass materials, including fuel wood, agricultural wastes, and animal wastes. In particular, many countries have large cattle and buffalo herds, whose considerable wastes have much energy potential. Traditionally, these wastes are carefully collected in India and used as fertilizer, except in places where villagers are forced by the scarcity of fuel wood to burn dung-cakes as cooking fuel. Since biogas plants yield sludge fertilizer, the biogas fuel and/or electricity generated is a valuable additional bonus. It is this bonus output that has motivated the large biogas programmes in a number of developing countries, particularly India

Rural energy planning requires choices among energy technologies. Up to the day, the choices have been confined to centralized energy supply technologies - power plants based on hydroelectricity, coal, oil, or natural gas. The problem is local and global environmental degradation. It has, therefore, become essential to extend the list of technological alternatives for energy decision-making to include decentralized sources of supply.

          

2.      Biogas

Biogas is actually a mixture of gases, usually carbon dioxide and methane. It is produced by a few kinds of microorganisms, usually when air or oxygen is absent. (The absence of oxygen is called "anaerobic conditions.") Animals that eat a lot of plant material, particularly grazing animals such as cattle, produce large amounts of biogas. The biogas is produced not by the cows themselves, but by billions of microorganisms living in their digestive systems. Biogas also develops in bogs and at the bottom of lakes, where decaying organic matter builds up under wet and anaerobic conditions.

Besides being able to live without oxygen, methane-producing microorganisms have another special feature: They are among the very few creatures that can digest cellulose, the main ingredient of plant fibres. Another special feature of these organisms is that they are very sensitive to conditions in their environment, such as temperature, acidity, the amount of water, etc.

Methane, which is the main constituent a colourless, odourless, inflammable gas, it has been referred to as sewerage gas, klar gas, marsh gas, refuse-derived fuel (RDF), sludge gas, will-o'-the-wisp of marsh lands, fool's fire, gobar gas (cow dung gas), bioenergy, and "fuel of the future." The gas mixture produced is composed roughly of 65 percent CH₄, 30 percent CO₂, and 1 per cent H₂S. A thousand cubic feet of processed biogas is equivalent to 600 cubic feet of natural gas, 6.4 gallons of butane, 5.2 gallons of gasoline, or 4.6 gallons of diesel oil. For cooking and lighting, a family of four would consume 150 cubic feet of biogas per day, an amount that is easily generated from the family's night soil and the dung of three cows. In addition, rural housewives using the biofuel are spared the irritating smoke resulting from the combustion of firewood; cattle dung cakes, and the detritus of raw vegetables

3. History of Biogas

People have been using biogas for over 200 years. In the days before electricity, biogas was drawn from the underground sewer pipes in London and burned in street lamps, which were known as "gaslights." In many parts of the world, biogas is used to heat and light homes, to cook, and even to fuel buses. It is collected from large-scale sources such as landfills and pig barns, and through small domestic or community systems in many villages.

The decomposition breaks down the organic matter, releasing various gases. The main gases released are methane, carbon dioxide, hydrogen and hydrogen sulphide. Bacteria carry out the decomposition or fermentation. The conditions for creating biogas have to be anaerobic that is without any air and in the presence of water. The organic waste matter is generally animal or cattle dung, plant wastes, etc. These waste products contain carbohydrates, proteins and fat material that are broken down by bacteria.  The waste matter is soaked in water to give the bacteria a proper medium to grow. Absence of air or oxygen is 

important for decomposition because bacteria then take oxygen from the waste material itself and in the process break them down.

4. Biogas is a Form of Renewable Energy

Flammable biogas can be collected using a simple tank, as shown here. Animal manure is stored in a closed tank where the gas accumulates. It makes an excellent fuel for cook stoves and furnaces, and can be used in place of regular natural gas, which is a fossil fuel. Biogas is considered to be a source of renewable energy. This is because the production of biogas depends on the supply of grass, which usually grows back each year. By comparison, the natural gas used in most of our homes is not considered a form of renewable energy. Natural gas formed from the fossilized remains of plants and animals-a process that took millions of years. These resources do not "grow back" in a time scale that is meaningful for humans

Biogas generation cycle

There are two types of bio gas plants that are used in India. These plants mainly use cattle dung called “gobar” and are hence called gobar gas plant. Generally a slurry is made from cattle dung and water, which forms the starting material for these plants.

The two types of bio gas plants are
1. Floating gas-holder type

2. Fixed dome type

                Floating gasholder type of plant: The diagram below shows the details of a floating gasholder type of bio gas plant. A well is made out of concrete. This is called the digester tank T. It is divided into two parts. One side has the inlet, from where slurry is fed to the tank. The tank has a cylindrical dome H made of stainless steel that floats on the slurry and collects the gas generated. Hence the name given to this type of plant is floating gas holder type of bio gas plant. The slurry is made to ferment for about 50 days. As more gas is made by the bacterial fermentation, the pressure inside H increases. The gas can be taken out through outlet pipe V.  The decomposed matter expands and overflows into the next chamber in tank T.  This is then removed by the outlet pipe to the overflow tank and is used as manure for cultivation purposes.

5. Energy in Biogas

               

                The main problem in the economic evaluation is to allocate a suitable monetary value to the non-commercial fuels, which have so far no market prices. For the majority of rural households biogas is primarily a means of supplying energy for daily cooking and for lighting. They use mainly firewood, dried cow dung and harvest residues as fuel. But even if the particular household does not purchase the required traditional fuel, it's value can be calculated with the help of fuel prices on the local market. Theoretically, the firewood collector of the family could sell the amount that is no longer needed in the household

                As an example, the rural households in India use the following quantities of non-commercial fuel per capita daily:

                                - firewood: 0.62 kg

                                - dried cow dung: 0.34 kg

                                - harvest residues: 0.20 kg

For rural households in the People's Republic of China the daily consumption of

                firewood is similar: between 0.55 - 0.83 kg per person.

                Which sources of energy have been used so far and to what extent they can be replaced must be determined for the economic evaluation of biogas by means of calorific value relations. The monetary benefits of biogas depend mainly on how far commercial fuels can be replaced and their respective price on the market.

                1 m3 Biogas (approx. 6 kWh/m3) is equivalent to:

                                Diesel, Kerosene (approx. 12 kWh/kg) 0.5 kg

                                Wood (approx. 4.5 kWh/kg) 1.3 kg

                                Cow dung (approx. 5 kWh/kg dry matter) 1.2 kg

                                Plant residues (approx. 4.5 kWh/kg d.m.) 1.3 kg

                                Hard coal (approx. 8.5 kWh/kg) 0.7 kg

                                City gas (approx. 5.3 kWh/m3) 1.1 m3

                                Propane (approx. 25 kWh/m3) 0.24 m3

 

6. The Benefits for Biogas

               

                Individual households judge the profitability of biogas plants primarily from the monetary surplus gained from utilizing biogas and bio-fertilizer in relation to the cost of the plants. The following effects, to be documented and provided with a monetary value, should be listed as benefits: expenditure saved by the substitution of other energy sources with biogas.

                If applicable, income from the sale of biogas; expenditure saved by the substitution of mineral fertilizers with bio-fertilizer. Increased yield by using bio-fertilizer. If applicable, income from the sale of bio-fertilizer; savings in the cost of disposal and treatment of substrates (mainly for waste-water treatment); time saved for collecting and preparing previously used fuel materials (if applicable), time saved for work in the stable and for spreading manure (if this time can be used to generate income). Monetarizing individual benefits The economic evaluation of the individual benefits of biogas plants is relatively simple if the users cover their energy and fertilizer demands commercially. In general, the monetary benefits from biogas plants for enterprises and institutions as well as from plants for well-to-do households should be quite reliably calculable. These groups normally purchase commercial fuels e.g. oil, gas and coal as well as mineral fertilizers. In industrialized countries, it is common practice to feed surplus electric energy, produced by biogas-driven generators, in the grid. Biogas slurry is a marketable product and the infrastructure allows it's transport at reasonable cost. Furthermore, treatment of waste and waste water is strictly regulated by law, causing communes, companies and farmers expenses which, if reduced with the help of biogas technology, are directly calculable benefits. In contrast, small farmers in developing countries collect and use mostly traditional fuels and fertilizers like wood, harvest residues and cow dung. No direct monetary savings can be attributed to the use of biogas and bio-fertilizer. The monetary value of biogas has to be calculated through the time saved for collecting fuel, the monetary value for bio-fertilizer through the expected increase in crop yields. Both in theory and in practice, this is problematic. In practice, a farmer would not value time for fuel collection very highly as it is often done by children or by somebody with low or no opportunity costs for his/her labor. In theory, it is difficult to define the value of unskilled labor. Similarly, the improved fertilizing value of biogas slurry will not be accepted by most farmers as a basis for cost-benefit analysis. They tend to judge the quality of slurry when counting the bags after harvest. Because a monetary calculation is not the only factor featuring in the decision to construct and operate a biogas plant, other factors come in which are less tangible: convenience, comfort, status, security of supply and others that could be subsumed under 'life quality'. Acceptance by the target group Besides the willingness and ability to invest considerable funds in biogas technology, there is a complex process of decision making involved when moving from traditional practices to a 'modern' way of producing fertilizer and  acquiring energy. Hopes and fears, expected reactions from the society, previous experiences with modern technology, all these feature in a decision. For a biogas program, it is important to realize that economic considerations are only part of the deciding factors in favor or against biogas technology. All these factors can be subsumed under acceptance. Acceptance is not a collection of irrational, economically unjustifiable pros and cons that a biogas extension project is called upon to dissolve. Rural households, as a rule, take rational decisions. But rural households and biogas programs often have information deficits that lead to non-acceptance of biogas technology by the target groups. Bridging this information gap from the farmer to the project and vice versa is a precondition for demonstrating the economic viability in a way that is understandable, relevant and acceptable to the farmer.

 

7. Biogas programs

               

                Biogas programs, however, should not neglect the argument of improved yields.

Increases in agricultural production as a result of the use of bio-fertilizer of 6 - 10 % and in some cases of up to 20 % have been reported. Although improved yields through biogas slurry are difficult to capture in a stringent economic calculation, for demonstration and farmer-to-farmer extension they are very effective. Farmers should be encouraged to record harvests on their plots, before and after the introduction of biogas. Statements of farmers like: "Since I use biogas slurry, I can harvest two bags of maize more on this plot" may not convince economists, but they are well understood by farmers.

                As mentioned earlier, to tap the potential of various renewable resources of energy, a variety of technology dissemination programmes are being implemented by the government in active collaboration with NGOs (non-governmental organizations), like TERI. In the last two decades, complexities in rural energy planning have been seriously considered and linked with overall development planning by way of decentralized planning. Programmes are being implemented at block level, such as the IREP (Integrated Rural Energy Programme), which was coordinated by the Energy Cell of the Planning Commission. The MNES earlier started with village-level planning and implementation of projects. Later, it attempted to develop a methodology for district-level energy planning in select districts of the country. In order to be more effective in implementation as well as administration of energy activities, the MNES has now chosen to devise energy plans at the block level. The studies are being undertaken in select 100 blocks in different states.

8. Conclusions-

    Biomass is available all round the year. It is cheap, widely available, easy to transport,
store, and has no environmental hazards.
 It can be obtained from plantation of land having no competitive use.
 Biomass-based power generation systems, linked to plantations on wasteland, simultaneously address the vital issues of wastelands development, environmental restoration, rural employment generation, and generation of power with no distribution losses.
 It can be combined with production of other useful products, making it an attractive
byproduct.

Biogas, although typically used for heating and cooking, can also be used to fuel a genset to produce electricity. 3.4 million biogas digesters are in daily use in India, and smaller