bio-bike project presentation

Final Year Group Project

Group Members: Amit Prem, Anup Suvarna, Varun Uthappa, Guru Prasad Shetty

The main aim of the project was to develop a prototype hybrid motorcycle to run on Compressed Natural Gas (CNG) and petrol as fuel.

The objective of the project are as follows:◦ Design and build working prototypes for inlet and exhaust systems to

accommodate both types of fuel.◦ Modification to the motorcycle chassis to accommodate additional

components.◦ Engine tuning to run CNG.◦ Reduce Emission and do a comparative test with the two fuel types. ◦ Compare performance changes.

Aim and Objectives

Compressed natural gas (CNG) is one of the alternative fuels and in its compressed form can play a vital role to augment the bargaining demand of diesel and petrol in the transport sector.

CNG as a fuel is clean and has got distinct technical, economic and ecological advantage over conventional fuel which makes it an excellent automotive fuel. More than the economic consideration the potential to reduce emissions will be the main reason to promote natural gas by many countries.

Existing petrol vehicles can use CNG by installing a bi-fuel conversion kit and then the converted vehicles can have the flexibility of operation either on CNG or petrol.

CNG is a mixture of hydrocarbons consisting of approximately 80% to 90% methane in gaseous form. Due to its low energy density, it is compressed to a pressure of 200 to 250 kg/cm² and hence the name compressed natural gas.

Introduction

Methane is the simplest alkaline and the principal component of natural gas. A chemical compound with the molecular formula CH4. Methane was discovered and isolated by Alessandro Volta between 1776 and 1778 when studying marsh gas from Lake Maggiore.

Methane's bond angles are 109.5 degrees. Burning methane in the presence of oxygen produces carbon dioxide and water. The relative abundance of methane and its clean burning process makes it a very attractive alternative fuel.

Methane being a gas at normal temperature and pressure, is difficult to transport from its source. In its natural gas form, it is generally transported in bulk by pipeline or LNG carriers.

The abundance of methane in the Earth's atmosphere in 1998 was 1745 parts per billion, up from 700 ppb in 1750. In the same time period, CO2 increased from 278 to 365 parts per million. In addition, there is a large, but unknown, amount of methane in methane clathrates in the ocean floors. The Earth contains huge amounts of methane. Large amounts of methane are produced anaerobically by methanogenesis. Other sources include mud volcanoes, which are connected with deep geological faults, and livestock (primarily cows) from fermentation.

Methane-The Next Generation Fuel

In general, methane reactions are hard to control. Partial oxidation to methanol, for example, is difficult to achieve; the reaction typically progresses all the way to carbon dioxide and water.

Methane is believed to form a formaldehyde ( H2CO). The formaldehyde gives a formyl radical (HCO), which then forms carbon monoxide (CO). The process is called oxidative pyrolysis:

CH4 + O2 → CO + H2 + H2O

Following oxidative pyrolysis, the H2 oxidizes, forming H2O, replenishing the active species and releasing heat. This occurs very quickly, usually in significantly less than a millisecond.

2H2 + O2 →2H2O

Finally, the CO oxidizes, forming CO2 and releasing more heat. This process is generally slower than the other chemical steps, and typically requires a few to several milliseconds to occur.

2CO + O2 →2CO2

The result of the above is the following total equation: CH4(g) + 2O2(g) → CO2(g) + 2H2O(l) + 890 kJ/mol Where bracketed "g" stands for gaseous form and bracketed "l" stands for liquid form.

Methane-The Next Generation Fuel

Constituent Approximate %Methane 94.50Ethane 3.20Propane 0.60Heavier Hydro Carbon 0.30Carbon Dioxide 0.05Nitrogen Gases 1.25Other Gases 0.10

Composition of Methane

Properties of Methane

Property ValueAuto Ignition Temperature 813K

Adiabatic Flame Temperature 2148KNet Calorific Value 51367kj/Cubic mt

Constant Pressure heat of reaction

47772 kj/kg

Research Octane No 130Flammability limits in air (% by

volume)5-15

Maximum burning velocity in air at NTP

0.39mt/sec

Molecular Weight 20.69Gas constant 0.4018

Specific heat at Constant Pressure 1.6297 kj/kgKSpecific heat at Constant Volume 1.2279 kj/kgK

It is a gas at normal condition; it forms a homogenous mixture with air, hence a complete combustion is possible.

Octane number is very high hence ideal fuel for S.I engine. This indicates that higher compression ratio can be used.

Flammability limits are wide; hence it can be operated as a lean mixture; this will lead to low emission of carbon monoxide and nitrogen dioxide.

Stoichiometric air fuel ratio on the mass basis is comparable to other petroleum liquid fuel.

It has an extremely low density as compared to liquid fuels. Hence has to be compressed in order to reduce the storage space.

Its calorific valve on the mass basis is better than other liquid fuels, but on the volume basis (even at every high pressure of 220 bars) it is extremely low; hence the storage space will have to be high even at high pressure.

As the fuel is already available in gaseous form cold starting is possible.

Advantages of Using CNG

It is lighter than air; hence in the event of leakage it will rise in air and reduce the risk of fire.

Since the C/H ratio of methane gas is lower than petrol or diesel, its product contain lesser carbon dioxide. This aspect is of great importance due to the mounting concern with “GREEN HOUSE EFFECT”.

Owing to CNG’s distinct features, it does not contaminate or dilute crankcase oil, giving a new lease of life to the engine.

It is pollution-free and totally environment friendly. It is non-toxic, non-corrosive, and non-carcinogenic. Its high compression ratio reduces fuel consumption and it cannot be adulterated or pilfered.

CNG is an environment friendly fuel. The natural gas is mainly composed of methane and its exhaust emissions consist of water vapours and a small fraction of carbon monoxide. The absence of carbon and other particulates result in negligible amount of harmful elements in exhaust fumes.

Safer; as it is lighter and dissipates quickly. Due to this it ignites quickly, but only when the fuel to air ratio was between 5 – 15% by volume.


Higher Octane number in the range of 120 to 130, which is considerably higher than 93 to 99 Octane for petrol. A high Octane number ensures that CNG fuel can run at high compression ratio without any knocking phenomena to the piston that will cause damage to the engine. Higher flammability compared to petrol that makes it appropriate to run on lean burn technology.

Because it is a clean burning fuel, it reduces the required maintenance cost of vehicle; it can be half of petrol—oil changes can be done for more than 15,000-30,000 km, spark plug points can be changed at intervals up to 120,000 km.

Plenty of reserve; there is an estimated 65-70 year supply of natural gas. Besides made from fossil fuel, natural gas can also be made from agricultural waste, human waste and garbage. Cheaper per litre equivalent than petrol, in Europe 14-17% less than petrol and 12-74% less expensive than diesel.


CNG fuel has some disadvantages that limit its potential to achieve the optimum engine performance, are as stated below:

◦ Since CNG is available in gaseous form, it has a low density. CNG from the mixer drawn into the engine cylinder displaces approximately 8% to 10% of Oxygen by volume. This reduces the amount of Oxygen due to larger space occupied by the CNG in the combustion chamber.

◦ CNG has a low flame speed. Its burns slower than conventional fuels, such as petrol and diesel. As much as 60% decrease in burning velocity has been measured. This prolongs the total combustion duration compared with diesel and petrol. This can cause a further reduction in the engine output of 5 to 10%.

Disadvantages of CNG System

Methane has low density and high diffusivity (three times that of petrol vapor ) hence if leaked methane is unconfined, will disperse quickly to oxygen concentration; where it cannot burn.

Minimum ignition energy needed to ignite methane (0.29 MJ) is higher than petrol(0.24 MJ) hence the risk of fire is lesser.

Higher concentration as compared to petrol is needed to burn methane (5.3% vs 1% to burn and 6.3% vs. 1.1% to detonate); methane flame is colder and is of less heat. Its ignition temperature is high. All these aspect makes this fuel safer.

It is non toxic, carcinogenic, caustic; contact with CNG (after expansion from high pressure) can cause frostbite.

Safety Aspects of CNG (Compare to Petrol)

Higher CR and better flow components for CNG system. This will help to improve engine and vehicle performance further.

An idle speed controller that considers engine load idle, engine coolant temperature and ambient temperature as an input and corrects the mixture accordingly. This is similar to the idle speed control used in case of MPFI vehicles. The vacuum solenoid operated AC kick off can also be used for this purpose.

Experiments are being done to improve the cylinder capacity and also to reduce the size and weight of the cylinder for better mileage of the vehicles.

Performance Improvements of CNG system

BioBike: Specifications

Engine Displacement (CC) 97.2No of cylinders 1Stroke 2/4 4Bore x Stroke 52.4 mm x 57.8mmMaximum Power (bhp/rpm) 7.5/8500

Torque (Nm/rpm) 7.2/5000Compression ratio 6.1:1No of Gears 4Ignition System CDIStart (Kick/Electric) KickKerb Weight 120 kgFront Suspension Telescopic ForksRear suspension Spring with Hydraulic

damper

CNG Cylinder High pressure copper tubes Pressure regulator Pressure reducer Gas-Air mixer Low pressure gas tube Pressure gauge On-Off valve

BioBike: CNG system components

CNG is typically stored in steel or composite containers at high pressure (3000 to 4000 lbf/in², or 205 to 275 bar). These containers are not typically temperature controlled, but are allowed to stay at local ambient temperature.

The cylinder used for our project is 23cm in diameter and 72cm in length.

In order to place the cylinder onto the bike, the existing fuel tank had to be removed. Due to the relative large size of the tank mounting the tank onto the bike required some modification.

The brackets for the tank were made of steel with a length of 79cm, width of 2cm and thickness of 0.5cm. The clamp to hold the brackets were welded onto the chassis. Because of the weight of the NGV tanks, this bracket has to withstand great mechanical stress.

The forces that act on it are very high and can tear it off in a collision; therefore, this bracket must be adequately mounted, with four bolts of no less than M10 with their corresponding lock washer and nuts.

BioBike: CNG system Cylinder Mounting

• The brackets for the NGV cylinders or cradles are specific for each cylinder and for each type of vehicle.

• They are made up of the following parts: Steel bracket on which the cylinder rests, a pair of metallic bands covered with a plastic sheath that avoids friction between the metals and a pair of rubber straps to be placed between the cylinder and the above mentioned bracket, also to avoid contact between the metals.

• A pressurized gas cylinder is probably the strongest component on the vehicle. Vehicles that were totally destroyed in collisions show the only discernable component being the intact gas cylinder.

• It is unlikely that cylinders will rupture due to collision impact. Natural gas is lighter than air and dissipates upward quite quickly if there were a leak.

BioBike: CNG system Cylinder Mounting

The installation of the high-pressure piping can be divided into three sections.

Section 1: Filling Valve – Pressure Regulator

Section 2: Pressure Regulator – Pressure Reducer

Section 3: Pressure Reducer – Engine Intake Manifold

BioBike: CNG system High Pressure Copper Tubes

A “loop” must be made in the Section “filling valve – pressure regulator” every time there is a change in direction of the pipe, or only one if the pipe maintains one direction. It is very important that this section be as short as possible, to avoid passing over other equipment in the engine compartment. The diameter of the copper tube which has been used is 0.7cm.

The following precautions must be taken in the Section “filling valve – NGV cylinders”:

Securely fasten the fuel pipe to the vehicle body using galvanized metal or plastic clamps so that there is no movement whatsoever. The fasteners or clamps should not be placed at a distance exceeding 600 mm.

As in the case of the previous Section, every time there is a change in the direction of the pipe, a “loop” must be made. The piping that goes under the vehicle must not “hang”; it must be placed over some fixed part of the vehicle’s body that can act as its support base.

BioBike: CNG system High Pressure Copper Tubes

A pressure-reducing regulator comprising of a regulator body has an inlet port, an outlet port, and a flow path. A valve element is moved relative to a valve seat by a diaphragm assembly to control gas flow along the flow path. The regulator comprises one or more of:

A coalescing filter mounted in the inlet port

The diaphragm assembly coupled to the valve element via a resilient member

A diaphragm chamber comprising a non-constant depth in the regulator body along its diameter

An aspirator tube extending into the outlet port from a passage between the diaphragm chamber and the outlet port

The valve seat comprising an inner seat and a protective covering over the inner seat.

BioBike: CNG system Pressure Regulator

Reduces CNG pressure from fuel cylinder (s). Inlet from 250 kg/ sq .cm to a range from 0 – 250 kg/sq .cm Factory setting ranges from 0 to 300 kg/sq .cm Manages gas pressure to engine fuel system. Must respond quickly to changing gas flow Must have very predictable output pressure throughout range of flow,

temperature and tank pressure. Manages varying gas compositions. Discussion of Joule-Thomson effect Requires heat to prevent icing inside regulator Enable options for pressure sensor, HP and LP gas fittings, relief valve connection,

etc.

BioBike: CNG system Pressure Regulator

The compressed natural gas enters the reducer at up to 200bar(3000psi) pressure.

The gas enters the 1st stage of the reducer where the pressure is reduced to 3.8 - 4.8bar. The gas pressure stabilizer technology is active.

The gas enters the 2nd stage of the reducer where the pressure is reduced to 0.8 – 1.5bar.

The gas enters the 3rd stage, intake manifold. Vacuum moves the membrane according to engine load and R.P.M. A dampener provision stabilizes the flow and prevents excessive erratic movement of the metering membrane which is optional, assuming smooth engine operation and lowest exhaust emissions.

A small amount of gas bypasses the 3rd stage for easy starting and idle control (adjustable needle valve). This unique feature guaranties easy starting and virtually eliminates the risk of backfire.

BioBike: CNG system Pressure Reducer

BioBike: CNG system Pressure Reducer

In a well designed system, the exhaust can not only ‘scavenge’ the cylinder of burnt gases, but actually suck intake charge into the cylinder at slightly more than atmospheric pressure. Two effects contribute to this. One is to utilize the tendency of the exhaust gases, once moving, to keep on doing so “inertia tuning”. The other “pulse tuning” which relies on pressure waves somewhat like a two – stroke system.

A slight amount of back pressure is required so that the unburnt charge is not sucked into the exhaust. Pulse tuning depends on the length and diameter of the header pipes when the exhaust valve opens, a pressure wave travels down the exhaust, and is reflected at the end as a wave of negative pressure. This travels back up the pipe and helps scavenge and refill the cylinder. Exhaust gases travels down the pipe at around 300 feet per second. But pressure waves, travel up to 5 times as fast.

BioBike: Exhaust System

The exhaust that we used has a header pipe diameter of 2.32cm and a length of 59.9cm. The aftermarket end can that was used provided a power gain of 2hp compromising slightly for the 10% loss in power when a vehicle runs on CNG. The end can that was used was 6.05cm in diameter with a length of 28.3cm. The total length of the exhaust system was 88.2cm.

BioBike: Exhaust System

Due to the nature of the combustion requirement of CNG, the air entering the engine needed to be between 5 to 15 (% by volume).

This would not have been achieved with the regular air flow that is required for the petrol system.

In order to control or minimize the air entering into the engine the air inlet into the air-box was blocked off and a hole was drilled onto the side cover. This hole was then fitted with a threaded PVC pipe so that a cap could be threaded on.

This arrangement enables us to limit the air flow into the engine for the combustion of methane maintaining it within the required range.

The advantage of performing this modification is that if the bike has to be run on petrol at some point all the rider had to do is open the cap so as to increase the air flow into the system for the combustion requirement of petrol.

CNG system works only with limited air entering the engine and the stock air filter system is essential in correctly being able to perform this process.

BioBike: Air-Box Tuning

BioBike: Air-Box Tuning

The Gas-Air mixer is a simple unit which is fixed onto the carburetor with a rubber sleeve. The Gas-Air mixer was made using Aluminium.

It consists of a channel at the center through which air passes into the carburetor.

The unit consists of a Gas inlet from which the low pressure gas from the pressure reducer enters with the help of low pressure rubber hose. Inside the mixer, Air mixes with the Gas from the pressure reducer and enters the engine through the original intake manifold via the carburetor.

No other modification is required for the intake of the gas into the combustion chamber. The throttle action of the existing carburetor causing the slider to move up and down controls the Gas-Air mixture entering the engine.

BioBike: Gas-Air Mixture Tuning

BioBike: Gas-Air Mixture Tuning

BioBike: Before Modifications

BioBike: After Modifications

BioBike: Results - Emission comparison

Constituent Petrol CNG % Reduction

Nox 11 PPM Vol 2 PPM Vol 81.82 %

CO 0.06 PPM Vol 0.02 PPM Vol 66.66 %

NO 10 PPM Vol 2 PPM Vol 80 %

HC 251 PPM Vol 166 PPM Vol 33.86 %

The emission tests conducted shows a remarkable decrease in the pollutant gases that are exhausted into the environment. Methane constitutes of 85% to 99% of natural gas and it is the lightest hydrocarbon, this makes natural gas inherently clean burning fuel, the test conducted proves that fact.

Methane itself is a greenhouse gas and since its utilization results in lesser harmful emissions when compared to petrol shows that a considerable reduction in harmful emission and fewer greenhouse gases will be generated resulting in slowing down of Global Warming and since methane is being utilized the results are more beneficial to the environment and to us.

BioBike: Results - Emission comparison

To produce a cleaner environment for all to live and work in, the development of alternative, cleaner fuels is essential. To encourage the use of the fuels, competitive prices combined with good marketing techniques are required.

Our project bike provided a millage of 110km/kg of methane while the same engine provided a mileage of 70km/liter of petrol this meant the bike is very cheap to run per km in methane which is 16 paisa. The total cost of the conversion can be recovered quickly from the savings accruing by use of CNG. Moreover, Compressed Natural Gas being a cleaner and greener fuel in comparison to Petrol / Diesel there is less wear and tear of the engine.

There is much less carbon deposit in the engine and also the life of Engine oil is enhanced. One can say that on a whole 20 to 30% of bike maintenance costs are saved by using CNG in the long run. Besides economy, there is no compromise to the safety of the bike which is better than petrol due to the nature of the fuel. Engine runs smoother and there is reduction in the noise or vibration of the bike. There is a small amount of power loss but it can be compensated for by increasing the compression ratio and by using an fuel mixture controller based on engine loads. We ran a free flow exhaust to get a 2hp increase in power.

Overall the project was a success and we were able to efficiently demonstrate the use and benefits of CNG as fuel on a Motorcycle. There were a number of learning opportunities through this project.

BioBike: Conclusion

BioBike

Special thanks•Engineering department for the support•Head of Department Dr. NS Sriram •Supervisor Mr Muralidhar •Ashith Shetty for his support.

THANK YOU