The paper deals with the latest trends in “Green Engineering” with a specific importance to automotive & aviation engine developments to reduce or in some cases completely nullify harmful emissions. The latest developments such as biofuel, hydrogen fuel cell & hybrid engine developments have been discussed.
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Introduction to improved engine designs in cars and some of the more eco friendly alternatives in automotive and aviation have been discussed. Some of the technologies that have been implemented in modern eco friendly cars have also been discussed.
Bio-diesel, compressed air, hydrogen etc are fast becoming the most sought after technologies in terms of ecological engine designs. The best thing about these engine designs is that they run on fuel that is renewable and cause little harm to the environment in terms of pollution as compared to petrol and other non renewable sources.
BIO FUEL BASED ENGINES:
Biodiesel is made from 100% renewable vegetable oil and from waste oil sources. Vehicles can be made to run almost entirely on biodiesel. Biodiesel can be used as a viable source for replacing petroleum. Biodiesel engine is nothing but a conventional diesel engine.
Fig1. Biodiesel & Environment cycle
DIESEL TO BIODIESEL:
The solution to diesel is certainly not petrol or gasoline. Biodiesel cars have become such popular choices with people who think about and care for the environment and the future of mankind. Biodiesel engines are basically diesel engines. We can mix diesel and biodiesel to some extent and use them as an alternate however, if we want to switch over to biodiesel completely, there are some minor changes to be made in the engine. Biodiesel degrades articles made of natural rubber. Hence before switching to biodiesel we should replace the rubber parts with polymers like FKM. Biodiesel has a tendency to stick together in cold weather hence we use a heater to preheat the oil. Using a mixture of bio-fuel for a long time may corrode the engine’s oil filters. Hence there is a need to constantly change the oil filters.
RECENT IMPLEMENTATIONS OF BIOFUELS:
Biofuels are being implemented throughout the world in a variety of fields from biofuel powered trucks to aeroplanes. Besides the cost of biofuel is less compared to conventional fuels, just under $1 per liter and its processing is very easy with added eco friendly advantages. Some recent implementations of this technology are as follows.
McDonald’s, the world renowned fast food restaurant is using the biodiesel made from 85 percent McDonald’s waste grease and 15% pure canola oil. McDonald’s claims to use 6.1 million liters of its used oil as bio-fuel which has a capacity to save nearly1625 tones of carbon every year.
Fig(i) A McDonald’s Biodiesel truck.
VIRGIN ATLANTIC JUMBO JET TEST FLIGHT Virgin Atlantic recently carried out a test flight on a jumbo jet fully powered by bio-fuel to show it can produce much less carbon than other companies. The jet flew from Amsterdam to London. Environmentalists and scientists praised the company for its achievement. However some critics blamed that it was just a publicity stunt. Although it is a brave new step it may not come into use until a much further date.
BIOBIKE, A BIODIESEL MOTORCYCLE MADE IN AUSTRALIA, GETS OVER 100 MPG
Fig2. The Bio-Bike
The Yan-mar 400cc Bio-Bike developed by an Australian crew to compete in The World solar bike Challenge. The bike has proven its effectiveness on the field and its uses a CVT transmission. Although there are no plans to introduce the bike commercially there are talks of building them.
COMPRESSED AIR ENGINES;
Angelo di Pietro first found the air engine concept in 2004.It produces high torque when compared to most other air engines making it more suitable and efficient for mobile applications. It is very quite with high torque with only 1 PSI pressure needed for it to start. This invention has the potential to produce emission free transport.
WORKING OF AIR ENGINE:
Fig.3 Di Pietro rotary pneumatic engine.
The space between stator and rotor is subdivided into six expansion chambers. These dividers follow the motion of the shaft driver as it rolls around the stator wall. The cylindrical shaft moves due to the pressure of the air eccentrically, thereby driving the motor shaft by means of two rolling elements mounted on bearings on the shaft. The rolling motion of the shaft is cushioned by the air film. The timing of the operations of the motors is governed by sensors mounted on the outside of the drive shaft. Motor speed is simply controlled by increasing or decreasing the air speed. It has soft start capabilities and high torque at zero RPM.
COMPRESSED AIR CAR MODELS:
One CAT (Compressed Air Technology) is an upcoming compressed air car. India’s Tata Motors is collaborating with Air engine developer Guy Niger of MDI to produce the vehicle. The vehicle contains air tanks that can be filled in four hours by plugging the car into a standard electrical plug. The ease of refueling and production of compressed air make these a suitable option for an environmental friendly future. Compressed air engines reduce the cost of vehicle production, because there is no need to build a cooling system, spark plugs, starter motor, or mufflers. It has zero emissions.
Fig.5 Air car & engine.
Air expands in an engine and must be heated to maintain its ambient temperature.
Conversely, when air is compressed and stored in a tank its temperature decreases and it expands.
BATTERY ELECTRIC VEHICLE:
An Electric car or an electric vehicle derives its power from an onboard battery pack rather than a conventional fuel tank and its prime movers are motors instead of engines. Normally any car that is powered by batteries and that which run on motors are known as Battery Electric Vehicles or BEV’s. The following describes the outlay and working of BEV’s.
WORKING OF BEV’s:
Fig.6 Outlay of BEV.
The general outlay of an electric car is as shown above. The parts are as follows:
Electric cars can use AC or DC motors:
DC motors usually need around 92 to 192 volts to function. DC motors used in electric vehicles usually come from the forklift industry.
AC motors, usually 3 phase AC motors run in a power range of about 240 volts on standard 300 volt battery pack.
Fig.7 Control of motor
There is an AC controller which hooks to the AC motors and there are six parallel transmitters than convert the 300 volts DC power into 240 volts of AC power and gives it to the 3-phase motor, the controller also provides a system for charging of the DC battery packs through a DC-DC converter and a charging port.
DC motors tend to be in the range of 20000 to 30000 watts and are less expensive than other sources. The range of a typical controller will be around 40-60000 watt range. DC motors have features like the overdrive (i.e.) a 20000 watt DC motor can withstand a load of 100000 and give additional horse power to the vehicle.
Fig.8 Electric Motor
Fig.8 Li-ion Battery Pack
Basically in Li-ion battery packs the transfer of electrons between anode and cathode produces current with easy recharging capabilities. Li-ion batteries are the most suitable sources of power in today BEV’s since they provide high power output, are compact and can be recharged easily. Further they have relatively long life compared to other battery sources.
There is a chance of the motor getting self distrusted due to over driving and heating.
Lithium-ion batteries are prone to short circuiting and over charging.
They are costly.
SOME LATEST ELECTRIC CAR DESIGNS:
The Leaf is the first mass-produced electric car for sale from a major manufacturer introduced in Dec/2010. Its estimated range is 117 kilometers with an energy consumption of 765 kJ/km and has a fuel economy of 99 miles per liter of gasoline. It does not produce any tail pipe pollution or any green house gases and has zero emissions.
Fig.9 Nissan Leaf with Battery pack and motor unit
Fig.10 Tesla Roadster.
The Tesla Roadster is a battery electric vehicle (BEV) sports car produced by the electric car firm Tesla Motors in California. The Roadster is the first production automobile to use lithium-ion battery cells and the first production BEV (all-electric) to travel more than 200 miles (320 km) per charge. It is the fastest electric vehicle in its class till date and can reach up to speeds of 125-145 mph with an estimated acceleration time 0-60 in 3.9 seconds.
HYDROGEN FUEL CELL POWERED ENGINES:
HYDROGEN FUEL CELL:
The basic fuel cell arrangement has separator plates, membranes, anode, cathode, gaskets and some time heating elements. Fuel cells only need hydrogen and oxygen to generate power. When used correctly they can provide good power to almost all our needs. Thermocouples and temperature sensors are sometimes provided for accurate control of power.
The power output of a fuel cell is limited hence fuel cells are grouped together in stacks normally known as fuel cell stacks that generate the necessary power needed for the required application.
Fig.11 (a) Hydrogen Fuel Cell
Hydrogen atoms enter at the anode where a catalyst enhances the reaction that strips off the electrons which are negatively charged and ionizes the hydrogen atoms which become positively charged. Thus the electrons are basically converted to DC current and water is obtained as a byproduct as shown in the below reaction.
2 H2 (gas) + O2 (gas) 2 H2O + energy
Fig.11 (b) Fuel-cell renewability
A power system incorporating hydrogen from renewable sources and a fuel cell is a closed system, as none of the products or reactants, water, hydrogen and oxygen are lost to the outside environment. The water consumed by the electrolyzer is converted to gases. The gases are converted back to water. The electrical energy produced by the solar panel is transferred to chemical energy in the form of gases. The gases can be stored and transported, to be reconverted back to electricity.
Fig.12 A Common Hydrogen Fuel cell
ADVANTAGES OF FUEL CELLS:
Fuel cells are efficient. They have no combustion processes
Fuel cells are clean. It has zero emissions with water as a byproduct.
Fuel cells are quiet. Since they do not have any moving parts they are very silent.
Fuel cells are environmentally safe and have no hazardous byproducts that may pollute the atmosphere like other conventional sources.
DISADVANTAGES OF FUEL CELLS:
Fuel cells must obtain mass-market acceptance to succeed.
Platinum is a scarce natural resource. At present platinum is a key component to fuel cells.
At present a large portion of the investment in fuel cells and hydrogen technology has come from auto manufacturers.
FUEL CELL POWERED VEHICLES:
HONDA FCX CLARITY:
The Honda FCX Clarity is a hydrogen fuel cell automobile manufactured by Honda. The design is based on the 2006 Honda FCX Concept. The FCX Clarity demonstrates electric car qualities such as zero emissions while offering 5 minute refueling times and long range in a full function large sedan.
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The vehicle has a 100kw fuel cell stacks and is made only on order. In this the free energy is captured and used for breaking. The electric power is stored in a 288w Li-ion battery pack and is used by the electric motor to produce a horsepower rated at 135. The range of the fuel cells is nearly 280 miles giving nearly 70 miles per charge.
Fig.13 HONDA FCX CLARITY
FUEL EFFICIENCY CONCEPTS
THE 5-STROKE ENGINE CONCEPT:
Fig.14 A Proposed 5-Stroke Engine
It consists of three cylinders of which two are conventional cylinders and the centre cylinder works based on the two cylinders
It works on the principle of consecutive combustion and exhaust.
The first and the third cylinder work like a normal four-stroke engine whereas the heat from the exhaust is used to drive the centre cylinder.
Estimated Fuel efficiency for these types of engines is up to 30 km/litre in petrol engines.
Fig.15 Gasoline-Electric Hybrid
Gasoline-electric hybrid cars contain the following parts:
Gasoline engine – This is same a conventional engine except that it is much more fuel efficient than others.
Fuel tank – This is mainly used to store gasoline to be used as fuel for the engine
Electric motor – The electric motor on a hybrid car is very sophisticated. It acts a motor as well as a generator.
Generator – It produces the electric power needed for the car to run. Basically it converts DC to AC and delivers it to the electric motors.
Batteries – Battery packs provide the necessary power to the electric motors of the car to function. They are provided with a charging port for easy recharging of the batteries.
Transmission – It is the same as in any conventional vehicle.
SOME LATEST HYBRID CARS:
The first commercial hybrid vehicle.
Has performance equal to that of any normal gasoline vehicle.
Newer versions have very sturdy transmission and breaking systems.
HONDA CIVIC HYBRID:
Almost the same performance as the petrol version of the vehicle.
Effective transmission and engine.
Nearly 40-45 miles per litre of gasoline.
Smooth in handling.
Thus some of the latest developments in green engine concepts and the technologies behind the have been discussed. The uses they provide and the potential behind each technology has also been briefly discussed. Conversion to these types of more “greener” technologies can prove very effective in protecting our planet from global warming and other, more serious issues. Thus I conclude by saying that a greener earth is a cleaner earth and we must all strive in protecting our environment by adopting such useful technologies.
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