Low Pollution Alternate Fuel Vehicles

Isuzu is developing low-pollution vehicles using alternative energy sources or hybrid systems to reduce emissions. Such vehicles are not only a vital step toward achieving lower emissions of pollutants, they will also contribute to the more effective utilization of limited resources.

Compressed Natural Gas (CNG) Vehicles

The CNG-powered engines emit very low NOx carbon monoxide (CO) and hydrocarbons (HC) and virtually no particulate matter (PM) at all. Another characteristic of natural gas, of which the main constituent gas is methane, is that it produces very little CO. Isuzu produces three-way catalytic converter-equipped CNG vehicles that achieve an excellent low-pollution emission performance. CNG (Compressed Natural Gas) is available from the significant reserves of natural gas that exist in many places around the world. Unlike in the case of petroleum, the bulk of supplies are not concentrated in the Middle East and reserves of natural gas are considered to be much larger than those of petroleum. Accordingly, this fuel has an important role in maintaining a stable supply of energy.

ELF CNG-MPI (Multi Point Injection) [Advantages]Zero PM emission Low NOx emission Very low CO emission  [Disadvantages]Short running distance Heavy fuel container

Dimethyl Ethel Engine (DME) Vehicles

With various advantages, The DME engine is getting wide recognition as a next generation, alternative-fuel powerplant. DME emits no black smoke and very little PM and Nox. Dimethyl Ether is made from charcoal and natural gas. It is very stable fuel which can be liquified under normal temperatures at low atmosperic pressure. Easy transportation and storage is also its advantage.

[Advantages] Zero PM emission and black smoke Very low Nox emission Good fuel economy equivalent to diesel engine Easy handling [Disadvantages] Shorter running distance than diesel engine Unsufficient Infrastracture

Diesel Hybrid Vehicles

Hybrid vehicles are designed to realize low pollution and energy saving by dual power sources. Isuzu's Elf diesel hybrid achieves low-CO emission levels and high fuel efficiency by fully extracting energy available when the vehicle decelerates. It uses diesel for fuel, needs no special infrastructure, and can be serviced anywhere. In addition, the Elf Diesel hybrid truck employs Isuzu's original hybrid system, which was optimized for light-duty trucks. The system achieves excellent fuel economy compared to other hybrid vehicles, and delivers the high durability and safety performance required by commercial vehicles at the same time. The Elf diesel hybrid truck has the following features: •  The hybrid system is based on the 4HL1 diesel engine. In addition to assisting the engine by adding an electric motor, the Smoother-E automatic shift system allows high-efficiency regenerative energy and automatic shifting in fuel-saving speed ranges. •  For the first time on a domestic truck, a Lithium-ion battery is used that provides approximately 3 times longer life than a nickel metal hydride battery. •  A PTO-type parallel drive hybrid system is employed, so that even if a failure occurs in the hybrid system, the motor and generator being installed on a shaft different from that of the engine, driving can be continued on just the diesel engine, without interference to the engine driveline.

ELF Diesel Hybrid [Advantages] Improved fuel consumption resulting in lower CO emissions Reduced exhaust emissions during start up and acceleration [Disadvantages] Complex systems and high maintenance costs

When starting and accelerating, or when the engine is under a heavy load, the vehicle runs on both the engine and electric motor using battery power

Vehicle runs as a fuel-efficient diesel engine during constant-speed runs only. The Smoother-E automatic shift changes speeds automatically for optimum fuel economy.

When decelerating, Smoother-E automatic shift automatically disengages clutch to prevent loss of regenerative energy, charging on battery efficiently.

After stopping, moving the shift lever into the N position will stop the engine automatically. Moving the lever to D restarts the engine. Gas emission is reduced, while fuel economy is improved at the same time.

Fuel Cell Vehicles

Fuel cell vehicles are highly advanced low-pollution vehicles that generate electricity through a chemical reaction between hydrogen and oxygen and use this electricity to drive a motor. R&D is currently proceeding into a system for storing hydrogen in a special alloy and a system utilizing methanol. Fuel cells are highly fuel-efficient, so they are considered as the next-generation of vehicle powerplants.

When water is electrolyzed it is split into hydrogen and oxygen. The principle of the fuel cell is based on the reversal of this reaction.

CO2 Reduction Technologies

Diesel Engine Combustion Systems

The quality of combustion in diesel engines depends on how quickly and how completely the fuel mixes with the air as it is injected into the combustion chamber. Two basic systems have been devised to improve this mixing: direct-injection and indirect-injection.

Direct-Injection

The direct-injection system introduces the fuel directly into the combustion chamber. Direct-injection promotes good fuel economy, but the air swirling is not strong enough to achieve an ideal mixture with the fuel. This weakness is overcome with specially designed chambers and air-intake ports, and by the use of high-pressure fuel injection. Direct-injection diesel engines are gathering increasing popularity. They are now used in nearly all trucks with payloads of four tons or more and also in a significant proportion of passenger cars in Europe. The most popular form of direct-injection system provides a strong swirl of air in the combustion chamber to aid the air-fuel mixing process, with the fuel being injected under high pressure from four or five nozzle holes.

Advantages Minimized surface area raises thermal efficiency and reduces heat loss, resulting in good fuel economy. Simple cylinder head design is durable and reliable, partly because it is largely unaffected by heat or pressure distortion. Engine starts easily, and preheating with a glow plug is not necessary.  Disadvantages Current designs produce more NOx emissions than indirect-injection systems. Not ideally suited to high-revolution vehicles (passenger cars) due to difficulties in creating an ideal swirl.

Indirect-Injection

The indirect-injection system is currently limited to use in passenger cars and light-duty trucks. The most popular design features a spherical swirl chamber in the cylinder head. Air is forced into the chamber by the piston and begins swirling rapidly, which promotes a good mix when the fuel is injected. A preliminary combustion of the mixture takes place and heat rises, forcing the remaining unburned fuel into the chamber at high velocity, where it mixes well with the air and undergoes complete combustion.

Advantages Suitable for fast engine speeds with high rpm. Less vibration and noise.  Disadvantages Additional chamber adds to design cost. Greater surface area leads to heat loss and reduced fuel economy. Higher temperature operation wears out parts faster.

Intercooler-Equipped Turbocharger

Turbocharger

A turbocharger is a mechanism that increases the amount of air supplied to an internal combustion engine at higher than normal pressure by means of a turbine powered by the exhaust gases. By allowing more air to enter the cylinder while maintaining the exhaust amount at the same level, a turbocharger can improve combustion efficiency and improve the power output.

Intercooler

An intercooler is a device that cools the supplied air, which is heated to a high temperature upon being compressed in the turbocharger. Then, it will send the cool high-density air to the cylinder.

Advantages of Turbo-Charged Engines The turbocharger can supply large displacement to the cylinder, so that a high level of output can be obtained with a small exhaust volume. Achieving high power with a small exhaust volume means that the engine's weight and size can be made smaller, and this translates into a lighter vehicle weight and improved fuel efficiency. Moreover, a turbo-charged engine can generate 20% to 50% more torque* compared to a non-turbo-charged engine with the same displacement. These advantages make turbo-charged engines ideal for vehicles used for long-distance, high-speed transportation. On the other hand, non-turbo-charged engines feature high levels of torque in the low speed range, which gives them a better startup and acceleration performance and makes them suitable for vehicles used mainly for city driving involving repeated starting and stopping. In recent years, turbo-charged engines are getting more popular for their high fuel economy and remarkable power performance. * Torque Torque is the rotational force generated by the movement of the crankshaft. The unit of torque is the Newton meter (Nm) or the kilogram meter (kgm). In principle, the higher an engine's combustion power, the greater the amount of torque it generates. For example, if a one-meter-long arm is fixed at right angles to a shaft and a 1kg weight is set at the tip, the force exerted on the shaft is 1Nm (1kgm).

Diesel Engines and Gasoline Engines

Diesel engines possess a diversity of features that other internal combustion engines can't match. The advantages of diesel include good thermal efficiency that translates into relatively low CO emissions, as well as powerful torque even at low speeds and high durability.

In his 1892 thesis concerning the "Theory and structure of a rational thermal engine that should replace the steam engines and internal combustion engines known today", Rudolf Diesel, the diesel engine's inventor in Germany, described the new engine's basic principles. These are: (1) at first only air is fed into the combustion chamber, then the fuel is sprayed in after the air is compressed; and (2) the air compression ratio is set high so that the air temperature becomes much higher than the combustion point of the fuel.

Diesel engines operate on a self combustion or compression combustion system that does not require ignition plugs and a non-uniform mixing method in which the air and fuel are sent separately into the combustion chamber where they mix together and spontaneous combustion takes place.

Exhaust emission levels are very different between diesel engines and gasoline engines. Diesel engines emit higher levels of nitrogen oxides (NOx) and particulate matter (PM) than gasoline engines.

Item Diesel Gasoline Exhaust emissions NOx - Better PM - Better CO (fuel consumption related) Better - Others Noise level - Better Engine torque Better - Durability Better -

Characteristics of Diesel Emissions

Among the substances contained in exhaust emissions, those that have particularly impacts on the environment are carbon dioxide (CO), carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx) and particulate matter (PM). Especially CO, PM and NOx are attracting serious attention, and a variety of technologies have been developed in order to reduce their generation.

CO (Carbon Dioxide)

What is CO?

CO or carbonic acid gas is colorless odorless gas present naturally in the air. The concentration of CO is increasing due to the combustion of fossil fuels and the cutting of tropical rainforests. It is important to conserve fossil fuels as much as possible in order to reduce the amount of CO generated. Vehicles with good fuel consumption emit lower COWhat happens when the atmospheric CO level rises?

Its connection with global warming is most worried. As the average temperature rises, sea levels rise and abnormal climates occur more frequently. The effects of these changes on people around the world are very serious.

PM (Particulate Matter)

What is PM?

PM is a general term for the various kinds of particulate matter emitted by diesel and other engines. This matter consists mainly of soot, half-combusted fuel particles, a lubricated oil component called SOF (Soluble Organic Fraction), and sulfates generated from the sulfur contained in the light oil fuel. PM also includes SPM*, which consist of particularly small particles.

What happens when PM emissions increase?

PM is one of the airborne pollutants that has a direct effect on human health. Breathing in large amounts of PM can result in respiratory problems or chronic lung disease.

* SPM (Suspended Particulate Matter): Among the PM present in engine exhaust gas, those with diameters of less than 10 microns are categorized as SPM. Environmental standards stipulate maximum SPM emission levels.

NOx (Nitrogen Oxides)

What is NOx?

NOx is a general term for a variety of chemical compounds formed in reactions between nitrogen and oxygen at high temperatures. The amount of NOx generated increases as combustion becomes more complete, so to reduce NOx generation the temperature of the reaction must be lowered. This fact makes it difficult to reduce NOx and PM generation simultaneously.

What happens when NOx emissions increase?

NOx is a major cause of photochemical smog and acid rain. It has a huge influence on natural eco-systems by damaging forests and acidifying lakes and marshes. In large cities, high local NOx concentrations may have negative effects on the human respiratory system.

Features of Diesel Engines

	Fuel: Diesel light oil
	Fuel supply system: High-pressure direct injection into cylinder via fuel pump
	Air-fuel mixing: Non-uniform mixing
	Ignition system: Compression-induced spontaneous combustion
	Compression ratio: 15.5-23
	Output control system: Controlled exclusively by fuel injection amount (fixed intake air amount, mixing ratio control)

Combustion In diesel engines, air is drawn into the cylinder and highly compressed, after which fuel is sprayed into the cylinder under high pressure. Ignition occurs spontaneously as a result of the high temperature generated through compression. Thermal Efficiency Ratio of heat converted into power against total heat generated during combustion Diesel Engines Feature High Thermal Efficiency Thermal Efficiency Ratio=Ratio of heat converted into motive power: 35-42%

CO Diesel engines' high thermal efficiency translates into low fuel consumption. 20-40% lower than gasoline engines Durability Working life of 300,000 - 1,000,000 km or more (from car-mounted engine data) Performance Diesel engines generate flat torque from the low speed range, so diesel vehicles are easy to drive.

Based on in-house data

Features of Gasoline Engines

	Fuel: Gasoline
	Fuel supply system: Carburetor or low-pressure intake-pipe fuel injection system
	Air-fuel mixing: Pre-injection uniform mixing
	Ignition system: Spark ignition
	Compression ratio: 8-10.5
	Output control system: Suction mixture air amount control via throttle valve (fixed mixing ratio)

Combustion In gasoline engines, air and fuel are mixed in advance and then drawn into the cylinder and compressed. The compressed mixture is ignited by an ignition plug. Thermal Efficiency Ratio of heat converted into power against total heat generated during combustion Thermal Efficiency Ratio=Ratio of heat converted into motive power: 25-30%

CO Since gasoline engines have a lower thermal efficiency than diesel engines, their CO exhaust amount is correspondingly greater. Durability Working life of 100,000 - 300,000 km or more (from car-mounted engine data) Performance Gasoline engines generate torque during high-speed rotation.

Source: ISUZU