English Unit4(1)-1.docx

GASOLINE AND DIESEL ENGINE In theory, diesel engines and gasoline engines are quite similar. They are both internal combus-tion engines designed to convert the chemical energy available in fuel into mechanical energy. This mechanical energy moves pistons up and down inside cylinders. The pistons are connected to a crankshaft, and the up-and-down motion of the pistons, known as linear motion, creates the rotary motion needed to turn the wheels of a car forward. The differences of gasoline and diesel engines : Differences The way explosions happen

Gasoline Engine fuel is mixed with air, compressed by pistons and ignited by sparks from spark plugs

Spark plug Don’t have Compression 14:1 to 25:1 Fuel Gasoline fuel

Diesel Engine the air is compressed first, and then the fuel is injected. Because air heats up when it's compressed, the fuel ignites. Have 8:1 to 12:1 Diesel fuel

1. The way explosions happen. The major difference between diesel and gasoline is the way these explosions happen. In a gasoline engine, fuel is mixed with air, compressed by pistons and ignited by sparks from spark plugs. In a diesel engine, however, the air is compressed first, and then the fuel is injected. Because air heats up when it's compressed, the fuel ignites. Both diesel and gasoline engines convert chemical energy from fuel into mechanical energy through a series of explosions. The way these explosions happen is the major difference between these two engines. 2. Spark plug Diesel engines have no spark plug. They need high compression ratios to generate the high temperatures required for fuel auto ignition (the higher the cetane number, the better the ignition). 3. Compression Compresison is much higher with a diesel engine (14:1 to 25:1) than a gasoline engine (8:1 to 12:1). Gasoline engines use lower compression ratios to avoid fuel auto ignition (engine knock). Higher compression ratios lead to higher thermal efficiencies and better fuel economies. 4. Fuel Diesel and gasoline engines are the major sources of power used in motor vehicles. Both are internal combustion engines but differ fundamentally in terms of their fuel–air mixture preparation and ignition, and the fuels they use: diesel fuel is composed of petroleum fractions with a higher boiling range than those of gasoline.

Diesel fuel is heavier than gasoline (because it’s made up of large molecules). It atomizes differently due to a different density and viscosity. And its flash point and autoignition temperatures are significantly higher. And given these, the converse can also be applied. Gasoline is lighter and flashes at a lower temperature than diesel. Means the diesel fuel will prematurely ignite in the diesel engine, which can lead to engine damage. Gasoline contamination can also damage the fuel pump and mess up diesel injectors. This happens because of a drop in lubrication. Simply speaking, gasoline is a solvent while diesel is an oil.

DIESEL VS GAS | THE ADVANTAGES AND DISADVANTAGES OF GAS/DIESEL ENGINES Gasoline Engine Diesel Engine Low emissions without requiring extensive High thermal efficiency (up to emissions control equipment/devices 30% greater fuel economy) Fuel exhibits high energy Lightweight and comparatively small size content per volumetric unit Generous mid-range and high rpm Flexible air-fuel ratio horsepower/torque Long lifespan, robust engine Capable of operating at high engine speeds components Generates high torque at low Advantages Low service and repair costs engine speeds Attractive cost of ownership/low initial Lack of ignition system purchase cost Engines run cool (rarely Low noise, vibration, and harshness overheat w/ properly maintained cooling system)

Limited lifespan Lower thermal efficiency Detonation (knocking or "ping") becomes Disadvantages serious concern in high compression engines Lower resale value (primarily do to limited lifespan and lower desirability in certain realms) Fuel volatility (greater safety concerns w/ storage and filling)

Relatively large engine size and mass Comparatively high initial purchase cost Comparatively high service and repair costs Fuel dilution is a major concern, not well suited for stop-and-go driving or long periods of idling Limited max engine speed

Extensive, if not somewhat Greater payload (not trailer weight) in truck burdensome emissions control applications do to lower engine weight system (modern engines) Ethanol in gasoline can be detrimental to Not all fuel stations carry diesel fuel systems (Federal mandates in the fuel (although it is not U.S.A. require that all on-highway gasoline particularly difficult to find be blended with ethanol) diesel fuel in any locality)

GASOLINE AND DIESEL FUEL Gasoline Gasoline (American English) or petrol (British English) is a transparent petroleumderived flammable liquid that is used primarily as a fuel in spark-ignited internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Gasoline used in internal combustion engines can have significant effects on the local environment, and is also a contributor to global human carbon dioxide emissions. Gasoline can also enter the environment uncombusted, both as liquid and as vapor, from leakage and handling during production, transport and delivery (e.g., from storage tanks, from spills, etc.). As an example of efforts to control such leakage, many (underground) storage tanks are required to have extensive measures in place to detect and prevent such leaks. Gasoline contains benzene and other known carcinogens. In a gasoline engine, the explosion process is:    

Intake stroke – fuel is mixed with air Compression stroke – piston goes up, mixture of fuel and air is compressed Ignition stroke – fuel/air is ignited through the use of a spark plug Exhaust stroke – piston goes up, pushes exhaust through the exhaust valve

1. Gasoline Terms The following qualities are needed by gasoline to provide soft engine work.  Flammable Simultaneous combustion in the combustion chamber with little knocking.  Volatile Gasoline must be able to form steam easily to provide an air-fuel mixture correctly when turning on the engine which is still cold  No oxidation and cleansing A little change in quality and changes in shape during storage. In addition, gasoline must prevent precipitation in the intake system. 2. Characteristics of a gasoline engine  High speed and great energy  Easy to operate  Perfect combustion  Generally used for passenger cars, small truck vehicles, and so on.

The quality of gasoline can be determined based on the number of beats it causes which is expressed by octane numbers. If gasoline has a high octane value, then good quality gasoline, and vice versa. 3. How to calculate octane values are used two types of compounds, namely :  n-heptane (straight chain alkanes)  isooktana (branch chain alkanes). 4. Advantages  Common fuel (easily available)  More convenient for shorter periods  Starts up immediately  Improves mobility of smaller generating sets  Relatively light compared to diesel generating sets  Quieter engines compared to diesel engines  Longer lifespan of the engine compared to natural gas (dry combustion) 5. Disadvantages  Extremely flammable  Short shelf life: approx. 12 months  Relatively expensive compared to diesel  Higher consumption  Storage of considerable quantities is dangerous. Max. 50L storage is allowed  Possibly unavailable during power failure  Risk of clogging the conduits after long downtime. Gasoline affects the carburetor 6. Apperance  Easily evaporates at normal temperature.  Colorless, translucent, and smelly.  Has a low flash point (-10 to -15 degrees Celsius).  Has a low density (0.71 to 0.77 kg / l)  Can dissolve oil and rubber.  Produces large amounts of heat (9,500 to 10,500 kcal / kg)  Slightly leaving soot after being burned.

Diesel Diesel Used as fuel for diesel engines in motorized vehicles such as buses, trucks, trains and tractors. 1. Producing steam  Seal the industrial output  Burning stone  Do metal heat 2. Requirements for quality of diesel fuel are required as follows.  Flammable  Solar must be able to allow the engine to work softly with little knocking.  Stay watery at cold temperatures (not easy to freeze)  Solar must remain liquid at low temperatures so that the engine will be easily turned on and rotated gently.  Lubrication power Solar also functions as a lubricant for injection pumps and nozzles. Therefore, it must have a good lubricating power.  Solar viscosity Diesel fuel must have adequate viscosity so that it can be sprayed by the injector.  Sulfur content Sulfur damages the use of engine components, and the sulfur content of diesel fuel must be as small as possible.  Stable Does not change in quality, does not easily dissolve during storage. Why Diesel engines are still popular?  The first, the ecological regulations are kept in foreign countries and the owners of ecology-friendly autos have discounts on assurance and other taxes.  Secondly, on condition of quality oil fueling and maintenance on the regular base diesel engine can operate up to half-million kilometers without capital repair. And that is the sure gain.  The third, the turbo-supercharging diesel engine can surely play the role of “firestarter”. Many car manufacturers follow that way. During storage, diesel fuel can be oxidized, become contaminated with harmful impurities and darken. This complicates its use in automobile engines, so this fuel should be subjected to a specific treatment in order to restore its original properties. To solve this problem GlobeCore company has developed and manufactures UVR plants. They allow cleaning and brightening of diesel fuel, as well as removing aromatics mercaptans, hydrogen sulfide, and some sulfur. GlobeCore processes provide an economical solution to the problem of contaminated diesel fuel, which allows full restoration of its properties and ensures a long and reliable service life of engines and fuel systems.

In a diesel engine, the explosion process is:    

Intake stroke – intake valve opens, air in, piston goes down Compression stroke – piston goes up, air compressed (heated in excess of 540°C) Combustion stroke – fuel is injected (right time), ignition, piston goes down Exhaust – piston goes up, pushes exhaust through the exhaust valve

Advantages     

Least flammable, therefore least dangerous Easily available Longer lifespan of the engine compared to natural gas (dry combustion) Relatively cheap, cheaper than gasoline in Europe Possibility to place a bigger external tank, home delivery is possible

Disadvantages       

Short shelf life: 18-24 months Big storage tanks = increased installation costs Possibly unavailable during power failure Not suited for shorter periods Watch out for moisture Heavy It takes a couple of seconds before the chamber where combustion takes place is warmed up enough (preheating)

Apperance Greater power        

High heat efficiency The fuel is efficient The speed is lower than the gasoline engine The vibration is large and rather noisy The price is more expensive More powerful Generally diesel engines are used for long-distance vehicles (commercial vehicles, large trucks, etc.) There are no spark plugs, so there is no possibility of dead spark plugs.

Price Diesel fuel, which is syrup-like compared to watery gasoline, packs more of a punch in terms of energy per unit of weight than gasoline (say, per gallon or liter). So even though it often costs more than gasoline, it contains more potential energy, so less diesel is required in terms of fuel to accomplish the same amount of work (in this case, driving distance) as gasoline. That’s why diesel cars tend to get mileage in the 30s, 40s, or 50s — or more — depending on the engine and vehicle type. In terms of fuel comparative costs, it’s either a wash or a slight advantage for either fuel, depending on the price difference, vehicle, and driving style. But overall, the final cost for using either fuel over time is going to be nearly the same.