Diesel Engine Basics
A diesel engine is an internal combustion engine that uses compression ignition to ignite the fuel as it is injected into the engine.
DIESEL ENGINES VS. GASOLINE ENGINES
It is helpful to an understanding of how diesel engines work to compare the differences between a diesel engine and a gasoline engine. The main differences between a gasoline engine and a diesel engine are:
A gasoline engine takes a mixture of gas and air, compresses it, and ignites the mixture with a spark. A diesel engine takes air, compresses it, and then injects fuel into the compressed air. The heat of the compressed air ignites the fuel spontaneously. A diesel engine does not contain a spark plug.
A gasoline engine compresses at a ratio of 8:1 to 12:1, while a diesel engine compresses at a ratio of 14:1 to as high as 25:1. The higher compression ratio of the diesel engine leads to better efficiency.
Gasoline engines generally use either carburetion, in which the air and fuel are mixed long before the air enters the cylinder, or port fuel injection, in which the fuel is injected just prior to the intake stroke (outside the cylinder). In a gasoline engine, therefore, all of the fuel is loaded into the cylinder during the intake stroke and then compressed. The compression of the fuel/air mixture limits the compression ratio of the engine – if it compresses the air too much, the fuel/air mixture spontaneously ignites and causes knocking. Diesel engines use direct fuel injection i.e. diesel fuel is injected directly into the cylinder. A diesel engine compresses only air, so the compression ratio can be much higher. The higher the compression ratio, the more power generated.
Diesel fuel injectors, unlike gasoline injectors, must be able to withstand the temperature and pressure inside the cylinder and still deliver the fuel in a fine mist. To ensure that the mist is evenly distributed throughout the cylinder, some diesel engines are equipped with special induction valves or pre-combustion chambers. Newer diesel engines are equipped with high-pressure common rail fuel systems. See Diesel Fuel System Basics for more information on this type of fuel system.
Diesel engines may be equipped with a glow plug. When a diesel engine is cold, the compression process may not raise the air temperature high enough to ignite the fuel. The glow plug is an electrically heated wire that facilitates fuel ignition when the engine is cold. Glow plugs are typically found on small diesel engines. Gasoline engines do not require glow plugs as they do not rely on spontaneous combustion.
Working Principle of Diesel Engine Cooling System
This post will introduce the working principle and components of diesel engine cooling system in detail. It is worth taking a few time to read it.
Diesel engines are heat-generating sources. They are cooled by circulating a water-based coolant through a water jacket, which is part of the engine. The coolant is circulated through pipes to the radiator to remove the heat added to the coolant by the engine and then back to the engine.
The typically components of the cooling system are:
1. Water pumps
2. Heat removing device (radiator or heat exchanger)
3. Coolant expansion tanks (surge tanks)
4. Temperature control valves
5. Temperature and pressure switches and indicators
Please note that the engine water cooling systems are either closed or open systems. Closed system is designed to use the same coolant with a closed circuit, preventing the losses of the coolant. While the open system uses the coolant once and discharges it or recirculates the coolant through systems, which cool the coolant by evaporation. Most of the stationary diesel engines use closed systems to control the chemistry of the coolant to prevent fouling of heat transfer surfaces and to closely control the temperatures.
In general, diesel generator cooling system has the following functions:
1. Cooling the engine cylinders via water jacket
2. Cooling the lube oil via lube oil cooler
3. Cooling combustion air via after cooler on turbo-charged engines
Although there are various types of pumps used in diesel engine cooling systems, two pumps are often used for two circuits systems. One is Engine driven pump, the other is electrical driven pump (It is used to circulate the coolant to keep the engine warm when the engine is not running.)
A high-powered diesel engine is very hard on the coolant. Additive-depleted coolant will not only allow liner cavitation but cause premature failure of the head gaskets, radiator, water pump, freeze plugs, heater core and thermostat.
Many diesel engines issues are caused by lacking proper maintenance.
First, check the additive level should be a part of maintenance schedule. Since the diesel engines have such a large liquid capacity, cooling system test strips are offered to check the level of additives. If the level is low, a bottle of SCA can be mixed in to renew the coolant without a complete change.
Second, when you are going to buy coolant, make sure it is compatible with a diesel engine, not automotive or light-truck use, which means gasoline powered.
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Understanding The Basics Of Diesel Fuel Systems
Oil derivatives are the dominant source of fuel for transportation systems. You have probably seen news coverage of “hydrogen” and “electric” powered vehicles, but these sources are still very much in their infancy. Gasoline is the primary fuel source for cars, trucks, and other passenger vehicles, but regular gasoline systems are not the only systems available. Diesel systems are the preferred types for commercial vehicles, cargo ships, and trains.
In theory, gasoline and diesel fuel systems are remarkably similar. They are both internal combustion engines and they both convert chemical reactions into mechanical energy. Both systems use a series of pistons to compress fuel and air before igniting it. The difference between the two systems is how energy is created within them.
In a gasoline engine, gas and air are mixed then compressed and ignited with sparks from the spark plug. In a diesel engine, air is compressed and then the gasoline is introduced. When the air is compressed, it heats up and the compressed air ignites the gas.
The differences between gasoline and diesel fuel systems do not stop at the combustion methods. Both systems also use entirely different fuels. Diesel is heavier and oilier than gasoline, so it evaporates more slowly. Additionally, diesel emits fewer compounds that are associated with global warming, like CO2 and methane. However, diesel fuel does emit more nitrogen compounds, which is associated with acid rain and smog.
Since diesel engines mix in the fuel after the air is compressed, they are able to exercise more control over how much is utilized. In fact, these engines are considered one of the most fuel-efficient transportation systems. This is why vehicles with diesel systems dominate the commercial and freight industries.
The components of diesel fuel systems
A basic diesel fuel system is made up of five essential components. These are the tank, the fuel transfer pump, filters, the injection pump, and the injection nozzles.
The fuel tanks in diesel systems are typically crafted from aluminum alloys or sheet metal. The tanks are designed to contain the diesel fuel and survive its long-term corrosive effects.
The transfer pump sucks the diesel fuel out of the tank to move it into the injection pump. The transfer pump is generally located outside of the fuel tank or on the rear of the injection pump. In a few situations, transfer pumps are also located within the tank.
Diesel, like gasoline, is always mixed with contaminants that can damage the combustion system. The fact that diesel is refined, stored, transported on trucks, then stored again at gasoline stations ensures that contaminants will enter the fuel. To address these concerns, filters are placed between the transfer pump and injection system. The filter removes dirt and other contaminants that could easily damage the fuel injection system.
The injection pump compresses the fuel in preparation for injection. Injection nozzles spray diesel into the combustion chamber of the cylinders. The combustion chamber enables the car to convert the miniature combustions (explosions) into mechanical energy that turns the vehicle’s wheels.
At Kendrick Oil, we distribute a wide variety of wholesale fuels, including diesel and regular gasoline. If your business is in need of wholesale fuel or if you want to learn more about any of our products and services, give us a call at (800) 299-3991. You can also Contact Us by email for details. We have locations in Texas, New Mexico, Oklahoma, and Kansas.
Charge Air Cooling
In modern engines, it is also important to ensure the temperature of the charge does not become excessive. In modern boosted engines, this is a real possibility. Excessive temperatures can lead to reduced charge density and higher combustion temperatures which can affect torque, power and emissions.
While turbochargers and superchargers increase charge air density, they also increase the temperature of the air in the intake manifold. This arrangement with intake air compression with no subsequent cooling was suitable for applications such as North American heavy-duty diesel engines until the 1990s. As emission standards became increasingly stringent, additional increases in charge air density were needed. While this could be achieved through compression to higher pressures, this would require more expensive compression equipment and would further increase cycle temperatures. On the other hand, if intake manifold temperature could be reduced, the intake density could be further increased and more air could be supplied to the engine without necessarily increasing the intake manifold pressure. While this would require a compressor capable of higher flow, the cost would be considerably less than a compressor that was also capable of higher pressures. Cooling the air with a heat exchanger as it leaves the compressor is a common way to achieve this charge air cooling. Such a heat exchanger is referred to as a charge air cooler (CAC), intercooler or aftercooler (Figure 1). These terms are commonly used interchangeably. The term intercooler refers to the fact that this heat exchanger performs its task in between two stages of compression, i.e., between compression in the compressor and compression in the cylinder of the engine. The term aftercooler refers to the charge air being cooled after being compressed in the compressor. Increasing demand for improvements in fuel economy and exhaust emissions has made the charge air cooler an important component of most modern turbocharged engines.