TWO STROKE DIESEL ENGINE
Working of two-stroke diesel engine:
1. Compression Stroke: During
the compression stroke, the air (or a mixture of air and fuel, depending on the
engine design) is compressed inside the cylinder as the piston moves upward.
The compression increases the air pressure and temperature, preparing it for
combustion.
2. Power Stroke: At the
end of the compression stroke, fuel is injected directly into the highly
compressed air inside the cylinder. The fuel ignites spontaneously due to the
high temperature and pressure, causing a rapid expansion of gases. This sudden
expansion forces the piston down the cylinder, converting the pressure energy
into mechanical work. This downward movement of the piston is the power stroke,
which drives the crankshaft and provides power to the engine.
Unlike four-stroke engines, two-stroke diesel engines do not have separate
intake and exhaust strokes. Instead, they rely on ports and valves to control
the flow of gases in and out of the cylinder. These engines generally have
simpler construction and fewer moving parts, which can make them lighter and
more compact.
Two-stroke diesel engines were more common in the past, but they have
become less prevalent due to some inherent drawbacks. They tend to produce more
exhaust emissions, have lower fuel efficiency, and are typically noisier
compared to four-stroke engines. Additionally, modern emission regulations and
environmental concerns have led to a decline in their use.
However, two-stroke diesel engines are still employed in certain
applications, especially in large marine engines, locomotives, and certain
industrial settings, where their specific advantages may outweigh their
drawbacks. Research and development efforts continue to improve their
efficiency and reduce emissions, keeping them relevant in specific niches of
the engine market.
ADVANTAGES OF TWO STROKE DIESEL ENGINE
1. Simplicity and Fewer Moving Parts: Two-stroke diesel engines have a simpler design with fewer moving
parts compared to four-stroke engines. This simplicity can lead to lower
manufacturing costs and easier maintenance.
2. Higher Power-to-Weight Ratio: Due to their reduced parts and lighter construction, two-stroke
diesel engines tend to have a higher power-to-weight ratio. This makes them
well-suited for applications where a high power output in a compact and lightweight
package is essential, such as in certain marine and locomotive applications.
3. Higher Power Density: Two-stroke diesel engines can achieve a higher power output per unit
of displacement compared to four-stroke engines. This means they can produce
more power from a smaller engine size, which can be advantageous in
space-constrained environments.
4. Higher Torque at Low RPM: Two-stroke diesel engines typically produce higher torque at low RPM
(revolutions per minute), which can be beneficial for certain heavy-duty
applications that require high starting torque or constant low-speed operation.
5. Simpler Exhaust System: Since there is no separate exhaust stroke in a two-stroke engine, it
requires a simpler exhaust system, reducing complexity and potential points of
failure.
6. Fewer Cooling Requirements: Two-stroke diesel engines have better cooling characteristics due to
the continuous supply of fresh air with each revolution. This can lead to
reduced cooling requirements and improved engine thermal efficiency.
7. Compact and Lightweight: The absence of additional valve mechanisms and reduced parts make
two-stroke diesel engines more compact and lighter than their four-stroke
counterparts, making them suitable for specific applications where space and weight
are critical factors.
8. Lower Cost and Maintenance: The simplicity of two-stroke diesel engines often translates to lower
manufacturing costs and reduced maintenance requirements, which can be
advantageous in certain industries and regions where cost is a significant
consideration.
DISADVANTAGES OF TWO STROKE DIESEL ENGINE
Two-stroke diesel
engines, despite their advantages in certain applications, also come with
several disadvantages, which have contributed to their declining popularity in
many modern automotive and industrial settings. Here are some of the key
disadvantages of two-stroke diesel engines:
1. Higher Emissions: Two-stroke diesel engines tend to produce
higher emissions, particularly of harmful pollutants such as unburned
hydrocarbons, carbon monoxide (CO), and particulate matter. These emissions can
have adverse effects on air quality and contribute to environmental pollution.
2. Lower Fuel Efficiency: Compared to four-stroke diesel engines, two-stroke
engines generally have lower fuel efficiency. Some of the incoming fuel mixture
can escape through the exhaust port before being fully burned, leading to
wasted energy and reduced efficiency.
3. Increased Oil
Consumption: Two-stroke diesel
engines require lubricating oil to be mixed with the fuel for proper
lubrication of engine components. This oil consumption leads to higher
maintenance costs and contributes to emissions.
4. Noise and Vibration: Two-stroke diesel engines are known for being
noisier and producing more vibrations compared to four-stroke engines. The
rapid and frequent firing of the engine can cause significant noise and
vibration levels, making them less suitable for noise-sensitive applications.
5. Poorer Reliability and
Durability: The increased
number of power strokes in a two-stroke engine can subject engine components to
higher stresses and wear, potentially leading to reduced reliability and
shorter engine life compared to four-stroke engines.
6. Thermal Efficiency
Limitations: The two-stroke
cycle inherently has less time for fuel-air mixing and combustion than the
four-stroke cycle. This limits the engine's ability to optimize fuel-air ratios
and can negatively impact thermal efficiency.
7. Smoky Exhaust: Due to incomplete combustion, two-stroke
diesel engines often produce smoky exhaust, which not only contributes to air
pollution but can also create visibility issues in certain applications.
8.Oil-Fuel Mixture Handling: Mixing lubricating oil with the fuel can be cumbersome, and maintaining the right oil-to-fuel ratio is crucial for proper engine operation. Incorrect mixture ratios can lead to engine performance issues and increased emissions.
9.Environmental
Concerns: The higher emissions
and lower fuel efficiency of two-stroke diesel engines have raised
environmental concerns, leading to stricter emission regulations in many
regions, which further limits their use in certain applications.