What is the ideal Otto cycle?
1. an ideal thermodynamic combustion cycle, as follows: a compression at constant entropy; a constant-volume heat transfer to the system; an expansion at constant entropy; and a constant-volume heat transfer from the system. The thermal efficiency of the ideal Otto cycle increases with an increasing compression ratio.
Which Otto cycle has a compression ratio of 7?
An ideal Otto cycle has a compression ratio of 7, at the beginning of the compression process, P1 =90 kPa, T1 = 27 degree C, and V1 = 0.004 m^3. The maximum cycle temperature is 1127 degree C. For each repetition of the cycle.
Which Otto cycle has a compression ratio of 9?
An ideal Otto cycle has a compression ratio of 9. At the beginning of the compression, air is at 14.4 psia and 120 F. During constant-volume heat addition 450 Btu/lbm of heat is transferred.
What is an ideal Otto cycle with air as the working fluid has a compression ratio of 8?
An ideal Otto cycle with air as the working fluid has a compression ratio of 8. The minimum and maximum temperatures in the cycle are 540 and 2400 R.
What is the compression ratio of an ideal Otto cycle?
9–34 An ideal Otto cycle has a compression ratio of 8. At the beginning of the compression process, air is at 95 kPa and 27°C, and 750 kJ/kg of heat is transferred to air during the constant-volume heat-addition process.
What is the difference between ideal and actual Otto cycle?
Actual Otto Cycle It is assumed that the Ideal cycle is a closed cycle regarding the addition and removal of the mixture. In actuality, the actual cycle is not closed as the mixture is circulated. The gas after compression leaves the system while the new mixture is added. No instantaneous heat addition process.
What is the compression ratio of a cycle?
The compression ratio is defined as the ratio between the volume of the cylinder with the piston in the bottom position, Vbottom (largest volume), and in the top position, Vtop (smallest volume). The higher this ratio, the greater will be the power output from a given engine. It is generally in the 6–10 range.
What is the ratio of Otto cycle?
Thermodynamic analysis of the Otto cycle produces a simple relationship among the thermal efficiency of the Otto cycle ηth, Otto, compression ratio r, and specific-heat ratio k: (3) η th , Otto = 1 − 1 / r k − 1 .
What will happen if compression ratio of Otto cycle increased from 5 to 7?
If the compression ratio of an engine working on Otto cycle is increases from 5 to 7, the % age increase in efficiency will be. 2 %
Why is it not possible to use a high compression ratio in Otto cycle?
In the Otto cycle, the combined air/fuel mixture is compressed, and its temperature rises per the well known gas laws. With excess compression, the temperature will exceed the ignition temperature of the air/fuel mixture, and the energy released by the fuel will work to drive the crankshaft backwards.
What is the compression ratio varies between for Otto cycle?
The compression ratio of Otto cycle is generally 6 to 12 while it is 16 to 25 for Diesel cycles. The lower compression ratio in Otto cycles is due to the reason that increasing the compression ratio will result in hotspots in cylinder that will lead to pre ignition and knocking.
In which cycle is the compression ratio higher?
6 Diesel Cycle (high pressure) when the compression is complete, and there is ignition without a spark. An idealized Diesel engine cycle is shown in Figure 3.12. This cycle can operate with a higher compression ratio than the Otto cycle because only air is compressed and there is no risk of auto-ignition of the fuel.
What is the ideal Otto cycle at the beginning of the compression stroke?
At the beginning of the compression stroke, an ideal otto cycle has an ideal pressure of 15 psia. A temperature of 75degF and a specific volume of 13.2 f t 3 /lbm.
Is the compression ratio of the Otto cycle higher than that of the Diesel cycle?
Internal combustion engines use either the Otto cycle or Diesel cycle. For a given compression ratio, the Otto cycle is more efficient, but Diesel engines generally have higher compression ratios and hence higher efficiencies. The Otto Cycle and a diesel engine.
What is the maximum temperature of the ideal Otto cycle?
An ideal Otto-cycle works between minimum and maximum temperatures of 300 K and 1800 K. What is the compression ratio of the cycle for maximum work output when γ = 1.5 for this ideal gas?
What is the formula for the compression rk ratio of the Otto cycle?
THE FORMULA FOR COMRESSION (rk) RATIO PG OTTO CYCLE IS rk=COMPRESSION RATIO =Vmax/Vmin. Explanation: otto cycle describes us about the thermal efficiency using compression ratio.
What is meant by compression ratio?
It is defined as the maximum volume of the combustion chamber (with the piston farthest out, or bottom dead centre) divided by the volume with the piston in the full-compression position (with the piston nearest the head of the cylinder, or top dead centre).
What is the air standard efficiency of the Otto cycle?
The air standard efficiency of an Otto-cycle is given by the expression n a = 1 − 1 ( R e ) n Where Re is the compression ratio, The value of ‘n’ in this equation is.
What is the difference between ideal Otto cycle and Carnot cycle?
The reversibility of the Carnot Cycle makes it the most efficient thermodynamic cycle to convert energy as heat into work operating between two thermal reservoirs at different temperatures. The Otto cycle represents an idealization of the processes in the spark-ignition 4-stroke internal combustion engine operation.
Is the ideal Otto cycle reversible?
Whereas in Ideal Otto cycle processes are Only internally reversible as there is no any internal entropy generation due to friction and reversible adiabatic compression and expansion.
What is the difference between an ideal cycle and an actual cycle?
There are many difference between these two as following : Working fluid considered as air in air standard cycle but in actual there is always mixture of air and fuel. Because of air is considered as constant there is heat capacity value like Cp & Cv are standard for air but it changes in actual cycle.
What is the ideal compression ratio?
The ideal compression ratio for a naturally aspirated engine is typically between 8:1 and 10:1. This range of compression ratios allows the engine to produce enough power to be useful, while still maintaining good fuel economy. Higher compression ratios can produce more power, but may sacrifice fuel economy.
What is a good compressor compression ratio?
In air conditioning applications, compression ratios of 2.3:1 to 3.5:1 are common, with ratios below 3:1 and above 2:1 as the standard for modern high-efficiency air conditioning equipment. In a 404a medium-temp refrigeration (cooler) application, 3.0:1 – 5.5:1 is a common ratio range.
How to find compression ratio?
By definition, the compression ratio is the total swept volume of the cylinder with the piston at bottom dead center (BDC), divided by the total compressed volume with the piston at top dead center (TDC).
Is Otto’s cycle an ideal cycle?
An Otto cycle is an idealized thermodynamic cycle that describes the functioning of a typical spark ignition piston engine. It is the thermodynamic cycle most commonly found in automobile engines.
Is compression ratio equal to expansion ratio in Otto cycle?
The P-V and T-S diagram of the otto cycle is shown below. The compression ratio is given by the ratio of volume before compression to volume after compression. The expansion ratio is given by the ratio of volume after expansion to the volume before expansion. Hence, Compression ratio = Expansion ratio.
Why does the Otto cycle have less compression ratio than the diesel cycle?
At high pressure, fuel is sprayed into the cylinder. When the compression is complete, there is an ignition without a spark. A diesel cycle can operate with a higher compression ratio than an Otto cycle as there is no risk of auto-ignition of the fuel and only air is compressed.
What is the standard Otto cycle?
An air standard Otto cycle has thermal efficiency of 0.5 and the mean effective pressure of the cycle is 1000 kPa. For air, assume specific heat ratio γ = 1.4 and specific gas constant R = 0.287 kJ/kg.
What is an ideal Otto cycle with 15% clearance?
An ideal Otto cycle engine with 15% clearance operates on 0.227 kgm per second of air; intake state is 100.58 kPa and 37.7 degree Celsius. The energy released during combustion is 100 kiloJoules per second.
What is Otto cycle of ideal gas?
On this page we have shown an ideal Otto cycle in which there is no heat entering (or leaving) the gas during the compression and power strokes, no friction losses, and instantaneous burning occurring at constant volume. In reality, the ideal cycle does not occur and there are many losses associated with each process.
What is the ideal cycle?
Ideal cycles are simplified thermodynamic closed cycles to analyze the compression, combustion, and expansion process in an engine with a focus on extraction of work from combustion of the fuel–air mixture.
What is the compression ratio of an Otto cycle?
What is an ideal Otto cycle?
What is an ideal Otto cycle with air as a working fluid?
What is the mean effective pressure value for the Otto cycle?
An Ideal Otto Cycle Has Compression: Why It Matters
So, what exactly is an Otto cycle? Well, it’s basically a model of how a spark-ignition internal combustion engine works. Think of it like a blueprint for how your car engine takes fuel, burns it, and turns that energy into motion. The Otto cycle has four main strokes:
1. Intake Stroke: This is where the engine sucks in a mix of air and fuel.
2. Compression Stroke: Here’s where things get interesting. The piston moves up, squeezing the air-fuel mixture, making it denser and hotter. This compression is key to the whole process.
3. Combustion: A spark ignites the compressed air-fuel mixture, causing a rapid expansion of hot gases.
4. Exhaust Stroke: The piston pushes out the burnt gases, getting ready for the next cycle.
Why Compression Is King
The compression ratio in an Otto cycle is super important. It’s the ratio of the volume of the cylinder at the start of the compression stroke to the volume at the end. A higher compression ratio means the air-fuel mixture gets squeezed more tightly.
Let’s break down why this matters:
* More Power: The more you compress the air-fuel mixture, the hotter it gets. This leads to a bigger bang when it explodes, giving you more power. Think of it like a pressure cooker – the more pressure you build up, the more intense the explosion.
* Better Efficiency: With higher compression, you get a better burn of the fuel, leading to less energy wasted. It’s like squeezing a sponge – the tighter you squeeze, the more water you can extract.
The Ideal Otto Cycle: Where Compression Shines
Now, in an ideal Otto cycle, we assume things work perfectly. No friction, no heat loss, just pure, beautiful physics. In this perfect world, a higher compression ratio means:
* Higher thermal efficiency: The engine converts more heat energy into mechanical energy, meaning more power output for less fuel.
* Increased work output: The explosion of the compressed air-fuel mixture pushes the piston with more force, resulting in more work done by the engine.
But It’s Not All Sunshine and Roses
While a high compression ratio sounds great, there are some downsides:
* Knocking: If the compression is too high, the air-fuel mixture can explode prematurely, causing a loud knocking sound. This is bad for your engine, so you have to be careful.
* Increased stresses: Higher compression means more pressure on the engine parts, which can lead to wear and tear over time.
Balancing the Act: Finding the Sweet Spot
So, how do you find the perfect balance? It’s all about finding the sweet spot between power, efficiency, and durability.
* Fuel quality: Higher compression often requires higher-octane fuel to prevent knocking.
* Engine design: Modern engines are designed with stronger materials and better cooling systems to handle the stress of higher compression.
FAQs
What is the difference between the Otto cycle and the Diesel cycle?
The Otto cycle uses spark ignition to ignite the air-fuel mixture, while the Diesel cycle uses compression ignition. Diesel engines have much higher compression ratios than Otto cycle engines, allowing them to ignite the fuel simply by compressing it.
Can you improve the compression ratio of an existing engine?
You can, but it’s usually not recommended. Modifying an engine’s compression ratio requires specialized knowledge and equipment, and can potentially damage the engine if done incorrectly.
Is a higher compression ratio always better?
Not necessarily. It depends on the specific application and the design of the engine. Higher compression ratios can be beneficial in some cases, but they also come with potential drawbacks.
What are some examples of engines with high compression ratios?
Many modern high-performance gasoline engines have compression ratios above 10. Some examples include Formula One engines, sports cars, and turbocharged engines.
Alright, that’s a quick rundown on the Otto cycle and the importance of compression. Keep in mind, this is just a simplified explanation. There’s a whole lot more to learn about internal combustion engines and their complexities. But hopefully, this gives you a good starting point.
See more here: Which Otto Cycle Has A Compression Ratio Of 7? | An Ideal Otto Cycle Has A Compression
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The ideal Otto cycle efficiency is shown as a function of the compression ratio in Figure 3.11. As the compression ratio, , increases, increases, but so does . If is too high, the mixture will ignite without a spark (at the wrong MIT – Massachusetts Institute of Technology
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