combustion engine. Discuss the thermodynamics of the Otto cycle for a combustion engine. Why does the...

combustion engine.

Discuss the thermodynamics of the Otto cycle for a combustion engine.

Why does the efficiency depend on the compression ratio?

What is the problem with that? Why is the Otto cycle better than a steam engine? Or, what is the main innovation

Expert Solution

Thermodynamic Cycles used in internal combustion gasoline powered engines. The first such engine was built by the German engineer Otto in 1861. The Otto cycle consists of four strokes of the piston for each explosion.

1. Intake stroke. A mixture of air and gasoline is drawn into the cylinder.
2. Compression stroke. The fuel-air mixture compressed, causing a rise in temperature.
3. Explosion. The mixture is ignited by spark plugs with the piston staying nearly fixed, leading to a rise in pressure and temperature.
4. Power Stroke. The hot gas is then allowed to do mechanical work by pushing the piston back.
5. Valve exhaust. An outlet valve is opened and some exhaust escapes with the piston remaining fixed.
6. Exhaust stroke. The piston forces the remaining exhaust to escape. The outlet valve is then closed, the inlet valve opened, and the cycle repeats.

The Otto cycle's efficiency is 1 - r^(1-k), where r is the compression ratio and
k is the specific-heat ratio (always > 1), so efficiency improves when r is large.
However, the possibility of "knocking" limits the compression ratio in a
spark-ignition engine.

queen_honey_blossom answered 2 years ago

The cycle involved in the operation of an internal combustion engine is called the Otto cycle....

The cycle involved in the operation of an internal combustion engine is called the Otto cycle. Air can be considered to be the working gas and assumed perfect. The cycle consists of the following steps. reversible adiabatic compression from A to B reversible constant volume pressure increase from B to C (from the fuel combustion) reversible adiabatic expansion from C to D reversible constant volume pressure decrease from D to A Determine an expression for the efficiency of this engine...

Thermodynamics problem: An engine operates on an air-standard Otto cycle. The pressure and temperature of the...

Thermodynamics problem: An engine operates on an air-standard Otto cycle. The pressure and temperature of the isentropic compression 100 kPa and 40 °C, respectively. The pressure at the end of compression is 2.0 MPa and the net work is 87,000 J/mol. Assume ideal air-standard cycle. Determine the following: pressure, volume, and temperature at end of each step. compression ratio. heat input and heat rejected per mol of working fluid. thermal efficiency of the cycle.

Consider an automobile engine which operates on the ideal Otto cycle. In this engine, air is...

Consider an automobile engine which operates on the ideal Otto cycle. In this engine, air is compressed with a compression ratio of 10. At the beginning of the compression process, air is at 105 kPa and 17oC, and in the combustion process 640 kJ/kg of heat is added to air. Taking into account the variation of specific heats with temperature, determine (a) the pressure and temperature at the end of the heat-addition (combustion) process, (b) the net work output, (c)...

A single-cylinder, four stroke research engine operates on Otto cycle. The specification of the engine is...

A single-cylinder, four stroke research engine operates on Otto cycle. The specification of the engine is shown as below:- Displacement volume of the cylinder = 540 cm3 Clearance volume of the cylinder = 60 cm3 Minimum temperature = 200°C Minimum pressure = 200 kPa Net work output = 1000 kJ/kg Sketch the process on a P-V diagram and by using constant specific heat at room temperature, determine: i) the temperature and pressure at each process, ii) the thermal efficiency of...

Working from first principles, derive an expression for the efficiency of an Otto Cycle engine in...

Working from first principles, derive an expression for the efficiency of an Otto Cycle engine in terms of compression ratio. Sketch the P-V diagram for this cycle and annotate it using the same station numbers used in your derivation. State why the efficiency must be less than that of the Carnot Cycle.

Another type of external combustion steam engine in the Rankine cycle engine. You are told a...

Another type of external combustion steam engine in the Rankine cycle engine. You are told a Rankine engine will be operated in the following manner. The engine will use 0.46 kilomoles of water vapor. The water vapor is initially at 1.5 atm in a 10 m3 vessel. The water vapor is compressed isobarically to 1/10th of its original volume. The water vapor is then isochorically pressurized to 5 atm. The water is then isobarically expanded to a volume of 4.23...

Using the thermodynamic cycles, explain the difference between the heat engine (Carnot cycle) and Otto and Diesel engines. Why do Diesel engines require different types of fuel than the regular Otto Engine?

Problem 5 CH5/5ptsUsing the thermodynamic cycles, explain the difference between the heat engine (Carnot cycle) and Otto and Diesel engines. Why do Diesel engines require different types of fuel than the regular Otto Engine?

An Otto Cycle engine operation at cold-air standard has a volume of 0.1908 at the beginning...

An Otto Cycle engine operation at cold-air standard has a volume of 0.1908 at the beginning of isentropic compression. If the compression ratio is 12.5, how much heat is released from the fuel per kg of fuel burned if the fuel consumption is 0.02 kg/min? The mean effective pressure is 350kPa.

a) An open cycle gas turbine engine consists of a compressor, a combustion chamber and a...

a) An open cycle gas turbine engine consists of a compressor, a combustion chamber and a two-stage turbine with a re-heater. The gas enters the compressor at a temperature of 15 C. The pressure ratio of the compressor, which is 90% efficient, is 12. The combustion gas enters the first stage turbine at 1100 C. Both stages of the turbine are 95% efficient. The first stage has a pressure ratio of 4, whereas that of the second stage is 3....

Research how an internal combustion engine operates. Describe four steps of a combustion cycle. What materials...

Research how an internal combustion engine operates. Describe four steps of a combustion cycle. What materials go in and out of the engine during each step? How many cylinders are involved in one cycle? What energy processes take place during each stroke? In which steps is work done?

Question