What is the effect of compression ratio on efficiency of Otto cycle?
As the compression ratio increases, the fuel mixture is sufficiently compressed thereby increasing the thermal efficiency, so that less fuel is required to produce the same amount of energy. Fuel consumption is reduced at higher compression ratios between 8 and 9.
What is the efficiency of Otto engine?
According to Mercedes, their power unit is now achieving more than 45% and close to 50% thermal efficiency, i.e. 45 – 50% of the potential energy in the fuel is delivered to wheels. The diesel engine has the highest thermal efficiency of any practical combustion engine.
What is the compression ratio of Otto cycle?
In the ideal Otto cycle the fuel-air mixture is introduced during the induction stroke and compressed to a much lower compression ratio (around 8:1) and is then ignited by a spark. The combustion results in a sudden jump in pressure while the volume remains essentially constant.
Why Otto cycle has higher efficiency then diesel cycle for the same compression ratio?
3. 6 Diesel Cycle. Although for a given compression ratio the Otto cycle has higher efficiency, because the Diesel engine can be operated to higher compression ratio, the engine can actually have higher efficiency than an Otto cycle when both are operated at compression ratios that might be achieved in practice.
Which of the following cycles has maximum efficiency?
Carnot cycle
Which thermodynamic cycle has maximum efficiency?
What is the value of efficiency of Carnot cycle?
It is well known that the Carnot cycle efficiency ( η thermal = 1 − T L T H ) is maximized with the highest possible heat source temperature TH and the lowest possible heat sink temperature TL.
Which engine has maximum efficiency?
Carnot engine
What are the four processes of a Carnot cycle?
The four stages in the Carnot cycle. (A) Stage 1: Isothermal expansion under heat input Q1, (B) Stage 2: Adiabatic expansion accompanied by a fall in temperature T1 to T2, (C) Stage 3: Isothermal compression, Q2 exhausted, (D) Stage 4: Adiabatic compression accompanied by an increase in temperature T2 to T1.
What is the principle of Carnot cycle?
Carnot’s theorem states that all heat engines between two heat reservoirs are less efficient than a Carnot heat engine operating between the same reservoirs. Every Carnot heat engine between a pair of heat reservoirs is equally efficient, regardless of the working substance employed or the operation details.
Why is Carnot cycle reversible?
Carnot cycle is one of the best-known reversible cycles. Hence, it is a reversible heat transfer process. Gas in the cylinder expands slowly, does work to its surroundings, and remains at a constant temperature TH. The total amount of heat transferred to the gas during this process is QH.
What is the significance of area under temperature entropy TS diagram?
Temperature Entropy Diagram The area under the curve 1-2 represents the energy absorbed as heat by the system during the isothermal process. The area under the curve 3-4 is the energy rejected as heat by the system. The shaded area represents the net work done by the system.
What is PV indicator diagram?
A pressure–volume diagram (or PV diagram, or volume–pressure loop) is used to describe corresponding changes in volume and pressure in a system. They are commonly used in thermodynamics, cardiovascular physiology, and respiratory physiology.
How do you calculate heat from a PV diagram?
One way is to find out the internal change energy of the system and infer the heat transfer to the system from that and the work done: δQto=dU−δWon. to find the heat delivered.
What do you mean by indicator diagram?
An indicator diagram is a chart used to measure the thermal, or cylinder, performance of reciprocating steam and internal combustion engines and compressors. The indicator diagram is used to calculate the work done and the power produced in an engine cylinder or used in a compressor cylinder.
How do you calculate power from an indicator diagram?
How to calculate power of Main Engine (2 stroke engine)?
- Power card or PV diagram can be used to measure indicated power in diesel engines.
- Calculations.
- Work done in one cycle = Mean Indicated Pressure x Area of the Piston x Length of stroke = [Pm] x [A] x [L]
- Indicated Power of Unit = Pm L A N.
What is the use of indicator diagram or PV diagram?
A curve showing variation of volume of a substance taken along the X-axis and the variation of pressure taken along Y-axis is called an indicator diagram or P-V diagram. The shape of the indicator diagram shall depend on the nature of the thermodynamical process the system undergoes.
How do you calculate effective pressure?
Calculated from in-cylinder pressure over intake and exhaust portions of engine cycle (360° in a four-stroke, 0° in a two-stroke). Direct measurement requires cylinder pressure sensing equipment. PMEP = IMEPg – IMEPn.
What is the difference between mean effective pressure and mean indicated pressure?
MEP, Mean Effective Pressure is calculated backwards from the measured Brake power using the PLAN formuala. Where P is the pressure, L is length of stroke, A is area and N is Number of power strokes. The Indicated Power and Pressure will always be greater than the MEP and Brake Power because of friction in the engine.
Can mean effective pressure be less than atmospheric?
Can the mean effective pressure of an automobile engine in operation be less than the atmospheric pressure? Yes.