Air standard Cycle.

Objective: To write a python Code Program to Plot a P-V diagram for an Otto –cycle for given geometric volumetric parameters at a particular compression ratio and calculate the thermal efficiency of the system as well.

Engine Design and Operating Parameters (Important Engine Characteristics):

Design Requirements:

1) Good engine performance over entire operating range.

2) Cost of fuel to be kept within limits.

3) Low engine noise and pollution in this range.

4) low initial cost installation costs.

5) Reliability and durability, maintenance requirements and how they affect engine cost, etc.

Engine performance is defined by:

1) Maximum power (or max. torque) available at each speed within a useful range.

2) Range of speed power over which engine operation satisfactory.

Some definition:

1) Maximum rated power: Highest power engine is allowed to develop for short periods, also referred to as “Intermittent power rating”.

2) Normal rated power: Highest power engine allowed developing in “continuous rating”.

3) Rated speed: Speed at which rated power is developed.

CYLINDER GEOMETRY

Result: 0.0008567979964335801

0.0008567979964335802 [Finished in 4.1s]

Note: Using the Python Code for engine geometry we have to solve Otto cycle problem.

OTTO CYCLE

This cycle is so named as it was conceived by ‘Otto’. On this cycle, petrol, gas and many types of oil engines work. It is the standard of comparison for internal combustion engines.

Figs. (a) and (b) shows the theoretical p-V diagram and T-s diagrams of this cycle respectively.

1. point 1 represents that the cylinder is full of air with volume V1, pressure p1, and absolute temperature T1.

2. Line 1–2 represents the adiabatic compression of air due to which p1, V1, and T1 change to p2, V2, and T2, respectively.

3. Line 2–3 shows the supply of heat to the air at a constant volume so that p2 and T2 change to p3 and T3 (V3 being the same as V2).

4. Line 3–4 represents the adiabatic expansion of the air. During expansion p3, V3, and T3 change to a final value of p4, V4 or V1 and T4, respectively.

5. Line 4–1 shows the rejection of heat by air at constant volume till the original state (point 1) reaches.

Consider 1 kg of air (working substance):

Heat supplied at constant volume = CV (T3 — T2).

Heat rejected at constant volume = CV (T4 — T1).

But, work done = Heat supplied — Heat rejected

= CV (T3 — T2) — CV (T4 — T1)

Python Code for the Otto cycle simulator:

Output: Now the output of the above is a follows:

Plots:

1) Using state variables:

P-v diagram for Otto cycle using volume tracing at cr = 08

2) Using volume traces:

P-v diagram for Otto cycle using volume tracing at cr = 08

Consolation:

Using this program as a template, for various combinations of geometric parameters- stroke and bore, connecting rod length, etc., and volumetric parameters — clearance volume, swept volume, etc… And an output showing ‘p –v’, a‘t-s’ diagramed thermal efficiency can be acquired which could save time and effort of the designers.