Engineering - Engine Cycles

Question 1

First step (both)

Answer 1

Inlet valve opens, exhaust valve closes

Question 2

Induction stroke (petrol)

Answer 2

Air/fuel mixture in
Piston down
V increases

Question 3

After induction stroke (both)

Answer 3

Inlet valve closes

Question 4

Compression stroke (both)

Answer 4

Piston up
Adiabatic compression
T increases

Question 5

Ignition step (petrol)

Answer 5

Spark ignites mixture
Q1 in
P increases
T increases

Question 6

Power stroke (petrol)

Answer 6

Increased p so piston down
Adiabatic expansion
P decreases
T decreases
V increases

Question 7

After power stroke (both)

Answer 7

Exhaust valve opens
Most gas leaves
Q2 out
P decreases
T decreases

Question 8

Exhaust stroke (both)

Answer 8

Piston up
Rest of gas expelled
V decreases to initial

Question 9

Power stroke 1 (diesel)

Answer 9

Fuel sprayed in
Fuel ignites
Q1 in
Piston down from fuel burning
Constant p
V increases

Question 10

Power stroke 2 (diesel)

Answer 10

Fuel supply cut off
Adiabatic expansion
Piston down
T decreases
P decreases
V increases