Gas

Question 1

What are the 5 advantages of gas cycles

Answer 1

1 - clean and sometimes inert working fluid
2 - smaller surfaces needed for heat transfer
3 - working fluid can be lubricant
4 - turbine doesn’t have problems of wet vapour
5 - pressure is relatively low so less heavy piping

Question 2

What are the ideal gas relations

Answer 2

PV = m RT 
P = row RT
dh = cpdT
du = cv dT

Question 3

What are the ideal gas relations for isentropic

Answer 3

pv^k = constant 
TV ^(K-1) = constant 
T P (k-1/k) = constant

Question 4

What is the work done by a compressor

Answer 4

W = m (he - hi)
= h2 - h1
= cp (T2 - T1)

Question 5

What are the three types of compressor

Answer 5

1 - reciprocating (high P low fr)
2 - centrifugal (low P high fr)
3 - axial flow (similar to 2)

Question 6

Why aren’t reciprocating compressor ideal

Answer 6

• intake and exhaust valves for not open and close instantaneously
• losses occur due to values and some heat transfer may take places

Question 7

What is the equation for effectiveness of a compressor

Answer 7

n = (v1 - v4) / (v1 - v3)

the volume drawn in over the displacement volume

Question 8

What is the broke

Answer 8

diameter of piston

Question 9

What is the stroke

Answer 9

distance the piston travels in

Question 10

What happens at the TDC

Answer 10

volume occupied by air is min

Question 11

What happens at the BDC

Answer 11

volume occupied by air is max

Question 12

What is the compassion ratio for an engine

Answer 12

r = VBDC/ VTDC

Question 13

What is the work done by the cycle

Answer 13

W(cycle) = (MEP) (Vbdc- Vtdc)

MEP = mean effective pressure

Question 14

What are the stages of an otto cycle

Answer 14

0 - 1 pision at tab and moved to bcc, air sucked in
1 -2 at bcc valve closed and poison impressed until tdc
2 -3 ignition occurs, T and P increase
3 -4 combustion products expand isentropicaly to bcc
4 - 1 exhaust valve opens P decrease and V constant

Question 15

What is the heat transfer in an out of an otto cycle

Answer 15

Q in = mcv (T3 - T2)

Q out = mcv (T4 - T1)

Question 16

What is the effciceny of an otto cycle

Answer 16

n = W net/ Qin = 1 - Q out/Q in 
n = 1 - 1/(r^(k-1))

Question 17

What are the stages in the diesel cycle

Answer 17

1 - 2 isentropic compression
2 - 3 isobaric heat addition
3 - 4 combustion terminated, expansion occurs isentropicaly
4 -1 contact volume, heat rejection.

Question 18

What is the efficiency for the diesel cycle

Answer 18

n = 1 - (1/r^(k-1) x ((rc^k - 1)/k(rc-1))

Question 19

What is the efficiency of the sterling and Ericsson cycles

Answer 19

n = 1 - Ql/Qh = 1 - Tl/Th

Question 20

What is a gas turbine?

Answer 20

• used to produce power

- can operate on a closed or open system

Question 21

What is an open cycle

Answer 21

air enters compressor, passes through constant pressure combustion chamber, through turbine and into atmosphere

Question 22

What is a closed cycle

Answer 22

combustion chamber replaced with heat exchanger and energy enters from exterior source
additional heat exchanger transfers heat from the cycle so that working fluid returns to initial state

Question 23

What factors effect the efficiency of the Baryton cycle

Answer 23

1 - irreversibility in compressor and turbine
2 - pressure drop in flow passages and combustion/ heat exchanger
3 - work required by compressor

Question 24

what is the efficiency of a Baryton cycle

Answer 24

n = 1 - rp^(1-k/k) where rp - P2/P1

Question 25

What is the efficiency of the regenerative gas cycle

Answer 25

n = (W turb - W comp)/q in | = 1 - T1/T4 x rp^(k-1/k)

Question 26

What is a CHP

Answer 26

system where both electrical power and heat are itlized

Question 27

What are turbojet engines

Answer 27

reaction engin with turbine only extracting sufficient energy to drive compressor, high speed air craft

Question 28

What are turbofan engines

Answer 28

reaction engine, part of air entering gets compressed fully | lower noise and better fuel consumption so used for civilian air craft

Question 29

What are turboprop engines

Answer 29

use exhaust stream to power additional power turbine which drive a propeller

Question 30

what are turbo shaft engines

Answer 30

like turbo prop, power turbine couples to an output shaft absorbing as much energy in gas stream, helicopters

Question 31

What does V thrust equal?

Answer 31

V thrust = V6 - V1

Question 32

What is the mole fraction

Answer 32

yi = Ni /N

Question 33

What is the mass fraction

Answer 33

mfi = mi / m

Question 34

What is the mean molecular weight of a mixture

Answer 34

m = M/ N

Question 35

What is the mixtures gas constant

Answer 35

R = R bar / m

Question 36

What is the amigo model

Answer 36

- treats each component as though is exists separately at the same pressure and temperature of mixture - total volume is the sum of the comments

Question 37

What is the dalton model

Answer 37

-each comment occupies the same volume and has the same temperature as mixture. -total pressure is the sum of component pressure

Question 38

what is the relative humidity ratio for absolute humidity?

Answer 38

w = mv/ma | where mv is mass of water vapour, ma is mass of dry air

Question 39

what is the relative humidity ratio

Answer 39

phi = mv/mg | where mv is mass of water vapour, mg is max mass of vapour in air at same temp

Question 40

What is the drew point temperature

Answer 40

temperature at which vapour condenses when its cooled at constant pressure

Question 41

Draw a ts and pv graph for stringing and erricson cycle

Answer 41

.

Question 42

Draw a ts and pv graph for barytone cycle regenerative cycle

Answer 42

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