UNIVERSITY OF WEST BOHEMIAFACULTY OF MECHANICAL ENGINEERING

DEPARTMENT OF POWER SYSTEM ENGINEERING

Ratkovská Katarína

JET ENGINES

HISTORY• 17.12.1903 Orvill Wright and Wilburom Wright

- first controlled flight

• 1935 Frank Whitley- patented principle of jet engines

• 27.8.1939 Hans von Ohain- HeS – 3B jet engine

W - 1

He - 178

TYPICAL ENGINE CUTS

0 – 1 engine intake1 – 2 compressor2 – 3 main combustion chamber3 – 4 gas turbine4 – 5 exhaust system

VK 1 engine with radial

compressor

RD 33

MiG-29

BASIC PARAMETERS

• Engine thrust [N]- It's more important parameter, which is

characterized a jet engines with direct reaction

[N ]Where:- mass flow rate []- – output gas velocity []- – air speed []

• Engine thrust [N]

mass flow rate - gas [] mass flow rate - air [] – output gas velocity [] – air speed []

• Engine performance P[W] turbo-prop engines

- – propeller thrust [N]- – air speed- – propeller efficiency [1]

Turboprop engine TP 100

TS - 21

- Turboshaft engine with free gas turbine.- It is starter of R-27F2M-300 engines.

Mig 23 - FLOGGER

• Air mass flow rate[] - Quantity of air that flows through the engine

in second.

=

• m – air mass [kg]• t – time [s]

• Specific engine thrust Fm []

• Hour fuel consumption [kg.]

- Fuel flow rate.

• Total compressor pressure ratio - Define ratio between total pressure on compressor

output to total pressure on compressor input.

– total air pressure on compressor input [Pa] – total air pressure on compressor output [Pa]

COMPRESSOR TYPESCentrifugal flow compressors

AXIAL FLOW COMPRESSORS

• Total absolute temperature before turbine stage [K]

- is the temperature value on combustion chamber output before turbine stage.

T3T = t3T+273,15 [K]

• Total absolute temperature behind turbine stage [K]

T4T = t4T+273,15 [K]

THERMAL CYCLE

• Jet engines are reactive engines witch works with atmospheric air. Purpose of air in this case is:

- Basic component of working media in thermodynamic cycle- Oxygen included in air is used during chemical reaction of burning- Accelerated air (in case of engines with direct reaction) create trust

SfJE - Ideal thermal cycle

SfJE with afterburner – ideal thermal cycle

WORK OF IDEAL THERMAL CYCLE

• In p-V diagram

• In T-s diagram

1,,. . kgJWWW adkomadexid

121. . kgJqqWid

WORK OF IDEAL THERMAL CYCLE

Ideal expansion work of gas:

1013

3

5353,

.11...11..

1..

kgJe

TcTc

TTTcTTcW

pp

ppadex

EFFICIENCY OF IDEAL CYCLE - SfTJE

• Quality of transformation of input heat “” to work “” is described by thermodynamic efficiency “”

111111..

1.1..

10

0

1

ee

eeTce

eTc

qW

p

pi

t

DEPENDENCE OF “” BY “”

WORK OF IDEAL THERMAL CYCLE - SfTJE

0

3

.

1

. TTe

opt

opt

0dedWi

1.2

0

31.2.

TT

opt

CONCLUSION

• Work of ideal cycle in thermodynamics is characterized by efficiency .

• Thermal efficiency of cycle depend by pressure ratio π and temperature ration /

DISCUSSION

QUESTIONS