Internal Combustion EnginesME 4143

Syed Hassan ShahAssistant Professor

Department of Mechanical Engineering

Lec:1 17th Feb,2015

EDUCATION PROFILE

• BACHELORS: MECHANICAL ENGINEERING, NED UNIVERSITY 2003

• MASTERS: MATERIALS SCIENCE AND ENGINEERING, UNIVERSITY OF DELAWARE,USA 2008

RESEARCH PROFILE

UNIVERSITY OF DELAWARE

• DEPARTMENT: MATERILAS SCIENCE AND ENGINEERING• ADVISER: Valeria Gabriela Stoleru

Assistant Professor Department of Materials Science and Engineering University of Delaware(2004-2008)

RESERCH AREAS:• UDRF: “Directed Assembly of III-V Quantum-Dot Nanostructures for Photonic and

Optoelectronic Devices”• UDRF: “Design and Fabrication of Electro-Optic Devices based on Quantum Dots• DOE/EPSCoR National Laboratory Partnership: “Key Physical Mechanisms in

Nanostructured Solar Cells” in collaboration with Andrew G. Noman (NREL, Golden, CO)

URL:1. http://www.mseg.udel.edu/faculty_research/vita/StoleruCV_0507.pdf2. http://www.mseg.udel.edu/images/projects/Stoleru/Titanium_oxidation.pdf3. http://www.yatedo.com/p/Gabriela+Stoleru/normal/e7e67fad73d442ee737dda8

62d313a86

UNIVERTSITY OF TEXAS ATARLINGTON

• DEPARTMENT: MATERILAS SCIENCE AND ENGINEERING• ADVISER: SAMIR IQBAL (EE DEPT.)• RESERCH FUNDING: CONTACT - Nanotechnology Research for Air

Force Applications • RESEARCH AREAS1. Nanoscale heat transfer, fluidics, manufacturing, optics, nano-

and mciro-scale electro-mechanical devices (NEMS and MEMS)2. NANOBIO DEVICES: DNA ANALYZER,CANCER DETECTION DEVICES

URL:http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=4617229&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D4617229

King Abdullah University of Science and Technology

• DEPARTMENT: MATERILAS SCIENCE AND ENGINEERING• ADVISER: Osman M. Bakr • RESERCH FUNDING: Office of Competitive Research Funds

(OCRF) • RESEARCH AREAS1. Synthesis of Si Nano particles2. Separation and characterization of Nanoparticles using Ultra

Centrifugation

COURSE OVERVIEW I

Instructor: Syed Hassan Shah (SEC-2)Time: Tues/Thurs as per time tableClass Activities:• Present new material• Announce homework, exams, etc.• Casual quiz

• No small talk or irrelevant discussion at all!!!

• TEXT BOOKINTERNAL COMBUSTION ENGINE FUNDAMENTALS by J.B.Heywood (Intern. Edit)Reference Books:1. Internal Combustion Engines: Applied

Thermosciences by Colin R. Ferguson2. Engineering Fundamentals of the Internal

Combustion Engine (2nd Ed) by W.P Pulkrabek

COURSE OVERVIEW II

COURSE OVERVIEW II

• We will start with review of ME-2123 Thermodynamics II

• Important topics reviewed will beThermodynamic processesThermodynamic CyclesOtto Cycle/ Diesel Cycle

THERMODYNAMIC PROCESSES

A thermodynamic process may be defined as the energetic evolution of a thermodynamic system proceeding from an initial state to a final state. Paths through the space of thermodynamic variables are often specified by holding certain thermodynamic variables constant.

Thermodynamic Processes - IsothermalTo keep the temperature

constant both the pressure and volume change to compensate. (Volume goes up, pressure goes down)

“BOYLES’ LAW”

Thermodynamic Processes - IsobaricHeat is added to the gas

which increases the Internal Energy (U) Work is done by the gas as it changes in volume.

The path of an isobaric

process is a horizontal line called an isobar.

∆U = Q - W can be used since the WORK is POSITIVE in this case

Thermodynamic Processes - Isovolumetric

Thermodynamic Processes - AdiabaticADIABATIC- (GREEK-

adiabatos- "impassable")

In other words, NO HEAT can leave or enter the system.

Polytropic Process• When a gas undergoes a reversible process in which

there is heat transfer, the process frequently takes place in such a manner that a plot of the Log P (pressure) vs. Log V (volume) is a straight line. Or stated in equation form

• PVn = constant.• This type of process is called a polytropic process. An

example of a polytropic process is the expansion of the combustion gasses in the cylinder of a water-cooled reciprocating engine

The Polytropic process: PVn=Const.

V

p State 1

State 2

Assumptions• Changes in KE and PE are zero• Quasistatic process• Ideal gas

2

1

2

1

)(

,21

V

V

V

Vby

dVVP

PdVWExpression for work:

Process equation:nn PVCVP 111

nVPVP

dVVCW

V

V nby

11122

1,21

2

1

Note that n cannot equal one, which is the general case.

Quasi-Static processes are processes in which every state of the process is an equilibrium process. The process is carried out so slow such that when we look at the state it looks at equilibrium.

(1)A constant-volume (isochoric) thermodynamic process in which the system is confined by mechanically rigid boundaries. No direct mechanical work can be done on the surroundings by a system with rigid boundaries; therefore the heat transferred into or out of the system equals the change of internal energy stored in the system.

An Isentropic Process is a process in which entropy of the system remains constant. (no irreversibilities or heat transfers)

SUMMARY

THERMODYNAMIC CYCLESHEAT SOURCE

HEAT SINKPump

Engine W

Qin

Qout

Working Substance

Thermodynamic Cycles• Definition: a recurring series of

thermodynamic processes through which an effect is produced by transformation or redistribution of energy

• One classification:– Open: working fluid taken in, used, & discarded– Closed: working medium never leaves cycle,

except through leakage; medium undergoes state changes & returns to original state

Five Basic Elements of all Cycles• Working substance: transports energy within

system• Heat source: supplies heat to the working medium• Engine: device that converts the thermal energy of

the medium into work– Heated: heat added in engine itself– Unheated: heat received in some device separate from

engine

Five Basic Elements of all Cycles• Heat sink/receiver: absorbs heat from the working

medium• Pump: moves the working medium from the low-

pressure side to the high-pressure side of the cycle• Examples:

– Closed, unheated engine: steam cycle– Open, heated engine: gasoline engine

Second Law of Thermodynamics

• Reversibility:– the characteristic of a process which would allow

a process to occur in the precise reverse order, so that the system would be returned from its final condition to its initial condition, AND

– all energy that was transformed or redistributed during the process would be returned from its final to original form

EnginesHeat flows from a HOT reservoir to a COLD reservoir

CHoutput

CH

QQWQWQ

QH = remove from, absorbs = hotQC= exhausts to, expels = cold

Engine EfficiencyIn order to determine the

thermal efficiency of an engine you have to look at how much ENERGY you get OUT based on how much you energy you take IN. In other words:

H

C

H

CH

hotthermal Q

QQQQ

QWe

1

Rates of Energy UsageSometimes it is useful to express the

energy usage of an engine as a RATE.For example:

The RATE at which heat is absorbed!

The RATE at which heat is expelled.

The RATE at which WORK is DONE

POWERtW

tQ

tQ

C

H

Efficiency in terms of rates

tQ

tQP

eP

tQ

tQP

tQt

W

QWe

CH

H

HHHthermal

Is there an IDEAL engine model?

Our goal is to figure out just how efficient such a heat engine can be: what’s the most work we can possibly get for a given amount of fuel?

The efficiency question was first posed—and solved—by Sadi Carnot in 1820, not long after steam engines had become efficient enough to begin replacing water wheels, at that time the main power sources for industry.  Not surprisingly, perhaps, Carnot visualized the heat engine as a kind of water wheel in which heat (the “fluid”) dropped from a high temperature to a low temperature, losing “potential energy” which the engine turned into work done, just like a water wheel.   

Carnot EfficiencyCarnot temperatures must be

expressed in KELVIN!!!!!!

The Carnot model has 4 parts•An Isothermal Expansion•An Adiabatic Expansion•An Isothermal Compression•An Adiabatic Compression

The PV diagram in a way shows us that the ratio of the heats are symbolic to the ratio of the 2 temperatures

ExampleA particular engine has a power output of 5000 W and an efficiency of

25%. If the engine expels 8000 J of heat in each cycle, find (a) the heat absorbed in each cycle and (b) the time for each cycle

ttW

tWP

WQWQQW

QJQQ

e

QQeWP

HCH

Hc

H

H

C

5000

8000

8000

8000125.025.0

15000

10,667 J

2667 J

0.53 s

ExampleThe efficiency of a Carnot engine is 30%. The engine absorbs 800 J of heat

per cycle from a hot temperature reservoir at 500 K. Determine (a) the heat expelled per cycle and (b) the temperature of the cold reservoir

C

C

H

CC

C

CCH

H

T

TTTe

QQWQQW

WJ

WQWe

500130.01

800800

30.0 240 J

560 J

350 K

NEXT TIME

• Engine Terminology• Review of Air Standard Cycles