ME 495 Final Exam

3 Components of Brayton Turbine Engine

Compressor, Combustion, Turbine

Isentropic

Adiabatic and reversible, entropy unchanged

Brayton Cycle Fuel

Kerosene and 500 AeroShell Turbine Oil mix

4 Turbine Assumptions

working fluid = ideal gas, combustion = constant P heat addition

exhaust = constant P heat rejection, constant specific heat at lowest P

Bomb Calorimeter Heating Value

Describes fuel energy production

Units of HV

per unit mass of the fuel

BC Complication: heat leaks everywhere

Corrected by: adjusted equation

BC Complication: Fuse burns

Corrected by: weigh fuse material

BC Complication: temp difference with surroundings

Corrected by: calorimeter insulation

BC Complication: burning hydrocarbon creates water vapor

Corrected by: higher vs. lower HV

BC Solid Fuel

Benzoic Acid Tablet

BC Liquid Fuel

Diesel

m water vs. m*

mass of only water vs. mass of all system components that absorb heat

4 components of vapor power plant

pump, boiler, turbine, condenser

Difference between RankineCycler vs. real vapor power plant

Pump does not compress water, funneled directly into boiler

Tubular HE setup

2 coaxial tubes, inner carries hot water, outer carries cold water

Direction of flow in tubular HE

countercurrent (opposite)

Heat transfer coefficient affected by

material properties, temp gradient, heat exchanger geometry, fluid flow rates

Mass flow rate =

Volume flow rate * density

Heat rate =

mass flow rate * specific heat capacity * temp gradient

Tubular and Plate HE - cold water flow rate decreases

less heat removed, less efficient

Plate HE setup

2 parallel plates, both streams pass three times in series between plates

Purpose of Vibration Analysis

Predictive maintenance, identify before failure

3 issues vibration analysis can identify

misaligned shafts, worn bearings, unbalanced sheaves

Tachometer function

measure motor speed in RPM

Single Tension Tester function

measures tension in timing belt

Direction of highest motor vibration

horizontal

Direction of highest bearing vibration

vertical

Direction of hydrostatic force variation

vertical

When moments about pivot point are equal

system is in equilibirum

3 things that determine natural frequency

mass, spring constant, damping ratio

Definition of natural frequency

material oscillates indefinitely at this frequency once moved

Purpose of damping

reduce vibration

Purpose of expansion valve

controls flow of refrigerant entering the evaporator

Superheat

heat added to a substance above saturation temp

Manually adjusting expansion valve controls

amount of energy entering evaporator

refrigeration unit demonstrates

vapor-compression refrigeration cycle

5 Components of vapor refrigeration unit

water reservoir, evaporator, rotary compressor, condenser, expansion valve

As expansion valve opens more, temp

decreases

When compressor speed increases

efficiency decreases

Larger vessel acts _______ , smaller vessels acts ________

under pressure, in a vacuum

Pressure release valve function

prevents over-pressurization

Ball valve function

transfers air between vessels and environment

Isolating valve function

isolates vessels from air pump

Needle valve function

small airflow adjustment between vessels

is ROV exo-, endo-, or iso- thermal

isothermal, initial temp = final temp

How to find volume ratio of two vessels

rearrange ideal gas law

3 stages of generalized measuring system

sensor, signal conditioning, readout

Analog signal

analogous to physical property

Digital signal

changes in steps

uncertainty definition

likely upper bound on error

systematic vs. random error

occurs on every meaurement vs. variable for each

population defintion

finite or infinite group from which samples are drawn

sample definition

defined number of members

3 common distibutions

Gaussian, T distribution, X^2 distribution

Probability density function

describes random precision error

frequency spectrum plots

frequency vs. amplitude

Amplitude response

treats all amplitudes uniformly

Frequency response

measures all frequency components proportionally

Phase response

maintains phase relationships in a complex wave

Slew rate

max rate of change manageable

First order systems assume

mass = 0

Second order systems have

step input

3 Rankine Cycle Calculation Steps

Find enthalpies of states 2-4,

Find mixture quality (x),

Find turbine efficiency

4 Laser Vibrometry Calculation Steps

Find critical and actual damping,

Find damping ratio,

Find natural and angular frequency,

Find phase angle

Units of HV

per unit mass of fuel