How does turbulent intensity change according to 4 stroke engine’s cycle? What are some bulk motion you can do to increase the turbulent intensity?

In: Mechanical Engineering

*2. Based on initial guesses, a mesh for a CFD simulation is
set up for an external ow around an object. The
ow does not experience signicant separation on the body surface.
The results yield y+ values between 4
and 40 on the the body surface. Explain why this result is not
adequate. Explain how you would proceed to
improve the results, and how you would know when they are
acceptable.*

In: Mechanical Engineering

Describe in simple terms how an XRD instrument can be used to perform a residual stress analysis of a strained steel sample. What needs to be measured, and how are the measurements performed

In: Mechanical Engineering

A batch production operation has a machine setup time of 4.0 hr and a processing time of 1.50 min per cycle. Three parts are produced each cycle. No tool handling time is included in the cycle. Part handling time each cycle is 30 sec. It consists of the worker obtaining three starting work units from a parts tray, loading them into the machine, and then after processing, unloading the completed units and placing them into the same tray. Each tray holds 27 work units. When all of the starting work units have been replaced with completed units, the tray of completed parts is moved aside and a new tray of starting parts is moved into position at the machine. This irregular work element takes 4.0 min. Batch quantity is 2,700 units.

Determine

(a) average cycle time,

(b) time to complete the batch,

(c) average production rate.

In: Mechanical Engineering

An intermediate pressure steam turbine is to be designed with 7 repeating stages as described above. The inlet conditions are: total temperature = 550°, total pressure = 4.0 MN/m2. The exit total pressure is 0.5 MN/m2. The rotational speed of the turbine is to be 1500 rev/min and the power output required is 90 MW. It is estimated that the turbine efficiency will be 90%. Calculate the mass flow through the turbine, the axial velocity, mean blade speed and the mean diameter of the turbine.

In: Mechanical Engineering

Scenario 2: Hunter Molding Machine (Machine Guarding)

While operating a Hunter molding machine, it is necessary for a single operator to reach inside the machine to adjust the pattern or blow it off to ensure that it is free of particles or other debris that will create deformed parts. This function is conducted once every 75 minutes, 8.5 hours per day. The molding pattern is placed on the holder by the machine, which then automatically rotates the pattern 180 degrees before the molding sand is compressed on the pattern, and then this process is repeated to ensure a two-sided mold is created. When the molds are compressed and then separated, the operator must reach inside the machine to clean the pattern by blowing compressed air onto the mold. The foundry supervisor is concerned that there is a potential for the operator to be caught in the rotating pattern holder, causing an amputation. He has asked for your help to provide a control measure to prevent any possible injuries to the operators. Note: A physical barrier between the operator and the pattern holder is not possible or feasible due to production activities. Please see the photographs below as a reference.

In: Mechanical Engineering

A flat plate solar collector with no cover plate has a selective absorber surface of emissivity 0.1 and solar absorptivity 0.95. At a given time of day the absorber surface temperature ?? is 120℃ when the solar radiation is 750 W/m^2, the effective sky temperature is -10℃, and the ambient temperature ?∞ is 30℃. Assuming that the heat transfer convection coefficient for the calm day conditions, estimated h= 0.22 (?? −?∞) 1 3 W/m^2 K.

(a) Calculate the useful heat removal rate (W/m^2 K) from the collector for these conditions.

(b) What is the corresponding efficiency of the collector?

In: Mechanical Engineering

Two kilograms of air is stored in a rigid volume of 2 m3 with the temperature initially at 300°C. Heat is transferred from the air until the pressure reaches 120 kPa. Calculate the entropy change of (a) the air and (b) the universe if the surroundings are at 27°C.

In: Mechanical Engineering

Find the general solution for the following ODEs. If initial condition is given, solve the initial value problem.

3) (D^4 − 13D^2 + 36I)y = 12e^x

4) (D^3 − D^2 − D + I)y = 0, y(0) = 0, Dy(0) = 1, D^2y(0) = 0

In: Mechanical Engineering

Q.3) Suppose (y, z) plane forms the boundary between a
nonconducting linear

medium (1) and a conducting medium (2). A monochromatic plane wave
traveling

in the x direction and polarized in the y direction approaches the
interface from the

left direction.

i) Draw the diagram for this case by indicating the directions for
incident, reflected

and transmitted electric and magnetic fields along with the
propagation direction.

ii) Calculate the reflection coefficient R and transmission
coefficient T and

show that R+T=1?

In: Mechanical Engineering

A straight cylindrical pipe (içi boş boru) lying along the x axis has a length of L and inner diameter of R1 and outer diameter R2. It is made of a material with a resistivity of ρ. Assume that a potential of Vo is applied at x = L, and the potential V = 0 at x = 0. Find (a) the electric field E in the wire as a vector, show the current direction. (b) find the current density J in the wire c) Calculate the magnetic field everywhere. Show and explain every step by using Ampere’s Law. d) Calculate the amplitude of Poynting vector in the wire.

In: Mechanical Engineering

Acetylene gas (C2H2) with 20% excess air, fully in continuous regime incinerated. Air and fuel, separate to the combustion chamber, separate temperature of 250C and 1 atm under pressure and under reaction, 300,000 to the environment at 250C kJ / kmol C2H2 is experiencing heat transfer. Combustion end products, combustion chamber 1 atm leaves the pressure. a) The end of combustion here means the temperature, b) Total entropy change for 1 kmol of C2H2, c) this reaction exergy destruction (usability loss) You calculate.

In: Mechanical Engineering

The net power of a steam power plant operating according to the simple ideal Rankine cycle is 30.5 MW. Water vapor enters the turbine at 7 MPa pressure and 500 ° C, expands to 10 kPa condenser pressure in the turbine. The steam is condensed in the condenser by cooling it with water from a lake. The flow rate of the lake water is 1950 kg / h. Get the pump and turbine adiabatic efficiency of 87%. Show the cycle in the T-s diagram.

C_{water}=4.18 kJ/kg°C

a) Calculate the thermal efficiency of the cycle,

b) Flow rate of the steam circulating in the cycle,

c) Calculate the temperature rise of the coolant.

In: Mechanical Engineering

Refrigerant R-134a enters the compressor of a refrigeration machine at 140 kPa pressure and -10 ° C temperature and exits at 1 MPa pressure. The volumetric flow of the refrigerant entering the compressor is 0.23 m3 / minute. The refrigerant enters the throttling valve at 0.95 MPa pressure and 30 ° C, exiting the evaporator as saturated steam at -18 ° C. The adiabatic efficiency of the compressor is 78%. Show the cycle in the T-s diagram. In addition,

a) the power required to start the compressor,

b) Heat drawn from the cooled medium per unit time,
COP_{SM} =?

c) Calculate between the evaporator and the compressor, how much the pressure of the refrigerant drops and how much the heat gain is.

In: Mechanical Engineering

The pressure ratio of a Brayton cycle with air operated regenerator is 8. The lowest and highest temperatures of the cycle are 310 K and 1150 K. The adiabatic efficiency of the compressor and turbine is 75% and 82%, respectively, and the efficiency of the regenerator is 65%. Show the cycle in the T-s diagram. Consider the variation of specific temperatures with temperature.

a) Calculate the temperature of the air at the turbine outlet,

b) Net work of the cycle,

c) Calculate the thermal efficiency of the cycle.

In: Mechanical Engineering