A reputable engine company has been making carbureted spark-ignition engines that operate with an equivalence ratio = 1.0 and a compression ratio of 9:1 for years. In order to control emissions, the engines operate with 20% exhaust gas recirculation (EGR) and a three-way catalytic converter. Since the company’s market share is steadily dropping, they consider hiring a MEC graduate to rescue them. The ambitious young engineer proposes a port fuel-injected (PFI) design, which operates lean at 0.7 with a high compression ratio (15:1) and vigorous inlet swirl. The new engine has the spark-plug mounted at the center of the combustion chamber, while the production engine has the spark-plug at the side.

(a) Will the flame development period of the new chamber be shorter, longer, or about the same as the current design?

(b) Will the rate of the combustion of the new chamber be faster, slower, or about the same as the current design?

(c) Sketch the mass fraction burned vs. crank-angle curves for these two combustion chambers when spark-timing is set for maximum brake torque. Clearly label the sparktiming, ignition delay, and overall burn duration for each case.

(d) The engineer claims that the proposed lean-burn engine will have the same octane requirement as the production SI engine. Could this claim be true?

(e) Will the proposed lean-burn engine clearly develop greater power at full load than the current SI engine?

(f) Would there be any additional advantages or disadvantages if the proposed engine were direct-injected, stratified charge, instead of homogeneous, operating at the same overall equivalence ratio?

Discuss the interactions of mechanical engineering with other disciplines at arkansas nuclear

Question 1. Samples of n = 4 items are taken from a process at regular intervals. A normally distributed quality characteristic is measured and x-bar and s values are calculated at each sample. After 50 subgroups have been analyzed, we have

? x?_i = 1,000 and ? s_i = 72

(A) Compute the control limit for the x and s control charts

(B)Assume that all points on both charts plot within the control limits. What are the natural tolerance limits of the process?

(C) if the specifications limits are 19 + 4.0 what are your conclusions regarding the ability of the process to produce items conforming to specifications?

(D) Assuming that if an item exceeds the upper specification limit it can be reworked, and if it is below the lower specification limit it must be scrapped, what percentage scrap and rework is the process now producing?

(E) If the process were centered at u = 19.0, what would be the effect on percentage scrap and rework?

Dislocation in metals

Describe edge dislocation motion in metals from an atomic perspective. Be sure to clearly illustrate the sequence in which bonds are broken and reformed.

Also from an atomic perspective, describe how macroscopic plastic deformation occurs by the motion of dislocations in response to an applied stress. Again, use words and visuals to explain.

how does a compressor can make a recording appear to sound louder.

The convection coefficient for flow over a solid sphere may be determined by submerging the sphere, which is initially at 25 °C, into the flow, which is at 75 °C, and measuring its surface temperature at some time during the transient heating process. If the sphere has a diameter of 0.1 m, a thermal conductivity of 20 W/(m·K), and a thermal diffusivity of 4.0×10-5 m²/s, at what time will a surface temperature of 60 ºC be recorded if the convection coefficient is 300 W/(m²·K)?

a) When deciding if the lumped capacitance method can be used, what is the value of the Biot number?

Bi c= 0.2505 ( correct)

b) When using the one-term approximation for transient 1-D conduction, what is the value of the applicable Biot number? Use Table 5.1.

Bi=??

c) Using the one-term approximation, if Bi in Table 5.1 were equal to 0.5, what would be the value of C1 for this problem?

C1=??

d) Use the one-term approximation method to solve for the Fourier number.
F0=??

e) Solve for the time required for the surface of the sphere to reach 60 ºC, in sec.

t=?? sec

An accelerator in an automobile is defined as anything a person directly interacts with, resulting in a change in motion of the vehicle. Your mission is to list 12 accelerators (describe what external forces gass pedal, parking brake, window switch button, engine start/stop button, shifting lever, clutch, A/C switch, heater switch, light buttons, radio button (uses some energy maybe?), door handle (opening door would decrease aerodynamic efficiency), cigarette lighter affect in an auotmobile indirectly) that you would find in any standard automobile. You must accurately describe each accelerator and state the external forces that directly cause each acceleration using adequate diagrams and explanations. Only standard cars and trucks.

A stainless steel ball (? = 8055 kg/m³ , C_P = 480 J/Kg? K ) of diameter D = 15cm is removed from the oven at a uniform temperature of 350 Degrees C. The ball is then subjected to the flow of air at 1 atm pressure and 30 degrees C with a velocity of 6m/s. The surface temperature of the ball eventually drops to 250 degrees 250 degrees C. Determine the average convection heat transfer coefficient during this cooling process and estimate how long this process has taken. The solution should be h = 25.12 W/m2 C and time = 1425 seconds according to the professor.

Describe the main operating principle of the X-Ray Diffraction (XRD) technique for analyzing the internal structure of powders and bulk solid samples. Use figures to illustrate your answer.

refrences needed

State and explain the different stages involved in refining the grain structure of metallic powders using high-energy ball milling.

Consider a 2.0 MW wind turbine that operates with a capacity factor of 30% (i.e. it produces 5,300 MWh/y). The initial cost is $3.5 million. The project life is 30 years and the salvage value is negligible. Maintenance costs are $50,000/y. The minimum attractive rate of return is 7%. For each of the following cases, determine the present value of the project and whether the cost is justified.

a. Power can be sold to the grid at $0.055/kWh. (ans. -503200, not justified)

b. Power can be sold to the grid at $0.10/kWh. (ans. 2456000 justified)

For a ball bearing made out of plastic inner and outer race and a stainless steel ball, which of these materials is likely to wear? What would the wear pattern be like? Which will eventually fail first?

An example of a superalloy/composites that could be used to build a landing gear for a space rocket like new shepherd(blue origin)

Steam flows steadily through an adiabatic turbine. The inlet conditions of the steam are 4
MPa, 500°C and 80 m/s, and the exit conditions are 30 kPa, 92% quality and 50 m/s. The
mass flowrate of the steam is 12 kg/s. Investigate the effect of the turbine exit pressure on
the power output of the turbine. Let the exit pressure vary from 10 to 200 kPa. Plot (1) T2
vs P2 and 2) Plot the power output (W_dot_T in MW) against the exit pressure (P2 in kPa)
and discuss the results.

a. What is the extensive property of interest/study in the first law of thermodynamics?

b. What three processes can influence the property of interest in an open system analysis of the first law of thermodynamics?

c. What crosses an open system boundary that cannot cross a closed system boundary?

d. Which are additive in nature, intensive properties or extensive properties?

e. Is the rate of change of a property inside a system boundary denoted with a dot or with a time derivative?

f. Is the rate at which a property crosses a system boundary denoted with a dot or with a time derivative?

g. What is the region of space outside of the system called?