Question

The compression ratio of an engine is 10 and the temperature and
pressure at the start of compression is 370 Celcius degree and 1
bar. The compression and expansion processes are both isentropic
and the heat rejected at exhaust at constant volume. The amount of
heat added during the cycle is 3000 kJ/kg.

Determine the mean effective pressure and thermal efficiency of the
cycle if the maximum pressure is limited to 70 bar and heat added
at both constant volume and constant pressure.

Assume that the charge has the same physical properties as that of
air.

Note: k=1.4, Cv=0.717 kJ/kgK, R=0.287 kJ/kgK

75 minutes,

Answer #1

To find Q(out) T5 is found out

From Q(out) thermal efficiency is found out

From thermal efficiency Work is found out and then P(mean) can be computed.

An inventor proposes a four-stroke cycle running on helium. The
engine has a compression ratio of 8 and maximum operating
temperature of 1,500 K. The atmospheric
conditions are temperature of 300 K and pressure of 100 kPa. The
processes can be approximated as below:
1- 2 isentropic compression
2- 3 constant volume heat addition
3- 4 isentropic expansion
4- 1 constant pressure heat removal
a. Plot P-v and T-s diagrams for this cycle.
b. Determine state conditions at the end...

An ideal Otto cycle has a compression ratio of 7. At the
beginning of the compression process, P1 = 90 kPa, T1 = 27°C, and
V1 = 0.004 m3. The maximum cycle temperature is 1147°C. For each
repetition of the cycle, calculate the heat rejection and the net
work production. Also, calculate the thermal efficiency and mean
effective pressure for this cycle. Use constant specific heats at
room temperature. The properties of air at room temperature are cp
= 1.005...

A Diesel cycle has a compression ratio of 12 and cut-off ratio
of 2. At the beginning of the isentropic-compression process, the
pressure and temperature are 100 kPa and 35°C (308 K),
respectively. During the constant-pressure process, heat is added
to the working fluid from a reservoir at a temperature of 1760°C
(2033 K). During the constant volume process, heat is rejected to
the environment, which is at 30°C (303 K) and 100kPa. For the air
involved, it may be...

In an ideal standard dual cycle, the pressure and temperature at
the beginning of compression are 1 bar and 47°C, respectively. The
heat supplied in the cycle is 1250kJ/kg, two third of this heat is
being added at constant volume and the remaining heat is added at
constant pressure. If the compression ratio is 16, determine
1)the maximum temperature in the cycle.
2)the thermal efficiency of the cycle.
3)the mean effective pressure.

10) An air-standard Otto cycle has a compression ratio of 9. At
the beginning of the compression process, the temperature is 20°C,
and the pressure is 100 kPa. The heat added is 500 kJ/kg. Determine
the cycle efficiency, work output, and the heat rejected.
11)An air-standard Otto cycle operates with a minimum
temperature of 300 K and a maximum temperature of 1700 K. The
compression ratio of the cycle is 7. At the beginning of the
compression process, the pressure...

1a. An air-standard cycle consists of the following processes:
isentropic compression from 15 ?C, 1.01 bar through a compression
ratio of 5:1; heat addition at constant volume of 2600 kJ/kg;
isentropic expansion to the initial volume; heat rejection at
constant volume. Sketch the cycle on p-v and T-s diagrams, and
calculate its ideal efficiency, mean effective pressure and peak
pressure.
Answers(0.475, 18.9 bar, 73.0 bar)
b. The cycle is problem (a) is modified so that the heat is
added
(a)...

Pressure and temperature at the beginning of compression of
compression of an air-standard (R=287 J/kgK, gamma= cp/cv=1.4).
Diesel cycle are 107kPa and 280K, respectively. At the end of the
heat addition, the pressure is 11MPa and the temperature is
2040K.
a) Determine the cut off ratio:

1) An air-standard Otto cycle has a compression ratio of 9. At
the beginning of the compression process, the temperature is 20°C,
and the pressure is 100 kPa. The heat added is 500 kJ/kg. Determine
the cycle efficiency, work output, and the heat rejected
2) An air-standard Otto cycle operates with a minimum
temperature of 300 K and a maximum temperature of 1700 K. The
compression ratio of the cycle is 7. At the beginning of the
compression process, the...

A four-cylinder, four-stroke engine is built
into an automobile. Within each cylinder of the engine, the
processes can be modeled as an air-standard Otto
cycle.
At the beginning of the compression process, the
cylinder volume is .559 L.
The temperature and pressure are 330 K and 1.5
bar, respectively. In the cycle, the maximum
temperature is 2200 K when the engine operates at
3000 RPM.
(4-stroke engine, 2 rotations per cycle, MW of air = 28.97
kg/kmol)
If the engine...

An ideal Otto engine has a compression ratio of 10 and uses air
as the working fluid. The state of air at the beginning of the
compression process is 100 kPa and 27 0C. The maximum
temperature in the cycle is 2100K. (R=0.287 for air) (using
variable specific heat)
Draw the P-v diagram of the Otto cycle
Determine the specific internal energies at the beginning and
the end of the compression,
Determine the specific internal energies before and after the...

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