Power Machines N6 — Document

November 2020 — N6 — Power Machines

N6 2020 Nated Engineering

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🎯 100 marks ⏱️ 3h 📄 7 pages 📝 47 items found

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Q1— Section header —

1.1Use a length of 40 mm for the average blade velocity and construct velocity diagrams for the turbine Indicate the lengths of all lines in mm, as well as the magnitude of all

1.2Calculate the scale if the relative velocity of the gas at the inlet to the first stage is 526 m/s. (1\ .3 From the diagrams determine

1.3.1The magnitude of the angle at which the gas leaves the turbine (1\

1.3.2The nozzle velocity of the gas in m/s (1\

1.3.3The velocity of the gas leaving the first stage in m/s (1\

1.3.4The axial thrust developed in the turbine in N (3\

1.3.5The power developed by the turbine in MW (3\ [20] 819004620

Q2— Section header —

2.1The absolute temperature of the air at the throat (2\

2.2The value of gamma (2\

2.3The pressure at the throat in kPa

2.4At the exit:

2.4.1The pressure in kPa

2.4.2The absolute actual air temperature

2.4The velocity of the air in m/s

2.4.4The specific volume of the air

2.4.5

2.4.6

2.520

Q3— Section header —

3.1Use only steam tables to calculate

3.1.1The heat transfer in the economiser in kJ/kg steam (2\

3.1.2The heat transfer in the evaporator in kJ/kg steam (2\

3.1.3The heat transfer in the superheater in kJ/kg steam (3\

3.1.4The heat lost with the superheat ed combustion moisture leaving the plant with the flue gases in kJ/min (3\

3.1.5The heat lost with the dry flue gases in kJ/min (3\

3.2Draw up a heat balance in kJ/min and as a percentage of the heat supplied, to determine the percentage heat lost to radiation. Include all

Q4— Section header —

4.1Calculate:

4.1.1The brake power in kW (3\

4.1.2The indicated power in kW (2\

4.1.3The brake specific fuel consumption in kg/kW.h (2\

4.1.4The air fuel ratio (2\

4.1.5The energy carried away by the exhaust gases in kJ/min (2\

4.1.6The indicated thermal efficiency (2\

4.2Draw up a heat balance in kJ/min and as a percentage of the heat supplied, to determine the percentage heat lost to radiation. Assume that the heat lost to friction was absorbed by the cooling water.

Q5— Section header —

5.1The index (n\r comp ression correct to TWO decimal (4\

5.2The power required to drive the compressor in kW (4\

5.3For the low pressure cylinder:

5.3.1

5.3.2

5.3.3The volumetric efficiency (2\

5.4For the high pressure cylinder (assuming the same volumetric efficiency as the low pressure cylinder\:

5.4.1

5.4.220

Mark Allocation

Total100 marks

Sections20 + 20 + 20 + 20 + 20 = 100 marks

Paper information

TitleDocument

SubjectPower Machines

LevelN6

Document typeQuestion paper

Year2020

MonthNovember

Pages12

Downloads4

Examination context

Decade2020s

Years ago6y

SeasonSpring (SH)

Start daySunday

Exam periodNovember 2020

Days since exam2,170

About Power Machines examination preparation

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How to use this resource for revision

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For stronger examination practice, complete the paper without unnecessary interruptions and keep track of the questions that take the most time. Afterwards, review the memorandum and separate knowledge gaps from mistakes caused by interpretation, calculation, structure, or examination technique.

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A practical revision approach

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