H3051
THE UNIVERSITY OF SUSSEX
BEng (final year) and MEng (year 3) EXAMINATION 2021
January 2021 (A1)
ENGINE TECHNOLOGY
Candidates must attempt THREE out of FOUR questions
Exam Duration: 3 hours
If all four questions are attempted, all will be marked, but the lowest mark
will not be counted in the total for the paper.
Write your answers on A4 paper, scan and save as a single PDF file and
upload to Canvas
PDF file name: candidate number_module title
Examination handout: Formula Sheet (available to download from Canvas)
Read Academic Integrity Statement
You are reminded that you should not access online materials, notes etc. during this
examination or discuss this assessment with others before the end of its 24 hour
window.
By submitting this assessment you confirm that you have read the above Statement
and are responsible for understanding and complying with Academic Misconduct
regulations as they relate to this assessment.
H3051 ENGINE TECHNOLOGY
2
Question 1
a) Using Figure Q1-1, suggest a specification for a four-stroke naturally
aspired engine with the maximum power of 240 kW and the maximum
torque of 1200 Nm. The specification will include the suggested stroke of
cylinders, area and bore of pistons and the resulting swept area. Assume
that the maximum pressure on piston must be 2.5 MW/m2 and must
be less than or equal to 9 .
Hint: As the best practice, the bore of the pistons should be slightly less
than their stroke.
Figure Q1-1: Maximum torque and power curves of the engine at different rotational
speeds
[10 marks]
b) For the results of (a), calculate the Mach number of airflow through the
intake valve of the engine and estimate the volumetric efficiency using
Figure Q1-2. Assume = 0.35 and = 30℃. The specific gas
constant and the heat capacity ratio of air are respectively 287 / /
and 1.40 ( ).
Figure Q1-2 Volumetric efficiency of the engine in terms of Mach number of airflow
[6 marks]
/Question continued on next page
0
50
100
150
200
250
0
200
400
600
800
1000
1200
1400
0 1000 2000 3000 4000
Speed (rpm)
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
0.9
0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7
Valve Flow Mach Number (-)
Power (kW)
Torque (Nm) Volumetric Efficiency (-)
H3051 ENGINE TECHNOLOGY
3
c) As in Figure Q1-3, the intake air path consisting of a carburettor and a
compressor can be with either of the following configurations:
a. the carburettor placed before the compressor;
b. the carburettor placed after the compressor.
Compare the cooling effect of fuel evaporation on charge temperature in a
turbocharged spark-ignition engine for these two cases. Explain which
configuration is preferable.
Assume that the air/fuel ratio is 14.7: 1 and the evaporation of the fuel at
this ratio causes a 30 ℃ drop in mixture temperature. The pressure ratio is
1.65 and the corresponding isentropic efficiency of the compressor is 73%.
The ambient air is 25℃, the specific heat capacity and ratio of air are
respectively , = 1.01
