(SEM -FIFTH) THEORY EXAMINATION 2017-18 I C ENGINES & COMPRESSORS

I.C. Engines & Compressors (NME-505)

Section-Wise Important Questions & Study Notes

SECTION–A

(Attempt all | 2 × 10 = 20)
Write short definitions, formulas, or neat sketches (2–3 lines each).

Degree of Reaction
Ratio of static enthalpy rise in the rotor to the total enthalpy rise of the stage (used in turbomachinery).

Motor Octane Number (MON) & Research Octane Number (RON)
RON measures knock under mild conditions; MON measures knock under severe conditions. Higher values indicate better anti-knock quality.

Swirl & Squish
Swirl is rotational air motion about cylinder axis; squish is radial inward flow near TDC—both improve mixing and combustion.

Actual P–V Diagram (Four-Stroke Engine)
Draw showing intake/exhaust losses, compression/expansion, and pumping loop.

Equivalence Ratio (φ)
φ = (Actual A/F) / (Stoichiometric A/F). φ>1 rich, φ<1 lean.

BMEP (Numerical)
Know relation between torque, swept volume, and cycles to compute BMEP.

Separation of Crude Oil
By fractional distillation.

Additives in Lubricants
Improve viscosity index, reduce wear, oxidation, corrosion, and foaming.

Catalytic Converter
Device that reduces CO, HC, and NOx using catalysts (Pt, Pd, Rh).

Mean Effective Pressure (MEP)
Imaginary constant pressure producing the same work per cycle as the actual cycle.

SECTION–B

(Attempt any THREE | 10 × 3 = 30)
Mix of derivations and theory.

1. Otto Cycle – Maximum Work Condition

Show that for given T₁ and T₃, T₂ = T₄ = (T₁T₃)¹ᐟ² for maximum work/kg of air.

2. Combustion Chambers in C.I. Engines

Open chamber (direct injection) and divided chambers (pre-combustion, swirl, air cell)—features and applications.

3. Ignition Lag in S.I. Engine

Define ignition lag; discuss effects of mixture strength, temperature, pressure, fuel properties, and engine speed.

4. Otto vs Diesel Cycle Comparison

Compare for same max pressure & heat input; also for same compression ratio & heat rejection (efficiency, work).

5. Mean Effective Pressure Relation

Derive MEP = (ηth × ΔP) / [(r−1)(γ−1)] (as per given relation).

SECTION–C

(Attempt any ONE | 10 × 1 = 10)

3(a) Surging & Stalling in Axial-Flow Compressors

Define both; causes, effects, and prevention (guide vanes, control).

OR

3(b) Thermo-Syphon Cooling System

Explain working with neat sketch; advantages and limitations.