Читать книгу Internal Combustion Engines - Allan T. Kirkpatrick - Страница 44

1 1.1 Compute the mean piston speed, bmep (bar), torque (Nm), and the power per piston area for the engines listed in Table 1.2.Table 1.2 Engine Data for Homework ProblemsBoreStrokeSpeedPowerEngine(mm)(mm)Cylinders(rpm)(kW)Marine13612712 26001118Truck108 95 8 6400 447Airplane 86 57 810500 522

2 1.2 A six‐cylinder, two‐stroke airplane engine with a compression ratio = 9 produces a torque of 1100 Nm at a speed of 2100 rpm. It has a bore of 123 mm and a stroke of 127 mm. (a) What is the displacement volume and the clearance volume of a cylinder? (b) What is the engine bmep, brake power, and mean piston speed?

3 1.3 A four‐cylinder, 2.5 L four‐stroke spark ignited engine is mounted on a dyno and operated at a speed of = 3000 rpm. The engine has a compression ratio of 10:1 and mass air–fuel ratio of 15:1. The inlet air manifold conditions are 80 kPa and 313 K. The engine produces a torque of 160 Nm and has a volumetric efficiency of 0.82. (a) What is the brake power (kW)? (b) What is the brake specific fuel consumption bsfc (g/kWh)? (c) What is the brake work (kJ) per cylinder per revolution?

4 1.4 The volumetric efficiency of the fuel injected marine engine in Table 1.2 is 0.80 and the inlet manifold density is 50% greater than the standard atmospheric density of = 1.18 kg/. If the engine speed is 2600 rpm, what is the inlet air mass flowrate (kg/s)?

5 1.5 A 380 cc single‐cylinder, two‐stroke motorcycle engine is operating at 5500 rpm. The engine has a bore of 82 mm and a stroke of 72 mm. Performance testing gives a bmep = 6.81 bar, bsfc = 0.49 kg/kWh, and delivery ratio of 0.748. What is the fuel–air ratio, ? Assume standard atmospheric conditions of 298 K and 101.3 kPa.

6 1.6 A 3.8 L four‐stroke, four‐cylinder fuel‐injected automobile engine, with an equal bore and stroke and a compression ratio of 10:1, has a power output of 88 kW at 4000 rpm and volumetric efficiency of 0.85. The bsfc is 0.35 kg/kWh. (a) What is the bore and ? (b) If the fuel has a heat of combustion of 42,000 kJ/kg, what are the bmep, thermal efficiency, and air–fuel ratio, ? Assume standard atmospheric conditions of 298 K and 101.3 kPa.

7 1.7 A 4.0 L six‐cylinder automobile engine is operating at 3000 rpm. The engine has a compression ratio of 10:1, and volumetric efficiency of 0.85. If the bore and stroke are equal, (a) what is the stroke , (b) the mean piston speed , (c) the cylinder clearance volume , and (d) the inlet air mass flowrate ? Assume standard inlet air conditions of 298 K and 101.3 kPa.

8 1.8 A 10.0 L, eight‐cylinder square four‐stroke truck engine has a brake mean effective pressure of 11 bar, and operates at 2500 rpm with a volumetric efficiency of 0.85. Assume inlet air conditions of 298 K and 1 bar. (a) What is the total mass air flowrate into the engine, (b) the brake power produced by the engine, (c) the bore, and (d) the mean piston speed?

9 1.9 Chose an automotive, marine, or aviation engine of interest, and compute the engine's mean piston speed, bmep, and power/volume. Compare your calculated values with those presented in Table 1.1.

10 1.10 Compare the approximate, Equation (1.36), and exact, Equation (1.33), dimensionless cylinder volume versus crank angle profiles for mm, and mm. What is the maximum error, and at what crank angle does it occur?

11 1.11 Plot the nondimensional piston velocity, Equation (1.37), for an engine with a stroke mm and connecting rod length mm. What is the maximum velocity, and at what crank angle does it occur?