ps5 - Massachusetts Institute of Technology DEPARTMENT OF...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Massachusetts Institute of Technology DEPARTMENT OF OCEAN ENGINEERING 2.611 SHIP POWER and PROPULSION Problem Set #5, Diesel Engine Problems, Due: November 14, 2006 1. A diesel engine designer is interested to know the effect of turbo-charging on mean effective pressure and power. The engine he is considering is a 14 cylinder, 4 stroke diesel engine. The rotational speed is 1200 rpm, mean piston speed of 12 m/s, and stroke to bore ratio of 1.25. The following data is estimated: Note: Review chapter 7 in the text before attempting this problem. Thermodynamic efficiency = 58.5% Mechanical losses = 8 % Heat losses = 9 % Charge pressure = 3.5 bar over pressure in inlet receiver Charging is reasonably effective (93%) Inlet receiver temp 60 Celsius Air excess ratio 1.8 Lower heating value of fuel 42,000 kJ/kg Stoichiometric fuel air ratio = 13:1 Gas constant air/exhaust gas R = .287 kJ/kg a. Calculate engine efficiency, mean effective pressure, and power output. (Note: you can assume that the combustion efficiency is 100%). b. If an engine of the same size was not turbocharged, what would be the efficiency, mean effective pressure and power (keep assumptions unchanged).
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2. The air standard dual-cycle is used to represent the thermodynamic characteristics of a large two-stroke diesel engine. The cylinder volume V 1 =1.0 m 3 ; the compression ratio ; the value of 12 /1 3 . v rVV == 0 0 32 . 8 p rT T = = ; and the cut-off ratio ; the temperature of the air entering the cylinder ; and the pressure 43 . 4 c rTT 0 1 300 TK = ( ) 2 1 1.0 bar 100 / p kN m = . Determine: a. the temperatures , , and in K 2 T 3 T 4 T 5 T b. the mass of the gas, m , in the cylinder in kg c. the heat transfers, 1 H Q , at constant volume; 2 H Q at constant pressure, and at constant volume, in kJ L Q d. the work of the engine per cycle in kJ, and the power per cylinder in kW, when the two-stroke engine operates at 79 rpm The engine is now fitted with a turbocharger and charge cooler. The compressor pressure ratio of the turbocharger is 3.9 and the polytropic efficiency 0.83 PC η = . The effectiveness of the charge cooler ( ) ( ) 1 1 /0 COMP COMP W TT ε =− = . 8 K where the cooling water temperature , the air temperature leaving the compressor and entering the charge cooler is and the temperature of the air leaving the charge cooler and entering the engine cylinder is T . 300 o W T = COMP T Determine: e. the temperature of the air leaving the charge cooler and entering the engine cylinder 1 1 T f. Repeat the tasks a through d for the new situation.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 02/24/2012 for the course MECHANICAL 2.611 taught by Professor Davidburke during the Fall '06 term at MIT.

Page1 / 5

ps5 - Massachusetts Institute of Technology DEPARTMENT OF...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online