MECE541_Ass-1-2023_M Shahbakhti

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University of Alberta *

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541

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Mechanical Engineering

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Nov 24, 2024

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DEPARTMENT OF MECHANICAL ENGINEERING INTERNAL COMBUSTION ENGINES MECE 541 M. Shahbakhti HOMEWORK #1 Due: Sep. 26, 2023 (submit hardcopy at the beginning of class) Posted: Sep. 3, 2023 Note: Review the assignment guideline in the course eClass General module.
MECE 541: Assignment 1 2 M. Shahbakhti THE UNIVERSITY OF ALBERTA INTERNAL COMBUSTION ENGINES - MEC E 541 (Fall 2023) ASSIGNMENT #1 Due Tue. Sep. 26, 2023 by 8:00 AM (submission in class) 1. Early Internal Combustion Engines [12 marks] a. Otto and Langen developed a free piston internal combustion engine and then a reciprocating piston internal combustion engine. What was important about their engines that allowed them to compete with the already-established Lenoir engines? b. Rudolph Diesel created a compression-ignition engine with considerably higher efficiency than the Otto cycle engine. What advantage gave his engine such high efficiency? 2. Engine Performance and Dimensions [28 marks] WardsAuto had awarded "Ten Best Engines of 2021" status to the Ford F-150 Hybrid PowerBoost™ twin-turbocharged 3.5-liter V-6 engine. This six-cylinder turbocharged port fuel injection & direct-injection SI engine has the peak brake torque of 570.0 lbf.ft @ 3000.0 rpm and the peak brake power of 430.0 hp @ 6000.0 rpm. The engine compression ratio is 10.5:1; the bore is 3.64 inches and the stroke is 3.41 inches. [Interesting video to watch: https://www.youtube.com/watch?v=KMVZ2eHUiUk&t=33s ] Image: wardsauto.com a. What is the engine power band? b. Is the displacement precisely 3.50 liters? c. What is the engine bmep at peak torque? at peak power? d. What is the mean piston speed at peak torque? at peak power? e. If you were selecting transmission gears to give an economical cruise speed, what engine speed would you select as a base? 3. Engine Specific Power [21 marks] The power per unit piston area P/A p (often called the specific power) is a measure of the designer's success in using the available piston area regardless of size. a. Derive an expression for P/A p , in terms of mean effective pressure and mean piston speed for two- stroke and four-stroke engine cycles.
MECE 541: Assignment 1 3 M. Shahbakhti b. Compute typical maximum values of P/A p for the following two engines. State your assumptions clearly. 2021 Cummins X15 Performance 14.9-liter inline 6-cylinder compression ignition engine; Application: Long-haul trucks; Bore 137 mm, stroke 169 mm, compression ratio 18.9:1, maximum power 421 kW at 1900 rev/min [Cummins.com] Large Wärtsilä-Sulzer RTA96-C two-stroke turbocharged 14-cylinder marine diesel engine. Bore 960.0 mm, stroke 2500.0 mm, rated power 80.080 MW at 102.00 rev/min [wartsila.com; topspeed.com]
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MECE 541: Assignment 1 4 M. Shahbakhti 4. Engine BSFC and Fuel Conversion Efficiency [10 marks] The brake fuel conversion efficiency of a compression-ignition engine is 0.360, and varies little with fuel type. Calculate the brake specific fuel consumption for diesel, and methane in g/(kW.h). The lower heating value for diesel and methane fuels are 43.20 MJ/kg and 50.01 MJ/kg, respectively. 5. Engine Multiple-choice Questions [21 marks] Four marks for correct answer, three marks for brief justification for each question 5.1 Your friend is working in an oil and gas Company where they recently installed a newly developed Cummins turbocharged, 12-cylinder 45-Liter direct injection 4-stroke diesel engine for a stationary application. Which of the following can be the specifications of the new engine? Why? a) Compression ratio: 10 Bore/Stroke ratio: 1.8 Ratio of rod length to crank throw: 4.4 c) Compression ratio: 16 Bore/Stroke ratio: 1.2 Ratio of rod length to crank throw: 8.2 b) Compression ratio: 14 Bore/Stroke ratio: 0.5 Ratio of rod length to crank throw: 6.4 d) Compression ratio: 8.0 Bore/Stroke ratio: 0.4 Ratio of rod length to crank throw: 7.4 5.2 2009 Ferrari F430 runs with a 4.3 Liter V8 engine with a compression ratio of 11.3. The engine is rated as having the peak IMEP 11 bar @5000 rpm. Peak brake power of the engine is 490 bhp @8500 rpm. What do you expect to be the engine speed at peak BMEP? Why? a) 8500 rpm c) 5500 rpm b) 5000 rpm d) 4500 rpm 5.3 2021 Toyota Prius 1.8 Liter in-line, 16-valve, 4-cylinder DOHC gasoline engine is rated as having peak torque of 142N.m at 3600 rpm and peak power of 96 hp at 5200 rpm. How much do you expect for the mechanical efficiency of this engine at idling condition (e.g., 700 rpm)? Why? a) 0% c) 30% b) 40-50% d) 90% 6. Alternative Propulsion Systems [8 marks] Purely electric vehicles are becoming more common. What are the major advantages and disadvantages of electric vehicles compared to vehicles using internal combustion engines?