The 6th International Conference on Science, Technology and Innovation for Sustainable Well-Being (STISWB VI), 28-30 August 2014, Apsara Angkor Resort & Conference, Siem Reap, Kingdom of Cambodia

MEE-xxxx

Design of Inertia Dynamometer for Single-cylinder Engine Maitree N.* and Kunanoppadol J. Department of Mechanical Engineering, Faculty of Engineering and Industrial Technology, Silpakorn University, Thailand. 73000 *Email: [email protected], Tel: 6634259025, Fax: 6634219367

Abstract This paper aims to overview the theory and method to design the inertia dynamometer. This is the first phase of the whole project to investigate the performance of single-cylinder engine running with combined fuel consisting of gasoline, ethanol, and HHO1. The processes to design the inertia dynamometer is presented sequentially. In this case, the existing inertia drum from the prior project was used as initial design condition, then other parts were designed and matched by engineering design procedures. The safety factor of the critical part was analyzed by the computer simulation software. By doing this, the final design of inertia dynamometer is prompt to be constructed in next phase. The paper should be useful for researchers who interest to develop their own engine’s dynamometer. Additionally, this concept can be applied to design and develop chassis dynamometer for engine tuning application as well. Keywords: Inertia dynamometer, engine’s performance, single-cylinder engine, engine tuning.

1. Introduction Typically, to investigate racing engine’s performance, torque-speed characteristic is more important than exactly data at any speed point because the engine is normally operated in various of speed range to accelerate the racing car [1], [2]. High and fast respond torque at the operating speed is the target of engine tuning. For engine’s performance measuring, dynamometer has been used. Dynamometer can be divided into two groups. First group is normally used to measure the engine’s performance at stationary speed such as dry friction, and fluid friction dynamometer, while the 1

second group is used for measuring in continuous speed such as eddy-current and inertia dynamometer. Inertia dynamometer is appropriate for small engine due to many reasons such as simple mechanism, inexpensive, and small size, [3], [4]. The important part of this dynamometer is the inertia drum used for simulating the vehicle’s movement [5], [6]. The angular dynamic of inertia drum will be designed equals to the vehicle’s linear dynamic. Typically, inertia dynamometer is not only used to measure the engine’s torque-speed characteristic to accelerate the drum, but can be used to measure the

The HHO (oxyhydrogen or hydroxy) is combination between two molecule of hydrogen and one molecule of oxygen gas.

50th Anniversary Technique Thai-German to Rajamangala Khon Kaen

The 6th International Conference on Science, Technology and Innovation for Sustainable Well-Being (STISWB VI), 28-30 August 2014, Apsara Angkor Resort & Conference, Siem Reap, Kingdom of Cambodia

brake’s capability to decelerate the drum as well. There are many research using this concept for testing the brake system [7]– [10]. To measure the torque-speed characteristics, the angular acceleration of the drum measured by the change of angular velocity is converted to torque value by the dynamic fundamental. For engine tuning, the repeatability is more important than exact value [11]. The scope presented in this paper is first part of the whole project to investigate the performance of single-cylinder gasoline engine (motorcycle engine) running with alternative fuel (the combination of gasoline, ethanol, and HHO). This phase is to design the dynamometer for measuring the performance. Therefore, this paper aims to overview the theory and methods to design the inertia dynamometer for using in next phases. The following part of the paper consists of the design theory, the critical part analysis, the result and final design, then this paper is finished with conclusion.

2. Design Theory The important design process is to select the size and shape of the inertia drum, and to match the transmission system between dynamometer and tested engine. Since the vehicle’s linear acceleration has to be simulated by drum’s angular acceleration, the drum’s moment of inertia must cover the vehicle’s movement parameters including weight, transmission system, and wheel size. The vehicle specifications and assumptions used as the design condition are shown in Table 1. The method to evaluate the inertia drum is followed the method of Blair (1990). By considering the vehicle’s movement, the Newton’s second law is shown in Equation 1. The driving force (𝐹𝑑 ) relates to the total mass including vehicle and passengers’ mass (𝑚𝑡 ), and vehicle acceleration (𝑎𝑣 ). 2

The vehicle acceleration can be considered in term of engine’s angular acceleration 𝑑𝜔 ( 𝑒 ), wheel radius (𝑟𝑤 ), and vehicle’s total 𝑑𝑡 transmission ratio (𝑖𝑡𝑣 ). Table. 1 Vehicle specification and design assumption Brand Model Vehicle weight Passengers 2 Wheel size

Honda Wave 110i 98 kg 140 kg 80/90-17M/C -50P (575.8 mm diameter) 110.1 cc. 6.9 kW, 8460 rpm 9.0 N-m, 5500 rpm

Engine - max power - max torque Gear ratio - 1st gear - 2nd gear - 3rd gear - 4th gear Secondary ratio Final transmission

2.615 1.555 1.136 0.916 4.059 2.642 (front and rear sprocket)

By considering the engine’s torque transmission, the engine’s driving torque (𝑇𝑒 ) is transferred through the transmission system including gear-box, secondary gearset, final transmission (chain and sprocket mechanism), and wheel to be the driving force as shown in Equation 2. The engine’s torque to accelerate the vehicle in Equation 3 is from combining Equation 1 and 2. The vehicle’s total transmission ratio in this equation consists of gearbox ratio (𝑖𝑔 ) and vehicle’s chain ratio (𝑖𝑐𝑣). 𝐹𝑑 = 𝑚𝑡 𝑎𝑣 = 𝑚𝑡 𝑚𝑡

𝑑𝜔𝑒 𝑟𝑤

𝑑𝑣𝑣 𝑑𝑡

= 𝑚𝑡

𝑑𝜔𝑤 𝑑𝑡

𝑟𝑤 =

𝑑𝑡 𝑖𝑡𝑣

Passengers’ weight was estimated from two passengers who have each weight is 70 kg (ref).

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(1)

The 6th International Conference on Science, Technology and Innovation for Sustainable Well-Being (STISWB VI), 28-30 August 2014, Apsara Angkor Resort & Conference, Siem Reap, Kingdom of Cambodia

𝑇

𝐹𝑑 = 𝑟𝑤 =

𝑇𝑒 𝑖𝑡𝑣

𝑤

𝑇𝑒 = 𝑚𝑡

𝑑𝜔𝑒 𝑑𝑡

(2)

𝑟𝑤 2

𝑟

(𝑖 𝑤 ) = 𝑚𝑡

𝑑𝜔𝑒 𝑑𝑡

𝑡𝑣

(𝑖

𝑟𝑤

2

)

𝑔 𝑖𝑐𝑣

(3)

By considering the drum’s dynamics, the torque to drive the inertia drum (𝑇𝑑 ) relates to drum’s moment of inertia (𝐼𝑑 ) and angular acceleration (𝛼𝑑 ) as shown in Equation 4. In this equation, the drum’s angular velocity relates to engine’s speed by the transmission concept. The engine’s torque (𝑇𝑒 ) is transferred through the dynamometer’s transmission system (𝑖𝑡𝑑 ) as shown in Equation 5. The engine’s torque to accelerate the drum as shown in Equation 6 is from combining Equation 4 and 5. Importantly, the dynamometer’s total transmission ratio in this equation consists of the existing gearbox (𝑖𝑔 ) and dynamometer’s chain mechanism (𝑖𝑐𝑑 ). 𝑇𝑑 = 𝐼𝑑 𝛼𝑑 = 𝐼𝑑

𝑑𝜔𝑑 𝑑𝑡

𝐼

= 𝑖𝑑

𝑑𝜔𝑒

𝑡𝑑

𝑑𝑡

𝑇𝑑 = 𝑇𝑒 𝑖𝑡𝑑 𝑇𝑒 = (𝑖

𝐼𝑑

𝑑𝜔𝑒 2 𝑑𝑡 ) 𝑡𝑑

(4) (5)

=

𝐼𝑑

2

(𝑖𝑔 𝑖𝑐𝑑)

𝑑𝜔𝑒 𝑑𝑡

(6)

Since the vehicle’s acceleration is simulated by drum’s acceleration, Equation 3 and 6 can be combined to reduce engine’s torque term as shown in Equation 7. Finally,

the relationship between drum’s moment of inertia needed to install in dynamometer (𝐼𝑑 ) and dynamometer’s chain ratio (𝑖𝑐2) is shown in Equation 8 while the total mass (𝑚𝑡 ), wheel radius (𝑟𝑤 ), and vehicle’s transmission ratio (𝑖𝑐𝑣) are constants. 𝑚𝑡

𝑑𝜔𝑒 𝑑𝑡

(𝑖

𝑟𝑤 𝑔 𝑖𝑐𝑣

𝑟

2

) =

𝐼𝑑 (𝑖𝑔 𝑖𝑐𝑑)

2

𝑑𝜔𝑒 𝑑𝑡

(7)

2

𝐼𝑑 = 𝑚𝑡 (𝑖 𝑤 ) (𝑖𝑐𝑑 )2 𝑐𝑣

(8)

To set the dynamometer’s chain mechanism (chain and two sprockets), the sprockets that available on market must be selected. The 25-teeth are selected for installed at the engine and 28-teeth for installed at the drum; therefore, the actual chain ratio is found to be 1.120. According to Equation 8 and Figure 1, the drum’s inertia needed to be installed at the selected point equals to 3.55 kg-m2. This value is less than the existing drum (3.62 kg-m2) and means that the existing drum is enough for using with the design conditions. From this equation, there are many alternatives can be used. Figure 1 shows the relationship between dynamometer’s chain ratio and drum’s moment of inertia from Equation 8. For this case, the inertia drum form prior project3 will be used and the total moment of inertia equals to 3.62 kg-m2; therefore, the designed chain ratio is calculated and found to be 1.132.

3

There are four sets of inertia drum with the total moment of inertia equals to 3.62 kg-m2. Each drum has the cylinder shape with the dimensions of 50 mm thickness, and 55 mm and 390 mm for inside and outside diameter respectively. The drum is made from steel: SS400 (JIS G3101) and has 42.02 kg weight.

50th Anniversary Technique Thai-German to Rajamangala Khon Kaen

The 6th International Conference on Science, Technology and Innovation for Sustainable Well-Being (STISWB VI), 28-30 August 2014, Apsara Angkor Resort & Conference, Siem Reap, Kingdom of Cambodia

Drum's moment of inertia (kg - m2)

12 10

8 6 Selection point (1.120,3.55)

4

Design point (1.132, 3.62)

2 0 0.0

0.3

0.5

0.8

1.0

1.3

1.5

1.8

2.0

Dynamometer's chain ratio

Fig. 1 Dynamometer’s chain ratio and Drum’s moment of inertia

3. Critical Part Analysis According to Kee and Blair (1994), the main shaft for installing the inertia drum is the critical part and it need to be investigated in term of safety. To do so, SolidWorks is used for finite element analysis. The force diagram is shown in Figure 2. The distribution load of the inertia drums equals to 8204.30 N/m. The flange-end with sprocket has 40.42 N (4.12 kg) while another flange-end with disc brake has 43.75 N (4.46 kg). The maximum torque applied to the main-shaft is calculated from the engine’s maximum torque (9.0 N-m) at the first gear ratio (2.615), the secondary ratio (4.059), and the selected chain ratio (1.120); by doing this, it is found to be 106.99 N-m. The chain tension at sprocket is calculated from driving torque and equivalence radius of the sprocket (144 mm) then divided in to x and y components based of engine and drum alignment, and found to be 1925.14 N for xaxis and 167.23 N for y-axis. By simple calculation, the reaction forces at main bearing near the sprocket side are found to be 1873.80 N for x-axis and 805.62 N for y-axis

while the reaction forces at another main bearing near the disc brake side are found to be 51.34 N for x-axis and 759.67 N for yaxis. The program subdivides the main shaft into small pieces of simple shapes (element) that connected at common point (nodes). Standard meshing is selected for operation with main shaft, and using “VoronoiDelaunay” meshing scheme. The details of meshing are shown in Table 2. The main shaft is made from steel: SS4004 (JIS G3101 standard). Table. 2 Created mesh to selection Mesh type Mesh factor Mesh used Automatic transition Jacobian points Element size Tolerance Mesh quality Total node Total element

Solid mesh Fine Standard mesh Off 4 points 5.473 mm 0.274 mm High 74,696 50,533

4

The SS400 is a carbon-steel for general structure steel plate in JIS G3101 standard that has the yields strength equals to 245 MPa, the tensile strength equals to and 440-510 MPa.

50th Anniversary Technique Thai-German to Rajamangala Khon Kaen

The 6th International Conference on Science, Technology and Innovation for Sustainable Well-Being (STISWB VI), 28-30 August 2014, Apsara Angkor Resort & Conference, Siem Reap, Kingdom of Cambodia

Fig. 2 Critical Part Analysis

4. Result and Discussion The analytical results are also shown in Figure 2. The maximum tensile stress on main shaft is found to be 19.29x106 N/m2 (19.29 MPa). Factor of safety is calculate form the maximum stress and the yield strength of material and found to be 12.70. Moreover, the maximum deflection is found to be 0.123 micron. These results indicate that the main shaft can be used safely in this design conditions [13]. The exploded view inertia dynamometer for measuring the performance of single-cylinder engine for next stages is shown in Figure 3. The final design consists of (1) Steel frame, (2) Single-cylinder engine, (3) Inertia set including four pieces of existing inertia drum, main shaft, and all fittings, (4) Disc brake set that can be modified for brake testing, (5) Sprocket set that can be change in case of changing the new tested engine, (6) Brake caliber set for further research, (7) Chain mechanism

Now, this inertia dynamometer is on the process of part building and installation. Interestingly, this design will be not installed any sensor for measuring drum’s speed and acceleration because the engine will be control with the stand-alone ECU that can be measure and record all operating data such as engine’s speed, fuel injection period, ignition timing, intake manifold pressure, and so on. The time record and engine’s speed tracked by ECU can be calculated to acceleration then converted to engine’s torque. Therefore, the engine’s torque-speed characteristics can be measured. In sum, this paper should be useful for researchers who interest to develop their own dynamometer for using in laboratory. This concept can be applied to develop the chassis dynamometer to measure the vehicle’s performance for engine tuning application as well.

5. Conclusion To design inertia dynamometer, the processes should start form vehicle’s data and all assumption. Next step is to design the drum’s moment of inertia used to simulate

50th Anniversary Technique Thai-German to Rajamangala Khon Kaen

The 6th International Conference on Science, Technology and Innovation for Sustainable Well-Being (STISWB VI), 28-30 August 2014, Apsara Angkor Resort & Conference, Siem Reap, Kingdom of Cambodia the vehicle’s movement. The main shaft is the critical part that have to be analyzed the safety. Finally, the layout of dynamometer including engine, drum, main shaft, and others can be designed.

6. Acknowledgement This work was supported by the Department of Mechanical Engineering, Faculty of Engineering and Industrial Technology, Silpakorn University, Thailand.

Fig. 3 Final Design of Inertia Dynamometer

7. References [1] G. P. Blair, The basic design of twostroke engines. Warrendale, PA: Society of Automotive Engineers, 1990. [2] J. Collins, E.R. and Y. Huang, “A programmable dynamometer for testing rotating machinery using a three-phase induction machine,” IEEE Trans. Energy Convers., vol. 9, no. 3, pp. 521–527, Sep. 1994. [3] H. A. Walker and J. A. Wilson, “Dynamometer for simulating the inertial and road load forces encountered by motor vehicles,” US5452605 A1995. [4] C. J. William and S. Dmitry, “Dynamometer for simulating the inertial

and road load forces encountered by motor vehicles and method,” US5445013 A1995. [5] S. Jarvis and H. Rolfe, “The use of an inertial dynamometer to explore the design of children’s wheelchairs.,” Scand. J. Rehabil. Med., vol. 14, no. 4, pp. 167–176, Dec. 1981. [6] D. Murray and E. Harrison, “Constant velocity dynamometer: an appraisal using mechanical loading.,” Med. Sci. Sports Exerc., vol. 18, no. 6, pp. 612–624, Dec. 1986. [7] P. F. Gotowicki, V. Nigrelli, G. V. Mariotti, D. Aleksendric, and C. Duboka, “Numerical and experimental analysis of a pegs-wing ventilated disk brake rotor, with

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The 6th International Conference on Science, Technology and Innovation for Sustainable Well-Being (STISWB VI), 28-30 August 2014, Apsara Angkor Resort & Conference, Siem Reap, Kingdom of Cambodia pads and cylinders,” in 10 th EAEC European Automotive Congress--Paper EAEC05YUAS04--P, 2005, vol. 5. [8] D. Sinclair and W. F. Gulick, “The Dual Brake Inertia Dynamometer - A New Tool for Brake Testing,” SAE International, Warrendale, PA, SAE Technical Paper 630464, Jan. 1963. [9] J. K. Thompson, A. Marks, and D. Rhode, “Inertia Simulation in Brake Dynamometer Testing,” SAE International, Warrendale, PA, SAE Technical Paper 2002-01-2601, Oct. 2002. [10] P. H. S. Tsang, M. G. Jacko, and S. K. Rhee, “Comparison of Chase and inertial brake Dynamometer testing of automotive friction materials,” Wear, vol. 103, no. 3, pp. 217–232, Jun. 1985.

[11] H. Kaji and H. Kita, “Acceleration of Experiment-Based Evolutionary Multiobjective Optimization of internalcombustion engine controllers using fitness estimation,” in IEEE Congress on Evolutionary Computation, 2007. CEC 2007, 2007, pp. 1777–1784. [12] R. J. Kee and G. P. Blair, “Acceleration Test Method for a High Performance Two-Stroke Racing Engine,” SAE International, Warrendale, PA, SAE Technical Paper 942478, Dec. 1994. [13] J. E. Shigley and J. J. Uicker, Theory of machines and mechanisms. McGraw-Hill, 1995.

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