A complete engine need to be tested before being distributed and to be used in a variety field of usage to make sure that the required engine able to come out with the specific range of power and output of the system. The engine should meets the customers demand and to be economically reasonable price suite with the promoted price. After doing the testing, the engine chould be eco-friendly to the nature that is not produce any type of pollution.
The engine comes with variety size and usage from as small as plug socket to the big one to be used for auxiliary purpose, in the vehicle or to run some mechanical work. This type of engine normally less than 30cc is used as the engine to run the lawn mower because it is just good enough to move the blade. The main problem is now, what is the maximum power or torque that can be given out from the engine, what is the fuel rate consumption that need to be consume.
The engine need to be tested by using the engine test bed or we can call it as engine test rig that comes in various size depends on the size of the engine. Seems that the test rig are used to test medium to large size of the engine and seemly not too efficient to be used to test the small engine. If we still use the test rig for big engine, we still have the result but not accurate. There might be some deviation for the test result. For that reason, we must design a new small engine test rig to study the performance of small engine.
To test the small engine, we should use the small test rig that specially designed for small capacity engine. Usually it is so difficult to test the small and a tiny engine but if we are using the normal rig design that used for big engine, the result will not be precise and could be inflict for the customer. Normally, simulation is used to study the performance of the small engine. Although the result can be predicted for the performance of the engine but to get the perfect result. By hook or by crook, we must using the experimental technique.
In the market, it is hard for us to look for available engine test rig for small engine because the demand for the small engine is too small. We must design our owh engine test rig to test the performance of the small engine. This project is mainly study a performance characteristics of indingenous naturally aspirated two stroke small engine (IA2S25). The capacity of the cylinder of engine is about 25CC. Because of that reason, it is needed a specific small engine rig design.
Statement of the problem
In UTM, there is no test rig design and test equipment to suit the small engine 2-stroke engine. We are taking the responsibility to come out with the design, fabrication, and example of a testing approach to suit the small engine needs. We can come out with the engine performance of this naturally aspirated 2-stroke small (IA2S25).
To perform the engine testing in order to determine the engine performance of naturally naturally aspirated two stroke small engine (IA2S25).
Design of engine facilities to suit with the small engine (IA2S25) needs
To fabricate the engine testing facilities
To design the engine testing code
To perform the engine testing
To analyze the engine performance
To write the report of the project
Basic concept of engine performance
Engine performance characteristics are conventionally presented of an engine performance characteristics. During the actual data from the actual test run of the engine is obtained and is very useful if comparing to the method by comparing one engine from another engine. In this section, some of important characteristics of SI engine are discussed with more specific.
We can noted that there will be a maximum power output per cylinder per cycle that occurs during certain speed of the particular engine. During this point of cycle, maximum value of force can be exerted to the piston. For practical purpose that during this point, we can say that the torque produced or engine capacity to do work will simultaneously maximum at this position of piston.
As the speed of the engine increase more that this speed, the quantity of this charge or power will be decrease. However, the power output of the engine will be increasing with the increasing of number of rotation per minute (RPM) due to the number of cycle per unit of time. With this increasing number of rotation, the air consumption will also increase. Engines are designed so that the maximum air consumption
Foundation of engine performance
Engine performance is a relative term that is normally represented by typical characteristics curve which functions of engine operating parameters. The term performance usually means the relationship between the power output, revolutions per minute, fuel or fluid consumption and ambient conditions in which an engine operates or how effectively it is provides useful energy relation to some other camparable engines.
Most of the engine testing for their performance characteristics takes place under laboratory condition. The engine is connected to a power -absorbing device called dynamometer (G. P. Blair, 1996). However, the performance characteristics of power, torque, fuel consumption rate, and air consumption rate, at various engine speeds are recorded (J.B. Heywood, 1988). There are so many typer of dynamometers; the principle of any dynamometer operation os to allow the casing to swing freely ( A.J. Martye and M.A. Plint, 2007). The reaction torque on the casing, which is exactly equal to the engine torque, is measured on a level length, L, from the centerline of the dynamometer as force, F. This restrains the outside casing from revolving, or torque and power qould not be absorbed (G.P. Blair, 1996 and A.J. Martyr and M.A. Plint, 2007).
Example of engine test rig
According to reference, engine performance theory could be divided to tho areas such as to learn performance engine using dynamometer (G. P. Blair, 1996, J.B. Heywood, 1988 and A.J. Martyr and M.A. Plint, 2007), and to repair and maintain engine through diagnostic analysis system with the result is the efficient operation of engines of all the design (J. Erjavec, 2006). Both theories have different objectives. First, to learn performance engine used dynamometer. The goal is could be developed engine performance or may ber also give service to customers for selected en engine. Second, is to monitoring of engine in order to have the efficient operation using diagnostic technique.
Then there are several factors that must be considered in evaluting the performance of the engine. Most of them are maximum power or torque available at each speed within the useful range of speed. Some range of the power output at constant speed for stable operation of the engine must be decided. The different speeds should be selected at equal intervals within the useful speed range. After that, specific consumption at each operating condition must be specified within the useful range of operation.
Dynamometers have been widely used for evaluation the performance of many kinds od internal conbustion engines. Many different types of dynamometers systems are in use today and detailed descriptions of the various types can be found in many book. While dynamometer make measurements of engine performance at specific loads, a large number of numerical simulations have also been developed to model the engine cycle and predict engine performance. An important advantage of these codes is that they allow the researcher to investigate the effects of specific aspects of the operating physics like friction, heat transfer and the chemistry involved in the combustion process.
THE IMPORTANCE OF ENGINE PERFORMANCE TESTING
The two stroke engine was developed only in two opposite fields that are marine engines which are used a separate scavenging pump and small engines for various application such as power tool. The two stroke cycle engine was invented by Sir Dugald Clerk in England at the end of the 19th century. The form of the engine is using the crankcase compression for the induction process, including the control of the timing and area of the exhaust, transfer and intake ports by piston (G. P. Blair, 1996)
Todays, the most common power source is the well known two-stroke engine. This type of engine has been natural choice due to low cost ang high power density. The two-stroke engine, as we know it today is not able to comply with future emission demands due to its massive hydrocarbon pollutant. However, in the future engine manufacturer must come up with new cost efficient engine technologies that still deliver the same or improved performance for customer satisfaction (M. Bergman, 2003).
Power and torque measurements obtained at different loading conditions show the general trends for most convectional scale engines. Based on figure 1, both parameters increase with increasing engine speed and reach a flat peak before decreasing at higher speeds. Engine torque is usually found to peak first followed by a peak in the engine power. Transmission systems in automobiles and other applications are designed to allow the engine to operate in the relatively narrow where it yields maximum power, torque and efficiency.
Figure : typical shape of power, torque characteristics of a conventional 2 or 4 stroke engine
Waltermann and Neundorf from University Padervorn, Germany, have been developed a test bed for the design and optimization of a series hybrid drive train (P.Waltermann and N Neuendorf, 2006). For the test bed control a powerful real-time environment is applied that comprises component control and the simulation of different models as well as the operating strategy and the emergency system. All important component of a series hybrid drive are mounted. The individual components (combustion engine, generator, battery and traction drives) were contolled with different modules.
Dynamometer is a device to measure force, torque, or power. For example, power produced by an engine, motor or other rotating prime mover can be calculated by simultaneously measuring torque and rotational speed (rpm). In standard emission testing cycles, dynamometers are used to provide simulated road loading of either the engine (using an engine dynamometer) or full powertrain (using a chasis dynamometer). In fact, beyond simple power and torque measurements, dynamometers can be used as part of a test rig for variety of engine development activities such as the calibration of engine management contollers, detailed investigations into combustion behavior.
AIR FLOW RATE MEASUREMENT
For the air flow rate consumption, there are a few methods that can be used to make an approximate estimate of the air mass flow rate supplied to the engine.quasi steady flow rate is meant by the average air flow rate over the entire engine cycle because usually researchers are not so interested in the instantaneous air flow rate into the engine. We can divide the total air supplied to the engine by the time taken that we recorded. Among the method used to measure the air flow rate measurement are air box with sharp edged orifice plate, viscous flow meter, positive displacement flow meter and corona discharge flow meter.
For this experiment, we are using air box with sharp edged orifice plate because it is the simplest quasi-steady air flow rate method is the air box. The air drawn from the box by the engine is replenished by atmospheric air which enters the box through a calibrated sharp-edged orifice plate or a venturi. The volume of the air box must be sufficiently large to damp out the air pulsation generated by the engine, so that the air flow through the orifice plate is as far as possible steady. The air mass flow rate through orifice plate can be calculated by using formula given above:
á¹=CdA √(2âˆ† p) kg/s
This equation is applicable to incompressible flow. Normally Cd=0.6 is used will sufficiently accurate for most purpose. In this experiment for this spark ignition engine, the air flow rate is minimun when the engine is idling ( small opening of the throttle) and maximim at high load and at the maximum opening of the throttle.
Flow meter is a device that used to measure the stream of waterr in the system. There are two type of flowmeter that is horizontal flowmeter and vertical flowmeter. There are a variety of size of flowmeter that need to be choosen appropriately before being used to make sure that we are using the correct size of flowmeter. Before being decided to buy the flowmeter, one must know the maximim value of the flowrate that usually being recorded in gallon per minute, GPM. The brochure usually comes in terms of pipe size, flow range and display model option. By hook or by crook, we must be able to provide the flow range of the stream because it is very important to know.
FUEL FLOW RATE MEASUREMENT
There are various method to measuring ht efuel consumption rate for an angine. Burette method is the simplest way to measure the fuel rate consumption because it will depending on the time that we run the engine for it to consume a certain volume of fuel. This type of masurement is more economical and will give more accurate result based time that engine is running.
Gambar burette method
Another way to measure the instantaneous fuel consumption is by using the weighing methodfor measuring the instantaneous fuel mass rate that had been supplied to the engine. This is a responsive and can be monitored without need to be turn off the engine. It used the hydraulic equivalent of the electrical wheatstone bridge. The bridge is made up by four orifice and the pump to establishes a reference fuel flow which recirculate around the bridge.
Gambar bridge method
When there is no fuel enter the bridge, the reference fuel flows through the bridge is balanced. However, when fuel passes through the bridge on its way to the engine, the bridge become unbalance and it produces a pressure difference signal which is directly proportional to the instantaneous mass flow rate of the fuel passing through the bridge. When the accuracy is not the main point in the measurement, we can used rotameter as the mechanism to measure the fuel flow rate.
Basically this initial project is mainly focussing on doing the evaluation of small 2 stroke small engine by using the brake pony and by attaching the hydraulic pump for poer steering for a car as the experimental approach to determine the brake power and torque produced by this 25cc engine.
Based on this project, the initial plan of measuring the performance of this engine are by using the pony brake and the hydraulic pump. The reason to using both two method for this engine is for differentiate between the result that obtained from both approach. Pony brake is a simple and economical type of dynamometer to measure the torque produced by the engine.
Brake pony is a type of dynamometer used to measure the power of an engine. The pony brake in our experiment is used the principle of friction force to resist the movement of shaft. One end of the cord is attached to the spring and the spring is connected to the fixed table. The other end of the cord is used to put the weighing system to be able for us to get the weight force.
Pumping power is the product of the flow volumetric flow rate of the pressure drop. The flow volumetric flow rate can be calculated by energy balance. The pressure drop is the summation of kinetic head, the static head, the magnetohydrodynamic (MHD) pressure drop and the friction pressure drop.
Pump Power formula:
P = qρgh
P: Pump power, in Watt
ρ: Fluid Density, in Kg/m^3
q: Flow Rate, in m^3/s
h: Head difference, in meter
g: The acceleration due to gravity, is 9.80665 m/s^2
Brake power, BP (kW)
Net power produced by an engine at the crankshaft engine is coupled to a hydraulic pump of power steering of a vehicle.
Brake mean Effective Pressure, Pb (kPa)
Average pressure acting on the piston of the engine that produces the same amount of work. It is useful as a parameter to compare the performance of dissimilar engines.
Torque, http://www.physics.uoguelph.ca/tutorials/torque/tauv.gif (Nm)
torque is a measure of the tendency of a force to rotact an object about an axis. Torque is the cross product of a force and the distance to the centre of rotation.
= Fxd (Nm)
Engine performance test procedure.
Definition of indigenous
originating or occurring naturally in a particular place; native: