THERMODYNAMICS T85D - Internal Combustion Engine Test Bed 1. General Didacta s T85D Internal Combustion Engine Test Bed has been specially designed for use in testing laboratories, and to ensure the greatest possible teaching effectiveness in the field of i.c. engines. In its design, all teaching needs have been taken into account, together with practical requirements, in terms of installation and replacement of the engines to be tested. The T85D is perfectly vibration free and can be installed in any room or laboratory. Engines are quickly and easily installed on the test frame in pairs, to be tested in rapid succession. The engines are coupled to a dynamometric unit for the determination of torque and power values. A data acquisition and analysis system for Personal Computer, called SAD/End, is available and make it possible to perform several functions automatically: taking measurements, displaying torque and power curves on screen or printing them out, filing the test data on disk, or printing them out. The SAD/End system makes it possible to acquire and then process, torque, speed, air flow and fuel flow data on a Personal Computer. SAD/End system is described in detail in a separate data sheet. DIDACTA Italia S.r.l. - Strada del Cascinotto, 139/30-10156 Torino - Italy Tel. +39 011 2731708 - Fax +39 011 2733088 - http://www.didacta.it - E-mail: info@didacta.it
2. Composition The system includes: Basic unit, with supporting frame; The dynamometric unit, with electric starting, a control and instrument panel, and a device to measure the flow of intake air (code 952400); Test engines, each of them installed on a supporting frame with sliding guides (table 1); Load unit (code 952403); Auxiliary cooling unit (optional - code 952411); Electromagnetic coupling (optional - code 952413); Exhaust gas calorimeter (optional - code 952414); Kit to measure the temperature of the exhaust gases (optional - code 952416); Device for the variation of the richness of the mixture for petrol engines (optional - code 952417); SAD/End - Data Acquisition System for Endothermic Engines (for description and technical characteristics see separate catalogue) (optional - code 914363); T156D/2 - kit for the chemical analysis of exhaust gas (optional - code 953250). 3. Description Basic Unit - code 952400 The basic unit includes the following components: Supporting frame; Dynamometric unit; Control and instrument panel; Unit for the measurement of intake air flow. Supporting frame Made of pressure-bent and welded sheet steel, it consists of a lower body and an upper body joined to one another with the interposition of four rubber vibration dampers with a large working surface, so as to absorb all the vibrations produced by engine operation. In this manner, it proves possible to prevent the transmission of dangerous vibrations to the floor and the other assemblies. The lower frame does not have to be bolted to the floor, because of the absence of vibrations; the upper frame has special sliding guides, which are suitable to support the engines, the dynamometric unit and all other accessories. Dynamometric unit This unit can be operated as a motor to start the engines being tested or as a brake to determine the torque and power characteristics of the different engines. It consists of an oscillating frame d.c. motor-generator, with dissipation resistance and load cell. Braking power can be as high as 10 kw. Control and instrument panel This is made up of a steel structure placed astride the basic unit, with no mechanical connections, so that is can be insulated from induced vibrations. The structure contains the fuel tanks, the devices for the determination of fuel consumption and the electrical control board equipped with adequate instrumentation, telltales, and all the controls that are necessary to perform the following functions: starting choosing between the motorisation and the braking function choosing between the clockwise and the counter-clockwise direction electrical engine starting with variable speed alternative activation of the electromagnetic coupling braking regulation with digital reading of: - rpm - torque - excitation current Moreover, it includes several connections and a large support surface for the other standard and optional equipment. Intake air flowmeter This unit consists of two damping reservoirs fitted with calibrated orifices and flexible hose connections to the engines being tested, and two universal differential micro-manometers with tilting scale. In this way it is possible to determine with great accuracy the volume of air taken in by the engine. Test engines The engines are installed on special supporting frames, fitted with sliding guides to facilitate the connection with the dynamometric unit. 5 different types of i.c. engines are available. Each bed is fitted with universal joints for a rapid installation of the engines onto the basic assembly; the output shafts are fitted with the aid of rapid coupling elastic joints. The main characteristics of these engines are summarised in table 1. Page 2
Load unit - code 952403 This consists of a dissipator that includes a battery of resistive elements housed in a self-ventilated tank equipped with pivoting wheels. The feeding unit is connected by means of a flexible cable ending in a multiple plug. OPTIONALS Auxiliary cooling unit (optional - code 952411) In water-cooled engines an auxiliary cooling assembly can be had on request: this performs the functions normally performed by the radiator, and makes it possible to take measurements on the cooling system. When used in conjunction with the optional exhaust gas calorimeter it also makes it possible to work out a thermal balance of the engine. The unit includes the following elements: expansion tank with mixing cooling system through closed loop automatic control; pipes; flexible hoses; electrically operated circulation pump; flowmeter for the determination of the coolant flow-rate; no. 5 thermocouples connected to a digital indicator for the determination of the temperature at the most significant points of the circuit. Optional auxiliary cooling unit. Optional exhaust calorimeter. Electromagnetic coupling (optional - code 952413) The engine being tested can be coupled to the dynamometric unit either by keying one engine at a time directly onto it, or by means of electromagnetic couplings which are alternatively activated, and make it possible to install two engines at a time and to couple only one of them at a time. Each coupling is fitted with a base and a flexible coupling similar to those of the engines, which therefore can be mounted very quickly. The electromagnetic coupling is of the single-disk type, with permanent magnet and armature of ferromagnetic material, with built-in clutch ring; the rotor disk is made of nitrided steel.
Exhaust gas calorimeter (optional - code 952414) To work out an accurate thermal balance, it is necessary to be able to determine the calories evacuated with the exhaust gases with great accuracy. The exhaust gas calorimeter makes it possible to cool the exhaust gases with water, so that the gases are released at a lower temperature. It consists: gas/water heat exchanger; flowmeter for the measurement of the exhaust gas cooling water flow-rate; no. 2 thermometers for the measurement of the exhaust gas cooling water temperature before and after the heat exchanger. The calorimeter assembly is fitted onto an independent wheeled structure, and can be easily connected to the engine being tested. To use the calorimeter, it is indispensable to have the optional kit for the measurement of the exhaust gas temperature - code 952416. Kit for the measurement of the temperature of the exhaust gases (optional - code 952416) This kit is made up of a digital instrument that measures the temperature, with automatic compensation on the cold junction, and a Cr/Al thermocouple suitable for the measurement of very high temperatures. Each engine comes with a housing where to introduce the probe. Device for the variation in the richness of the mixture for petrol engines (optional - code 952417) In engines with fuel feed by means of a carburetor, this device makes it possible to obtain a continuous variation in the richness of the mixture. It produces no secondary effects on the characteristics of the carburetor and therefore it is widely used in engine testing. It consists of an electrically operated vacuum/pressure pump, a control panel, a sensitive valve and a manometer for connection to the carburetor. SAD/End - Data Acquisition System for Endothermic Engines (for description and technical characteristics see separate catalogue) (optional - code 914363) The SAD/End computer-based system allows real time data acquisition from engine testing benches. T156D/2 - Kit for the chemical analysis of exhaust gases (optional code 953250) The exhaust gas analyzer is of the infrared ray type and is suitable for petrol engines. It can be used to measure the values of carbon monoxide (CO), carbon dioxide (CO 2 ), unburned hydrocarbons (HC) and oxygen (O 2 ). On the basis of such values, the instrument automatically determines the air/fuel ratio, which is an indispensable term of reference in engine tuning. 4. Experiments Classroom exercises Fundamentals of mechanics: the concepts of work, energy and power; Operating principles of internal combustion engines; Determination of port size for a 2-stroke engine, as a function of the timing diagram. Determination of dynamic and kinematic engine quantities: forces acting on the connecting rod, the piston and the crankshaft; displacement, speed and acceleration diagrams of the piston. Definition of the main parameters characterizing the operation of internal combustion engines: torque and power delivered, specific fuel consumption, efficiency, air/fuel ratio; Dimensioning the cooling system (air or water) for an internal combustion engine; New types of fuel for internal combustion engines, as an alternative to petrol or diesel oil. Laboratory experiments Starting procedure of an internal combustion engine, and related safety instructions; Use of the dynamometric unit to determine engine torque and power values; Determination of torque and power values with the throttle open wide, at different engine rotation speeds; Determination of specific fuel consumption and engine efficiency; Determination of volumetric efficiency and the air/fuel ratio; Measuring the flow-rate of a fluid (cooling air water, exhaust gas, fuel); Determination of the quantity of heat absorbed by a fluid through the measurement of temperature variations and flowrate; Determination of air and fuel requirements; determination of mixture ratios; Measurement of the volumetric and mechanical efficiency by using the dynamometer as an electric motor so as to obtain different engine rotation speeds; Determination of thermal balance, by measuring: the amount of heat absorbed by the cooling air (or water) (with option 952411); amount of heat absorbed by the exhaust gases (with options 952414 and 952416); mechanical energy used up. Determination of power delivered and fuel consumption by using (in 4-stroke engines only) a mixture of petrol (80%) and alcohol (20%) instead of petrol; Page 4
Execution of the main tests and determination of the torque and power curves on a Personal Computer (with system SAD/End, available on request); 5. Requirements Electrical power supply: 380 V AC three-phase, 50/60 Hz, 4 kw Water supply: 500 l/h - 3 bar Water discharge Exhaust gas outlet. 6. Weights and dimensions Basic unit Dimensions: 2530 x 780 x 1200 h mm Weight: 420 kg Dynamometric unit Dimensions: 1200 x 1050 x 2000 h mm Weight: 110 kg Load unit Dimensions: 650 x 450 x 950 h mm Weight: 57 kg Auxiliary cooling unit (optional) Dimensions: 800 x 500 x 2000 h mm Weight: 100 kg Exhaust gas calorimeter (optional) Dimensions: 800 x 800 x 1800 h mm Weight: 80 kg SAD/End - Data acquisition system for endothermic engines (optional) Dimensions: 550 x 360 x 350 h mm Weight: 15 kg T156D/2 - Kit for the chemical analysis of exhaust gases (optional) Dimensions: 400 x 180 x 450 h mm Weight: 8,6 kg
Table 1 - Main technical data of the available engines Code 952428 952406 952426 Cycle Otto Diesel Diesel No. of strokes 4 4 4 Fuel feed system Petrol Gasoil Gasoil Cooling Air Air Water Cylinders 1 1 2 Displacement [cm 3 ] 338 315 505 Max power output [kw] 8 5 8 Max power engine speed [rpm] 3600 3600 3200 Max torque [Nm] 23.7 15 29 Max torque engine speed [rpm] 2600 2400 2400 Weight [Kg] 30 33 62 (Data stated by manufacturer after running in with standard air fitter and muffler) Cod. R00215/E 1012 Ed. 01 Rev. 03 In any time and without notice, Didacta Italia can carry out any appropriate modification on the product details, always maintaining their main features, according to the designing and teaching necessity. Page 6