Capitolul 3 Software And Equipement For The Experiment [309009]

CAPITOLUL 3 – Equipment used for experimental research

3.1 Equipment’s used engine tests

An engine test facility is a [anonimizat], housed in a building adapted or built for its purpose. For such a [anonimizat], its many parts must be matched to each other while meeting the operational requirements of the user and being compliant with various regulations. Engine and vehicle developers now need to measure improvements in engine performance that are frequently so small as to require the best available instrumentation in order for fine comparative changes in performance to be observed. This level of measurement requires that instrumentation is integrated within the total facility such that their performance and data are not compromised by the environment in which they operate and services to which they are connected.

Engine test facilities vary considerably in power rating and performance; [anonimizat], lubrication oils or exhaust emissions.

[anonimizat], homologate or develop performance criteria of all or part of the tested engine. [anonimizat], which in turn will rely on the instrumentation chosen to produce it and the system within which the instruments work.

An engine test bench must include:

– engine test chamber;

– control chamber;

– space needed for measure equipment’s;

– space needed for prepare workshop;

– space needed for parts;

Fig.3.1.Engine test bench presentation

Structural organization of an engine test bench

Minimum requirements for an engine test bench:

– Fuel supply system;

– Ventilation and air conditioning system;

– Engine cooling system;

– Exhaust gas evacuate system;

– Phonic isolation;

– Seismic block;

– Fire extinguishing system;

– [anonimizat];

– Engine charging equipment;

– Control unit.

[anonimizat]: cooling and breathing. The control of one of them (cooling) may be critical to the effects that the other (breathing) will have on the engine.

As a [anonimizat], in that they breathe in air for combustion purposes. Therefore, [anonimizat], humidity, and condition will affect the performance of the engine.

Fig.3.2.Ventilation and air conditioning system

Attempting a [anonimizat], but also to prevent the accumulation of dangerous amounts of gas and vapors. [anonimizat].

Combustion air is the air that actually participates in the combustion process (the suction air). Also to ensure repeatability and reproducibility conditions is temperature and humidity conditioned (25° C temperature and 40% relative humidity respectively). [anonimizat] ​​constantly conditioned by a heater and a vaporizer.

The combustion air conditioning system is separate from that of the air in the cell and allows the control of the two parameters regardless of the conditions in the cell, for this reason the air is directed to the intake manifold through a duct coming from the upper floor of the test cell, where it has already been optimized. For a more precise adjustment, the combustion air duct is equipped with a humidifier and a temperature probe.

The volume of air supplied by the boiler is kept constant at a level that assures the engine for the operating conditions and at the same time prevents the engine from aspiring air from the cell that has not been optimized for intake.

Combustion or induction air describes the air that the engine will draw in or induct, through the inlet tract into the inlet manifolds and into the cylinders for the combustion process. The source of this air usually is the ambient air that is present within the test cell itself (e.g. the same air that the technician is breathing-fumes, vapors and all).

The quality of the air is critical to the performance of the engine and will be reflected in the engine test results. Obviously, from the viewpoint of the customer who is commissioning the tests, undesirable air quality will produce undesirable test results and inevitably lead to wasted money, time and effort in conducting the tests. Where in-cell air quality is of an extremely dubious or poor condition with regard to the four points mentioned (air temperature, pressure, humidity or condition) or the test requires absolute guaranteed and consistent air quality, then the air for the combustion process may be drawn from outside the cell and via additional filtering equipment. In the main, air is drawn from the cell environment, and this is the focus of this section.

The temperature of the air entering the inlet manifold has a direct influence on the complete integration of the air and fuel as a mixture, with regard to the evenness and atomization of the mixture (e.g. the dispersal and size of the fuel droplets throughout the air stream and on the mass of the air fuel mixture). When the air temperature is too low, fuel does not mix as effectively with the air stream due to the higher density of the air; therefore, it tends to fall to the sides and floor of the inlet tract. This gives an uneven mixture and poor atomization, which may cause misfiring and so forth. In turn, this can lead to higher emissions of hydrocarbons and carbon monoxide. In the case of air temperatures that are too high, the air charge is expanded by its heat and, as a consequence, has a reduced density. This reduced density means that the fuel lair charge will have a lesser mass than preferred (lower total oxygen content).

The efficient flow of air through and around the test cell is important for the safety and reliability of the testing operation. Although airflow rate and extraction through the cell usually are controlled automatically, the flow around the assemblies and equipment within the test cell is affected by the care and thought applied by the technician when setting up the test. It is important that cells are kept tidy and clear of unnecessary equipment, particularly near the ventilating fans and so forth.

Engine cooling system

The hot and cold wells provide a volume of water required for the running of numerous engine and dynamometer rigs under test at the same time. (Dynamometers are cooled by the water or air.) The wells provide the means for an infinitely variable and controllable engine heat range by controlling the flow and temperature of the raw water through the cell manifolds.

This system is designed to provide instant engine cooling for repeated cold-start condition testing by rapidly dissipating the heat of the engine coolant at the heat exchangers.

Water is lost through evaporation due to high temperatures in the system and through deliberate leaking. This deliberate leaking is done to ensure that the cooling water is recycled with fresh water over a period of time to prevent excess buildup of impurities and water quality deterioration. The bleed-off reduces the requirement to drain and replenish the system completely on a regular basis.

Fig.3.3 Water cooling towers

It must be emphasized here that the engine coolant (with or without antifreeze mixed into the coolant) is separate from the cooling raw water.

The engine coolant is stored in a host radiator chamber that also may incorporate the heat exchanger, with separate chambers keeping the engine coolant away from the cooling raw water. The components of the engine cooling system and their relative positions and connections are critical and must conform to the requirements laid down.

The cooling raw water carries away the engine coolant heat to the hot well and cooling towers. Frequently, a customer requests that his or her engine be run on a particular coolant and antifreeze mixture for certain tests.

This mixture is set up for the coolant system of the engine, and the cell raw water services are used to maintain running temperatures as required by the test procedures. Note that all antifreeze solutions are not the same.

Therefore, care should be used to ensure that technicians select the correct antifreeze, per the instructions of the engineer and client.

This is particularly important when ultra-low emission levels are being measured, for the heat transfer rate through the mixture can affect the combustion process. In addition, the onset of nucleate boiling and effective heat transfer can be adversely affected by incorrect coolant mixtures, making repeat tests at some time in the future practically impossible.

Fig.3.4 Heat exchanger

The main function of heat exchangers is, as the name suggests, to exchange heat. It is important to remember that heat can be exchanged in both directions using the heat exchanger system.

The new generation of plate heat exchangers has been designed as a low-cost alternative to the shell tube units.

High-pressure devices are made from grade 3-16 stainless steel heat transfer plates, two outer covers, and four connections, with copper vacuum brazed together to form an integral unit.

Low-pressure plate-type heat exchangers are manufactured from aluminum and duralumin.

These types of heat exchangers are suitable for heating, cooling, evaporating, or condensing any fluids compatible with the materials of construction.

Fuel supply and control system

Fuel is delivered in engine testing cell from two locations according to fuel type used. Commercial fuel is delivered from one of the master tanks with a capacity of 5000 liters; special fuel is delivered form barrels with a capacity of 200 liters.

Fuel is delivered by pneumatic pumps (with membrane), those pumps have the advantage that doesn’t use electric power to operate eliminating fire risk and if the pump is switch off, pressure remains in the system.

Because the fuel flow required to operate the engine is smaller the fuel flow produce by the pump it is necessary to use by-bass valves along fuel lines.

All the lines that enter in the engine room must have an electronic cut-off valve connected to fire extinguish system.

Fig.3.5 Tanks used for commercial fuel Fig.3.6 Special fuel barrels

A pressure regulator is used to obtain different pressures according to the engine tested.

Fig.3.7 Pressure regulator

For measuring fuel consumption and regulate fuel temperature it is used AVL system.

The combination of AVL Fuel Balance and AVL Fuel Temperature Control is a high precise fuel consumption measurement and conditioning system, which is used worldwide at almost all engine test beds where engines of a maximum consumption of 150 kg/h are tested.

The AVL Fuel Balance is mainly used where high measuring accuracies and gravimetric measurements are required.

The built in calibration device enables calibration of the system under real test bed conditions. The AVL Fuel Temperature Control is used for fuel temperature conditioning on engine and chassis dyno test beds in research, development and production.

As a controlled cooling system it allows the user to set the fuel temperature anywhere within the range of 10 … 80 °C.

This system is capable to condition fuel consumptions up to 150 kg/h with a typical temperature stability of better than 0.02 °C and thus guarantees highest measurement accuracy when determining the fuel consumption on modern combustion engines.

Reducing the fuel consumption of engines requires the measurement of increasingly small differences in fuel flow.

The AVL Fuel Balance allows measuring these slight differences with maximum reliability.

The AVL Fuel Balance with AVL Fuel Temperature Control is based on the principle of gravimetric measurement. The amount of fuel consumption is determined directly by measuring the time related weight decrease of the measuring vessel by means of a capacitive sensor. Convenient calibration and easy maintenance provide optimum ease of operation. With the FlexFuel option, up to 100% alcohol and biodiesel can be measured.

Fig.3.8 AVL fuel balance

The following measuring data and functions are available:

indication of the fuel consumption values in kg/h and g;

measurement and indication of the actual fuel consumption at a measurement frequency of 10 Hz (measurement time 0.1s);

average consumption for pre-selected measuring time or pre-selected measuring weight;

total/interval consumption for determined measuring time;

running average calculation with additional indication of standard deviation and min. /max. values (with option remote control);

fully automatic built-in accuracy check and calibration;

fast and efficient fuel change;

indication of error and status report.

Application The AVL Fuel Balance is used to measure the fuel consumption of engine- and chassis dyno test beds for transient and steady-state measurement.

Benefits

the precision measurement accuracy of 0.12% can be verified according to ISO9001 within a few minutes on the engine test by the integrated calibration unit;

test bed times are minimized due to extreme reliability and long maintenance intervals;

dynamic fuel consumption measurement on engines with air bubbles in the engine return line;

easy to integrate in different automation systems thanks to the presence of compatible interfaces;

measurement results absolutely comparable to the AVL Fuel Mass Flow Meter;

direct mass determination of the fuel;

eminently suitable for state-of-the-art high-pressure injection systems;

not sensitive to pressure pulsations from the carburetor system.

The fuel consumption is determined using an appropriate weighing vessel linked by a bending beam to a capacitive displacement sensor. Due to the fact that the weighting vessel has to be refilled for each measurement this is a discontinuous measurement principle. The mass of fuel consumed is therefore determined gravimetrically, which means that the density does not have to be determined in addition. The fuel consumption can thus be determined to an accuracy of 0.12%.

The built-in calibration unit is standard scope of supply and allows calibration and accuracy check according to ISO 9001 which helps to reduce downtimes.

Fig.3.9 AVL fuel balance operating principle

Tabel.3.1Tehnical Data

Engine charging equipment

William Froude is regarded as the father of the modern dynamometer. His first project was to design a dynamometer for the steam engine in the HMS Conquest. The unit was fitted to the propeller shaft of the HMS Conquest, and the unit was submerged to provide cooling capacity for the absorbed power. Handles located on the stern of the ship operated a complex series of bevel gears that opened and closed sluice gates. An arrangement of levers read the torque on a spring balance located on the quay; a mechanical mechanism noted the engine revolutions .These were coupled to a rotating drum, and this produced a speed-versus-load chart, the area under the graph being the power.

The dynamometer is as fundamental to the in-cell testing of engines as is the engine. In establishing the engine characteristics and performance under different “road load” conditions, it is necessary to be able to safely and effectively replicate actual on-road conditions on a consistent and repeatable basis. This is in essence what the dynamometer enables one to do when running engines are tested.

The function of the dynamometer is to impose variable loading conditions on the engine under test, across the range of engine speeds and durations, thereby enabling the accurate measurement of the torque and power output of the engine.

Many types of dynamometers are available to the industry, with each having its own distinct advantages and disadvantages compared to those of its rivals.

The main types of dynamometers considered here are as follows:

"Hydraulic" (or water brake), of which there are two types:

Constant fill: This type uses thin sluice plates inserted between the rotor and the stator, across the mouth of the pockets, to interrupt and affect the development of the toroidal (or whirlpool effect) flow patterns within the pockets. These sluice plates can be inserted to infinitely varying degrees to provide variable control of the loading of the engine crankshaft.

Variable fill: As the name suggests, this method relies on controlling the amount of water available within the dynamometer casing, thus affecting the water supply available to the rotor stator assembly. This in turn will have an effect on the developed resistance force. The use of water outlet valves in varying the water flow through the dynamometer casing replaces the sluice plate control found in the constant fill machines.

Electrical, of which there are three main types:

DC current

AC current

Eddy current

With the eddy current dynamometer, the engine turns on the driveshaft, which is mounted on the rotor within the dynamometer casing. The outer edges of the rotor disc run between electromagnetic poles of the stator. Varying the excitations of these magnets, thereby altering their effect on the spinning rotor disc, will develop a resistant force or drag to counter the torque of the engine. Electromagnetic devices such as this are infinitely variable and have the added advantage of almost instantaneous implementation, thus giving greater control for the test-bed controller. Water cooling is achieved by passing raw water into the cavities in the stator near the point where the rotor and the stator are closest (eg. where the magnets act upon the rotor plate).

Eddy current dynamometers are the most popular type used within the test cell environment. These vary in size and application, depending on the power-torque output of the engine being run. Special care must be given to the elimination of vibration when using electric dynamometers because the sensitivity of the control will be affected.

The AC or DC transient dynamometer consists of a variable speed generator or alternator, the electrical output of which is delivered outside the test cell to a controllable load bank. In certain cases, particularly where large power output and continuous operation are concerned, the output may be delivered into the mains supply.

The generator cooling air is drawn from the test cell and returned to it, contributing to the total heat release in the cell. No water cooling is likely to be involved. This type also can be used for starting the engine and is used primarily for transient testing. Here, the aim is to evaluate fuel consumption variances (among other values), during split-second operations such as gear changing and overrun situations, which also affect he1 use and so forth, via the engine management systems.

Fig.3.10.AC dynamometer

For our tests we use a AC dynamometer (Fig. 3.10) with the following specifications:

– power 227kW;

– maximum speed nn/nmax4130/8540 rpm

– power supply 380V;

– frequency fn/fmax 68/141 Hz.

This type of machine is characterized by a small inertia and is successfully use to simulate the whole vehicle run.

Because the stator is fixed, the engine torque is measured by an electromagnetic system without contact (flange torque sensor).

Equipments and softs used for data acquisition

3.2.1 Connecting box

All the sensors that we use to measure temperature and pressure are located in the connection box that does the link between sensors and network module (E-GATE01).

Fig.3.11.Connection box

The box has two modules:

– One module with 16 analog multifunctional inputs, can be configured for multiple signals;

– One module with 16 analog inputs configured for type K thermocouples.

Analog signal from sensors are converted into digital signals and transferred to E-GATE by a PROFIBUS-DP link up to 12Mbit/s.

Pressure sensors: is used PR 824 sensor with a precision of 0.25 % with different measure domain according to the engine parameter that is measured. The sensor can operate from -20 ˚C up to +90°C.

Fig.3.12 Pressure sensor and type K thermocouple

For temperature acquisition are use type K thermocouples with Ni Cr-Ni, precision is 1% of measurement field from -20 ˚C up to +1300°C.

The knock sensor contains a piezoelectric crystal (3) and a seismic mass (1).

When the detonation occurs, strong vibrations in the cylinder are produced that are propagated through the block motor and captured by the sensor. Vibrations transmit the seismic measurement of the skin to the piezoelectric element and produce an electrical voltage.

Fig.3.13.Knock sensor

Components of a knock sensor:

seismic mass;

the housing;

piezoelectric element;

electrodes;

electrical contacts.

3.2.2 Instrumented spark plugs

The pressure sensing instruments (fig.3.14) have the ability to measure the pressure in the cylinder according to the piezoelectric principle.

Fig.3.14.Spark plugs with pressure sensor

Since the electric charge produced by the crystal is low, it is transmitted through a high impedance cable and converted to a voltage signal by an amplifier (fig.3.15).

Fig.3.15. Signal amplifier AVL MICRO IFEM

After conversion, the signal is sent to the data acquisition system (fig.3.16)

Fig.3.16. Data acquisition system AVL INDIMODE

3.2.3 Encoder

To determine the position of the crankshaft and its angular speed, a transducer for the AVL 365C encoder crankshaft position is used.

The operating principle is based on the reflection phenomenon of light, having a slotted disc, which gives a very high accuracy under extreme operating conditions.

Electronic components are mounted separately from the sensor that is mounted on the crankshaft flange to minimize the influence of electrical interference, temperature and vibration.

The information is transmitted by light pulses from the encoder through a 2 meter long optical cable to an AVL INDIMODUL data acquisition unit that synchronizes the information received from the crankshaft position transducer with the engine cylinder pressure measured by the sensors piezoelectric spark plugs.

The encoder (figure 4) has the following features:

– Maximum speed: 20000 rpm;

– temperature range: from -400 to 700 ° C for electronic components;

– temperature range: from -400 to 1200 ° C for mechanical parts.

Fig.3.17. AVL 365Ce Crankshaft Position Transducer

Software used

DDT 2000.

It is a software that can perform diagnostics (feather reading and deletion) as well as uploading new calibrations into the ECU.

Fig.3.18.DDT 2000

INCA

In today's automotive industry, the standard is the INCA (Integrated Calibration and Acquisition system). The system allows a real-time calibration of hundreds of variables and tables while performing simultaneous recordings.

INCA tools are used to develop and test the ECU as well as validate and calibrate electronically controlled systems in the vehicle, on the test bench, or in a virtual environment on the PC.

The tools offer a wide variety of functions, including pre-calibration of functional models on the PC, programming Flash ECU, measurement data analysis, calibration data management, and automatic optimization of ECU parameters.

Generated data can be continually processed and evaluated.

Fig.3.19.INCA

INDICOM

IndiCom is a combustion analysis software that combines data acquisition with professional data evaluation for a clear graphical presentation.

AVL provides a complete solution for measuring combustion from sensors for data processing to post-processing solutions.

Benefits:

– a powerful and flexible data acquisition system for a wide variety of applications;

– extensive capabilities of on-line computing;

– easy integration into test cell automation with personalized and generic interfaces;

– maximum measurement accuracy.

Flexible data acquisition system that studies the combustion process for a wide range of engines. IndiLod AVL is the high-performance measuring device.

Fig.3.20.INDICOM

MORPHEE

It is a program used to control and monitor engine test stands.

As a result of this, Morphee performs the following real-time operations:

acquisition and storage of gross (unworked) or point-to-point measurements (ready processed);

continuous data acquisition for post-mortem examination – in the event of a failure in one of the stand equipment, all parameters of the stand can be examined the length of time before the fault occurred; the length of time can be set according to the size of the allocated memory;

control of all external instruments of the stand (both analogue and digital);

surveillance of all parameters, with different stop levels in case of repeating alarms or warnings.

Fig.3.21 Morphee