Testing of ic engines pdf

Introduction to Internal Combustion Engines 3. Air Standard Cycles 4. Fuel-Air and Actual Cycles 5. Combustion in S. Engines 6. Combustion in C. Engines 7. Air Capacity of Four Strok Engines 8. Two Stroke Engines 9. Chemical Thermodynamics and Fuels Conventional and Alternative Carburetion and Carburettors Fuel Injection Systems for C. Engines Ignition Systems S. Engine Friction and Lubrication Engine Cooling Supercharging of I. Testing and Performance of I.

Air Pollution from I. Engines and Its Control Miscellenous Engines Air Compressors Gas Turbines and Jet Propulsion Rajput Free? Visitor Kindly Note :. Disclaimer :. For any quarries, Disclaimer are requested to kindly contact us , We assured you we will do our best. Thank you.

Save my name, email, and website in this browser for the next time I comment. One way of avoiding part of the problem is to use a standard reference fuel, and to control its temperature at the point of measurement. This way, standard volumetric measuring techniques can be used without any complications. If normal commercial fuel is used, then density needs to be checked on every batch, and corrections for temperature applied. Laboratory engine tests traditionally use a well-established form of fuel flow gauge shown in Fig.

At first, steady state running is established with fuel coming from the high level tank, by gravity. Then the fuel tap T is turned off so that the fuel drawn by the engine comes from the measuring vessels, shown as the traditional globe pipettes, and is timed by a stop-watch. As soon as the measurement period is finished, the header tank is re-connected by opening the tap.

On one test the time for 50 cm3 of fuel to be consumed became surprisingly long, indicating incredibly low specific fuel consumption. It was not until the engine started misfiring towards the end of a measuring period that the answer was found. There was a partial blockage between the globe system and the engine.

The fuel supply was just adequate when running from the header tank. However, during measurement the head available to drive the fuel was lower, being just the head from the globes to the engine, hence the engine drew fuel not only from the globes but also an unmetered amount from the float chamber C, Fig.

After each measuring period the head from the tank was sufficient to refill the chamber. When the blockage was cleared the fuel consumption readings became credible.

This particular problem would not occur with a diesel or fuel injection gasoline engine, because in these cases there is no floatchamber or equivalent. Gravimetric fuel measuring devices have been developed, which automatically compensate for density variations in the fuel.

These are expensive but highly accurate. They also do not suffer from a problem with diesels, which is that the injector spillway flow, which must be returned to the measuring device, tends to contain air bubbles.

With a volumetric measuring device, the bubbles inevitably upset the measurement, whereas with a gravimetric device, they do not. Internal Combustion Engine Testing Fig. These measure mass flow rate directly, and are not affected by small bubbles, unless they accumulate to create a large air pocket. All continuous fuel flow rate measurement techniques are prone to errors, particularly at low flow rates, so where possible the measurements should be checked against a cumulative measurement.

There are various ways of measuring friction, all with disadvantages and inaccuracies. A motoring test, where the engine fuel andor ignition are cut off suddenly, and the engine is driven by the dynamometer, appears at first sight to be an accurate method.

If the readings are taken quickly, the engine is still at full operating temperature, so oil viscosity, etc. Unfortunately the cylinder pressures have reduced, so the piston ring friction is reduced.

Also, the gas flow changes, so the pumping losses in the engine change. This method is therefore not highly accurate. Morse tests are a variation on the same theme, where one or two cylinders are disabled at a time. Traditionally this was done by disconnecting one spark plug, but with fuel injection systems it is appropriate and safer to cut off the fuel to individual cylinders.

Morse tests are also not particularly accurate, the reasons being the same as for motoring tests. Willans line tests are based on the finding that for diesel engines, the fuel consumption versus load graph is very nearly linear over the lower part of the load spectrum.

Therefore extrapolating this line back to zero fuel consumption gives a theoretical indication of engine friction.

Unfortunately, this is friction at zero load, which is unrealistic for the same reasons as above. The friction could then be calculated from this and the brake torque. Systems for measuring the IMEP do exist, but have some limitations on accuracy, as described below. Measuring the position of top dead centre TDC to sufficient accuracy is quite difficult, partly due to torsional deflections in the crankshaft when running, which can amount to something of the order of 1".

A 1" error in angle may give a significant error in MEP. Cylinder pressures are best measured with piezo transducers. If directly exposed to the combustion chamber, they often suffer from transient thermal effects during combustion. The radiated heat pulse causes a transient bowing of the diaphragm on the front of the transducer, affecting the pressure readings.

This can be reduced but not eliminated by an insulating layer. If the transducer is recessed into a cavity, then resonance effects in the cavity may affect the readings.

One approach has been to incorporate the transducer into a spark plug washer or diesel injector washer , which presumably eliminates some of the above effects, but may make the reading sensitive to vibration and resonance effects.

Cylinder pressures often vary significantly between cylinders, so for a multi-cylinder engine it would be necessary to measure on all cylinders simultaneously. While engine friction measuring methods may not be strictly accurate, they are nevertheless very valuable experimental tools for developing improved engine designs.

The automotive industry requires complex tests, based on various driving cycles, with closely controlled conditions. Many of the worst engine emissions occur during transient conditions, which is why these requirements have evolved. Further details can be found in Plint and Martyr Temperatures of the internals of engines are measured routinely as part of engine development.

For static components, thermocouples are the standard technique, but for moving components, other techniques are used. A variety of plugs which melt at different temperatures are fitted, and the engine is run then dismantled to discover which have melted.

It is important to decrease the load and speed of the test progressively, as heat soakage can result in parts of the piston becoming unrealistically hot if the engine is suddenly stopped from full power. An arrangement has been described in Section 5. A small window is fitted in the cylinder wall and the infra- red detection instrument views through a stroboscopic disc. By varying the phasing between engine and stroboscope various parts of the piston can be observed.

Measurement of wear of piston rings has been carried out by irradiating a ring, then subsequently measuring the radioactivity of the engine oil. This technique could be applied to any component, and can be potentially used in the field as well as on the test-bed. Chemical doping rather than irradiation may be equally appropriate.