tailieunhanh - Ebook Engine testing - Theory and practice (3rd edition): Part 2

(BQ) Part 2 book "Engine testing - Theory and practice" has contents: Measurement of fuel, combustion air and oil consumption; thermal efficiency, measurement of heat and mechanical losses; thermal efficiency, measurement of heat and mechanical losses; exhaust emissions; tribology, fuel and lubrication testing,. and other contents. | 12 Measurement of fuel, combustion air and oil consumption Introduction In this chapter a review is made of the instruments required to measure the consumption of the liquid fuel, combustion air and lubricating oils during engine running in a test bed. Until the advent of instruments capable of measuring ‘instant’ air and fluid flow, the standard methods recorded cumulative consumption over a period of time, or measured the number of revolutions over which a known mass of liquid fuel was consumed. While these methods and instruments are still viable, more and more testers are required to record the actual transient consumption during test sequences that simulate ‘real-life’ driving conditions. Modern engine designs incorporate a number of fuel spill-back or fuel return strategies that make the design of test cell consumption systems more complex than before. In simple terms, it is necessary now to measure the amount of fuel entering the metering and conditioning system, rather than leaving it, for the engine. The systems frequently have to control the pressure of the fuel return line and remove vapour bubbles and the heat energy picked up through the engine’s fuel rail and pressure regulator circuit. Liquid fuel conditioning and consumption measurement is no longer a matter of choosing the appropriately sized instrument, but rather of designing a complex pipe circuit incorporating those instruments, heat exchangers and the engine. Measurement of the air consumption of the engine is covered in principle and practice. Measurement instruments for liquid fuel consumption For all liquid fuel consumption measurement, it is critical to control fuel temperature within the metered system as far as is possible. Therefore, most modern cells have a closely integrated temperature control and measurement system. The condition of the fuel returned from the engine can cause significant problems as it may return at pulsing pressure, considerably warmer than the control .