Page 10 - Winter 2018 Travelore Issue 44
P. 10

Page 10 - DRVC Travelore
continued from page 4
How They Work: Diesel Engines and Turbochargers
1 4
Oxygen density changes depending on air temperature and altitude. To address this, diesel manufacturers introduced the first turbochargers in the 1950s. Since then, improvements have been made in diesel functional- ity as well as with the turbochargers used on them.
A turbocharger is critical to the power output and effi- ciency of the diesel engine. It is the job of the turbo- charger to compress a great volume of air flowing
into the engine’s cylinder before the fuel is injected. When air is compressed the oxygen molecules are
packed closer together. The effect is that more fuel
can be added than for the same size, naturally-aspi-
rated engine. The result is the generation of increased mechanical power from the combustion process. There- fore, the same power can be produced from a smaller displacement engine with turbocharging than one that is normally aspirated (without turbocharging). This results in taking less space as well as a reduction in weight, in comparison to a non-turbocharged engine, while contrib- uting to improved fuel economy.
How a Turbocharger Works
A turbocharger is made up of two main sections: the turbine and the compressor (see the illustration on page 10). The turbine consists of the turbine wheel (1) and the turbine housing (2). It is the job of the turbine housing
to guide the exhaust gas (3) into the turbine wheel. The energy from the exhaust gas turns the turbine wheel, and the gas then exits the turbine housing through an exhaust outlet area (4).
The compressor also consists of two parts: the compressor wheel (5) and the compressor housing (6). The compres- sor’s mode of action is opposite that of the turbine. The compressor wheel is attached to the turbine by a forged steel shaft (7), and as the turbine turns the compressor wheel, the high-velocity spinning draws in air and com- presses it. The compressor housing then converts the high- velocity, low-pressure air stream into a high-pressure, low-velocity air stream through a process called diffusion. The compressed air (8) is pushed into the engine, allowing the engine to burn more fuel to produce more power.
A Word about Cummins
According to Cummins, they are the only manufacturer focuses on medium to heavy-duty diesel engine turbo
technologies. They provide fixed, wastegate, variable, two-stage, turbo-compounding and waste heat expander technologies specifically developed to deliver higher efficiency and lower cost while meeting strict emissions requirements.
Driving and Operating Tip
Always allow adequate cool-down time before shutting down a diesel engine. “Adequate time” will vary with conditions. In general, this means allowing the engine to operate at normal temperature (pay close attention to the temperature guage) for five minutes before shut down whether driving in light traffic on level road or idling at the destination. This helps all components to return to
a normal state of operation while maintaining adequate lubrication and will add longevity to the engine and it’s components. Idling longer than that timeframe at normal operating temperature is a waste of fuel and adds noth- ing to the operating life of a
modern engine.
Byron Songer, VP Publica- tions, served as compiler and general editor of this article. Core graphics were edited from material available from Cum- mins and “How Cars Work”.
1 The turbine wheel
2 The turbine housing
3 Exhaust gas
4 Exhaust outlet area
5 The compressor wheel
6 The compressor housing
7 Forged steel shaft
8 Compressed air

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