Turbochargers Information

HISTORY OF TURBOCHARGING

The development of turbochargers began around the same time as the first internal combustion engines were built. Between 1885 and 1896, Gottlieb Daimler and Rudolf Diesel conducted research into increasing power output and reducing fuel consumption by compressing air forced into the combustion chamber. In 1952, Swiss engineer Alfred Büchi successfully implemented exhaust gas-driven boosting for the first time, achieving a 40% power increase. This event marked the beginning of the gradual development and implementation of turbo technology.

The use of the first turbochargers was limited to extremely large engines, particularly marine engines. In the automotive sector, truck manufacturers were the first to start using turbochargers. In 1938, the first turbocharged engine for a truck was built at the "Swiss Machine Works Sauer" plant.

The first passenger cars equipped with turbos were the Chevrolet Corvair Monza and the Oldsmobile Jetfire, introduced to the American market in 1962-63. Despite the obvious technical advantages, low reliability led to the rapid disappearance of these models.

The 1973 oil crisis spurred research into the application of turbochargers on commercial diesel engines, as prior development of turbo technology had been hampered by the need for large capital investments and low fuel costs. The tightening of exhaust emission regulations in the late 80s led to a significant increase in the number of trucks equipped with turbochargers. Today, the level of turbo technology development is so high that almost every truck engine is equipped with a turbocharger.

The beginning of turbocharged engine use in sports cars, particularly in Formula 1 in the 70s, led to a significant increase in the popularity of turbochargers. The prefix "turbo" became fashionable. At that time, almost all car manufacturers offered at least one model with a gasoline turbocharged engine. However, after a few years, the trend for turbo engines began to fade, as it turned out that a turbocharger, while increasing the power of a gasoline engine, significantly increases fuel consumption.

Turbo lag was quite significant in the early models of this equipment, which was also a serious argument against installing a turbo on a gasoline engine.

A turning point in the development of turbochargers came with the release of the Mercedes-Benz 300 SD in 1978, the first passenger car equipped with a turbocharged diesel engine. In 1981, the VW Turbodiesel followed the Mercedes-Benz 300 SD. Using a turbocharger, manufacturers managed to increase the efficiency of the diesel engine to the level of a gasoline engine, while maintaining significantly lower exhaust emissions.

Today, installing a turbocharger on a gasoline engine is no longer considered from the perspective of increasing power, but from the perspective of reducing fuel consumption and thus reducing CO2 and other harmful emissions. Thus, turbocharged engines serve as a way to reduce energy consumption and environmental emissions.

MAIN CAUSES OF TURBOCHARGER FAILURE

As practice shows, the vast majority of turbo "failures" are caused by issues not related to the turbo itself. It is extremely important to determine the cause of failure BEFORE deciding to repair or replace the turbo.

4 MAIN CAUSES OF TURBOCHARGER FAILURE

1. Oil Contamination

• Contamination with fine particles. Not detectable visually, but causes bearing wear and grinding down of bearing edges.

2. Insufficient Lubrication

• Insufficient oil supply (e.g., due to blocked oil passages by gasket particles) is characterized by a strong discoloration of the bearing seats.
• Chemical contamination. Causes severe wear and overheating of bearings and the shaft. Visually, the damage is almost indistinguishable from damage due to insufficient lubrication. The main cause of this type of malfunction is fuel entering the oil, which degrades the latter's lubricating properties.

3. Extreme Operating Conditions

• Exceeding speed and/or power limits. Exceeding speed and/or power limits leads to overheating of the bearing seats, as well as oil coking. Carbon deposits form on the shaft. The back of the compressor wheel also becomes coked and deformed. In some cases, pieces can break off from the turbine wheel blades.

4. Damage from Foreign Object Ingestion

• Hard Foreign Object - Compressor. Damage occurs when a foreign object enters the compressor. An object entering the compressor ricochets off the compressor inlet walls, causing serious damage. Salt and sand cause severe erosion and destruction of the blades.
• Soft Foreign Object. Ingestion of soft foreign objects, such as pieces of paper or rags, into the turbo leads to blade deformation (bending backwards) and chipping of metal pieces from them.
• Hard Foreign Object - Turbine. A foreign object entering the turbine causes characteristic damage to the blades. Even small objects like rust flakes can cause serious destruction due to the high rotational speed of the impeller.

PRINCIPLE OF TURBOCHARGER OPERATION

To gain a clearer understanding of how a turbocharger works, it is necessary to familiarize oneself with the operating principle of an internal combustion engine. Today, most diesel passenger and commercial vehicles are equipped with 4-stroke piston engines, with operation controlled by intake and exhaust valves. Each working cycle consists of 4 strokes over 2 full crankshaft revolutions.

• Intake — as the piston moves down, air (in a diesel engine) or a fuel-air mixture (in a gasoline engine) passes through the open intake valve.
• Compression – the combustible mass is compressed.
• Expansion – the air-fuel mixture is ignited by spark plugs (gasoline engine), diesel fuel is injected under pressure and ignition occurs spontaneously.
• Exhaust – as the piston moves up, exhaust gases are expelled.

These operating principles provide the following ways to increase engine efficiency:

• Increasing displacement
• Increasing engine speed
• Turbocharging

INCREASING DISPLACEMENT

Increasing displacement provides an increase in engine power, as a larger combustion chamber allows for a greater volume of air to be forced in and more fuel to be burned. Increasing displacement can be achieved by increasing the number of cylinders or the volume of each cylinder. Generally, increasing displacement leads to an increase in engine mass. This method does not provide significant advantages in terms of emissions and fuel consumption.

INCREASING ENGINE SPEED

Another way to increase engine power is to increase engine speed. Increasing speed is done by increasing the number of piston strokes per unit of time. However, for technical reasons, this method has strict limitations. Increasing engine speed leads to increased pumping losses and other operational losses, causing a drop in efficiency.

TURBOCHARGING

When applying the first two methods, the engine relies solely on natural aspiration. Air for combustion flows directly into the cylinder during the intake stroke. When using a turbocharger, the air entering the combustion chamber is pre-compressed. The same volume of air enters the engine, but the higher pressure allows a greater mass of air to pass through, enabling an increase in the amount of fuel burned. Thus, when using a turbocharger, engine power increases relative to its displacement and fuel consumption.

CHARGE AIR COOLING

During compression, the intake air is heated to 180 °C. When cooled, the density of the air increases, allowing for a greater volume of air to be forced in. Charge air cooling is one of the few measures for increasing the power of internal combustion engines that positively impacts fuel consumption and emission levels. Reducing the temperature of the incoming air lowers the combustion temperature and, thus, reduces the amount of NOx produced. Increasing air density reduces fuel consumption and environmental pollution.

There are two types of turbocharging – mechanical supercharging and exhaust gas turbocharging.

MECHANICAL SUPERCHARGING

In mechanical supercharging, air is compressed by a compressor driven by the engine. However, part of the gained power is used to drive the compressor. Depending on the engine size, the power required to drive the compressor ranges from 10 to 15% of the total engine output. Thus, compared to a naturally aspirated engine of the same power, an engine with mechanical supercharging has higher fuel consumption.

EXHAUST GAS TURBOCHARGING

When using exhaust gas turbocharging, the energy of the exhaust gas, which is normally unused, is directed to drive a turbine. The compressor is on the same shaft as the turbine and provides intake, compression, and supply of air to the combustion chamber. In this case, there are no mechanical connections to the engine.

ADVANTAGES OF EXHAUST GAS TURBOCHARGING

• Compared to a naturally aspirated engine of the same power, a turbocharged engine has lower fuel consumption, as part of the exhaust gas energy contributes to increasing engine power. A smaller engine size reduces thermal and other losses.
• A turbocharged engine has a significantly better power-to-weight ratio, i.e., kW/kg.
• The required engine bay space for a turbocharged engine is smaller than for a naturally aspirated engine.
• With a turbocharged engine, it is possible to further improve torque characteristics to maintain power close to maximum at very low engine speeds, which avoids frequent gear shifting when driving in mountainous terrain.
• Turbocharged engines perform significantly better at high altitudes. Under reduced atmospheric pressure, a naturally aspirated engine loses a significant portion of its power. In contrast, the performance of a turbocharged engine improves due to the increased pressure difference between the constant pressure upstream of the turbine and the reduced external pressure at the turbine inlet. The low air density at the inlet is compensated for, resulting in almost zero power loss.
• Since a turbocharged engine is smaller and consequently has a smaller noise-radiating surface area, its noise characteristics are better than those of naturally aspirated engines.
• In this case, the turbocharger acts as an additional muffler.

TURBOCHARGER CONSTRUCTION

TURBINE HOUSING

The turbine housing is made from various grades of spheroidal graphite cast iron to withstand thermal impact and impeller destruction. Like the turbine wheel, the housing profile is machined to fully match the blade shape. The turbine housing inlet flange serves as the mounting base for securing the turbocharger, bearing the load.

Parameters:

• Typically an iron alloy with spheroidal graphite
• Usually serves as the mounting base, bearing the weight of the entire turbocharger

Main Requirements:

• Impact resistance
• Oxidation resistance
• Heat resistance (strength at high temperatures)
• Heat stability (resistance to thermal shock)
• Ease of machining for the turbine wheel

TURBINE WHEEL AND SHAFT ASSEMBLY

The turbine wheel is installed in the turbine housing and connected via a pin that rotates the compressor wheel.

Parameters:

• High-quality nickel alloy coating
• Made from strong and resistant alloys
• Withstands operating temperatures up to 760 °C

Main Requirements:

• Wear resistance
• Deformation resistance
• Corrosion resistance

COMPRESSOR HOUSING

The compressor housing is cast from aluminum. Various alloys are used for different compressor types. Both vacuum casting and sand casting are used. Precise final machining ensures the dimensions and surface quality necessary for normal turbo operation.

Parameters:

• Usually made from various aluminum alloys
• Precise dimensions and shapes
• Operating temperatures up to 200 °C

Main Requirements:

• Strength against impact and mechanical loads
• Machining quality and precise dimensions

COMPRESSOR WHEEL

The compressor wheel is made from aluminum alloys using casting. Rubber molds are used for casting. A casting mold is made from it, and molten metal is poured in. Precise blade dimensions and accurate machining are important for normal compressor operation. Boring and polishing increase fatigue resistance coefficients. The wheel is located on the shaft assembly.

Parameters:

• Typically aluminum alloy (Cu-Si)
• This casting process began use in 1976

Main Requirements:

• High fatigue strength
• High tensile strength
• High corrosion resistance
• On some wheel models, for very powerful and prolonged operation at high temperatures, the blades are made of titanium

BEARING HOUSING (CENTER HOUSING)

The gray metal bearing housing provides the location for the floating bearing system for the shaft, turbine, and compressor, which can rotate up to 170,000 revolutions per minute.

Parameters:

• Usually made of metal
• Manufacturing and processing involve grinding, boring, drilling, and polishing
• Complex geometric design for cooling

Main Requirements:

• Machining Quality
• Rigidity
• Heat Resistance

BEARING SYSTEM

The bearing system must withstand high temperatures, operating mode changes, the presence of dirt in the lubricant, etc.

The bearings are made from specially developed bronze or copper alloys. 

A specially developed manufacturing process is designed to create bearings with the necessary qualities of heat resistance and wear resistance.

The reinforced steel thrust rings and oil grooves are manufactured with particular precision. Axial pressure is absorbed by a bronze hydrodynamic thrust bearing located at the end of the shaft assembly. Precise calibration ensures even bearing load.