Comparison of mechanical compressor and turbine
We are used to the fact that any internal combustion engine is subject to a simple principle: the larger the size of the motor, the higher its power. In principle it is predetermined by the laws of physics, but the engineering thought does not stand still in search of alternative ways to increase the thrust of power units not to the detriment of their size.
One of them can be called installation of an additional unit in the engine – a supercharger. Such a compressor can deliver a much larger volume of air into the cylinders than with the standard scheme. This means that it is possible to increase the fuel supply with the same volume of the combustion chamber.
Somewhat later, another device was developed – a turbine, which performs basically the same task, but in a slightly different way. Today we will talk about the differences between the turbine and the compressor.
Ways to increase the power of engines
Before considering the difference between a supercharger and a turbine and figuring out which technology is better, it makes sense to become familiar with the principles used to increase the power of modern powertrains.
The operating scheme of any internal combustion engine is quite simple: the driving force is fuel, or rather a mixture of air and fuel which burns in the cylinders, forcing them to perform a reciprocating motion. The two components are fed into the engine separately. The fuel (let’s take gasoline to be specific) is fed to the intake manifold through the fuel line, and its supply is provided by a separate pump. The air enters the engine by gravity, passing cleaning through the air filter. If it turns out to be clogged, the power of the power unit decreases, increasing the consumption.
But if you use devices that provide an unobstructed supply of increased volumes of air, and even under pressure, you can partially solve the problem of increasing engine power without the need to increase the volume of the combustion chamber. The amount of oxygen increases, which means that by a simple adjustment it is possible to increase the flow of gasoline, as a result the efficiency of the engine increases.
The compressor and turbine perform the task of forcing air into the cylinders, remaining to this day the most accessible and easy to implement devices to increase the intake capacity of the engine for the same dimensions. Of course, the increase in size is still there – at least due to the presence of the very additional devices, but in proportion it is not comparable with the need to increase the volume of the working cylinders, since it will lead to the need to change the size of the engine itself, including its body as the most massive component of the entire car.
Well, now let’s consider the peculiarities of operation of both types of devices.
How the turbine works
Most vehicles are equipped with four-stroke engines whose operation is controlled by an intake/exhaust valve system. Each work cycle of a modern power unit, as the name implies, includes four strokes, or episodes, as a result of which the engine crankshaft makes two complete revolutions.
Let’s consider these strokes in more detail:
- During intake, the pistons move downward, while simultaneously entering the combustion chamber of the FAM (in diesel engines, only air enters the CS);
- The compression cycle involves compression of the air-fuel mixture;
- During the expansion cycle, the compressed mixture is ignited by a spark generated at a certain moment by the spark plug (diesel units ignite spontaneously as a result of the injection of diesel fuel under higher pressure). As a result of combustion there is an explosive expansion of the mixture, which is converted into heat and exhaust gases;
- the exhaust stroke is characterized by the release of the exhaust with a simultaneous upward movement of the piston under the pressure of the exhaust gases.
Without going into details, we should note that such a scheme of motor operation implies the possibility of increasing its efficiency in the following ways:
- Increase in the volume of the CS and the entire engine;
- Increasing the crankshaft rpm;
- installation of a turbocharger.
The first method can be implemented in two independent ways: by increasing the size of the cylinders or by adding new cylinders. Both methods are applicable, but only at the expense of an increase in mass and dimensions of the power unit. In other words, this is a clearly expressed extensive type of development.
Growth of crankshaft RPM is possible by increasing the number of strokes of the piston, but this method also has severe limitations on applicability, caused by both technical features of implementation, and a drop in the overall efficiency of the motor due to the inevitable entrainment of losses, especially on the intake stroke.
The classical scheme of an internal combustion engine assumes the use of air entering the engine by gravity. The use of turbocharging allows the same volume of air to be fed into the cylinders, but in a compressed form, i.e. actually increasing the amount of oxygen in the combustion chamber. This means that more fuel can be supplied per unit of time, which allows increasing the efficiency of the power unit.
Structurally, this scheme is implemented as follows: the exhaust gases resulting from the combustion of fuel assemblies are directed to the rotor blades, rotating the turbine shaft. This drives the shaft of the compressor unit, which is actually responsible for supplying atmospheric air under pressure into the cylinders. On the way, the air, heated due to the effect of compression, is cooled by the intercooler, which prevents earlier ignition of the combustible mixture due to an increase in its temperature.
As you can see, the car’s crankshaft and turbocharger are not directly related, but in fact the speed of the crankshaft has an effect on the turbine’s performance. The fact is that at higher revolutions, the energy of the exhaust increases, which leads to an increase in turbocharger power.
Now let’s look at the difference between a mechanical compressor and a turbine.
How a compressor functions
When using methods to increase the power of the power unit by forcing more air volume into the cylinders, the first to be used were not turbochargers, but mechanical counterparts, or simply superchargers.
These units, unlike the turbine, use the crankshaft as the driving force, the rotation of which is transferred to the compressor shaft by means of a belt/chain gear, i.e. purely mechanically.
The supercharger principle is based on increasing the amount of air flowing into the combustion chamber, which allows the fuel-air mixture to be densified. The higher the density, the more powerful the fuel-air mixture will be ignited, transmitting more energy to the crankshaft and increasing the efficiency of the power unit.
It should be understood that there is an optimum proportion of the combustion mixture of fuel and air. For gasoline, it is 14:1, i.e. one part of the fuel must account for one volumetric part of the air. Thus, simply increasing the volume of air will not only not lead to an increase in the explosion power of the mixture, but will even worsen its parameters. This means that it is necessary to adjust the gasoline supply, which is done in cars, the engine of which is equipped with a mechanical compressor. And such adjustment is made in automatic mode, taking into account the work of the blower.
The power increase with this method is about 45%, and the value of torque increases by 30% on average. That’s pretty good, considering that it doesn’t require any intervention in the timing.
The mechanical supercharger is started as soon as the engine starts, when the drive belt wraps around the drive pinion on the crankshaft and connects it to the compressor gear. The blower rotor begins to draw air in, compresses it, and directs it under pressure into the intake manifold. The operating speed of the compressor is 50,000 to 60,000 rpm. This is enough to increase the amount of air flowing into the cylinders by 50%.
But there is one problem: when air is compressed, its temperature rises in proportion to its density, and this leads to the fact that when the mixture is ignited by the spark plug, it will not be able to give all its energy. So, along with increasing the amount of fuel to maintain the “golden” proportion, it is necessary to solve another problem: to cool the mixture. For this purpose, there is an intercooler as part of the mechanical compressor.
The cooling mechanism can be implemented in several ways: using coolant or by means of cold air running into the car.
So schematically, the difference between the compressor and turbine is minimal, but structurally, it is very significant.
Which is better: a compressor or a turbine
To assess the advantages and disadvantages of both approaches, let’s consider their features and differences:
- The main advantage of mechanical compressors is usually considered their ability to deliver a perfectly accurate amount of air, which, in turn, allows to obtain a balanced mixture. This reliability of the supercharger has the most positive effect on the work of the entire power unit, eliminating the probability of a number of malfunctions that lead to a reduction in the overall engine life;
- The advantage of the turbine is the absence of a mechanical drive, as it is powered by the kinetic energy of the exhaust. Thus, power losses are minimized here, unlike the compressor, which consumes up to 30% of the motor’s energy for its operation. But this is achieved by a substantial redesign of the gas distribution mechanism and a number of related assemblies. In addition, the greatest effect of the turbine is manifested when the power unit operates at maximum revolutions;
- From the above it follows and one of the main disadvantages of the turbine: its installation to the engine – the procedure is very complex, responsible and time consuming. The process of turbocharger adjustment is characterized by no less complexity. When installing it, not only do you have to install additional equipment, but also to modify the power unit itself, and in some cases – the transmission, because the load on the gearbox increases significantly;
- When using a mechanical compressor, the number of engine modifications is many times less, and most of them are of a superficial nature;
- installation of the supercharger into the engine compartment is in general easier than its turbocharged counterpart. The same can be said about the adjustment of a mechanical compressor, which consists in selecting the optimum parameters of the air-fuel mixture. Installation of the blower is greatly simplified by the use of ready-made kits specially designed for such a procedure;
- Turbine installation/tuning requires from the performer of the works a thorough knowledge of the theoretical part and numerous practical nuances. Therefore, the vast majority of motorists are unlikely to engage in this procedure on their own, and not every car service center will undertake such work. Installation of mechanical supercharger in this regard is almost by far easier;
- Another peculiarity of the turbine – high sensitivity to the quality of fuel and engine oil. Here, the problem of supplying lubricating fluid and draining it into the sump is solved autonomously, which complicates the design and increases operating costs (oil change in the turbine must be more frequent than in the engine). Ignoring this rule will inevitably lead to turbocharger malfunctions and a number of additional problems. The compressor in this context is much more tolerant of fuel quality;
- turbocharging is a complex technology, so the turbocharger requires special care. There is a considerable list of routine operations that are part of turbine and intercooler maintenance work. For the mechanical counterpart, the main problem is taking care of the cleanliness of the incoming air flow, and that is the case with screw-type and cam-type superchargers;
- The turbine does not work very well at low engine speeds, at times demonstrating the effect called “turbojam”. It is only when the crankshaft reaches medium rpm that you can feel the power increase, which becomes very tangible at maximum rpm. If the car is operated mainly in the city mode, the turbocharged engine can be ineffective. We should note that turbines of the latest generation are partially deprived of this disadvantage, confidently coping with the work of the motor at lower revolutions. But the cost of such devices is also high. The work of the compressor, as already noted, practically does not depend on the crankshaft speed, forming an effective boost in the whole power range. The power gain here will be about the same regardless of the revolutions of the power unit;
- The supercharger is a fairly self-contained unit, which is connected to the engine with a small number of interface parts, which simplifies its maintenance/repair. A turbocharged compressor is much more closely integrated into the engine, and its maintenance requires experience and knowledge uncharacteristic for such work on a conventional atmospheric power unit;
- The undoubted advantage of a turbine is that it provides a higher power boost. But turbine heat becomes a problem that is not so easy to solve. As a result, the wear and tear on the turbocharger itself increases dramatically, and engine parts fall into disrepair faster, reducing the overall life of the engine. So the cooling system has to be improved, which makes the design even more complex;
- The compressor starts working efficiently as soon as the crankshaft starts turning. That is, even at idle it will form a larger volume of FAM than that of the classic atmospheric engine. But you can’t say the same about the turbocharger – at low revs it won’t function at all. However, the supercharger takes a significant part of the power from the power unit (according to some calculations – up to 25-30%), so the power gain compared to the turbocharger is less by about the same amount;
- Another disadvantage of a mechanical supercharger is the higher fuel consumption compared to that of a turbine. Accordingly, the efficiency of the compressor is obviously lower. If we judge the usefulness of the supercharger in terms of fuel economy, the turbine is beyond competition;
- The mechanical drive of the compressor (chain or belt) is another headache for car owners, but compared to the maintenance of the turbine it can be called a trifle;
- If we talk about self-installation of the supercharger, the compressor version has many advantages. There are many models on the market with different characteristics, as well as ready-made kits. The choice of turbines is much narrower, and the situation will not change in the medium term;
- although the cost of a good turbocharger is much higher than that of a mechanical supercharger, and despite a number of its disadvantages, most cars are equipped with a turbine. The reason here is obvious – the maximum increase in engine power.
So, if you want to determine for yourself what is better, a turbine or a supercharger, let us summarize the above:
- The work of the compressor is more stable, it does not reduce the life of the engine;
- The efficiency of a turbine is significantly higher, as it uses the free energy of the exhaust and does not take power away from the power unit;
- The supercharger is much easier to install/maintain;
- a turbine requires its own lubrication system that requires maintenance (and more often than the engine’s lubrication system);
- engine power gain when using a turbocharger depends on the value of revolutions, with the compressor it is stable throughout the crankshaft speed range
- Maintenance of the turbine is many times more complicated;
- A mechanical compressor is less economical than a turbocharged blower
- Installation of a turbine requires significant modifications of the engine and its service systems. The supercharger, being a stand-alone device, is much easier to install;
- Selecting a compressor for any car model is an incomparably easier task than finding a suitable turbine;
- In terms of cost the compressor is also much more profitable.
As you can see, the turbocharged version of the supercharger has a lot more disadvantages, but most of them are offset by the main advantage for which such units were designed – a significant increase in power of the power unit.
So if you are so burning to make your car faster – you should consider all these factors before making a final decision. The more so that today the most actual solution is considered a double boost system, the device of which provides the joint use of both technologies. In particular, such cars are produced by automobile concern VAG.
A few words about the speed difference between the supercharger and the turbine
We have repeatedly mentioned the insensitivity of the mechanical supercharger to the current crankshaft RPM. In contrast to the compressor, the turbine at less than 3500 rpm will not work. To create pressure greater than atmospheric pressure, the crankshaft speed must be higher than the specified threshold.
When accelerating the car, the highest efficiency of the supercharger will be achieved for a short time, soon returning to the average indicators. With a turbine everything is different: at the beginning of acceleration you will feel the notorious “turbo slack”, but as you accelerate, the engine power will increase exponentially.
It follows that if you prefer to drive “with a breeze” in a car with a gasoline engine, the turbine will be the best option. For a diesel engine, there is no mechanical compressor at all.
Using a supercharger allows you to stabilize the engine in the entire range of modes, but the power gain will be much smaller.
Let’s leave aside the question of supercharger maintenance – the mechanical one has an indisputable advantage here, and concentrate on the economy and dynamics of the car. Here the preference is already on the side of the turbocharged variant. If we take into account that the present tendencies with fuel cost are not optimistic at all, it is not difficult to foresee that in a medium term buyers will prefer not voracious off-roaders, but economical mid-class cars. As for their unimpressive dynamics, the use of a turbine allows solving this problem completely. And to reduce thus fuel consumption. But the maintenance costs, most likely, will completely “eat up” such economy.
We hope that the description of the difference between a turbine and a compressor will help you to make the best decision depending on your goals and financial capabilities.
Turbine VS compressor…which side are you on?!
After surfing the vast expanse of the Internet, I’ve come to the following…:
A turbine is a rotary engine, the feature of which is continuous operation. The rotor converts the kinetic energy of steam, gas or water into mechanical energy. Today, turbines are actively used as the main drive element for a wide variety of vehicles (land, sea and air). As unbelievable as it may seem, an attempt to create a mechanism similar to the modern turbine was made even before our era. It was not until the late 19th century, with the development of thermodynamics and mechanical engineering, that steam turbines began to appear, distinguished primarily by their high functionality.
A compressor, in turn, can be different and used in a variety of industries. It is needed to compress and deliver gases (including air) under pressure. This device was invented to significantly increase the maximum power of the engine, because more air is pumped into the combustion chamber. As a result, more fuel enters the cylinder, which in turn means that the ultimate goal is achieved. To illustrate some figures: on average, a compressor can add about 46 percent more power (plus 31 percent more torque). Nowadays, these devices are actively used to increase the engine power of both cars and trucks. To date, compressors are the best and most economical option for those who want to increase the power of the engine, to add a certain amount of horsepower to it.
Comparison of turbine and compressor
What is the difference between a turbine and a compressor? When it comes to choosing a compressor or a turbine, one first looks at the main signs of difference that these devices have: -One of the main advantages of a compressor is to ensure the uninterrupted combustion of impurities. This directly affects the proper operation of the engine as a whole, helping to avoid various troubles associated with failure. -In turn, the turbine also has certain advantages: it does not affect the loss of horsepower, while the compressor cannot boast of this. True, it is necessary to notice that it is the general power output of the engine (loss at compression makes up to 20 percents). -Installation and tuning of the turbine is quite a complicated process, requiring considerable time and money. In addition, it is necessary to modify the powertrain somewhat. In comparison, in order to use a compressor, there is actually only one thing needed – the correct selection of the admixture. Installation is very easy. -If we talk about the turbine in the car, it will not be possible to install it without the help of a specialist. The compressor does not need special equipment and knowledge. This greatly simplifies the process. -Turbine in the car has a significant disadvantage – it requires a frequent supply of oil under pressure, which increases the cost of vehicle maintenance. If you do not perform this manipulation with a certain regularity, the car will quickly break down, creating additional problems. A compressor doesn’t need this. -The turbine requires special care. For it to work properly, the car owner will have to visit a workshop once a month if he or she does not have the necessary experience. -The turbine needs to be fully attached to the car’s engine. If the vehicle is producing a small amount of rpm, the turbine is almost useless. Only by squeezing the maximum revs can you get good power. Of course, a car owner can now buy a device that works regardless of the speed of the car, but such a turbine costs a decent amount. The work of the compressor does not depend on the speed of the car, it gives a fixed power at any speed. -The compressor is an independent device in the car, due to which the maintenance and repair process is simplified. Even without much experience, almost every car owner can repair the unit himself. -The turbine can reach higher rpm than the compressor. But it also heats up much faster, which puts the engine under attack. It will wear out quickly. -The compressor is actuated as soon as the engine is started. This is a definite advantage over the turbine, which will not work without transport movement. But at the same time, the compressor drives the entire engine. The turbine, on the other hand, relieves the “heart” of the car of the additional load. -Compressors consume more fuel than a turbine. And their efficiency is an order of magnitude lower. That is, the turbine in the car works at full power without wasting gasoline. -The compressor is belt-driven because it is a mechanical supercharger. The turbine is spun by the car’s exhaust gases, which spin two impellers connected by a shaft. -If you decide to buy a compressor for the car, you should know that there is a huge selection of them on the market. The turbine, on the other hand, has no such advantage. -Finally, the turbine costs an order of magnitude more than the compressor. This factor also causes the high popularity of the device in the Russian market.
And so, to summarize – the difference between a compressor and a turbine is as follows:
= The compressor ensures proper engine operation (uninterrupted combustion of the impurities). = The turbine does not affect the loss of horsepower (total power output of the powertrain). = In the degree of difficulty in installing and configuring the device. The compressor has the advantage in this regard. = The turbine requires an oil supply, which affects the entire operation of the car. = The turbine will have to be constantly maintained and diagnosed. = The turbine is installed directly into the engine, while the compressor is an independent device. = The compressor has a fixed capacity, while the turbine’s operation depends on the vehicle’s RPM. = The turbine is able to accelerate the car to higher speeds than the compressor. = A compressor uses more fuel with less efficiency than a turbine. = A compressor can be matched to any car model, while a turbine has few choices. = The cost of the turbine itself and its installation is higher than the price of the compressor.
My preference is for a compressor! What about you? I am interested in your opinion!
Peace, goodness, love, speed, DRIVE and smooth roads without cameras and “representatives of the law”! )))))