e-ISSN : 2541-1934
Review of Air Intake System Development for Internal Combustion Engine
Yulia Ayu N1, Nur Hidayatur R2, Risma Nurdinda3
1,2,3 Naval Architecture, Universitas Muhammadiyah Gresik, Jawa Timur Indonesia
*Koresponden email: [email protected]
Received: October 6, 2022 Accepted: October 17, 2022
Abstract
Today air intake system for internal combustion engines has experience changes to increase its performance.
In existence of an appropriate air supply will affect the air-fuel ratio (AFR) and impact on the power generated and decrease the value of NOx for more complex effects. The increasing demand for energy encourages the creation of new technologies that increase the value of work in the form of decreasing emissions, increasing efficiency to longer durability. The method used in this study is a comparison of the results of each starting air system. The air intake system functions as an air supply for the combustion process, the first air intake system utilizing atmospheric pressure to push air into the combustion chamber which today has developed with a turbo system. Turbo system has functions to increase the amount of air supply and compress it, so that the combustion process will be more efficient and produce more environmentally friendly exhaust gases and more optimal power, in other words better efficiency this is known as a turbocharger.
Keywords: intake air, combustion engine system development, internal combustion engine, air-fuel ratio, turbocharger
Abstrak
Saat ini sistem udara start untuk mesin pembakaran dalam telah mengalami perubahan untuk meningkatkan kinerjanya. Adanya suplai udara yang sesuai akan mempengaruhi air-fuel ratio (AFR) dan berdampak pada daya yang dihasilkan serta penurunan nilai NOx untuk efek yang lebih kompleks. Meningkatnya kebutuhan akan energi mendorong diciptakannya teknologi baru yang meningkatkan nilai kerja dalam bentuk menurunkan nilai emisi, meningkatkan efisiensi hingga daya tahan yang lebih lama. Metode yang digunakan dalam penelitian ini adalah komparasi hasil dari masing-masing sistem udara start. Sistem pemasukan udara berfungsi sebagai suplai udara untuk proses pembakaran, sistem pemasukan udara yang pertama memanfaatkan tekanan atmosfer untuk mendorong udara ke dalam ruang bakar yang dewasa ini telah berkembang dengan sistem turbo. Sistem turbo berfungsi untuk menambah jumlah suplai udara dan memampatkannya, sehingga proses pembakaran lebih sempurna sehingga menghasilkan gas buang yang lebih ramah lingkungan dan tenaga yang dihasilkan lebih optimal dengan kata lain efisiensi lebih baik.
Kata Kunci: sistem udara start, pengembangan sistem motor bakar, motor bakar dalam, rasio udara dan bahan bakar, turbocharger
1. Introduction
Air is a necessary component to create a combustion process. Therefore, air intake system includes as important role in the operation of combustion engine. The intake air system consists of several components, such as turbocharger, intercooler, sensors, valve, and intake manifold. Air intake systems are designed to be as effective as possible in order to provide fresh air intake to the combustion chamber with right amount and at appropriate temperature and pressure conditions for combustion and scavenging. The gas exchange phase when engine operates in expansion stroke, the residual gas combustion is removed from combustion chamber by opening exhaust valve and then open intake valve to enter fresh air into the combustion chamber [1].
The growing need for great power has led the development of an air intake system for combustion, which will support achievement of mixing air and fuel with right ratio. The compress air ratio is also defined as the ratio between volume of combustion chamber and displacement volume by piston. It impacts to development air intake system aimed at optimizing the combustion process by affecting the Air Fuel Ratio (AFR).
Today, air intake system has now been using an additional equipment called a turbo. Turbo on the air intake system is also called a supercharger or turbocharger, its function is to increase the mass of combustion air inside the cylinder by raising air density. Compressor is one of equipment that used to increase air density, supercharger and turbocharger differentiated by how the compressor works, if the compressor is driven by a crankshaft engine called a supercharger, if driven by a turbine is called a turbocharger.
To increase power or performance of a combustion engine, it requires two important roles of the main ingredients’ combustion, that is fuel and air. If viewed in terms of economy, air is basic ingredient to improve performance at a cheaper cost than fuel. As amount of air supplied increases, it will optimize combustion process and reduce unburning fuel discard to the air.
2. Functional Equipment of Air Intake System 2.1. Intake Manifold
Air intake manifold serves as air flow that ready to be inserted into combustion chamber or can be said as a guide to the air flow cylinder head. The general construction of the intake manifold consists of plenum then followed by a pipe leading to the valve. This manifold can show different in every machine, but its main function is to distribute the air into the cylinder evenly.
The construction should take into account some basic fluid mechanics so the flow can be evenly distributed to every channel and generate small losses. Like smooth surface and shape direct flow and produce pressure drop as small as possible from compressor to cylinder to air pressure is maintained. In addition, design must also consider heat insulation and provide a balanced flow direction to the entire cylinder.
The arrangement of fresh air supplement for combustion chamber is one aspect affecting exhaust emissions, fuel efficiency and engine performance. Some researchers have done research on changes in the shape of intake manifolds and even turbo systems aimed at improving engine performance. Most of the work done is to enlarge the plenum and change the inlet angle of the manifold so that it will generate turbulent airflow into the combustion chamber [2].
2.2. Air Filter
Keeping combustion chamber clean is not only a fuel filter task, but also an air filter equipment. These components will contribute to creating a clean combustion chamber and help optimize vehicle performance.
Beside consideration to note the diesel engine working on high enough compression ratio condition, of course this will cause cylinder liner scratched if the incoming air is dirty. Selection of air filter components should be adjusted from air consumption requirements for engine.
One of air filter function is preventing unwanted object to get in the engine and trigger some problems.
Air filter has flow restriction which is increase pressure ratio over the turbo which gives the same boost but to the cost of a higher working temperature. By using low restriction of intake air system will be gaining more power and less heat [3]. For air intake system scheme see figure 1.
Figure 1. Engine air flow diagram
Source : Seaboard Marine (www.sbmar.com accessed on May 11th, 2018)
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2.3. Turbocharger
In the air intake system circuit required the equipment that serves to maintain the quantity mass flow rate of air intake of the engine that serves as an air boosting tool and called Air Charger. Based on each of the different compressor drive types: Compressor which driven by exhaust engine was called gas turbocharger, and compressor that mechanically driven by the engine itself called supercharger and driven by a high-rotation electric motor called the electric supercharger. Each type of air charger has different technical specifications so that the selection is adjusted according to the operational needs of the engine.
To increase engine power and save fuel consumption and to utilize thermal energy contained in engine exhaust gases, the technology used is the Exhaust Gas Turbocharger (EGT) [4]. To maximize energy that contained in exhaust gases and still reduce the Turbo Lag occurrence, would be placed turbocharger which mounted by an electric turbo motor-generator series (Electric Turbo Compound / ETC). Some excess energy in the exhaust gas that contain energy of heat and gases flow will be converted by turbo to generator into electric power [5]. The engine-driven supercharger provides a stable continuous flow of time for each load change and eliminates the turbo lag effect because the rotation matches the fixed ratio of the engine rotation [6]. The application of an electric supercharger on the engine to eliminate turbo lag, offers fuel consumption savings and also inspires for downsizing of engines as well as reduced exhaust emissions [7]
2.4. Intercooler
Intercoolers have been increasingly used in internal combustion engines with supercharging since 1990s because of their positive effect on engine power and fuel consumption [8]. An intercooler is any mechanical device used to cool a fluid, including liquids or gases, between stages of a multi-stage heating process, typically a heat exchanger that removes waste heat in a gas compressor. The flow diagram can be seen on figure 2.
Figure 2. Turbocharger with intercooler System Source : [9]
The intercooler to be placed in the path of air that flows from the turbo/supercharger in to the motor.
An intercooler will be needed because the physics of air described in the Ideal Gas Law, that is PV= nRT.
Its explain the ideal gas law as basic because pressure and temperature are directly proportional, as it creates more pressure with turbo or supercharger, which produce more heat as well. Hot air is physically less dense and therefore contains fewer oxygen molecules per unit volume. This means less air for the motor in a given stroke and therefore less power produced. Hot air also causes a higher cylinder temperature and therefore can aid in pre-detonation of the combustion cycle causing detonation [10].
The Intercooler device works by increasing the efficiency of the induction system and reducing the heat generated by the supercharger or turbocharger it will increasing more through combustion. this removes the heat due to compression (i.e., temperature rise) that occurs in any gas when its pressure is increased or its unit mass per unit volume (density) is increased as shown in Figure 3. This is similar to a radiator whereas a radiator cools the engine but the turbo intercooler cools the air feed to the engine machine. When the turbocharged engine runs over long distances, more of the hot air compressed by the turbo enters the intercooler. Figure 3 will illustrate the intercooler temperature at a certain time will increase due to the entry of hot air, engine temperature and weather conditions [11].
Figure 3. Effect of the inter cooler temperature on pressure in the cylinder (P) versus crank angle (deg) Source : [12]
Intercoolers increase the efficiency of the induction system. This system work with reducing induction air heat created by the turbocharger and promoting more thorough combustion. This removes the heat of compression (i.e., the temperature rise) that occurs in any gas when its pressure is raised or its unit mass per unit volume (density) is increased. Intercoolers also work to eliminate the wasteful method of lowering intake charge temperature by the injection of excess fuel into the cylinders' air induction chambers, to cool the intake air charge, prior to its flowing into the cylinders. Turbocharger that work with intercooler will increase motor power (30 - 80%), diesel engine which using turbocharger can work more efficiently, if the machine has to work at an altitude of more than 1500 meters above sea level, turbocharger has an important meaning in the effort to overcome the loss power caused by the decrease in atmospheric air density the place.
The power generated will increase by 66.1% on an engine with the same number of cylinders and sizes using a turbocharger and intercooler at 2500 rpm. The average effective pressure increases by 66.4%
at 2300 rpm with the same engine dimensions and torque for this diesel motor also increases by 60.8% at 2100 rpm with the same engine speed. Meanwhile, specific fuel consumption decreased by 5.20% at 2100 rpm for combustion engines with turbochargers and intercoolers. Power indicator on combustion motor this diesel increased by 62.6%. With these results it can be concluded that the use of a turbocharger and an intercooler makes the engine work very efficiently and greatly affects the performance of the diesel motor.
[13].
2.5. Valve to Cylinder
Valve is one of important components in the working system of internal combustion engine. Valve to cylinder serves as air intake line into combustion chamber, and as a mixture intake line of air and fuel in the gasoline motor. In addition, valve also serves to remove the exhaust gas from the combustion chamber.
The intake valve construction will be larger than the exhaust valve this is intended for fresh air in the supply into the combustion chamber will be filled with good and produce the right turbulence [3].
Movement of intake and exhaust valve work mechanically and controlled by camshaft, while the camshaft is controlled by crankshaft. Control process occurs because crankshaft rotation and when the valve is open or closed it will provide movement corresponding to the movement of the piston [14]. When selecting a valve, it should take into account the thermal and mechanical pressures affecting the valve when in a closed position. And the valve must be able to work under extreme pressure without deformation or worn-out. It is also important to consider the process or speed of opening and closing the valve without damage.
2.6. Sensor
In addition to components that have been described above there are also sensors which needed by system during operational engine intake system in real applications. The sensors include:
a. Mass flow meters are placed between air and turbo filters to check incoming airflow.
b. Pressure gauges after air filter, to determine decreasing of air pressure which caused by the air filter.
c. The compressor's inlet temperature and temperature rise above the turbo are essential so a temperature meter needs to be installed in both positions.
d. Ambient temperature also needs to be known.
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e. Pressure gauge after turbo, to know how pressure generated by turbo.
f. Temperature and pressure are very important to be measured after going through intercooler because in this condition air will be ready to use for burning process [3].
3. Air Intake System Development 3.1. Naturally Aspirated Engine
Naturally aspirated engine is a system of intake oxygen into combustion chamber of an internal combustion engine that relies on atmospheric pressure and is not given forces induction such as turbochargers or superchargers. Such air supply systems are still frequently used in race or sport vehicles, this is intended to prevent turbo lag. The working principle of this system, air will be sucked by relying on the suction step, when the piston position moves downward to Bottom Dead Center. Due to the limited inlet space of the engine inlets through inlet manifold and air filter causing a decrease in suction pressure and resulting in less than 100%-cylinder air efficiency automatically decreases the power generated by the engine. Based on experiments conducted by researchers from Madras, the Indian Institute of Technology said that in the dynamics of different injection time between engine with turbocharger and naturally aspirated indicates that the naturally aspirated engine cannot handle the higher fuel mass during the combustion process [15].
Naturally aspirated engines show a very clear burning process phase, with increasing work load increasingly requiring more fuel and has a smaller phase delay. When compared to the engine with turbocharger, naturally aspirated has a smaller cylinder pressure than that there is less optimal combustion.
However, in high speed mode, the engine with a naturally aspirated system will produce a load that tends to be stable because the cylinder pressure does not decrease (relatively constant) [16]. Viewed based on combustion chamber construction, natural aspiration system is less suitable to be used on machines with burner construction using pre-chamber because swirl that produced is bad. And engine in this type also less sensitive to low-quality fuel [17].
3.2. Supercharger Development
Supercharger is required for the engine to be more efficient, more powerful and reduce air pollution from the exhaust generated. In compliance with air supplement that using supercharger, many application methods and supercharge types are used, so that the need for air mass flow will maintained continuity to the machine and can be fulfilled without being affected by the load changes from low to high load.
One form of the supercharger application method is the twin charger where the Supercharger is installed in the system after turbocharger in order to control the pressure. This supercharger function is to overcome the weaknesses that exist in the turbocharger about the slow response time. Architectures like this can work well even on low engine speeds. The disadvantage is the reduction of engine power used to drive the supercharger [18].
Associated with the next supercharger is a method of controlling the system of exhaust gas recirculation is reintroduced with pressurized fresh air from the supercharger into the combustion chamber.
At these two gas meetings, in fact the equalization of preceding pressure occurs from the gas mixing process, but is expected to result in rapid engine reaction, the formation of stable and smooth torque with exhaust gas recirculation (EGR) to a minimum. This method is intended to provide an additional heat for air intake and reduce exhaust engine [19].
This time about profitable situational design and manufacturing standards to gain great power and engine efficiency improvements, engine-driven supercharger twin screw is used because it has better low- speed torque characteristics and good transient response capability. Less support is the noise caused by the supercharger of twin screw caused by the over compressed of the compressor and the loss of the engine's effective power to drive the compressor. The work carried out is by extending the supercharger drain hole which enlarges the slot along the helical direction of the rotor to reduce compression and improve the discharge flow [20].
For small engines KR Pullen et al uses a supercharger driven by induced electric power with a compressor innovation called Turbo Claw which can anticipate when low engine speed, in the form of a radial working compressor that can work relatively very low against tangential velocity to eliminate instability. When low speed operation of course the needs air flow rate is also low, low-cost electric motor.
In its performance the compressor will be used only when necessary. Turbocharger and Supercharger / TurboClaw installed in parallel mode [21].
There are two categories of automotive superchargers, centrifugal superchargers and positive displacement superchargers. The centrifugal supercharger produces exponential pressure along with the
increase of rotation, but this type is not applicable for low rotation. The positive displacement supercharger (Root type) produces instant boost even at low speeds, but there is instability in the high-speed field of the supercharger automotive outlet, where the high-speed outflow varies in parallel plane but also perpendicular to the plane and forms a three-dimensional flow. Its size and angle are also varied and had a periodic behavior. The greatest instability of the nature of the airflow is at the closest to the outlet [22]
The Miller cycle is an engine cycle that working to determines the intake air valves are carried out by slowing or accelerating their closing, which aims to reduce exhaust emissions. The Miller cycle does not increase the efficiency of the engine, but it can improve clean work and reduce the tapping problem on the machine. The Miller cycle is more optimal when used with a supercharger. The network output of the Miller cycle is lower than the Otto cycle without the supercharger, (Mean Effective Pressure) MEP Miller cycle with lower supercharger than Otto cycle without supercharger. The air mass in a miller cycle cylinder with a supercharger is smaller than the Otto cycle without a supercharger. Optimization of the Miller cycle with the supercharger can be obtained by applying a higher-pressure supercharger and optimizing efficiency at the intake valve closure by Late Inlet valve closing (LIVC) method [23].
3.3. Turbocharger
A centrifugal compressor that gets power from turbines it called turbocharger whose power source comes from exhaust gas engine. It used in combustion engines to increase power and engine efficiency by increasing the air pressure entering the engine. Additional function of Turbocharger was motor that can reduce SFOC (Specific Fuel Oil Consumption), minimize vibration, and improve efficiency [24]. From the results of paper analysis, the results show about, machine performance is strongly influenced by turbocharger pressure and intercooler temperature. Intercooler has a key role in controlling the combustion temperature of cylinders in a turbocharged engine. Its main component is the turbocharged diesel internal combustion engine. Increased high-pressure air compressors can produce overheated air, significantly reducing performance improvements from turbo charging due to decreased density. With the intercooler the temperature received by the turbocharged enables greater air volume to be loaded into the engine. with the addition of turbocharger can increase motor power (30 - 80%), machine dies with turbochargers can work more efficiently, if the engine has to work more than 1500 meters above sea level, the turbocharger plays an important role in the effort to overcome the power losses caused by the reduced atmospheric air density at the site [13].
By using a turbocharger Power that produce will increase about 66.1% at 2500 rpm rotation with the same number of cylinders and engine dimensions. The average effect force increased by 66.4% at 2300 rpm rotation with the same engine dimension. The torque for this diesel fuel motor also increased by 60.8%
at 2100 rpm rotation with engine dimensions also equal. Specific fuel consumption decreased by 5.20% at 2100 rpm rotation for combustion engine with turbocharger and intercooler. The indicator power on this diesel fuel motor increased by 62.6%. With this result it can be said that the use of turbocharger and intercooler is very efficient and very influential on the performance of the diesel fuel motor.
Overfeeding is need for increasing power and torque compare with speed range. The problem of the overfeeding engine is to achieve the maximum output power, and in combination with maximum strength, improving the low-speed torque is reduced to postpone Turbo Lag. To reach this goal, careful planning and consideration of the turbine engine components are placed in harmony. We have to change some design parameters to turn a natural breathing machine into an overfeeding machine, Some parameters like engine and runner geometry are not changed and have to enter code and there is no optimization on any of these parameters. These changes need to be discussed. In general, the following points should be considered for the choice of a turbocharged engine [25]:
A) For different speeds increased its need to selected turbocharger engine torque for desired value.
B) The turbocharger size that will be chosen as small as possible. As turbocharger is smaller so its launching is faster, and increasing or decreasing its speed will be faster with high or low load, as a result the delay will be lower in the performance turbocharger (turbo lag). Inertia turbocharger is much smaller than it would be there and a further delay in performance will be resolved.
C) much less of a turbocharger to the combustion gases is used to increase the torque, the better. However, the turbine control valve (waste gate) will open more and more gases are discharged to the atmosphere.
Or in other words, as the combustion gases flow through the turbine is less, so turbocharger will have a higher response rate.
D) Engine Turbocharger must be carefully selected the compressor that would be use for and turbine will work with high efficiency and all functional parts and engine turbine and compressor are working in the area. These points do not reach to the surge line.
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4. Conclusion
Based on the description above, there are several things that can be concluded, including the development of air supply system technology for internal combustion engines that has brought good development to industrial needs. Such as increasing the power generated and reducing the NOx value generated by the engine. In addition, the development of air intake technology also makes today's commercial engines more fuel efficient than previous developments. Natural air supply system is not good in terms of fuel economy. However, under certain conditions, natural aspiration is needed because the modification process is easier and is generally used on small vehicles for racing needs.
5. Acknowledgment
The authors would like to thank for colleagues from the University of Muhammadiyah Gresik who have provided insights and insights that are very helpful for this research, although they may not agree with all the interpretations or conclusions of this paper.
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