Browse Topic: Air supply
Air Supply Unit (ASU) serves as the pneumatic source for the air suspension system in the passenger car segment. The ASU is an electrically driven oil-free compressor with integrated air dryer to deliver dry air to the suspension system. Solenoid valve, Height Sensor and ECU adjusts the pressure in bellow based on the vehicle load condition. During the lab test, pressure was not building up in the compressor due to delivery valve failure. The type of valve in asu is reed valve type, it is mostly used in the micro compressors due to its low cost, simple structure and light weight configuration. The reed movement is based on the pressure difference between the inlet and the compression chamber. Failure analysis is carried out based on the finite element analysis to identify the root cause, the root cause identified is optimized to prevent the failure. An accelerated test condition is arrived based on the FEA and a tailored series of accelerated tests are carried out to reproduce the failure. The correlation between the test results and the FEA was found satisfactory. The significant factors that are responsible for the failure are identified with their respective control measures. This paper describes the reed valve failure simulation using finite element method and accelerated testing.
Proton exchange membrane fuel cells (PEMFC) are considered an environment-friendly alternative vehicle power in the future owing to their high power density and zero-carbon emission. To research the performance of the air supplied by the PEMFC air system, the PEMFC air system bench composed of an air compressor, cooler, emulated stack, back-pressure valve, and sensors was built. Then, a PEMFC system test bench composed of a hydrogen supply subsystem, stack, air supply subsystem, electronic control subsystem, and cooling subsystem was established. The fuel cell system control parameters and control method are complex due to the coupling and nonlinearity of the air supply system. The strategy composed of a feedforward table and piecewise proportional integral (PI) feedback control strategy was employed to regulate the pressure and flow rate of the air supply system. The air compressor map and the mapping relationship among the air compressor speed, opening of the back-pressure valve, and stack current were obtained by carrying out experiments on the PEMFC air system bench. The results show that the air pressure and flow rate follow the reference value, and the flow error and pressure error are 1.5 g/s and 0.25 kPa, respectively. The proposed strategy can coordinately control the air flow rate and pressure, and it can provide qualified pressure and flow rate for the PEMFC stack.
This SAE Aerospace Recommended Practice (ARP) applies to blankets used for passenger comfort within transport category aircraft cabins. When the term “blanket” is used in this document it refers to all blankets that are provided by the aircraft operator for passenger warmth.
The existing compressor plants at railroad marshalling yards (MYs) are equipped with automatic compressed air supply control systems. However, this is implemented using outdated and ineffective methods. Taking into account the current trends in the field of three-phase motor control, as well as the requirements for energy saving, the most effective is the frequency regulation of performance. The work provides a justification for the need to use a variable frequency drive of a compressor unit (CU). A mathematical model has been developed for controlling an asynchronous motor (AM), taking into account the setting coefficient of performance. As a result, a computer simulation model for controlling the drive motor of a reciprocating compressor at an MY has been proposed and tested. The diagrams and values obtained made it possible to study in detail the automatic control system of the drive and select the optimal control laws for the frequency-controlled unit. An analysis of the results of simulation modelling showed that at the moments of starting and stopping the machine, transient surges of currents, voltages, and mechanical shocks are eliminated, which will significantly extend the service life of electrical and mechanical components. And the control characteristic will reduce energy consumption due to the optimal control of the motor speed and, as a consequence, the unit performance. Thus this model and principle can be applied in real installations. As a result of this approach, an economic effect is expected due to optimal performance management and savings on maintenance and replacement of compressor station power units.
The article proves the necessity for heating the air in the pneumatic engine of a hybrid power unit designed for moving a compact wheeled vehicle. The aim is to improve the pneumatic engine operation indicators by heating the compressed air before it is supplied to the cylinder using the obtained theoretical and experimental studies. For the easy-to-use of assessing the effectiveness of heating the air supplied to a pneumatic engine, the experiments were carried out by two pressure ps = 0.7 MPa and ps = 0.9 MPa, according to them the testing of a pneumatic unit was conducted without heating the compressed air at the temperature equal to the ambient temperature Ts = 293 K. Also, during the experiments a pneumatic engine was tested at other temperatures while supplying the compressed air at the inlet to the engine cylinder. So, at an inlet pressure ps = 0.7 MPa, the compressed air was heated up to the temperature Ts = 383 K, and at a pressure ps = 0.9 MPa it was heated up to the temperature Ts = 388 K. The conclusions reached regarding the efficiency of heating the air at the inlet to the pneumatic power unit cylinders were drawn for the case when the pneumatic engine is used as part of a vehicle hybrid power unit and the air is heated by using the heat of exhaust gases from an internal combustion engine operating simultaneously or a heat accumulator. The studies carried out in this article make it possible to determine the feasibility of the joint use of a pneumatic power unit and an internal combustion engine, not only in severe operating conditions with heavy traffic on busy road sections of large cities and megalopolises, but also during the independent operation of a pneumatic engine in traffic jams..
This SAE Aerospace Information Report (AIR) provides information on aircraft cabin air quality, including: Origins of chemical airborne contaminants during routine operating and failure conditions. Exposure control measures, including design, maintenance, and worker training/education. This AIR does not deal with airflow requirements.
In Toyota’s 2nd generation FCV, an electric turbo-type air compressor has been adopted for downsizing and cost reduction. Automotive Fuel Cell applications present several challenges for implementing a turbo-type air compressor. When operating a fuel cell in high-temperature or high-altitude locations, the FC stack must be pressurized to prevent dry-up. The flow rate vs pressure conditions that the FC must pass through or in some cases operate at are typically within the surge region of a turbo-type air compressor. Additionally, Toyota requires quick air transient response (< 1 sec) for power generation, energy management, and FC dry-up prevention. If the turbo-type air compressor is not precisely controlled during quick transients, it can easily enter the surge region. To solve the above issues, we developed a new air supply controller which can avoid compressor surge by controlling 3 variables, ‘FC stack air flowrate’, ‘FC stack air pressure’, and ‘FC stack air Bypass’ independently with high accuracy. The controller was designed using a model-based development approach. At first, the physical characteristics of the air systems compressor, valves, pipes, and FC stack were modeled and integrated into a system level simulation that can run real-time on-board the vehicle Engine Control Unit (ECU). Next, the feedforward and feedback (PI) control were developed by implementing inverse models of the air system component equations. We confirmed that this control development approach could achieve Toyota’s air supply control performance requirements and prevent turbo-type air compressor surge.
Mechanical friction and heat transfer in internal combustion engines are two highly researched topics, due to their importance on the mechanical and thermal efficiencies of the engine. Despite the research efforts that were done throughout the years on both these subjects, engine modeling is still somewhat limited by the use of sub-models which do not fully represent the phenomena happening in the engine. Developing new models require experimental data which is accurate, repeatable and which covers wide range of operation. In SAE 2018-01-0121, the conventional pressurized motored method was investigated and compared with other friction determination methods. The pressurized motored method proved to offer a good intermediate between the conventional motored tests, which offer good repeatability, and the fired tests which provide the real operating conditions, but lacks repeatability and accuracy. A ‘shunt pipe’ was utilized between the intake and exhaust manifolds which reduced significantly the air supply demand. In SAE 2019-01-0930, Argon was used in place of air in the experimental setup which resulted in bulk gas temperatures synonymous to the fired engine. In SAE 2019-24-0141 and SAE 2020-01-1063 mixtures between air and Argon were utilized to investigate the relationship of mechanical friction with a controlled gradual increase in the bulk in-cylinder temperature. In this publication, a one-dimensional engine model is developed to assess the capability of the 1D model to capture the effects on the motored engine imposed by changing the working gas. From the experimental studies on the pressurized motored engine, increasing the proportion of Argon to air showed an increase in the peak bulk gas temperature of around 600°C. This resulted in an increase in the heat losses, a decrease in the pumping losses and no measureable difference in the mechanical friction.
Fuel cell technology can play a major role in reducing transportation-related emissions, especially in heavy-duty, long-haul applications. Consequent transfer of technology from air supply systems for combustion engines to cathode air paths serves as an enabler for necessary system cost reduction. To achieve the required system lifetime, the supply of clean air is essential. Gases like NOx, SO2 and NH3 poison the catalyst, leading to increased stack degradation rates. Effective removal with functionalized activated carbons enhances the catalyst´s lifetime. Research on real-life concentrations of these contaminants under different driving patterns and road profiles enables knowledge-based design of cathode air filter elements. To prevent flooding of components like air filter, humidifier, or stack, water separators are integrated at different position inside the system. Plastic air ducts with integrated sensors and flaps required to manage the air flow connect the different functional components. Broadband silencers are applied to reduce noises inside the system, e.g. generated by the compressor. Essential components like humidifier and air-cooler can easily be incorporated into the system. In the cathode air exhaust path, an additional water separator is applied to protect turbine blades and to prevent emission of splash water from the tailpipe. The consistent transfer of technology from air supply systems for combustion engines to cathode air paths enables cost-, noise and packaging-optimized, plausible system concepts with enhanced energy efficiency.
Continuous efforts to improve thermal efficiency and reduce exhaust emissions of internal combustion engines have resulted in development of various solutions towards improved lean burn ignition systems in spark ignition engines. The Dual Mode, Turbulent Jet Ignition (DM-TJI) system is one of the leading technologies in that regard which offers higher thermal efficiency and reduced NOx emissions due to its ability to operate with very lean or highly dilute mixtures. Compared to other pre-chamber ignition technologies, the DM-TJI system has the distinct capability to work with a very high level of EGR dilution (up to ~40%). Thus, this system enables the use of a three-way catalyst (TWC). Auxiliary air supply for pre-chamber purge allows this system to work with such high EGR dilution rate. This work presents the results of experimental investigation carried out with a Dual Mode, Turbulent Jet Ignition (DM-TJI) optical engine equipped with a cooled EGR system. The results show that the DM-TJI engine could maintain stable operation (COVIMEP<2%) with 40% external EGR at stoichiometric (λ ~ 1) operating conditions. The relative timing between the auxiliary air and fuel inside the pre-chamber was found to be critical to maintaining successful operation at 40% EGR diluted condition. Ultra-lean (up to λ ~ 2) operation was also demonstrated at two different compression ratios with good combustion stability. A range of pre-chamber nozzle orifice diameters were tested with both lean and EGR diluted conditions. In general, smaller orifice diameters resulted in shorter overall burn duration due to more favorable distribution in ignition sites.
The dynamic and efficiency of automotive fuel cell drives is significantly influenced by air supply system. Different air compression architectures use electric compressor (EC), electric turbocharger (ETC), or a serial booster (SB) consisting of turbocharger and electric compressor. These three variants of air compression systems were modeled using a map approach and added to a 0D fuel cell air supply model. The characteristic maps of the turbomachinery were measured on the test bench under fuel cell conditions. Subsequently, the calculated isentropic efficiencies were corrected with respect to heat transfer phenomena occurring during the measurement. Moreover, a scaling method for the maps of the turbomachinery is explained. The initial simulation of the air compression systems with equal diameters for the turbomachinery showed no difference in the mechanical power demand. Therefore, the particle swarm algorithm (PSA) was applied to optimize the turbomachinery maps of EC, ETC, and SB with the scaling method. The PSA reduces the mechanical power demand of EC by 17%, of ETC by 18%, and of SB by 27%. This leads to the lowest power consumption of SB followed by ETC and last EC. The best performance of SB is caused by the higher recuperated mechanical power of the turbine.
High pressure fuel cell engine, namely high pressure fuel cell system for automobiles, is the core power plant of fuel cell vehicle. Among many categories of fuel cells, proton exchange membrane fuel cell (PEMFC) is the most widely used one for automotive applications, with the characteristic of high power density, fast response and moderate working conditions. The cathode oxygen supply in PEMFC is one of the most important factors which affects its output power and operational lifespan. Reasonable regulation of air supply process flow and pressure can effectively improve system’s performance and efficiency. In this paper, a mathematical model of the air supply system and a model of altitude and environmental pressure are established in MATLAB \ Simulink by mechanism modeling method. Then the modules of the air supply system are integrated to supply air to the 85 KW PEMFC stack model. According to the nonlinear optimal theory, the optimal steady-state condition of the system under different net power is found. Simulate the air supply system under different altitude from 0 m to 4000 m. With analyzing the simulation results, it can be concluded that high-voltage fuel cell engine maximum output net power will be reduced by about 6% with each 1000 meters rise of altitude in the condition of the altitude below 3000 meters. From 3000 to 4000 meters, it will be reduced by 11%. At the same time for high-pressure fuel cell engine in high altitude environment, to ensure that it has the same net output power and the best efficiency as low altitude areas, the speed, the opening of back pressure valve and current must be increased as appropriate.
Several methods are nowadays used by OEM’s in order to determine engine friction through experiments to help them develop friction correlations to be used in 1D simulation models. Some of the friction measurement methods used are; Willans Line, Morse test, Teardown test and Indicated Method. Each of these methods have their own disadvantages, with some reliant on heavy assumptions. In this paper a friction measurement method is discussed which requires a conventional motoring dynamometer cell by which the engine can be motored at different speeds. The exhaust manifold of the motored 2 litre, 4 cylinder diesel engine was shorted to the intake manifold with an unrestrictive ‘shunt’ pipe which reroutes the exhausted air to the intake [1]. The shunt pipe was pressurized by an external source of compressed air to make up for blow-by losses. It is noted that the compressed air supply is thus a small fraction of what would be required if no recirculation is used. In fact a small compressor that supplied shop air to the laboratory was more than adequate. In this manner the engine could be loaded with peak in-cylinder pressures reaching those reached whilst firing, thus engine friction can be determined at any particular combination of engine speed and load. This method computes the rubbing friction mean effective pressure (RFMEP) from a subtraction of the brake mean effective pressure (BMEP) and indicated mean effective pressure (IMEP). Since in motoring both the IMEP and BMEP are comparable in magnitude to the FMEP, error propagation is kept to a minimum. Thermodynamic loss angle, cylinder to cylinder variability, cycle-to-cycle variability, setpoint stability and repeatability of measurements are presented for a 5 rpm by 4 MAP test matrix, 1100, 1400, 2000, 2500 and 3000 rpm and 1.0, 1.5, 2.0 and 2.5 bar MAP.
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