Engine Intake Research Articles

Microstructure and particle filtration behavior of multimodal filter media made of fibers of different shapes for automotive engine intake application

This article describes microstructure of needle-punched nonwoven filter media comprising polyester fibers of different cross-sectional shapes and reports on their dynamic particle filtration behavior both at clean and clogging stages. The multicomponent fibrous filter media were characterized by their mean fiber shapes which were related to those of the individual components weighted by the corresponding mass fractions. In such media, the fibers of different cross-sectional shapes produced a synergistic effect on the gravimetric filtration efficiency at the clean stage. The fractional filtration efficiency was quite accurately expressed as a sum of fractional filtration efficiencies of individual components weighted by their surface area fractions. The evolution of pressure drop was explained in light of drag theory, and the role of fiber shape in determining the drag coefficient was discussed. Overall, the multimodal fibrous filter media prepared with fibers of different cross-sectional shapes showed a high potential for automotive engine intake application.

A comparative assessment of performance, combustion, and emissions of a gasoline port and direct injection camless engine

AbstractThe lower part‐load efficiency of the spark‐ignition (SI) engine is because of the higher pumping loss during the gas exchange process. In this study, the part‐load efficiency of a port fuel injection (PFI) and gasoline direct injection (GDI) camless engines were investigated. An in‐house developed electro‐pneumatic variable valve actuation (VVA) system controls the camless engine's intake valve events. The effect of un‐throttled operation with early intake valve closings (EIVC) on performance, combustion, and emissions was analyzed. The IVC timing for GDI camless engine was found to be lower (2°–7° crank angle) than the PFI camless engine for all operating conditions due to the in‐cylinder charge cooling. Hence, the pumping mean effective pressure (PMEP) for GDI camless engine was reduced, and brake specific fuel consumption (BSFC) was improved (maximum 2.1%) compared to the PFI camless engine. The THC and CO emissions were higher for GDI camless engine due to the relatively in‐homogeneous mixture formation, whereas the NOx emission was lower for all operating conditions.

Microstructure and particle filtration behavior of multimodal fibrous filter media made of fibres of different sizes for engine intake air filtration

This paper reports a set of theoretical expressions for describing the microstructure of multimodal fibrous filter media comprising fibres of different cross-sectional sizes along with the application of such expressions to predict the filtration performance of clean and clogging media for engine intake air filtration. It is found that the overall filtration efficiency corresponds very well with the classical theory of air filtration after suitably modifying the single fibre efficiency and mean fibre diameter. The square of mean fibre diameter is found to be a weighted harmonic mean of the square of fibre diameter of individual component. The single fibre efficiency of multimodal filter media, when expressed as a summation of single fibre efficiencies of individual component of fibres weighted by the corresponding surface area fraction, correlates very well with the experimental results. The evolution of pressure drop is explained satisfactorily based on Berman’s approach after suitably modifying the Davies equation.

Structural optimization on the design of an automobile engine intake pipe

Structural optimization on the design of an automobile engine intake pipe

Hydraulic source ripple and source impedance in 3D acoustic FEM model

Pressure ripple, fluid-borne acoustic pressure wave, can be critical in hydraulic system design. Hydraulic pumps can be considered as an acoustic source causing pressure ripple. And thus, acoustic modeling approaches are appropriate to simulate pressure ripple in the system. Acoustic source characteristics include source strength and source impedance below the plane wave cutoff frequency. They can not only be used to analytical model straightforwardly, but also be applied in a 3D acoustic model with proper setup. This paper demonstrates how source characteristics of hydraulic pumps be applied in finite element models. The proposed method is validated by comparing to a 1-D analytical model, and then a case study demonstrates how the source characteristics can assist on pressure ripple design of the system. The method can also be translated to applications other than hydraulic systems, like engine intakes, exhaust systems, and HVAC systems.

Film Cooling in Gas Turbine and Nozzle.

A gas turbine is a rotating engine that generates its power through the flow of combustion gases. With either an axial or centrifugal compressor, air from the surrounding environment is drawn into the engine intake, where it is compressed and heated before being sent to combustion chamber. Every gas turbine engine has a nozzle as a standard part. Among its many responsibilities include propelling the engine forward, returning exhaust gases to the free stream, and regulating mass flow through the engine. When the power turbine's exhaust exits, the nozzle is directly in the direction of the fumes. Simply put, nozzles are just tubes that allow hot gases to flow through them; they're not much more complicated than that. The highest point on each of these deals is around 2500 kelvin. This research illustrates the film cooling method for gas turbine and nozzle longevity. For film cooling to work, the temperature of the airfoil and nozzle case must be decreased.

A Study of Engine Intake Noise Control Based on the Improved Filtered-x Least Mean Square Algorithm

To reduce the intake noise of automobile engines, an active control system model of engine intake noise is established with the Filtered-x least mean square (FxLMS) algorithm. The offline identification method is adopted to identify the secondary path. The engine speed signal is used to construct the reference signal of a sound source to avoid interference of a secondary sound source to the reference signal. A variable-step algorithm is proposed, in which parameters are added to the normalized algorithm instead of the sinusoidal variable-step algorithm to adjust the amplitude range. This algorithm not only has the advantages of fast convergence speed and small steady-state error but also adapts to the characteristics of a time-varying reference signal and easy selection of parameters. In this paper, the noise of automobile engines under the New European Driving Cycle (NEDC) is studied and the proposed algorithm has faster convergence speed compared with the normalization algorithm, better adaptability to the change of the reference signal, and better stability compared with the sinusoidal variable step-size algorithm. The results show that the algorithm proposed can effectively reduce the intake noise of the engine at each speed and the noise reduction effect can reach 23.11 dB at a certain frequency. Meanwhile, the stability of the system is improved.

An Experimental Study on a Dual-Fuel Generator Fueled With Diesel and Simulated Biogas

Abstract Diesel-fueled generators are widely used for power generation in remote and/or off-grid communities. In such communities, local organic waste streams can be used to generate biogas, which can be used to replace diesel used by diesel generators to lower fuel cost and reduce greenhouse gas (GHG) emissions. Diesel-powered generators can be easily retrofitted with a biogas dosing line in the engine intake to introduce biogas, but appropriate optimization would be of great help to further improve generator performance and reduce GHG emissions. The objective of this research is to demonstrate simplified optimization methods that can reduce GHG emissions (carbon dioxide and methane) from such retrofitted dual-fuel engines under various biogas compositions. The study was conducted on a modern 30 kilowatt (kW) generator using an electronically controlled, four-stroke, four-cylinder, direct injection, turbo-charged diesel engine. The engine was operated with the factory electronic control unit (ECU) and a programmable ECU which allowed for control of the fuel injections and exhaust gas recirculation valve. Biogas was simulated by using natural gas (with more than 95% methane by volume) which was diluted with either carbon dioxide or nitrogen. This study consisted of two areas. The first one was the comparison of the engine performance when operating with biogas using the factory ECU and the programmable ECU with user-optimized fuel injection. The second one was the influence of volume fraction of carbon dioxide or nitrogen in the biogas. Test results reinforced the importance of optimizing the diesel injections when the engine was operated in the biogas-diesel dual-fuel mode to ensure complete combustion and achieve a reduction in GHG emissions. Increasing nitrogen fraction had a minimal effect on the emissions but increasing carbon dioxide fraction caused the NOx and methane emissions to decrease, and the indicated thermal efficiency to increase.

Study on the influence of blade on electromagnetic scattering characteristics in the open-ended cavity

The aero engine intake is the most important and strongest scattering source of the combat aircraft in the forward area. The incident electromagnetic wave will directly illuminate the fan/compressor blades which would change the forward radar cross section (RCS) distribution of the intake. The influence of the internal blade geometry parameter, including blade number, blade stages and the angle between two-stage blades on the RCS of the open-ended cavity was obtained by using the method of moment with the multi-layer fast multipole. The results show that the mean RCS of the cavity decreases with the increasing blade number in the smaller detection angle range. The mean RCS of the cavity increases with the increasing blade stage which changes the transmission path of the incident electromagnetic wave inside the cavity. And compared with the cavity with only one blade, the mean RCS with three-stage blades increases by more than 55%. With the angle between the two-stage blades increasing, the mean RCS of the cavity decreases first and then increases.

Parametric modeling and optimization of the intake and exhaust phases of a hydrogen Wankel rotary engine using parallel computing optimization platform

Focusing on performance and emissions optimization, a novel parallel computing optimization platform was implemented to optimize the intake and exhaust phases of a hydrogen Wankel rotary engine (WRE). An improved multi-objective particle swarm algorithm implemented with the Sobol sequence was introduced in this study, which makes it superior in global search. A one-dimensional model integrating the leakage models was built and validated under various excess air ratios. The parametric control variables of the intake and exhaust phases were defined as rise stage, main stage, and decline stage. The indicated mean effective pressure (IMEP), indicated specific fuel consumption (ISFC), and nitrogen oxide (NOx) were used as evaluation objectives.The optimization results showed that there was a quadratic relationship between ISFC and IMEP, and the ISFC decreased with increasing IMEP. The relationship between NOx and IMEP was closer to linear, and the NOx increased with the increase of IMEP. The timing of intake port full closing (IPFC) contributed the most influence to IMEP and NOx, and a delayed IPFC resulted in a lower IMEP. The timing of exhaust port start opening (EPSO) significantly affected the ISFC, and an earlier EPSO resulted in a higher ISFC. In the optimal case, the IMEP was increased by 2.0%, ISFC was reduced by 1.1%, and NOx was only increased by 0.1%. It is a prospective approach to further improve performance and emissions simultaneously using parallel computing optimization platform.

Analysis of FSC Supercharged Engine Intake Front End

This paper is based on the simulation analysis of the supercharger front intake pipeline of the FSAE racing car engine. To limit engine power, the equation race requires an annular restrictor valve to be installed in the intake system with an inner diameter less than 20mm. Limiting valves have a great impact on the intake flow and engine performance. In this paper, the intake front segment is modeled, the simulation analysis is done by Fluent, and the GT-power engine simulation software is used to assist the simulation. A good intake front segment is obtained, which provides an effective method for the design of the intake front of supercharger engine.

A Study on Design of S-Duct Structures and Air Intake for Small Aircraft Applied to High Strength Carbon-Epoxy Composite Materials.

Recently, many structural parts using composite materials are being applied to small aircraft and UAV in the world. The aim of this work is to design the engine intake structure of a small aircraft. For structural safety evaluation, a finite element analysis method was applied. In this work, structural design and numerical analysis of air intake and s-duct structures for small aircraft were performed. The target structure is composed of an s-duct and a cylindrical intake structure. Firstly, an investigation of the mechanical properties of carbon/epoxy material was conducted. The distributed pressure load and acceleration condition was applied to the structural design. The structural design load was investigated considering safety factors. The structural analysis was performed to analyze the validity of the design results. Through the structural analysis using the finite element analysis method, it was confirmed that the designed air intake structure is safe. The manufacturing of the prototype structure will be carried out based on the designed result.

Physics-based modeling of homogeneous charge compression ignition engines with exhaust throttling

Homogeneous charge compression ignition (HCCI) engines create a more efficient power source for either stationary power generators or automotive applications. Due to the absence of direct actuation of ignition, HCCI based combustion control is quite challenging. For the purpose of control synthesis and design, a crank-angle based dynamic model of an HCCI engine with internal exhaust gas recirculation (EGR) is proposed in this paper. The HCCI autoignition timing is controlled by the amount of internal EGR induced by the cost effective exhaust throttling strategy. The zero dimensional single zone model is developed based on conservation of mass and energy and ideal gas law. The model is comprised of five subsystems: cylinder volume, intake, and exhaust runners along with combustion and heat-transfer models. Inputs to the model include engine speed, intake temperature, fueling rate, intake, and exhaust throttle positions. Outputs of the model contain the pressure, temperature, mass and burned gas fraction in the intake, exhaust and cylinder, air-to-fuel ratio (AFR), heat release rate, combustion phasing, and the indicated mean effective pressure (IMEP). The model is developed based on MATLAB/Simulink and validated against experimental data under steady-state and transient conditions at various intake temperatures, fueling levels, and exhaust throttle positions. Results demonstrate that by changing the exhaust throttle position, the pressure in the exhaust runner is regulated. As a result, the residual gas fraction is altered, leading to changes in mixture temperature and thus control of the HCCI combustion phasing. In the end, closed loop simulation is conducted with a linear quadratic Gaussian (LQG) controller applied to the crank-angle based model for regulation of combustion timing CA50 using exhaust throttle during load (fueling level) changes. In the future, this model can be utilized for control development and hardware in the loop (HIL) simulation.

Detailed analysis on engine operating in dual fuel mode with different energy fractions of sustainable HHO gas

AbstractCarbon emission and problems associated with the world have been the major concerns for the past few decades. The world governments have implemented stringent emission norms to reduce the pollution created by hydrocarbon combustion in automobiles. The use of gaseous fuels in IC engines has gained interest among the research community. In the present research work, hydrogen, and oxygen (HHO gas) are produced together in an electrolyzer unit and is fed into the engine intake manifold before the carburetor. The electrolyzer consists of an anode, cathode and five neutral plates made of 316 L SS. Electrolyser production rate was tested with four different molarity conditions of NaOH electrolyte solution ranging from 0.24 to 1 N. It was noted that a maximum of 2 LPM of HHO gas was produced with the supply of 90 A‐h current at 1 N solution concentration. The performance and emission characters of the SI engine were conducted at six different load conditions and four flow rates of HHO gas. HHO gas induction has significantly increased the thermal brake efficiency by 8% and decreased the specific fuel consumption by 20%. With the supply of 2 LPM of HHO gas, CO2, HC, and NOx emissions were reduced by 67%, 59%, and 34%, respectively.

Using a Genetic Algorithm to Achieve Optimal Matching between PMEP and Diameter of Intake and Exhaust Throat of a High-Boost-Ratio Engine

With the increasingly stringent CO2 emission regulations, the degree of strengthening of the engines is increasing. Under high-pressure conditions, the airway throat parts of the intake and exhaust systems have a great influence on the flow loss of the diesel engine. The reasonable distribution of the throat area of the intake and exhaust ports in the limited cylinder headspace is key to improving the performance of supercharged engines. This study took a large-bore, high-pressure ratio diesel engine as the research object. Firstly, the three-dimensional (3D) flow simulation method was used to reveal the influence law of different throat areas on the engine intake and exhaust flow under steady-state conditions, and a steady-flow test bench was built to verify the accuracy of the simulation model and law. Secondly, based on the 3D steady-state calculation and test results, a more accurate one-dimensional simulation model was constructed, and a joint optimization simulation platform was established based on the dynamic data link library. On this basis, the mathematical description of the multi-objective optimization of airway throat size was established using machine learning methods, such as a genetic algorithm, the design domain and boundary conditions of variable parameters were clarified, and the collaborative optimization objective of integrated flow coefficient and flow loss is proposed to achieve the fast and accurate optimization of intake and exhaust throat diameters.

Optimization of Marine Two-Stroke Diesel Engine Based on Air Intake Composition and Temperature Control

The influence of gas intake temperature, composition and the volume concentration of each gas component on diesel engine combustion, emission and the output power was studied by building a calculation model of the B&W 6S35ME-B9 marine two-stroke low-speed diesel engine, followed by a comprehensive optimization exploration. The results showed that under 295 K and 18.5% O2 of intake gas, the engine’s NOx emission is only 4.5 g/kWh and reduced to 58% from the normal air gas intake condition. Moreover, their power output is very similar. In addition, the effect of CO2 or H2O added into the intake of the diesel engine on the performance of the diesel engine can be compensated by reducing the intake temperature. At the intake temperature of 295 K, the engine’s NOx emission with 20.58% O2, 77.42% N2 and 2% H2O is 8.62 g/kWh, and 9.06 g/kWh under 20.79% O2, 78.21% N2 and 2% CO2. It is lower than 11.77 g/kWh, which is under normal intake conditions (315 K, 21%O2 and 79%N2). The power output is also similar to the normal intake condition. Therefore, the comprehensive optimization of gas intake temperature, composition and concentration can effectively optimize the diesel engine’s performance in terms of combustion, emission and power output. The research results have an important reference value for the optimization of diesel engine performance.

Analysis of pollutant emissions and fuel consumption, during real driving cycles in different intake temperature scenarios

Current European vehicle homologation regulations are increasingly restrictive. Recently, World-wide light-duty test cycle (WLTC) and Real driving emissions (RDE) cycles have been introduced as type approval tests for new vehicles. This document studies the effect of intake temperature on pollutant emissions and fuel consumption of a Euro 6 Diesel engine when tested under WLTC and RDE. The tests have been performed by setting the temperature at the outlet of the water charge air cooler (WCAC) at 35°C and 20°C in different tests. To do that, the air-cooler was immersed in a temperature-controlled water bath. This temperature reduction can be produced due to an improvement in the WCAC in the same ambient temperature or also with the same WCAC in case of the ambient temperature is lower. All tests have been carried out in an engine test bench, eliminating the uncertainty involved on the road (driving mode, traffic, ambient temperature, etc.). Once the WLTC and RDE cycles were performed, carbon dioxide (CO2) and pollutant results were analyzed. Nitrogen oxides (NOX) emissions were considerably reduced when the engine intake temperature air was decreased, concretely a 7.1% in RDE and 11.63% in WLTC and the CO2 emissions were also cut down around 1%.

An Experimental Study on Combustion and Cycle-by-Cycle Variations of an N-Butanol Engine with Hydrogen Direct Injection under Lean Burn Conditions.

This study experimentally investigated the effects of hydrogen direct injection on combustion and the cycle-by-cycle variations in a spark ignition n-butanol engine under lean burn conditions. For this purpose, a spark ignition engine installed with a hydrogen and n-butanol dual fuel injection system was specially developed. Experiments were conducted at four excess air ratios, four hydrogen fractions(φ(𝐻2)) and pure n-butanol. Engine speed and intake manifold absolute pressure (MAP) were kept at 1500 r/min and 43 kPa, respectively. The results indicate that the θ0–10 and θ10–90 decreased gradually with the increase in hydrogen fraction. Additionally, the indicated mean effective pressure (IMEP), the peak cylinder pressure (Pmax) and the maximum rate of pressure rise ((dP/dφ)max) increased gradually, while their cycle-by-cycle variations decreased with the increase in hydrogen fraction. In addition, the correlation between the (dP/dφ)max and its corresponding crank angle became weak with the increase in the excess air coefficient (λ), which tends to be strongly correlated with the increase in hydrogen fraction. The coefficient of variation of the Pmax and the IMEP increased with the increase in λ, while they decreased obviously after blending in the hydrogen under lean burn conditions. Furthermore, when λ was 1.0, a 5% hydrogen fraction improved the cycle-by-cycle variations most significantly. While a larger hydrogen fraction is needed to achieve the excellent combustion characteristics under lean burn conditions, hydrogen direct injection can promote combustion process and is beneficial for enhancing stable combustion and reducing the cycle-by-cycle variations.

Energy Saving in Trigeneration Plant for Food Industries

The trigeneration plants for combined cooling, heating, and electricity supply, or integrated energy systems (IES), are mostly based on gas reciprocating engines. The fuel efficiency of gas reciprocating engines depends essentially on air intake temperatures. The transformation of the heat removed from the combustion engines into refrigeration is generally conducted by absorption lithium-bromide chillers (ACh). The peculiarity of refrigeration generation in food technologies is the use of chilled water of about 12 °C instead of 7 °C as the most typical for ACh. This leads to a considerable cooling potential not realized by ACh that could be used for cooling the engine intake air. A refrigerant ejector chiller (ECh) is the simplest in design, cheap, and can be applied as the low-temperature stage of a two-stage absorption-ejector chiller (AECh) to provide engine intake air cooling and increase engine fuel efficiency as result. The monitoring data on gas engine fuel consumption and power were analyzed in order to evaluate the effect of gas engine cyclic air cooling.

Multi-objective surrogate model-based optimization of a small aircraft engine air-intake duct

Aviation industry is constantly striving for more efficient design processes in respect to optimal time, human and computational resources utilization. This implies a need for application of an approximation techniques enabling for fast responses generation with maintained level of results quality. This study focuses on an advancement of aerodynamic shape optimization process of a small aircraft engine intake system by introduction of a surrogate modelling step into the design loop. The multi-objective metamodel assisted optimization is carried out in order to reduce pressure losses along the engine intake duct and increase flow homogeneity at the engine compressor intake plane. Latin Hypercube Design method is utilized in order to sample the design space. A set of initial objective function evaluations is generated with application of Reynolds-averaged Navier–Stokes solver. The ensemble of samples is further used to train a Kriging-based surrogate model. The Efficient Global Optimization algorithm basing on the Expected Improvement function is employed to gradually increase the metamodel prediction quality by usage of sequential sampling technique. Finally, the optimal point predicted by the Kriging surrogate is validated against the high-fidelity model with usage of the Computational Fluid Dynamics code. The paper presents an application of the abovementioned methodology to the design process of the I-31T aircraft turboprop engine intake system. Proposed Kriging-based optimization workflow is utilized in order to reduce pressure losses and improve flow homogeneity in the engine air-intake duct.