Actual Engine Test Research Articles

Thermal performance of counterflow wet cooling tower filled with inclined folding wave packing: An experimental and numerical investigation

Improve the heat transfer performance of cooling tower packing in the field of energy saving and environmental protection is of great significance, this study proposes a kind of inclined folding wave packing, using experimental research and numerical calculations combined method to study the heat and mass transfer characteristics of inclined folding wave packing, the results show that: inlet wind speed rises, the cooling tower approximation reduced from 4.38 °C to 2.78 °C; when the gas to water mass ratio increases from 0.322 to 1.019, the cooling number from 1.115 to 1.754; when the gas to water mass ratio of 0.54, the height of the packing from 0.915 m to 1.830 m, the cooling number from 1.15 to 1.64, the height of the packing to enhance the channel of the gas-liquid heat transfer effect. Compared with the traditional ramp packing, the cooling efficiency of the developed inclined folded wave packing is improved by 15.32 %. Combined with the actual engineering test found that the packing height can be increased to reduce gas to water mass ratio and air volume requirements, up to 28 % of the air volume can be saved. The motor output power of 1.830 m high inclined folding wave packing in actual operation is 0.268 kW, compared with 0.915 m high inclined folding wave packing, the difference in energy consumption is 0.246 kW. Inclined folding wave packing can not only improve the overall performance of the cooling tower, but also significantly reduce energy consumption, which can guide the engineering practice.

Development of a Surrogate System of a Plant Dynamics Simulation Model and an Abnormal Situation Identification System for Nuclear Power Plants Using Deep Neural Networks

In the case of a new nuclear reactor, existing evaluation experience is limited; thus, accidents and troubles may occur as a result of such lack of experience. To deal with such situations, it is desirable to use a virtual nuclear plant to reproduce behaviors under various conditions and identify unknown anomalies from the behaviors. Then, when an abnormal situation occurs, one can quickly determine the cause of the abnormality to operate plant equipment and return the plant to a stable condition as quickly as possible. Two types of deep neural network (DNN) systems have been constructed to support the identification of unknown anomalies and the determination of their causes. One is a surrogate system that can estimate physical quantities of a nuclear power plant in a computational time of several orders less than a physical simulation model. The other is an abnormal situation identification system that can estimate the state of the disturbance causing an anomaly from physical quantities of a nuclear power plant. Both systems are trained and tested using data obtained from the analytical code for incore and plant dynamics (ACCORD), which reproduces the steady and dynamic behavior of the actual High Temperature Engineering Test Reactor (HTTR) under various scenarios. The DNN models are built by adjusting the main hyperparameters. Through these procedures, these systems are shown to be able to perform with a high degree of accuracy.

Design and Implementation of Three-Channel Drainage Pipeline Ground Penetrating Radar Device.

In order to solve the current problems that conventional video inspection can only detect, as an internal pipeline defect and drainage pipeline radar inspection device detects in a single direction and at radar frequency in water pipeline defect detection, a three-channel drainage pipeline ground penetrating radar (GPR) inspection device was designed and developed, the assembly and commissioning of the device prototype were completed, and an actual engineering test application was carried out. Focusing on the problem that the detection direction and depth of the single-channel detection device are limited, a three-channel drainage pipeline GPR inspection device is designed to realize the synchronous detection of the inside of the pipeline, the pipeline body, and the external environment of the pipeline, improving the detection depth and efficiency. According to the design scheme of the three-channel drainage pipeline GPR inspection device, the assembly of the device prototype was completed. The device contains three radar channels, the top of the main frequency of the antenna is 1.4 GHz, the two sides are 750 MHz, the video camera has a pixel count of 4 million, and the positioning accuracy is less than 1 mm, the waterproof grade is IP68, the detection accuracy of pipe deformation (slope) is 0.1°, the detection depth outside the pipe is 1.2 m, and the detection accuracy of corrosion thickness is 15 mm. In a practical application of the device, the Jianguomenqiao sewage pipeline in Beijing, China, was tested, resulting in the discovery of 87 defects, including 39 loose soil areas at the bottom of the pipe exterior, 40 void areas, and 8 cavities.

다양한 작동 조건에서의 마이크로 터보젯 엔진 성능 예측을 위한 통합 해석 모델 구현 연구

In this study, an integrated CFD analysis implementation were conducted for the commercial micro turbojet engine, JetCat P300-RX, which has a maximum thrust of 300 N. A three-dimensional integrated analysis model includes major components of the micro gas turbine engine. A steady-state RANS (Reynolds Averaged Navier-Stokes) analysis was performed using ANSYS CFX V20.2. For the turbulence model and combustion model, the k-ω SST (Shear Stress Transport) model and the EDM (Eddy Dissipation Model) model were applied, respectively. The analysis were performed for various engine speed (RPM) conditions from 30,000 RPM to 106,000 RPM and various altitude conditions from sea level to 3.0 km. And the analysis results were verified by comparing with the actual engine test results. The comparison results showed that most of the performance parameters, such as thrust, exhaust gas temperature (EGT), air flow rate, and compression ratio in all analysis conditions (RPM and altitude) are in good agreement with the ground test results of commercial engines.

The Non-Uniformity Control Strategy of a Marine High-Speed Diesel Engine Based on Each Cylinder’s Exhaust Temperature

To improve the non-uniformity of a multi-cylinder marine diesel engine caused by manufacturing assembly errors and performance degradation of the fuel injection system, with the instantaneous speed applied as the control target, the feedback variable of each cylinder’s exhaust temperature was used to obtain the non-uniformity information and the injection quantity of each cylinder was applied as the control variable; the inhomogeneity control was accomplished by modifying the injection pulse spectrum. The model of AVL Cruise M was established and validated by bench test data. The non-uniformity control strategy based on the instantaneous speed and the exhaust temperature of each cylinder was developed in SIMULINK, and the control effect was compared with the closed-loop control of cylinder pressure by software in-loop simulation. The results showed that the non-uniformity control strategy based on exhaust temperature could significantly improve the uniformity of each cylinder; although the improvement effect was not as great as the non-uniformity control strategy based on cylinder pressure, the cost was significantly reduced, and the practicality and reliability were better. With the closed-loop control of exhaust temperature and instantaneous speed, the CV (Coefficient of Variation) of IMEP (indicated effective pressure) was close to the closed-loop control of cylinder pressure; the maximum occurred at 25% load when it was 0.199%. This co-simulation provided a theoretical basis for the subsequent hardware-in-the-loop simulation and actual engine tests.

Operation characteristics of soil blasting vibration test device under vibration load

To improve the accuracy of vibration velocity monitoring during blasting in soil layers, this paper provides a method and device for data correction by combining finite element software and actual engineering test data. Based on the length of the test pedestal exposed to the surface of the geotechnical body, the finite element structural model corresponding to each length of the test pedestal is established. Moreover, a predetermined external excitation load is applied outside the finite element model and the correction function of the vibration data is obtained by analysis of the stress and vibration data. The device solves the problem of low accuracy of vibration velocity measurement in soil and establishes a correction method for measurement data. The results show the following: (1) With the propagation of blasting seismic waves, the maximum stress values of the test device appear in the footwall position, the middle of the extension rod, and the bottom position in that order. (2) At the end of the test, there is an obvious phenomenon of speed amplification at the top of the test device. (3) As the length of the test device exposed to the ground increases, the particle peak vibration velocity (PPV) of the test device varies exponentially with the PPV of the ground and the range of variation of the vibration velocity in the X-direction is the largest.

Dynamic Characteristics of LOX/Kerosene Variable Thrust Liquid Rocket Engine Test System Based on General Modular Simulation Method

For the research demand of reusable LOX/kerosene variable thrust liquid rocket engine, a test system with electric displacement pumps is designed and a multidisciplinary modular dynamic simulation method based on AMESim platform is used to analyze the system. The method comprehensively considers the characteristics of complex components in the engine and realizes the fast module assembly and variable step size solution. Considering the combustion model of thrust chamber, the positive displacement pump model with complex leakage channels, and the cooling jacket heat transfer model, the component dynamic equations are deduced and the final model simulation results reveal that the system has a smooth ignition, stage turning, and shutdown process. The thrust can reach 6900 N in high working condition and the variable thrust ratio is 5 : 1. The dynamic characteristics of the system show that the performance error of main pump components is less than 5%, the maximum average temperature rise of the thrust chamber coolant is about 28°C, and the time of stage adjustment is within 300 ms, which mean the overall design of the system is reasonable. Although the accumulation of LOX before kerosene injection can adversely affect the temperature of the thrust chamber, large pressure pulses do not occur due to the ignitor’s duty flame. Moreover, the pintle injectors based on PID control can effectively stabilize the pressure drop at lower conditions. The system and the simulation method provide important support for the actual engine test and the general LRE dynamic characteristics analysis.

Water injection control modelling by using model-based calibration

<p><span lang="EN-US">This study presents the development of water injection system for turbocharged spark ignition engine. The water injection control system is built for turbocharged spark ignition (SI) engine where water was injected at the intake port just before the throttle body. The data was collected from the simulation through the GT-Power software to determine the optimized injection output for the engine. Single-stage statistical engine responses and boundary models were established by using Model-Based Calibration Toolbox. Control system was built using Simulink and simulation tests were conducted based on the speed and throttle position as the variables. The highest value of brake torque achieved in the GT-Power simulation was taken as the base value to determine the injection amount. The mean value of the predicted injection was recorded at 12.29 g/s while the variance of the predicted injection to the optimized injection was below 1%. The control system was simulated with the set predicted injection and the standard deviation of the predicted injection was 1.18. The control system simulation recorded a low percentage of 0.04% variance to the optimized injection with the pulse width modulation signal. The control system is ideal to be constructed and tested on actual engine test bed.</span></p>

Real Driving Emissions Evaluation for A Heavy Duty Diesel Vehicle based on Engine-in-the-loop Methodology

Real driving emissions of a heavy-duty vehicle with a maximum total mass of 18000 kg were investigated by the engine-in-the-loop (EIL) methodology. Virtual vehicle model, driver model and real road model was established, then to combined with the actual engine and emission test equipment to fulfill the vehicle emission evaluation on engine test bed. The results indicate the road driving can be well reproduced on engine laboratory with good vehicle speed followability, engine speed and torque consistence. However, the emission results show a larger difference with a 3.6 gap for CO2, a 72.3% gap for NOx and a 40% gap for PN., respectively. Analysis shows that the intercooler temperature, the exhaust temperature and equipment difference has a combined effect on the emission accuracy.

Effects of textured cylinder liner piston ring on performances of diesel engine under hot engine tests

It has great significance on the performance of cylinder liner-piston ring (CLPR) friction pairs with the different surface textures and affects the service life, reliability, and economy of diesel engines. However, most studies on the surface texture applied to CLPR have concentrated on simulated tests and computations, and the actual hot engine tests were ignored. The aim of this study was to gain insights into the interactions between different types of surface textures and the performance of diesel CLPRs under hot engine conditions. Three types of thread groove textures on cylinder liner surfaces with different widths, including 1, 2, and 3 mm, and a circular dimple texture on a piston ring with a depth of 100 μm were designed and machined, and were then tested under hot test conditions using a four-stroke diesel engine. To investigate the performance of diesel engine using different types of surface textures, the wear mass loss of the piston ring, worn surface morphologies and wear depth of the cylinder liner, exhaust gas emissions performance, and vibration performance of the diesel engine were obtained. Compared with untextured CLPRs, the experimental results indicated that appropriate surface texture (e.g., 3 mm wide grooved texture) significantly affected the comprehensive performance of the diesel engine. These findings will aid in understanding the performance impact of surface texture on diesel under hot engine conditions as well as its actual application to diesel engines.

A Study of Wear Mechanism on Upper Surface of Piston Top Ring Groove

<div class="section abstract"><div class="htmlview paragraph">During engine durability tests (peak power, constant engine speed) conducted in the development process, it has been the case that excessive wear has occurred to the upper surfaces of the piston top ring grooves, despite the fact that contact pressure due to combustion pressure has been low. This has resulted in considerable increases in development man-hours. The research discussed in this paper therefore set out to conduct a factor analysis of wear on the upper surfaces of piston top ring grooves in order to elucidate the wear mechanism in petrol engine for passenger car. This paper will discuss the test method employed in the factor analysis and the mechanism of wear demonstrated by the analysis. First, the form of the wear was analyzed, and rig test methods able to reproduce wear were developed. With regard to the form of wear, both sliding and impact modes were observed. Sensitivity analyses for each form of wear were conducted using rig tests. Quality engineering was employed in the tests, and sensitivity was analyzed based on the design of experimental method. Following this, an engine motoring test method was developed that was closer to the operating state of an actual engine, and that allowed tests to be simply conducted. This motoring test was able to reproduce a compound form of wear produced by sliding and impact, equivalent to that observed in an actual engine, and verified the accuracy of the factor sensitivity demonstrated in the rig tests. In addition, the motoring test was able to reproduce asymmetrical wear in the direction of the circumference of the grooves, which could not be reproduced in the rig test, and made it possible to elucidate the causes of this wear. Finally, an actual engine test was conducted combining the highest and lowest of the determined sensitivities, confirming the validity of the identified wear factors.</div></div>

Characteristics of Integrated Air Control and Low-Pressure Exhaust Gas Recirculation Valve for Diesel Engines

The purpose of this study is to investigate the characteristics of a newly introduced integrated exhaust gas recirculation (EGR) valve. Traditionally, a exhaust-pressure regulating valve is installed to increase the EGR flow rate; the method used in this study induces an increase of the EGR flow by restricting fresh intake. Unlike the two-motor two-drive system of the low-pressure (LP)-EGR system, the air control valve (ACV) and EGR valve are constructed in a linked structure. The two valves can be controlled simultaneously by a single driver, which permits reductions in volume and weight. In order to compare the existing LP-EGR system with the integrated LP-EGR system, the characteristics of the system were analyzed by a rig test and an actual engine test. It was determined that as the EGR valve opened, the EGR rate was increased and the torque was decreased under the same load condition because of the pumping resistance caused by the ACV closing.

Characterization of the friction and wear effects of graphene nanoparticles in oil on the ring/cylinder liner of internal combustion engine

Purpose This study aims to investigate the tribological characteristics of a Napier-type second piston ring against a cylinder liner in the presence of graphene nano-additives mixed into 5W40 fully synthetic engine oil. Design/methodology/approach Wear tests were carried out in the boundary lubrication condition using a reciprocating tribometer, and real engine tests were performed using a single spark ignition Honda GX 270 test engine for a duration of 75 h. Findings The experimental results of the tribometer tests revealed that the nano-additives formed a layer on the rubbed surfaces of both the piston ring and the cylinder liner. However, this layer was only formed at the top dead center of the cylinder liner during the engine tests. The accumulation of carbon (C) from the graphene was heavily detected on the rubbed surface of piston ring/cylinder liner, mixed with other additive elements such as Ca, Zn, S and P. Overall, the use of graphene nano-additives in engine oil was found to improve the frictional behavior in the boundary and mixed lubrication regimes. Abrasive wear was found to be the main mechanism occurring on the surface of both piston rings and cylinder liners. Originality/value Though many researchers have discussed the potential benefits of graphene as a nano-additive in oil to reduce the friction and wear in laboratory tests using tribometers, to date, no actual engine tests have been performed. In this paper, both tribometer and real engine tests were performed on a piston ring and cylinder liner using a fully formulated oil with and without graphene nano-additives in the boundary lubrication condition. It was found that a graphene nano-additive plays an active role in lowering the coefficient of friction and increasing surface protection and lubrication by forming a protective layer on the rubbing surfaces.

An experimental study on the application of oxygenated fuel to diesel engines

This paper deals with the evaporative characteristics and engine test results of emulsified fuels composed of diesel and hydrogen peroxide to reduce engine emissions by means of fuel design. The purpose of this study is basic research for applying emulsified fuel (EF) to engine through investigating the change of properties of emulsified fuel and the analysis of the behavior characteristics of free and impinging spray. In addition, the results are applied to real engine and the results of the study are presented comprehensively. To make the emulsified fuel for the experiment, the surfactant for mixing the emulsified fuel was fixed at a mixing ratio of 3% (vol.) of the total volume of the fuel, and Span 80 and Tween 80 were mixed at a ratio of 9:1. The mixing ratio of the hydrogen peroxide of the emulsified fuels was set to increase by 10% from EF2 to EF42 in consideration of the amount of the surfactant, and expressed as EF0 (diesel) in the case of diesel only. However, for the stable operation of the engine, the actual engine experiment was conducted only for the mixing ratios of EF0 and EF2. In order to analyze the characteristics of evaporation and engine emission reduction according to the mixing ratio of emulsified fuel, the experiments of droplet, free spray, impinging spray and actual engine were performed, respectively. Experimental images for visualization were obtained by using scattered light and Schlieren method. In the case of the droplet experiment, the evaporation characteristics were analyzed by free drop of the fuel droplet on a heating plate maintained at 473 K. The injection pressures of the emulsified fuel were set to 40 MPa, 60 MPa, 80 MPa and 100 MPa. In the case of free spray, experiment was carried out in a constant volume chamber maintained at room temperature (288 K) and 423 K. In the case of the impinging spray, the temperature of the impinged plate was changed to 423 K, 473 K and 523 K, respectively. The evaporation characteristics of the emulsified fuel were analyzed through the analysis of the fuel diffusion area and the entropy analysis based on statistical thermodynamics using the results obtained from such experiments. It was found that droplet and spray evaporation were promoted as the mixing of hydrogen peroxide in the emulsified fuel increased, and a method of quantitatively analyzing the experimental phenomenon could be proposed. From these results, it can be expected that the mixture of emulsified fuel mixed with hydrogen peroxide can be formed faster than the conventional diesel when applied to a real diesel engine. As a result, it is expected to play a positive role in terms of engine emission reduction. Based on these basic experimental results, emulsified fuels with mixing ratios of EF0 and EF2 were applied to diesel engine and actual engine test was conducted. NOx and soot were reduced by rapid mixture formation due to the fuel evaporation promoting effect as well as the effect of lowering the temperature of the combustion chamber due to the latent heat of evaporation of the hydrogen peroxide contained in the emulsified fuel. Finally, it can be confirmed that when the proper mixture ratio of emulsified fuel is selected for main engine operation, simultaneous reduction of NOx and soot is possible.

Methodologies to Compare IC Engine Power Assembly Interface Materials

To meet the needs of higher power, lower weight and better emissions IC engines, component manufacturers develop new materials, coatings and surface technologies (e.g. surface texture). In this paper methodologies have been developed for comparing & ranking interface materials with custom-built rigs built in GE Global Research, Bangalore for large sized IC engines. This work will discuss the three methodologies developed using: i) Journal Bearing Rig ii) Piston-Liner Rig and the iii) Valve-seat rig. The Journal bearing Rig can be spun to engine linear speeds with lubricant heated to engine oil temperature. The loading is performed using a hydraulic system. Seizure, steady state wear and start stop tests can be performed on this rig. The piston liner rig can accommodate a section of the liner and ring from an actual engine. The combination of the pneumatic mechanism and the 2-axis load cell can load and measure the normal load & frictional load. The piston ring-liner simulates interface hot engine temperatures and contact pressures at TDC/BDC. Scuffing & wear tests can be performed with this test rig to compare scuffing limits and steady state wear rates. The valve-seat rig fixture is built within a MTS frame and can accommodate small sections of the actual engine valve and seat. Normal load and the fretting stroke is simulated using MTS hydraulic system A furnace is used around the fixture to simulate higher temperatures. Case studies comparing & ranking different coatings/repair coatings and oil additives etc. will be presented in this work to showcase the effectiveness of the methodology. Tests using this methodology can be typically performed in 10 % of time & cost of actual engine test.

Experimental and kinetic analysis of hydrothermal aging effects on ammonia adsorption capacity over a commercial Cu-zeolite selective catalytic reduction catalyst

Ammonia/urea selective catalytic reduction is an efficient technology to control NOx emission from diesel engines. One of its critical challenges is the performance degradation of selective catalytic reduction catalysts due to the hydrothermal aging experienced in real-world operations during the lifetime. In this study, hydrothermal aging effects on the reduction of ammonia adsorption capacity over a commercial Cu-zeolite selective catalytic reduction catalyst were investigated under actual engine exhaust conditions. Ammonia adsorption site densities of the selective catalytic reduction catalysts aged at two different temperatures of 750°C and 850°C for 25 h with 10% H2O were experimentally measured and compared to that of fresh catalyst on a dynamometer test bench with a heavy-duty diesel engine. The test results revealed that hydrothermal aging significantly decreased the ammonia adsorption capacity of the current commercial Cu-zeolite selective catalytic reduction catalyst. Hydrothermal treatment at 750°C reduced the ammonia adsorption site to 62.5% level of that of fresh catalyst, while hydrothermal treatment at 850°C lowered the adsorption site to 37.0% level of that of fresh catalyst. Also, in this study, numerical simulation and kinetic analysis were carried out to quantify the impact of hydrothermal aging on the reduction of ammonia adsorption capacity by introducing an aging coefficient. The kinetic parameter calibrations based on actual diesel engine tests with a commercial monolith Cu-zeolite selective catalytic reduction catalyst provided a highly realistic kinetic parameter set of ammonia adsorption/desorption and enabled a mathematical description of hydrothermal aging effect.

Simulation and Experimental Study of SCR Injection System

Abstract According to actual engineering test, we design a linear controlled spray ammonia grille, and apply it to the SCR injection system of ship tail gas treatment. In this paper, the geometric model of ammonia injection grid was built in the flue of diesel engine, and the effects of spray atomization, ammonia uniformity and urea droplet distribution on spray atomization were simulated. Then the test bench was set up to observe the injection status of the ammonia injection grille. The NOx content of the outlet was measured by the original data of the flue gas, and the experimental data were processed. We calculate the denitrification rate by taking the average value to verify the correctness of the spray ammonia grid scheme.

Seizure Improved Lead-Free Electroplated Bearing Overlay System for Heavy-Duty Truck and Off-Highway Applications

The move to lead-free bearing materials is well known, and upcoming legislation, such as the restriction of hazardous substances, is increasing the drive to extend this trend toward heavy-duty diesel truck and off-highway applications. During the development of lead-free systems, new electroplated overlays and bronze-based substrates have been developed by various suppliers, but little attention has been given to the interlayer or diffusion barrier between the overlay and substrate materials. This interlayer is particularly necessary for tin-based solutions as it prevents the rapid diffusion of overlay species into the bronze substrate. The present development focuses on improving this often overlooked element in the system and provides a further robustness that could even be adapted to lead-based systems where increased performance is required. The incorporation of hexagonal boron nitride (hBN) as a solid lubricant in the nickel interlayer changes dramatically the interlayer properties and provides more typical bearing-like behavior for seizure resistance and scuff performance compared to nickel alone. The paper details the findings of respective rig tests as well as an actual engine test supporting the change in material characteristics and the associated improvement in seizure resistance.

Emission prediction in conceptual design of the aircraft engines using augmented CRN

ABSTRACTThe semi-analytical prediction of pollutants emissions from gas turbines in the conceptual design phase is addressed in this paper. The necessity of this work arose from an urgent need for a comprehensive model that can quickly provide data in the conceptual design phase. Based on the available inputs data in the initial phases of the design process, a chemical reactor network (CRN) is defined to model the combustion with a detailed chemistry. In this way, three different chemical mechanisms are studied for Jet-A aviation fuel. Furthermore, the droplet evaporation for liquid fuel and the non-uniformity in fuel-air mixture are modelled. The results of a developed augmented modelling tool are compared with the pollutants data of two annular engine's combustors. The CRN results have good agreement with the actual engine test rig emissions output. In conclusion, the augmented CRN has shown to be efficient in predicting engine emissions with a very short executing time (few seconds) using a small CPU requirement such as a personal computer.

NOX및 NH3Slip 저감을 위한 Urea-SCR 제어기반 모델 개발 및 검증

저감효율에 대한 실험 조건 및 데이터를 획득하였다. 또한, 제안된 모델은 Rig 실험에서 사용한 실험조건과 결과데이터를 이용하여 Matlab 을 통해 검증하였으며 시뮬레이션 시 필요한 모델의 파라미터 값들은 실험데이터를 기반으로 최적화하였다. Abstract: To satisfy stricter NOX emission regulations for light- and heavy-duty diesel vehicles, a control algorithm needs to be developed based on a selective catalytic reaction (SCR) dynamics model for chemical reactions. This paper presents the development and validation of a SCR dynamics model through test rig experiments and MATLAB simulations. A nonlinear state space model is proposed based on the mass conservation law of chemical reactions in the SCR dynamics model. Experiments were performed on a test rig to evaluate the effects of the NOX and NH3 concentrations, gas temperature, and space velocity on the NOX conversion efficiency for the urea–SCR system. The parameter values of the proposed SCR model were identified using the experimental datasets. Finally, a control-oriented model for an SCR system was developed and validated from the experimental data in a MATLAB simulation. The results of this study should contribute toward developing a closed-loop control strategy for NOX and NH3 slip reduction in the urea–SCR system for an actual engine test bench.