Real Engine Test Research Articles

Co-optimization and prediction of high-efficiency combustion and zero-carbon emission at part load in the hydrogen direct injection engine based on VVT, split injection and ANN

Hydrogen fuel holds great promise for accelerating the energy sector's decarbonization efforts. However, hydrogen's unique properties pose challenges for hydrogen direct injection (HDI) engines, such as differences in airflow exchange capabilities for very low density and reduced combustion rates due to lean burn conditions. This study investigates the impact of combined variable valve timing (VVT) and split injection strategies on HDI engine combustion, efficiency, and emissions. Using Artificial Neural Network (ANN) models and experimental data, predictive models for Brake Thermal Efficiency (BTE) and Nitrogen Oxide (NOx) emissions were developed. Adjusting intake and exhaust valve timings improved BTE by up to 2.5 % and 1.8 %, respectively, while reducing NOx emissions by 48.9 % and 31.1 % under specific conditions. Optimizing split injection alongside VVT further increased BTE by 1.2 % and 0.9 %, but increased NOx emissions by 29.9 % and 26.5 %. The flexible application of VVT and split injection strategies aims to balance efficiency gains with emissions control. The ANN-based models demonstrated high accuracy (R2 > 0.974), proving reliable substitutes for real-engine testing in certain conditions. In conclusion, this research highlights the potential of VVT and split injection strategies to enhance HDI engine performance while mitigating environmental impact, supporting the transition to sustainable energy solutions.

Study of water and hydrogen addition on the pyrolysis and combustion characteristics of isooctane

Water injection and hydrogen combustion technologies have gained widespread attention in recent years. Combining H2O and H2 injection could bring more desirable combustion based on the needs of different engine conditions. To fully explore what effects the simultaneous injection of H2O and H2 would have on the combustion process of isooctane, three different subtests were performed in this study: investigation on chemical reaction mechanism, the laminar flame speed measurements and real engine tests. Firstly, H2O and H2 were added to the JSR (Jet Stirred Reactor) reactor to analyze the synergistic effect of H2O and H2 on the pyrolysis process of isooctane. The experimental results showed that the addition of H2O and H2 leads to an increase of OH and H radicals, which increases the concentrations of C1-C3 species and decreases the concentrations of C4 species. To further investigate the effect of H2O and H2 on the radical reaction of isooctane combustion process, this study then measured the laminar flame speed of IC8H18/H2/O2/H2O gas mixture by using constant volume combustion bomb, and found that water injection would reduce the laminar flame speed, and H2 would increase the laminar flame speed accordingly. Sensitivity analysis showed that it was more sensitive to reactions R1, R97 and R12, and was more sensitive to H2O than to H2. Finally, real engine tests were performed on a modified 1.5L gasoline equipped with port H2O and H2 injection systems at 1300 rpm with 30% throttle opening. The results showed that the use of H2O and H2 permitted the manipulation of engine combustion speed. Specifically, H2O injection led to a decrease in the peak cylinder pressure; and the addition of H2 increased the cylinder pressure again·H2O injection resulted in increased ignition delay and slower flame spread, slowing the engine's burn rate when needed. Using H2 addition led to a short ignition delay and accelerated combustion velocity, which counteracted the negative impacts of H2O injection and elevated the engine combustion speed to optimize efficiency. In summary, this paper revealed the complementary coordination between H2O and H2 through experimental and simulation studies. It will provide theoretical guidance for the development of H2O injection with H2 technology for gasoline engines.

Internal Combustion Engine Modeling Framework in Simulink: Combustion Modeling

An internal combustion engine modeling framework has been developed in the MATLAB/Simulink environment to allow engine component blocks to be connected in a physically representative manner to reduce the model build time. Each component block, derived from physical laws, interacts with other blocks according to block connection. In this series paper, detailed combustion modeling is presented among several engine subsystems. In the engine modeling framework, combustion is represented by a spherical flame propagating from the spark plug, and the burn rate is correlated to combustion chamber geometry, laminar flame speed, and turbulence. To accurately predict the burn rate, the quasi-dimensional model requires tuning. The combustion model has been computationally validated in a previous study and will be experimentally validated with real engine test data in the next series paper.

Influence of thermal barrier coating on partially premixed combustion in internal combustion engine

Nowadays, improving the thermal efficiency of internal combustion engine (IC Engine) has becoming increasingly essential. In this paper, the influences of thermal barrier coating (TBC) on the near wall combustion and pollutant distribution in Gasoline/Diesel RCCI (Reactivity Controlled Compression Ignition) and GCI (Gasoline Compression Ignition) combustion are investigated. Mathematical model of TBC is applied in Kiva3v CFD code for the numerical investigation, and GCI experiments is conducted for the real engine tests. The result shows that for Gasoline/Diesel RCCI combustion, spray/wall impingement is observed resulting in fuel film which becomes the main source of near wall soot formation. While for GCI combustion, no film is found and most of the pollutants are concentrated in the bowl region. A thermal reorganization effect is found with TBC, which not only keeps higher near wall temperature for the chemical reaction, but also enlarges the bowl-center high temperature area. By applying TBC, the thermal efficiency can be improved for both combustion modes. Higher peak pressure and advanced combustion phase are also produced which accelerate the boundary combustion especially in the squish region, therefore both unburned products and soot can be reduced at the cost of increased NOx emission.

Thermoacoustic engine as waste heat recovery system on extended range hybrid electric vehicles

Waste heat recovery (WHR) systems suggest a promising solution for reducing vehicle CO2 emissions in order to meet the CAFE targets by 2025. This paper presents a methodology to improve the overall efficiency of a combined cycle machine consisting of a reciprocating internal combustion engine (ICE) coupled to a thermoacoustic (TAE) machine used for thermal-to-electric WHR. It investigates the potential of calibrating the ICE at some specific points of its engine map in order to achieve an optimal overall efficiency when coupled to the bottoming thermoacoustic cycle. A three-cylinder gasoline engine is modeled using GT suite code and the effect of spark timing delay on exhaust temperature, exhaust flow and engine brake efficiency are compared to real engine test bench values. Three bottoming thermoacoustic configurations coupled to this ICE are modeled and calibrated according to test results performed on a thermoacoustic machine prototype. The resulting electrical power recovery from the exhaust gas is analyzed and assessed. A Range Extender Hybrid Electric Vehicle (EREV) is considered and fuel consumption is simulated on the WLTC. The results revealed an added value for adding a multi-module TAE in series, to optimize heat recovery with a potential of consumption reduction up to 7.6%. Results have also shown interest in delaying the ignition, enabling higher exhaust temperature and mass flow rate which tend to positively impact the TAE machine. The proposed method is also beneficial in the way that it avoids knocking problems and enables the future design of higher compression ratio engines for auxiliary power unit on EREV.

Teaching Nonlinear Model Predictive Control with MATLAB/Simulink and an Internal Combustion Engine Test Bench

Model Predictive Control (MPC) is used for more and more applications in an industrial context. The applications are characterized by increasing complexity while the available computation time is getting smaller and smaller. MPC is the most important advanced control technique with even increasing importance. Hence, this topic should be covered in control lectures during the academic studies in order to prepare students for their future work. For the successful implementation of MPC algorithms, knowledge from multiple disciplines is crucial and needs to be taught. Besides teaching knowledge in classical control theory, especially fundamentals in the fields of modeling, simulation and numerical optimization are required for understanding MPC. Programming skills are inevitable to apply the concept in real-world applications.This paper presents a concept for teaching MPC from the theory to the application to real-world systems. Details about the lectures covering the relevant topics are given. In the hands-on exercises, students implement their own linear as well as nonlinear MPC in MATLAB/Simulink. As example application in the exercises, the air path of a turbocharged diesel engine with high pressure exhaust gas recirculation is investigated. At the end of the semester, students can test their developed controllers on a real diesel engine test bench and compete against each other for the best control performance.

Fast engine model for FMU-less small turbojet engines

The focus of this paper is on small low-cost turbojet engines equipped with a gear-type fuel pump rather than a more traditional fuel metering unit. The incorporation of such type of fuel flow actuation devices introduce additional nonlinearities into the system and therefore make traditional modeling and system identification methods difficult to apply. In this paper, we propose a nonlinear fast engine model structure that can be used for various applications, including identification, modeling and simulation, and controller design of such sub-class turbojet engines. A high-fidelity turbojet engine model including its nonlinear gear-type fuel pump is developed, which is later used to generate the fast engine model. The parameters of the fast engine model are estimated using regression analysis. The identification procedure is also applied to real engine test data to verify the proposed approach.

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.

A novel method for the determination of the change in blade tip timing probe sensing position due to steady movements

Abstract The correlation of blade tip timing (BTT) measurements against strain gauge (SG) measurements and finite element (FE) predictions includes a number of uncertainties. One of the main ones is the steady movement of the blades (i.e. change in their mean position and orientation). This causes the sensing positions of the probes relative to a blade tip to deviate from their intended (nominal) positions, leading to deceptive results for the BTT amplitude and the corresponding stress levels. Such movements are caused by variations in static loading conditions (thermal and pressure) associated with changes in the operating speed. A novel method is introduced for the determination of three basic types of blade tip steady movements: axial; lean; untwist. The method relies on linking the shift in the averages of the BTT data to a number of geometrical relations, depending on the type of movement. Not more than two probes (to be placed at different axial positions) are needed to measure all three types of movement. The method is validated by simulations using a novel BTT simulator, and by measurements from both a test rig and real engine tests. The validated results demonstrate the great potential of the method for practical applications.

Simulation of an aircraft radial engine misfire detection

The misfire phenomenon is particularly unfavourable in aircraft engines because it affects the stability and reliability of work. This paper presents the algorithm for detecting ignition failure in a radial aircraft engine. The Crankshaft Velocity Fluctuation method was applied, which consists in analysing changes in the crankshaft speed signal as a function of time. A zero-dimensional model of the aircraft engine was developed in order to perform the research. The validation of the model was performed using the results from the test bench. The model was subjected to simulation tests in fixed operating conditions. Based on the engine speed signal obtained as a result of the simulation, the normalized second derivative of the signal was determined based on the adopted algorithm. On the basis of this derivative, a criterion was defined to assess the occurrence of the misfire phenomenon. The results of the calculations can be compared in future with the results of the real engine tests.

Estimation of the in-cylinder residual mass fraction at intake valve closing in a two-stroke high-speed direct-injection compression-ignition engine

New combustion concepts and engine designs are being currently investigated in order to comply with upcoming pollutant regulations and reduce fuel consumption. In this context, two-stroke architectures appear as a promising solution for the implementation of some combustion concepts. However, scavenging processes in a two-stroke engine are much more challenging than for a four-stroke engine, and the residual mass of burnt gases retained inside the cylinder needs to be properly determined in order to keep control over the in-cylinder composition, hence over the combustion conditions and pollutant emissions. In this study, a new methodology for the estimation of the internal residual gas fraction is introduced, which is based on the thermodynamic processes occurring in the engine investigated and makes use of basic engine instrumentation and measurement equipment usually available in a conventional test cell. Several versions of the estimator were developed so that different requirements could be met, such as those of real-time estimation on an engine test bench but with reduced precision or, on the contrary, highly precise but time-consuming computations for post-processing purposes and combustion diagnosis. The consistency of the internal residual gas estimator was then validated through its application to real engine tests at different operating points.

Effect of engine exhaust gas pulsations on the performance of a thermoelectric generator for wasted heat recovery: An experimental and analytical investigation

Using thermoelectric generator (TEG) for waste heat recovery on internal combustion engines is a promising solution for efficiency improvement. This study investigates the behavior of TEG during engine operation. It distinguishes the effect of the engine flow properties on the TEG performance. Three test rigs have been designed and built to investigate this effect. The results confirm that there are two main engine exhaust gas properties that affect the TEG performance, namely: engine exhaust gas composition and engine exhaust gas pulsation.An analytical model has been developed to identify and quantify the effect of each parameter on the convective heat transfer coefficient between the exhaust gas and the thermoelectric module, hence on the TEG performance. Test results show a difference in the TEG output power up to 30% between hot air and real engine test at perfectly similar TEG inlet temperature and mass flow rate. The model identifies that 5–12% of this difference is related to the gas composition whereas another test rig proves that the engine exhaust pulsating flow is responsible for the remaining difference (88–95%). Further studies will be conducted to improve the TEG design thanks to this pulsation effect behavior.

Optimum design for intake and exhaust system of a heavy-duty diesel engine by using DFSS methodology

In this study, an optimum design for intake and exhaust system of a heavy-duty diesel engine was conducted by using the well-known design for six sigma (DFSS) methodology. As a result of this work, the NOx emission regulation has been successfully satisfied while minimizing the fuel consumption. On the basis of this DFSS work, the design robustness of the engine system was also enhanced. Hence, it is expected that the final design proposal would reduce the variability in brake thermal efficiency (BTE) that could be caused by the harsh environment and the system aging. Especially, this work has successfully raised the amount of exhaust gas recirculation (EGR) up to the target level by adopting the venturi tubes in the intake and exhaust lines. In this study, engine cycle simulation technique was employed to assess the effect of the various design parameters and the final design proposal was verified through a real engine test. The current optimum design work has considered four control factors such as the size of turbocharger, the diameter of intake and exhaust venturi pipes, and the efficiency of EGR cooler. Here, an L9 orthogonal array was employed to efficiently choose the best design proposal among 81 design combinations (i.e., four independent control factors which individually have three different levels).

Development of Compressor Blade Prognostics and Health Management for Large Gas Turbine Engine

DOOSAN has been developed large gas turbine since 2014 as a national project in Korea. Recent researches showed that one of major risk item in gas turbine development is compressor rotor blade failure. There are several events of compressor rotor blade failure which have occurred over the last few years, in some cases causing catastrophic damage to the entire compressor. In response to these issues, DOOSAN started to develop compressor monitoring system to prevent failures and diagnose blades to assess the structural integrity of each blades. This paper presents the ideas and plans how DOOSAN will develop the system with latest sensors. Additionally, validation methods will be presented using sub-scaled test rig in 2018 and real scale engine test in 2019, respectively.

Transient Performance Analysis of an Industrial Gas Turbine Operating on Low-Calorific Fuels

The demand for more environmentally friendly and economic power production has led to an increasing interest to utilize alternative fuels. In the past, several investigations focusing on the effect of low-calorific fuels on the combustion process and steady-state performance have been published. However, it is also important to consider the transient behavior of the gas turbine when operating on nonconventional fuels. The alternative fuels contain very often a large amount of dilutants resulting in a low energy density. Therefore, a higher fuel flow rate is required, which can impact the dynamic behavior of the gas turbine. This paper will present an investigation of the transient behavior of the all-radial OP16 gas turbine. The OP16 is an industrial gas turbine rated at 1.9 MW, which has the capability to burn a wide range of fuels including ultra-low-calorific gaseous fuels. The transient behavior is simulated using the commercial software GSP including the recently added thermal network modeling functionality. The steady-state and transient performance model is thoroughly validated using real engine test data. The developed model is used to simulate and analyze the physical behavior of the gas turbine when performing load sheds. From the simulations, it is found that the energy density of the fuel has a noticeable effect on the rotor over-speed and must be considered when designing the fuel control.

실시간 가스터빈 엔진 시뮬레이터를 적용한 소형 제트엔진 성능시험장치 개발

가상엔진 시뮬레이터를 이용한 시험장치는 실제 엔진을 이용한 시험과 유사한 시험 수행을 통하여 엔진 시험 횟수를 줄이고 동일한 조건에서 반복 시험이 가능하므로 엔진 정비 및 운용비용을 감소시켜 준다. 그리고 실제 시험에서 수행하기 어려운 극한 상황을 쉽게 구현할 수 있기 때문에 실제 엔진 시험 시 발생할 수 있는 엔진 손상 및 위험한 시험을 대체해 준다. 본 연구에서는 사전 연구를 통해 개발하였던 소형제트엔진 성능시험장치에 실시간 엔진 모델을 적용하여 실제 엔진 시험과 가상 엔진 시험을 다목적으로 수행할 수 있는 업그레이드 된 소형제트엔진 성능시험장치를 개발하였다. 새로 개발된 다목적 소형 제트엔진 성능시험장치는 교육용 및 연구용으로 더욱 다양하게 활용될 수 있을 것으로 기대된다. Test device using virtual engine simulator can help reduce the number of engine tests through tests similar to the actual engine tests and repeat the test under the same condition, and thus reduce the engine maintenance and operating costs. Also, as it is possible to easily implement extreme conditions in which it is hard to conduct actual tests, it can prevent engine damages that may happen during the actual engine test under such conditions. In this study, an upgraded small jet engine performance test device was developed that can conduct both real and virtual engine test by applying real-time engine model to the existing micro jet engine performance test device that was previously developed by authors. This newly developed multi-purpose small jet engine performance test device is expected to be used for various educational and research purposes.

Dynamic Oil Consumption Measurement of Internal Combustion Engines using Laser Spectroscopy

A new approach has been developed to measure dynamic consumption of lubricant oil in an internal combustion engine. It is based on the already known technique where sulfur is used as a natural tracer of the engine oil. Since ejection of motor oil in gaseous form into the exhaust is by far the main source of engine oil consumption, detection of sulfur in the exhaust emission is a valuable way to measure engine oil consumption in a dynamic way. In earlier approaches, this is done by converting all sulfur containing chemical components into SO2 by thermal pyrolysis in a high temperature furnace at atmospheric pressure. The so-formed SO2 then is detected by broadband-UV-induced fluorescence or mass spectrometric methods. The challenge is to reach the necessary detection limit of 50 ppb. The new approach presented here includes sulfur conversion in a low-pressure discharge cell and laser-induced fluorescence with wavelength and fluorescence lifetime selection. A limit of detection down to 10 ppb at a temporal resolution in the time scale of few seconds is reached. Extensive, promising studies have been performed at a real engine test bench. Future developments of a compact, mobile device based on these improvements are discussed.

Effect of the Biot Number on Metal Temperature of Thermal-Barrier-Coated Turbine Parts—Real Engine Measurements

For numerous hot gas parts (e.g., blades or vanes) of a gas turbine, thermal barrier coating (TBC) is used to reduce the metal temperature to a limit that is acceptable for the component and the required lifetime. However, the ability of the TBC to reduce the metal temperature is not constant, it is a function of Biot and Reynolds number. This behavior might lead to a vane's or blade's metal temperature increase at a lower load relative to a reference load condition of the gas turbine (i.e., at lower operating Reynolds number). A measurement campaign has been performed to evaluate metal temperature measurements on uncoated and coated turbine parts in Alstom's GT26 test power plant in Switzerland. Therefore, the impact of varying Reynolds number on the ability of the TBC to protect the turbine components was evaluated. This paper reports on engine-run validation, including details on the application of temperature sensors on thermal-barrier-coated parts. Different methods for the application of thermocouples that were taken into account during the development of the application process are shown. Measurement results for a range of Reynolds number are given and compared to model predictions. Focus of the evaluation is on the measurements underneath the TBC. The impact of different Reynolds number on the ability of the TBC to protect the parts against the hot gas is shown. TBC coated components show under certain circumstances higher metal temperatures at lower load compared to a reference load condition. The measurement values obtained from real engine tests can be confirmed by 1D-model predictions that explain the dependency of the TBC effect on Biot and Reynolds number.

Application of Microwave Sensing to Blade Health Monitoring

This paper discusses the application of microwave sensing to turbine airfoil health monitoring. The proposed microwave system operates at 6- and 24-GHz and is applicable to both blade tip-clearance and blade tip-timing measurements. One of the main advantages of microwave systems, compared to other technology such as capacitive or eddy current, is that it can be installed for long term operations in the harsh environment of the first turbine stages. The monitoring of blade tip-timing and tip-clearance pattern is useful for detecting abnormal blade behavior due to structural damage. Such a sensing system can also be used in actively maintaining optimal blade-to-casing clearance, thereby enhancing turbine efficiency. This paper presents blade tip-clearance pattern monitoring based on microwave measurements. First, a laboratory study shows the ability of the system to consistently measure tip clearance pattern. Then tip clearance pattern measurements from a real engine test are presented. While this paper presents results from system testing on tip clearance, it is expected that this study will be carried forward in the next phase to demonstrate tip-timing measurement and further, to show how such as system can form the basis for a more comprehensive health management system.

Combustion Engine Air Intake Theoretical Modelling, Model-Verfication & Application to Optimal Valve Actuation

AbstractA theoretical model for the air intake of a four stroke internal combustion engine is derived from first principles, the conservation of mass and the conservation of energy. Full valve actuation is taken into account: The opening angle of both the intake as well as the exhaust valve, as well as the variable valve lift are considered as plant inputs, which may be manipulated to maximize the air intake rate and hence the power, the engine delivers. The theoretical model is verified by comparing the model output to steady state data collected at an engine test bench. Therefor a formal connection between state-of-the-art mean value models and the crank angle resolved physical model must be established. The pressure loss in the intake valve is considered a disturbance of the ideal cylinder filling dynamics, which is estimated using non-linear optimization techniques. The intended purpose of physical model building for the cylinder air intake is prediction of the air intake rate and computation of optimal valve control action before a lot of effort is put into a real experiment at the engine test bench. A significant reduction of operating time and cost consumed by the real engine test bench can be achieved, if a small subset of steady state measurements are used to compute a meta-model for the pressure loss. The combination of the black-box pressure loss model and the air intake model allows for prediction of the air intake rate at unknown operating points of the engine with sufficient accuracy.