Waste Gate Research Articles

Optimization of the Performance of a Formula SAE Engine by Means of a Wastegate Valve Electronically Actuated

The engine and vehicle design in Formula SAE competition has to accomplish a strict regulation. In order to limit the maximum power, an air restrictor of 20mm of diameter is imposed in the intake line. To overcome the limitations caused by the restrictor, Firenze Race Team equipped its one-cylinder engine with a turbocharger, which is conventionally provided with a wastegate (WG) valve to limit the maximum boost pressure and avoid knocking phenomena. Typically, the WG valve is controlled by a pneumatic actuator, which opens the valve according to a defined and constant maximum boost pressure downstream the compressor in the whole engine operating range. Therefore, the boost pressure at high engine speed, in which knocking problems are less intense and the volumetric efficiency is lower, is limited by the threshold value defined at medium-low engine speeds, i.e. the pneumatic WG limits the maximum power that the engine can supply. In this study, the implementation of an electronic control system for the WG valve is described together with a dedicated control strategy aimed at providing the desired boost pressure at full load for each engine speed, in order to get the maximum power avoiding knocking phenomena. The electronic WG provided higher power values and a more extended torque curve in comparison to the conventional pneumatic one.

A Second-Order Sliding Mode Observer for Fault Detection and Isolation of Turbocharged SI Engines

This paper proposes a novel method for detection and isolation of wastegate (WG) faults in a turbocharged (TC) gasoline engine. This paper starts with a fault effect analysis on the WG faults, including WG stuck open and stuck closed, which is an early step in a detection strategy design. Then, a second-order sliding-mode observer (SOSMO) is proposed to capture the exhaust manifold dynamics. The observer uses experimentally validated engine models to estimate the WG position and a virtual force. The virtual force represents the external disturbances that disrupt the WG operation and enables the proposed SOSMO to estimate the WG position robust to the faults. Using this force, a detection and isolation algorithm is presented and experimentally verified on a modern TC gasoline engine. Test bench results show that the proposed strategy can successfully detect and isolate the two different WG faults.

가솔린 자동차 터보차져용 WGV Head의 금속 분말 사출성형 해석

Abstract : The waste gate valve (WGV) for gasoline vehicles operate in a harsh high-temperature environment. Hence, WGVs are typically made of Inconel 713C, which is a type of Ni-based superalloy. Recently, the metal injection molding (MIM) process has attracted considerable attention for parts used under high-temperature conditions. In this study, an MIM analysis for the head and other parts of the WGV is conducted using a commercial CAE program Moldflow. Further, optimal manufacturing conditions are determined by analyzing flow characteristics at various injection times and locations. Moreover, to improve the accuracy of the analysis results, we compare the actual temperature of the mold during injection processing with that observed through the analysis. As the results, metal injection patterns of analysis are well in accord with these of short shot test. And the temperature variations of analysis is also very similar with those of feedstock when metal injection molding. Key words : Metal injection molding(금속분말 사출성형), Waste gate valve(웨이스트게이트 벨브), Turbo charger(터보차져), Metal injection molding analysis(금속분말 사출성형해석)

금속분말사출성형공법을 이용한 가솔린 터보차저의 웨이스트 게이트 밸브 어셈블리 열 충격 내구 시험

A waste gate valve (WGV) assembly for a gasoline turbocharger is typically manufactured by means of precision casting. In this study, however, it was newly manufactured in a more innovative way, metal injection molding (MIM) using Inconel 713C alloy, and its performance was tested in a 1.6L direct injection gasoline engine by a thermal shock durability test that lasted 300 hours, after which the results were compared to those of a precision-cast WGV assembly with regard to the engine intake boost pressure, turbine wheel speed, and transient intake pressure. It was found that the two WGV assemblies showed similar performance levels throughout the durability test.

The Variable Outlet Turbine Concept for Turbochargers

A variable geometry concept for advanced turbocharger (TC) systems is presented. The variability of the device is based on outlet area changes as opposed to the more common systems that are based on inlet turbine geometry changes. In addition to the conventional variable turbine geometry (VTG), the new variable turbine type is termed variable outlet turbine (VOT). The flow variability is achieved by variation of the flow cross section at the turbine outlet using an axial displacement of a sliding sleeve over the exducer and provides a simple solution for flow variability. In order to predict the aerodynamic performance and to analyze the loss mechanisms of this new turbine, the flow field of the VOT is calculated by means of steady state 3D-CFD (computational fluid dynamics) simulations. The VOT design is optimized by finding a good balance between clearance and outlet losses. Furthermore, experimental results of the VOT are presented and compared to a turbine equipped with a waste gate (WG) that demonstrates an efficiency advantage of 5%. Additionally, engine performance measurements were carried out to investigate the influence of the VOT on fuel consumption and to asses the functionality of the new pneumatic actuating system. The VOT engine tests show also performance advantage in comparison to a WG turbine especially toward high engine loads. It is found that the use of the VOT at this condition shows a turbine efficiency advantage of 6% related to a reduction in engine fuel consumption of 1.4%. The behavior at part load is neutral and the peak turbine efficiency of the VOT is comparable with a fix turbine geometry.

Modeling and Estimation of Unmeasured Variables in a Wastegate Operated Turbocharger

Estimation of relevant turbocharger variables is crucial for proper operation and monitoring of turbocharged (TC) engines, which are important in improving fuel economy of vehicles. This paper presents mean-value models developed for estimating gas flow over the turbine and the wastegate (WG), the wastegate position, and the compressor speed in a TC gasoline engine. The turbine is modeled by an isentropic nozzle with a constant area and an effective pressure ratio calculated from the turbine upstream and downstream pressures. Another physically sensible model is developed for estimating either the WG flow or position. Provided the WG position is available, the WG flow is estimated using the orifice model for compressible fluids. The WG position is predicted considering forces from the WG passing flow and actuator. Moreover, a model for estimating the compressor speed in low and medium compressor pressure ratios is proposed, using the compressor head and efficiency modified by the turbine effective pressure ratio. The estimates of the turbocharger variables match well with the experimentally measured data. The three proposed models are simple in structure, accurate enough to be utilized for engine modeling, and suitable to be validated and calibrated on an internal combustion engine in a test cell.

An Experimental and Theoretical Study of the Effects of Excess Air Ratio and Waste Gate Opening Pressure Threshold on NOx Emission and Performance in a Turbocharged CNG SI Engine

Turbocharged CNG engines produce high NOx emission due to the fuel type and high combustion temperature. In this research, the effects of lean-burn and waste gate opening pressure threshold on NOx emission are studied theoretically and experimentally at WOT condition as well as 13-mode ECE-R49 test cycle. A code is developed in MATLAB environment for predicting engine NOx and the results are validated with the research experiments. Simulations show that NOx increases by increase of excess air ratio and reaches at most to 2486ppm at excess air ratio of 1.1 and then decreases. It is also experimentally found that changing waste gate opening pressure threshold from 165mmHg to 200 and 265mmHg decreases total bsNOx at a rate of 6% and 12% respectively. Increase of the threshold to 323mmHg increases total bsNOx. Therefore, to minimize the cycle bsNOx, the threshold of 265mmHg is the optimum threshold for the engine between the four pressure thresholds experimented.

Tier 4 Interim 배기규제 만족을 위한 56kW급 오프로드 차량 EGR 적용에 관한 연구

비도로용 차량의 경우 대부분 디젤엔진을 사용하여 엔진의 특성상 PM과 NOx의 배출이 많은 단점이 있다. 승용 및 상용 디젤 차량의 경우 CRDI 및 후처리 장치를 적용하였고 후처리 장치로 DOC/DPF를 장착함으로써 PM은 약 90% 이상 저감 가능하다. 상반관계인 NOx는 EGR 사용을 통해 1차적으로 NOx 배출량을 감소시키고 LNT, Urea-SCR 등의 DeNOx 시스템으로 NOx의 배출량을 보다 현저히 저감시켜 배기규제를 만족시키고 있다. 본 연구에서는 tier 4 interim 배기규제를 만족하기 위해 56㎾급 오프로드 차량으로 연구를 진행하였다. NOx의 감소를 위해 WGT와 전자 제어방식의 HPL EGR 시스템을 적용하였고 CO와 THC, PM 배출가스를 줄이기 위해 DOC와 DPF를 사용하였다. EGR 시스템을 적용하기 위해 각 조건에 대한 기본 실험을 실시하여 EGR map을 작성하였다. 작성된 map을 NRTC 모드에서 시험하여 map의 적용성을 검증하고 tier 4 interim 배기규제 만족여부를 파악하였다.

Financial appraisal of wet mesophilic AD technology as a renewable energy and waste management technology

Anaerobic digestion (AD) has the potential to support diversion of organic waste from landfill and increase renewable energy production. However, diffusion of this technology has been uneven, with countries such as Germany and Sweden taking the lead, but limited diffusion in other countries such as the UK. In this context, this study explores the financial viability of AD in the UK to offer reasons why it has not been more widely used. This paper presents a model that calculates the Internal Rate of Return (IRR) on a twenty year investment in a 30,000 tonnes per annum wet mesophilic AD plant in the UK for the treatment of source separated organic waste, which is judged to be a suitable technology for the UK climate. The model evaluates the financial significance of the different alternative energy outputs from this AD plant and the resulting economic subsidies paid for renewable energy. Results show that renewable electricity and renewable heat sales supported by renewable electricity and renewable heat tariffs generates the greatest IRR (31.26%). All other uses of biogas generate an IRR in excess of 15%, and are judged to be a financially viable investment. Sensitivity analysis highlights the financial significance of: economic incentive payments and a waste management gate fee; and demonstrates that the fate of the digestate by-product is a source of financial uncertainty for AD investors.

Emissions from large-scale medium-speed diesel engines: 1. Influence of engine operation mode and turbocharger

The operation of four – stroke diesel engines in either propulsion or generator mode application has a strong influence on gaseous, smoke (soot) and particulates emissions. Tests were made with a supercharged after-cooled large-scale diesel engine (mean speed ∼ 500 rpm, power per cylinder ∼ 1 MW) burning mainly heavy fuel oil. Gaseous emissions (NOx, CO, HC) were measured according to the IMO technical code, smoke (soot) emissions were determined optically and particulate matter (PM) was measured using a gravimetric impactor for five size fractions. Impact on gaseous emissions, smoke (soot) and PM was found when analysing the effects of the engine operating mode, fuel nozzle, start of injection (SOI), and load (speed). Results show that the exhaust emission was also highly dependent on the engine turbocharger system, especially the by-pass control, but was not affected by waste gate control. The gaseous and soot emissions were less for the generator mode in the total load region, decreasing with the load. PM emissions were found to decrease with the load for the propulsion mode, while showing an increase with the load for the generator mode.

Engine Control of a Downsized Spark Ignited Engine: from Simulation to Vehicle

Tightening European standards on fuel consumption and pollutant emissions reduction lead to a sophistication of engine concepts and associated control. Since few years, downsizing (reduction of the engine displacement) appears as a major way to achieve those requirements for spark ignition engines. Efficient performance and drivability can be then achieved with a direct injection downsized engine with turbocharging and Variable Camshaft Timing (VCT). One of the major issues of the torque-oriented control is in-cylinder mass observation and control. To have an efficient torque response, the in-cylinder trapped mass, adjusted by the throttle and the waste gate, must be controlled with accuracy according to performance and drivability requirements. Depending on admission and exhaust pressures, the twin VCT will allow to control in-cylinder burned gases rate to reduce fuel consumption and pollutant emissions, and air scavenging to improve transient speed response. Another major issue is in-cylinder trapped mass and air scavenging prediction for AFR control. In this paper, we propose a model-based approach to achieve those engine control issues. The first challenge is to design accurate observers for non-measurable variables (in-cylinder burned gases and trapped air mass). The method is based on a complex high frequency 0D engine model, which has been validated on a large range of engine operating points and transient operations based on test bed results. Then, this model permits to design and learn open-loop nonlinear static observers of in-cylinder masses (based on neural network). The static and dynamic behavior of high frequency 0D engine model allows to achieve design of dynamic and closed-loop in-cylinder mass observation and prediction, multivariable and non-linear control of air path according to in-cylinder mass trajectory (trapped air mass & recirculated gases rate). Then, the complete engine control can be developed and validated on simulation and on a real time Software-In-the-Loop platform based on high frequency 0D engine model, before a complete validation and calibration on test bed. Finally, the complete torque-oriented engine control has been integrated on vehicle. From 0D engine model, a complete vehicle model has been set on real-time platform in order to validate engine control integration and design vehicle layout. The major issue is then supervision of engine control set points (torque, AFR, efficiency) according to engine states (start, idle, driver request, cut-off) and warm-up strategies.

Evaluation of various rich combustion strategies for HD-DI diesel engines

The diesel engine, because of its superior fuel economy compared with spark ignition engines, has attracted considerable attention. Significant improvement in their performance and engine emissions has been achieved. The use of various advanced internal measures has resulted in significant reduction of pollutant emissions inside the combustion chamber. Nevertheless, considering the increasingly restrictive 'engine-out' emission standards to be adopted, it appears that the use of air throttling systems is possibly inevitable in order to meet the future limits. This is because NOx and soot emissions are usually affected in the opposite way from the various internal measures. However, the use of conventional air throttling systems in DI diesel engines is not possible owing to the lean nature of diesel combustion, which does not permit the use of catalysts for controlling NOx emissions. Currently, alternative 172 D.T. Hountalas et al. solutions are proposed focusing on the use of a selective catalytic reduction system, requiring a carefully controlled injection of urea or NOx traps (adsorbers) When the storage capacity of the trap is reached, during normal lean operation, the engine must switch to rich operation in order to produce the necessary reducing agents, that is, CO and H2, which release the stored NOx to react with CO in a catalyst to finally form N2. In this work, an extended computational investigation has been conducted to examine various strategies for achieving rich combustion in diesel engines. Rich diesel combustion has recently attracted attention for the regeneration of NOx traps. Rich combustion can be achieved using either internal or external measures, (fuel injection at the exhaust manifold). Rich operation is expected to have a negative impact on engine performance and emissions resulting in an increase of brake specific fuel consumption (bsfc), soot and exhaust gas temperature. For this reason, in this work, various strategies are examined for achieving rich combustion using internal measures, namely intake air throttling or/and waste gate operation, EGR and late post injection. The investigation was conducted on a heavy-duty DI diesel engine, using a phenomenological simulation code that is based on a multizone combustion model. Information is provided concerning the impact of the various rich strategies examined on engine performance and emissions. This enables us to estimate the most appropriate one. Using this information, we established a combination of strategies to achieve the lowest possible λ value with acceptable overall fuel and soot penalties.

Modeling of a turbocharged SI engine

Turbocharged SI engines are a major possibility in the current trend of down-sized engines with preserved drivability performance. Considering control and supervision it is favorable to have a mean value model to be used e.g. in observer design. Such models of turbo engines are similar to those of naturally aspirated engines, but there are some special characteristics, e.g. the interconnected gas flows, the intercooler, the difference in relative sizes between the gas volumes (compared to naturally aspirated engines), the turbo, and the waste gate. Here, a model is developed with a strategy to find a model for each engine component (air filter, compressor, after cooler (or intercooler), throttle, engine, turbine, waste gate, and a lumped model for the catalyst and exhaust) as they behave in an engine setting. When investigating agreement with measured data and sensitivity of possible model structures, a number of interesting issues are raised. The experiments and the model validation have been performed on a Saab 2.3 1 production engine.

Modeling of a Turbo Charged SI Engine

Turbo charged SI engines are a major possibility in the current trend of down-sized engines with preserved drivability performance. Considering control and supervision it is favorable to have a mean value model to be used e.g. in observer design. Such models of turbo engines are similar to those of naturally aspirated engines, but there are some special characteristics, e.g. the interconnected gas flows, the intercooler, the difference in relative sizes between the gas volumes (compared to naturally aspirated engines), the turbo, and the waste gate. Here, a model is developed with a strategy to find a model for each engine component (air filter, compressor, after cooler (or intercooler), throttle, engine, turbine, waste gate, and a lumped model for the catalyst and exhaust) as they behave in an engine setting. When investigating agreement with measured data and sensitivity of possible model structures, a number of interesting issues are raised. The experiments and the model validation have been performed on a Saab 2.31 production engine.

Fault Diagnosis with Dynamic Neural Structure and Application to a Turbocharger

An attempt has been made to establish a nonlinear dynamic time discrete neuron model, the so called Dynamic Elementary Processor (DEP). This DEP disposes of local memory, in that it has dynamic states. Based on the DEP neuron, a dynamic Multi Layer Perceptron neural net (MLP) is proposed to identify nonparametric, multi-input single-output (MISO) models for nonlinear, dynamic systems. The identified models are used to build a bank similar to observer based schemes. The output residuals between the process and the bank models are used to detect and identify a fault in the process, if it has occurred. An empirical MISO model for the turbine of a turbosupercharger was identified to demonstrate the identification ability of the proposed DEP net with real data. The fault detection scheme was successfully applied to detect and diagnose a transient fault in the turbine waste gate.

Pressure Wave Supercharging of Passenger Car Diesel Engines

This study is based on experimental test results, typical for small passenger car diesel engines. The influence of engine size on the performance of the car was investigated using four different types of engine. The four types of engine were (a) naturally aspirated engine, (b) engine with turbocharger and waste gate, (c) engine with pressure wave supercharger (PWS) and (d) engine with PWS and intercooler. The performance of the car fitted with the pressure wave supercharger ComprexR* was examined and found to have excellent response, reduced fuel consumption and reduced exhaust emissions.