Wastegate Valve Research Articles

Performance Optimization of a Turbocharged Spark-Ignition VVA Engine at Part Load

Nowadays, modern internal combustion engines show more and more complex architectures in order to improve their performance. Referring to the spark-ignition (SI) engines, downsizing philosophy and Variable Valve Actuation (VVA) systems allow to reduce the Brake Specific Fuel Consumption (BSFC) at low and medium load, while maintaining the required performance at high load. On the other hand, the above solutions introduce additional degrees of freedom for the engine control, requiring longer calibration time and experimental effort. In the present work, a twin-cylinder turbocharged VVA SI engine is numerically investigated by a one-dimensional (1D) model (GT-PowerTM). The considered engine is equipped with a fully flexible VVA actuation system, realizing an Early Intake Valve Closure (EIVC) strategy. Proper "user routines" are implemented in the code to simulate turbulence and combustion processes. In a first stage, 1D engine model is validated against the experimental data under part load condition, both in terms of overall performance and combustion evolution. The validated 1D engine model is then integrated in a multipurpose commercial optimizer (mode FRONTIERTM) with the aim to identify the engine calibrations that simultaneously minimize BSFC and Brake Mean Effective Pressure (BMEP) under part load operation at a specified engine speed of 3000rpm. In particular, the decision parameters of the optimization process are the EIVC angle, the throttle valve opening and the waste-gate valve opening and combustion phasing. Proper constraints are assigned for the pressure in the intake plenum in order to limit the gas-dynamic noise radiated by the intake mouth. The adopted optimization approach shows the capability to reproduce with a very good accuracy the experimentally advised optimal calibration, corresponding to the numerically derived Pareto frontier in the Brake Mean Effective Pressure (BMEP)-BSFC tradeoff. The optimization also underlines the advantages of an engine calibration based on a combination of EIVC strategy and intake throttling, rather than a purely throttle-based calibration. The developed automatic procedure allows for a "virtual" calibration of the considered engine on completely theoretical basis and proves to be very helpful in reducing the experimental costs and the engine time-to-market.

Sizing and Simulation of a Piston-prop UAV

A sizing and simulation platform has been developed for the optimization of advanced configurations for aircrafts including, but not limited to, more electric, hybrid-electric, turbo-compound piston engines and fuel cell systems. In the present investigation the software has been applied to the simulation of a medium-altitude, medium-endurance unmanned aerial vehicle (UAV) equipped with a two-stroke diesel engine with a single stage turbo-compressor. The engine was simulated with a 1D code (AVL-Boost) taking into account several values of speed, air-fuel ratio and flight altitude. The behavior of the waste-gate valve at the different flight levels was also accounted for. The Willans line method is used to obtain the seal level and in flight performance map of scaled engines with the same configuration. The power requests of a reference 128kW engine and two scaled engines along the mission have been compared with the available power to discuss the potentiality of hybrid electric and turbo-compound configurations.

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)

Development of turbocharging system for diesel engines of power generation application at different altitudes

The environmental atmospheric density reduces with the increased altitude. For turbocharged diesel engines, boost pressure and mass flow rate of fresh air are decreased with the limited plateau self-compensation ability when the altitude increases to a certain value. The decreased air flow results in the reduction of output power of diesel engines, and the diesel engine performances affect the electric power of diesel generator set. Therefore, to solve the problem of diesel generator set operating at plateau, power recovery of diesel engines is essential for maintaining its performance. Boost pressure recovery provides an alternative solution to this problem. In this paper, a turbocharging system was developed for recovering the boost pressure according to a matching process. A control strategy of the waste-gate valve was confirmed, and two operating modes were determined based on the bypass flow ratio. The results show that boost pressure of the engine can be recovered with the matched turbocharging system at different altitudes. However, boost pressure recovery cannot make sure the power recovery of diesel engines due to the changing overall system efficiency and pumping process. Therefore, a method of fuel compensation was proposed, and it can achieve the power recovery target along with the valve control strategy for boost pressure recovery.

One-dimensional simulations and experimental analysis of a wastegated turbine for automotive engines under unsteady flow conditions

In this paper, the unsteady-state behaviour of a turbocharger wastegated turbine (IHI-RHF3) is investigated using both an experimental approach and a numerical approach. First, an experimental campaign is performed in a specialized test rig operating at the University of Genoa, for different openings of the wastegate valve and under steady flow and unsteady flow operations. An appropriate configuration of the turbine outlet circuit fitted with a separating wall is used to carry out instantaneous measurements downstream of the turbine wheel and the wastegate valve. The above data constitute the basis for the tuning and validation of a one-dimensional turbine model recently developed at the University of Naples. Preliminary model tuning is carried out on the basis of the characteristic map measured for a completely closed wastegate valve under steady flow operations. A refined one-dimensional schematization of the experimental apparatus is implemented within the commercial GT-Power® software, including the turbine, the wastegate circuit and the upstream and downstream measuring stations. In particular, the classical map-based approach is suitably corrected with a sequence of pipes that schematizes each component of the turbine (the inlet and outlet ducts, the volute and the wheel) to account for the wave propagation and storage phenomena inside the machine. A detailed one-dimensional schematization of the wastegate circuit is also implemented and independently tuned. The turbine model capability under unsteady flow conditions is tested for different wastegate openings and pulse frequencies, by applying time-dependent boundary conditions. In particular, the pressures and temperatures measured upstream and downstream are imposed at the model ends, and the instantaneous mass flow rate and the actual power are numerically evaluated. The results are compared with the experimental data, demonstrating good accuracy and showing some improvements with respect to the standard turbine modelling in the case of the mass flow rate prediction. On the contrary, the computed actual power shows some inaccuracies, especially at higher pulse frequencies.

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.

Experimental analysis of unsteady flow performance in an automotive turbocharger turbine fitted with a waste-gate valve

Downsizing and turbocharging is today an effective way of enhancing fuel economy in automotive engines. However, more information on compressor and turbine behaviour when working under unsteady flow conditions typically occurring in automotive turbocharged engines is still required to improve simulation models. The results of an experimental investigation into a small turbocharger turbine fitted with a waste-gate valve are presented in this paper. Turbine performance was measured under both steady and unsteady flow operation. Particular attention was given to pulsating flow performance, evaluated starting from the measurement of instantaneous parameters (inlet and outlet static pressure, mass flowrate, and turbocharger rotational speed). The effect of flow unsteadiness on turbine behaviour is analysed, referring to different pulse frequencies and waste-gate settings. The paper highlights that steady and unsteady turbine performance when the waste-gate valve is partially or totally open should be known in order to improve engine-turbocharger matching calculations.

Steady and pulsating flow efficiency of a waste-gated turbocharger radial flow turbine for automotive application

In the paper the results of an experimental investigation developed on a small turbocharger turbine for automotive application are presented, including the effect of the waste-gate valve opening. The study was focused on the evaluation of turbine efficiency, especially under unsteady flow conditions typically occurring in automotive turbocharged engines. Turbine efficiency values measured under steady and pulsating flow conditions are compared, also considering a quasi-steady flow approach.