Steady Engine Operation Research Articles

Experimental and modeling analysis on the optimization of combined VVT and EGR strategies in turbocharged direct-injection gasoline engines with VNT

The combination of a growing number of complex technologies in internal combustion engines (ICE) is commonplace, due to the need of complying with the tight pollutant regulations and achieving high efficiencies. Hence the work of calibration engineers is led by a constant increase in degrees of freedom in ICE design. In this research work, a wide analysis on the optimization of combined variable valve timing (VVT) and exhaust gases recirculation (EGR) strategies is developed, in order to reduce fuel consumption in a EURO 6 1.3l 4-stroke 4-cylinder, gasoline, turbocharged, direct-injection engine, also equipped with a variable nozzle turbine (VNT). For that purpose, a methodology which combines 1D engine simulations with limited experimental work was applied. First, the data from 25 experimental tests distributed into three steady engine operating conditions was used to calibrate a 1D model. Then, modeling parametric studies were performed to optimize VVT and EGR parameters. A total of 150 cases were simulated for each operating point, in which VVT settings and EGR rate were varied at iso-air mass flow and iso-intake manifold temperature. The optimization was based on finding the configuration of VVT and EGR systems which maximizes the indicated efficiency. All different cases modeled were also evaluated in terms of pumping and heat losses. Moreover, a deep assessment of instantaneous pressure traces and mass flows in intake and exhaust valves was given, to provide insights about the optimization procedure. Finally, the findings obtained by simulation were compared with the results from a design of experiments (DOE) composed of more than 300 tests, and the impact on engine fuel consumption was analyzed.

Cylinder-to-cylinder high-pressure exhaust gas recirculation dispersion effect on opacity and NOx emissions in a diesel automotive engine

The objective of the study is to determine the effect of the high-pressure exhaust gas recirculation dispersion in automotive diesel engines in NO x and smoke emissions in steady engine operation. The investigation quantifies the NO x and smoke emissions as a function of the dispersion of the high-pressure exhaust gas recirculation among cylinders. The experiments are performed on a test bench with a 1.6-L automotive diesel engine. In order to track the high-pressure exhaust gas recirculation dispersion in the intake pipes, a valves system to measure CO2, that is, exhaust gas recirculation rate, was installed pipe to pipe. In addition, a valves device to measure NO x emissions cylinder to cylinder in the exhaust was installed. Moreover, a smoke meter device was installed downstream the turbine, to measure the effect of the high-pressure exhaust gas recirculation dispersion on smoke emissions. Five different engine speeds were studied with different torque levels; thus, the engine map was widely studied, from 1250 to 3000 r/min and between 6 and 20 bar of brake mean effective pressure. The exhaust gas recirculation rate varies between 4% and 25% depending on the operating point. The methodology focused on experimental tools combining traditional measuring devices with a specific valves system, which offers accurate information about species concentration in both the intake and the exhaust manifolds. The study was performed at constant raw NO x emissions to observe the effect of the exhaust gas recirculation dispersion in the opacity and fuel consumption. The study concludes that when the exhaust gas recirculation dispersion is low, the opacity presents reduced values in all operating points. However, above a certain level of exhaust gas recirculation dispersion, the opacity increases dramatically with different slopes depending on the engine running condition. This study allows quantifying the exhaust gas recirculation dispersion threshold. In addition, the exhaust gas recirculation dispersion could contribute to increase the fuel consumption up to 3.5%.

An analysis of SCR reactor deactivation impact on NOx emissions from a compression ignition engine

Catalytic exhaust gas aftertreatment devices fitted to combustion engines are susceptible to partial deactivation as their operating time progresses. This includes selective catalytic reduction (SCR) reactors meant for NOx emission control. There are several known deactivation mechanisms of SCR reactors already analyzed in detail in the literature. This paper, however, approaches the analysis of reactor deactivation by comparison of exhaust gas characteristics over repeatable cycle for fresh and aged samples of a SCR reactor for non-road mobile machinery. The research aims to outline which parameters describing the SCR reactor’s performance are most affected by its ageing. In order to do that, fresh and aged samples of the reactor were tested under the Non Road Steady Cycle. The acquired emission results, including concentration traces of particular compounds were analyzed. The specific NOx emission of the aged reactor was significantly higher than that of the fresh one. The NOx conversion efficiency of both reactors was found similar at periods of steady engine operation. It was recognized that during transient conditions the NOx conversion efficiency of the aged reactor was decreased. It was found that the main factor contributing to that phenomenon is the drop in the ammonia storage capacity of the aged SCR sample.

Influence of a low pressure EGR loop on a gasoline turbocharged direct injection engine

This paper presents an experimental study of a low pressure EGR loop on a spark ignition (SI) Gasoline Turbocharged Direct Injection (GTDI) engine that will improve the understanding on the advantages and disadvantages of this strategy. Two steady engine operating conditions were investigated, 10 bar and 17 bar at 2000 rpm. At partial load conditions a combustion, performance, air management and exhaust gas emissions study was performed in order to analyses the EGR effect on the GTDI engine. The main advantages found were the reduction in fuel consumption due to the better combustion phasing, and the reduction in pumping losses and heat losses through the cylinder walls. A reduction on NOx, CO and soot was also observed when introducing EGR at these operating conditions. The main disadvantage found was the water condensation after the intercooler. At high load conditions similar analysis and conclusions to the partial load conditions are obtained. The EGR also allowed the combustion to be phased in a more efficient angle by reducing the risk of knocking, which helped reduce the exhaust gas temperature, despite the elimination of the fuel enrichment strategy. A reduction on CO and soot raw emissions was also observed when introducing EGR, as observed at partial load conditions, but a high reduction in NOx, CO, HC and soot emissions was observed after the catalyst since the fuel enrichment strategy is eliminated when cooled EGR is introduced. The main disadvantage found was the turbocharger limitation since higher compression ratio is required in order to keep the same air mass flow as the reference conditions without EGR. The original turbocharger is not designed to provide this higher compression ratio at low engine speed and high load. Results confirm how introducing EGR is a suitable strategy to control knocking and reduce simultaneously exhaust gas temperature and fuel consumption, but the disadvantages found in this investigation must be solved to assure its feasibility as a powerful technology to be implemented in future SI engines.

Nanoparticle Filtration Characteristics of Advanced Metal Foam Media for a Spark Ignition Direct Injection Engine in Steady Engine Operating Conditions and Vehicle Test Modes

In this study, the particle formation and reduction characteristics at the engine-out position, after a three-way catalyst (TWC) and a metal foam gasoline particulate filter (GPF), were evaluated for a gasoline direct-injection (GDI) engine under part-load operating conditions. The vehicle tests were performed under the Federal Test Procedure-75 (FTP-75) and the Highway Fuel Economy Test (HWFET) modes. Particle number (PN) concentrations, size distributions, and the filtering efficiency with the GPF were evaluated with a condensation particle counter (CPC) and a differential mobility spectrometer (DMS500). Under steady engine operating conditions, the PN concentrations at the engine-out position were 9.7 × 105–2.5 × 106 N/cc. While, the PN concentrations after the GPF were 9.2 × 104–3.5 × 105 N/cc, and the PN was reduced by 77%–96%. The PN filtering efficiency with the GPF-GDI vehicle reached approximately 58% in the FTP-75 and 62% in the HWFET mode. The PN concentration of the GPF-GDI vehicle was significantly reduced to 3.95 × 1011 N/km for the FTP-75 and 8.86 × 1010 N/km for the HWFET mode. The amount of nucleation mode particles below 23 nm was substantially reduced with the GPF-GDI vehicle. The fuel economy, CO2, and regulated emissions of the GPF-GDI vehicle were equivalent to those of the base GDI vehicle under the vehicle certification modes.

Diagnosing marine turbine engines through energy characteristics of their flow sections

The aim of the performed research was to develop of a diagnostic method of the flow section of a marine turbine combustion engine based on the level of delamination of its energy characteristics. The here adopted diagnostic model provides for a formulation of the evaluation of the technical conditions based on the measurements of the parameters of the thermodynamic medium in the characteristic control cross-sections of the flow section of the engine during a steady engine operation at nominal load. Based on the energy balancing of the individual impeller sets calculations were performed of their parameters in the form of a distribution of the stream of enthalpy along the flow section. This constituted the basis for the diagnostic conclusions on the overall technical condition of the engine at the same time enabling the identification of the spots of greatest energy losses.

Study on Steady Condition Control of Hybrid Turbocharging System

This paper analyzes the principle of hybrid turbocharging system in a vehicle diesel engine, and proposes motor control model about hybrid turbocharging system in steady engine operation condition according to energy imbalance of the exhaust gas. The high-speed motor can work as a motor or a generator in this control model of different engine condition. Then mapping algorithms about n-dimensional linear interpolation and BP neural network are presented to solve steady condition control problem of the hybrid turbocharging system. Each algorithm is applied to map same sample data, the simulation results reveal that BP neural network mapping algorithm is more suitable for the mapping control of hybrid turbocharging system because BP neural network has better generalization ability and faster processing speed.

Light scattering technique for estimating soot mass loading in diesel particulate filters

The real-time estimation of soot mass loading on diesel particulate filters (DPF) is essential to assure perfect and fuel efficient regeneration. Computer models based on the pressure drop across the DPF are usually installed in the engine control unit to estimate the soot mass loading during vehicle driving, but this approach is still subject to uncertainty about the lack of resources available. The aim of this study is to develop a portable instrument that can make real-time measurements of soot mass loading under transient mode for calibrating the models. The instrument is based on the light scattering technique: A laser beam illuminates diesel particles in a small exhaust sample and the intensity of scattered light from soot particles is reduced to soot mass concentration using calibration data obtained under steady engine operating conditions. It is demonstrated that the prototype instrument can measure the temporal variations of cumulative soot mass and filtration efficiency of a diesel particulate filter under a transient mode, and that it has a minimum detectable concentration of 5 μg/m3, which is low enough to detect the particle breakthrough in the DPF. The proposed technique has potential to be applied for on-board diagnostics if the device is downsized.

Order tracking of diesel engines with a Kalman filter

Order tracking analysis is one of the techniques used to monitor the performance of diesel engines. The objectives are to separate vibration into terms corresponding to the rotational speed and its multiples and then to monitor the changes over the revolution of a crankshaft. A Kalman filter provides the technique of isolating each of the components that are synchronous to the shaft rotation. By filtering the signal in the time domain it has also the capabilities to follow any variation of the rotational speed. Thus, the Kalman filter, if properly designed, can provide a tool for testing not only steady engine operation but can also be used to analyze both the engine acceleration and declarations under different loads. The paper discusses first, the process of monitor the frequency components locked up to the rotational speed with high resolution. Then, it shows how to reconstruct the synchronous components, in terms of amplitude and phase, to produce the vibration patter over the crankshaft revolution.

A Numerical Study of Fuel Evaporation and Transportation in the Intake Manifold of a Port-Injected Spark-Ignition Engine

The paper presents a computer simulation of mixture preparation in the inlet port of a port-injected spark-ignition engine operating at low load and low speed. The solution of the models at successive crank angles allows mixture preparation in the port to be investigated under steady engine operation. The main features of the simulation are: monosize spray of a single-component fuel, evaporation of the spray droplets during flight, evaporation of the fuel film, fuel film flow along the manifold walls and unsteady air flow during the induction period. Use of the simulation allowed investigation of the effects of: manifold wall and air temperatures, spray-droplet size, injection timing, injector aim, fuel voltatility and the use of methanol as the fuel.